Improved urea synthesis method

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for synthesis of urea from ammonia and carbon dioxide at high pressure and temperature with formation of ammonium carbamate as an intermediate product. The method includes a high pressure synthesis section comprising at least one step for separating unreacted ammonium carbamate from ammonia via stripping decomposition, carried out in a vertical apparatus which is a stripping column. Said step also involves feeding a CO2 stream, heated to temperature 130-230C, into the bottom part of said stripping column, in amount of 1-15 wt % with respect to total weight of fresh CO2, containing a passivating agent, fed into the process. The amount of this agent is such that its equivalent O2 content in moles ranges from 0.05 to 0.8% with respect to the number of moles of CO2 in said stream. Fresh CO2 is compressed in a multiple-stage compressor having intermediate heat-exchange stages. Apparatus for realising the improved urea synthesis method is also provided. The invention enables to optimise the urea synthesis process.

EFFECT: invention enables to optimise the urea synthesis process.

21 cl, 3 dwg, 3 ex

 

The present invention relates to an improved method for the synthesis of urea.

In particular, in the art there are several ways to obtain urea.

The synthesis of urea is carried out by reaction of ammonia and carbon dioxide at high pressure and temperature, followed by separation of urea from a mixture containing unreacted products, and returning them to the reactor.

Thus, the industrial method of obtaining urea based on direct synthesis in accordance with the following reaction:

This synthesis proceeds in two separate stages:

In the first phase (1a) is an exothermic equilibrium reaction, the velocity at room temperature is high, however, in order to achieve the required equilibrium state at high temperature stage (1B), the required high pressure.

In the second stage (1B) is an endothermic reaction, which achieves significant speed only at high temperatures (>150C), and when reaching the equilibrium state and at a temperature of 185C, starting from the mixture of the reactants in stoichiometric proportions, leads to the degree of conversion of CO2slightly above 50%. This is not high enough degree of conversion mn is a significant increase, increasing the ratio of NH3/CO2.

Two of the stages outlined above usually are not in separate zones of the reactor, and simultaneously in the reaction mixture, which therefore contains urea, water, ammonia, carbon dioxide and ammonium carbamate; the relative concentrations of these components in different points of the reactor depend on various thermodynamic and kinetic factors play a role in the process.

Methods of obtaining urea by direct synthesis from ammonia and carbon dioxide are well described in the literature relating to this area. Great overview of the most common ways to obtain urea can be found, for example, in "Encyclopedia of chemical technology" ("Encyclopedia of Chemical Technology", Ed.Kirk-Othmer, "Wiley Interscience", third Ed. (1983), vol.23, p.548-575).

When using industrial methods for producing urea usually spend the synthesis reactor, which serves NH3, CO2and aqueous solutions of ammonium carbamate and/or carbamates, coming from recycled threads unreacted reactants, at temperatures in the range from 150 to 215C, pressure at least to 13.2 MPa (130 ATM), a molar ratio of NH3/CO2in the interval from 2.5 to 5, calculated on the amount fed streams, including ammonia and CO2in the form of carbamate/carbonate of ammonium. In addition to the formed water and the excess is fed NH 3coming out of the reactor, the product still contains a significant amount of CO2mainly in the form of unreacted ammonium carbamate.

Important for optimal degrees of transformation aspect is the control of the temperature level in the reactor, because of too low temperature, too high and lead to the reduction of the degree of conversion due to multidirectional action of various chemical and thermodynamic factors.

The separation of urea from water and unreacted reagents is carried out in several sections operating at decreasing temperatures and pressures; in these sections carry out the decomposition of ammonium carbamate to the NH3and CO2which then can be recycled to the reactor. The presence of the section offices and recirculatory carbamate requires additional costs, which negatively affects the value of the final product.

Known processes which proceed in accordance with the above General scheme, described, for example, in U.S. patents 4092358, 4208347, 4801745 and 4354040.

In particular, the urea contained in the aqueous solution leaving the reactor, separated from the greater part of the unreacted ammonium carbamate and excess ammonia used in the synthesis, in suitable decomposers or Stripping columns, which operates under a pressure which, essentially equal to or slightly lower than the pressure in the synthesis.

The decomposition of ammonium carbamate is carried out in the decomposers by heating from the outside via indirect heat exchange with a warmer fluid medium, usually with steam at 1.8 to 3.0 MPa, possibly with distillation of the products of decomposition of inert gases, or ammonia, or carbon dioxide, or mixtures of inert gases with ammonia and/or carbon dioxide, and the distillation may be performed with excess of ammonia dissolved in the urea solution (smoothee") - i.e. without a separate filing eye agent.

The decomposition of the carbamate, along with possible eye agents and except for inert ingredients, usually condense in refrigerators, you get a liquid that is recycled back into the reactor for synthesis.

Additional documents that can be specified as references, presents US patents 4314077, GB 1184004, GB 1292515, US 3984469, US 4137262, DE 2116267, FR 2489323. In these patents described processes for the production of urea, the characteristics of which are set out above.

The most difficult stages in the synthesis process of urea are those in which the ammonium carbamate is present at the highest temperature and the highest concentration, and therefore, in the above-mentioned processes these stages coincide with the stages of decomposition-Otho the key and condensation of ammonium carbamate.

One of the problems that need to be addressed at these stages, is associated with corrosion of the equipment used because of the exceptionally aggressive characteristics of the environment inside the equipment due to the presence of highly concentrated salt solutions, and because of the phenomena caused by mechanical stress on the surface in the areas of decomposition and release the gaseous phase.

To overcome these disadvantages in the prior art proposed, for example, be used in the manufacture of Stripping columns, special materials, in particular Ti, Zr, special stainless steel carbamide class or a combination of both. In accordance with the prior art it is helpful to apply a certain amount of air or other passivating agents to extend the period of stability of these materials to corrosion, especially in the case of stainless steel, favoring the formation of a stable oxide layer on the surface in contact with the working fluid environments.

In particular, the invention can be implemented on units of a certain type for the synthesis of urea by distillation of the ammonia, i.e. those installations where the stage distillation is carried out in the Stripping column, in which the stage of decomposition of the carbamate of the ammonia present in the solution for the synthesis and/or is supplied for this purpose.

Currently, installations of this type in the cube Stripping columns add a certain amount of air to achieve the passivation Stripping columns, made of stainless steel. This addition is carried out by appropriate injection of air by means of compressors, designed exclusively for this purpose. In other parts of the circuit synthesis of urea under high pressure, requiring passivation, the latter also carried out using air, which is added at the inlet to compressor CO2and sent to the reactor for the synthesis of urea by the compressor. The air, which was not involved in the reaction, the passivation of the reactor, out of the reactor together with the reaction mixture, and it is sent to the upper part of the Stripping column, from which it passes into the fridge for carbamate, and from thence to the separator carbamate, and then leaves the circuit synthesis using a valve designed to control pressure in the circuit.

During this journey the air provides passivation of the surfaces of the equipment with which it comes into contact and which otherwise would be subject to corrosion processes.

Given the above, i.e. the fact that the air for the passivation direct from the reactor in the upper part of the Stripping column, a cube Stripping columns excluding the Chan of the passivation process, produce the specified air, which is added at the inlet of the compressor for CO2and sent to the reactor by means of the compressor.

For this reason, in the prior art indicate the need to conduct the appropriate introduction of air through the compressor, designed exclusively for this purpose.

However, this solution requires additional special devices, that is, these compressors, which, in addition to costs, they require periodic maintenance.

As mentioned above, an additional aspect that should be taken into account in the case of these plants, due to the fact that heat, and, more generally, the temperature level in the reactor at the stage of filing and the reaction of ammonia and carbon dioxide to form a liquid mixture containing ammonium carbamate, water, ammonia and urea, is controlled by changing the temperature level flow CO2and/or ammonia fed to the reactor, and/or based on the distribution of these same filed flows between the Stripping column, a refrigerator and a reactor, and/or by changing the amount of heat removed in the refrigerator. This control of the temperature level is an additional essential aspect to obtain the optimum degree of conversion in the reactor, as too low, too high temperature led to a decrease in the degree of conversion due to multidirectional action of various chemical and thermodynamic factors.

The applicants have proposed a method that does not have the above described disadvantages inherent in the prior art, and additionally optimizes the synthesis of urea.

Accordingly, the present invention is an improved method for the synthesis of urea from ammonia and carbon dioxide at high pressure and temperature with the formation of ammonium carbamate as an intermediate product including the sections of the synthesis at high pressure, comprising at least one stage of separation by decomposition-Stripping with ammonia, unreacted ammonium carbamate, held in a vertical apparatus, commonly called a Stripping column, characterized by the fact that this stage also includes flow CO2at the bottom of the said Stripping column, heated to a temperature in the range from 130 to 230C, preferably from 150 to 210C, in an amount of from 1 to 15%, preferably from 3 to 12% wt. with respect to the total mass of fresh CO2fed to the process containing passivating agent in such a quantity that it is equivalent to the content of O2in moles is in the range from 0.05 to 0.8%, preferably from 0.1 to 0.4% relative to the number of moles of CO2in the specified stream.

In the present description, the term "heated, heated with respect to the flow means that the tempo is the atur specified flow increased and its temperature is higher than the flow temperature CO2on the final compressor outlet.

More preferably, the heated stream of CO2fed to the Stripping column had a temperature in the range from 160 to 200C.

In accordance with the present invention fresh CO2not supplied to the Stripping column is preferably directed into the reactor, but it can also be distributed between the reactor and the other stages of the process, such as a refrigerator and one or more stages of separation in the middle and low pressure.

Preferably, the amount specified flow of heated CO2fed to the Stripping column, ranged from 4 to 15%, more preferably from 4 to 12% by weight relative to the total mass of fresh CO2fed to the reactor.

The flow of compressed CO2fed to the reactor has a temperature in the range from 100 to 200C, preferably from 130 to 185C.

You can heat the entire compressed CO2and it is possible to heat only the flow of CO2fed to the Stripping column.

Preferably fed to the Stripping column flow CO2was heated at one or more intermediate stages of compression CO2.

The flow of compressed CO2fed to the reactor at one or more intermediate stages of compression CO2during the feed to the reactor may consist of a mixture of compressed CO2 and one or more streams of heated CO2accordingly, in suitable proportions, and even more preferably at least at an intermediate stage of compression at the highest temperature from the combination of the flow of compressed CO2and the flow of heated CO2in suitable proportions.

In accordance with a specific embodiment of the present invention, the flow of CO2directed into the reactor and having a temperature of from 130 to 185C., is 0-40 wt.%. in relation to the total weight of the specified stream of compressed CO2coming out of the reactor at a temperature of from 100 to 120C, and 60-100% wt. in relation to the total weight of the specified stream from a stream of CO2heated at one or more intermediate stages of heat transfer from the compressor to a temperature of from 140 to 200C.

In accordance with another preferred embodiment of the present invention the flow of fresh CO2fed to the Stripping column, on 4-12% wt. representing the CO2directed into the reactor, heated to a temperature of from 160 to 200C at one or more intermediate stages of heat transfer in compressor for CO2.

The heated stream of CO2heat up during the feed to the reactor at one or more intermediate stages of compression CO2on the outer side or in the tube space.

Stage of decomposition-Stripping the carb is Mata ammonium ammonia preferably is a stage smoothely.

Passivating agent, as a rule, is an oxidizer, which is preferably selected from air, oxygen enriched air, hydrogen peroxide and mixtures thereof, preferably air.

The term "equivalent content of O2" in the same sense as it is used here in the description pestiviruses agent, indicates the number of moles of O2that would also be used instead of pestiviruses agent to obtain the same degree of conversion in the oxidation-reduction reactions. This corresponds to the number of moles of O2in the case of air or oxygen, half of the number of moles of H2O2and 3/2 of the number of moles of ozone.

Proposed in the present invention, the method preferably includes a step of synthesis of urea, where the molar ratio of ammonia/carbon dioxide is in the range from 2.7 to 5.0, more preferably from 3.0 to 4.0.

The fundamental advantage of the improved method is that it allows the simultaneous optimization of the technological characteristics of the reactor and Stripping columns.

Taking into account the fact that the temperature control of the reactor is fundamental for the optimization of transformation and that the flow of CO2in a special way heated for optimum conversion in the reactor, in fact, should also porn is th this excessive heating leads to a decrease in the degree of conversion. Therefore, control of the temperature can also easily be done by filing a specific part of the flow of heated CO2in the Stripping column, and the result at the same time optimized technological characteristics of the reactor and Stripping columns.

Under the direction of a certain part of the flow of heated CO2in the Stripping column while increasing the temperature of the stream of compressed CO2directed into the reactor, to balance the reduction of its quantity, at the same time there are very positive effects: the reactor operates at the optimum temperature that maximizes the degree of transformation, while at the passivation due to pestiviruses agent, in particular air, is present in the flow of heated CO2prevents corrosion cube Stripping columns. This solution also leads to the compensation of heat, allowing for the growth of enthalpy, and this gives added value of the proposed process. In addition, the reactor can operate at the optimum temperature, heating the feed flow of ammonia.

An additional advantage offered by this method is to exclude compressor for feeding pestiviruses Vozduha cube Stripping columns and require additional costs and periodic maintenance.

The proposed method also has the advantage that it surprisingly quickly can be implemented by introducing a few simple modifications to existing traditional installation, provided that it has a section distillation under high pressure. In particular, it is enough to modify the installation so that was the opportunity to serve in the specified section of the distillation stream is heated CO2between the compressor for CO2and the reactor.

An additional advantage is the possibility of using steam strippers from any resistant to urea steel material. Here the method further illustrated in the attached drawings, on which:

Figure 1 schematically presents the implementation stages of compression and pre-heat flow CO2;

Figure 2 schematically represents the implementation of the reaction and decomposition-Stripping (path synthesis) process for the synthesis of urea, which is a preferred implementation of the present invention;

Figure 3 schematically represents the implementation of the reaction and decomposition-Stripping (path synthesis) process for the synthesis of urea, which is a variant of implementation of the characteristic of the current level of technology.

In all these drawings are not shown structural details, such as us, the son, valves and other equipment, do not seem important for a full understanding schematically reflected processes. In any case, you should not assume that the proposed method is limited to only what is shown and described on the attached drawings which are given only for illustrative purposes.

In the proposed method, where the reactor operates with an excess of ammonia relative to the stoichiometric quantity of carbon dioxide required to obtain ammonium carbamate, and then urea, the stream exiting the reactor, and in the General case, the main part of the liquid streams generated in the process, usually contains an excess of ammonia. In the present description has been directed to the composition of these liquid streams and mixtures (two-phase), while it is usually assumed that all carbon dioxide is present in the form of ammonium carbamate, and the remaining excess of ammonia is present in the form of free ammonia or ammonia.

Moreover, to simplify the present description, the term "liquid" is used to denote flows of mixtures consisting of a single liquid phase or mixed phase vapor-liquid. Conversely, the term "gas" is used for flows of mixtures in which the liquid phase is essentially absent.

In the diagram shown in figure 1, you can see the successive stages of compression (compression ratio) C1, C2, C3 and C4, as well as those whom laboniki SC1, SC2, SC3, SC4 and sc5 pack. Stage compression C1, to which the power line 1 by line 2 is connected with the first heat exchanger SC1, with the highest temperature, where the compressed CO2line 9d is heated and sent to the output line 3, which is directly related to the Stripping column S1 through line 3b (15b figure 2). Coming from line 2 CO2cool, and it comes from SC1 on line 4, which is associated with the second stage of compression C2 after passing through the heat exchanger SC2 (which serves for cooling water). CO2emerging from the stage of compression, C2, serves on line 5 to heat exchanger SC3, from which it exits through line 6 to the feed stage compression C3 after getting into the heat exchanger SC4 (which serves for cooling water). Cooling CO2served on the other side of the heat exchanger SC3 on line 9b, it goes on line 7, and it can be directed into the heat exchanger SC1 along the lines 7b and 9d and the reactor through line 7a, which is connected to line 3A, and then line 9a (which corresponds to line 15a figure 2). Line 3 is also connected to line 3A, which comes from the heat exchanger SC1 for possible separation between the reactor and Stripping column CO2with the maximum temperature.

Stage compression C3 next, after passing through the heat exchanger sc5 pack (which serves for cooling water) through line 8 is connected with the stage of the compression C4, which is cared, includes the output line 9, which directly connects it to the heat exchanger SC3 through line 9b and the reactor R1 via line (15a figure 2). Stage C4 can also be directly connected to the heat exchanger SC1 sequentially on lines 9, 9c and 9d.

Connecting lines schematically reflected in figure 1, allow by means of regulating valves, indicated by the symbol of the butterfly, to receive streams of different compositions with respect to CO2fed to the reactor and Stripping column, in the sense of temperature, and flow rate selected in accordance with the present invention. In the embodiment of the present invention some of the lines shown in figure 1, if necessary, and can not be used.

In the diagram Figure 2 shows the reactor R1, which through overflow pipe T and the line 10 is connected to a Stripping column S1. Last through line 11 is connected with the section P of the isolation and purification of urea, from which the line 12 carbamate return in the capacitor CC1 and receive urea on line 20 in its pure form, solid or in aqueous solution. The exit gases from the Stripping column S1 is connected with the capacitor CC1 through line 13, which is then connected to the separator.

Installation of compression and heating of the carbon dioxide associated with the reactor (line 15A) and cube Stripping columns (line 15b). Line 16A is a supply line is of Miaka in the reactor, it consists of a line 16 to the fresh and recovered ammonia and line 17 of the recycle carbamate leaving the separator V. In the head part of the separator V provided by the output line 18 to eject inert products and to control the pressure.

Reflected in figure 3 scheme essentially plays the same elements with the same purpose as in figure 2. However, this scheme refers to the traditional method of producing urea. Significant difference compared to Figure 2 is the lack of a line 15b at full supply of fresh CO2into the reactor through line 15 leading from the compression system With, and in the presence of the compressor 19, which is intended to supply pestiviruses air Stripping columns in the cube S1.

The proposed method can be carried out in case of installation with the above characteristics, equipped with a section for synthesis, including equipment and connections already described in connection with the description of the scheme presented in figure 2. The installation itself can be created by building it anew, or it can very conveniently be created by modifying an existing installation for the synthesis of urea, equipped with a Stripping column, which can operate in conditions smoothely, through the introduction of a line between the compressor CO2and the lower part of the specified Stripping columns, which on the OK CO 2to submit to the Stripping column in an amount of from 1 to 15%, preferably from 4 to 12 wt.%. with respect to the total mass of fresh CO2supplied in the installation.

Thus, with reference to figure 1 and figure 2 describes the various possible embodiments of the proposed method, however, the present description does not limit the General scope of the invention itself.

The flow of fresh CO2served in the installation of compression and heating, as detailed in figure 1.

This plant, which is a compressor for feeding into the reactor, consists of a number of stages of compression (usually four) with increasing pressure, and between them there is the same number of stages of heat to control the temperature of CO2. Pressure achieved at different stages of compression depend on the design and performance of compressors and usually well-known specialists in this field of technology. Ways embodiment the intermediate stages of heat exchange in combination with the stages of compression are also well known.

In accordance with the private option for the entire flow of compressed CO2through the four stages of compression C1, C2, C3 and C4 on the lines 2, 4, 5, 6, and 8 are sent on lines 9 and 9b of the heat exchanger SC3. It is understood that in the heat exchanger SC3 stream CO2on the output line 7, which is optionally heated, cha is in part directed along lines 7b in line 9d, which feeds the heat exchanger SC1, and then to the Stripping column S1 through lines 3 and 3b and for the most part on line 7a it is passed in line 3a, and from there sent on lines 9a directly into the reactor R1.

Alternatively, it is also possible to direct the entire flow of compressed CO2coming from the heat exchanger SC3, in the heat exchanger SC1 on lines 7, 7b and 9d, where after further heating the partially directed through line 3 to the Stripping column S1, and for the most part - in the reactor R1 along the lines 3a and 9a.

In accordance with another alternative, the flow of compressed CO2after passing through the four stages of compression C1, C2, C3 and C4 on the lines 2, 4, 5, 6, and 8 partially directed along lines 9 and 9a directly into the reactor R1, and partly along the line 9b - exchanger SC3. At the outlet of the heat exchanger SC3 stream CO2additionally heated, can follow one of the paths described in the previous paragraphs.

In accordance with another alternative stream of compressed CO2at the exit from the stage C4 on line 9 partially sent directly to the heat exchanger SC3 along lines 9c and 9d, and from there to the Stripping column lines 3 and 3b, and for the most part - in the heat exchanger SC3 and then into the reactor R1 in lines 7, 7a, 3a and 9a.

In accordance with the scheme presented in figure 2, the fresh and regenerated ammonia, compressed and supplied through the line 16, are referred to as the displacing fluid in ejector and mixed there with restoring and recirculated flow (line 17), ammonia, carbamate and water coming from the separator V, and includes a condensate obtained in CC1, and the regenerated product coming from the partition P. the Resulting stream is directed through line 16a to the reactor R1.

Alternatively, and in accordance with the requirements of part ammonia can be sent to the Stripping column S1 (line 16b).

Under normal operating conditions of the process according to the invention, these streams contain mainly ammonia in the liquid state.

Fresh CO2containing passivating agent, which can represent, for example, air, lines 15a and 15b is sent to the reactor R1 and the Stripping column S1, respectively.

A large part of the fresh carbon dioxide after the compression are sent directly to the reactor (>85%)and partly in the Stripping column S1, as already explained in detail with reference to Figure 1.

The total power of the reactor consists of threads 15a and 16a, which, in turn, fed from the recycle line 17.

Coming from reactor R1 through overflow pipe T and line 10 liquid stream containing urea, water, ammonia, ammonium carbamate and the air is sent to the Stripping column S1.

The regenerated stream coming from the partition P and containing water, ammonia and ammonium carbamate, is sent to the capacitor CC1 line 12.

Gaseous stream 13 that is extracted is from the head of the Stripping column S1, containing NH3, CO2and water, recycle in the fridge CC1. There it condenses at a pressure approximately equal to or slightly lower than the pressure in the reactor, and at the highest possible temperature, preferably above 140C, more preferably from 150 to 180C, to form a liquid stream containing mainly ammonium carbamate and ammonia and a small amount of water and possibly urea. The latter is formed during the stage of condensation, where working conditions are already favorable partial shift already described chemical equilibrium (1b) to the right. Thus obtained liquid stream is fed into the separator V on line 14. A gaseous stream comprising inert gases and possibly the remains of the oxygen along with small quantities of ammonia, CO3and H2O, poured from the head portion of the separator V on line 18.

Thread 11 coming from the cube Stripping columns S1 and containing all the urea, direct (line 11) at the subsequent stage of purification and concentration, which is shown schematically together in the partition P in figure 2. The already mentioned thread NH3, carbamate and recovered water (stream 12) comes from this point, and pure urea and water extract on lines 20 and 21, respectively.

Here an improved method for the synthesis of urea from ammonia and carbon dioxide can is about to use, for example, in the synthesis process comprising the following stages:

(a) the supply of ammonia and carbon dioxide and their interaction in at least one reactor at a molar ratio of NH3/CO2where ammonia is considered as such or in the form of ammonium carbamate, in the range from 2.7 to 5, preferably from 3.0 to 4.0, with the formation of the first liquid mixture containing ammonium carbamate, water, ammonia and urea;

(b) the transfer of the specified first liquid mixture to the stage of decomposition-Stripping;

(C) heating the first liquid mixture at the specified stage of decomposition-Stripping essentially at the same pressure, as specified in the reactor in order to achieve decomposition of part of the ammonium carbamate into ammonia and carbon dioxide with simultaneous distillation of ammonia specified liquid mixture with the formation of the first gaseous mixture containing ammonia, carbon dioxide and water, and the second liquid mixture containing urea, water, ammonia and undecomposed portion of the ammonium carbamate in the cube Stripping tower also serves the flow of heated CO2containing passivating agent;

(g) the transfer, if possible by means of the ejector, the specified first gaseous mixture to the stage condensing, operating essentially at the same pressure as the reactor, and the condensation of the mixture with the formation of a third liquid mixture containing carbamasepine and ammonia, refer to the separator;

(d) allocation of urea contained in the specified second liquid mixture, in one or more successive stages of decomposition and separation with the formation of essentially pure urea fourth liquid mixture containing water, ammonia and ammonium carbamate, and possibly the fifth stream containing essentially ammonia, and found a fourth liquid mixture formed in stage (d), are sent to the specified stage of condensation.

This method of synthesis is usually applied in a continuous manner on a suitable installation, pure ammonia and carbon dioxide are continuously fed into the system in order to reimburse the appropriate amount of reagents, transformed into urea and deleted on exit from the last section of the separation and pilirani" (granulation) of the product.

Fresh ammonia can be fed directly into the reactor, or it can be directed - in whole or in part - as organoclay fluid medium in the Stripping column and/or can be placed directly in the refrigerator.

The compressed ammonia is directed into the reactor typically has a temperature in the range from 0 to 130C, preferably from 30 to 100C. the higher temperature stream of ammonia may be preferred in that case, if in the Stripping column serves fresh CO2in the amount of from 8 to 15% of its total number, that is to maintain the reactor in a satisfactory temperature conditions.

The reactor for the synthesis of normally operates at temperatures from 150 to 215C, preferably from 160 to 195C, and at pressures from 8.9 MPa to 20 MPa, preferably from 11 MPa to 18 MPa, while the molar ratio of ammonia/carbon dioxide is in the range from 2.7 to 5.0, more preferably between 3,0 and 4,0.

Bringing the temperature in the reactor to the required size can be made according to any known in the art methods, for example, in addition to the said heated feed stream of ammonia, supply reactor terminographical element or by direction of the gases emerging from the Stripping column, directly in the reactor.

The reactor is usually provided with several plates of the type selected from known in the art, therefore, to provide optimal conditions for flow ideal displacement, it is also possible in the presence of two-phase systems.

The reactor may also include various reaction zones, appropriately interrelated with each other, possibly with different feed streams.

The reactor must have a liquid filling of this type, to provide a residence time of fluid from several minutes to several tens minutes, the ammonium carbamate formed by the reaction of ammonia with carbon dioxide at the stage of condensate and/or in the reactor, managed to degidrirovaniya to urea.

The stage of decomposition of the distillation is usually carried out in a heated Stripping column, usually using indirect heating with steam at high pressure. The temperature in the Stripping column is typically in the range from 160 to 220C, preferably 190 to 210C, and the pressure in it is the same or slightly lower than the pressure in the reactor.

Under the above conditions, the ammonium carbamate is prone to rapid decomposition, thereby forming ammonia and carbon dioxide, whereas urea, already formed in the reactor, remains essentially unchanged. The Stripping is done using ammonia as the carrier gas. In a preferred embodiment of the present invention the stage of decomposition of the distillation is conducted using as the carrier gas, the same ammonia, which is found in abundance in the stream exiting the reactor. Additional details of this preferred technology can be found, for example, in U.S. patent 3 876 696 (SNAMPROGETTI), the content of which is incorporated into this description by reference. This latest technology is called "smoothee".

Stage of decomposition is usually carried out in a device with beam vertically oriented pipe with falling liquid films. Coming out of the reactor, the mixture is preferably serves in the head part of the equipment, and it forms plank is, which is distributed down the walls of the tube bundle. In the proposed method it is also possible to use other known equipment suitable for this purpose.

Stage condensation is usually carried out in suitable refrigerators, for example in refrigerators with the beam pipe or surface refrigerators, in which the heat of condensation is used to heat other fluid. The heat of condensation is preferably used to produce steam, but it also can be used to supply heat to one of the subsequent stages of the decomposition of ammonium carbamate with an average or low pressure.

Stage condensation can be conducted under normal conditions (temperature, pressure, composition), such as in the known processes, provided that during the latter prevents the formation of solid ammonium carbamate in the refrigerator and/or lines coming out of it.

The separation of urea from ammonia and ammonium carbamate still present in the liquid stream leaving stage of decomposition sublimation is carried out in consecutive sections of decomposition and separation operating at average (from 1.1 MPa to 2.5 MPa) and/or low (0.2 to 0.8 MPa) pressure. This phase separation can be performed using one of the methods described in the literature, which have the ability to get recycled W is DCI stream, containing an aqueous solution of ammonium carbamate and ammonia, and possibly also a stream essentially consisting of ammonia. Appropriate sections of the separation and purification are, for example, such as is schematically presented in figure 1-5 of publication in the already mentioned "Encyclopedia of chemical technology" ("Encyclopedia of Chemical technology").

Separated thus from ammonium carbamate urea are usually obtained in the form of aqueous solution, which is subjected to final dehydration under vacuum (0.001 MPa) and obtain, firstly, the water, and secondly essentially pure urea, which is sent on the normal processes of pilirani" etc.

The stage of separation and purification of urea also included the final stage of dehydration stage treatment of waste water leaving the installation for synthesis.

Various liquid or two-phase streams containing ammonium carbamate coming from different subsections stage of separation and purification (decomposition of the carbamate at medium and low pressure, recondense carbamate, dehydratase urea, waste water)will be collected in a single recirculated stream and sent to a specified stage of condensation.

In accordance with certain variants of the implementation of the separation and purification of urea, in any case included in the scope of the present invention, the recycled AMIA and carbon dioxide may be present in the form of carbonate, bicarbonate and ammonium carbamate or a mixture thereof depending on the temperature and pressure of the mixture.

Below for illustration purposes and advantages of the present invention presents a number of practical examples, which in no way limit the scope of the claims.

The following examples illustrate the compositions of the various streams on the main components of the urea, ammonia, carbon dioxide and water, regardless of the fact that carbon dioxide in the ammonia liquid flows essentially in the form of ammonium carbamate. Air and inert products without their discernment designated as "air", as the consumption of oxygen in the working conditions of the synthesis loop are almost negligible.

Example 1

Was carried out a synthesis process of urea in accordance with this invention by a method where a stream of CO2containing a suitable amount of air flowing from the node With compression and heat was applied to the cube Stripping columns S1. More Stripping columns in the cube did not enter separately additional quantity of air or other pestiviruses agent. The link given by the schema shown in figure 1 and 2.

In the reactor R1 was applied the following components:

663 kg/h CO2and 5 kg/h of air from line 15a;

470 kg/h CO2, 650 kg/h NH3and 300 kg/h of water, in the form of a solution of carbamate am one line 17;

717 kg/h of fresh NH3with line 16.

The reactor operates at 15.9 MPa and 188C and refrigerator CC1 - when to 15.4 MPa and about 155C.

Water flow 12-enriched carbamate, consisting in particular of:

H2O=202 kg/h

CO2=172 kg/h

NH3=380 kg/h

extracted from partition P purification and concentration, or flow after Stripping columns S1, and after the connection with the thread 13 coming from the Stripping columns S1, directed along the line 12 in the fridge CC1.

Gaseous stream 18 consisting of H2O=2 kg/h CO2=2 kg/h, NH3=50 kg/h, air=5.5 kg/h, was separated in the separator V from stream 14 leaving the fridge CC1, and the rest of the thread 17 is returned to the reactor R1.

In General, the reactor R1 through line 16a has submitted the following components (formally believed that the formation of urea in the refrigerator CC1 none):

H2O=300 kg/h,

CO2=470 kg/h

NH3=1367 kg/h

Liquid stream 14 coming out of the overflow pipe T reactor, containing all the urea was sent to the Stripping column S1. It is characterized, in particular, the following composition:

urea=1000 kg/h,

H2O=600 kg/h

CO2=400 kg/h,

NH3=800 kg/h,

air=5 kg/h

A Stripping column operates at 15,2 MPa, at a temperature in the cube 205C and under conditions of smoothely.

From the head part Stripping Colo who were taken out of the gaseous stream 13, characterized by the following composition:

CO2=300 kg/h,

NH3=320 kg/h

H2O=100 kg/h,

air=5.5 kg/h

On line 15b in the cube Stripping columns filed the flow of CO2containing air as pestiviruses agent and is characterized by the following composition:

CO2=70 kg/h,

air=0,5 kg/h

The specified thread CO2was heated at node C to a temperature of 197C by re-sending a specific part (aliquots) flow CO2leaving the last stage of compression, at an intermediate stage of heat exchange in the same compressor in accordance with the following scheme shown in figure 1. 733 kg/h of fresh CO2mixed with 5.5 kg/h of air were subjected to compression with an increase of 16.2 MPa and heated to 110C when passing through four successive stages of compression C1, C2, C3 and C4. 668 kg/h of this mixture directed from line 9 to line 9b in the heat exchanger SC3, from which the mixture was along the line 7 at a temperature of 165C by heat exchange with a stream of CO2coming from line 5 at 190C, and then departing on line 6 at 115C. the Entire flow of CO2line 7 was applied to the reactor R1 along the lines 7a, 3a and 9a, while the line 7b remained closed.

The remaining 70,5 kg/h of a mixture of CO2/the air is directed from line 9 to line 9c and 9d in the heat exchanger SC1, from which the mixture was along the line 3 at a temperature of 197C, which was achieved by heat is BMENA with a stream of CO 2coming from line 2 at 200C and out through line 6 at 185C. this mixture CO2/the air is sent to the Stripping column S1 from line 3 to line 3b.

The liquid stream 11, which is extracted from the cube Stripping columns S1, consisted of the following products:

urea=1000 kg/h,

H2O=500 kg/h,

CO2=170 kg/h

NH3=480 kg/h;

this thread was sent to the next stage of purification and concentration of urea. These stages are essentially consist of the usual sections highlight at medium and low pressure sections of concentration characteristic of the traditional process SNAMPROGETTI Urea, a General scheme which is reflected, for example, on page 561 of the already mentioned "Encyclopedia of chemical technology" ("Encyclopedia of Chemical technology").

Example 2

Essentially repeated as described in example 1 process with the difference that containing air stream CO2supplied in a cube Stripping column through line 15b, had the following composition:

CO2=50 kg/h,

air=0,36 kg/h

This stream is also heated to a temperature of 197C by passing through the intermediate stage of compression in accordance with the following scheme, which differs from the schema in example 1.

733 kg/h of fresh CO2mixed with 5.5 kg/h of air was compressed to 16.2 MPa and heated to 110C by passing through the four stages of compression C1, C2, C3 and C4. The entire flow of CO2(738,5 kg/h) and the air is, leaving C4 on line 9, was sent into the heat exchanger SC3 on line 9b, where he goes through line 7 at a temperature of 150C by heat exchange with a stream of CO2coming from line 5 at 190C and the outgoing line 6 at 125C.

An aliquot of the specified flow coming from SC3 on line 7, quantitatively component 50,36 kg/h, directed along the line 7b in the heat exchanger SC1, and then optionally heating it up to 197C by heat exchange with a stream of CO2coming on line 2 at 200C and out through line 4 at 195C, was sent to the Stripping column S1 lines 3 and 3b, the corresponding line 15b in figure 2. The remaining part of the flow line 7, quantitatively component 688,14 kg/h, was sent directly to the reactor R1 at a temperature of 150C on lines 7, 7a, 3a and 9, the corresponding line 15a in figure 2. Line 9c remained closed.

Due to the speed variation of the flow rate supplied to the cube Stripping column through line 15b, 70,50 kg/h on 50,36 kg/h amount of CO2in lines 13, 14 and 17 in figure 2, respectively, are reduced by approximately 20 kg/h compared with example 1.

Example 3

Essentially repeated as described in example 1 process with the difference that containing air stream CO2supplied in a cube Stripping column through line 15b, had the following composition:

CO2=30 kg/h,

air=0.21 kg/h

This stream is also heated to a temperature of 183C in accordance with etousa scheme, different from the schema in example 1.

733 kg/h of fresh CO2mixed with 5.5 kg/h of air was compressed to 16.2 MPa and heated to 110C by passing through the four stages of compression C1, C2, C3 and C4. The entire flow of CO2(738,5 kg/h) and air exiting C4 on line 9, was sent into the heat exchanger SC3 on line 9b, where he goes out on the line 7 at a temperature of 147C by heat exchange with a stream of CO2coming from line 5 at 190C and the outgoing line 6 at 127C.

The entire flow leaving SC3 on line 7, was sent along the line 7b in the heat exchanger SC1 and there was additionally heated to 183C by heat exchange with a stream of CO2coming on line 2 at 200C and out through line 4 at 150C. a Significant portion (30,21 kg/h) flow coming from SC1 on line 3, was sent to the Stripping column S1 lines 3 and 3b, whereas the remaining part of the flow (703,29 kg/h), still at a temperature of 183C, were sent to the reactor R1 along the lines 3a and 9a. Line 9c 7a and remained closed.

Due to the speed variation of the flow rate supplied to the cube Stripping column through line 15b, 70,50 kg/h on 30,21 kg/h amount of CO2in lines 13, 14 and 17 in figure 2, respectively, are reduced by approximately 40 kg/h compared with example 1.

Testing process carried out in accordance with the above examples during the lifetime of one year, did not show significant is rotamania corrosion even in the absence of a separate filing pestiviruses agent in the Stripping column.

1. An improved method for the synthesis of urea from ammonia and carbon dioxide at high pressure and temperature with the formation of ammonium carbamate as an intermediate product including the sections of the synthesis at high pressure, comprising at least one stage of separation by decomposition-Stripping with ammonia, unreacted ammonium carbamate, held in a vertical device, which is a Stripping column, characterized in that this stage also involves feeding in the lower part of the Stripping columns specified flow CO2heated to a temperature of from 130 to 230C., in an amount of from 1 to 15% relative to the total mass supplied to the process fresh CO2containing passivating agent in such a quantity that it is equivalent to the content Of the2in moles is in the range of 0.05 to 0.8% in relation to the number of moles of CO2in the specified thread; and fresh CO2subjected to compression in a multi-stage compressor, comprising the intermediate step of heat exchange.

2. The method according to claim 1, characterized in that the flow of heated CO2fed to the Stripping column has a temperature of from 150 to 210C.

3. The method according to claim 1, characterized in that the flow of heated CO2fed to the Stripping column has a temperature of from 160 to 200C.

4. The method according to claim 1, characterized in that the number of flow of heated CO 2fed to the Stripping column, is from 3 to 12% relative to the total mass of fresh CO2served in the process.

5. The method according to claim 1, characterized in that the quantity of flow of heated CO2fed to the Stripping column, is from 4 to 12% relative to the total mass of fresh CO2fed to the reactor.

6. The method according to claim 1, characterized in that the flow of CO2fed to the reactor has a temperature of 100 to 200C., preferably between 130 to 185C.

7. The method according to claim 1, characterized in that the flow of CO2fed to the Stripping column, and a stream of CO2fed to the reactor, is subjected to heating.

8. The method according to claim 1, characterized in that the flow of CO2supplied in a cube Stripping column, is heated in one or more intermediate stages of said compressor for CO2.

9. The method according to claim 1, characterized in that at least a part and preferably the entire flow of CO2fed to the reactor, heated in one or more intermediate stages of the compressor for CO2.

10. The method according to claim 1, characterized in that the flow of CO2fed to the reactor, consists of a mixture prepared in suitable proportions of the flow of compressed CO2and from the flow of CO2heated at least in the intermediate stage of the compressor, which has a maximum rate is the atur.

11. The method according to claim 1, characterized in that the flow of CO2fed to the reactor and having a temperature of from 130 to 185C., is 0-40% relative to the total mass of the specified stream of compressed CO2coming out of the reactor at a temperature of from 100 to 120C, and 60-100% relative to the total mass of the specified stream from the stream WITH a2heated during one or more intermediate stages of heat transfer from the compressor to a temperature of from 140 to 200C.

12. The method according to claim 1, characterized in that the flow of CO2fed to the Stripping column and on 4-12% representing a CO2directed into the reactor, heated to a temperature of from 160 to 200C. at one or more intermediate stages of heat transfer in compressor for CO2.

13. The method according to claim 1, characterized in that the heated stream of CO2heated in one or more intermediate stages of the compressor for CO2on the outside or in the tube space.

14. The method according to claim 1, characterized in that the phase decomposition/removal of ammonium carbamate, ammonia is a stage smoothely.

15. The method according to claim 1, wherein the passivating agent is present in such quantity that it is equivalent to the content Of the2in moles is in the range from 0.10 to 0.40% in relation to the number of moles of CO2in the specified stream.

16. The method according to claim 1, otlichalis the same time, what passivating agent is an oxidizing agent.

17. The method according to item 16, wherein the oxidant is selected from air, oxygen enriched air, hydrogen peroxide and mixtures thereof.

18. The method according to item 16, wherein the oxidant is air.

19. The method according to claim 1, characterized in that it includes a step of synthesis of urea, where the molar ratio of ammonia/carbon dioxide is in the range from 2.7 to 5.0, preferably from 3 to 4.

20. Installation for the implementation of an improved method for the synthesis of urea according to any one of claims 1 to 19, including the sections of synthesis, where the reactor R1 via line 10 connected to the Stripping column S1, suitable for operation in conditions of "smoothely"connected, in turn, in its lower part through line 11 with section R. isolation and purification of urea, and in its upper part, through line 13 from the capacitor CC1 to carbamate, which, in turn, is connected to the reactor R1 using a sequence of lines 14, 17 and 16A, where the specified reactor R1 also connected to the compressor through line 15A to supply fresh carbon dioxide, characterized in that the compressor is also connected to the lower part of the specified Stripping columns S1 on line 15b, suitable for thread migration CO2in the Stripping column in an amount of from 1 to 15%, before occhialino from 4 to 12% relative to the total mass of fresh CO 2supplied in the installation.

21. Installation according to claim 20, characterized in that it can be obtained by modification of an existing installation for the synthesis of urea, equipped with a Stripping column, suitable for operation in the conditions of smoothely, by providing the connecting line between the compressor for CO2and the lower part of the specified Stripping columns, suitable for flow CO2in the Stripping column in an amount of from 1 to 15%, preferably from 4 to 12% relative to the total mass of fresh CO2supplied in the installation.



 

Same patents:

FIELD: chemistry.

SUBSTANCE: invention relates to a method of modernising a urea production plant (1). The plant includes: a reactor (2) for urea synthesis, means (7, 8) for feeding ammonia and carbon dioxide into said reactor (2) for urea synthesis, an apparatus (3) for desorption with carbon dioxide for treating the reaction mixture from the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution, with partial decomposition of carbamate and partial separation of free ammonia, thus obtaining a stream containing ammonia and carbon dioxide in vapour phase and a stream containing urea and residual carbamate in aqueous solution, a urea extraction section for treating the stream coming out of the desorption apparatus (3) and containing urea and residual carbamate in aqueous solution for separating urea from residual carbamate in aqueous solution, at least one at least one vertical film condensation apparatus (4) for partial condensation of the stream coming out of the desorption apparatus (3) and containing ammonia and carbon dioxide in vapour phase, thus obtaining a liquid stream containing carbamate in aqueous solution and a gaseous stream containing ammonia and carbon dioxide in vapour phase, means (15, 14) for respectively feeding the stream containing carbamate in aqueous solution and the gaseous stream containing ammonia and carbon dioxide in vapour phase into said reactor (2) for urea synthesis. Said at least one condensation apparatus (4) is provided with means for essentially full condensation of at least a portion of the stream coming out of the desorption apparatus (3) and containing ammonia and carbon dioxide in vapour phase to obtain a stream containing urea and carbamate in aqueous solution. The method involves the following stages: providing second desorption apparatus (47), providing means (9) for feeding a first portion of the stream of reaction mixture coming out of the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution into said desorption apparatus (3), providing means (48) for feeding a second portion of the stream of reaction mixture coming out the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution into said second desorption apparatus (47), and providing means (49) for feeding at least a portion of the stream coming out of said second desorption apparatus (47) and containing ammonia and carbon dioxide in vapour phase directly into the synthesis reactor (2). A method of producing urea and a urea production plant are also disclosed.

EFFECT: invention ensures high output of the product with low power consumption.

12 cl, 2 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing carbamide from ammonia and carbon dioxide. The method is carried out at high temperature and pressure, molar ratio NH3:CO2=(3.4-3.7):1, in a carbamide synthesis reactor followed by extraction of excess ammonia from the carbamide synthesis fusion cake by separation at pressure 80-120 kgf/cm2, two-step distillation of the fusion cake, condensation of distillation gases with formation of recycled solutions of ammonium carbonates. First-step distillation is carried out at pressure 80-120 kgf/cm2 in a CO2 current. After distillation, the fusion cake is fed to the second distillation step which is carried out at low pressure. Distillation gases from the first step are condensed in two successive zones at distillation pressure of the first step, where in the first zone, condensation is carried out while feeding a portion of ammonium carbonate solution obtained during condensation of distillation gases at the second step. The condensed vapour is cooled with a condensate which boils at excess pressure to obtain vapour. The ammonium carbonate solution from the second condensation step is fed into the reactor. At the first distillation step, CO2 is used in amount of 30-35% of its total amount fed into the process. Gases and the liquid carbamide synthesis fusion cake are output from the carbamide synthesis reactor separately. Gases from the synthesis reactor and excess ammonia from the separation step are fed into the first condensation zone of distillation gases from the first step. In the second condensation zone of distillation gases from the first step, the condensed vapour is cooled by recycled water and uncondensed gases at the same pressure are washed by the other portion of the ammonium carbonate solution obtained during condensation of distillation gases from the second step, and the formed ammonium carbonate solution is fed into the second condensation zone.

EFFECT: process of producing carbamide with low power consumption.

1 dwg, 1 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing urea from ammonia and carbon dioxide. The method comprises the following steps: feeding ammonia and carbon dioxide into a urea synthesis section operating at given high pressure; reaction of ammonia and carbon dioxide in the synthesis section to obtain an aqueous solution containing urea, ammonium carbamate and ammonia; feeding a first portion of said aqueous solution containing urea, ammonium carbamate and ammonia into a processing section operating at given medium pressure to extract ammonium carbamate and ammonia contained in that solution; dissociation of the first portion of said aqueous solution containing urea, ammonium carbamate and ammonia in the processing section to obtain an aqueous solution of urea and a vapour phase containing ammonia, carbon dioxide and water; condensation of said vapour phase containing ammonia, carbon dioxide and water in the processing section to obtain aqueous ammonium carbamate solution; directing the aqueous ammonium carbamate solution to the repeated cycle in the urea synthesis section. The method also involves feeding aqueous solution of urea obtained at the dissociation step in the processing section into a decomposition apparatus located in the urea extraction section and operating at given low pressure; decomposition of aqueous solution of urea in the decomposition apparatus in the urea extraction section to obtain concentrated urea solution and a second vapour phase containing ammonia, carbon dioxide and water; condensation of the second vapour phase in a condenser located in the urea extraction section and linked to said decomposition apparatus to obtain a first recycle aqueous solution of ammonium carbamate; steam stilling the second portion of aqueous solution containing urea, ammonium carbamate and ammonia while heating in a steam stilling unit essentially at the given high pressure to obtain a second aqueous solution of urea and a third vapour phase containing ammonia, carbon dioxide and water, where said heating is carried out via indirect heat exchange with a vapour stream which forms condensed vapour upon condensation; using at least a portion of the condensed vapour as heat carrier for dissociation of the first portion of the aqueous solution containing urea, ammonium carbonate and ammonia in the dissociation unit located in the processing section at medium pressure. The invention also discloses apparatus for producing urea and a method for upgrading existing apparatus for producing urea.

EFFECT: invention increases production capacity of apparatus for producing urea while simultaneously ensuring high degree of conversion of carbon dioxide to urea.

21 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention refers to the way of carbamide production at higher temperatures and under the pressure in the installation that contains a high pressure section including a reactor, stripper, condenser and gas washer. The method includes interaction between ammonia and carbon dioxide in the reactor with formation of the reactor feed and separate withdrawal of the liquid flow containing carbamide, ammonium carbamate and free ammonia in water solution from the reactor, and the gas flow containing predominantly inert gases. The flows of liquid and gas carbon dioxide are fed to the high pressure section. The liquid flow from the reactor is for to the stripper for partial decompounding of the ammonium cabamade and partial release of the free ammonia in the current of the gas carbon dioxide that is introduced into the stripper and includes ammonia and carbon dioxide admixed with water vapour, and of the liquid flow including carbamide and residual ammonium carbamade in the water and ammonia solution. The liquid flow from the stripper is fed at the stage of subsequent decompounding of the ammonium carbamade and separation of ammonia and carbon dioxide thus obtaining carbamide and recirculating liquid flow containing ammonium carbamade in the water and ammonia solution. The gas flow from the stripper is fed to the condenser for partial absorption and condensation in the course of mixing with ammonia and the liquid flow from the gas washer. The liquid flow from the condenser is fed to the reactor. The gas flow from the reactor is cleaned from ammonia and carbon dioxide while contacting with the recirculating liquid flow in the gas washer. The flow of liquid carbon dioxide is introduced into the reactor or condenser after it has been mixed with another process flow; the flow of liquid carbon dioxide is mixed with the liquid flow coming out from the gas washer or the condenser.

EFFECT: improvement of reliability of the applied equipment.

4 cl, 3 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: carbamide is obtained at high temperature and pressure in an apparatus having a high-pressure section, including a reactor, a stripper, a condenser and a scrubber, using a method which involves reaction of ammonia and carbon dioxide in the reactor to form a reaction mixture and separate outlet from the reactor of a liquid stream containing carbamide, ammonium carbamate and free ammonia in aqueous solution, and a gas stream mainly containing inert gases, feeding into the high-pressure section streams of liquid and gaseous carbon dioxide, feeding the liquid stream from the reactor into the stripper for partial decomposition of ammonium carbamate and partial extraction of free ammonia in the current of gaseous carbon dioxide fed into the stripper to obtain a gas stream containing ammonia and carbon dioxide with a water vapour impurity, and a liquid stream, feeding the liquid stream from the stripper to the next ammonium carbamate decomposition step and separating ammonia and carbon dioxide to obtain carbamide and a recycled liquid stream containing ammonium carbamate in an aqueous ammonium solution, feeding the gas stream from the stripper into the condenser for partial absorption-condensation thereof while mixing with ammonia and the liquid stream from the scrubber, feeding the liquid stream from the condenser into the reactor, removing ammonia and carbon dioxide from the gas stream from the reactor upon contact with the recycled liquid stream in the scrubber, where the stream of liquid carbon dioxide is fed into the high-pressure section after mixing with another process stream, where the stream of liquid carbon dioxide is mixed with a gas stream coming from the stripper or condenser, in the apparatus for mixing said streams, where when feeding the liquid stream into an insert with a variable cross-section through a convergent nozzle and the gas stream into the housing, liquid carbon dioxide evaporates through contact in the insert with part of said gas stream entering the insert, followed by contact of the mixed stream at the outlet of the insert with the remaining part of the gas stream passing through a slit between the insert and the housing.

EFFECT: high reliability of the used equipment.

4 cl, 3 ex, 4 dwg

FIELD: medicine, pharmaceutics.

SUBSTANCE: invention relates to method of obtaining carbamide with stable carbon isotope 13C for application in medical diagnostics of gastrointestinal tract diseases. Claimed method has two stages, the first stage includes interaction of labeled carbon dioxide and propylene oxide at temperature 120-130C and pressure 1.3-1.5 MPa in presence of catalyst with further isolation of labeled propylene carbonate. Catalyst of the first stage is complex of zinc bromide with tertiary organophosphine or 1-butyl-3-methylimidasolium chloride, and mole ratio of propylene oxide to catalyst constitutes 500-2000:1. At the second stage carried out is ammonolysis of isolated liquid propylene carbonate at temperature 130-150C and pressure 5.0-7.0 MPa with further isolation of target product.

EFFECT: method ensures obtaining carbamide, labeled by stable isotope 13C, with high output with sufficient simplicity and manufacturability of method and absence of highly toxic and explosive substances.

4 cl, 2 tbl, 14 ex

FIELD: agriculture.

SUBSTANCE: liquid ammonia and carbon dioxide are fed to a synthesis section (100) and exposed to a reaction in it in order to produce urea. At the same time the synthesis section comprises at least a reactor, a steaming device and a capacitor, which form a high-pressure circuit, and at least some carbon dioxide is sent to the synthesis section (100) in the liquid phase. Also a plant is proposed for production of urea, as well as a method to increase urea production plant efficiency.

EFFECT: increased energy efficiency of urea production method.

13 cl, 7 dwg

FIELD: process engineering.

SUBSTANCE: invention relates to plant intended for producing carbamide from ammonium and carbon dioxide at elevated temperature and pressure. Proposed plant comprises high-pressure section comprising reactor, stripper, condenser and scrubber operated at in face one pressure, liquid ammonium feeder, appliance to feed gaseous and liquid carbon dioxide into high-pressure section, appliances to feed liquid flows from reactor into stripper, from stripper at carbamide and circulated liquid flow extraction stage, from condenser into reactor, from scrubber into condenser, appliances to feed gas flows from reactor into scrubber, from stripper into condenser, appliances to feed circulated liquid flow into scrubber, appliance to mix liquid carbon dioxide with another flow including cylindrical housing with appliances to feed liquid carbon dioxide, another process flow and to discharge mixed flow, as well as tapered nozzle arranged inside said housing and aligned therewith and communicated with liquid carbon dioxide feed appliance. Note here that appliance to mix liquid carbon dioxide with gaseous carbon dioxide comprises gaseous carbon dioxide feed union and variable-section insert made up of tube with convergent inlet section and divergent outer. Note also that said insert is arranged to form annular clearance between housing and insert. Also it's proposed the method of carbamide production.

EFFECT: higher reliability.

2 cl, 2 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to apparatus for producing carbamide from carbon dioxide and liquid ammonia at high pressure and temperature, comprising a carbamide synthesis reactor, a pump for feeding liquid ammonia into the carbamide synthesis reactor, a compressor for feeding gaseous carbon dioxide into the carbamide synthesis reactor, a pump for feeding liquid carbon dioxide into the carbamide synthesis reactor, a device for bringing into contact carbon dioxide streams, characterised by that the device for bringing into contact carbon dioxide streams has a cylindrical housing with nozzles for inlet of liquid carbon dioxide, inlet of gaseous carbon dioxide and outlet of the mixed gaseous stream of carbon dioxide, as well as the following, arranged in series inside the housing and coaxial with the housing: a convergent nozzle connected to the liquid carbon dioxide inlet nozzle, and a variable cross-section insert in form of a pipe, the inlet part of which is convergent and the outlet part divergent, where the insert lies in such a way that an annular slit forms between itself and the housing. The invention also relates to a method of producing carbamide using the described device.

EFFECT: use of the present invention simplifies process design, reduces materials consumption of the equipment used and increases reliability of the equipment used.

2 cl, 3 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a novel method of producing carbamide with a stable 13C isotope used in medical diagnostics, involving reaction of labelled carbon dioxide and ethylene oxide at temperature 80-150C, pressure 2.1-6 MPa in the presence of a catalyst - complex of zinc bromide and tertiary organophosphines in molar ratio of ethylene oxide to the catalyst equal to 500-5000:1, followed by extraction of the labelled ethylene carbonate and ammonolysis of the extracted ethylene carbonate at temperature 120-170C and pressure 2.8-4.7 MPa.

EFFECT: possibility of obtaining an end product with good output using a fairly simple and technologically effective method.

4 cl, 14 ex, 2 tbl

FIELD: industrial inorganic synthesis.

SUBSTANCE: aqueous carbamate solution leaving urea recovery section at a certain temperature is decomposed by indirect heat exchange with flowing heat carrier having specified temperature. Temperature difference between aqueous carbamate solution and heat carrier is thus decreased to a value not exceeding 70°C, preferably to a value within a range of 20-40°C. Aqueous carbamate solution, prior to be fed into decomposition apparatus, is preheated in heat exchanger by stream produced in evaporation zone containing ammonia and carbon dioxide in vapor phase.

EFFECT: increased efficiency of apparatuses designed for decomposition of recycled carbamate solution.

6 cl, 2 dwg

FIELD: chemical technology.

SUBSTANCE: invention relates to producing urea from ammonia and carbon dioxide. Method involves preparing products of reaction in the synthesis zone as a solution containing urea, ammonium carbamate and unreacted ammonia. Part of solution obtained in synthesis of urea (preferably 10-60 wt.-%) is fed from the synthesis zone to additionally assembled zone of treatment under mean pressure at 1-4 MPa wherein gas flow is separated and subjected for absorption with ammonium carbamate solution of low pressure supplying from the section for isolation and treatment of urea. As a variant of method the invention proposes to use the combined reactor in the synthesis zone representing vertically installed or combined reactor. Enhancement of output of existing processes in synthesis of urea is achieved by feeding part of urea solution synthesized in the synthesis reactor to additionally installed zone for treatment of mean pressure including the dissociation zone, desorption zone of mean pressure and the condensation zone of mean pressure. Invention provides enhancement of output of unit for producing urea being without modification of section of high pressure.

EFFECT: improved method for producing urea.

10 cl, 4 dwg

FIELD: chemical technology.

SUBSTANCE: invention relates to technology for preparing urea. Method involves interaction of pure ammonia and carbon dioxide in reaction space to obtain reaction mixture containing urea, carbamate and free ammonia in an aqueous solution that is treated in evaporator (1) to obtain partially purified mixture that is fed to section for isolation of urea. Diluted solution of carbamate removing from the urea isolating section is subjected for treatment in evaporator (2) and at least part of vapors formed in it is recovered to the reaction space and/or into evaporator (1). Significant part of carbamate in aqueous solution is subjected for decomposition under pressure that corresponds essentially to pressure value in reaction space. Part of decomposition products including ammonia and carbon dioxide in vapor phase is recovered into reactor and/or into the first evaporator (1) and carbamate after its partial decomposing is fed into section for isolating urea. Device for preparing urea consists of the synthesis reactor, evaporators (1) and (2) for partial decomposition of carbamate and for separation of free ammonia and carbon dioxide in vapor phase, apparatus for condensation of vapor flow, pipe-line for recover of carbamate part in aqueous solution into reactor and section for isolation of urea from its aqueous solution. Preferably, pipe-line is fitted with ejector and evaporators are fitted with apparatus for feeding carbon dioxide as a evaporating agent. Invention provides enhancing yield of urea, reducing energy consumptions and investment due to updating the technological schedule of the process.

EFFECT: improved preparing and updating methods.

30 cl, 4 dwg

FIELD: chemical industry; devices and methods of production of carbamate.

SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to carbamatecondenserof the sinking type used in the installation for production of the synthesized carbamide from the gaseous carbon dioxide and the liquid ammonia. The condenser (1) of the sinking type contains the bundle (5) of pipes, in which the condensation of the gaseous compounds is exercised and as a result of the interaction of ammonia with carbon dioxide the carbamate is formed. The condenser differs from others by availability the condensate circulating pipe (19, 23) structurally not connected with the bundle (5) of pipes and designed for circulation of the components in the closed contour of the condenser (1)of the part of the condensed inside it gaseous compounds. The availability of the separate circulating pipe structurally not connected with the bundle of the condensation pipes and communicating with the upper and the lower parts of the condenser ensures the possibility of circulation of the carbamate passing over of the bundle of the condensation pipes, what allows to increase essentially the output of carbamate gained as a result of condensation.

EFFECT: the invention allows to raise essentially the output of carbamate gained as a result of condensation.

6 cl, 3 dwg

FIELD: chemical industry; methods and the devices for production of carbamide from ammonia and carbon dioxide.

SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to the methods and the devices for production of carbamide from ammonia and carbon dioxide. The method of production of carbamide includes the interaction of ammonia and carbon dioxide in the zone of synthesis at the heightened temperatures and pressures with formation of the melt of the carbamide containing carbamide, water, ammonium carbamate, ammonia and carbon dioxide. The carbamide melt distillation conduct at the heat feeding on the two stages of pressure preferentially at 15-25°C and 2-5 kgf/cm2. The carbamide melt distillation on the first step of the pressure conduct sequentially in two zones. In the first zone the distillation is conducted adiabatically or at the heat feeding, and in the second zone - at the heat feeding in the stream of carbon dioxide. The condensation-absorption process at refrigeration of the gases of the distillation is conducted with utilization of the aqueous absorbers. The formed aqueous solutions of the carbon- ammonium salts are recycled from the stage of the condensation-absorption of the gases of the distillation of the second step to the stage of the condensation-absorption of the gases of distillation of the first step, and also from the stage of the condensation-absorption of the gases of distillation of the first step into the zone of the synthesis. The evaporation of the aqueous solution of carbamide is exercised in some steps at the heat exchange between the gases of the distillation of the first step and the aqueous solution of carbamide at the stage of the preliminary evaporation. The installation for production of carbamide consists of: the reactor of the carbamide synthesis; the device with the heat feeding from the external source for distillation of the carbamide melt produced in the reactor of the carbamide synthesis at the first step of the pressure and consisting of the column of distillation melt of the first step and the film-type heat exchanger; the device with the heat feeding for the distillation of the carbamide melt on the second step of pressure; apparatuses for evaporation at heating of the aqueous solution of the carbamide produced on the second step of distillation. The devices for condensation-absorption at refrigeration of the gases of the distillation of the both steps switch on the heat exchanger-recuperator for heat interchange between the gases of the distillation of the first step and the aqueous solution of carbamide. The installation also contains a means for feeding of ammonia and carbon dioxide into the reactor of synthesis of carbamide, feeding of the carbamide melt from the reactor of synthesis into the column of distillation of the first step, from the column of distillation of the first step into the film-type heat exchanger and from the film-type heat exchanger into the device for distillation of the second step, the aqueous solution of carbamide from the device for distilling of the second step into the heat exchanger-recuperator and from the heat exchanger-recuperator - into the apparatus for the subsequent evaporation; the gases of distillation from the device for distilling of the first step - in the heat exchanger-recuperator and from the heat exchanger-recuperator - into the device for condensation-absorption of the gases of distillation of the first step; the gases of distillation from the apparatus for distillation of the second step - into the device for condensation-absorption of the gases of distillation of the second step; the solution of the carbon-ammonium salts from the device for condensation-absorption of the gases of distillation of the second step - into the device for condensation-absorption of the gases of distillation of the first step and from the device for condensation-absorption of the gases of distillation of the first step - into the reactor of synthesis, a means for feeding of carbon dioxide into the film-type heat exchanger. The technical result of the invention is the increased degree of the heat recuperation of the production cycle and reduction of he quantity of the heat exchangers using the heating steam from the external sources.

EFFECT: the invention ensures the increased degree of the heat recuperation of the production cycle and reduction of he quantity of the heat exchangers using the heating steam from the external sources.

8 cl, 3 ex, 3 dwg

FIELD: chemical industry; methods of synthesis of carbamide and the column for its realization.

SUBSTANCE: the invention is pertaining to the method of synthesis of carbamide from ammonia and carbon dioxide in the column of synthesis with the gas-liquid recycle, at which the stream of the water solution of the carbon-ammonium salts (CAS) from the area of distilling route from above or from below into the middle of the synthesis column containing the vertical cylindrical body, the corrosion-resistant material lining located on the body interior surface, the mixer and the unions of inlet and outlet of the reactants and having the located inside it perforated pipeline, which holes are disposed in pairs along the pipeline perimeter at the level of the column muddle midpoints of a column at the angle of 20° - 60° to the central axis of the column. The technical result of the invention consists in intensification of the contacting of the introduced components, the increased service life of the column lining layer and the raised conversion due to removal of the surplus of the water formed during the synthesis process.

EFFECT: the invention ensures intensification of the contacting of the introduced components, the increased service life of the column lining layer, the raised of conversion.

3 cl, 3 dwg

FIELD: chemical industry; methods of production of carbamide from carbon dioxide and ammonia.

SUBSTANCE: the invention is pertaining to the method of production of carbamide from carbon dioxide and ammonia. The method of production of carbamide is realized in the reactor of synthesis with the subsequent thermal distillation from the reaction mixture of the carbamate and partially ammonia in the high-pressure apparatus at heat input by means of the steam. The separated gas phase is directed for condensation into the high-pressure condenser, where gas condensation heat is transferred to the heat-carrier with formation of the steam A. The carbamide solution from the high-pressure apparatus is fed for the ammonium carbamate decomposition into the apparatus at the average pressure with usage of the heat carrier. At that as the heat carrier use the steam condensate produced after the high-pressure apparatus in the combination the steam A. The high-pressure condenser represents the submerged condenser. The installation for production of carbamide includes the reactor of the synthesis of carbamide, the high-pressure apparatus for the thermal distillation of the carbamate and ammonia from the solution of synthesis of carbamide with the heat supply by means of the heat carrier, and also contains the apparatus for ammonium carbamate decomposition at the average pressure. As the high-pressure condenser used for the gas phase condensation the installation contains the submerged condenser. The method of the installation upgrade consists that the existing high-pressure condenser is substituted for the submerged condenser. The technical result of the invention is reduction of the power inputs due to upgrade of the equipment and the combined usage of the scheme of recuperation of the heat of the heat carriers.

EFFECT: the invention ensures the reduced power inputs, the upgrade of the equipment, the combined usage of the scheme of recuperation of the heat of the heat carriers.

12 cl, 2 dwg

FIELD: chemical industry; methods and devices for production of carbamide.

SUBSTANCE: the invention is pertaining to the methods and devices for production of carbamide from ammonia and carbon dioxide. At realization of the method the reaction mixture from the synthesis reactor is fed in the stripper for the partial decomposition of the ammonium carbamate in the flow of the source carbon dioxide at the pressure practically equal to the pressure in the synthesis reactor. The stream of the source carbon dioxide is divided into two parts, one of which is routed into the stripper, and the other part is used as the working stream for injection of the gas stream from the stripper into the vertical condenser. The liquid stream from the stripper is fed at the stage of the subsequent decomposition of the ammonium carbamate, and the gaseous stream from the stripper is injected into the lower part of the vertical condenser for its mixing with source liquid ammonia. The liquid stream from the vertical condenser is fed into the synthesis reactor, butt from the gaseous stream absorb ammonia and carbon dioxide. The installation for production of carbamide consists of: the synthesis reactor; the scrubber for purification of the gaseous streams from the reactor from ammonia and carbon dioxide; the stripper for the partial decomposition of the ammonium carbamate; the vertical condenser, in which the mixing of the gas stream from the stripper with the source liquid ammonia takes place. The stripper is connected to the lines of feeding of the fluid stream from the reactor and the stream of the source carbon dioxide, and also is equipped with tool for injection of the gaseous stream from the stripper into the vertical condenser by the part of the stream of the source carbon dioxide. By the liquid stream the stripper is linked with the apparatuses for the subsequent decomposition of the ammonium carbamate and extraction of carbamide. The method of upgrading of the installation for production of carbamide consists in connection of the reactor of the synthesis to the stripper for the partial decomposition of the ammonium carbamate in the flow of the source carbon dioxide, in equipping the stripper with the tools for injection of the gaseous stream from the stripper into the vertical condenser with the part of the stream of the source carbon dioxide, and also in the availability of the lines of delivery of the gaseous mixture after the injector and the feeding line of the source liquid ammonia into the lower part of the vertical condenser. The technical result of the invention is the increased degree of conversion of the source reagents into carbamide at reduction of the scale of recirculation of the non-converted reactants.

EFFECT: the invention ensures the increased degree of conversion of the source reagents into carbamide at reduction of the scale of recirculation of the non-converted reactants.

11 cl, 2 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of condensing carbamate through condensation of gaseous phase of carbon dioxide and ammonia into a liquid phase, which is carbamate in aqueous solution and optionally a solution which contains urea and non-reacting substances and liquid ammonia, in a submerged-type condenser, containing a given number of heat-exchange pipes in a bundle, meant for condensing carbamate, into each of which gaseous and liquid phases are fed simultaneously and independently from each other. The invention also relates to a submerged-type device for condensing carbamate.

EFFECT: increased efficiency and output of the method of condensing carbamate in the proposed device.

14 cl, 4 dwg

FIELD: process engineering.

SUBSTANCE: invention relates to corrosionproof fluid flow conducting parts and equipment comprising one or more such parts. Equipment component comprises first fluid corrosionproof flow conducting section that comprises first corrosionproof material and second fluid flow conducting section that comprises second material. First and second sections are, directly or indirectly, have their ends welded together in solid state to make integral fluid flow conducting part. Invention covers also the method of replacing at least one fluid flow conducting equipment part that proposes replacement component comprising first fluid flow conducting section that includes first material and second fluid flow conducting section that includes second material. Second material is, in fact, identical to that of equipment section whereat spare part is to be mounted. First and second sections are, directly or indirectly, have their ends welded together in solid state to make integral fluid flow conducting part. Space part is secured to equipment by flush butt welding of second material of second space part with material being, in fact identical, to that of equipment attachment section.

EFFECT: higher efficiency due to replacement with parts that feature improved corrosion resistance properties.

101 cl, 2 ex, 4 tbl, 14 dwg

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