Installation for the production of urea and the way of its improvement

 

(57) Abstract:

The invention relates to the technology of production of urea from ammonia and carbon dioxide. The apparatus comprises first and second reactors for the synthesis of urea, the partition separating the reaction mixture, including the section of the separation of free ammonia and carbamate from an aqueous solution of urea from the reaction products of the first and second reactors. As the second reactor installation includes a single reactor type with a higher performance than the performance of the first reactor synthesis of urea, and a second reactor connected in parallel to the first reactor. In the first reactor to maintain a pressure of about 150 bar and a temperature of about 190oC, and the second reactor provides a pressure of about 240 bar and a temperature of about 195oC. the Second reactor contains a primary partition that includes the reactor boiler type, which can provide partial removal of heat of reaction. The way of improvement of plants for the production of urea is that the first reactor synthesis of urea connect the liquid communication line with the section of the distillation of the ammonia, which is designed for separation of free ammonia and carbamate in the flow of a single type, having higher performance than the first reactor. The overall performance of the production is distributed so that the first reactor synthesis of urea has the performance of 50-95% of the total capacity and performance of the second reactor is 5-50% of the total capacity. As a result of increased production efficiency. 2 C. and 10 C.p. f-crystals, 3 ill.

The invention relates to a method of upgrading an existing manufacturing for production of urea, comprising a first reactor for the synthesis of urea, the associated liquid communication line with the host evaporation of the ammonia, which is the separation of free ammonia and carbamate, coming out of the reactor, an aqueous solution of urea, which contains the stage providing a second synthesis reactor urea single type, providing more effective than the first reactor synthesis of urea.

The invention relates also to upgraded device for the production of urea, which may be arranged as indicated above.

It is known that there is often a need to increase the output and production capacity of urea on an already existing company. To present the STV, for example, proposed by the present applicants as described in European application EP-A-0 479103.

In the application EP-A-0 479103 describes a method (process) of receipt of urea, in which the high purity ammonia and carbon dioxide react in the first reactor (reactor) and the thus obtained reaction mixture is fed into the extraction section, and then in the second reactor (reactor) carry out the reaction between the less pure reagents, largely dedicated to re-cycle the node extraction (return mix).

In accordance with the above mentioned European application increasing the capacity of existing production is achieved by installing an additional a single reactor with a large output (i.e., served reagents, without recirculating water) in parallel with the existing reactor, which operates in accordance with the General technology of recycling (i.e., serves not only pure chemicals, but an aqueous solution of carbamate after recycling).

Despite the fact that in this way we can increase the production capacity of urea, however, there remain a number of problems that hinder the effective modernization of production is 3, the reaction mixture, leaving an additional reactor, cannot be treated in sections evaporation (distillation) of ammonia and she should pass that requires an increase in the power section (node) extract below two synthesis reactors operating in parallel, and leads to a significant increase in the level of energy consumption in the process of synthesis of urea.

So, the problem which is solved by the present invention, is the need to develop ways of upgrading an installation for production of urea, which can significantly increase power while reducing the total required power thus created the upgraded installation.

This problem is solved according to the present invention by developing the above way of modernization, characterized in that it comprises the stage of:

a) attaching the specified second reactor and the upper part (to the place of entrance flow) of the said section of the distillation of ammonia, and to the means for supplying high-purity ammonia and carbon dioxide;

b) the distribution of the total production capacity to separate from 50 to 95% of the specified power to the first reactor synthesis of urea, and 5 to the ohms of the present invention the desired increase capacity and reduce energy consumption at the same time are achieved with less load on the existing reactor and a load of additional reactor, which is achieved by increasing the production capacity.

The best option is that, when the auxiliary reactor is a single type with partial heat generated during the reaction (nonadiabatic): this method also increases the total output of the upgraded installation.

Other aspects and advantages of the method according to the present invention will become clearer from the following description of a preferred variant of the invention, not limiting the present invention, which is given for explanation with reference to the below drawings, of which:

Fig. 1 is a standard diagram of the process of production of urea, including the sections of the distillation of the ammonia, which is used in the analog;

Fig. 2 is a diagram of manufacturing process, resulting in the modernization of the installation shown in Fig. 1, in accordance with the present invention; and

Fig. 3 is a schematic depiction of the setup shown in Fig. 2, with nonadiabatic reactor single type.

In Fig. 1, which shows the installation known from analogue refers to the synthesis reactor is connected fluid communication with a section of the distillation of ammonia (SS), includes desorber S (athanasou section).

A large part of the carbamate contained in the urea solution leaving the reactor R, and a part of the present unbound ammonia is distilled over in desorber S and returned to the reactor, while having the urea solution SU with relatively low residual content of carbon dioxide (5-7 wt%), and relatively high ammonia content (22-25% weight).

Section distillation of ammonia SS, in turn, is connected liquid communication line with site selection urea RE, which includes a step of distillation, with an average pressure SMP working under pressure 18-20 bar, distillation column CR and distiller LP low pressure, pressure of about 4 bar.

In a distillation column CR of a solution of carbamate SC separates the flow of ammonia NEP high purity.

To supply pure ammonia, obtained by mixing flow NEP and the flow of fresh ammonia NA, as well as for recycling solution of carbamate SC in the fridge carbamate CC and then to the synthesis reactor R is installed, respectively, the pumps P and P'.

Main technical characteristics in the Isobaric process, distillation (separation) of ammonia is carried out at specified is MIAK/carbon dioxide in the reactor 3,2-3,4

Mol. the ratio of water/carbon dioxide in the reactor is 0.6 - 0.8

The temperature in the reactor,oC - 180-190

Output, % - 62-63

Steam consumption, kg per metric ton of urea - 900

The above values were considered to be quite solid and further significant improvement process was not possible.

In accordance with the present invention, the installation depicted in Fig. 1, modernized by:

a) placement upstream of a section of the distillation of ammonia SS, the second reactor synthesis of urea single type of ROT that has a higher effective yield than the first reactor synthesis of urea R;

b) attaching a reactor ROT to partition separating ammonia SS through pipe C and the means 4 and 5 for the filing, respectively, of high-purity ammonia and carbon dioxide;

b) distribution of total power production in a certain proportion, so that from 50 to 95% of the specified power are at the first reactor synthesis of urea R, and from 5 to 50% of the specified power attributable to the second reactor synthesis of urea ROT.

The scheme is organized so the setup is shown in Fig. 2.

In accordance with the present invention, the parallel reactor of the type who, and the reactor with partial heat released by the reaction,

For the purposes of the present invention operating pressure and temperature in a single reactor ROT, respectively, must be between 230 and 270 bar and from 190 to 205oC.

Anyway, in the best embodiment of the present invention using a single reactor ROT with partial removal of the reaction heat is preferable to upgrade the Department of ammonia.

In Fig. 3 shows a retrofit for the production of urea, in which the parallel reactor ROT consists of two sections: primary partition ROT. AC, heat generated by the reaction; secondary section ROT.CC conventional type.

Section ROT.AC preferably contains the reactor so-called boiler type.

In this connection it should be noted that the use of the reactor for the synthesis of urea boiler type in the method according to the present invention provides additional benefits associated with a marked decline in investment as a reactor of this type can be powered by existing sediment for feeding ammonia, having a maximum nazwie with another aspect of the present invention can be obtained, distributing the load between the existing reactor R and additional single reactor ROT, the average conversion rate significantly greater than at the facility prior to its modernization.

The most favorable is that it gives you room for transshipment to the main equipment installation including desorber S, condenser (refrigerator) carbamate CC, stage distillation at an average pressure of the SMP, as well as significant expansion of "bottlenecks" (without modification of the main equipment), limiting the throughput of the installation as a whole.

In accordance with the present invention, the total capacity of the existing production is distributed in certain proportions, so that from 50 to 95% of the specified capacity has an existing reactor for the synthesis of urea R, and from 5 to 50% of specified capacity has additional reactor for the synthesis of urea ROT.

Most preferred is the option, when the proportion of the total production capacity per reactor R, ranges from 55 to 65%, while the share of single reactor ROT is from 45 to 35%.

With the aim to better explain the present invention, the following is not limiting the ka, with the help of 1500 metric tons of urea per day.

Example. The installation of the production of urea with the Department of ammonia, with a capacity of 1,500 metric tons of urea per day, including the synthesis reactor R with a working pressure of 145 bar, section, division SS and section allocation RE, including stills medium pressure (SMP) and low pressure (LP) pressure, respectively, 18 and 4 bar, modernize so that his new production capacity is 1500 1,5 = 2250 metric tons of urea per day.

To reduce thermal load an existing partition branch of the SS section allocation RE (except vacuum node) download reactors R and ROT as follows, MT/day of urea:

The existing reactor (R) - 1350

Additional reactor (ROT) - 900

Total - 2250

Operational characteristics of the reactor are presented below:

a) before upgrading

The existing reactor R:

Capacity MT/day - 1500

The molar ratio of ammonia/carbon dioxide - 3,6

The molar ratio of water/carbon dioxide - 0,68

Output, % - 62

Pressure, bar - 145

Temperature, % - 190

b) after upgrading

B. 1 Existing reactor R:

Output, % - 61

Pressure, bar - 145

TemperatureoC - 190

B. 2 single reactor ROT:

Capacity MT/day 900

The molar ratio of ammonia/carbon dioxide - 3,6

The molar ratio of water/carbon dioxide - 0

Output, % - 75

Pressure, bar - 242

TemperatureoC - 193

The total yield obtained from the two reactors operating in parallel, is

< / BR>
i.e., 4.6% more than the output on the unit to its modernization.

When the steam consumption is reduced, despite an increase in plant capacity, approximately 100-130 kg per metric ton of urea.

During the modernization of existing desorber S, section allocation, RE, including the stage distillation at an average pressure of SMP and distiller low pressure LP and the carbamate condenser CC does not require any modification to match the increase in production capacity.

1. The way of improvement of plants for the production of urea, which use the first reactor synthesis of urea directly connected to the liquid communication line with the section of the distillation of the ammonia, which is designed for separation of free ammonia and carbamate in the flow of products is having better performance than the first reactor, characterized in that the flow from the top of the second reactor is sent to the distillation section of the ammonia that is connected to the first reactor and the second reactor is connected to a device for the supply of high-purity ammonia and carbon dioxide, distribute the overall performance of the production so that the first reactor synthesis of urea has a capacity of 50 - 95% of the total capacity and performance of the second reactor is 5 to 50% of the total capacity.

2. The method according to p. 1, characterized in that in the first reactor synthesis of urea, the process is conducted at a pressure of about 150 bar and at a temperature of about 190oC.

3. The method according to p. 1, characterized in that in the second reactor for the synthesis of urea, the process is carried out with partial removal of the heat of reaction.

4. The method according to p. 1, characterized in that in the second reactor synthesis of urea place of the primary section in which the partial dissipation.

5. The method according to p. 4, characterized in that the primary partition of the second reactor comprises a reactor boiler type.

6. The method according to p. 1, characterized in that in the second reactor for the synthesis of urea, the process is conducted at a pressure of about 240 bar and at a temperature of 190 - 195oC.

8. Installation according to p. 7, characterized in that it contains the first reactor, providing the pressure of the synthesis of urea to about 150 bar and a temperature of about 190oC.

9. Installation according to p. 7, otlichay.

10. Installation under item 9, characterized in that in the second reactor synthesis of urea posted by the primary partition, which is designed for partial heat dissipation.

11. Installation according to p. 10, characterized in that it contains the specified primary section of the second reactor which includes a reactor boiler type.

12. Installation according to p. 7, characterized in that it contains a second reactor, providing a pressure of about 240 bar and a temperature of 190 - 195oC.

 

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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; 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 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 production of urea from ammonia and carbon dioxide. A reaction mixture is obtained in a synthesis reactor at given high pressure as a result of a reaction between NH3 and CO2, where the said reaction mixture contains urea, ammonium carbamate and free ammonia in aqueous solution, from which ammonium carbamate and ammonia are extracted and subsequently returned to the synthesis reactor. Ammonium carbamate and ammonia are extracted from the reaction mixture on process steps for decomposing ammonium carbamate to NH3 and CO2 and their stripping and on the next process step for their re-condensation to obtain ammonium carbamate which is returned to the synthesis reactor. The reaction mixture obtained as a result of the reaction between ammonia and carbon dioxide is taken to the process steps for decomposition and stripping using a pump.

EFFECT: changing production capacity by changing pump parameters, possibility of horizontal assembling, reduced expenses on servicing and increased safety.

12 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining urea from ammonia and carbon dioxide. As a result of ammonia and carbon dioxide interaction at high pressure in reactor obtained is water solution, which contains urea, ammonium carbamate and ammonia. From obtained water solution carbamate and ammonia are separated by decomposing carbamate and thermal evaporation of ammonia and carbon dioxide in stripping apparatus, obtaining ammonia and carbon dioxide, which after that are again condensed in condenser obtaining carbamate, which is returned to reactor. All stages together with reaction of synthesis are carried out in fact at one and the same pressure. In addition, into reactor additionally supplied is passivating oxygen, obtained as a result of interaction waste gases, which contain carbon dioxide, ammonia and passivating oxygen which did not take part in the reaction, are removed from reactor and are supplied into bottom part of stripping apparatus for passivation of at least part of its internal surfaces. Installation for obtaining urea contains communicating with each other and forming closed high pressure contour reactor, stripping apparatus, condenser, section of final urea purification and pipelines for supply into reactor of carbon dioxide and ammonia. It is equipped with pipeline for supply into reactor of passivating oxygen and pipeline for connecting upper part of reactor with bottom part of stripping apparatus.

EFFECT: ensuring even and efficient passivation of all apparatuses of high pressure contour.

13 cl, 2 dwg

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

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