The way of modernization of the plant for producing urea (variants) and a device for producing urea (options)

 

(57) Abstract:

The invention relates to improvements in the technology of production of urea from ammonia and carbon dioxide. Urea is obtained on the installation, including two synthesis reactor, equipment for desorption, which produce partial decomposition of the carbamate in the reaction mixture coming from the zone of the synthesis of the first and second reactors, and partial separation of free ammonia vapors in a mixture with water vapor and impurities. After the partial condensation of vapors receive the first urethane solution returned in the first synthesis reactor. The second synthesis reactor have to equipment for desorption and connect with the latest. The second urethane solution obtained in section separation for selection urea, return to the second reactor. Thus, the installation includes additional equipment for recycling the second urethane solution obtained at the stage of allocation of urea, in the second synthesis reactor, as well as equipment for return to the second reactor flow of ammonia and carbon dioxide in vapour phase. In the reach simplifying technology to increase the yield of the final product. 4 C. and 22 C.p. f-crystals, 8 ill.

About the property modernization of the plant for producing urea, contains:

reactor for the synthesis of urea;

- equipment for desorption, in which the first reaction mixture taken from the reactor, is subjected to processing, consisting in a partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the mixture;

- equipment for at least partial condensation of the vapors taken from the equipment for desorption and recycling of the first urethane solution in the reactor;

section selection urea, in which the urea is obtained in the reactor, is separated from the second aqueous urethane solution.

The present invention relates also to a device for producing urea, representing the installation, streamlined offer in the invention method.

Among the problems that must be solved in real time upon receipt of urea are problems associated with the need to create installations, on the one hand, improved performance and process flexibility, and on the other hand, require to create a small investment and low production costs, particularly low energy consumption.

In these processes all production of urea is distributed between the main reaction space, in which at low output get most of all received at the installation of urea (typically from 60 to 80%), and additional so-called "forward" reaction space in which the high output given the same amount of urea, which allows you to bring the total capacity of the plant to the nominal value. According to the technological scheme of these processes, the reaction mixture obtained in the main reaction space is subjected to pre-treatment, getting it returned for re-processing in this reaction space a concentrated solution of carbamate and urea solution, which is then treated and purified together with the reaction mixture obtained in the additional reaction space, the section of the separation and selection of urea. The output from this last section will get diluted urethane solution and essentially pure urea solution.

In known processes for obtaining urea for m is tsya only essentially pure carbon dioxide and ammonia, and diluted urethane solution is subjected to the second processing exclusively in the main reaction space, which must be capable of conversion into urea total carbamate obtained in behind him cleaning sections.

Meet essentially all of the above requirements, these known methods have a relatively low average output value, limited by the low output value of the main reactor, and have a number of technological limitations associated with the large quantity of the solution is returned to the main reactor, and the need to install additional reactor with large size and high cost.

A large amount of water contained in the returned to the main reactor solution, despite the high yield reactions in an additional reaction space, determines the upper limit obtained on the installation of a weighted average of output and limits the possibility of reducing energy consumption and consumption of high-pressure steam.

In the European application EP 0544056 and EP 0624571 describes how the industrial synthesis of urea in new facilities, which are well cleaned ammonia and carbon from the Mat from the section selection urea is fed into the second reaction space, where is his interaction with the unreacted part of the ammonia and carbon dioxide. However, in EP 0544056 or in EP 0624571 not equal and it does not solve the problem of modernization of existing plants for urea, including equipment for desorption designed to handle containing urea reaction mixture, which improves the performance of the installation and at the same time provides a high weighted average output value.

Summary of the invention

The technical problem whose solution is proposed in the present invention is to develop a feasible method of modernization of the equipment for production of urea, which can eliminate the disadvantages inherent in the above-mentioned known systems.

In accordance with the first variant of the present invention this problem is solved by the upgrade installation of the type specified above, characterized in that it provides advanced stage:

installation of the second reactor synthesis of urea before equipment for desorption;

connection of this second reactor with the specified equipment for desorption;

- UFOs in the partition selection urea.

When developing the present invention it has been unexpectedly found that there is a possibility of further reduction of steam consumption and further simplify the installation on which the above method, due to the receipt of urea in providing high output conditions in the main reaction space (where you get a basic quantity of the finished product) and receiving urea at low output in the secondary reactor (which receive a smaller portion of the final product).

In accordance with the present invention the above conditions, providing a high yield of the reaction is mainly the reaction space, can be created by feeding it pure reagents and only concentrated urethane solution obtained after surgery partial removal (partial decomposition of carbamate and partial separation of free ammonia and condensation) of the reaction mixture taken from the main reaction space.

The principal difference obtained after the upgrade offer in the invention by the installation method from the known installations is that the proposed installation is diluted urethane solution, taken from sec, exposed after recycling reprocessing only and exclusively in the additional reaction space.

Due to the large water content in the recirculating solution in the additional reaction space are conditions of low output, and the number obtained in this space, the final product is a small part of the total number received at the installation of urea.

In accordance with another variant of the present invention the above problem is solved by the upgrade installation of the type specified above, characterized in that it provides advanced stage:

installation of the second reactor synthesis of urea, set up equipment for desorption;

- installation of equipment for the recycling of the second reactor of the second urethane solution obtained in section selection urea;

connection of this second reactor equipment for distillation, in which the second reaction mixture is taken from the second reactor, is subjected to processing, consisting in a partial decomposition of carbamate and partial separation of free ammonia in aqueous solution;

- installation of equipment and;

connection of equipment for distillation with section selection urea.

Embodiments of the invention

In accordance with the first variant of the present invention, the reaction is basically the reaction space occurs under the following conditions:

the molar ratio of NH3/CO2: 2,8-3,4, preferably 3,0;

the molar ratio of H2O/CO2: 0,1-0,25, preferably 0,18;

the reaction temperature: 180-195oC, preferably 190oC;

pressure: 140-155 bar, preferably 145 bar;

the degree of conversion of CO2: 69-71%.

The molar ratio between ammonia and carbon dioxide less than 4 and preferably equal to 3, you can reduce the volume of the reaction space with a large output and reduces the amount of heat for preheating of the reactants to the reaction temperature.

The fusion reaction in the additional reaction space occurs under the following conditions:

the molar ratio of NH3/CO2: 4,2-4,6, preferably 4,5;

the molar ratio of H2O/CO2: 1,2-1,6, preferably 1,5;

the reaction temperature: 180-192oC, preferably 190oC;

pressure: 140-155 bar, prefer the e l e C taken from the additional reaction space is subjected to partial purification (partial decomposition of carbamate and partial separation of free ammonia in aqueous solution) together with the reaction mixture taken from the main reaction space. Purification of the reaction mixture is expediently carried out at a temperature of from 180 to 192oC on entry to and from 165 to 170oC on output, and at a pressure essentially equal to the pressure in the main reaction space (140-155 bar), using as a Stripping agent is carbon dioxide. Preferably only a partial condensation obtained in the desorption process flow in the form of vapour of ammonia and carbon dioxide. The remaining part of the flow of vapors of ammonia and carbon dioxide are served in the additional reaction space, thus supporting the molar ratio between ammonia and carbon dioxide in the above limits and providing in the reaction space required heat balance. If necessary, the molar ratio between ammonia and carbon dioxide in an additional reaction space can be maintained at an optimum level by filing in this space preferred option to maintain the molar ratio between ammonia and carbon dioxide within the specified limits and create the conditions for thermal equilibrium above the stream remaining neskondensirovannyh ammonia and carbon dioxide can also partially be served in the main reaction space.

In another embodiment of the present invention taken from the additional reaction space, the reaction mixture before it is fed into the desorption pre-distil. Due to this decrease the amount of liquid undergoing desorption and partial purification, and reduces the cost required for such heat treatment. As a result of this distillation of the reaction mixture receive a stream of vapors of ammonia and carbon dioxide, which returns in extra of the reaction space to maintain it within the specified limits molar ratio between ammonia and carbon dioxide and the necessary heat balance. Preferably the distillation of the reaction mixture taken from the additional reaction space, performed in any well known manner at a pressure essentially equal to the pressure in the additional reaction space.

In accordance with the present invention the reaction of conversion of carbamate to urea in the additional reaction region should be carried out under pressure, or essentially equal to the pressure in the main reaction space, or less of this pressure 4-8 bar.

In the first case, ammonia, carbon dioxide and VM solution taken from the section selection urea, and return to liquid form in the additional reaction space. In the latter case, the pair taken from the top of the main reaction space, can be submitted in the additional reaction space using them to maintain this space at the required level the molar ratio between ammonia and carbon dioxide.

The invention also allows a certain way to simplify the whole installation for producing urea, because it does not require the placement of additional reaction space above the main reaction space.

In another embodiment of the present invention, the purification of the reaction mixture occurs at a pressure essentially equal to the pressure in the main reaction space, preferably at a pressure of 150 bar) in the so-called Isobaric conditions or conditions "imageservlet". In this embodiment, the fusion reaction in the first reaction space occurs under the following conditions:

the molar ratio of NH3/CO2: 3,0-3,4, preferably 3,2;

the molar ratio of H2O/CO2: 0,08-0,2, preferably 0,1;

the reaction temperature: 185-195oC, preference is CLASS="ptx2">

The molar ratio between ammonia and carbon dioxide less than 4 and preferably equal to 3.2, you can reduce the volume of the reaction space with a large output and reduces the amount of heat required for preheating the reactants to the reaction temperature.

Imagesarray the reaction mixture is carried out at a temperature of from 190 to 210oC.

The fusion reaction in the additional reaction space occurs under the following conditions:

the molar ratio of NH3/CO2: 4,2-4,6, preferably 4,5;

the molar ratio of H2O/CO2: 1.0 to 1.5, preferably 1,3;

the reaction temperature: 185-195oC, preferably 190oC;

pressure: 145-155 bar, preferably 150 bar;

the degree of conversion of CO2: 58-62%.

In this embodiment of the invention the reaction mixture is taken from the additional reaction space is subjected to partial purification (partial decomposition of carbamate and partial separation of free ammonia in aqueous solution) together with the reaction mixture taken from the main reaction space.

Offer in this embodiment of the invention, the method also provides for partial condensation puchase vapors of ammonia and carbon dioxide are served in the additional reaction space, supporting due to this, in the same molar ratio between ammonia and carbon dioxide in this space and providing required for the synthesis reaction heat balance. In this embodiment, moreover, taken from the top of the main reaction space vapor stream (consisting of vapors of ammonia, carbon dioxide and water) is subjected together with the reaction mixture Isobaric desorption, and the stream taken from the top of the additional reaction space, is fed directly to the section selection urea.

Similarly to the above variant of the invention the reaction of conversion of carbamate to urea in the additional reaction space in this embodiment is performed at a pressure, or essentially equal to the pressure in the main reaction space, or less 4-8 bar.

Preferably the distillation of the reaction mixture taken from the additional reaction space, carried out at a pressure of from 135 to 155 bar, preferably 150 bar and at a temperature of from 190 to 210oC on conventional equipment well known methods.

This variant of the invention also reduces the amount of liquid exposed in deso accordance with another object of the present invention, the above technical problem is solved by using made as a result of modernization as described above setup, including:

the first synthesis reactor urea;

- equipment for desorption, in which the reaction mixture is taken from the first reactor, is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the first mixture;

- equipment for at least partial condensation of the vapors taken from the equipment for desorption and recycling of the first urethane solution in the first reactor;

the second reactor for the synthesis of urea, located parallel to the first reactor;

section selection, in which the urea is obtained in the first and second reactors is separated from the second aqueous solution of carbamate;

- equipment for recycling the second solution of the carbamate obtained in the reaction space, in the second reactor;

- equipment for feeding the second reaction mixture taken from the second reactor, in the equipment for desorption.

In accordance with another variant of the invention, the above device for producing urea includes:

the first synthesis reactor urea;

- equipment for desorption, in which the first reaction mixture, oturai the division of free ammonia in aqueous solution, contained in the first mixture;

- equipment for at least partial condensation of the vapors taken from the equipment for desorption and recycling of the first urethane solution in the first reactor;

the second reactor for the synthesis of urea, located parallel to the first reactor;

section selection, in which the urea is obtained in the first and second reactors is separated from the second aqueous solution of carbamate;

- equipment for recycling the second solution of the carbamate obtained in section selection in the second reactor;

the distiller, in which the second reaction mixture is taken from the second reactor, is subjected to a treatment consisting in the partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the second mixture;

- equipment for recycling vapors taken from the distiller, in the second reactor.

In accordance with the present invention installed to carry out the proposed method of producing urea can be made in the form of new facilities or upgrading existing facilities, with a simultaneous increase their productivity and improve parameters related to potraviny below in the description of preferred, but do not limit the invention to the examples of its execution, which are shown in the appended drawings.

Brief description of drawings

In Fig. 1 shows a process scheme of the known installation for obtaining urea, working in the so-called method of desorption of CO2.

In Fig. 2 schematically shows the first option proposed in the present invention is installed, representing either a new installation or an upgraded installation according to Fig. 1.

In Fig. 3 schematically shows the second option proposed in the present invention is installed, representing either a new installation or an upgraded installation according to Fig. 1.

In Fig. 4 schematically shows a third option proposed in the present invention is installed, representing either a new installation or an upgraded installation according to Fig. 1.

In Fig. 5 shows the process scheme of the known installation for obtaining urea, working on the way Isobaric desorption (imagesarray).

In Fig. 6 schematically shows a fourth option proposed in the present invention is installed, representing either a new installation or mod the present invention installed, representing either a new installation or an upgraded installation according to Fig. 5.

In Fig. 8 schematically shows a sixth variant proposed in this invention installed, representing either a new installation or an upgraded installation according to Fig. 5.

For simplicity, in the description below and the drawings, various well-known thoroughfare, connecting with each other separate devices considered plants, are referred to and indicated on the drawings only as needed.

In Fig. 1 position 1 is the technological scheme of the known installation for obtaining urea, working in the so-called method of desorption of CO2. Installation 1 consists of sections 2 synthesis and section 3 cleaning and screening the resulting urea and contains a number of apparatuses, as described in detail below, at low pressure or under vacuum. Section 2 of the synthesis consists of series connected reactor R-1 for the synthesis of urea (which is formed corresponding to the reaction space), operating at high pressure desorber 4, intended for the partial decomposition of carbamate and partial allocation of free ammonia in aqueous solution, desorbtsiya formed in desorber vapor supplied to him by ammonia and a solution of carbamate, taken from section 3. The reactor R-1 is connected at its bottom by a pipe 6 with desorber 4, which are formed in the vapor phase (including ammonia, carbon dioxide and water vapor), which is line 7 is fed to the carbamate condenser 5, and the liquid phase (containing partially purified urea solution, which is supplied by pipeline 14 in section 3 cleaning and screening the resulting urea. The upper part of the reactor R-1 is connected by a pipe 31 with the scrubber 8, in which flowing from the reactor R-1 pair (consisting mainly of ammonia, carbon dioxide and water vapor) are absorbed supplied from sections 3 through the pipeline 9 diluted recycled carbamate. Marked in positions 10 and 11 of the centrifugal compressor and the high pressure pump is designed to feed the pipes 30a and 30b, respectively, of carbon dioxide in desorber 4 and ammonia in the condenser 5. Connected to the capacitor 5 carbamate ejector 12 provides flow to the condenser 5 or recirculating solution of carbamate supplied to the ejector from the scrubber 8 pipeline 9a, or an aqueous solution of carbamate, which is supplied to the ejector from the bottom of the reactor R-1. The pipe 13 connecting the condensate is regulating the carbamate and the source of ammonia and carbon dioxide. As mentioned above, the pipeline 14 in section 3 arrives obtained in section 2 synthesis of partially purified urea solution. In section 3 purification and selection of the resulting urea has the distiller 15 low pressure (operating at a pressure of 3-4 bar) connected via a collection of 18 of the urea solution with two serially fitted normal vacuum distillers 16, 17. Obtained in section 3 purified urea is withdrawn from the unit through the pipeline 19 and fed to further processing, which uses conventional not shown in the diagram equipment. Ammonia vapors in pipes 20 and 21 are received in the section 22 of the vacuum condensing and condensed in the usual way in it. The resulting condensate, which contains some amount of residual ammonia, is fed to further processing through the pipeline 23. Taken from the distiller 15 pairs are mixed with those obtained in section 22 of dilute solution of ammonia and form after condensation in the mixer 24 diluted urethane solution pump 25 high pressure pipe 9 is applied to the above scrubber 8.

The following are some shown in Fig. 2-4 ve installation 1. The elements of these installation options 1, which by design or on purpose do not differ from those in the above setup, indicated in Fig. 2-4 the same positions as in Fig. 1, and further description of the options for new installations will not be considered. It is also necessary to emphasize that the distinctive characteristic of the present invention is that described below installation options 1 can be represented as first created installation and setup, which is the modernization of existing facilities, as further explained below.

In accordance with the present invention shown in Fig. 2 section 2 synthesis in parallel to the reactor R-1 is the second reactor R-2 synthesis of urea. According to the fundamental idea of the invention, the reactor R-1 with respect to output and the amount of urea operates as the main reactor, and the reactor R-2 works as an additional reactor with a smaller output and a smaller amount of urea and is designed to produce urea from flowing from section 3 purification and selection of diluted urea urethane solution. In this regard, the unit 1 is provided with the appropriate equipment is yuushi a dilute solution of carbamate.

In accordance with another feature of the present invention, the additional reactor R-2 (which is formed corresponding to the reaction space) is connected by a pipe 27 with desorber 4, in which there is a partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the reaction mixture taken from the reactor R-1 and R-2. Connection of additional reactor R-2 pipe 27 with the outlet 6A of the pipe 6 can significantly simplify the whole setup diagram. To maintain the appropriate level of molar ratio of NH3/CO2and create the necessary heat balance reactions in primary and secondary reactors R-1 and R-2 uses taps 28a and 28b of the pipe 28, which in the reactors fed the remaining vapor in the condenser 5 of the carbamate portion of the ammonia and carbon dioxide. To maintain the appropriate level of molar ratio of NH3/CO2and create the necessary heat balance in the additional reactor R-2 you can also use part of the source of ammonia, feeding it to the reactor through pipe 26, connected by a pipe 29 with the pipe 30b, in which the source of ammonia todaysenator R-2 is located relative to the earth at a higher level, than the lower part of the main reactor R-1, resulting in easier flow into the reactor R-2 pipeline 28b of the capacitor 5 carbamate neskondensirovannyh rich in ammonia vapor. Pairs taken from the upper part of the additional reactor R-2, go through the pipe 32 into the scrubber 8.

As noted above, is shown in Fig. 2 installation 1 represents either a new installation or an upgraded accordingly an existing installation, in particular a streamlined installation process scheme is shown in Fig. 1.

The preferred option upgrade Fig. 1 provides for the implementation of the following stages:

- extra reactor R-2 before desorber 4 parallel to the existing reactor R-1;

connection of reactor R-2 desorber pipeline 27;

- installation of the pipeline 26 for recirculation to the reactor R-2 diluted urethane solution obtained in section 3 and taken out of the scrubber 8.

In a variant of the installation according to Fig. 2 additional reactor R-2 is preferably mounted so that its lower part was located on the ground level wasexactly installation also provides for the installation of the pipeline 28b for recirculation to the reactor R-2-rich ammonia neskondensirovannyh vapors from the condenser 5 carbamate and installation of the pipeline 32, which is taken from the top of the reactor R-2 pair arrive in the scrubber 8.

In another embodiment of the invention section 2 of the synthesis of the proposed facility 1, as shown in Fig. 3, contains the distiller 35, in which the distillation flowing through the pipe 27 from the reactor R-2 reaction mixture and in which is formed a flow rich in ammonia vapor, which is returned to the reactor R-2 to line 36. Distiller 35 is connected to desorber 4 pipe 37, which partially purified in the distillation of the reaction mixture enters desorber. In this installation option, in addition, to improve the efficiency of the distillation neskondensirovannyh rich in ammonia vapors from the condenser 5 carbamate serves to drain 28b of the pipeline 28 is not in the reactor R-2, and in the distiller 35. The availability of distiller 35 can reduce the amount of liquid reaction mixture obtained in the reactor R-2) supplied to desorber 4, and to thereby reduce thermal load on him. The presence of the distiller is most effective when it is necessary to upgrade an existing installation is running at full capacity by decorarea.

Option installation 1 according to Fig. 4 the lower part of the additional researchability in the typically complex and expensive mounting the lift to the reactor R-2. In this embodiment, installation of the additional pressure of the reaction space for 4-8 bar less than the pressure in the existing main reaction space. When this molar ratio of NH3/CO2and heat balance in the additional reactor R-2 is supported at the required level not at the expense neskondensirovannyh vapor taken from the condenser 5 carbamate, and feed it through the pipeline 33 vapors from the top of the main reactor R-1. In this scheme, the pipe 28 passes only between the carbamate condenser 5 and the main reactor R-1. Low pressure synthesis reactor R-2 determines whether installation in the pipe 27 at the entrance to desorber 4 pump 34 which pumps the reaction mixture from reactor R-2 desorber.

Below is shown in Fig. 5 scheme of the known installation for obtaining urea according to the method of Isobaric desorption (imagesarray). Those elements of the unit 1, which in its design or in its purpose no different from those in the above settings, indicated in Fig. 5 the same positions as in Fig. 1-4, and further will not be considered.

In section 2 of the synthesis shown in Fig. 5 installation 1 though it directly into the reactor R-1, and ammonia is fed into the collector 38, which is an integral part of section 3 selection produced urea. To do this, the unit 1 is used pipes 39, 40, connecting the centrifugal compressor and the high pressure pump (not shown) reactor R-1 and the collector 38. In section 2 there is also mounted behind the condenser 5 carbamate separator 41, designed to separate neskondensirovannyh in the condenser 5 vapors, including ammonia, carbon dioxide and water vapor, from urethane solution is returned to the reactor R-1 via line 42, which is connected to the ejector 43. A pair of separator 41 is disposed on the pipe 44 into the distiller 45 medium pressure (pressure of about 18 bar), which is established in section 3 selection directly behind desorber 4. Section 3 in addition to the above the distiller 45 medium pressure, the distiller 15 low pressure and vacuum stills 16,17 there distillation column 46, designed to separate essentially pure ammonia from dilute urethane solution, which is returned back to the reactor R-1. Diluted urethane solution taken from the bottom of the distillation column 46, the pipe 47 is pumped by pump 4 is the PR 49, and liquid ammonia by pipeline 50 enters the collector 38. This ammonia together with fresh ammonia is pumped into the reactor R-1 is connected to the ejector 43 pipeline 53, running the pumps 51, 52. The pump 51 is connected with the pipe 54, through which the column 46 rectification served ammonium phlegm. In the distillation column 46 is rectification diluted urethane solution obtained by condensation in the respective capacitors 55 and 56 vapors taken from the top of the distillers 45 and 15 low and medium pressure. In section 3 also has a capacity of 57, which gathers formed in the capacitor 56 diluted urethane solution, which pump 58 is pumped from this tank to the column 46.

Below is shown in Fig. 6-8 some alternatives proposed in the present invention installations, which are based on the scheme described above installation 1 according to Fig. 5.

In the variant shown in Fig. 6, section 2 of the synthesis setup 1 contains the second reactor R-2 synthesis of urea, installed parallel to the reactor R-1. Similarly to the above versions of the invention the reactor R-1 operates as the main reactor as part of the and reduced performance and is suitable for conversion into urea diluted urethane solution, supplied from sections 3 purification and selection urea.

The installation 1 also has a corresponding device designed in this case in the form of a pipe 66 to pump from the bottom of the column 46 in the advanced reactor R-2 pump 48 diluted urethane solution. Additional reactor R-2 is connected by a pipe 59 with desorber 4, in which there is a partial decomposition of carbamate and partial separation of free ammonia contained in the reaction mixtures taken from the reactors R-1 and R-2. To maintain the required level of molar ratio of NH3/CO2and heat balance in the additional reactor R-2 in the reactor by pipe 44 from the condenser 5 carbamate served neskondensirovannyh rich in ammonia fumes. In this embodiment of the invention a pair taken from the top of the additional reactor R-2, the pipe 60 are fed into the distiller 45 medium pressure. The bottom of the additional reactor R-2 is preferably positioned relative to the ground level above the bottom of the main reactor R-1, thereby facilitating the flow in the reactor R-2 neskondensirovannyh vapors from separator 41.

1, a schematic of which is shown in Fig. 6 may Ave the R installation the scheme which is shown in Fig. 5, the ongoing implementation of a number of mounting operations similar to those mentioned in the description, as shown in Fig. 2.

The suggested installation 1 according to Fig. 7 additional reactor R-2 is mounted below the main reactor R-1 or on the same level, the pressure in the additional reaction space for 4-8 bar below the pressure in the main reaction space. Under reduced pressure in the secondary reactor R-2 is taken from him, the reaction mixture is pumped into desorber 4 pipeline 59 installed before desorber pump 61. The operation of the additional reactor R-2, lower than in the main reactor R-1, the pressure in this case can simplify the design of the installation 1 and to reduce the cost of its manufacture (or modernization).

In one proposed in the invention and shown in Fig. 8 installation option 1 in section 2 of the synthesis include a distiller 62, in which the distillation flowing through the pipeline 62 of the reactor R-2 reaction mixture and the formed rich in ammonia vapors that the pipe 64 is returned to the reactor R-2. Distiller 62 in turn is connected to distillate mixture. In this installation the end of the pipe 65 is also used to feed distiller 45 average pressure of the reaction mixture from the connected with desorber 4 of the pipeline 14. The availability of distiller 62 can reduce the amount of liquid reaction mixture obtained in the reactor R-2) supplied to desorber 4, and to reduce due to this, its thermal load. The greatest effect from the use of this distiller can be obtained by upgrading an existing installation is running at full capacity by desorber.

1. The way of modernization of the plant for producing urea, containing the first reactor synthesis of urea R-1, the second reactor synthesis of urea R-2, equipment 4 for desorption, in which the reaction mixture is taken from the first reactor R-1 is processed, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the first mixture; equipment 5 for at least partial condensation of the vapors taken from the equipment 4 for desorption, and return the first urethane solution in the first reactor R-1; section 3 selection urea, in which the urea is obtained in the first reactor R-1 is separated from reactor R-2 synthesis of urea to equipment 4 for desorption, the connection of the second reactor R-2 equipment 4 for desorption, installation of equipment 9, 25, 26, 47, 48, 66 to return to the second reactor R-2 of the second urethane solution obtained in section 3 selection urea.

2. The method according to p. 1, characterized in that the bottom of the second reactor R-2 is above the bottom of the first reactor R-1.

3. The method according to p. 1, characterized in that it further includes the step of installing equipment 28a, 28b, 44 to return neskondensirovannyh fumes from equipment 4 for desorption in the second reactor R-2.

4. The method according to p. 1, characterized in that it further includes the step of installing equipment 8, 26 for condensing vapors taken from the top of the first R-1 and/or the second R-2 reactor, and to return the resulting solution in the second reactor R-2.

5. The method according to p. 1, characterized in that it further includes the step of installing a pipe 33 to return to the second reactor R-2 vapor taken from the top of the first reactor R-1.

6. The method according to p. 1, characterized in that it further includes the step of installing a pipe 60 for supplying vapor taken from the top of the second reactor R-2, in section 3 selection urea.

7. The method according to p. 1, characterized in that Y, in which the second reaction mixture is taken from the second reactor R-2, treated, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the second mixture; installation of equipment 36 to return the vapors taken from the equipment for distillation, in the second reactor R-2; the connection equipment 35 distillation equipment 4 for desorption.

8. The method according to p. 7, characterized in that it further includes the step of installing equipment 28b for recycling neskondensirovannyh fumes from equipment 4 for desorption in the equipment for distillation 35.

9. The method according to p. 1, characterized in that it further includes a step of connection of the top of the second reactor R-2 with distiller 45 medium pressure, which is present in section 3 selection urea.

10. The way of modernization of the plant for producing urea, containing the first reactor synthesis of urea R-1, the second reactor synthesis of urea R-2, equipment 4 for desorption, in which the reaction mixture is taken from the first reactor R-1 is processed, consisting of partial decomposition of carbamate and partial separation of free ammonia in water is uraemic of equipment 4 for desorption, and return the first urethane solution in the first reactor R-1; section 3 selection of urea, in which the urea is obtained in the first reactor R-1 is separated from the second aqueous urethane solution, characterized in that it comprises the following stages: installation of the second reactor R-2 synthesis of urea to equipment 4 for desorption, equipment installation, 47, 48, 66 to return to the second reactor R-2 of the second urethane solution obtained in section 3 selection urea, the connection of the second reactor R-2 equipment 62 to distillation to process selected from the second reactor R-2 reaction mixture, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the second mixture, the installation of equipment 64 to return vapor from the equipment 62 for distillation in the second reactor R-2, connection equipment 62 for distillation with section 3 selection urea.

11. The method according to p. 10, characterized in that it further includes the step of installing equipment 44 for returning vapors from equipment 4 for desorption in the second reactor R-2.

12. The method according to p. 10, characterized in that it further includes the step of installing a pipe 60 for supplying steam the VA urea, including the first reactor synthesis of urea R-1, the second reactor synthesis of urea R-2, located parallel to the first reactor R-1 equipment 4 for desorption, in which the reaction mixture is taken from the first reactor R-1 is processed, consisting of partial decomposition of carbamate and partial separation of free ammonia in aqueous solution contained in the first mixture; equipment 5 for at least partial condensation of the vapors taken from the equipment 4 for desorption, and return the first urethane solution in the first reactor R-1; section 3 selection urea, in which the urea is obtained in the first R-1 and the second R-2 reactor, is separated from the second aqueous urethane solution, characterized in that it further contains equipment 9, 25, 26, 47, 48, 66 to return to the second reactor R-2 of the second urethane solution obtained in section 3 selection urea, equipment, 27, 34, 37, 59, 61 for supplying the second reaction mixture from the second reactor R-2 equipment 4 for desorption, where it can be processed together with the first reaction mixture from the first reactor.

14. Installation according to p. 13, characterized in that it also contains equipment 10, 30A for flow of ishodnogo reactor R-2 is above the bottom of the first reactor R-1.

16. Installation according to p. 13, characterized in that it also contains equipment 28a, 28b, 44 for recirculation neskondensirovannyh fumes from equipment 4 for desorption in the first R-1 and/or second reactor R-2.

17. Installation according to p. 13, characterized in that it also contains equipment 8, 26 for condensing vapors taken from the top of the first R-1 and/or the second reactor R-2, and return the resulting solution in the second reactor R-2.

18. Installation according to p. 13, characterized in that it also contains at least one conduit 33 to return to the second reactor R-2 vapor taken from the top of the first reactor R-1.

19. Installation according to p. 13, characterized in that it also contains at least one conduit 60 for supplying section 3 selection urea vapor taken from the top of the second reactor R-2.

20. Device for producing urea, comprising a first reactor for the synthesis of urea R-1, the second reactor R-2 synthesis of urea, located parallel to the first reactor R-1 equipment 4 for desorption, in which the reaction mixture is taken from the first reactor R-1 is processed, consisting of partial decomposition of carbamate and partial separation of free AMIA the ditch, taken from equipment 4 for desorption, and return the first urethane solution in the first reactor R-1; section 3 selection of urea, in which the urea is obtained in the first R-1 and the second R-2 reactor, is separated from the second aqueous urethane solution, characterized in that it further contains equipment 9, 25, 26, 47, 48, 66 for recycling to the second reactor R-2 of the second urethane solution obtained in section 3 selection urea, equipment 35, 62 distillation selected from the second reactor R-2 reaction mixture with obtaining a flow comprising ammonia and carbon dioxide in vapor phase and partially purified reaction mixture, equipment 36, 64 to return to the second reactor R-2 flow comprising ammonia and carbon dioxide in vapour phase.

21. Installation according to p. 20, characterized in that it also contains equipment 65 for feeding partially purified reaction mixture of equipment 62 distillation section 3 selection urea.

22. Installation according to p. 20, characterized in that it also contains equipment 37 for supplying partially purified reaction mixture of equipment 35 distillation equipment 4 for desorption.

23. Installation according to p. 20, characterized in that it also includes the R-2.

24. Installation according to p. 20, characterized in that it also contains equipment 28b to return neskondensirovannyh fumes from equipment 4 for desorption in the equipment for distillation 35.

25. Installation according to p. 20, characterized in that it also contains a pipe 60 for supplying vapor taken from the top of the second reactor R-2, in section 3 selection urea.

26. Installation according to p. 20, characterized in that it also contains equipment 8 for condensing vapors taken from the top of the first R-1 and/or the second R-2 reactor, and returning the resulting solution in the second reactor R-2.

 

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