Method of producing carbamide

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing carbamide from ammonia and carbon dioxide at high temperature and pressure, molar ratio NH3:CO2=(3.4-3.7):1. The method is carried out in a carbamide synthesis reactor from which gases and a carbamide synthesis liquid melt are separately output, followed by separation of excess ammonia from the carbamide synthesis melt at pressure of 9-12 MPa, two-step distillation of the melt, condensation of distillation gases to form recyclable ammonium carbonate solutions. Distillation at the first step is carried out at pressure of 9-12 MPa in a current of carbon dioxide. After distillation, the melt is fed into the second distillation step, which is carried out at low pressure. Gases from the first distillation step are condensed in two successive areas at pressure of the first distillation step into which gases output from the synthesis reactor and excess ammonia from the separation step are also fed. In the first area, condensation is carried out while feeding a portion of the ammonium carbonate solution obtained from condensation of gases from the second distillation step, and the condensed vapour is cooled by a condensate which boils at excess pressure to obtain vapour. In the second condensation area 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. The formed ammonium carbonate solution is fed into the second condensation area and the ammonium carbonate solution coming out of the second condensation area is fed into the reactor. Distillation at the first step is carried out in a current of carbon dioxide which is used in amount of 35-40% of the total amount thereof fed into the process; 75-85% of gases separated at the separation step are fed into the first condensation area for distillation gases from the first step, and the remaining amount of gases separated at the separation step, along with gases output from the synthesis reactor, is fed into the second condensation area for distillation gases from the first step.

EFFECT: producing vapour with parameters which enable use thereof in the next steps of the carbamide synthesis process in the first condensation area of gases from the first distillation step.

1 dwg, 1 tbl, 2 ex

 

The invention relates to a process for the production of urea from ammonia and carbon dioxide.

A known method of producing urea, including the interaction of ammonia and carbon dioxide in the synthesis reactor at elevated temperature (160-190C) and pressure (12.5 to 20 MPa, a molar ratio of NH3:CO2=(1.5-to 3.5):1 (preferably 2,1:1) forming a reaction mixture containing urea, ammonium carbamate (hereinafter referred to carbamate and free ammonia in aqueous solution, separation output gases and liquid water synthesis of urea from the synthesis reactor, the subsequent filing of AA synthesis of urea stripper partial decomposition of carbamate and partial allocation of free ammonia in the current source of carbon dioxide (preferably 25-75% of its total amount introduced into the process at a pressure of from 1 MPa to a pressure in the synthesis reactor to obtain a gas stream comprising ammonia and carbon dioxide, and a liquid flow comprising urea and residual carbamate in aqueous solution, the feed liquid stream from the stripper on stage subsequent decomposition of the carbamate, the separation of ammonia and carbon dioxide and excretion of urea, the feed gas stream from the stripper on stage partial absorption-condensation, the flow generated at this stage of the liquid flow in the synthesis reactor (SU 190290, C07C 127/04, reissue 194).

As a result of using this method is a slight excess of ammonia conversion rate of carbon dioxide in the urea and the specific productivity of the reactor is low, resulting in significant capital cost of construction and to the large-scale recycling, require a high energy level 0,217 ton of fuel equivalent per tonne) for the production of 1 ton of urea.

A known method of producing urea from ammonia and carbon dioxide at elevated temperature and pressure, the molar ratio of NH3:CO2=(3.6V-6.0V):1, in the reactor for the synthesis of urea with the subsequent release of excess ammonia from Plava synthesis of urea separation at a pressure of 6 to 12 MPa, a two-stage distillation of the solvent, the condensation of the gases of distillation with the formation of recycled solutions of ammonium salts (UAS), and the first distillation stage is carried out at a pressure of 6 to 12 MPa in the current CO2(~70% of the total quantity that you enter in the process), the water after distillation is passed to the second stage of distillation, which is carried out at low pressure, the gases of distillation first stage condense in two successive zones at a pressure of the first distillation stage, and in both zones condensable vapors are cooled condensation, boiling under pressure, steam, used after the respective stages of the process; the condensation in the first zone is carried out with excess CO2in the gas phase and the introduction of a solution of UAS obtained when the absorption-condensation of the gases of distillation of the second stage, the second condensation zone serves the separated ammonia solution UAS, leaving the second zone of condensation, is sent to the reactor, mixing before recirculation of liquid ammonia, and not condensed gases are subjected to water absorption-condensation together with the gases of the second distillation stage (SU 692257, C07C 126/02, 1984).

This known method, due to the combination of high molar ratio of NH3:CO2at the stage of synthesis with the holding of the first distillation stage at a pressure not as low as 1 MPa, but not as high as the pressure of the synthesis, allows to minimize the cost of energy resources. As indicated in the description of this method, its implementation, the total specific energy consumption for production of 1 ton of urea are 0,166 equivalent per tonne and significantly lower cost by other known methods. However, provided in a known manner the conditions of the condensation of gases from the distillation of the first degree in two successive zones provide a relatively low completeness of their condensation at a pressure of 6-12 MPa: as the process of condensation at constant temperature and increasing con is entrale of ammonium carbamate formed in the solution UAS increases the equilibrium vapor pressure above the solution. Therefore, in the second condensation zone, cooled the same way as the first, condensation, boiling under pressure, the degree of condensation is low. Not condensed at this stage, the gases are subjected to condensation in the low pressure stage. Thus, according to the example from the description of this known method, the total quantity of gas allocated at a pressure of 9 MPa, is 107900 kg/h, and of this amount, a step of low pressure passed 34900 kg/h (32%). This leads to the production of large quantities of dilute solution of UAS that before recycling it is necessary to concentrate, which requires additional energy costs. For this reason, the technical potential of the above combinations of conditions of synthesis and distillation of the first stage is not fully used.

The closest to the invention is a method of obtaining urea from ammonia and carbon dioxide at elevated temperature and pressure, the molar ratio of NH3:CO2=(3,4-3,7):1, in the reactor for the synthesis of urea with separate output from the gas and liquid melt synthesis of urea, with the subsequent release of excess ammonia from Plava synthesis of urea separation at a pressure of 8.12 MPa, a two-stage distillation of the solvent, the condensation of the gases of distillation with the formation of recycled solutions UAS, and the distillation of the first article the penalty is carried out at a pressure of 8.12 MPa in the current CO 2used at 30-35% of the total quantity that you enter in the process, the melt after distillation is passed to the second stage of distillation, which is carried out at low pressure, the gases of distillation first stage condense in two successive zones at a pressure of the first distillation stage, while in the first zone, the condensation is carried out at the introduction part of the solution UAS obtained by condensation of the gases of the second distillation stage, and condensable vapors are cooled condensation, boiling under pressure, steam, gases, derived from the synthesis reactor, together with excess ammonia allocated for phase separation, is introduced into the first condensation zone gases from the distillation of the first stage, in the second zone to the condensation of gases from the distillation of the first stage of condensable vapors are cooled by the circulating water, and not condensed gases at the same pressure washed with another portion of the solution of ammonium salt, obtained by condensation of the gases of distillation of the second stage, and the resulting solution of ammonium salts is injected into the second condensation zone, and a solution of ammonium salts, leaving the second zone of condensation, is sent to the reactor (EN 2454403, C07C 273/04, 2012).

In this way, thanks to the introduction of gaseous flows from the synthesis reactor and from the zone of separation excessive AMIA is in the first condensation zone at a pressure of 8.12 MPa together with the gases of the first distillation stage, it is possible to significantly increase the degree of condensation of ammonia and carbon dioxide at this stage and accordingly increase the production of steam by condensation, and reduce the amount of gases that must be condensing at low pressure. This fact entails a reduction of energy costs in the production of urea to 0,160 equivalent per tonne on 1 ton of urea.

The disadvantage of a relatively low temperature level of the process of condensation of the gases of distillation in the first zone. From this level depend on the pressure and temperature of steam, the resulting utilization of the heat (excess pressure 0,28-0,32 MPa, a temperature of 130-135C). The possibility of using a pair of such parameters on the subsequent stages of the process is limited, because even during transport of the vapor to the place of its consumption, its parameters can be reduced below an acceptable level.

The problem posed by the present invention is in that the redistribution process streams, which would generate in the first condensation zone at a pressure 9-12 MPa pairs suitable for use in the subsequent stages of the process.

To solve this problem, a method for obtaining urea from ammonia and carbon dioxide at elevated temperature and pressure, the molar aspect] is the solution of NH 3:CO2=(3,4-3,7):1, in the reactor for the synthesis of urea from which separately remove gases and liquid water synthesis of urea, with the subsequent release of excess ammonia from Plava synthesis of urea separation at a pressure 9-12 MPa, a two-stage distillation of the solvent, the condensation of the gases of distillation with the formation of recycled solutions of ammonium salts, and the first distillation stage is carried out at a pressure 9-12 MPa in the current CO2the water after distillation is passed to the second stage of distillation, which is carried out at low pressure, the gases of distillation first stage condense in two successive zones at a pressure of the first distillation stage, where the injected gases as withdrawn from the synthesis reactor, and the excess ammonia is allocated for phase separation, while in the first zone, the condensation is carried out at the introduction part of the solution ammonium salts obtained by condensation of the gases of the second distillation stage, and condensable vapors are cooled condensation, boiling under pressure, steam, in the second zone to the condensation of gases from the distillation of the first stage of condensable vapors are cooled by the circulating water and not condensed gases at the same pressure washed with another portion of the solution of ammonium salt, obtained by condensation of the gases of distillation the second STU is EIW, and the resulting solution of ammonium salts is injected into the second condensation zone, a solution of ammonium salts, leaving the second zone of condensation, is sent to the reactor, wherein the first distillation stage is carried out in the current CO2used at 35-40% of the total quantity that you enter in the process, 75-85% of the gases evolved at the stage of separation, is introduced into the first zone of condensation of gases from the distillation of the first stage, and the rest of the quantities of gas allocated to phase separation, together with the gases withdrawn from the synthesis reactor is injected into the second zone to the condensation of gases from the distillation of the first degree.

The technical result achieved by implementation of the proposed method is the possibility of production in the first zone to the condensation of gases from the distillation of the first stage steam pressure of not lower to 0.33 MPa, which ensures its use in the later stages of production of urea. While maintaining almost the same steam flow from external sources, as in the known method, this allows you to reduce capital costs through the reduction of heat transfer surface in the apparatus condensation of gases from the distillation of the first stage and in the apparatus of the second distillation stage.

The invention is illustrated by the following examples with SS is the LCA on the technological scheme, shown in the attached figure.

EXAMPLE 1. In the synthesis reactor urea 1 serves the flow of liquid ammonia 2 (47586 kg/h) and gaseous carbon dioxide 3 (38400 kg/h)and recirculated solution of UAS 4 (145866 kg/h; ammonia 53,7, carbon dioxide 35,4, water 10,6, urea 0,2) from the second condenser high pressure 5 (molar ratio of NH3:CO2in the reactor 3,63:1). In the reactor at a pressure of 20 MPa and a temperature of 190C are formed separately derived stream 6 Plava synthesis of urea: (220000 kg/h; urea 38.5, ammonia 30,2, carbon dioxide 12,7, water 18,5; hereinafter, all compositions are given in wt.%; the content of ammonium carbamate is shown as ammonia and carbon dioxide, a product of the interaction of which he is; the content of inert impurities in the gas streams not shown) and the thread 7 is not condensed gases (ammonia 11579 kg/h). Thread 6 drossellied to a pressure of 9 MPa in the separator 8, where the at 165C is allocated gaseous stream 9 (23394 kg/h; ammonia 76,6, carbon dioxide 19,4, water of 4.0). Thread 10 of the water from the separator 8 (196607 kg/h; urea 43,1, ammonia 24,7, carbon dioxide 11,9, water 20,3; the molar ratio of NH3:CO2=2,93 - based urea) without changing the pressure supplied to the stripper 11, where when heated vapor pressure (50733 kg/h, the excess pressure of 2 MPa) and purging with carbon dioxide (flow 12; 23536 kg/h 38 per cent of the quantity, input in the process) at 165C in the lower part of the decomposition of the larger part of the ammonium carbamate and the distillation of the excess ammonia. The water is withdrawn from stripper 11 (stream 13; 141040 kg/h; urea 59,9, ammonia 7,8, carbon dioxide 7,0, water 25,1), is subjected to further processing using conventional manufacturing methods: second distillation stage at a pressure of 0.3 MPa and a temperature of 135-140C, the condensation of the selected gas in the cooling water with the formation of a dilute solution of UAS, evaporation of a solution of urea in three stages under vacuum (residual pressure of 50, 30 and 3 kPa) to a concentration of 98.5-99.5% of the subsequent pillromanian or granulation, which receive 84303 kg/h of urea. The gas flow 14 from the stripper 11 (79103 kg/h; ammonia 47,6, carbon dioxide 46,7, water 5,5, urea 0,1) together with a gas flow of 15 (18715 kg/h ammonia 14327 kg/HR, carbon dioxide 3638 kg/h, water 750 kg/h), part (80%) of the thread 9 of the separator 8, coming into the first condenser high pressure 16. In the capacitor 16 serves also part of the solution UAS obtained by condensation of the gases of the second distillation stage (stream 17; 14830 kg/h; ammonia 35,4, carbon dioxide 32,0, water 31,8, urea and 0.8). In the annular space of the condenser 16 by evaporation of the steam condensate from the tank 18, through the heat of formation of carbamate and RA is the creation of ammonia at 157C is formed 53611 kg/h of steam with a pressure of 0.33 MPa (stream 19), which is used in subsequent stages of the process. Gas-liquid mixture from the condenser 16 is supplied to the second condenser high pressure 5, which also serves the solution UAS from the absorber to the high pressure 20 (stream 21; 19980 kg/h; ammonia 45,0, carbon dioxide 27,2, water 27,0, urea and 0.7), and the gas flow 22 (4679 kg/h ammonia 3584 kg/HR, carbon dioxide 908 kg/h, water 187 kg/h), which is the rest of the gas stream 9 from the separator 8, and the gas flow 7 from the synthesis reactor 1. In the condenser 5 at 115C (cooling circulating water) condenses a large part of the gases not condensed in the condenser 16, with the formation of recirculated into the reactor 1 stream 4. A large part of the gases not condensed in the condenser 5 (thread 23; ammonia 3019 kg/h), is absorbed by another part of the solution UAS obtained by condensation of the gases of the second distillation stage (stream 24; 17000 kg/h; composition identical to the composition of the stream 17), in the absorber high pressure 20 with the formation of the thread 21 solution UAS. Not absorbed ammonia (39 kg/h) in a mixture with inert gases (stream 25; less than 2% of the total amount of gases, condensed at a pressure of 9 MPa - threads 7, 9 and 14) is sent for final absorption in the absorber low pressure 26. The number and compositions of the streams are also given in the accompanying table.

EXAMPLE 2. In the synthesis reactor urea 1 serves threads Jew is on ammonia 2 (47590 kg/h) and gaseous carbon dioxide 3 (38400 kg/h), and recirculated solution of UAS 4 (146233 kg/h; ammonia 53,7, carbon dioxide 35,5, water 10,6, urea 0,2) from the second condenser high pressure 5 (molar ratio of NH3:CO2in the reactor 3,63:1). In the reactor at a pressure of 20 MPa and a temperature of 190C are formed separately derived stream 6 Plava synthesis of urea: (220352 kg/h; urea 38.5, ammonia 30,3, carbon dioxide 12,7, water 18,5; hereinafter, all compositions are given in wt.%; the content of ammonium carbamate is shown as ammonia and carbon dioxide, a product of the interaction of which he is; the content of inert impurities in the gas streams not shown) and the thread 7 is not condensed gases (ammonia 11597 kg/h). Thread 6 drossellied to a pressure of 12 MPa in the separator 8, where the at 165C is allocated gaseous stream 9 (23550 kg/h; ammonia 76,5, carbon dioxide 19,5, water of 4.0). Thread 10 of the water from the separator 8 (196803 kg/h; urea 43,1, ammonia 24,7, carbon dioxide 11,9, water 20,3; the molar ratio of NH3:CO2=2,93 - based urea) without changing the pressure supplied to the stripper 11, where when heated vapor pressure (49533 kg/h, pressure 2 MPa) and purging with carbon dioxide (flow 12; 23536 kg/h 38% of the total number entered in the process) at 165C in the lower part of the decomposition of the larger part of the ammonium carbamate and the distillation of the excess ammonia. The water output is C the stripper 11 (stream 13; 142890 kg/h; urea 59,2, ammonia 8,5, carbon dioxide 7,4, water 24,8), is subjected to further processing using conventional manufacturing methods: second distillation stage at a pressure of 0.3 MPa and a temperature of 135-140C, the condensation of the selected gas in the cooling water with the formation of a dilute solution of UAS, evaporation of a solution of urea in three stages under vacuum (residual pressure of 50, 30 and 3 kPa) to a concentration of 98.5-99.5% of the subsequent pillromanian or granulation, which receive 84305 kg/h of urea. The gas flow 14 from the stripper 11 (77448 kg/h; ammonia 47,2, carbon dioxide 47,0, water 5,7, urea 0,1) together with a gas flow of 15 (18840 kg/h ammonia 14413 kg/HR, carbon dioxide 3674 kg/h, water 754 kg/h), part (80%) of the thread 9 of the separator 8, coming into the first condenser high pressure 16. In the capacitor 16 serves also part of the solution UAS obtained by condensation of the gases of the second distillation stage (stream 17; 13680 kg/h; ammonia 37,0, carbon dioxide 32,1, water 30,1, urea and 0.8). In the annular space of the condenser 16 by evaporation of the steam condensate from the tank 18, through the heat of formation of carbamate and dissolution of ammonia at 164C is formed 49826 kg/h of steam with a pressure of 0.35 MPa (stream 19), which is used in subsequent stages of the process. Gas-liquid mixture from the condenser mostwant second capacitor high pressure 5, also submit a solution of UAS from the absorber to the high pressure 20 (stream 21; 26891 kg/h; ammonia 53,2, carbon dioxide 23,9, water 22,4, urea and 0.6), and the gas flow 22 (4710 kg/h ammonia 3603 kg/HR, carbon dioxide 918 kg/h, water 188 kg/h), which is the rest of the gas stream 9 from the separator 8, and the gas flow 7 from the synthesis reactor 1. In the condenser 5 at 140C (cooling circulating water) condenses a large part of the gases not condensed in the condenser 16, with the formation of recirculated into the reactor 1 stream 4. A large part of the gases not condensed in the condenser 5 (thread 23; ammonia 6934 kg/h), is absorbed by another part of the solution UAS obtained by condensation of the gases of the second distillation stage (stream 24; 20000 kg/h; composition identical to the composition of the stream 17), in the absorber high pressure 20 with the formation of the thread 21 solution UAS. Not absorbed ammonia (42 kg/h) in a mixture with inert gases (stream 25; less than 2% of the total amount of gases, condensed at a pressure of 12 MPa - threads 7, 9 and 14) is sent for final absorption in the absorber low pressure 26. The number and compositions of the streams are also given in the accompanying table.

Table
The number and composition of flows examples
# threadQuantity, kg/hComposition, % wt.
NH3CO2ureawater
Example 1
247586100
338400100
414586653,735,40,210,6
622000030,2a 12.7a 38.518,5
711579100
92339476,6 19,44,0
1019660724,711,9to 43.120,3
1223536100
131410407,87,059,925,1
147910347,646,70,15,5
151871576,619,44,0
171483035,432,00,8of 31.8
1953611
211998045,027,20,727,0
22467976,619,44,0
233019100
241700035,432,00,8of 31.8
2539100
Example 2
247590100
338400100
414623353,735,50,210,6
622035230,3a 12.7a 38.518,5
711597100
92355076,519,54,0
1019680324,711,9to 43.120,3
1223536100
131428908,57,459,224,8
1477448 to 47.247,00,1the 5.7
151884076,519,54,0
171368037,032,10,830,1
1949826100
212689153,223,90,622,4
22471076,519,54,0
236934100
242000037,032,10, 30,1
2542100

A method of producing urea from ammonia and carbon dioxide at elevated temperature and pressure, the molar ratio of NH3:CO2=(3,4-3,7):1, in the reactor for the synthesis of urea from which separately remove gases and liquid water synthesis of urea, with the subsequent release of excess ammonia from Plava synthesis of urea separation at a pressure 9-12 MPa, a two-stage distillation of the solvent, the condensation of the gases of distillation with the formation of recycled solutions of ammonium salts, and the first distillation stage is carried out at a pressure 9-12 MPa in a stream of carbon dioxide, water after distillation is passed to the second stage of distillation, which is carried out at low pressure, the gases of distillation first stage condense in two successive zones at a pressure of the first distillation stage, where injected also the gases withdrawn from the synthesis reactor, and the excess ammonia is allocated for phase separation, while in the first zone, the condensation is carried out at the introduction part of the solution ammonium salts obtained by condensation of the gases of distillation of the second stage, condensing the steam is cooled by the condensate, boiling under pressure, steam, in the second zone to the condensation of gases from the distillation of the first stage of condensable vapors are cooled by the circulating water, and not condensed gases at the same pressure washed with another portion of the solution of ammonium salt, obtained by condensation of the gases of distillation of the second stage, and the resulting solution of ammonium salts is injected into the second condensation zone, a solution of ammonium salts, leaving the second zone of condensation, is sent to the reactor, wherein the first distillation stage is carried out in a current of carbon dioxide used in the amount of 35-40% of the total quantity that you enter in the process, 75-85% gases evolved at the stage of separation, is introduced into the first zone of condensation of gases from the distillation of the first stage, and the rest of the quantities of gas allocated to phase separation, together with the gases withdrawn from the synthesis reactor is injected into the second zone to the condensation of gases from the distillation of the first stage.



 

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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: 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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