CN112495323B - For CO2Medium-pressure desorption hydrolysis tower for gas stripping urea production and energy-saving production increasing method - Google Patents
For CO2Medium-pressure desorption hydrolysis tower for gas stripping urea production and energy-saving production increasing method Download PDFInfo
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- C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
- C07C273/04—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds from carbon dioxide and ammonia
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- C07C273/00—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups
- C07C273/02—Preparation of urea or its derivatives, i.e. compounds containing any of the groups, the nitrogen atoms not being part of nitro or nitroso groups of urea, its salts, complexes or addition compounds
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- B01J2219/00049—Controlling or regulating processes
- B01J2219/00051—Controlling the temperature
- B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
- B01J2219/00105—Controlling the temperature by indirect heating or cooling employing heat exchange fluids part or all of the reactants being heated or cooled outside the reactor while recycling
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- B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J2219/00049—Controlling or regulating processes
- B01J2219/00051—Controlling the temperature
- B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
- B01J2219/00117—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with two or more reactions in heat exchange with each other, such as an endothermic reaction in heat exchange with an exothermic reaction
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P20/10—Process efficiency
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
Abstract
The invention provides a medium-pressure desorption hydrolysis tower, an energy-saving production improving device and a method for a urea production process by a carbon dioxide gas stripping method, and belongs to the field of urea chemical industry. The medium-pressure desorption hydrolysis tower is divided into an upper section and a lower section, and the lower section is provided with a condensate inlet, a high-pressure system gas inlet, a medium-pressure steam inlet and a purified water outlet; the bottom of the upper section is provided with an air lifting cap and a separator, and the upper section is also provided with a cold urine outlet communicated with the urine concentration device, a cold urine inlet communicated with the bottom of the air lifting tower and a hydrolysis gas phase outlet; the inside of the heat exchanger is provided with a gas-liquid mixed phase of the condensate and the high-pressure system gas, and the heat exchanger is used for exchanging heat with the medium-pressure steam; and the gas-liquid distribution plate is arranged for finishing desorption and hydrolysis of the condensate and the high-pressure system gas in the mixing and heat exchange processes. The invention not only realizes the deep hydrolysis of the condensate, but also reduces the water content in the gas phase at the top of the medium-pressure decomposition tower, actively controls the water-carbon ratio of the urea synthesis system, improves the urea conversion rate and realizes the full recovery of heat.
Description
Technical Field
The invention belongs to the field of urea chemical industry, and particularly relates to a medium-pressure desorption hydrolysis tower, an energy-saving production-increasing device and a method for a urea production process by a carbon dioxide gas stripping method.
Background
During the urea production process, due to the reversibility of the urea synthesis reaction, NH entering the production system3、CO2The urea can not be generated through the complete conversion of the single-pass reaction, so the raw material proportioning can not be strictly proportioned according to the reaction equation, and unreacted substances are required to be recycled by configuring a recycling circulation system and enter the production circulation again, thereby improving the synthesis rate of the urea.
In the prior art, gas stripping methods in urea production comprise a carbon dioxide gas stripping method and an ammonia gas stripping method according to different proportions of raw materials. In the circulating recovery system based on the carbon dioxide gas stripping method, products discharged from the urea synthesis tower are condensed at high pressure and low pressure to obtain condensate, the condensate enters the hydrolysis tower to be subjected to the carbon dioxide gas stripping process, and unreacted raw materials are recovered and sent back to the urea synthesis tower. However, the raw material obtained by the method through air stripping not only contains a large amount of heat but also contains a large amount of moisture, so that on one hand, the heat is continuously dissipated in the transmission process to cause energy waste, and on the other hand, a large amount of moisture directly enters the urea synthesis process, so that the water-carbon ratio of a synthesis system is increased, and the synthesis conversion rate is low.
Disclosure of Invention
In view of the above-mentioned defects or shortcomings in the prior art, the present invention aims to provide an energy-saving production-increasing device and method for a urea production process by a carbon dioxide gas stripping method, which can realize the active control of the water-carbon ratio of a urea synthesis system and increase the conversion rate of urea synthesis.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
in a first aspect, an embodiment of the present invention provides a medium-pressure desorption hydrolysis tower for a carbon dioxide gas stripping urea production process, the medium-pressure desorption hydrolysis tower is divided into an upper section and a lower section which are communicated with each other, a condensate inlet communicated with a condensate tank is arranged on the side surface of the upper part of the lower section, a high-pressure system gas inlet communicated with a high-pressure scrubber is arranged on the side surface of the middle part of the lower section, a medium-pressure steam inlet is arranged on the side surface of the lower part of the lower section, and a purified water outlet is arranged at the bottom of the lower section; the bottom of the upper section is provided with an air lifting cap, and a separator is arranged on the upper side of the air lifting cap; the side surface of the lower part of the upper section is provided with a cold urine outlet communicated with the urine concentration device, the side surface of the upper part of the upper section is provided with a cold urine inlet communicated with the bottom of the gas stripping tower, and the top of the upper section is provided with a hydrolysis gas phase outlet communicated with the urine concentration device, the medium-pressure condensation device and the high-pressure washer in sequence;
the middle part of the lower section of the medium-pressure desorption hydrolysis tower is provided with a heat exchanger for exchanging heat with medium-pressure steam by a gas-liquid mixed phase of condensate and high-pressure system gas; and the gas-liquid distribution plate is arranged for finishing desorption and hydrolysis of the condensate and the high-pressure system gas in the mixing and heat exchange processes.
As a preferred embodiment of the invention, the gas-liquid distribution plate consists of a tower plate and a distribution unit; the distribution unit comprises a liquid descending device with an opening and a gas lifting device with an opening, and the gas phase and the liquid phase are uniformly distributed through the cooperation of the liquid descending device and the gas lifting device.
As a preferred embodiment of the invention, the pressure adopted by the lower section of the medium-pressure desorption hydrolysis tower is 1.9-2.5 MPa, and the pressure adopted by the upper section of the medium-pressure desorption hydrolysis tower is 1.6-1.9 MPa.
As a preferred embodiment of the invention, the gas-phase flow velocity on the gas-liquid distribution plate is 25-35 m/s, and the liquid-phase flow velocity on the gas-liquid distribution plate is 0.5-3 m/s.
In a preferred embodiment of the invention, the temperature of the condensate is 170-200 ℃, the temperature of the high-pressure system gas is 160-185 ℃, the temperature of the purified water is 190-220 ℃, and the temperature of the gas phase at the gas lifting cap is 170-195 ℃; the average temperature of the gas-liquid distribution plate is 155-175 ℃.
In a second aspect, the embodiment of the present invention further provides an energy-saving production-extracting device for a carbon dioxide gas-stripping urea production process, where the equipment for producing urea by a carbon dioxide gas-stripping method includes a urea synthesis tower, a carbon dioxide gas-stripping tower, an ammonium carbamate condenser, a high-pressure scrubber, a low-pressure rectification device, a medium-pressure absorption tower, a condensate tank, a urine tank, and a urine concentration device, and the energy-saving production-extracting device includes the medium-pressure desorption hydrolysis tower and the medium-pressure ammonium carbamate condensation device; wherein the content of the first and second substances,
the condensate tank is connected with the medium-pressure absorption tower and is communicated with a condensate inlet of the medium-pressure desorption hydrolysis tower; a high-pressure system gas outlet of the high-pressure scrubber is communicated with a high-pressure system gas inlet of the medium-pressure desorption hydrolysis tower; the gas-liquid distribution plate and the heat exchanger at the lower section of the medium-pressure desorption hydrolysis tower are used for uniformly mixing, desorbing and hydrolyzing the condensate with the high-pressure system gas, the purified water outlet is used for discharging medium-pressure steam for completing heat exchange, and the gas phase for completing heat exchange, desorption and hydrolysis enters the upper section of the medium-pressure desorption hydrolysis tower through the gas lifting cap;
the cold urine outlet at the bottom of the carbon dioxide gas stripping tower is communicated with the cold urine inlet of the medium-pressure desorption hydrolysis tower; the cold urine outlet of the medium-pressure desorption hydrolysis tower is communicated with the liquid phase inlet of the low-pressure rectification device, the liquid phase inlet of the urine concentration device and the urine groove in sequence; a hydrolysis gas phase outlet of the medium-pressure desorption hydrolysis tower is communicated with a gas phase inlet of the urine concentration device, an inlet of the medium-pressure methylamine condensation device and an inlet of the high-pressure washer in sequence; the urine concentrating device is used for carrying out heat exchange between the hydrolyzed gas phase and the cold urine, and simultaneously discharges the cold urine into the urine tank after concentrating the cold urine.
As a preferred embodiment of the invention, the device further comprises a heat exchanger arranged outside the medium-pressure desorption hydrolysis tower, wherein a low-temperature inlet of the heat exchanger is communicated with an outlet of the condensate tank, and a low-temperature outlet of the heat exchanger is communicated with a condensate inlet of the medium-pressure desorption hydrolysis tower; and a high-temperature inlet of the heat exchanger is communicated with a purified water outlet, and a high-temperature outlet of the heat exchanger is connected with water using equipment.
In a third aspect, an embodiment of the present invention further provides an energy-saving production improving method for a urea production process by a carbon dioxide gas stripping method, where the method is implemented by using the above energy-saving production improving apparatus, and specifically includes the following steps:
step S1, in the lower section of the medium-pressure desorption hydrolysis tower, after the condensate from the condensate tank is pressurized by a feed pump, the condensate enters the medium-pressure desorption hydrolysis tower from a condensate inlet, and the high-pressure system gas of the high-pressure scrubber enters the medium-pressure desorption hydrolysis tower from a high-pressure system gas inlet;
step S2, mixing the condensate and the high-pressure system gas into a gas-liquid mixed phase, performing heat exchange with medium-pressure steam on a heat exchanger in the middle of the medium-pressure desorption hydrolysis tower, uniformly mixing and distributing the gas-liquid mixed phase on a gas-liquid distribution plate in the medium-pressure desorption hydrolysis tower, heating and stripping the gas by the medium-pressure steam, hydrolyzing the condensate and urea in the high-pressure system gas to generate ammonia and carbon dioxide, feeding the ammonia, the carbon dioxide and the water which are free with the condensate and the urea in the high-pressure system gas into a separator in a gas phase through a gas lifting cap at the bottom of the upper section of the hydrolysis tower, and discharging a liquid phase through a purified water outlet at the bottom of the medium-pressure desorption hydrolysis tower;
step S3, in the upper section of the medium-pressure desorption hydrolysis tower, the gas phase entering the separator through the gas lift cap exchanges heat with the cold urine from the bottom of the carbon dioxide gas stripping tower, the water vapor enters the cold urine after being condensed, and the residual ammonia, carbon dioxide and water are discharged from the top of the upper section of the medium-pressure desorption hydrolysis tower in a gas phase; after heat exchange is completed, the cold urine absorbs condensed water and enters a low-pressure rectifying device;
step S4, cold urine enters a urine concentration device through a low-pressure rectification device and a liquid phase inlet, a hydrolysis gas phase discharged from the top of a medium-pressure desorption hydrolysis tower is mixed with a condensate separated by the low-pressure rectification device, the cold urine enters the urine concentration device through a gas phase inlet, the urine is concentrated through the waste heat of the mixed phase of the hydrolysis gas phase and the condensate, the concentrated urine is discharged into a urine tank, and a gas-liquid mixed phase after heat exchange enters a medium-pressure methylamine condensation device;
and step S5, condensing and separating the gas-liquid mixed phase from the urine concentration device through a medium-pressure methylamine condenser to finish gas-liquid separation of the gas-liquid mixed phase, wherein the gas phase enters a low-pressure rectification device, and the liquid phase enters a high-pressure scrubber and returns to the urea synthesis tower.
As a preferred embodiment of the present invention, the step S1 further includes: the condensate from the carbon dioxide stripping tower exchanges heat with purified water discharged from the bottom of the medium-pressure desorption hydrolysis tower before entering the medium-pressure desorption hydrolysis tower.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
mixing high-pressure system gas and condensate by arranging a medium-pressure desorption hydrolysis tower, and then carrying out heat exchange with medium-pressure steam through a heat exchanger; the gas phase generated by hydrolysis is obtained after heat exchange and then is subjected to heat exchange with cold urine, so that deep hydrolysis is realized, raw materials in condensate are recycled, and the uniformity of gas phase distribution and the heat recovery efficiency are improved; meanwhile, the water content in the gas phase at the top of the medium-pressure decomposition tower separator is reduced, the active control on the water-carbon ratio of a urea synthesis system is realized, the conversion rate of urea synthesis is improved, and the conversion rate of urea synthesis is at least improved by 1-2%.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a medium-pressure desorption hydrolysis tower for a carbon dioxide stripping urea production process, provided by an embodiment of the invention;
FIG. 2 is a top view of a gas-liquid distribution plate of the medium-pressure desorption hydrolysis tower shown in FIG. 1;
FIG. 3 is a cross-sectional view of a gas-liquid distribution plate of the medium-pressure desorption hydrolysis tower shown in FIG. 1;
FIG. 4 is a schematic diagram of the structure and connection of an energy-saving production improving device for a urea production process by a carbon dioxide stripping method according to an embodiment of the invention.
Description of reference numerals:
100-medium pressure desorption hydrolysis tower; 101-a condensate inlet; 102-high pressure system gas inlet; 103-medium pressure steam inlet; 104-a purified water outlet; 106-cold urine outlet; 105-cold urine inlet; 107-outlet of hydrolysis gas phase; 108 — internal heat exchanger; 109-gas-liquid distribution plate; 91-gas-liquid distribution plate column plate; 92-gas-liquid distribution plate distribution unit; 921-liquid-dropping device; 922-an air-lift device; 923-forming holes; 110-rising gas cap; 111-a separator; 112-external heat exchanger; 113-medium pressure condensing unit; 201-a urea synthesis tower; 202-high pressure scrubber; 203-methylammonium condenser; 204-a carbon dioxide stripper; 205-a low pressure rectification plant; 206-medium pressure absorption tower; 207-urine concentrating device; 208-a urine bath; 209-condensate tank.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
As shown in fig. 1, the embodiment of the present invention provides a medium pressure desorption hydrolysis tower 100 for a carbon dioxide gas stripping urea production process, wherein the medium pressure desorption hydrolysis tower 100 is divided into an upper section and a lower section which are communicated with each other, the upper side surface of the lower section is provided with a condensate inlet 101 communicated with a condensate tank, the middle side surface of the lower section is provided with a high pressure system gas inlet 102 communicated with a high pressure scrubber, the lower side surface of the lower section is provided with a medium pressure steam inlet 103, and the bottom of the lower section is provided with a purified water outlet 104; the bottom of the upper section is provided with an air lifting cap 110, and the upper side of the air lifting cap 110 is provided with a separator 111; the lower side of the upper section is provided with a cold urine outlet 106 communicated with the urine concentration device, the upper side of the upper section is provided with a cold urine inlet 105 communicated with the bottom of the gas stripping tower, and the top of the upper section is provided with a hydrolysis gas phase outlet 107 communicated with the urine concentration device, the medium-pressure condensation device and the high-pressure washer in sequence. The middle part of the lower section of the medium-pressure desorption hydrolysis tower is provided with a heat exchanger 108 for exchanging heat with medium-pressure steam by a gas-liquid mixed phase of condensate and high-pressure system gas; and the gas-liquid distribution plate 109 is also arranged for finishing desorption and hydrolysis of the condensate and the high-pressure system gas in the mixing and heat exchange processes.
As an embodiment of the present invention, as shown in fig. 2 and fig. 3, the gas-liquid distribution plate 109 is composed of a tray 91 and a distribution unit 92; wherein, the distribution unit 92 includes the liquid descending device 921 that has the trompil 923 and the lift gas device 922 that has the trompil 923, realizes the evenly distributed of gaseous phase and liquid phase through the cooperation of liquid descending device and lift gas device. The opening 923 may be in any shape, such as diamond, heart, rectangle, circle, polygon, etc.
When the intermediate product of the urea synthesized by the carbon dioxide gas stripping method is recovered by adopting the medium-pressure desorption hydrolysis tower, the high-pressure system gas of the high-pressure scrubber and the condensate in the condensation tank are mixed in the medium-pressure desorption hydrolysis tower, and the first heat exchange is completed in the mixing process; and introducing medium-pressure steam in the medium-pressure desorption hydrolysis tower, and then finishing secondary heat exchange with the gas-liquid mixed phase. Sufficient heat recovery is ensured in the heat exchange while providing energy for the desorption and hydrolysis processes.
As shown in figure 1, the second heat exchange process of the gas phase and the liquid phase is completed by a heat exchanger inside the medium-pressure desorption hydrolysis tower. Meanwhile, the gas-liquid distribution plate is arranged in the medium-pressure desorption hydrolysis tower, so that the gas phase and the liquid phase are fully and uniformly mixed through the gas-liquid distribution plate, and the gas phase and the liquid phase are kept in the medium-pressure desorption hydrolysis tower for a long enough time to complete desorption and hydrolysis. The medium-pressure desorption hydrolysis tower not only provides enough pressure for desorption, but also provides enough temperature for hydrolysis, so that desorption and hydrolysis can be simultaneously realized.
In a specific embodiment of the invention, the pressure applied to the lower section of the medium-pressure desorption hydrolysis tower is 1.9-2.5 MPa, and the pressure applied to the upper section is 1.6-1.9 MPa. In order to ensure complete completion of desorption and hydrolysis, the gas phase flow rate on the gas-liquid distribution plate is 25-35 m/s, and the liquid phase flow rate is 0.5-3 m/s. In addition, the temperature of the condensate is 170-200 ℃, the temperature of the high-pressure system gas is 160-185 ℃, the temperature of the purified water is 190-220 ℃, and the temperature of the gas phase at the gas lifting cap is 170-195 ℃; the average temperature of the gas-liquid distribution plate is 155-175 ℃.
Through the setting of the parameters, the medium-pressure desorption hydrolysis tower realizes the desorption of a carbon dioxide gas stripping method and the hydrolysis of urea at the same time, so that the ammonia and urea content in the discharged purified water are less than 5ppm, and the method can be directly applied to other production processes, for example, as a desalted water raw material.
The liquid phase after the desorption hydrolysis, i.e., the purified water, is discharged from the medium pressure desorption hydrolysis tower through the purified water outlet 104, and the purified water has a certain amount of heat. In a specific embodiment of the invention, a heat exchanger is arranged outside the medium-pressure desorption hydrolysis tower, a low-temperature inlet of the heat exchanger is communicated with an outlet of a condensate tank, and a low-temperature outlet of the heat exchanger is communicated with a condensate inlet of the medium-pressure desorption hydrolysis tower; and a high-temperature inlet of the heat exchanger is communicated with a purified water outlet, and a high-temperature outlet of the heat exchanger is connected with water using equipment. In the heat exchanger outside the medium-pressure desorption hydrolysis tower, the purified water with certain heat and the condensate in the condensate tank carry out primary heat exchange, the condensate is subjected to primary heating, and the heat is fully recycled through the heat exchange.
The top gas after the desorption hydrolysis enters the upper section of the medium-pressure desorption hydrolysis tower through the gas rising cap 110. The constituents of the gas phase include ammonia, carbon dioxide from hydrolysis, and free ammonia, carbon dioxide, and water. In the separator, the overhead gas is fully contacted with cold urine from a carbon dioxide stripping tower, so that the impact on the packing or tray of the separator of the medium-pressure desorption hydrolysis tower is reduced, and the heat of the overhead gas is fully recycled through heat exchange. At this time, water in the gas phase is condensed to become a liquid phase, the liquid phase enters cold urine, and the residual ammonia and carbon dioxide carrying a small amount of water are discharged from the top end of the medium-pressure desorption hydrolysis tower and enter the next heat exchange due to heat. At this time, the cold urine is diluted due to the inflow of the condensed water, and in the subsequent recovery process, the urine needs to be concentrated and then recovered. At the moment, the gas phase with certain heat discharged from the top is mixed with condensate liquid from the low-pressure rectification device which is originally converged into the urine concentration device to form a gas-liquid mixed phase, and the gas-liquid mixed phase enters the urine concentration device; the diluted urine is primarily treated by the low-pressure rectifying tower and then converged into the urine concentrating device, and the urine is concentrated by the heat of the gas-liquid mixed phase, so that the heat in the system is fully recycled. The urine concentrating device can be modified on the basis of urea synthesis equipment, a gas phase inlet from the top of the medium-pressure desorption hydrolysis tower is added, and a heat exchange device is added; the urine pre-concentration tower and the corresponding devices such as an aftercooler, an ejector and the like can also be additionally arranged. The concentrated urine is directly converged into a urine tank; the gas-liquid mixed phase after heat exchange enters a medium-pressure methylamine condenser. The temperature of the gas-liquid mixed phase is preliminarily reduced, all intermediate products in the system are recovered, the corresponding hydrolysis process is also carried out, ammonium carbamate condensate is obtained after the temperature is reduced, and the ammonium carbamate condensate returns to the high-pressure washer and the urea synthesis process.
It can be seen from the above that, in the urea synthesis process by the carbon dioxide gas stripping method, the medium-pressure desorption hydrolysis tower provided by the embodiment replaces a deep hydrolysis device, and the desorption and hydrolysis processes are realized by one device, so that not only is the moisture in the recovered gas phase reduced, but also the water-carbon ratio in the urea synthesis system is actively controlled, the conversion rate of urea synthesis is improved, and meanwhile, the heat of the system is fully recycled, and the desorption and hydrolysis processes are realized in the same device, so that the investment cost and the operation consumption are saved, and the urea production cost is reduced.
The embodiment of the invention also provides an energy-saving production improving device for the urea production process by the carbon dioxide gas stripping method. As shown in fig. 4, the apparatus for producing urea by carbon dioxide stripping method comprises a urea synthesis tower 201, a carbon dioxide stripping tower 204, an ammonium carbamate condenser 203, a high-pressure scrubber 202, a low-pressure rectification device 205, a medium-pressure absorption tower 206, a condensate tank 209, a urine tank 208 and a urine concentration device 207, and the energy-saving production-increasing device comprises the medium-pressure desorption hydrolysis tower 100 and the medium-pressure ammonium carbamate condensation device 113.
Wherein, the condensate tank 209 connected with the medium-pressure absorption tower 206 is communicated with the condensate inlet 101 of the medium-pressure desorption hydrolysis tower; the high-pressure system gas outlet of the high-pressure scrubber 202 is communicated with the high-pressure system gas inlet 102 of the medium-pressure desorption hydrolysis tower; the gas-liquid distribution plate 109 and the heat exchanger 108 on the lower section of the medium-pressure desorption hydrolysis tower are used for uniformly mixing, desorbing and hydrolyzing the condensate with the high-pressure system gas, the purified water outlet 104 is used for discharging the purified water after heat exchange, and the gas-lifting cap 110 is used for feeding the gas phase after heat exchange, desorption and hydrolysis into the upper section of the medium-pressure desorption hydrolysis tower.
The cold urine outlet at the bottom of the carbon dioxide stripping tower 104 is communicated with the cold urine inlet 105 of the medium-pressure desorption hydrolysis tower; the cold urine outlet 106 of the medium-pressure desorption hydrolysis tower is sequentially communicated with the liquid-phase inlet of the low-pressure rectifying device 205, the liquid-phase inlet of the urine concentrating device 207 and the urine groove 208; the hydrolysis gas phase outlet 107 of the medium-pressure desorption hydrolysis tower is communicated with a gas phase inlet of a urine concentration device 207, an inlet of a medium-pressure methylamine condensation device 113 and an inlet of a high-pressure washer 202 in sequence; the urine concentrating device 207 is used for exchanging heat between the hydrolyzed gas phase and the cold urine, and simultaneously, the cold urine is concentrated and then discharged into a urine tank.
In a specific embodiment of the invention, the energy-saving production-increasing device further comprises a heat exchanger 112 arranged outside the medium-pressure desorption hydrolysis tower 100, a low-temperature inlet of the heat exchanger 112 is communicated with an outlet of a condensate tank, and a low-temperature outlet of the heat exchanger is communicated with a condensate inlet 101 of the medium-pressure desorption hydrolysis tower; the high-temperature inlet of the heat exchanger is communicated with the purified water outlet 104, and the high-temperature outlet is connected with water using equipment.
The embodiment of the invention also provides an energy-saving production improving method for the urea production process by the carbon dioxide gas stripping method, which is realized by adopting the energy-saving production improving device and specifically comprises the following steps:
and step S1, in the lower section of the medium-pressure desorption hydrolysis tower, after the condensate from the condensate tank is pressurized by the feed pump, the condensate enters the medium-pressure desorption hydrolysis tower from the condensate inlet, and the high-pressure system gas of the high-pressure scrubber enters the medium-pressure desorption hydrolysis tower from the high-pressure system gas inlet.
And step S2, mixing the condensate with the high-pressure system gas to form a gas-liquid mixed phase, performing heat exchange with medium-pressure steam on a heat exchanger in the middle of the medium-pressure desorption hydrolysis tower, uniformly mixing and distributing the gas-liquid mixed phase on a gas-liquid distribution plate in the medium-pressure desorption hydrolysis tower, heating and stripping the gas by the medium-pressure steam, hydrolyzing the condensate and urea in the high-pressure system gas to generate ammonia and carbon dioxide, feeding the ammonia, the carbon dioxide and the water, which are free, into a separator in a gas phase through a gas lifting cap at the bottom of the upper section of the hydrolysis tower, and discharging a liquid phase through a purified water outlet at the bottom of the medium-pressure desorption hydrolysis tower.
In the step, the condensate and the high-pressure system gas stay in the medium-pressure desorption hydrolysis tower for a long enough time, the urea realizes deep hydrolysis and releases latent heat, the hydrolyzed condensate becomes purified water and is discharged from a purified water outlet, and the content of the discharged purified water urea and ammonia is lower than 5ppm, so that the reutilization of water resources can be met.
Step S3, in the upper section of the medium-pressure desorption hydrolysis tower, the gas phase entering the separator through the gas lift cap exchanges heat with the cold urine from the bottom of the carbon dioxide gas stripping tower, the water vapor enters the cold urine after being condensed, and the residual ammonia, carbon dioxide and water are discharged from the top of the upper section of the medium-pressure desorption hydrolysis tower in a gas phase; after heat exchange is completed, the cold urine absorbs condensed water and enters a low-pressure rectifying device.
In the step, the heat exchange tubes in the medium-pressure desorption decomposer are used for distributing gas phase in heat exchange, so that the gas stripping-hydrolysis tower top gas enters the upper section through the gas lifting cap and is fully contacted with cold urine, the impact on the filler or tray of the medium-pressure decomposition tower separator is reduced, the heat (including latent heat and sensible heat) of the tower top gas of the medium-pressure desorption hydrolysis tower is fully recovered, and the water content in the methylamine solution is reduced, so that the water-carbon ratio returned to the urea synthesis tower is reduced, the active control on the water-carbon ratio in the urea synthesis tower is realized, the urea synthesis conversion rate is improved, the subsequent low-pressure system circulation volume is reduced, and the operation elasticity of a subsequent device is improved.
Step S4, cold urine enters a urine concentration device through a low-pressure rectification device and a liquid phase inlet, a hydrolysis gas phase discharged from the top of a medium-pressure desorption hydrolysis tower is mixed with a condensate separated by the low-pressure rectification device, the cold urine enters the urine concentration device through a gas phase inlet, the urine is concentrated through the waste heat of the mixed phase of the hydrolysis gas phase and the condensate, the concentrated urine is discharged into a urine tank, and a gas-liquid mixed phase after heat exchange enters a medium-pressure methylamine condensation device;
and step S5, condensing and separating the gas-liquid mixed phase from the urine concentration device through a medium-pressure methylamine condenser to finish gas-liquid separation of the gas-liquid mixed phase, wherein the gas phase enters a low-pressure rectification device, and the liquid phase enters a high-pressure scrubber and returns to the urea synthesis tower.
It should be noted that the energy-saving production improving method for the carbon dioxide gas stripping urea production line corresponds to the energy-saving production improving device, and the description and limitation of the energy-saving production improving device are also applicable to the energy-saving production improving method in the embodiment, and are not described herein again.
According to the technical scheme, the energy-saving production increasing device and method for the urea production process by the carbon dioxide gas stripping method, provided by the embodiment of the invention, solve the problem of the deficiency of a process condensate deep hydrolysis system in the urea production process by the existing carbon dioxide gas stripping method, fully utilize the existing equipment and realize the purpose of completely recycling the heat of the tower top gas; the distribution uniformity of gas phase and gas-liquid mixed phase is improved by the internal structure design of the medium-pressure desorption hydrolysis tower; meanwhile, the water content in the gas phase at the top of the medium-pressure desorption hydrolysis tower separator is reduced, the active control of the water-carbon ratio of the urea synthesis system is realized, the conversion rate of urea synthesis is improved, and the circulation volume of a subsequent recovery system is reduced, so that the aims of increasing the yield and reducing the consumption are fulfilled.
The foregoing description is only exemplary of the preferred embodiments of the invention and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other arrangements formed by any combination of the above features or their equivalents without departing from the spirit of the invention. For example, the above features and (but not limited to) features having similar functions disclosed in the present invention are mutually replaced to form the technical solution.
Claims (9)
1. A medium-pressure desorption hydrolysis tower for a carbon dioxide gas stripping urea production process is characterized in that,
the medium-pressure desorption hydrolysis tower is divided into an upper section and a lower section which are communicated with each other, the side surface of the upper part of the lower section is provided with a condensate inlet communicated with a condensate tank, the side surface of the middle part of the lower section is provided with a high-pressure system gas inlet communicated with a high-pressure washer, the side surface of the lower part of the lower section is provided with a medium-pressure steam inlet, and the bottom of the lower section is provided with a purified water outlet; the bottom of the upper section is provided with an air lifting cap, the upper side of the air lifting cap is provided with a separator, and the air lifting cap is used for finishing heat exchange, desorption and hydrolysis of gas phase which enters the upper section of the medium-pressure desorption hydrolysis tower; the side surface of the lower part of the upper section is provided with a cold urine outlet communicated with the low-pressure rectifying device and the urine concentrating device, the side surface of the upper part of the upper section is provided with a cold urine inlet communicated with the bottom of a carbon dioxide gas stripping tower, and the top of the upper section is provided with a hydrolysis gas phase outlet communicated with the urine concentrating device, a medium-pressure methylamine condensing device and a high-pressure washer in sequence;
the middle part of the lower section of the medium-pressure desorption hydrolysis tower is provided with a heat exchanger for exchanging heat with medium-pressure steam by a gas-liquid mixed phase of condensate and high-pressure system gas; and the gas-liquid distribution plate is arranged for finishing desorption and hydrolysis of the condensate and the high-pressure system gas in the mixing and heat exchange processes.
2. The medium-pressure desorption hydrolysis column as claimed in claim 1, wherein the gas-liquid distribution plate is composed of a tray and a distribution unit; the distribution unit comprises a liquid descending device with an opening and a gas lifting device with an opening, and the gas phase and the liquid phase are uniformly distributed through the cooperation of the liquid descending device and the gas lifting device.
3. The medium-pressure desorption hydrolysis tower as claimed in claim 1 or 2, wherein the lower section of the medium-pressure desorption hydrolysis tower adopts a pressure of 1.9-2.5 MPa, and the upper section adopts a pressure of 1.6-1.9 MPa.
4. The medium-pressure desorption hydrolysis tower as claimed in claim 1 or 2, wherein the gas-phase flow rate on the gas-liquid distribution plate is 25-35 m/s, and the liquid-phase flow rate is 0.5-3 m/s.
5. The medium-pressure desorption hydrolysis tower as claimed in claim 1 or 2, wherein the temperature of the condensate is 170-200 ℃, the temperature of the high-pressure system gas is 160-185 ℃, the temperature of the purified water is 190-220 ℃, and the temperature of the gas phase at the gas-lifting cap is 170-195 ℃; the average temperature of the gas-liquid distribution plate is 155-175 ℃.
6. An energy-saving production-extracting device for a carbon dioxide gas-stripping urea production process, wherein equipment of the carbon dioxide gas-stripping urea production process comprises a urea synthesis tower, a carbon dioxide gas-stripping tower, an ammonium carbamate condenser, a high-pressure washer, a low-pressure rectifying device, a medium-pressure absorption tower, a condensate tank, a urine tank and a urine concentrating device, and is characterized in that the energy-saving production-extracting device comprises the medium-pressure desorption hydrolysis tower as claimed in any one of claims 1 to 5, and further comprises a medium-pressure ammonium carbamate condensing device; wherein the content of the first and second substances,
the condensate tank is connected with the medium-pressure absorption tower and is communicated with a condensate inlet of the medium-pressure desorption hydrolysis tower; a high-pressure system gas outlet of the high-pressure scrubber is communicated with a high-pressure system gas inlet of the medium-pressure desorption hydrolysis tower; the gas-liquid distribution plate and the heat exchanger at the lower section of the medium-pressure desorption hydrolysis tower are used for uniformly mixing, desorbing and hydrolyzing the condensate with the high-pressure system gas, the purified water outlet is used for discharging the purified water subjected to heat exchange by medium-pressure steam, and the gas phase subjected to heat exchange, desorption and hydrolysis by the gas lifting cap enters the upper section of the medium-pressure desorption hydrolysis tower;
the cold urine outlet at the bottom of the carbon dioxide gas stripping tower is communicated with the cold urine inlet of the medium-pressure desorption hydrolysis tower; the cold urine outlet of the medium-pressure desorption hydrolysis tower is communicated with the liquid phase inlet of the low-pressure rectification device, the liquid phase inlet of the urine concentration device and the urine groove in sequence; a hydrolysis gas phase outlet of the medium-pressure desorption hydrolysis tower is communicated with a gas phase inlet of the urine concentration device, an inlet of the medium-pressure methylamine condensation device and an inlet of the high-pressure washer in sequence; the urine concentrating device is used for carrying out heat exchange between the hydrolyzed gas phase and the cold urine, and discharging the cold urine into a urine tank after concentrating the cold urine; and the gas-liquid mixed phase from the urine concentration device is condensed and separated by a medium-pressure methylamine condensation device to complete gas-liquid separation of the gas-liquid mixed phase, wherein the gas phase enters a low-pressure rectification device, and the liquid phase enters a high-pressure washer and returns to the urea synthesis tower.
7. The energy-saving production improving device for the carbon dioxide gas stripping urea production process according to claim 6, characterized by further comprising a heat exchanger arranged outside the medium-pressure desorption hydrolysis tower, wherein a low-temperature inlet of the heat exchanger is communicated with a condensate tank outlet, and a low-temperature outlet of the heat exchanger is communicated with a condensate inlet of the medium-pressure desorption hydrolysis tower; and a high-temperature inlet of the heat exchanger is communicated with a purified water outlet, and a high-temperature outlet of the heat exchanger is connected with water using equipment.
8. An energy-saving production improving method for a urea production process by a carbon dioxide gas stripping method, which is characterized by being realized by the energy-saving production improving device of claim 6 or 7, and specifically comprising the following steps:
step S1, in the lower section of the medium-pressure desorption hydrolysis tower, after the condensate from the condensate tank is pressurized by a feed pump, the condensate enters the medium-pressure desorption hydrolysis tower from a condensate inlet, and the high-pressure system gas from the high-pressure washer enters the medium-pressure desorption hydrolysis tower from a high-pressure system gas inlet;
step S2, mixing the condensate and the high-pressure system gas into a gas-liquid mixed phase, performing heat exchange with medium-pressure steam on a heat exchanger in the middle of the medium-pressure desorption hydrolysis tower, uniformly mixing and distributing the gas-liquid mixed phase on a gas-liquid distribution plate in the medium-pressure desorption hydrolysis tower, heating and stripping the gas by the medium-pressure steam, hydrolyzing the condensate and urea in the high-pressure system gas to generate ammonia and carbon dioxide, feeding the ammonia, the carbon dioxide and the water which are free with the condensate and the urea in the high-pressure system gas into a separator in a gas phase through a gas lifting cap at the bottom of the upper section of the hydrolysis tower, and discharging a liquid phase through a purified water outlet at the bottom of the medium-pressure desorption hydrolysis tower;
step S3, in the upper section of the medium-pressure desorption hydrolysis tower, the gas phase entering the separator through the gas lift cap exchanges heat with the cold urine from the bottom of the carbon dioxide gas stripping tower, the water vapor enters the cold urine after being condensed, and the residual ammonia, carbon dioxide and water are discharged from the top of the upper section of the medium-pressure desorption hydrolysis tower in a gas phase; after heat exchange is completed, the cold urine absorbs condensed water and enters a low-pressure rectifying device;
step S4, cold urine enters a urine concentration device through a low-pressure rectification device and a liquid phase inlet, a hydrolysis gas phase discharged from the top of a medium-pressure desorption hydrolysis tower is mixed with a condensate separated by the low-pressure rectification device, the cold urine enters the urine concentration device through a gas phase inlet, the urine is concentrated through the waste heat of the mixed phase of the hydrolysis gas phase and the condensate, the concentrated urine is discharged into a urine tank, and a gas-liquid mixed phase after heat exchange enters a medium-pressure methylamine condensation device;
and step S5, condensing and separating the gas-liquid mixed phase from the urine concentration device through a medium-pressure methylamine condensation device to finish gas-liquid separation of the gas-liquid mixed phase, wherein the gas phase enters a low-pressure rectification device, and the liquid phase enters a high-pressure scrubber and returns to the urea synthesis tower.
9. The energy-saving production-increasing method according to claim 8, wherein the step S1 further comprises: the condensate from the carbon dioxide stripping tower exchanges heat with purified water discharged from the bottom of the medium-pressure desorption hydrolysis tower before entering the medium-pressure desorption hydrolysis tower.
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| IT1232670B (en) * | 1989-09-15 | 1992-03-02 | Snam Progetti | PROCEDURE FOR PURIFICATION OF WASTEWATER PRODUCED BY UREA PRODUCTION PLANTS. |
| CN2637484Y (en) * | 2003-08-14 | 2004-09-01 | 宁波远东化工科技有限公司 | Synthetic ammonia, urea waste liquid treatment device |
| CN100400430C (en) * | 2006-05-18 | 2008-07-09 | 刘国胜 | Energy saving, purifying and recovering process for urea process condensate |
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| CN101696177B (en) * | 2009-11-02 | 2012-07-04 | 河南心连心化肥有限公司 | Device for processing urea process condensate and method thereof |
| CN102267754A (en) * | 2010-06-02 | 2011-12-07 | 张庆喜 | Combined technique of advanced urea hydrolysis under low pressure and production apparatus thereof |
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