CN111318042A - Device system and method for producing modified urea - Google Patents
Device system and method for producing modified urea Download PDFInfo
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- CN111318042A CN111318042A CN202010138590.XA CN202010138590A CN111318042A CN 111318042 A CN111318042 A CN 111318042A CN 202010138590 A CN202010138590 A CN 202010138590A CN 111318042 A CN111318042 A CN 111318042A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C9/00—Fertilisers containing urea or urea compounds
- C05C9/005—Post-treatment
Abstract
The invention discloses a device system and a method for producing modified urea. The device system comprises a urea synthesis system, a rectification flash system, an evaporation concentration system a, a granulation system, a packaging system, a dust washing and recovery system, an evaporation concentration system b, a vacuum condensation system and an auxiliary agent adding and conveying system which are sequentially connected. Wherein, the two sets of evaporation concentration systems are in a low-pressure working condition, so that the corrosion degree of chloride ions and the like can be reduced; the vacuum condensation system can ensure that the ammonia consumption of the urea product is always in a lower level; the modified urea is controllably prepared by the aid adding and conveying system, so that the operation and control are convenient, and the controllability is strong due to the combination of the operation rule and the original urea evaporation system.
Description
Technical Field
The invention relates to a device system and a method for producing modified urea, belonging to the field of nitrogen fertilizer production.
Background
The traditional urea production capacity in China is surplus, meanwhile, the Ministry of agriculture proposes a 'zero increase action scheme of fertilizer usage amount in 2020', and the work of creating special differentiated products by fertilizer enterprises to improve competitiveness and promote fertilizer 'reduction and increase' is very important.
In the production process of urea, the interior of a high-pressure ring composed of a urea synthesis tower, a stripping tower and a high-pressure washer is made of stainless steel, and under the conditions of high temperature and high pressure, the sensitivity of stress corrosion cracking of the stainless steel can be greatly improved if chloride ions exist in a process medium, so that various cracks appear on the surface of equipment. In the actual production, the chloride ion is strictly controlled, the chloride ion content is required to be less than 0.2ppm as qualified, but the chloride ion content in various additives required by the production of modified urea products reaches over 50ppm and far exceeds the upper limit of the chloride ion control content after entering the system. According to the traditional technology for producing modified urea by tower granulation, various additives and coloring agents are added at the top of the tower, and dust urea does not enter a melting device after being collected, so that harmful ions are isolated outside a urea high-pressure system, and diversified and differentiated production of tower granulation products can be realized. The large particle granulation technology of the circulating fluidized bed is used in a large urea device from the nineties of the last century in China, the technology has the characteristics of high production capacity, uniform urea particles and high particle strength, the fertilizer efficiency of urea products has the slow release characteristic, and dust urea is washed and recycled to a molten urea system, so that condensate generated by an evaporation system is recycled and enters a urea high-pressure ring. Therefore, when the circulating fluidized bed granulation technology is used for producing modified products, how to utilize the circulating fluidized bed urea device to produce urea products meeting the market requirements and simultaneously ensure the safety of high-pressure ring production equipment, particularly how to treat dust and steam condensate generated by producing modified urea granulation, realize safe, environment-friendly and stable operation, avoid the corrosion problem of harmful ions to equipment such as a high-pressure ring and the like, and become a difficult problem of enterprises for producing modified urea products by adopting the circulating fluidized bed granulation technology.
Disclosure of Invention
The invention aims to provide a device system and a method for producing modified urea.
The invention provides a device system for producing modified urea, which comprises a urea synthesis system, a rectification flash system, an evaporation concentration system a, a granulation system, a packaging system, a dust washing and recovery system, an evaporation concentration system b, a vacuum condensation system and an auxiliary agent adding and conveying system which are sequentially connected;
the evaporation concentration system a comprises a concentrated solution outlet and a gas phase port, the concentrated solution outlet is connected with the granulation system, and the gas phase port is connected with the urea synthesis system through a decomposition and recycling system;
the granulation system is connected with the dust washing and recovering system and is used for washing dust generated by the granulation system; the dust washing and recovering system is used for concentrating the recovered dust washing water through the connected evaporation and concentration system b, and the dust washing water concentrated by the evaporation and concentration system b is mixed with the outlet of the evaporation and concentration system a and enters the granulation system connected with the evaporation and concentration system a; the evaporation concentration system b condenses the generated gas phase through the vacuum condensation system connected with the evaporation concentration system b and recovers condensed water, and then the condensed water generated by the vacuum condensation system returns to the dust washing recovery system connected with the evaporation concentration system b;
the pipeline between the dust washing and recovering system and the evaporation and concentration system b is connected with the auxiliary agent adding and conveying system so as to add the auxiliary agent into the evaporation and concentration system b and mix the auxiliary agent with the solution in the evaporation and concentration system b;
the systems are connected through pipelines.
In the invention, the condensed water generated by the vacuum condensation system returns to the dust washing system to be used as washing water or concentrated to be sent to a boiler denitration system, so that water balance is realized.
In the above-mentioned apparatus system, the evaporation concentration system a includes a first-stage evaporation separator a1, a second-stage evaporation separator a2 and a molten urea pump a connected in sequence;
the first-stage evaporation separator a1 and the second-stage evaporation separator a2 sequentially concentrate urine and send the concentrated urine to the granulation system through the molten urea pump a.
In the device system, the dust washing and recovering system comprises a dust washing system and a urine recovering tank which are connected in sequence;
the urine recovery groove conveys urine therein to the evaporation concentration system b through a urine recovery pump.
In the above-mentioned apparatus system, the evaporation concentration system b comprises a first-stage evaporation separator b1, a second-stage evaporation separator b2 and a molten urea pump b which are connected in sequence;
the two-stage evaporation separator conveys the concentrated urine to an inlet of a molten urea pump a through a molten urea pump b, and then the concentrated urine enters the granulation system through the molten urea pump a for granulation.
In the above device system, the evaporation concentration system b further comprises a urine storage tank;
the two-stage evaporation separator b2 is used for conveying the concentrated urine with the concentration not reaching more than 96.5% to the urine storage tank through the molten urea pump b, and the outlet of the urine storage tank is connected to the urine recovery tank.
In the above apparatus system, the vacuum condensing system comprises vacuum coolers a, b, c, vapor extractors a, b, c and a condensate storage tank;
outlets of the first-stage evaporation separator and the second-stage evaporation separator b2 are respectively connected with the vacuum coolers a and b, the vacuum coolers a, b and c are respectively connected with the steam extractors a, b and c, and an outlet of the steam extractor a is connected with an inlet pipeline of the steam extractor b;
the vacuum coolers a, b and c are connected to the condensate storage tank;
the condensate storage tank is connected with a condensate pump to send condensate in the condensate storage tank to the dust washing system.
In the above device system, the auxiliary agent adding and conveying system includes an auxiliary agent adding tank and an auxiliary agent conveying pump, and the auxiliary agent adding tank conveys the auxiliary agent to the evaporation and concentration system b through the auxiliary agent conveying pump;
an auxiliary agent adding metering pump and a stirring device are further arranged in the auxiliary agent adding tank.
In the above-mentioned device system, valves are respectively disposed on the pipelines between the molten urea pump a and the granulation system, between the molten urea pump b and the molten urea pump a, between the molten urea pump b and the urine storage tank, between the urine storage tank and the urine recovery tank, between the auxiliary agent delivery pump and the evaporation concentration system b, and between the condensed liquid pump and the dust washing system.
The invention also provides a method for producing urea by adopting the device system to carry out granulation on the circulating fluidized bed, which comprises the following steps: synthesizing a urea solution in the urea synthesis system by using liquid ammonia and carbon dioxide as raw materials, concentrating the urea solution to be more than 96.5% by using the rectification flash evaporation system and the evaporation concentration system a, sending the concentrated urea solution to the granulation system for granulation by using the molten urea pump a, and then packaging the urea solution in a packaging system;
meanwhile, dust generated by the granulation system is washed by the dust washing and recovering system to obtain recovered urine; and concentrating the recovered urine through the evaporation concentration system b and the vacuum condensation system, and returning the concentrated urine to the granulation system for granulation to obtain the urea.
In the above method, when the modified urea is prepared, the method further comprises the following steps: and (3) adding the auxiliary agent into the evaporation concentration system b through the auxiliary agent adding and conveying system, mixing the auxiliary agent with the concentrated solution in the evaporation concentration system b, then mixing the mixture with the effluent of the evaporation concentration system a in an inlet of the molten urea pump a, and jointly granulating the mixture in the granulation system to obtain the modified urea.
In the above method, the dust generated by the granulation system is recovered by the following steps:
washing the dust generated by the granulation system through the dust washing system to obtain recovered urine; the recovered urine is returned to the urine recovery tank and then is conveyed to the primary evaporation separator b1 and the secondary evaporation separator b2 by the urine recovery pump to be evaporated, meanwhile, steam is condensed by the vacuum cooler, condensed water enters the condensed liquid storage tank and is conveyed to the dust washing system by a condensed liquid pump to be used as washing water; and during condensation, the vacuum degrees in the first-stage evaporation separator b1 and the second-stage evaporation separator b2 are adjusted and controlled through a steam pump, concentrated solution in the second-stage evaporation separator b2 is concentrated until the concentration reaches more than 96.5%, the concentrated solution is conveyed to the inlet of the molten urea pump a through the molten urea pump b, and the concentrated solution is mixed with concentrated solution obtained by the evaporation concentration system a and enters the granulation system for granulation.
The invention has the following advantages:
1. in the invention, the condensate liquid pump sends the condensate liquid out of the boundary area, and because the ammonia content of the condensate liquid is less than 1%, the condensate liquid ammonia content can be concentrated according to requirements and then sent to a boiler denitration system for use or directly sent to a granulation washing system for washing water, thereby ensuring that the ammonia consumption of a urea product is always in a lower level.
2. The device is in a low-pressure working condition, the corrosion degree of chloride ions and the like is reduced, and harmful ions containing the chloride ions and the like only circulate in the evaporation concentration system b, so that the original device is not influenced; the newly-added device has the advantages of small equipment investment, low corrosion degree, controllable risk and remarkable benefit.
3. The invention has simple process flow and convenient operation and control, and the modified urea is controllably prepared by the aid adding and conveying system, and the operation specification is combined with the original urea evaporation system, so that the controllability is stronger.
Drawings
FIG. 1 is a schematic diagram of a plant system for producing modified urea according to the present invention;
FIG. 2 is a schematic diagram of a specific plant system for producing modified urea according to the present invention.
The individual labels in the figure are as follows:
1 a urea synthesis system; 2, a rectification flash system; 3, an evaporation concentration system a; 4, a granulation system; 5, packaging the system; 6, a decomposition and recycling system; 7, a dust washing and recycling system; 8, an evaporation concentration system b; 9 vacuum condensation system; 10 an auxiliary agent adding and conveying system; 11 two-stage evaporative separator a 2; 12 a molten urea pump a; 13 dust washing system; 14 a urine recovery tank; 15 one-stage evaporative separator b 1; 16 two-stage evaporative separator b 2; 17 a molten urea pump b; 18 a urine receptacle; 19. 20, 20-1 vacuum coolers a, b, c; 21. 22, 23 steam extractors a, b, c; 24 a condensate sump; 25 condensate pump; 26 an auxiliary agent adding groove; 27 an auxiliary agent delivery pump; 28 urine recovery pump.
Detailed Description
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The invention is further illustrated with reference to the following figures and examples.
As shown in fig. 1, which is a schematic structural diagram of an apparatus system for producing a modified urea product according to the present invention, mainly comprises: the system comprises a urea synthesis system 1, a rectification flash system 2, an evaporation concentration system a3, a decomposition and recycling system 6, a granulation system 4, a packaging system 5, a dust washing and recycling system 7, a newly-added evaporation concentration system b8, a vacuum condensation system 9 and an auxiliary agent adding and conveying system 10.
Wherein, the 1, 2, 3, 4, 5, 6 and 7 systems are similar to the conventional process and device, and the main difference is the improvement of 8, 9 and 10 systems. The evaporation concentration system a3 comprises a concentrated solution outlet and a gas phase port, the concentrated solution outlet is connected with the granulation system 4, and the gas phase port is connected with the urea synthesis system 1 through a decomposition and recycling system 6; the granulation system 4 is connected with the dust washing and recovering system 7, and is used for washing the dust generated by the granulation system; the dust washing and recovering system 7 is used for concentrating the recovered dust washing water through a connected evaporation and concentration system b8, and the dust washing water concentrated by the evaporation and concentration system b8 is mixed with an outlet of the evaporation and concentration system a3 and enters a granulation system 4 connected with the evaporation and concentration system a 3; the gas phase generated by the concentration of the evaporation concentration system b8 is condensed by a vacuum condensation system 9 connected with the evaporation concentration system and condensed water is recovered, and then the condensed water generated by the vacuum condensation system 9 returns to the dust washing and recovering system 7 connected with the evaporation concentration system; an auxiliary agent adding and conveying system 10 is connected to a pipeline between the dust washing and recovering system 7 and the evaporation and concentration system b8 so as to add an auxiliary agent into the evaporation and concentration system b8 and mix the auxiliary agent with a solution in the evaporation and concentration system b 8; the systems are connected through pipelines.
As shown in fig. 2, which is a schematic structural diagram of a specific apparatus system for producing modified urea according to the present invention, an evaporative concentration system a includes a primary evaporative separator a1, a secondary evaporative separator a2, and a molten urea pump a, which are connected in sequence; the first-stage evaporation separator a1 and the second-stage evaporation separator a2 sequentially concentrate urine and send the concentrated urine to the granulation system 4 through a molten urea pump a.
Further, the dust washing and recovering system 7 comprises a dust washing system 13 and a urine recovering tank 14 which are connected in sequence; the urine collection tank 14 delivers the urine therein to the evaporation concentration system b8 by the urine collection pump 28.
Further, the evaporation concentration system b8 comprises a first-stage evaporation separator b115, a second-stage evaporation separator b216 and a molten urea pump b8 which are connected in sequence; the second-stage evaporation separator b216 delivers the concentrated urine to the inlet of the urea melt pump a 12 through the urea melt pump b8, and then enters the granulation system 4 through the urea melt pump a 12 for granulation.
Further, the evaporation concentration system b8 further comprises a urine storage tank 18; the second-stage evaporation separator b216 delivers the concentrated urine with concentration not higher than 96.5% to the urine storage tank 18 through the molten urea pump b 17, and the outlet of the urine storage tank 18 is connected to the urine recovery tank 14.
Further, the vacuum condensation system 9 comprises vacuum coolers a, b, c (respectively referenced 19, 20-1) and vapor extractors a, b, c (respectively referenced 21, 22, 23) and a condensate sump 24; outlets of the first-stage evaporation separator b115 and the second-stage evaporation separator b216 are respectively connected with vacuum coolers a and b (19 and 20), steam extractors a, b and c (21, 22 and 23) are respectively connected with the vacuum coolers a, b and c (19, 20 and 20-1), and an outlet of the steam extractor a 21 is connected with an inlet pipeline of the steam extractor b 22; the vacuum coolers a, b and c (19, 20 and 20-1) are connected to a condensate storage tank 24; the condensate storage tank 24 delivers the condensate therein to the dust scrubbing system 13 by means of a condensate pump 25 connected thereto.
Further, the auxiliary agent adding and conveying system 10 includes an auxiliary agent adding tank 26 and an auxiliary agent conveying pump 27, and the auxiliary agent adding tank 26 conveys the auxiliary agent into the evaporation concentration system b8 through the auxiliary agent conveying pump 27; an assistant adding metering pump and a stirring device are also specifically arranged in the assistant adding groove 26.
Furthermore, valves are respectively arranged on pipelines between the molten urea pump a 12 and the granulation system 4, between the molten urea pump b 17 and the molten urea pump a 12, between the molten urea pump b 17 and the urine storage tank 18, between the urine storage tank 18 and the urine recovery tank 14, between the auxiliary agent delivery pump 27 and the evaporation concentration system b8, and between the condensate pump 25 and the dust washing system 13.
A process for the production of urea by means of circulating fluid bed granulation according to the plant system shown in figure 1, comprising the following steps: synthesizing a urea solution in a urea synthesis system 1 by using liquid ammonia and carbon dioxide as raw materials, concentrating the urea solution to be more than 96.5% by using a rectification flash evaporation system 2 and an evaporation concentration system a3, conveying the concentrated urea solution to a granulation system 4 for granulation by using a molten urea pump a 12, and packaging the granulated urea solution in a packaging system 5; meanwhile, dust generated by the granulation system 4 is washed by a dust washing and recovering system 7 to obtain recovered urine; and concentrating the recovered urine through an evaporation concentration system b8 and a vacuum condensation system 9, and returning the concentrated urine to the granulation system 4 for granulation to obtain the urea.
Further, when the modified urea is prepared, the method also comprises the following steps: the auxiliary agent is added into the evaporation concentration system b8 through the auxiliary agent adding and conveying system 10, is mixed with the concentrated solution in the evaporation concentration system b8, enters an inlet of a molten urine pump a 12 and is mixed with the effluent of the evaporation concentration system a3, and enters a granulation system 4 together for granulation, so that the modified urea is obtained.
According to the device shown in FIG. 2, the specific process flow is as follows: the urea synthesis system 1 synthesizes urea, the urea synthesized urine is concentrated to more than 96.5% by a first-stage evaporation separator a1 (not shown) and a second-stage evaporation separator a 211 in an evaporation concentration system a3, the urea is sent to a granulation unit 4 by a molten urea pump a 12, the generated dust is washed by a dust washing system 13, washing water is returned to a urine recovery tank 14, the urine in the urine recovery tank 14 is sent to improved two-stage evaporation concentration (a first-stage evaporation separator b115 and a second-stage evaporation separator b216) by a urine recovery pump 28, the concentrated urine concentration reaches more than 96.5%, the urine is sent to an inlet of the molten urea pump a 12 by a molten urea pump b 17, and the urea is mixed with concentrated urine of a main system (the evaporation concentration system a 3) and then granulated. The auxiliary agent is mixed in the auxiliary agent adding tank 26 according to the adding concentration, is conveyed to the inlet of the first-stage evaporation separator b115 by the adding auxiliary agent conveying pump 27 to be mixed with the urine, and is mixed with the whole urine at the molten urea pump a 12. Condensate of the vacuum coolers a, b and c (19, 20 and 20-1) enters a condensate storage tank 24, and is sent to the dust washing system 13 through a condensate pump 25 to be used as washing water or concentrated to be sent to a boiler denitration system, so that water balance is realized.
The urine concentration of the urine recovery tank 14 is different according to the amount of dust; if the concentration can not reach more than 96.5% after the first-stage evaporation separator b115 and the first-stage evaporation separator b216 are concentrated by the evaporation process, the urine can be conveyed to the urine storage tank 18 by the molten urea pump b 17 and then returned to the urine recycling tank 14 for recycling concentration.
In the method, the steam extractors a, b and c (21, 22 and 23) realize the adjustment and control of the vacuum in the first-stage evaporation separator b115 and the first-stage evaporation separator b216 in the evaporation concentration system b8 by the steam drive of 0.6 MPa.
Taking the production of poly (zinc aspartate) modified urea at 100% load as an example:
synthesizing ammonia and carbon dioxide into urine in a urea synthesis system 1, concentrating the urine to be more than 96.5% by a rectification flash system 2 and an evaporation concentration system a3, sending the urine into a granulation system 4 (specifically a fluidized bed granulator) for granulation, and recovering dust generated in the granulation process into a urine recovery tank 14 through a dust washing system 13; the poly-ammonia zinc medicament is configured into 25% solution in the additive adding groove 26, the solution and the 40% dust melt-back urine 9t/h conveyed by the urine recovery pump 28 are jointly fed into a first-stage evaporation separator b115(130 ℃, 33KPa (A)) and a second-stage evaporation separator b216(132 ℃, 18KPa (A)) for concentration at the flow rate of 1.4t/h through the additive conveying pump 27 at normal temperature, the concentrated urine reaches more than 96.5%, the concentrated urine is fed into the inlet of a molten urea pump a 12 through a molten urea pump b 17, and the concentrated urine is mixed with fresh urine and then fed into a fluidized bed granulator for granulation.
According to the experimental result, through analyzing and checking various auxiliary agents such as poly-ammonia zinc sold in the current market, the content of chloride ions is more than 50ppm and is far higher than the limit requirement of 0.2ppm after the medicament is added into the urine; but through the improvement of the process, the urine containing high-concentration chloride ions can be ensured to be circulated in a limited unit, and the corrosion influence on key equipment is avoided.
Claims (10)
1. A device system for producing modified urea comprises a urea synthesis system, a rectification flash system, an evaporation concentration system a, a granulation system, a packaging system, a dust washing and recovery system, an evaporation concentration system b, a vacuum condensation system and an auxiliary agent adding and conveying system which are sequentially connected;
the evaporation concentration system a comprises a concentrated solution outlet and a gas phase port, the concentrated solution outlet is connected with the granulation system, and the gas phase port is connected with the urea synthesis system through a decomposition and recycling system;
the granulation system is connected with the dust washing and recovering system and is used for washing dust generated by the granulation system; the dust washing and recovering system is used for concentrating the recovered dust washing water through the connected evaporation and concentration system b, and the dust washing water concentrated by the evaporation and concentration system b is mixed with the outlet of the evaporation and concentration system a and enters the granulation system connected with the evaporation and concentration system a; the evaporation concentration system b condenses the generated gas phase through the vacuum condensation system connected with the evaporation concentration system b and recovers condensed water, and then the condensed water generated by the vacuum condensation system returns to the dust washing recovery system connected with the evaporation concentration system b;
the pipeline between the dust washing and recovering system and the evaporation and concentration system b is connected with the auxiliary agent adding and conveying system so as to add the auxiliary agent into the evaporation and concentration system b and mix the auxiliary agent with the solution in the evaporation and concentration system b;
the systems are connected through pipelines.
2. The device system of claim 1, wherein: the evaporation concentration system a comprises a first-stage evaporation separator a1, a second-stage evaporation separator a2 and a molten urea pump a which are connected in sequence;
the first-stage evaporation separator a1 and the second-stage evaporation separator a2 sequentially concentrate urine and send the concentrated urine to the granulation system through the molten urea pump a.
3. The device system according to claim 1 or 2, characterized in that: the dust washing and recovering system comprises a dust washing system and a urine recovering tank which are connected in sequence;
the urine recovery groove conveys urine therein to the evaporation concentration system b through a urine recovery pump.
4. The device system according to any one of claims 1-3, wherein: the evaporation concentration system b comprises a first-stage evaporation separator b1, a second-stage evaporation separator b2 and a molten urea pump b which are connected in sequence;
the two-stage evaporation separator b2 conveys the concentrated urine to the inlet of the molten urea pump a through the molten urea pump b, and then enters the granulation system for granulation through the molten urea pump a;
and/or the presence of a gas in the gas,
the evaporation concentration system b also comprises a urine storage tank;
the two-stage evaporation separator b2 is used for conveying the concentrated urine with the concentration not reaching more than 96.5% to the urine storage tank through the molten urea pump b, and the outlet of the urine storage tank is connected to the urine recovery tank.
5. The device system according to claim 3 or 4, characterized in that: the vacuum condensation system comprises vacuum coolers a, b and c, vapor extractors a, b and c and a condensate storage tank;
outlets of the first-stage evaporation separator b1 and the second-stage evaporation separator b2 are respectively connected with the vacuum coolers a and b, the vacuum coolers a, b and c are respectively connected with the steam extractors a, b and c, and an outlet of the steam extractor a is connected with an inlet pipeline of the steam extractor b;
the vacuum coolers a, b and c are connected to the condensate storage tank;
the condensate storage tank is connected with a condensate pump to send condensate in the condensate storage tank to the dust washing system.
6. The device system according to any one of claims 1-5, wherein: the auxiliary agent adding and conveying system comprises an auxiliary agent adding groove and an auxiliary agent conveying pump, and the auxiliary agent adding groove conveys the auxiliary agent to the evaporation concentration system b through the auxiliary agent conveying pump;
an auxiliary agent adding metering pump and a stirring device are further arranged in the auxiliary agent adding tank.
7. The device system according to any one of claims 2-6, wherein: valves are respectively arranged on pipelines between the molten urea pump a and the granulation system, between the molten urea pump b and the molten urea pump a, between the molten urea pump b and the urine storage tank, between the urine storage tank and the urine recovery tank, between the auxiliary agent delivery pump and the evaporation concentration system b, and between the condensed liquid pump and the dust washing system.
8. A process for the production of urea by means of circulating fluid bed granulation using the plant system according to any one of claims 1 to 7, comprising the following steps: synthesizing a urea solution in the urea synthesis system by using liquid ammonia and carbon dioxide as raw materials, concentrating the urea solution to be more than 96.5% by using the rectification flash evaporation system and the evaporation concentration system a, sending the concentrated urea solution to the granulation system for granulation by using the molten urea pump a, and then packaging the urea solution in a packaging system;
meanwhile, dust generated by the granulation system is washed by the dust washing and recovering system to obtain recovered urine; and concentrating the recovered urine through the evaporation concentration system b and the vacuum condensation system, and returning the concentrated urine to the granulation system for granulation to obtain the urea.
9. The method of claim 8, wherein: when the modified urea is prepared, the method also comprises the following steps: and (3) adding the auxiliary agent into the evaporation concentration system b through the auxiliary agent adding and conveying system, mixing the auxiliary agent with the concentrated solution in the evaporation concentration system b, then mixing the mixture with the effluent of the evaporation concentration system a in an inlet of the molten urea pump a, and jointly granulating the mixture in the granulation system to obtain the modified urea.
10. The method according to claim 8 or the method, characterized by: in the method, the process of recovering the dust generated by the granulation system comprises the following steps:
washing the dust generated by the granulation system through the dust washing system to obtain recovered urine; the recovered urine is returned to the urine recovery tank and then is conveyed to the primary evaporation separator b1 and the secondary evaporation separator b2 by the urine recovery pump to be evaporated, meanwhile, steam is condensed by the vacuum cooler, condensed water enters the condensed liquid storage tank and is conveyed to the dust washing system by a condensed liquid pump to be used as washing water; and during condensation, the vacuum degrees in the first-stage evaporation separator b1 and the second-stage evaporation separator b2 are adjusted and controlled through a steam pump, concentrated solution in the second-stage evaporation separator b2 is concentrated until the concentration reaches more than 96.5%, the concentrated solution is conveyed to the inlet of the molten urea pump a through the molten urea pump b, and the concentrated solution is mixed with concentrated solution obtained by the evaporation concentration system a and enters the granulation system for granulation.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112358327A (en) * | 2020-11-26 | 2021-02-12 | 河南晋开化工投资控股集团有限责任公司 | Energy-saving type large-particle urea granulation system and granulation process |
| CN112694349A (en) * | 2020-12-24 | 2021-04-23 | 绿色造粒(北京)技术有限公司 | Preparation system and preparation method of slow-release urea |
| CN113457191A (en) * | 2021-07-15 | 2021-10-01 | 华强化工集团股份有限公司 | Flash evaporation system |
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Application publication date: 20200623 |