Treatment system and process for condensation mother liquor of alkaline ADC (azodicarbonamide) foaming agent
By designing a treatment system with multi-stage tower structure and steam reverse contact technology, the problems of high ammonia nitrogen content and insufficient urea recovery in the weak alkali condensation process are solved, efficient recycling and environmentally friendly treatment are achieved, and the conductivity and pollutants of wastewater are reduced. content.
Patent Information
- Application Number
- CN202411477141.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-22
- Publication Date
- 2025-01-10
AI Technical Summary
In the prior art, the content of ammonia nitrogen in the effluent mother liquor produced by the weak alkali condensation process is high and the urea recovery is insufficient, resulting in an increase in the impurities of biurea, a decrease in product purity and low process efficiency.
A treatment system including a biuret reactor, a centrifuge, an HDCA mother liquor tank, a first desorption tower, a second desorption tower and a hydrolysis tower were designed. The mother liquor was decomposed and recovered through a multi-stage tower structure and steam reverse contact technology. ammonia and urea reduce the conductivity and ammonia nitrogen content of wastewater.
The efficient recycling and utilization of ammonia and urea in the mother liquor is achieved. The conductivity of the wastewater after treatment is less than 10us/cm2, the ammonia nitrogen content is less than 10ppm, and the urea content is less than 100ppm, which improves the stability and environmental protection of the process.
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Figure CN119281252A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of ADC preparation, and in particular to a processing system and process for condensation mother liquor of an alkaline ADC foaming agent. Background Art
[0002] Azodicarbonamide, commonly known as ADC, is the most widely used foaming agent in the world and is used for foaming plastics and rubber. The synthesis of biurea in ADC foaming agent is the condensation reaction of urea and hydrazine hydrate, which can be divided into acid condensation and weak base condensation.
[0003] The weak base condensation method uses urea and hydrazine hydrate to react and generate biurea. Ammonia is produced as a by-product while generating biurea. The ammonia is removed from the reactor in the form of gas, and after being absorbed and purified by alkaline solution, it is reused for hydrazine hydrate synthesis, thus realizing the recycling of ammonia. The reaction equation is as follows: NH2-NH2･H2O +2NH2-CO-NH2→NH2-CO-NH-NH-CO-NH2+2NH3+ H2O However, the reaction rate is slow. In order to speed up the reaction, urea is in a state of large excess. The mother liquor after separating the biurea contains unreacted urea. At present, the mother liquor is mostly used for urea dissolution process for reuse. However, after multiple cycles, the product biurea has more impurities, darker color, and wider particle size distribution. For this reason, the process adopts the method of discharging part of the mother liquor and adding fresh water to ensure the purity of biurea.
[0004] However, how to efficiently treat the mother liquor discharged from the weak base condensation process, reduce the ammonia nitrogen content in the discharged wastewater and recover the ammonia produced by the hydrolysis of urea is an urgent problem to be solved by those skilled in the art. Summary of the invention
[0005] In view of this, the purpose of the present invention is to provide a system and process for treating the condensation mother liquor of an alkaline ADC foaming agent in view of the deficiencies of the prior art. The system can hydrolyze the mother liquor and recycle the ammonia therein, and the conductivity of the treated liquid wastewater is less than 10us / cm 2 , ammonia nitrogen content <10ppm, urea content <100ppm, energy saving and environmental protection.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A system for treating condensation mother liquor of an alkaline ADC foaming agent, comprising a biurea reactor, a centrifuge, a HDCA mother liquor tank, a first desorption tower, a second desorption tower and a hydrolysis tower; The upper inlet of the biurea reactor is connected to the urea dissolving tank and the hydrazine hydrate feeding pipe, the upper outlet is connected to the ammonia recovery process, and the lower part is connected to the centrifuge. The solid after centrifugation by the centrifuge enters the biurea deoxidation process, and the liquid after centrifugation is connected to the HDCA mother liquor tank through a pipeline. The two outlet pipelines of the HDCA mother liquor tank are respectively connected to the urea dissolving tank and the first desorption tower. The lower part of the first desorption tower is provided with a second desorption tower, and the lower part of the second desorption tower is provided with a low-pressure steam pipeline. The top of the first desorption tower is connected to the ammonia recovery process through a pipeline, and the liquid outlet of the first desorption tower is connected to the hydrolysis tower through a pipeline. The upper part of the hydrolysis tower is connected to the lower part of the first desorption tower through a pipeline, and the side of the hydrolysis tower is provided with a medium-pressure steam pipeline.
[0007] Furthermore, a heat exchanger is connected between the pipe connecting the biurea reactor and the centrifuge and the biurea reactor.
[0008] Furthermore, the HDCA mother liquor tank is connected to the first desorption tower via a desorption heat exchanger, and the bottom of the second desorption tower is connected to the desorption heat exchanger.
[0009] Furthermore, the liquid outlet of the first desorption tower is connected to the hydrolysis tower in sequence with a hydrolysis tower feed pump and a hydrolysis heat exchanger, and the liquid outlet of the hydrolysis tower is connected to the hydrolysis heat exchanger and the upper part of the second desorption tower in sequence.
[0010] Furthermore, the liquid outlet of the second desorption tower passes through the analytical heat exchanger in turn and then enters the process condensate cooler for cooling.
[0011] A process for treating the condensation mother liquor of an alkaline ADC foaming agent using the above system comprises the following steps: 1) Urea and hydrazine hydrate in the urea dissolving tank enter the biurea reactor through the feed pipe, the reaction temperature is 90-110°C, and the ammonia generated in the biurea reactor enters the ammonia recovery process through the upper outlet; 2) The reaction liquid product enters the centrifuge through the slurry delivery pump for centrifugation, the solid after centrifugation enters the biurea deoxidation process, the liquid after centrifugation enters the HDCA mother liquor tank, and then re-enters the urea dissolution tank for recycling; 3) When the mother liquor is dark brown in color, it enters the upper part of the first desorption tower after being preheated by the analytical heat exchanger. The liquid flows downward along the tower plate in the first desorption tower. The dilute solution flowing out from the bottom of the first desorption tower is pumped out by the hydrolysis tower feed pump and then heat-exchanged by the hydrolysis heat exchanger to enter the hydrolysis tower for hydrolysis. The medium-pressure steam pipeline supplies high-pressure and high-temperature steam with a temperature of 220-240°C and a pressure of 3-4Mpa. The high-temperature and high-pressure gas after hydrolysis enters the first desorption tower. The NH3 and CO2 analyzed by the first desorption tower go up to enter the ammonia recovery process; 4) The liquid in the hydrolysis tower flows out from the liquid outlet, and then enters the second desorption tower from the upper part after heat exchange in the hydrolysis heat exchanger. The low-pressure steam enters the second desorption tower through the low-pressure steam pipeline at the lower part. The temperature in the tower is 120-130℃, and the pressure is 0.2-0.3Mpa. The desorbed NH3 and CO2 go up and finally enter the ammonia recovery process; 5) The liquid flowing out of the bottom of the second desorption tower passes through the analytical heat exchanger and then enters the process condensate cooler to be cooled to 45°C and sent to the wastewater treatment unit.
[0012] The beneficial effects of the present invention are: 1. The present invention discloses a treatment system for condensation mother liquor of an alkaline ADC foaming agent. The mother liquor with a relatively light color in the early stage is returned to a urea dissolution tank for recycling. When the mother liquor turns dark brown, the system can decompose the urea therein into ammonia for recycling. The whole system has high stability, and the ammonia nitrogen and urea contents in the treated wastewater are low.
[0013] 2. The mother liquor is first preheated and then goes to the first desorption tower. When the solution flows through each tower plate from top to bottom, it contacts with the high-temperature and high-pressure gas coming out of the hydrolysis tower in reverse direction to resolve the NH3 and CO2 therein; the dilute solution flowing out of the bottom liquid outlet of the first desorption tower enters the hydrolysis tower, and after reverse contact with the medium-pressure steam, the decomposed NH3 and CO2 enter the first desorption tower. The solution flowing out of the bottom liquid outlet of the hydrolysis tower enters the second desorption tower after heat exchange, and fully contacts with the ascending low-pressure steam at its bottom, resolves the NH3 and CO2 therein and continues to ascend, and finally enters the ammonia recovery process, and the conductivity of the liquid wastewater flowing out of the second desorption tower is less than 10us / cm 2 , ammonia nitrogen content <10ppm, urea content <100ppm, and sent to the wastewater treatment unit for further treatment. The treatment process of the present application can parse out NH3 and CO2 in the mother liquor to further recycle ammonia, and the ammonia nitrogen content and urea content of the wastewater flowing out of the second desorption tower are very low, which is energy-saving and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 It is a schematic diagram of the connection structure of the processing system of the condensation mother liquor of the alkaline ADC foaming agent of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure of the first desorption tower and the second desorption tower; Figure 3 Schematic diagram of the structure of the hydrolysis tower.
[0015] In the figure: 1-biurea reactor, 2-centrifuge, 3-HDCA mother liquor tank, 4-first desorption tower, 5-second desorption tower, 6-hydrolysis tower, 7-urea dissolution tank, 8-analysis heat exchanger, 9-hydrolysis tower feed pump, 10-hydrolysis heat exchanger, 11-low-pressure steam pipeline, 12-medium-pressure steam pipeline, 13-heat exchanger, 14-process condensate cooler, 15-slurry delivery pump, 16-mother liquor delivery pump, 17-medium-pressure steam coil, 18-gas outlet. DETAILED DESCRIPTION
[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Example 1
[0017] like Figure 1 As shown, a system for treating condensation mother liquor of an alkaline ADC foaming agent comprises a biurea reactor 1, a centrifuge 2, a HDCA mother liquor tank 3, a first desorption tower 4, a second desorption tower 5 and a hydrolysis tower 6; The upper inlet of the biurea reactor 1 is connected to the urea dissolving tank 7 and the hydrazine hydrate feeding pipe, the upper outlet is connected to the ammonia recovery process, the lower part is connected to the centrifuge 2 through the slurry delivery pump 15, the pipeline connecting the biurea reactor 1 and the centrifuge 2 is connected to the biurea reactor 1 through a heat exchanger 13, the solid after centrifugation by the centrifuge 2 enters the biurea deoxidation process, the liquid after centrifugation is connected to the HDCA mother liquor tank 3 through a pipeline, the HDCA mother liquor tank 3 is connected to two outlet pipelines through a mother liquor delivery pump 16, and respectively connected to the urea dissolving tank 7 and the first desorption tower 4.
[0018] The HDCA mother liquor tank 3 is connected to the first desorption tower 4 through a desorption heat exchanger 8. A second desorption tower 5 is arranged at the lower part of the first desorption tower 4. A low-pressure steam pipeline 11 is arranged at the lower part of the second desorption tower 5. The liquid outlet of the second desorption tower 5 is connected to a wastewater treatment unit.
[0019] The top of the first desorption tower 4 is connected to the ammonia recovery process through a pipeline, the liquid outlet of the first desorption tower 4 is connected to the hydrolysis tower feed pump 9 and the hydrolysis heat exchanger 10 in sequence, and enters the hydrolysis tower 6, the upper part of the hydrolysis tower 6 is connected to the lower part of the first desorption tower 4 through a pipeline, and a medium-pressure steam pipeline 12 is arranged on the side of the hydrolysis tower 6. The liquid outlet of the lower part of the hydrolysis tower 6 is connected to the hydrolysis heat exchanger 10 and the upper part of the second desorption tower 5 in sequence, and the liquid outlet of the second desorption tower 5 enters the process condensate cooler 14 for cooling after heat exchange through the analytical heat exchanger 8, and then enters the wastewater treatment unit.
[0020] In the present application, the first desorption tower 4 and the second desorption tower 5 are both ADV floating valve trays, which are internally connected. For the connection relationship, see Figure 2The first desorption tower 4 and the second desorption tower 5 are both provided with tower plates, and the tower plates are provided with float valves. The mother liquor flows as shown by the hollow arrows, and the high-temperature and high-pressure gas flows as shown by the solid arrows, that is, the mother liquor entering from the HDCA mother liquor tank 3 after heat exchange enters from the first desorption tower 4, and the high-temperature and high-pressure NH3 and CO2 gases desorbed from the hydrolysis tower enter the first desorption tower 4 from the bottom, and the resolved NH3 and CO2 go up to enter the ammonia recovery process; in addition, the liquid flowing out from the liquid outlet of the hydrolysis tower 6 enters the second desorption tower 5 for further analysis after heat exchange in the hydrolysis heat exchanger 10, and the low-pressure steam enters the second desorption tower from the low-pressure steam pipeline 11, and fully contacts with the liquid flowing down from the top, and the resolved NH3 and CO2 continue to go up to the first analysis tower 4, and finally enter the ammonia recovery process, and the NH3 and CO2 in the ammonia recovery process can be further processed to achieve complete ammonia recovery. Example 2
[0021] The process of treating the condensation mother liquor of the alkaline ADC foaming agent by using the above system comprises the following steps: Urea and hydrazine hydrate in the urea dissolving tank 7 enter the biurea reactor 1 through the feed pipe, and the reaction temperature is 90-110°C. In this embodiment, the temperature is 90°C for the first two hours of the reaction and 105°C after 2 hours. On the one hand, the decomposition of urea is prevented, and the reaction rate can be promoted. The molar ratio of urea to hydrazine hydrate is 2-3:1, preferably 2.2-2.5:1. Although excess urea is conducive to the reaction, excessive urea content increases the subsequent urea treatment load and increases the energy consumption of the device. The ratio in this embodiment is 2.5:1. The temperature control is to heat the heat exchanger 13 to the reaction temperature for reaction; the ammonia generated during the reaction in the biurea reactor 1 enters the ammonia recovery process through the upper outlet in the gas phase, and the gas phase temperature is controlled at 70-100°C, 80°C in this embodiment, to prevent ammonia and carbon dioxide from generating carbon ammonia to block the pipeline; and during the reaction, as the gas phase enters the ammonia recovery system, it is also necessary to continuously add water to the system; At the end of the condensation reaction, the hydrazine hydrate content is less than 2%, the condensation mother liquor contains 9-13wt% urea, 1-2wt% ammonia, hydrazine hydrate <2wt%, and 83-88% water. In this embodiment, the condensation mother liquor contains 12wt% urea, 2wt% ammonia, hydrazine hydrate <2wt%, and 84% water; 2) The reaction liquid product (biurea slurry) is transported to the centrifuge 2 through the slurry delivery pump 15 for centrifugation. The solid after centrifugation in the centrifuge 2 enters the biurea deoxidation process. The liquid after centrifugation enters the HDCA mother liquor tank 3 and then re-enters the urea dissolution tank 7 for recycling; 3) In this embodiment, when the mother liquor is circulated 21 times and the mother liquor is dark brown in color, the pipeline entering the urea dissolution tank 7 is closed, and the mother liquor is sent to the hydrolysis process. The mother liquor is preheated by the analytical heat exchanger 8 at a flow rate of 2-3 t / h (the flow rate is controlled to be 2.5 t / h in this embodiment) and then enters the upper part of the first desorption tower 4. The liquid flows downward along the tower plates in the first desorption tower 4. The dilute solution flowing out from the bottom of the first desorption tower 4 is pumped out by the hydrolysis tower feed pump 9 and then enters the hydrolysis tower 6 for hydrolysis through the hydrolysis heat exchanger 10 for heat exchange.
[0022] The medium-pressure steam pipeline 12 of the hydrolysis tower 6 supplies high-pressure and high-temperature steam, and the temperature of the hydrolysis tower is controlled to be 220-240°C, the pressure is 3-4Mpa, preferably 3.2-3.5Mpa, and the pressure in this embodiment is 3.5Mpa. The high-temperature and high-pressure gas containing NH3 and CO2 after hydrolysis enters the lower part of the first desorption tower 4. The pressure in the first desorption tower is generally 0.1-0.3Mpa, and the pressure in this embodiment is 0.25Mpa, and the temperature is 120-130°C, which is convenient for the analysis of ammonia and carbon dioxide. The NH3 and CO2 analyzed by the first desorption tower 4 go up at a certain pressure and enter the ammonia recovery process; The liquid in the hydrolysis tower 6 flows out from the liquid outlet, and then enters the second desorption tower 5 from the upper part after heat exchange in the hydrolysis heat exchanger 10. The low-pressure steam enters the second desorption tower 5 through the low-pressure steam pipeline 11 at the lower part. The temperature in the second desorption tower 5 is 120-130°C, and the pressure is 0.2-0.3Mpa. The actual pressure in this embodiment is 0.25Mpa. The descending liquid and the ascending low-pressure steam are in reverse contact, and the resolved NH3 and CO2 gas phase ascend and finally enter the ammonia recovery process; The structural schematic diagram of the hydrolysis tower 6 in this application is as follows Figure 3 As shown, the hydrolysis tower adopts a horizontal structure with 9 baffles inside, which divide the hydrolysis tower into 10 chambers in series, so that the flow presents a plug flow type, avoiding back mixing, and hydrolysis is carried out in it; medium-pressure steam is introduced into each chamber from the medium-pressure steam coil 17 on the bottom side, and the gas phase goes out from the upper gas outlet 18 and then merges into the first desorption tower, and the liquid phase goes out from the bottom of the other end and enters the second desorption tower. In the exchanged liquid phase, due to the desorption effect, the concentration of ammonia and carbon dioxide is very low, so as to promote the hydrolysis reaction; 5) The conductivity of the wastewater in the liquid flowing out of the bottom of the second desorption tower 5 is less than 10us / cm 2 , ammonia nitrogen content <10ppm, urea content <100ppm, cooled to 45°C through the analytical heat exchanger 8 and the process condensate cooler 14 and sent to the wastewater treatment unit.
[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.
Claims
1. A system for treating condensation mother liquor of alkaline ADC foaming agent, characterized in that: It comprises a biurea reactor (1), a centrifuge (2), an HDCA mother liquor tank (3), a first desorption tower (4), a second desorption tower (5) and a hydrolysis tower (6); The upper inlet of the biurea reactor (1) is connected to the urea dissolving tank (7) and the hydrazine hydrate feed pipe, the upper outlet is connected to the ammonia recovery process, and the lower part is connected to the centrifuge (2). The solid after centrifugation in the centrifuge (2) enters the biurea deoxidation process, and the liquid after centrifugation is connected to the HDCA mother liquor tank (3) through a pipeline. The two outlet pipelines of the HDCA mother liquor tank (3) are respectively connected to the urea dissolving tank (7) and the first desorption tower (4); A second desorption tower (5) is arranged at the lower part of the first desorption tower (4), a low-pressure steam pipeline (11) is arranged at the lower part of the second desorption tower (5), and a liquid outlet of the second desorption tower (5) is connected to a wastewater treatment unit; the top of the first desorption tower (4) is connected to an ammonia recovery process via a pipeline, the liquid outlet of the first desorption tower (4) is connected to a hydrolysis tower (6) via a pipeline, the upper part of the hydrolysis tower (6) is connected to the lower part of the first desorption tower (4) via a pipeline, and a medium-pressure steam pipeline (12) is arranged at the side of the hydrolysis tower (6).
2. The processing system of an alkaline ADC foaming agent condensation mother liquor according to claim 1, characterized in that: A heat exchanger (13) is connected between the pipe connecting the biurea reactor (1) and the centrifuge (2) and the biurea reactor (1).
3. The processing system of an alkaline ADC foaming agent condensation mother liquor according to claim 1, characterized in that: The HDCA mother liquor tank (3) and the first desorption tower (4) are connected to a desorption heat exchanger (8).
4. The processing system of an alkaline ADC foaming agent condensation mother liquor according to claim 1, characterized in that: The liquid outlet of the first desorption tower (4) is connected to the hydrolysis tower (6) in sequence with a hydrolysis tower feed pump (9) and a hydrolysis heat exchanger (10), and the liquid outlet of the hydrolysis tower (6) is connected to the hydrolysis heat exchanger (10) and the upper part of the second desorption tower (5) in sequence.
5. The processing system of an alkaline ADC foaming agent condensation mother liquor according to claim 1, characterized in that: The liquid outlet of the second desorption tower (5) passes through the analytical heat exchanger (8) in turn for heat exchange and then enters the process condensate cooler (14) for cooling before entering the wastewater treatment unit.
6. A process for treating alkaline ADC foaming agent condensation mother liquor using the system of claim 1, characterized in that: 1) Urea and hydrazine hydrate in the urea dissolving tank (7) enter the biurea reactor (1) through a feed pipe, the reaction temperature is 90-110° C. Ammonia gas generated in the biurea reactor (1) enters the ammonia recovery process through an upper outlet; 2) The reaction liquid product enters the centrifuge (2) through the slurry delivery pump (15) for centrifugation. The solid after centrifugation in the centrifuge (2) enters the biurea deoxidation process. The liquid after centrifugation enters the HDCA mother liquor tank (3) and then re-enters the urea dissolution tank (7) for recycling. 3) When the mother liquor is dark brown, it is preheated by the desorption heat exchanger (8) and then enters the upper part of the first desorption tower (4). The liquid flows downward along the tower plate in the first desorption tower (4). The dilute solution flowing out from the bottom of the first desorption tower (4) is pumped out by the hydrolysis tower feed pump (9) and then heat exchanged by the hydrolysis heat exchanger (10) and enters the hydrolysis tower (6) for hydrolysis. The medium-pressure steam pipeline (12) supplies high-pressure and high-temperature steam with a temperature of 220-240°C and a pressure of 3-4 MPa. The high-temperature and high-pressure gas after hydrolysis enters the first desorption tower (4). The NH3 and CO2 analyzed by the first desorption tower (4) go up and enter the ammonia recovery process; 4) The liquid in the hydrolysis tower (6) flows out from the liquid outlet, exchanges heat in the hydrolysis heat exchanger (10), and then enters the second desorption tower (5) from the top. The low-pressure steam enters the second desorption tower (5) through the low-pressure steam pipeline (11) at the bottom. The temperature in the tower is 120-130°C and the pressure is 0.2-0.3Mpa. The desorbed NH3 and CO2 go up and finally enter the ammonia recovery process. 5) The liquid flowing out from the bottom of the second desorption tower (5) passes through the analytical heat exchanger (8) and then enters the process condensate cooler (14) to be cooled to 45° C. and sent to the wastewater treatment unit.