Method and device for separating and recovering by-product ammonium carbonate generated in ketazine preparation process

Abstract

The invention belongs to the field of separation and recovery of by-products in an organic reaction process, and particularly relates to a method and a device for separating and recovering by-product ammonium carbonate generated in a ketazine preparation process. A ketazine synthetic liquid water layer is introduced into an ammonia discharge kettle to be heated, gasified materials pass through a condenser, liquid enters an oil-water separation device, and after oil-water separation, the water layer enters an ammonium carbonate distillation kettle to be subjected to thermal decomposition; the generated carbon dioxide and ammonia gas enter an ammonium carbonate collecting tank through a gas-phase pipeline preheated by steam to be condensed to obtain supersaturated ammonium carbonate turbid liquid, ammonia gas is introduced, cooling crystallization is performed, the supersaturated ammonium carbonate turbid liquid enters a filter to be filtered, and the obtained solid is recycled ammonium carbonate. According to the method, 99% of ammonium carbonate in the ketazine synthesis liquid can be separated, the content of the byproduct ammonium carbonate can reach 31-33.5% (based on ammonia), and the national food-grade standard is met.

Description

Technical Field

[0001] The invention belongs to the field of separation and recovery of by-products in an organic reaction process, and specifically relates to a method and a device for separation and recovery of ammonium carbonate, a by-product generated in a ketazine preparation process. Background Art

[0002] As an important inorganic fine chemical intermediate, hydrazine hydrate is widely used in the synthesis of pesticides, medicines, foaming agents, initiators, curing agents, polymerization catalysts, etc. There are many industrial synthesis routes for hydrazine hydrate, the main ones being the Raschig method, the urea method, the ketazine method, and the hydrogen peroxide oxidation method.

[0003] The hydrogen peroxide method uses hydrogen peroxide as an oxidant under the action of an ammonia catalyst to oxidize a mixture of ammonia water and ketone compounds to synthesize the corresponding ketone azine intermediate, which is then hydrolyzed under high pressure to obtain hydrazine hydrate and the corresponding ketone compound. During the preparation process, an activator is required to help the butanone azine reaction to form. The activators that can be selected include organic amines or nitriles such as formamide, acetamide, propionamide, acetonitrile, and propionitrile. These organic ammonia or nitriles will be partially hydrolyzed into the corresponding organic acid ammonium during the reaction, resulting in reduced activity. In order to restore activity, patent WO2018065997A1 mentions that the corresponding amide or nitrile is recovered after long-term dehydration at 140-145°C.

[0004] In addition, the activators of the hydrogen peroxide method need to be activated at high temperature after the reaction. This process will cause the decarboxylation of organic ammonium acid to release carbon dioxide. At the same time, when the activator is formamide, ammonium formate, etc., it will also be oxidized into carbonic acid by hydrogen peroxide. The generated carbon dioxide will eventually form ammonium carbonate enrichment in the ammonia system. Experiments have shown that when the carbonate content exceeds 0.5%, it will have a significant impact on the reaction yield. Ammonium carbonate will decompose into carbon dioxide and ammonia above 50°C. Carbon dioxide and ammonia will turn into ammonium carbonate again when condensed, making it difficult to simply separate ammonium carbonate and water. It will continue to be enriched in the system, eventually resulting in excessive ammonium carbonate in the synthesis system, affecting the synthesis yield. Even if the water is scrapped and treated because the system water contains too much ammonia and needs to be discharged, the carbonate and ammonia in the process still need to be separated.

[0005] Patents US5252309A and CN1028520C mention a solution of enriching carbonate in the bottom of the tower by ultra-low temperature and negative pressure concentration at 20-45°C. These solutions have the following problems: 1. This method is only suitable for the situation where the ammonium carbonate content of the bottom concentrate is low. After the concentration exceeds 2%, ammonium carbonate will appear at the top of the tower, and the separation efficiency will be significantly reduced; 2. Multiple dehydration consumes a lot of energy; 3. The process of negative pressure dehydration and concentration of ammonium carbonate uses a distillation tower, which requires large equipment investment and space; 4. In order to ensure that carbonate is decomposed to the top of the tower as little as possible, an extremely low dehydration temperature is required, and high requirements are placed on the refrigerant at the top of the tower; 5. There is a lack of feasible solutions for the treatment of wastewater enriched in the bottom of the tower to contain more than 2% ammonium carbonate. Summary of the invention

[0006] The present invention aims at the deficiencies existing in the prior art and provides a method and device for separating and recovering ammonium carbonate, a byproduct produced in the process of preparing ketazine. In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] The water layer of the ketazine synthesis liquid is passed into the ammonia discharge kettle for heating. After the vaporized material passes through the condenser, the liquid enters the oil-water separation device. After the oil-water separation, the water layer enters the ammonium carbonate distillation kettle for thermal decomposition. The generated carbon dioxide and ammonia enter the ammonium carbonate collection tank through the gas phase pipeline preheated by steam to condense to obtain a supersaturated ammonium carbonate suspension. Ammonia is passed in, the temperature is reduced and crystallized, and the solid obtained by filtration in the filter is the recovered ammonium carbonate.

[0008] Furthermore, the water layer of the ketazine synthesis liquid is passed into an ammonia exhaust kettle for heating, the vaporized material passes through a condenser, the non-condensable gas enters an ammonia tail gas absorption system, the liquid enters an oil-water separation device, the oil layer enters a butanone recovery device after oil-water separation, the water layer enters an ammonium carbonate distillation kettle for thermal decomposition, the generated carbon dioxide and ammonia enter an ammonium carbonate collecting tank through a gas phase pipeline preheated by steam to condense to obtain a supersaturated ammonium carbonate suspension, the non-condensable ammonia in the ammonium carbonate collecting tank is passed into an ammonia tail gas absorption system, ammonia is passed into the supersaturated ammonium carbonate suspension, the temperature is reduced and crystallized, and the solid obtained by filtration in a filter is the recovered ammonium carbonate.

[0009] The ammonia exhaust kettle is equipped with a packed tower, and the vaporized material is separated and purified by the packed tower before entering the condenser.

[0010] The supersaturated ammonium carbonate suspension obtained in the ammonium carbonate collection tank is placed in an ammonium carbonate crystallization kettle, ammonia gas is introduced, the temperature is reduced for crystallization, and the solid obtained by filtering through a filter is the recovered ammonium carbonate.

[0011] The heating temperature in the ammonia discharge kettle is 90-105°C. When the temperature exceeds 105°C, the ammonia discharge and deketone removal are stopped.

[0012] After a batch of materials in the ammonia discharge kettle is discharged and de-ammonia is removed, the batch can be continued to be processed until the water layer collected in the oil-water separation device reaches a certain volume and then concentrated into the ammonium carbonate distillation kettle for the next step of processing. Alternatively, the water layer can be directly placed into the ammonium carbonate distillation kettle for the next step of processing after each batch of materials is discharged and de-ammonia is removed. The remaining materials in the ammonia discharge kettle are placed in the working liquid recovery and treatment system for further dehydration and recovery of the activator.

[0013] The pressure of the thermal decomposition reaction in the ammonium carbonate distillation kettle is a positive pressure of 0-400 kPa, preferably 0-100 kPa, the temperature is 80-150° C., preferably 100-118° C., the reaction time is 0.5-12 hours, and the pressure of the thermal decomposition reaction is adjusted by charging nitrogen. After the thermal decomposition reaction, the remaining material in the ammonium carbonate distillation kettle is placed in an ammonia exhaust kettle for further concentration treatment.

[0014] The temperature of the gas phase pipeline preheated by steam is 50-150° C., preferably 100-150° C., to prevent condensation of ammonium carbonate. The steam is low-pressure steam.

[0015] The ammonium carbonate collection tank is equipped with a condensation system, and the condensed water temperature is 30-40℃.

[0016] Ammonia gas is introduced into the supersaturated ammonium carbonate suspension to control the ammonia content of the mother liquid to be greater than 25%, preferably 25%-27%.

[0017] The cooling crystallization is to cool the temperature to 0-5°C to crystallize out the solid.

[0018] The liquid obtained after filtration is returned to the ammonium carbonate distillation kettle or the ammonia exhaust kettle for further processing.

[0019] The non-condensable ammonia gas from the condenser and the ammonium carbonate distillation kettle needs to pass through the ammonium carbonate washing system to remove the decomposed ammonium carbonate (in the form of carbon dioxide or ammonia) before entering the ammonia water absorption system. The material obtained from the ammonium carbonate washing system can also enter the nitrogen exhaust kettle for treatment.

[0020] The separation and recovery device includes an ammonia exhaust kettle, a condenser, an oil-water separation device, an ammonium carbonate distillation kettle, an ammonium carbonate collecting tank, and a filter which are sequentially connected through pipelines; wherein the ammonium carbonate distillation kettle is also directly connected to the ammonia exhaust kettle through a pipeline, and the filter is also directly connected to the ammonia exhaust kettle or the ammonium carbonate distillation kettle through a pipeline.

[0021] Furthermore,

[0022] An ammonium carbonate crystallization kettle is also arranged between the ammonium carbonate collecting tank and the filter; the condenser and the ammonium carbonate collecting tank are both connected to the ammonia tail gas absorption system, and an ammonium carbonate washing system is arranged before the ammonia tail gas absorption system; the oil-water separation device is also connected to the butanone recovery device.

[0023] The bottom of the ammonia exhaust kettle is also connected to the working fluid recovery and processing system.

[0024] Ketazine synthesis liquid refers to the intermediate ketazine synthesis liquid synthesized by hydrazine hydrate in the hydrogen peroxide method. The activating agent used is organic amide or ammonium acid such as formamide, acetamide, propionamide, ammonium formate, ammonium acetate, ammonium propionate, etc.; the ketone used is ketone organic matter such as acetone, butanone, benzophenone, etc.

[0025] Beneficial effects of the present invention:

[0026] The present invention utilizes the property that ammonium carbonate is easily decomposed by heat, first extracts it from the water layer of the synthetic liquid, then thermally decomposes the extract to enrich and concentrate the high-concentration ammonium carbonate again, and finally, by-product ammonium carbonate is obtained by crystallization and separation after further reducing the solubility of ammonium carbonate by supplementing ammonia gas. The present invention does not increase any raw material input, is economical and environmentally friendly, and the recovered ammonia water does not introduce new impurities and does not affect the system reuse. The by-product ammonium carbonate is an excellent nitrogen fertilizer with a wide range of uses, and the process does not generate any wastewater discharge. The present invention can separate 99% of the ammonium carbonate in the keto-azo synthesis liquid, and the by-product ammonium carbonate content can reach 31-33.5% (in terms of ammonia), meeting the national food grade standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the device used in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below in conjunction with specific embodiments, but the present invention is not limited to the following description:

[0029] The ketone azine synthesis liquid water layer refers to the synthesis liquid of the intermediate ketone azine synthesized by the hydrogen peroxide method hydrazine hydrate, and the ketone used can be acetone, butanone, benzophenone and other ketone organic substances; the activator used is formamide, acetamide, propionamide, ammonium formate, ammonium acetate, ammonium propionate and other organic amides or ammonium acids. The embodiment of the present invention processes the butanone azine water layer, and butanone and formamide (activator) are used in the synthesis of the butanone azine water layer, and the ammonium carbonate content is 0.5-1%.

[0030] Example 1

[0031] A method for separating and treating butanone azine water layer and ammonium carbonate, comprising the following steps: adding 2200L of synthetic liquid water layer into a 3000L ammonia discharge kettle equipped with a 3-meter packing tower, stirring and heating to 90-105°C to discharge ammonia and remove ketone, separating and purifying the gasified product through the packing tower, extracting most of the gasified ammonia from the top of the tower and directly entering the ammonium carbonate washing system through a condenser (circulating water condensation) as non-condensable gas through a gas phase pipeline, washing and removing carbonic acid, and then recovering the ammonia tail gas absorption system to obtain ammonia water, the gasified water, butanone, ammonium carbonate, part of ammonia and other components extracted from the top of the tower are condensed into liquids through a condenser and separated into layers in an oil-water separation device, the precipitated water layer is passed into an ammonium carbonate distillation kettle for the next step of treatment, and the oil layer is passed into a butanone recovery system to recover butanone. After the temperature of the ammonia discharge kettle reaches 105°C, the discharge of ammonia and the removal of ketone are stopped. The sedimentation tank of the oil-water separation device collects 95kg of the water layer, and analysis shows that it contains 15.5% ammonium carbonate and 16.5% ammonia. The remaining material in the ammonia kettle is about 1800L. Analysis shows that the ammonium carbonate content is less than 0.01% and the ammonia content is less than 0.05%. The remaining material in the kettle is placed in the working liquid recovery and treatment system for further dehydration and recovery of the activator.

[0032] In the ammonia discharge kettle, the ammonia removal and ketone removal are carried out for many times until the water layer in the sedimentation tank of the oil-water separation device reaches 2400kg, and then the ammonium carbonate distillation kettle is pumped in, nitrogen is filled to a gauge pressure (positive pressure) of 100kpa, the temperature is raised to 110-118℃, and the positive pressure of 100±5kpa is maintained by a regulating valve for thermal decomposition. The carbon dioxide and ammonia produced by the decomposition are depressurized to the gas phase pipeline through the regulating valve. The gas phase pipeline is pre-heated to 100-150℃ with low-pressure steam (0.2-0.5mpa), and the decomposed gas after decompression enters the ammonium carbonate collection tank through the gas phase pipeline for collection. The cooling water temperature of the ammonium carbonate collection tank is controlled at 30-40℃ for condensing the ammonium carbonate in the gasification product. After 5 hours of thermal decomposition reaction, the ammonium carbonate collection tank receives 304.3kg of supersaturated ammonium carbonate suspension. There are about 1935kg of residual material in the ammonium carbonate distillation kettle, which is put into the ammonia discharge kettle for further concentration treatment. The non-condensable gas from the ammonium carbonate collection tank is introduced into the ammonia tail gas absorption system to obtain 642.8 kg of 25% ammonia water.

[0033] The supersaturated ammonium carbonate suspension in the ammonium carbonate collection tank is placed in an ammonium carbonate crystallization kettle, the ammonia content in the solution is analyzed, ammonia gas is introduced to ensure that the solution contains 25-27% ammonia, and the temperature is lowered to 0-5°C for filtration. After filtration, 260.1 kg of ammonium carbonate is recovered after low-temperature drying of the filter cake, and the analysis content is 32.6% (in terms of ammonia). The mother liquor analysis contains 25.67% ammonia and 20.69% ammonium carbonate, which is pumped into an ammonium carbonate distillation kettle to continue deammonium carbonate or return to the ammonia kettle for further concentration.

[0034] Example 2

[0035] 2200L of synthetic liquid water layer is added to a 3000L ammonia discharge kettle equipped with a 3-meter packed tower, stirred and heated to 90-105℃ to discharge ammonia and remove ketones. The gasified product is separated and purified by the packed tower. Most of the vaporized ammonia produced from the top of the tower is directly introduced into the ammonium carbonate washing system through the condenser (circulating water condensation) as non-condensable gas through the gas phase pipeline. After washing and removing carbonic acid, the ammonia tail gas absorption system is recovered to obtain ammonia water. The vaporized water, butanone, ammonium carbonate, part of ammonia and other components produced from the top of the tower are condensed by the condenser to the oil-water separation device for stratification. The precipitated water layer is passed into the ammonium carbonate distillation kettle for treatment, and the oil layer is passed into the butanone recovery system to recover butanone. After the temperature of the ammonia discharge kettle reaches 105℃, the discharge of ammonia and ketone removal is stopped. 95kg of water layer is collected in the sedimentation tank of the oil-water separation device, and the analysis shows that it contains 15.5% ammonium carbonate and 16.5% ammonia. The remaining liquid in the ammonia discharge kettle is about 1800L. Analysis shows that the ammonium carbonate content is less than 0.01% and the ammonia content is less than 0.05%. The remaining material in the kettle is placed in the working liquid recovery and treatment system for further dehydration and recovery of the activator.

[0036] After multiple ammonia removal and deketone removal in the ammonia removal kettle until the water layer in the sedimentation tank of the oil-water separation device reaches 2400kg, the ammonium carbonate distillation kettle is pumped in, nitrogen is filled to a gauge pressure (positive pressure) of 200kpa, the temperature is raised to 125-132℃, and the positive pressure of 200±5kpa is maintained by a regulating valve for thermal decomposition. The carbon dioxide and ammonia produced by decomposition are depressurized to the gas phase pipeline through the regulating valve. The gas phase pipeline is pre-heated to 100-150℃ with low-pressure steam (0.2-0.5mpa). The decomposed gas after decompression enters the ammonium carbonate collection tank through the gas phase pipeline for collection. The cooling water temperature of the ammonium carbonate collection tank is controlled at 30-40℃ for condensing the ammonium carbonate in the gasification product. After 3 hours of thermal decomposition reaction, the ammonium carbonate collection tank receives 301.2kg of supersaturated ammonium carbonate suspension. There are about 1939kg of residual material in the ammonium carbonate distillation kettle, which is put into the ammonia removal kettle for further concentration treatment. The non-condensable gas from the ammonium carbonate collection tank is introduced into the ammonia tail gas absorption system to obtain 639.2 kg of 25% ammonia water.

[0037] The supersaturated ammonium carbonate suspension in the ammonium carbonate collection tank is analyzed for ammonia content in the solution, and ammonia gas is introduced to ensure that the solution contains 25-27% ammonia, and the temperature is lowered to 0-5°C for filtration. After filtration, the filter cake is dried at low temperature to recover 259.8kg of ammonium carbonate, and the analysis content is 32.8% (in terms of ammonia). The mother liquor is analyzed to contain 26.37% ammonia and 22.28% ammonium carbonate, and is pumped into the ammonium carbonate distillation kettle to continue deammonium carbonate or return the ammonia kettle to continue concentration.

[0038] The above examples are only for illustrating the technical concept and technical features of the present invention, and cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating and recovering ammonium carbonate, a by-product produced in a ketazine preparation process, characterized in that: The water layer of the ketazine synthesis liquid is passed into the ammonia discharge kettle for heating. After the vaporized material passes through the condenser, the liquid enters the oil-water separation device. After the oil-water separation, the water layer enters the ammonium carbonate distillation kettle for thermal decomposition. The generated carbon dioxide and ammonia enter the ammonium carbonate collection tank through the gas phase pipeline preheated by steam to condense to obtain a supersaturated ammonium carbonate suspension. Ammonia is passed in, the temperature is reduced and crystallized, and the solid obtained by filtration in the filter is the recovered ammonium carbonate.

2. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1, characterized in that: The water layer of the ketazine synthesis liquid is passed into the ammonia exhaust kettle for heating. After the vaporized material passes through the condenser, the non-condensable gas enters the ammonia tail gas absorption system, the liquid enters the oil-water separation device, and after the oil-water separation, the oil layer enters the butanone recovery device, and the water layer enters the ammonium carbonate distillation kettle for thermal decomposition. The generated carbon dioxide and ammonia enter the ammonium carbonate collection tank through the gas phase pipeline preheated by steam to condense to obtain a supersaturated ammonium carbonate suspension. The non-condensable gas in the ammonium carbonate collection tank is passed into the ammonia tail gas absorption system, ammonia is passed into the supersaturated ammonium carbonate suspension, the temperature is reduced and crystallized, and the solid obtained by filtration in the filter is the recovered ammonium carbonate.

3. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1 or 2, characterized in that: The ammonia exhaust kettle is equipped with a packed tower, and the vaporized material is separated and purified by the packed tower before entering the condenser.

4. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1 or 2, characterized in that: The supersaturated ammonium carbonate suspension obtained in the ammonium carbonate collection tank is placed in an ammonium carbonate crystallization kettle, ammonia gas is introduced, the temperature is reduced for crystallization, and the solid obtained by filtering through a filter is the recovered ammonium carbonate.

5. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1, characterized in that: The heating temperature in the ammonia exhaust kettle is 90-105°C.

6. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1, characterized in that: The pressure of the thermal decomposition reaction in the ammonium carbonate distillation kettle is a positive pressure of 0-400 kPa, the temperature is 80-150° C., and the decomposition reaction time is 0.5-12 h.

7. The method for separating and recovering the by-product ammonium carbonate produced in the ketazine preparation process according to claim 1, characterized in that: The temperature of the gas phase pipeline preheated by steam is 50-150℃.

8. The method for separating and recovering by-product ammonium carbonate produced in the ketazine preparation process according to claim 4, characterized in that: Ammonia gas is introduced into the supersaturated ammonium carbonate suspension to control the ammonia content of the mother liquor to be greater than 25%.

9. An apparatus for use in the method of claim 1, characterized in that The separation and recovery device includes an ammonia discharge kettle, a condenser, an oil-water separation device, an ammonium carbonate distillation kettle, an ammonium carbonate collecting tank, and a filter which are sequentially connected through pipelines; wherein the ammonium carbonate distillation kettle is also connected to the ammonia discharge kettle through a pipeline, and the filter is also connected to the ammonia discharge kettle or the ammonium carbonate distillation kettle through a pipeline.

10. The device according to claim 9, characterized in that An ammonium carbonate crystallization kettle is also arranged between the ammonium carbonate collecting tank and the filter; the condenser and the ammonium carbonate collecting tank are both connected to the ammonia tail gas absorption system, and an ammonium carbonate washing system is arranged before the ammonia tail gas absorption system; the oil-water separation device is also connected to the butanone recovery device.

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