Process for producing carbonated ammonium carbonate as a by-product from carbon sequestration using coking ammonia distillation ammonia water

Abstract

This invention belongs to the field of energy conservation, emission reduction, and comprehensive resource utilization technology in the coking industry, specifically involving a process for preparing industrial-grade ammonium carbonate using ammonia water and flue gas carbon dioxide, which are byproducts of the ammonia stripping section in coking. The invention uses 20% concentration ammonia water (byproduct of the ammonia stripping section) and carbon dioxide purified from coking flue gas via pressure swing adsorption as raw materials. These materials react in a carbonation tower under low temperature (0-10℃) and slightly positive pressure conditions to generate an ammonium carbonate solution. This solution is then concentrated to 50% concentration by low-temperature evaporation at 60-70℃, followed by crystallization, centrifugation, and drying with hot air at 70℃ to obtain industrial-grade solid ammonium carbonate. The condensate generated during evaporation and crystallization is recycled to the remaining ammonia water tank, achieving a closed-loop system circulation. This invention realizes in-situ coupling and high-value utilization of ammonia and carbon resources in coking enterprises, simultaneously achieving carbon sequestration and reduction.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation, emission reduction and comprehensive resource utilization technology in the coking industry, specifically involving a process for preparing industrial-grade ammonium carbonate using ammonia water and flue gas carbon dioxide produced by the ammonia stripping section of coking. Background Technology

[0002] In the coking process, coking and coal gasification enterprises generate a large amount of surplus ammonia gas after the residual ammonia water is treated by the ammonia stripping section. Conventional processes only remove ammonia nitrogen through ammonia stripping, and the concentrated ammonia water contains a large amount of carbonate impurities, which fails to realize the high-value utilization of ammonia resources. At the same time, the combustion of coke oven gas emits a large amount of carbon dioxide, which is directly released into the atmosphere, causing serious greenhouse gas emissions and resource waste.

[0003] Traditional industrial ammonium carbonate production primarily uses liquid ammonia from ammonia synthesis units and purchased carbon dioxide as raw materials, resulting in high raw material costs, high energy consumption, and poor integration with coking production systems. Currently, ammonia water, a byproduct of ammonia stripping in the coking industry, is not effectively utilized due to its high carbonate content. The lack of a closed-loop utilization of ammonia and carbon resources leads to low environmental and economic benefits, failing to meet the green transformation needs of the coking industry under the "dual carbon" target. Summary of the Invention

[0004] The purpose of this invention is to provide a process for producing ammonium carbonate as a byproduct of carbon fixation using ammonia water from coking processes. This achieves in-situ coupling and high-value utilization of ammonia and carbon resources in coking enterprises, simultaneously fulfilling the goals of carbon fixation and reduction.

[0005] The specific steps of this invention are as follows: 1. Crude ammonia water pretreatment: The crude ammonia gas produced from the top of the coking ammonia stripping section carries acidic gases such as carbon dioxide. After cooling and condensation, crude ammonia water with a concentration of about 20% (containing 8-20% ammonium carbonate) is obtained and transported to the carbonization tower. 2. Carbon dioxide capture and pressurization: The flue gas from the chimneys and other emission outlets of coking plants is separated and purified into carbon dioxide through pressure swing adsorption (PSA) process, and then pressurized to 0.1-0.3MPa (slight positive pressure) before being sent to the carbonization tower; 3. Low-temperature carbonization synthesis: Inside the carbonization tower, crude ammonia water and carbon dioxide react in a fully countercurrent manner under low temperature and slightly positive pressure conditions of 0-10℃ to produce an ammonium carbonate solution. The main reaction formula is: 2NH3⋅H2O + CO2 = (NH4)2CO3 + H2O 4. Low-temperature evaporation and concentration: The ammonium carbonate solution overflows from the top of the carbonation tower to the evaporation tower and is evaporated at a low temperature of 60-70℃ and a vacuum degree of -0.06~-0.08MPa to obtain a concentrated ammonium carbonate solution with a concentration of about 50±2%. 5. Crystallization and centrifugal separation: The concentrated liquid is fed into a crystallization tower and cooled and crystallized at 10-20℃ to obtain ammonium carbonate crystal slurry. The slurry is then centrifuged to obtain wet ammonium carbonate crystals. 6. Drying the finished product: The wet crystals are fed into a drying bed and dried with hot air at 70°C, controlling the final moisture content to ≤1.0%, to obtain a solid ammonium carbonate product that meets industrial-grade standards; 7. Condensate circulation: The condensate produced by the evaporation tower and crystallization tower is cooled to below 30°C and then returned to the remaining ammonia water tank, realizing a closed-loop water circulation system with no wastewater discharge.

[0006] The reaction temperature of the carbonization tower is 0-10℃, and the operating pressure is 0.1-0.3MPa (slight positive pressure).

[0007] The evaporation tower has an evaporation temperature of 60-70℃, a vacuum degree of -0.06~-0.08MPa, and a concentrate concentration of 50±2%.

[0008] The hot air temperature of the above-mentioned drying bed is 70℃, the product moisture content is ≤1.0%, and the product purity is ≥98.5%. Compared with existing technologies, the present invention has the following advantages: Closed-loop utilization of resources: Using coking-produced ammonia water and flue gas carbon dioxide as raw materials, there is no need to purchase synthetic ammonia and carbon sources from outside, which greatly reduces the cost of raw materials and realizes in-situ coupling and closed-loop utilization of ammonia and carbon resources. High-efficiency carbon sequestration and emission reduction: Directly capture carbon dioxide in coking flue gas and convert it into products, realize the resource utilization of greenhouse gases, and meet the carbon emission reduction and environmental protection upgrade requirements of coking enterprises; Low-energy and gentle process: Carbonation, evaporation and drying are all carried out at low temperatures to avoid high-temperature decomposition of ammonium carbonate, reduce system energy consumption and equipment corrosion, and ensure high operational stability. Zero-waste clean production: The process condensate is fully recycled, with no wastewater or exhaust gas discharged, meeting the requirements of clean production and green chemical industry; High-value benefits: The industrial-grade ammonium carbonate produced as a byproduct can be sold directly, creating additional economic benefits for coking enterprises and achieving a win-win situation for environmental protection and economic benefits. Attached Figure Description

[0009] Figure 1 The process flow diagram of this invention. Detailed Implementation

[0010] The technical solution of the present invention will be further described below through specific embodiments. Example

[0011] Taking a coking plant with an annual output of 2 million tons of coke as an example, the specific implementation steps are as follows: 1. The crude ammonia gas at the top of the coking ammonia stripping section is cooled to 30°C by a cooler and condensed to obtain crude ammonia water with a concentration of 20% (containing 12% ammonium carbonate), with a flow rate of 15 m³ / h, which is then sent to the carbonization tower. 2. The flue gas from the coking chimney is purified by a pressure swing adsorption device to obtain CO2 with a purity of ≥95%. After being pressurized to 0.2MPa, it is sent to the bottom of the carbonization tower to come into countercurrent contact with ammonia water. 3. The temperature inside the carbonation tower is controlled at 5℃ and the pressure at 0.2MPa. The reaction produces an ammonium carbonate solution, which overflows from the top of the tower to the evaporation tower. 4. The evaporation tower is controlled at a temperature of 65℃ and a vacuum of -0.07MPa to concentrate the ammonium carbonate solution to a concentration of 50%. 5. The concentrated solution is fed into a crystallization tower, cooled and crystallized at 15°C, and then separated by centrifugation to obtain wet ammonium carbonate crystals; 6. The wet crystals are fed into a vibrating fluidized bed drying bed and dried with hot air at 70℃ to obtain a solid ammonium carbonate product with a purity of 98.8% and a moisture content of 0.8%, with a yield of approximately 2.5 t / h; 7. The condensate produced by the evaporation tower and crystallization tower is cooled to 25°C and then returned to the remaining ammonia water tank. The system water consumption is close to zero and there is no wastewater discharge.

Claims

1. A process for producing carbon dioxide fixation byproduct ammonium carbonate from coking ammonia distillation ammonia water, characterized by It comprises the following steps: (1) Preparation of crude ammonia water: The crude ammonia gas from the top of the coking ammonia distillation column is cooled to obtain ammonia water with a concentration of about 20% and containing 8-20% ammonium carbonate, which is sent to the carbonation tower; (2) Carbon dioxide supply: The coking flue gas is separated and purified by pressure swing adsorption, pressurized and then sent to the carbonation tower; (3) Low-temperature carbonation: The ammonia water and carbon dioxide are reacted to generate ammonium carbonate solution under the conditions of 0-10℃ and slight positive pressure; (4) Low-temperature evaporation: The ammonium carbonate solution is overflowed from the top of the carbonation tower to the evaporation tower, and is concentrated to a concentration of 50±2% under vacuum conditions and at a temperature of 60-70℃; (5) Crystallization and centrifugal separation: The concentrated solution is sent to the crystallization tower, cooled and crystallized under the condition of 10-20℃ to obtain ammonium carbonate crystal slurry, which is centrifuged to obtain wet ammonium carbonate crystals; (6) Drying of finished product: The wet ammonium carbonate crystals are sent to the drying bed and dried with hot air at 70℃, and the final moisture content is controlled to be ≤1.0% to obtain solid ammonium carbonate product meeting the industrial grade standard; (7) Water circulation: The condensed water generated in the evaporation and crystallization is cooled and then returned to the remaining ammonia water tank to realize closed-loop circulation.

2. The process for producing carbon dioxide and by-product ammonium carbonate using carbonated ammonia water from coking according to claim 1, characterized in that The operating pressure of the carbonation tower is 0.1-0.3MPa, and the gas-liquid countercurrent contact mode is used to improve the reaction efficiency.

3. The process for producing carbon dioxide and by-product ammonium carbonate using carbonated ammonia water from coking ammonia distillation according to claim 1, characterized in that The evaporation tower operates under vacuum conditions, and the vacuum degree is -0.06~-0.08MPa to avoid high-temperature decomposition of ammonium carbonate.

4. The process for producing carbon dioxide and ammonium carbonate as by-products by using carbonated ammonia water from coking ammonia evaporation according to claim 1, characterized in that The drying bed uses hot air at 70℃ for drying, and the product moisture content is controlled to be ≤1.0% and the purity is ≥98.5%, meeting the industrial grade ammonium carbonate standard.

5. The process for producing carbon dioxide and ammonium carbonate as by-products by carbon sequestration using coked ammonia distillation aqueous ammonia as claimed in claim 1, wherein The process condensed water is cooled to below 30℃ and then all returned to the remaining ammonia water tank, without wastewater discharge, realizing clean production.

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