Ammonium nitrate production wastewater treatment process

Abstract

The invention belongs to the technical field of wastewater treatment, and provides an ammonium nitrate production wastewater treatment process which is mainly composed of a neutralization tank, a tubular heat exchanger, a precision filter, a ceramic filter, a concentrated stock solution box, an ionic membrane concentration device, a desalination stock solution box, an ionic membrane desalination device, a reverse osmosis water inlet box, an RO security filter and a reverse osmosis device. The neutralization adjusting system enables the content of dilute nitric acid or free ammonia in the condensate to be reduced to the minimum, normal operation of subsequent treatment procedures is not affected, the condensate is filtered by the filter and then enters a concentrated stock solution box of the electrodialysis system, and stable and normal work of the electrodialysis system is ensured; the concentrated solution containing ammonium nitrate is collected by the concentrated solution box, and then is recycled to a factory area for production by the concentrated solution recycling pump; produced water enters a qualified water tank to serve as circulating water supplementary water, and concentrated liquid returns to an electrodialysis system to be treated again; recycled liquid is recycled, energy is saved, cost is saved, and environment friendliness is achieved.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment, and in particular relates to a process for treating ammonium nitrate production wastewater. Background Art

[0002] The production process of ammonium nitrate fertilizer products is to use dilute nitric acid and gaseous ammonia for neutralization reaction. A large amount of heat is released during the reaction. The size of the reaction heat is related to the concentration of nitric acid. The water in the neutralized solution absorbs heat and vaporizes, and finally a concentrated ammonium nitrate solution of about 75% is obtained. Further evaporation finally obtains ammonium nitrate fertilizer.

[0003] During the production of ammonium nitrate fertilizer products, the steam generated is condensed into condensate wastewater after condensation. The condensate wastewater contains usable ammonium nitrate and dilute nitric acid or free ammonia. If it is discharged directly, it will seriously pollute the environment and waste the recyclable substances. For this reason, manufacturers have put forward requirements for treatment and recycling; if the condensate waste liquid is allowed to directly enter the electrodialysis system, the ammonium nitrate and ammonia contained in the condensate waste liquid will damage the electrodialysis membrane stack and reduce the service life of the membrane stack; if the condensate waste liquid is discharged directly, it will cause a certain degree of water pollution because the water quality does not meet the standards. Summary of the invention

[0004] In order to solve the above problems, the present invention discloses a process for treating ammonium nitrate production wastewater.

[0005] To achieve the above object, the technical solution of the present invention is as follows: The present invention provides a process for treating ammonium nitrate production wastewater, which is mainly composed of a neutralization tank, a shell-and-tube heat exchanger, a precision filter, a ceramic filter, a concentrated stock liquid tank, an ion membrane concentrated device, a desalinated stock liquid tank, an ion membrane desalination device, a reverse osmosis water inlet tank, an RO security filter, and a reverse osmosis device, and specifically comprises the following steps: (1) Mixing ammonium nitrate production wastewater with gaseous ammonia and / or dilute nitric acid in a neutralization tank for neutralization reaction; (2) The wastewater produced in step (1) is transported to a shell-and-tube heat exchanger by a neutralization output pump for cooling to a temperature of <35°C; (3) The wastewater after cooling in step (2) is filtered through a precision filter and a ceramic filter to remove colloids, microorganisms, and suspended solid particles in the wastewater; (4) The wastewater after filtering in step (3) enters the concentrated stock liquid tank for electrodialysis; (5) The wastewater discharged from the concentrated liquid tank is input into the ion membrane concentration device under the action of the concentrated raw water pump. Under the action of the electrodialysis ion membrane, a stream of ammonium nitrate concentrate with a higher content and a stream of ammonium nitrate fresh water with a lower content are generated. The ammonium nitrate concentrate with a higher content is collected by the concentrated water tank and then recycled to the plant for production through the concentrated liquid recycling pump. The ammonium nitrate fresh water with a lower content enters the desalination liquid tank and is transported to the ion membrane desalination device through the desalination raw water pump. (6) The fresh water generated from the ion membrane desalination device enters the reverse osmosis water inlet tank, enters the RO safety filter through the reverse osmosis lift pump, and then enters the reverse osmosis device after being pressurized by the reverse osmosis high-pressure pump. Driven by pressure, the solute and solvent in the solution are separated. The generated fresh water enters the qualified water tank and is used as circulating water supplement water. The concentrated liquid returns to the desalination liquid tank for reprocessing.

[0006] Furthermore, the ammonium nitrate production wastewater is condensed wastewater obtained by condensing steam generated in the process of producing ammonium nitrate fertilizer products.

[0007] Furthermore, the pH of the ammonium nitrate production wastewater is 2-3.

[0008] Furthermore, the neutralization reaction time of step (1) is 0.5-2 hours, the pH value after the neutralization reaction is 4.5-5.5, and the temperature after the neutralization reaction is 65-75°C.

[0009] Furthermore, an automatic pH detector is arranged at the outlet of the neutralization tank, and a device for automatically adding ammonia and dilute nitric acid is arranged on the neutralization tank, and the amount of added ammonia or dilute nitric acid is automatically adjusted according to the data detected by the pH detector.

[0010] Furthermore, the nitric acid content in the ammonium nitrate production wastewater is 500-1000 ppm, and the ammonium nitrate content is 800-1500 ppm.

[0011] The process for treating ammonium nitrate production wastewater according to claim 1, characterized in that the pH of the water in the qualified water tank in step (6) is 6.5-8, ammonia nitrogen ≤5 mg / L, and ammonium nitrate ≤10 mg / L.

[0012] The beneficial effects of the present invention are: The neutralization and adjustment system of the present invention reduces the content of dilute nitric acid or free ammonia in the condensate to the minimum without affecting the normal operation of the subsequent treatment process. The colloidal substances, microorganisms, and suspended solid particles in the condensate are filtered through precision filters and ceramic filters and enter the concentrated stock liquid tank of the electrodialysis system to ensure the stability and normal operation of the electrodialysis system. The concentrated liquid containing ammonium nitrate of the present invention is collected by the concentrated concentrate tank and then reused in the factory for production through the concentrate reuse pump. The fresh water produced by the present invention enters the qualified water tank and is used as circulating water supplement water, and the concentrate returns to the electrodialysis system for reprocessing. The recovered liquid is reused to save energy, save costs, and be environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The present invention is a process flow chart of ammonium nitrate production wastewater treatment. DETAILED DESCRIPTION

[0014] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Example

[0015] like Figure 1 As shown, the present invention provides a process for treating ammonium nitrate production wastewater.

[0016] Flow rate and pollutant content of influent wastewater (1) Incoming wastewater flow According to the basic data provided by the factory, the water entering the ammonium nitrate wastewater treatment unit is the process condensate discharged from the 200,000 tons per year ammonium nitrate unit. The water volume is normally 14.4m 3 / h, maximum 17.2m 3 / h, the wastewater treatment plant is designed to operate 24 hours a day, so the designed treatment water volume is 18m 3 / h. 330 working days per year.

[0017] (2) Incoming wastewater quality According to the relevant basic data provided, the production wastewater is mainly ammonium nitrate condensation wastewater. Based on similar comparative analysis and combined with the wastewater quality discharged from other similar projects, the water quality of various types of wastewater is shown in Table 1 below. Table 1 Incoming wastewater quality table

[0018] Neutralization and adjustment system Since the ammonium nitrate condensate contains dilute nitric acid or free ammonia, if it directly enters the electrodialysis separation system, it will damage the electrodialysis membrane stack, reduce the service life of the membrane stack, and make it difficult for the discharged water to meet the standards, so it must be treated by the neutralization and adjustment system. The basic principle of the neutralization and adjustment system is: install an automatic ammonia and dilute nitric acid adding device when the ammonium nitrate condensate enters the neutralization tank, mix a small amount of gaseous ammonia or dilute nitric acid with the condensate and enter the neutralization tank, and a small amount of gaseous ammonia reacts with a small amount of nitric acid in the condensate to generate ammonium nitrate after the reaction, and the pH value rises to 4.5-5.5. The condensate stays in the neutralization tank for 1±0.5 hours, and automatically adjusts the amount of ammonia or dilute nitric acid added according to the data detected by the pH automatic detector at the outlet of the neutralization collection tank, so that the content of dilute nitric acid or free ammonia in the condensate is reduced to a minimum, without affecting the normal operation of the subsequent treatment process.

[0019] The condensate that has been neutralized and adjusted previously (temperature is 71±2℃) is pumped to the storage tank by the neutralization output pump, and then pumped to the shell-and-tube heat exchanger for cooling by the storage tank output pump, so that the temperature of the condensate drops to <35℃. The colloidal substances, microorganisms, and suspended solid particles in the condensate are filtered through precision filters and ceramic filters, and then enter the concentrated stock liquid tank of the electrodialysis system to ensure the stability and normal operation of the electrodialysis system.

[0020] Electrodialysis system The wastewater in the concentrated liquid tank is input into the ion membrane concentration device under the action of the concentrated liquid pump. Under the action of the electrodialysis ion membrane, a concentrated liquid with a higher content of ammonium nitrate and a fresh water with a lower content of ammonium nitrate are generated. The concentrated liquid with a higher content of ammonium nitrate is collected by the concentrated water tank and then recycled to the plant for production through the concentrated liquid recycling pump. The wastewater with a lower content of ammonium nitrate enters the desalination liquid tank and is lifted to the ion membrane desalination stage. The generated fresh water enters the reverse osmosis system, and the concentrated liquid is returned to the concentrated liquid tank for reprocessing.

[0021] Reverse Osmosis System The fresh water from the electrodialysis system enters the reverse osmosis water inlet tank, passes through the reverse osmosis booster pump and the reverse osmosis high-pressure pump for pressurization, and then enters the reverse osmosis system. Driven by pressure, the solute and solvent in the solution are separated by the selective interception effect of the reverse osmosis membrane. The generated fresh water enters the qualified water tank and is used as circulating water supplement water. The concentrated solution returns to the electrodialysis system for reprocessing; an RO safety filter is installed between the reverse osmosis booster pump and the reverse osmosis high-pressure pump.

[0022] The indicators of the treated wastewater are as follows: PH 6.5-8; temperature 35-40℃; pressure -0.6MPaG; ammonia nitrogen <5mg / L, ammonium nitrate <10mg / L, water output 16.7t / h. The clean water after the complete set of water treatment process equipment meets the circulating water supplementary water standard.

[0023] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A process for treating ammonium nitrate production wastewater, characterized in that: It is mainly composed of a neutralization tank, a shell-and-tube heat exchanger, a precision filter, a ceramic filter, a concentrated liquid tank, an ion membrane concentrated device, a desalinated liquid tank, an ion membrane desalination device, a reverse osmosis water inlet tank, a RO security filter, and a reverse osmosis device, and specifically includes the following steps: (1) Mixing ammonium nitrate production wastewater with gaseous ammonia and / or dilute nitric acid in a neutralization tank for neutralization reaction; (2) The wastewater produced in step (1) is transported to a shell-and-tube heat exchanger by a neutralization output pump for cooling to a temperature of <35°C; (3) The wastewater after cooling in step (2) is filtered through a precision filter and a ceramic filter to remove colloids, microorganisms, and suspended solid particles in the wastewater; (4) The wastewater after filtering in step (3) enters the concentrated stock liquid tank for electrodialysis; (5) The wastewater discharged from the concentrated liquid tank is input into the ion membrane concentration device under the action of the concentrated raw water pump. Under the action of the electrodialysis ion membrane, a stream of ammonium nitrate concentrate with a higher content and a stream of ammonium nitrate fresh water with a lower content are generated. The ammonium nitrate concentrate with a higher content is collected by the concentrated water tank and then recycled to the plant for production through the concentrated liquid recycling pump. The ammonium nitrate fresh water with a lower content enters the desalination liquid tank and is transported to the ion membrane desalination device through the desalination raw water pump. (6) The fresh water generated from the ion membrane desalination device enters the reverse osmosis water inlet tank, enters the RO safety filter through the reverse osmosis lift pump, and then enters the reverse osmosis device after being pressurized by the reverse osmosis high-pressure pump. Driven by pressure, the solute and solvent in the solution are separated. The generated fresh water enters the qualified water tank and is used as circulating water supplement water. The concentrated liquid returns to the desalination liquid tank for reprocessing.

2. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: The ammonium nitrate production wastewater is condensed wastewater obtained by condensing the steam generated in the process of producing ammonium nitrate fertilizer products.

3. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: The pH of the ammonium nitrate production wastewater is 2-3.

4. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: The neutralization reaction time of step (1) is 0.5-2 hours, the pH value after the neutralization reaction is 4.5-5.5, and the temperature after the neutralization reaction is 65-75°C.

5. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: An automatic pH detector is arranged at the outlet of the neutralization tank, and a device for automatically adding ammonia and dilute nitric acid is arranged on the neutralization tank. The amount of added ammonia or dilute nitric acid is automatically adjusted according to the data detected by the pH detector.

6. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: The nitric acid content in the ammonium nitrate production wastewater is 500-1000ppm, and the ammonium nitrate content is 800-1500ppm.

7. A process for treating ammonium nitrate production wastewater according to claim 1, characterized in that: The pH of the water in the qualified water tank in step (6) is 6.5-8, ammonia nitrogen ≤ 5 mg / L, and ammonium nitrate ≤ 10 mg / L.

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