Method for ammonia distillation pretreatment of byproduct ammonia water in coal chemical industry

Abstract

The invention belongs to the field of chemical product purification processes, and particularly relates to an ammonia distillation pretreatment method for byproduct ammonia water in the coal chemical industry. Ammonia-containing wastewater enters a two-stage ceramic filter after being pressurized by a pressure pump and then is connected with a multi-medium filter, a multi-medium outlet enters an anion adsorption tank after being pressurized by a pipeline pump, the adsorption tank adopts a one-open and one-standby mode, an online pH monitoring device is arranged at the outlet, and the resin tank saturated by adsorption is analyzed by sodium hydroxide under specific conditions. The desorption solution is recycled, and finally the wastewater enters an ammonia distillation section. According to the method, pollutants are efficiently removed, the TDS of the treated wastewater is reduced to 1000 or below, the treatment process is continuous, the cost is low, high economic benefits and environmental protection benefits are achieved, the process is optimized, alkali is not added during ammonia distillation, the steam consumption is reduced, the ammonia distillation operation cost is reduced, and the TDS of the ammonia distillation wastewater is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the field of purification processes for chemical products, and particularly relates to a method for pre-steaming ammonia of by-product ammonia water in coal chemical industry. Background Art

[0002] In the ammonia evaporation towers of coal gasification and coking plants, due to the poor quality of the raw material ammonia-containing wastewater, a large amount of impurities enter the ammonia evaporation system without treatment, resulting in the blockage of the ammonia evaporation tower. Some substances such as tar residues sticking inside the ammonia evaporation tower will also greatly increase the maintenance time. Chloride ions and other pollutants dissolved in water will also cause an increase in the energy consumption of the ammonia evaporation tower.

[0003] Anionic impurities such as chloride ions and carbonate ions contained in the ammonia-containing wastewater convert the free ammonia in the ammonia-containing wastewater into fixed ammonia, resulting in the need to add a large amount of sodium hydroxide in the ammonia evaporation process to improve the ammonia evaporation capacity of the ammonia evaporation tower and reduce the ammonia nitrogen content of the ammonia-containing wastewater.

[0004] Currently, the pre-treatment before ammonia evaporation cannot effectively reduce the TDS and COD in the ammonia water. Existing pre-treatment devices such as ceramic filters can only filter out some solid impurities and cannot separate other impurities dissolved in water such as chloride ions in the ammonia-containing wastewater. Summary of the Invention

[0005] The object of the present invention is to provide a method for pre-steaming ammonia of by-product ammonia water in coal chemical industry, which can improve the ammonia evaporation efficiency of ammonia-containing wastewater in coal chemical industry, recycle the sodium hydroxide solution for the second analysis, reduce the steam consumption, reduce the operation cost of ammonia evaporation, and greatly reduce the TDS of the ammonia evaporation wastewater.

[0006] The specific implementation scheme of the present invention is as follows: (1) The ammonia-containing wastewater first enters a two-stage ceramic filter after being pressurized by a booster pump. The temperature is not limited, and the pressure is controlled at 0.4 - 0.6 MPa. Among them, the filtration accuracy of the first-stage ceramic filter is 5 microns, and the filtration accuracy of the second-stage ceramic filter is 0.5 microns. The outlet pressure of the ammonia-containing wastewater after two-stage filtration is 0.3 MPa. Through the setting of the two-stage ceramic filter, the suspended solids and colloidal substances in the wastewater can be effectively removed, improving the clarity of the wastewater and providing good conditions for subsequent treatment.

[0007] (2) The outlet of the ceramic filter is directly connected to a multi-media filter. The inlet pressure of the multi-media filter is not less than 0.2 MPa. A variety of filtering media are filled in the multi-media filter, and the filtering media are quartz sand, anthracite, and activated carbon.

[0008] (3) The multi-media outlet uses a pipeline pump to increase the pressure to 0.3 MPa and enters the anion adsorption tank. The anion adsorption tank is filled with anion resin. The adsorption tanks are arranged in a one-use-one-spare mode to ensure the continuity of the treatment process. The filtration rate is 0 - 1.5 BV. An on-line pH monitoring device is set at the outlet. When the pH is lower than 12, it is switched to the standby resin tank. The resin tank saturated with adsorption is desorbed with 2% - 4% sodium hydroxide at a temperature of 50 - 60 °C. 50% of the desorbed sodium hydroxide solution is recycled for the second desorption. The dosage of sodium hydroxide is 3 times the resin filling volume, and the desorption liquid flow rate is 1 - 3 BV.

[0009] (4) The ammonia-containing wastewater from the outlet of the anion adsorption tank enters the ammonia distillation section. The concentrated ammonia water generated by the ammonia distillation tower no longer contains acidic impurities. The TDS of the ammonia distillation wastewater is reduced from the original 3000 - 5000 to less than 1000, reducing the load on the biochemical treatment of the wastewater.

[0010] The above operations make it no longer necessary to add sodium hydroxide solution for ammonia distillation, while reducing the steam consumption. Compared with the traditional load, the TDS of the generated ammonia distillation wastewater is significantly reduced, reducing the load on the biochemical treatment of the wastewater.

[0011] The present invention has the following advantages compared with the existing technologies: After the ammonia-containing wastewater is purified in three stages in sequence by the process of the present invention, the ammonia-containing wastewater no longer contains oil substances such as tar drops that can cause blockage of the ammonia distillation tower, and all the fixed ammonia is replaced by free ammonia, greatly improving the ammonia distillation efficiency of the ammonia distillation tower. The process is optimized, no alkali is added for ammonia distillation, the steam consumption is reduced, the operation cost of ammonia distillation is reduced, and the TDS of the ammonia distillation wastewater is greatly reduced. Specific Embodiments

[0012] The technical solutions and their effects of the present invention are further described below through specific embodiments. Embodiment

[0013] The specific implementation method is as follows: (1) The ammonia-containing wastewater first passes through a pressure pump to increase the pressure and then enters two-stage ceramic filters. The temperature is not limited, and the pressure is controlled at 0.4 - 0.6 MPa. Among them, the filtration accuracy of the first-stage ceramic filter is 5 microns, and the filtration accuracy of the second-stage ceramic filter is 0.5 microns. The outlet pressure of the ammonia-containing wastewater after two-stage filtration is 0.3 MPa. Through the setting of the two-stage ceramic filters, the suspended solids and colloidal substances in the wastewater can be effectively removed, improving the clarity of the wastewater and providing good conditions for subsequent treatment.

[0014] (2) The outlet of the ceramic filter is directly connected to the multi-media filter. The inlet pressure of the multi-media filter is not less than 0.2 MPa. The multi-media filter is filled with various filtering media such as quartz sand, anthracite, activated carbon, etc., which can further remove fine particles and organic matters in the wastewater and improve the filtering effect of the wastewater.

[0015] (3) The pressure is increased to 0.3 MPa by a pipeline pump at the outlet of the multi-media filter and then enters the anion adsorption tank. The anion adsorption tank is filled with anion resin. The adsorption tanks are operated in a one-open-one-standby mode to ensure the continuity of the treatment process. The filtration rate is 0 - 1.5 BV. An on-line pH monitoring device is set at the outlet. When the pH is lower than 12, it is switched to the standby resin tank. The resin tank saturated with adsorption is desorbed with 2% - 4% sodium hydroxide at a temperature of 50 - 60 degrees Celsius. 50% of the recovered sodium hydroxide solution is used for the second desorption. The dosage of sodium hydroxide is 3 times the resin filling amount. The flow rate of the desorption liquid is 1 - 3 BV. Through the treatment of the anion adsorption tank, anion pollutants such as ammonia nitrogen in the wastewater can be effectively removed, improving the purification degree of the wastewater. At the same time, the maximum recycling of the sodium hydroxide solution during the desorption process reduces the treatment cost and reduces the pollutant emissions.

[0016] (4) The ammonia-containing wastewater at the outlet of the anion adsorption tank enters the ammonia distillation section. The concentrated ammonia water produced by the ammonia distillation tower no longer contains acidic impurities. The TDS of the ammonia-distilled wastewater is reduced from the original 3000 - 5000 to less than 1000, reducing the load on the wastewater biochemical treatment system. The above operations make it no longer necessary to add sodium hydroxide solution during ammonia distillation, while reducing the steam consumption. Compared with the traditional load, the TDS of the produced ammonia-distilled wastewater drops significantly, reducing the load on the wastewater biochemical treatment.

Claims

1. A method for pre-treatment of ammonia distillation of by-product ammonia water in coal chemical industry, characterized in that The specific steps are as follows: (1) The ammonia-containing wastewater first enters two-stage ceramic filters after being pressurized by a pressure pump. The temperature is not limited, and the pressure is controlled at 0.4 - 0.6 MPa. Among them, the filtration accuracy of the first-stage ceramic filter is 5 microns, and the filtration accuracy of the second-stage ceramic filter is 0.5 microns. The outlet pressure of the ammonia-containing wastewater after two-stage filtration is 0.3 MPa. After being filtered by the two-stage ceramic filters, suspended solids and colloidal substances in the wastewater are effectively removed; (2) The outlet of the ceramic filter is directly connected to a multi-media filter. The inlet pressure of the multi-media filter is not less than 0.2 MPa, and the multi-media filter is filled with a variety of filter media; (3) The pressure of the multi-media outlet is increased to 0.3 MPa by a pipeline pump and enters the anion adsorption tank. The anion adsorption tank is filled with anion resin. The adsorption tank adopts a one-open-one-standby method to ensure the continuity of the treatment process. The filtration speed is 0 - 1.5 BV. An on-line pH monitoring device is set at the outlet. When the pH is lower than 12, it is switched to the standby resin tank. The resin tank saturated with adsorption is desorbed with 2% - 4% sodium hydroxide at a temperature of 50 - 60 degrees Celsius. The desorbed sodium hydroxide solution is recycled for the second desorption. The maximum recycling of the sodium hydroxide solution is carried out during the desorption process, and no additional sodium hydroxide solution is required for ammonia distillation; (4) The ammonia-containing wastewater at the outlet of the anion adsorption tank enters the ammonia distillation section. The concentrated ammonia water generated by the ammonia distillation tower no longer contains acidic impurities, and the TDS of the ammonia-distilled wastewater is reduced from the original 3000 - 5000 to less than 1000.

2. The method for pre-treatment of ammonia distillation of by-product ammonia water in coal chemical industry according to claim 1, characterized in that The filter media described above are quartz sand, anthracite, and activated carbon.

3. A method for pre-steaming ammonia from by-product ammonia water in coal chemical industry according to claim 1, characterized in that 50% of the desorbed sodium hydroxide solution is recycled for the second desorption. The dosage of sodium hydroxide is 3 times the resin filling amount, and the desorption liquid flow rate is 1 - 3 BV.