Generation and analysis of ammonia-alkali waste residue liquid, waste water, and waste gas

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This post was last edited by yanshan86 on 2010-11-3 10:53 ⑴ In the brine refining process, Mg2+ and Ca2+ react in crude brine to generate Mg(OH)2 and CaCO3 to form salt cement. The salt cement is mixed with the distillation waste liquid and discharged through clarification or pressure filtration as the waste liquid (L1), and the solid slag (S1) is stored. The production amount and chemical composition of salt cement vary depending on the Mg2+ and Ca2+ content in the original salt. The amount of salt cement produced is about 1.1-1.2m3/t alkali, which contains solid residue of about 60kg/t alkali (dry basis). The solid content (S1) contains approximately 11.55% calcium sulfate, approximately 58.5% calcium carbonate, and approximately 19.5% magnesium hydroxide. Others include 2.07% acid-insoluble matter, 2.11% mixed oxides, and 6.27% others. When the Ca2+ and Mg2+ impurities in the raw salt are high, it is more economical to use the lime ammonium bicarbonate method to refine the brine. However, the brine waste sludge produced by the lime ammonium bicarbonate method to refine the brine contains ammonia, and its concentration and emissions are related to the amount of calcium removal and the level of operation. There is no ammonia loss in brine refining using the lime soda ash method, but when the Ca2+ and Mg2+ impurities in the raw salt are high, the operating cost is high due to the use of product soda ash. ⑵Limestone calcining process: Limestone is calcined to produce kiln gas containing carbon dioxide. The kiln gas needs to be dusted and cooled by a scrubber, an electric precipitator, and a cooling tower before being sent to the carbonization workshop for alkali production. The amount of washing water produced is about 8m3/ton of soda ash (L2), which contains dust, coal tar, etc. ； After digestion, the lime is used for mother liquor distillation and brine refining. In the ashing process, due to the quality of limestone, coke or white coal, some sand and other debris will inevitably be produced. After separation, it can be used for construction and paving (S2). ⑶Steaming and absorbing ammonia process: Ammonia distillation is a main process in the production of soda ash by the ammonia-alkali method. The purpose is to use refined brine to recover ammonia and carbon dioxide in the filtered mother liquor to produce ammonia brine for soda ash production. The total ammonia in the mother liquor is divided into free ammonia and fixed ammonium. Fixed ammonium must be added to gray milk before it can be decomposed. The ammonia evaporation process produces distillation waste liquid. The distillation waste liquid is discharged after clarification or pressure filtration as waste liquid (L1), and the solid residue (S1) is stored. The distillation waste residue liquid is about 10m3/ton of soda ash, containing about 200-300 kg of solid waste residue (dry basis). The solids in the waste residue liquid basically come from lime milk, and the amount of waste residue generated depends on the quality of the limestone, the effective decomposition rate of the limestone after calcination, etc. The pH of ammonia-alkali waste residue is <12.5, which is a general solid waste. In order to ensure the recovery rate of ammonia and reduce the ammonia nitrogen concentration in the discharged waste liquid, it is necessary to maintain a surplus of gray milk. The waste residue liquid contains approximately 2 titers of excess ash, and the waste serum liquid contains approximately 800 mg/l Ca(OH)2. After clarification and other treatments, the pH value of the waste liquid is generally between 11 and 11.5, which contains about 55 g/l NaCl, about 100 g/l CaCl2, and about 70 mg/l ammonia. The factors that affect the ammonia content of the waste liquid are relatively complex. The main factors include the operating period of the ammonia distillation tower, the component fluctuation of the mother liquor, the composition fluctuation of the gray milk, the relative amounts of the mother liquor and the gray milk, etc., which are closely related to the equipment level, the automation control level of the production process, and the quality of the raw materials. (4) Ammonia evaporation condensate, heavy alkali calciner gas condensate and equipment cleaning, maintenance, leakage, etc. cause the mother liquor containing high ammonia concentration to be distilled into dilute liquid, and the waste dilute liquid (L3) after ammonia recovery enters the sewage discharge system.