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CN-118145676-B - Method for desulfurizing acid radical and recycling ammonium chloride and sodium chloride from deamination mother solution separated by multi-effect evaporation crystallization

CN118145676BCN 118145676 BCN118145676 BCN 118145676BCN-118145676-B

Abstract

The invention discloses a method for desulfurizing a deamination mother solution and recovering ammonium chloride and sodium chloride through multiple-effect evaporation crystallization, which comprises the following steps of 1) collecting deamination mother solution, 2) carrying out primary cold precipitation, namely conveying the deamination mother solution into a normal-temperature ammonium precipitation kettle, cooling to 25-28 ℃ for cold precipitation crystallization, centrifuging to obtain ammonium chloride and a first mother solution for agriculture, 3) carrying out secondary cold precipitation, namely conveying the first mother solution into a cold precipitation crystallization kettle, adding sodium chloride, cooling to 20-23 ℃ for cold precipitation crystallization, centrifuging to obtain ammonium chloride for agriculture and a second mother solution, 4) carrying out tertiary cold precipitation, namely conveying the second mother solution into a strong cold precipitation kettle, cooling to 0-5 ℃ for crystallizing and precipitating sodium sulfate decahydrate, centrifuging to obtain the mother solution of sodium sulfate decahydrate and sodium chloride, and 5) returning the sodium chloride to a multiple-effect evaporation system for recovering sodium chloride. According to the invention, the deamination mother liquor is treated by a three-time cold-precipitation crystallization method, instead of directly returning the deamination mother liquor to a multi-effect evaporation system for recycling, the phenomenon that the sulfate radical content in the salt exceeds the standard caused by malignant recycling accumulation of the sulfate radical due to high sulfate radical content in the deamination mother liquor and repeated recycling can be effectively avoided, the sulfate radical content in the recovered industrial salt reaches the standard of GB/T5462-2015 industrial salt, and the product quality of the industrial salt is improved.

Inventors

  • TENG LONG
  • LIU SONGLIN
  • WANG SHANG
  • Zhong Linhui
  • LI YUEMING

Assignees

  • 衡阳爱洁科技股份有限公司

Dates

Publication Date
20260512
Application Date
20240126

Claims (7)

  1. 1. A method for desulfurizing the deamination mother liquid and recovering ammonium chloride and sodium chloride by multiple-effect evaporation crystallization is characterized by comprising the following steps of 1) collecting deamination mother liquid, 2) carrying out primary cold precipitation, namely conveying the deamination mother liquid into an ammonium precipitation kettle at normal temperature, cooling to 25-28 ℃ for cold precipitation crystallization, centrifuging to obtain ammonium chloride and a mother liquid I for agriculture, 3) carrying out secondary cold precipitation, namely conveying the mother liquid I into a cold precipitation crystallization kettle, adding sodium chloride, cooling to 20-23 ℃ for cold precipitation crystallization, centrifuging to obtain ammonium chloride and a mother liquid II for agriculture, 4) carrying out tertiary cold precipitation, namely conveying the mother liquid II into a strong cold precipitation kettle, cooling to 0-5 ℃ for crystallizing and precipitating sodium sulfate decahydrate, centrifuging to obtain sodium sulfate decahydrate and a mother liquid, and 5) returning sodium chloride to a multiple-effect evaporation system for recovering sodium chloride.
  2. 2. The method for desulfurizing and recovering ammonium chloride and sodium chloride from deamination mother liquor separated by multiple-effect evaporation and crystallization as claimed in claim 1, wherein the deamination mother liquor in the step 1) is mother liquor obtained by firstly adopting a distillation method to deaminize, then adopting a multiple-effect evaporation method to extract sodium chloride from the deaminated mother liquor, and finally adopting a flash evaporation vacuum cooling method to precipitate ammonium chloride and centrifugally dewatering and separating.
  3. 3. The method for desulfurizing an ammonia-free mother liquor and recovering ammonium chloride and sodium chloride by multi-effect evaporation and crystallization separation according to claim 1, wherein the cold separation crystallization time after the ammonia-free mother liquor is cooled to 25-28 ℃ in the step 2) is 4-6h.
  4. 4. The method for desulfurizing an ammonia-free mother liquor and recovering ammonium chloride and sodium chloride according to claim 1, wherein the cold separation crystallization time of the mother liquor after the mother liquor is cooled to 20-23 ℃ in the step 3) is 2-4h.
  5. 5. A process for desulfurizing an ammonia-free mother liquor and recovering ammonium chloride and sodium chloride according to claim 1, wherein the addition amount of sodium chloride is =the content of ammonium chloride in mother liquor A. Times.0.6.
  6. 6. The method for desulfurizing and recovering ammonium chloride and sodium chloride from deaminated mother liquor separated by multi-effect evaporation and crystallization according to claim 1, wherein the cold separation crystallization time of the mother liquor after the second temperature of the mother liquor is reduced to 0-5 ℃ in the step 4) is 2-4h.
  7. 7. The method for desulfurizing and recovering ammonium chloride and sodium chloride from deaminated mother liquor separated by multi-effect evaporation crystallization according to any one of claims 1-6, wherein the normal temperature ammonium precipitation kettle, the cold precipitation crystallization kettle and the forced cold precipitation kettle are all provided with jackets, and cooling water is injected into the jackets to reduce the temperature of the solution in the kettle.

Description

Method for desulfurizing acid radical and recycling ammonium chloride and sodium chloride from deamination mother solution separated by multi-effect evaporation crystallization Technical Field The invention relates to the technical field of deamination mother liquor treatment obtained by separating ammonium chloride recovered from baking soda mother liquor, in particular to a method for desulfurizing acid radicals and recovering ammonium chloride and sodium chloride in deamination mother liquor separated by multi-effect evaporation and crystallization. Background The mother liquor of sodium bicarbonate is obtained by washing, dehydrating and separating sodium bicarbonate in the process of preparing sodium bicarbonate by taking brine and ammonium bicarbonate as raw materials, and contains a large amount of ammonium chloride, sodium chloride and ammonium bicarbonate, so that the ammonium chloride and the sodium chloride can be recycled from the mother liquor, waste materials can be changed into things of value, and the environment is protected. At present, the method for recovering ammonium chloride from sodium bicarbonate mother liquor adopts an ammonia distillation tower for deamination, and then adopts a multi-effect evaporation cooling crystallization method, for example, patent application number CN200910068695.6 discloses a process method for recovering ammonium chloride and sodium chloride from wastewater containing ammonium chloride and sodium chloride, which takes the mother liquor containing ammonium chloride and sodium chloride generated in the process of producing sodium bicarbonate by double decomposition reaction of a natural brine method as raw materials to produce ammonium chloride and sodium chloride. Adopts ammonia distillation, evaporation, crystallization and separation processes. The evaporation adopts multiple-effect, heat pump and vacuum evaporation processes, a falling film evaporator and a forced circulation evaporator are selected, three-effect mixed flow process is adopted, sodium chloride is separated out in the evaporation, and the ammonium chloride is separated out after the evaporation by cooling crystallization. When the ammonium chloride is recovered from the sodium bicarbonate mother solution, the salt in the mother solution is extracted by adopting a multi-effect evaporation method after the sodium bicarbonate mother solution is subjected to deamination, the ammonium chloride is separated out from the mother solution obtained by recovering the salt by adopting a flash evaporation vacuum cooling method, the ammonium chloride and the deamination mother solution are obtained after the ammonium chloride is subjected to liquid removal by a centrifugal machine, and the deamination mother solution is returned to a multi-effect evaporation system for recycling. However, in the practical application process, when the deamination mother liquor is returned to a multi-effect evaporation system for repeated recycling, the content of SO4 2- is continuously accumulated, the content of SO 42- is increased by 10-15 times after repeated recycling for 10 times, and the increase of SO 42- is caused by the fact that in order to avoid that the ammonium chloride cannot meet the standard of agricultural ammonium chloride due to too much Na 2SO4 entering the ammonium chloride, the characteristic that the solubility of sodium sulfate is the largest at 40-45 ℃ is utilized in the vacuum cooling crystallization process, SO that the sodium sulfate is separated from the ammonium chloride and the ammonium chloride is crystallized and separated out, a large amount of sodium sulfate returns to the evaporation system along with the mother liquor, when SO 42- is accumulated to Na 2SO4 to be saturated, na 2SO4 and NaCl are co-precipitated, SO that the content of SO 42- in the recovered salt exceeds the standard, the standard of GB/T5462-2015 industrial salt cannot be met, and the quality of industrial salt is seriously reduced. Disclosure of Invention The invention aims to solve the technical problems of overcoming the defects of the prior art and providing a method for desulfurizing acid radicals and recycling ammonium chloride and sodium chloride in deamination mother liquor which is simple in process and can effectively reduce sulfate radical content and is separated by multi-effect evaporation crystallization. The invention solves the technical problems by adopting the technical scheme that the method comprises the steps of 1) collecting deamination mother liquor, 2) carrying out primary cold precipitation, namely conveying the deamination mother liquor into an ammonium precipitation kettle at normal temperature, cooling to 25-28 ℃ for cold precipitation crystallization, centrifuging to obtain agricultural ammonium chloride and mother liquor I, 3) carrying out secondary cold precipitation, namely conveying the mother liquor I into a cold precipitation crystallization kettle, adding sodium chloride, cooling