CN109879297B - Process for thermal recovery of products from mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate - Google Patents
Process for thermal recovery of products from mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate Download PDFInfo
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Abstract
The process for recovering the product from the mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate by a thermal method comprises the following steps of: preheating mother liquor, then sending the mother liquor into an ammonia still for deamination, sending carbon dioxide and ammonia gas generated after deamination into an ammonia absorption tower to generate carbon-containing ammonia water, and adding carbon dioxide into the carbon-containing ammonia water to enable the carbon dioxide to be excessive and generate ammonium bicarbonate. The process also comprises the following steps of recovering the deaminated mother liquor and obtaining ammonium chloride and sodium chloride: carrying out five-effect cross-flow evaporation to obtain sodium chloride, carrying out four-effect flash crystallization to obtain ammonium chloride, throwing the overflow liquid of the salt thickener and the salt centrifuge into a V-effect evaporation tank, and participating in circulation again; and pumping the overflowed liquid of the ammonium thickener and the thrown liquid of the ammonium centrifugal machine into an IV-effect flash crystallizing tank by using a pump, and participating in production circulation again. The process can simultaneously recover ammonium chloride and sodium chloride, has extremely high recovery rate, and can effectively improve the heat utilization rate.
Description
Technical Field
The invention relates to the technical field of mixed mother liquor recovery, in particular to a process for recovering products from mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate by a thermal method.
Background
The production method comprises the steps of taking brine and ammonium bicarbonate as raw materials, producing baking soda by adopting a double decomposition reaction, and producing a large amount of mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate in the production process of the baking soda, wherein in addition, the heavy soda filtration mother liquor (generally called soda production mother liquor) obtained in the soda production process also contains the four components, and the component content of the heavy soda filtration mother liquor is slightly different from that of the mother liquor (generally called baking soda production mother liquor) obtained after the baking soda is produced by the double decomposition.
At present, the above mother liquor treatment methods include the following two methods:
the first method is a cold method for recovering ammonium chloride, and the process is that the mother liquor is frozen and cooled, then solid sodium chloride is added, and the ammonium chloride is separated by cooling and salting out. The method has the advantages of large-scale production, mature process technology and stable product quality. However, the method needs to select high-quality solid salt as a raw material, so that the cost is high, the energy consumption during freezing is high, the investment amount is large, and the recovery period is long.
The second method is a 'hot method' for recovering ammonium chloride, which overcomes the defect of a 'cold method', an evaporation method is adopted to concentrate the mother liquor, and the ammonium chloride and the sodium chloride are respectively separated out by utilizing the different solubility along with the temperature change relationship, thereby achieving the purpose of separation; the method can recover ammonium chloride and refined salt sodium chloride without adding sodium chloride during treatment.
Chinese patent publication No. CN 101544437 a discloses a process for recovering ammonium chloride and sodium chloride from wastewater containing ammonium chloride and sodium chloride, which uses mother liquor generated in the process of producing sodium bicarbonate by natural brine double decomposition reaction as raw material to produce ammonium chloride and sodium chloride, and adopts ammonia distillation, evaporation, crystallization and separation processes for treatment. The evaporation adopts multiple-effect, heat pump and vacuum evaporation processes, a falling film evaporator and a forced circulation evaporator are selected, and a three-effect mixed flow process is adopted, so that sodium chloride is crystallized and separated out in the evaporation, and ammonium chloride is crystallized and separated out after the evaporation and the cooling. The invention adopts the three-effect mixed flow evaporation and two-effect salting-out process, and the process has the problems of high energy consumption, high cost, low product purity caused by co-precipitation of ammonium chloride and sodium chloride, unreasonable type selection of an evaporation tank and the like. This patent is doing the deamination and is handled the back, does not recycle the ammonia, not only causes the pollution to the environment, has wasted the resource moreover, and the rate of recovery is also low.
The Chinese patent with publication number 102992353A discloses a process for producing industrial-grade ammonium chloride by an IV-effect evaporative heat method, which comprises the steps of feeding sodium bicarbonate production mother liquor into an ammonia still for deamination, feeding ammonia gas into a washing tower, feeding tail gas into a condenser for condensation to obtain ammonia water, sequentially feeding the ammonia water to the IV, III, II and I effects of a multi-effect evaporation system in a counter-current feeding mode, crystallizing ammonium chloride, washing slurry, dehydrating and drying to obtain a product. This patent has a number of disadvantages: 1. the ammonia water obtained by condensing the deaminated tail gas has low concentration and large equivalent weight, contains a large amount of carbon dioxide and has low practical value; 2. The countercurrent feeding is adopted for multi-effect evaporation, and the solution flows from low pressure to high pressure in the effect room and must be conveyed by a pump; 3. after the high-temperature mother liquor enters the final effect, the temperature is reduced quickly, the generated secondary steam cannot be reused, and the heat utilization rate is not high; 4. the heat exchange of a multi-stage preheater is adopted in the process, particularly, a condensate water preheater and the like have limited effects, but the frequency of mother liquor blockage is increased, and the heat exchange is not feasible in the actual industrial production process.
Disclosure of Invention
The invention aims to provide a process for recovering products from mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate by a thermal method, which can effectively improve the heat utilization rate and has extremely high recovery rate.
In order to solve the problems, the following technical scheme is adopted: the process for thermally recovering products from mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate comprises a method for recovering gas generated after deamination of the mother liquor and a method for recovering the mother liquor after deamination and obtaining ammonium chloride and sodium chloride, wherein when the mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate is the mother liquor obtained after double decomposition for producing sodium bicarbonate, the method for recovering the gas generated after deamination of the mother liquor comprises the following steps: pumping mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate into a primary condensate water heat exchanger of the original mother liquor, and heating the mother liquor to 35-40 ℃ by V-effect evaporation condensate water; then the mother liquor enters a secondary condensate water heat exchanger of the original mother liquor, and the mother liquor is heated to 55-60 ℃ by I-effect evaporation condensate water; then enters a third-stage heat exchanger of the original mother liquor, the mother liquor is heated to 65-70 ℃ and then enters an ammonia still, the temperature of the lower part of the ammonia still is controlled to be 105-120 ℃, and the ammonium bicarbonate is prepared by using the cooled mixed gas of ammonia and carbon dioxide generated in the deamination process, which comprises the following specific steps: sending the mixed gas of ammonia and carbon dioxide into an ammonia absorption tower, and absorbing the ammonia gas and the carbon dioxide by water to generate carbon-containing ammonia water; feeding carbon-containing ammonia water into a carbonization tower, washing carbon dioxide tail gas which is not absorbed by water in an ammonia absorption tower, pressurizing by a compressor, feeding into the carbonization tower, supplementing food-grade carbon dioxide which accounts for 15-20% of the total amount of the required carbon dioxide into the carbonization tower in time to enable the carbon dioxide to be excessive, reacting with the carbon-containing ammonia water in the carbonization tower to generate ammonium bicarbonate crystals, decompressing and leading out reaction liquid from the carbonization tower, feeding into a thickener for concentration, feeding bottom liquid of the thickener into a centrifugal machine for solid-liquid separation, and drying to obtain a food-grade ammonium bicarbonate product.
The method for recovering the deaminated mother liquor and obtaining ammonium chloride and sodium chloride comprises the following steps:
A. pumping the deaminated mother liquor from an ammonia still into a II-effect evaporation tank through a pump for heating and evaporation, wherein the temperature of the solution is controlled to be 102-108 ℃; after evaporation and concentration, mother liquor is discharged into a III-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 80-86 ℃; after evaporation and concentration, mother liquor is discharged into an IV-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 64-70 ℃; after evaporation and concentration, mother liquor is discharged into a V-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 45-50 ℃; after evaporation and concentration, the mother solution and the precipitated crystals are pumped into an I-effect evaporation tank for heating and evaporation, and the temperature of the solution is controlled to be 120-129 ℃; after evaporation concentration, washing sodium chloride crystals separated out from the I-effect evaporation tank, discharging, thickening by a salt thickener, then dewatering in a centrifuge, and drying sodium chloride obtained after centrifugal dewatering to obtain a product;
B. discharging the evaporation concentrated solution of sodium chloride crystals separated from the first-effect evaporation tank to the first-effect flash tank; after flash evaporation and concentration, mother liquor is discharged into a second-effect flash tank; after flash evaporation and concentration, mother liquor is discharged into a III-effect flash tank in a downstream manner; after flash crystallization, discharging the mother liquor and the crystals to an IV-effect flash crystallization tank; after flash crystallization, conveying ammonium chloride crystals to an ammonium thickener by a pump, dehydrating the base solution of the ammonium thickener by a centrifugal machine to obtain wet ammonium chloride, and drying the wet ammonium chloride to obtain a dry ammonium chloride product;
C. throwing the overflow liquid of the salt thickener and the liquid obtained after salt centrifugal machine into a liquid barrel after salt throwing, pumping the liquid into a V-effect evaporation tank by a pump, and participating in circulation again; the overflow liquid of the ammonium thickener and the liquid thrown by the ammonium centrifuge enter an ammonium thrown liquid barrel, and are sent into an IV-effect flash crystallization tank by a pump to participate in production circulation again;
secondary steam of the first-effect flash tank enters a heating chamber of a third-effect evaporation tank for heat exchange in the ammonium chloride flash process, secondary steam of the second-effect flash tank enters a heating chamber of a fourth-effect evaporation tank for heat exchange, secondary steam of the third-effect flash tank enters a heating chamber of a fourth-effect evaporation tank for heat exchange, and secondary steam of the fourth-effect flash crystallization tank enters an indirect condenser for condensing with circulating water;
raw steam from a boiler is sent into a heating chamber of an I-effect evaporation tank, secondary steam generated by the evaporation chamber of the I-effect evaporation tank is sent into the heating chamber of a II-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the II-effect evaporation tank is sent into a heating chamber of a III-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the III-effect evaporation tank is sent into a heating chamber of a IV-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the IV-effect evaporation tank is sent into a heating chamber of a V-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the;
the condensed water in the heating chamber of the I-effect evaporation tank is discharged into the I-effect condensation bucket, the condensed water is pumped into the primary mother liquid secondary condensed water heat exchanger, after the mother liquid is heated, the condensed water is sent back to the boiler for recycling, the condensed water in the heating chamber of the II-effect evaporation tank is discharged into the II-effect condensation bucket, then the condensed water in the heating chamber of the III-effect evaporation tank is discharged into the III-effect condensation bucket and the condensed water after the II-effect flash, the condensed water in the heating chamber of the IV-effect evaporation tank is discharged into the IV-effect condensation bucket and the condensed water after the III-effect flash, the condensed water in the heating chamber of the V-effect evaporation tank is discharged into the V-effect condensation bucket and the condensed water after the IV-effect flash are pumped into the primary condensed water heat exchanger of the primary mother liquid and then discharged outside.
Preferably, the ammonia still is an indirect steam heating type sieve plate tower.
Preferably, the ammonia absorption tower is a circulating cooling bubble column.
Preferably, the carbonization tower is a sieve plate tower with a cooling section.
Preferably, the I-V effect evaporation tanks are external heating type forced circulation axial feeding evaporation tanks, and each I effect evaporation tank is provided with a jacket with a clear liquid separation function.
Preferably, the I-III effect flash tanks are all forced circulation axial feeding flash tanks, the IV effect flash crystallization tank is a forced circulation axial feeding flash crystallization tank, and the IV effect flash crystallization tank is provided with a jacket with a clear liquid separation function.
Preferably, the pressure of the evaporation chamber of the I-effect evaporation tank is controlled to be 1.65-1.7kg/cm2The pressure of the evaporation chamber of the II-effect evaporation tank is controlled to be 0.69-0.75kg/cm2The pressure of the evaporation chamber of the III-effect evaporation tank is controlled to be 0.38-0.44kg/cm2The pressure of the evaporation chamber of the IV-effect evaporation tank is controlled to be 0.18-0.22kg/cm2The pressure of the evaporation chamber of the V-effect evaporation tank is controlled to be 0.08-0.11kg/cm2。
Preferably, the temperature of the solution in the first-effect evaporation tank is controlled to be 126 ℃, the temperature of the solution in the second-effect evaporation tank is controlled to be 105 ℃, the temperature of the solution in the third-effect evaporation tank is controlled to be 83 ℃, the temperature of the solution in the fourth-effect evaporation tank is controlled to be 67 ℃, and the temperature of the solution in the V-effect evaporation tank is controlled to be 48 ℃.
When the mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate is the mother liquor produced by soda ash, the saturated saline water is adopted to absorb the cooled mixed gas of ammonia and carbon dioxide, and the saturated saline water is sent to the mode of preparing alkali to replace the step of preparing the ammonium bicarbonate by the cooled mixed gas of ammonia and carbon dioxide generated in the deamination process, and other conditions can be carried out by referring to the process for carrying out thermal recovery on the mother liquor obtained after the double decomposition production of sodium bicarbonate.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention sends the gas generated after deamination treatment into an ammonia absorption tower to generate carbon-containing ammonia water, then sends the carbon-containing ammonia water into a carbonization tower, and ensures that the carbon dioxide in the carbonization tower is excessive and can react with the ammonia water to generate ammonium bicarbonate by supplementing a proper amount of food-grade carbon dioxide in time and pressing carbon dioxide tail gas in the ammonia absorption tower into the carbonization tower, and further separates to obtain high-purity ammonium bicarbonate solid, and 1t of ammonium bicarbonate solid can be produced by additionally supplementing 150kg of carbon dioxide in the actual production.
2. The method adopts a five-effect vacuum evaporation process, optimizes the heating temperature, adopts cross-flow feeding evaporation, feeds deaminated mother liquor from an ammonia still into a second-effect evaporation tank without being sent to the first-effect or last-effect after coming out, controls the temperature to be 102-108 ℃, then sequentially discharges the deaminated mother liquor into a third-effect evaporation tank, a fourth-effect evaporation tank and a V-effect evaporation tank downstream, controls the temperatures of the third-effect evaporation tank, the fourth-effect evaporation tank and the V-effect evaporation tank to be 80-86 ℃, 64-70 ℃ and 45-50 ℃, respectively, sends secondary steam generated in an evaporation chamber of the V-effect evaporation tank to an atmospheric mixed condenser for condensation, does not pump off and discharges the deaminated mother liquor by a vacuum pump, and sends the mother liquor into the first-effect evaporation tank for evaporation and separates out sodium chloride crystals after the V-effect evaporation is finished. The five-effect cross-flow feeding can prevent secondary steam generated after high-temperature mother liquor after deamination firstly enters final effect from being incapable of being recycled, and can complete the whole multi-effect evaporation step only by one-time power transmission, thereby reducing power consumption, reducing equipment corrosion, reducing operation failure rate and prolonging production period.
3. By adopting the four-effect flash process, not only energy is saved, but also equipment scaling and blockage are reduced due to reduction of crystallization supersaturation, so that the production period is prolonged, and the purpose of not rinsing the tank in half a year can be achieved. In addition, the heat exchange process is optimized, the flash steam generated by the first effect flash tank, the second effect flash tank and the third effect flash tank respectively enters the heating chambers of the third effect flash tank, the fourth effect flash tank and the V effect salt evaporation tank for heat exchange, the heat utilization rate is further improved, and the heat exchanger is not easy to block.
4. The comprehensive recovery rate of the mother liquor is high and can reach more than 99.5 percent.
Detailed Description
The following examples are given to illustrate the present invention and it should be noted that the following examples are only for illustrative purposes and should not be construed as limiting the scope of the present invention, and that the modification and modification of the present invention by those of ordinary skill in the art are not essential to the present invention.
Example 1
Original mother liquor: mother liquor of double decomposition reaction for producing sodium bicarbonate, wherein Cl-Has a content of 167.5g/L, NH4 +Has a content of 62.96 g/L, HCO3 -The content of (b) is 35.86 g/L, and the raw mother liquor content is 119000 kg/h.
The process for recovering the product from the baking soda production mother liquor by the thermal method comprises the following steps:
pumping mother liquor into a primary condensate water heat exchanger of original mother liquor, heating the mother liquor to 38 ℃ by V-effect evaporation condensate water, then entering a secondary condensate water heat exchanger of the original mother liquor, heating the mother liquor to 58 ℃ by I-effect evaporation condensate water, then entering a tertiary condensate water heat exchanger of the original mother liquor, heating the mother liquor to 66 ℃, then entering an ammonia still, controlling the temperature of the lower part of the ammonia still to be 115 ℃, cooling mixed gas of ammonia and carbon dioxide generated in the ammonia removal process, then sending the cooled mixed gas into an ammonia absorption tower, and absorbing the ammonia and the carbon dioxide by water to generate carbon-containing ammonia water; feeding carbon-containing ammonia water into a carbonization tower, washing carbon dioxide tail gas which is not absorbed by water in an ammonia absorption tower, pressurizing by a compressor, feeding the carbon dioxide into the carbonization tower, supplementing 400kg/h of carbon dioxide into the carbonization tower, reacting excessive carbon dioxide with the carbon-containing ammonia water to generate ammonium bicarbonate crystals, decompressing and leading out reaction liquid from the carbonization tower, feeding the reaction liquid into a thickener for concentration, feeding bottom liquid of the thickener into a centrifuge for solid-liquid separation, and drying to obtain a food-grade ammonium bicarbonate product.
The method for recovering the deaminated mother liquor and obtaining ammonium chloride and sodium chloride comprises the following steps:
A. pumping the deaminated mother liquor into a second-effect evaporation tank by a pump for heating and evaporation, wherein the pressure of a heating chamber of the second-effect evaporation tank is 1.62kg/cm2Controlling the temperature of the solution at 105 ℃, discharging the mother liquor downstream into a III-effect evaporation tank for heating and evaporation after evaporation and concentration, and controlling the pressure of a heating chamber of the III-effect evaporation tank at 0.70 kg/cm2Controlling the temperature of the solution to be 83 ℃, discharging the mother solution into an IV-effect evaporation tank downstream for heating and evaporation after evaporation and concentration, wherein the pressure of a heating chamber of the IV-effect evaporation tank is 0.39kg/cm2Controlling the temperature of the solution at 67 ℃, discharging the mother liquor downstream into a V-effect evaporation tank for heating and evaporation after evaporation and concentration, wherein the pressure of a heating chamber of the V-effect evaporation tank is 0.19kg/cm2Controlling the temperature of the solution at 48 ℃, evaporating and concentrating, and passing the mother liquor and the precipitated crystals throughPumping into an I-effect evaporation tank for heating and evaporation, wherein the pressure of a heating chamber of the I-effect evaporation tank is 3.2kg/cm2Controlling the temperature of the solution at 126 ℃, carrying out evaporation concentration, discharging a large amount of salt crystals separated out from the I-effect evaporation tank, thickening the salt crystals by a salt thickener, then dewatering the salt crystals in a centrifugal machine, and drying sodium chloride obtained after centrifugal dewatering to obtain a product;
B. discharging the evaporation concentrated solution separated from sodium chloride crystals in the first-effect evaporation tank to a first-effect flash tank, discharging the mother solution into a second-effect flash tank downstream after flash concentration, discharging the mother solution into a third-effect flash tank downstream after flash concentration, discharging the mother solution and the crystals to a fourth-effect flash crystallizing tank after flash crystallization, discharging ammonium chloride crystals to an ammonium thickener after flash crystallization, dehydrating the bottom solution of the ammonium thickener through a centrifugal machine to obtain wet ammonium chloride, and drying the wet ammonium chloride to obtain a dry ammonium chloride product;
C. throwing the overflow liquid of the salt thickener and the liquid obtained after salt centrifugal machine into a liquid barrel after salt throwing, pumping the liquid into a V-effect evaporation tank by a pump, and participating in circulation again; the overflow liquid of the ammonium thickener and the liquid thrown by the ammonium centrifuge enter an ammonium thrown liquid barrel, and are sent into an IV-effect flash crystallization tank by a pump to participate in production circulation again;
wherein, the secondary steam of first effect flash tank of ammonium chloride flash process advances III effect evaporating pot heating chambers heat exchanges, and the secondary steam of II effect flash tank advances IV effect evaporating pot heating chambers heat exchanges, and III effect flash tank's secondary steam gets V effect evaporating pot heating chambers heat exchanges, and IV effect flash crystallizer's secondary steam gets into indirect condenser and uses the circulating water with its condensation.
The pressure from the boiler is 5kg/cm2The generated steam enters a heating chamber of an I-effect evaporation tank, secondary steam generated by an evaporation chamber of the I-effect evaporation tank is sent to a heating chamber of a II-effect evaporation tank to be used as a heat source for heating, secondary steam generated by an evaporation chamber of the II-effect evaporation tank is sent to a heating chamber of a III-effect evaporation tank to be used as a heat source for heating, secondary steam generated by an evaporation chamber of the III-effect evaporation tank is sent to a heating chamber of a IV-effect evaporation tank to be used as a heat source for heating, secondary steam generated by an evaporation chamber of the IV-effect evaporation tank is sent to a heating chamber of a V-effect evaporation tank to be used as a heat source for heating, secondary steam generated by an evaporation chamber of thePumping and emptying, and maintaining the vacuum degree at-0.092 MPa.
The condensed water in the heating chamber of the I-effect evaporation tank is discharged into the I-effect condensation bucket, the condensed water is pumped into the second-stage condensed water heat exchanger of the original mother liquid, after the mother liquid is heated, the condensed water is sent back to the boiler for recycling, the condensed water in the heating chamber of the II-effect evaporation tank is discharged into the II-effect condensation bucket, then the condensed water in the heating chamber of the III-effect evaporation tank is discharged into the III-effect condensation bucket and the condensed water after the II-effect flash, the condensed water in the heating chamber of the IV-effect evaporation tank is discharged into the IV-effect condensation bucket and the condensed water after the III-effect flash, the condensed water in the heating chamber of the V-effect evaporation tank is discharged into the V-effect condensation bucket and the condensed water after the IV-effect flash, the condensed water is pumped into the first-stage condensed.
Wherein, the ammonia still is indirect steam heating formula sieve tray tower, and the ammonia absorption tower is circulative cooling bubble cap tower, and the carbonators is the sieve tray tower of taking the cooling zone, and I ~ V imitates the evaporating pot and is the external heating formula forced circulation axial feeding evaporating pot, and I imitates the evaporating pot and has the clamp cover that possesses the clear liquid separation function, and I ~ III imitates the flash tank and is forced circulation axial feeding flash tank, and IV imitates the flash crystallizer and be forced circulation axial feeding flash crystallizer, and IV imitates the flash crystallizer and have the clamp cover that possesses the clear liquid separation function.
The total steam consumption is 16600kg/h (not counting the energy consumption of ammonia distillation), the ammonium chloride is recovered by 19400kg/h, and the sodium chloride is recovered by 12890 kg/h. The steam consumption of the ammonia still is 19500kg/h, and 5920 kg/h of recovered ammonium bicarbonate.
Example 2
Original mother liquor: mother liquor of soda production, in which Cl is contained-The content of (B) is 161.5g/L, NH4 +Has a content of 63.7g/L, HCO3 -With CO3 2-The content of (b) was 67.5g/L, and the amount of the raw mother liquor was 119000 kg/h.
The difference compared to example 1 is that first: the raw mother liquor used in example 1 is the mother liquor after the production of sodium bicarbonate by metathesis reaction (i.e., the mother liquor for the production of sodium bicarbonate), while the raw mother liquor in this example is the mother liquor for the filtration of heavy alkali (i.e., the mother liquor for the production of sodium carbonate), which contains ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate, but the contents of the two solutions are different; secondly, in this embodiment, the tail gas from the ammonia still is cooled and then absorbed by saturated brine, and the brine is returned to the alkali making system, but the process of absorbing ammonia and carbon dioxide in the tail gas by using water and producing ammonium bicarbonate by carbonization in embodiment 1 is not used, and other steps, process parameters and other conditions are consistent with embodiment 1. Absorbing the cooled mixed gas of ammonia and carbon dioxide by using saturated brine, and sending the saturated brine to prepare alkali.
The total steam consumption is 169900 kg/h (not counting the ammonia distillation energy consumption), ammonium chloride 18950kg/h is recovered, and sodium chloride 9110 kg/h is recovered.
Claims (9)
1. The process for recovering the product from the mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate by a thermal method is characterized by comprising the following steps: the method comprises the steps of recovering gas generated after the deamination of the mother liquor and recovering the deaminated mother liquor to obtain ammonium chloride and sodium chloride;
the method for recovering the gas generated after the deamination of the mother liquor comprises the following steps: mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate and sodium bicarbonate is pumped into a primary condensate water heat exchanger of the original mother liquor by a No. 1 pump, and the mother liquor is heated to 35-40 ℃ by V-effect evaporation condensate water; then the mother liquor enters a secondary condensate water heat exchanger of the original mother liquor, and the mother liquor is heated to 55-60 ℃ by I-effect evaporation condensate water; then enters a third-stage heat exchanger of the original mother liquor, the mother liquor is heated to 65-70 ℃ and then enters an ammonia still, the temperature of the lower part of the ammonia still is controlled to be 105-120 ℃, and the ammonium bicarbonate is prepared by using the cooled mixed gas of ammonia and carbon dioxide generated in the deamination process, which comprises the following specific steps: sending the mixed gas of ammonia and carbon dioxide into an ammonia absorption tower, and absorbing the ammonia gas and the carbon dioxide by water to generate carbon-containing ammonia water; feeding carbon-containing ammonia water into a carbonization tower, washing carbon dioxide tail gas which is not absorbed by water in an ammonia absorption tower, pressurizing by a compressor, feeding into the carbonization tower, supplementing food-grade carbon dioxide which accounts for 15-20% of the total amount of the required carbon dioxide into the carbonization tower in time to enable the carbon dioxide to be excessive, reacting with the carbon-containing ammonia water in the carbonization tower to generate ammonium bicarbonate crystals, decompressing and leading out reaction liquid from the carbonization tower, feeding into a thickener for concentration, feeding bottom liquid of the thickener into a centrifugal machine for solid-liquid separation, and drying to obtain a food-grade ammonium bicarbonate product,
the method for recovering the deaminated mother liquor and obtaining ammonium chloride and sodium chloride comprises the following steps:
A. conveying the deaminated mother liquor from an ammonia still to a II-effect evaporation tank through a No. 2 pump for heating and evaporation, wherein the temperature of the solution is controlled to be 102-108 ℃; after evaporation and concentration, mother liquor is discharged into a III-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 80-86 ℃; after evaporation and concentration, mother liquor is discharged into an IV-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 64-70 ℃; after evaporation and concentration, mother liquor is discharged into a V-effect evaporation tank downstream to be heated and evaporated, and the temperature of the solution is controlled to be 45-50 ℃; after evaporation and concentration, the mother solution and the precipitated crystals are sent into an I-effect evaporation tank through a No. 3 pump for heating and evaporation, and the temperature of the solution is controlled to be 120-129 ℃; after evaporation concentration, washing sodium chloride crystals separated out from the I-effect evaporation tank, discharging, thickening by a salt thickener, then dewatering in a centrifuge, and drying sodium chloride obtained after centrifugal dewatering to obtain a product;
B. discharging the evaporation concentrated solution of sodium chloride crystals separated from the first-effect evaporation tank to the first-effect flash tank; after flash evaporation and concentration, mother liquor is discharged into a second-effect flash tank; after flash evaporation and concentration, mother liquor is discharged into a III-effect flash tank in a downstream manner; after flash crystallization, discharging the mother liquor and the crystals to an IV-effect flash crystallization tank; after flash crystallization, conveying ammonium chloride crystals to an ammonium thickener by using a No. 4 pump, dehydrating the base solution of the ammonium thickener by using a centrifugal machine to obtain wet ammonium chloride, and drying the wet ammonium chloride to obtain a dry ammonium chloride product;
C. throwing the overflow liquid of the salt thickener and the liquid obtained after salt centrifugal machine into a liquid barrel after salt throwing, and sending the liquid into a V-effect evaporation tank by a No. 5 pump to participate in circulation again; the overflow liquid of the ammonium thickener and the liquid thrown by the ammonium centrifuge enter an ammonium thrown liquid barrel, and are sent into an IV-effect flash crystallization tank by a No. 6 pump to participate in production circulation again;
secondary steam of the first-effect flash tank enters a heating chamber of a third-effect evaporation tank for heat exchange in the ammonium chloride flash process, secondary steam of the second-effect flash tank enters a heating chamber of a fourth-effect evaporation tank for heat exchange, secondary steam of the third-effect flash tank enters a heating chamber of a fourth-effect evaporation tank for heat exchange, and secondary steam of the fourth-effect flash crystallization tank enters an indirect condenser for condensing with circulating water;
raw steam from a boiler is sent into a heating chamber of an I-effect evaporation tank, secondary steam generated by the evaporation chamber of the I-effect evaporation tank is sent into the heating chamber of a II-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the II-effect evaporation tank is sent into a heating chamber of a III-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the III-effect evaporation tank is sent into a heating chamber of a IV-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the IV-effect evaporation tank is sent into a heating chamber of a V-effect evaporation tank to be used as a heat source for heating mother liquor, secondary steam generated by the evaporation chamber of the;
the condensed water in the heating chamber of the I-effect evaporation tank is discharged into an I-effect condensation bucket, the condensed water is pumped into a second-stage condensed water heat exchanger of the original mother liquor, after the mother liquor is heated, the condensed water is sent back to the boiler for recycling, the condensed water in the heating chamber of the II-effect evaporation tank is discharged into an II-effect condensation bucket, then the condensed water in the heating chamber of the III-effect evaporation tank is discharged into the III-effect condensation bucket and the condensed water after the II-effect flash, the condensed water in the heating chamber of the IV-effect evaporation tank is discharged into an IV-effect condensation bucket and the condensed water after the III-effect flash, the condensed water in the heating chamber of the V-effect evaporation tank is discharged into the V-effect condensation bucket and the condensed water after the IV-effect flash are discharged into the first-stage condensed water heat exchanger of the original mother liquor.
2. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the ammonia still is an indirect steam heating type sieve plate tower.
3. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the ammonia absorption tower is a circulating cooling bubble cap tower.
4. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the carbonization tower is a sieve plate tower with a cooling section.
5. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the I-V effect evaporation tanks are externally heated forced circulation axial feeding evaporation tanks, and each I effect evaporation tank is provided with a jacket with a clear liquid separation function.
6. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the I-III effect flash tanks are all forced circulation axial feeding flash tanks, the IV effect flash crystallization tank is a forced circulation axial feeding flash crystallization tank, and the IV effect flash crystallization tank is provided with a jacket with a clear liquid separation function.
7. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the pressure of the evaporation chamber of the I-effect evaporation tank is controlled to be 1.65-1.7kg/cm2The pressure of the evaporation chamber of the II-effect evaporation tank is controlled to be 0.69-0.75kg/cm2The pressure of the evaporation chamber of the III-effect evaporation tank is controlled to be 0.38-0.44kg/cm2The pressure of the evaporation chamber of the IV-effect evaporation tank is controlled to be 0.18-0.22kg/cm2The pressure of the evaporation chamber of the V-effect evaporation tank is controlled to be 0.08-0.11kg/cm2。
8. The process according to claim 1 for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate, characterized in that: the temperature of the solution in the first-effect evaporation tank is controlled to be 126 ℃, the temperature of the solution in the second-effect evaporation tank is controlled to be 105 ℃, the temperature of the solution in the third-effect evaporation tank is controlled to be 83 ℃, the temperature of the solution in the fourth-effect evaporation tank is controlled to be 67 ℃, and the temperature of the solution in the V-effect evaporation tank is controlled to be 48 ℃.
9. Process for the thermal recovery of products from a mother liquor containing ammonium chloride, sodium chloride, ammonium bicarbonate, sodium bicarbonate according to any one of claims 1 to 8, characterized in that: and adopting a saturated saline water mode to absorb the cooled mixed gas of ammonia and carbon dioxide and sending the saturated saline water to prepare alkali to replace the step of preparing ammonium bicarbonate by using the cooled mixed gas of ammonia and carbon dioxide generated in the deamination process.
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| CN110980765A (en) * | 2019-12-24 | 2020-04-10 | 武汉德泽环保科技有限公司 | Process for preparing ammonium chloride |
| CN111802621A (en) * | 2020-07-10 | 2020-10-23 | 益盐堂（应城）健康盐制盐有限公司 | Selenium-rich edible salt and preparation method thereof |
| CN112093812A (en) * | 2020-10-05 | 2020-12-18 | 湖南海联三一小苏打有限公司 | Cyclic manufacturing method for co-production of sodium bicarbonate and ammonium chloride |
| CN114605012B (en) * | 2022-03-30 | 2023-05-02 | 光大环境科技（中国）有限公司 | Forward osmosis zero-emission system taking ammonium bicarbonate as drawing liquid and operation process thereof |
| CN115159573B (en) * | 2022-07-26 | 2023-03-24 | 敦煌寰泰绿钒科技有限公司 | Method for purifying ammonium metavanadate and method for preparing vanadium pentoxide |
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| CN101544437B (en) * | 2009-04-30 | 2011-04-27 | 河北工业大学 | Process method for recovering ammonium chloride and sodium chloride from waste water containing ammonium chloride and sodium chloride |
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