How to produce sodium bicarbonate?
How to produce sodium bicarbonate?
At present, the method in the industry to produce heavy soda using light soda as raw materials includes solid phase hydration method, liquid hydration method and extrusion method; method using natural soda as rat material including evaporation and carbonation method with the latter two methods have been described in the section of industry sodium carbonate; thus here we only describe the three ways using soda ash as raw material. 
Solid-phase method: put the high-temperature light soda and hot water of 50~70 ℃ for hydration reaction at 90~97 ℃ conditions for generating into sodium carbonate monohydrate, which was further calcined at 130~150 ℃, and further went through sieve to obtain heavy soda products. Its reaction equation is: Na2CO3 + H2O → Na2CO3 ? H2O 
Na2CO3 ? H2O [△] → Na2CO3 + H2O
Liquid-phase Hydration method: at about 100 °C, the high temperature light soda is dissolved using water and recycling mother liquor was dissolved to prepare a saturated solution and have hydration reaction; the reation mixture was further pumped to the crystallizer and cool to 80~90 ℃ to generate the suspension of sodium carbonate monohydrate, which further underwent thickening, separation to generate the heavy soda products. The reaction formula is similar to the solid phase hydration method.
Extrusion method: extrude the high-temperature (150~160 ℃) soda from a base compartment in a pressure of 5000~7000 kg/cm2 to rigid sheet with a thickness of 2 mm, and then crushed and sieved to get the heavy soda product with suitable particle size. The big particles were sent back to be broken while the small particle was subject to extrusion again and cyclically used separately.
There are mainly three ways including ammonia soda method, Union soda method and natural soda processing method.
The main reaction of Solvay method is as follows: NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl 2NaHCO3 → Na2CO3 + CO2 + H2O
The process is briefly summarized as follows: the original salt was dissolved in water and made into refined salt water (or secondary salt water; it is the same below) after the removal of calcium and magnesium salt. The secondary salt water further underwent absorption of ammonia to make ammonia salt water with NaCl concentration of more than 89 titers, the ratio of FNH3 and Na + concentration ratio being within the range of 1.13~1.18. The ammonia salt was cooled to 35~38 ℃ and further sent to carbonization section to have reaction with the pre-compressed carbon dioxide coming from lime kiln and calciner to generate the sodium bicarbonate suspension and flow to filtration section in which the sodium carbonate (bicarbonate) crystal was separated from the suspension and sent to the upper section of calcination for calcination and decomposition at 160 ℃to obtain soda products. The filtered mother liquor is mixed with the lime milk from lime section to get blend; at the same time, use the steam heating to distill out the ammonia in the distillation column for ammonia absorption by salt water for cycle utilization.
The production process of the Union soda method is divided into soda process (also known as I process) and manufacturing ammonium process (process known as II) for union production of soda and ammonium chloride while the mother liquor constitutes a closed loop in the two processes.
The main reaction is the same as ammonia soda method The process is briefly summarized as follows: the original salt (sodium chloride) was washed with saturated brine to remove calcium and magnesium impurities, and then crushed, washed, thick, separated to obtain the washed salt with qualified purity (NaCl content ≥98%), particle size (10 to 20 mesh) and further sent to the salting crystallizer. The overflowed mother liquor II from the salting crystallizer absorbed the ammonia in the ammonia absorber to generate ammonia mother liquor II, which after clarification, was sent to the carbonation tower for absorption of carbon dioxide (carbonation) to get the suspension of sodium bicarbonate; the sodium bicarbonate suspension was filtered to obtain solid sodium bicarbonate which was further calcined to obtain the soda product. 
The mother liquor (liquor I) with heavy soda filtered generated ammonia mother liquor I after absorbing ammonia; the ammonia mother liquor I was further subject to heat exchange with the mother liquor II through the heat exchanger and sent into cold separation crystallization machine after cooling and further had heat exchange with cold carrier body (brine) or refrigerant (liquid ammonia) through external cooling device; at 5~10 °C, part of the ammonium chloride is cooled and precipitated out. The overflow liquid (half liquor II) of the cold separation crystallization device flowed back into the salting crystallizer; add washed salt to precipitate some more ammonia chloride. 
The ammonia chloride suspension originated from the cold precipitation and salting crystallization device was subject to thickening, separation to obtain a wet ammonium chloride which was further sent to ammonium dry oven to get the dried ammonia chloride product. The overflow liquid (mother liquor II) of the salting crystallizer was subject to heat exchange with ammonia liquor l to generate ammonia mother liquor II after absorption of ammonia and then sent to the carbonation tower for making soda. With such kind of continuous cycle, we can constantly produce soda and ammonium chloride.
Natural soda processing method
Sesquisoda method: this method is based using sesquisoda as raw materials for production of soda. Some US natural soda processing plants apply this method.
Ore was crushed to around 20 mesh (O.8mm) and sent into the dissolving tank; using circulating mother liquor to dissolve it into a saturated solution and send into the clarifier to clarify it with underflow into thickener; add water to rinse the soda component in the with recycling mud. The clarifier overflow liquid was filtered and sent to three-effect evaporator for evaporation; the crystal slurry taken from the third-effect evaporator was pumped into the thickener and then subject to centrifuge for dewatering to obtain the filtered pellet of Sesquisoda, which generates soda through calcination soda.
Carbon monohydrate method: this method was also based on using sesquisoda as the raw material for the production of soda; its product quality is superior to the sesquisoda process and it is adopted by the majority of the US natural soda processing plants.
The ore was crushed to about 6 mm and sent the calciner for calcination at about 150 ℃; the most fraction of the ore is crude soda; it further entered into the dissolving tank and was dissolved at temperature slightly below 100 ℃ and sent to the three-effect evaporator after the clarification with the concentrated soda suspension being isolated to obtain the sodium carbonate monohydrate and sent to drier for drying to obtain heavy soda.
Carbonation method: this method is based on using natural alkali halide as raw material, and was adopted at Dabusu area for natural soda processing.
The natural alkali of solution mining or water dissolved alkali halide was subject to clarification, preheating and subject to carbonation with carbon dioxide; further went through filtration and calcination to obtain soda. During the mid-1980s, the ammoniated carbonization method was successfully developed; namely, the refined alkali halide first absorbs nitrogen and then carbonation with the following steps the same as before. Compared to the direct carbonization, ammoniated carbonation method increase the sodium utilization by 25% to 65% to 70%.
Natural soda halide evaporation method: use natural soda ore of solution mining or natural soda originated from the alkali lake to obtain alkali halide which further undergone refining, separation, preheating, evaporation, separation, calcination to obtain Orioles soda.
Sodium carbonate synthesis method: the crude sodium carbonate and sodium bicarbonate was dissolved by steam and clarifying the supernatant after settling impurity; after sending carbon dioxide for reaction to certain concentration, further go through distillation, cooling and crystallization to obtain sesquisoda, the reaction equation is as below:
Na2CO3 + NaHCO3 + 2H2O → Na2CO3 ? NaHCO3 ? 2H2O
Natural soda method: take natural soda as raw material; it is subject to steam dissolving and clarification, impurity removal with the supernatant containing sodium carbonate, sodium bicarbonate and sodium sulfate, etc., carry out kiln gas carbonation to make some part of Na2CO3 to be re-carbonized into NaHCO3, which was evaporated at 60 ℃ for precipitating out of the corresponding complex with separation generating sesquisoda finished product. The mother liquor was evaporated again to precipitate Glauber base. The reaction equation is as below:
3Na2CO3 + 5H2O + CO2 → 2 (Na2CO3 ? NaHC03 ? 2H2O)
At present, China always adopts ammonia soda or union soda method for direct production of edible Soda. During the process of making light soda, we need to increase the refining process such as removal of arsenic and heavy metal impurities. See other industrial processes in the part of industrial sodium carbonate.

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