Method for treating free ammonia during sodium bicarbonate production and application

Abstract

The invention discloses a method for treating ammonium chloride in sodium bicarbonate mother solution at normal temperature and application. The method comprises the following steps of: adding saturated brine into a double decomposition reaction kettle, adding ammonium hydrogen carbonate to perform double decomposition reaction to generate sodium bicarbonate, and then filtering, dehydrating and drying the sodium bicarbonate to obtain sodium bicarbonate; and adding free ammonia (NH3) gas generated in the double decomposition reaction process and the drying process into concentrated sulfuric acid, absorbing the free ammonia by using sulfate radical negative ions (SO4<->), generating ammonium sulfate [(NH4)2SO4] crystal and separating out the crystal. When the sodium bicarbonate is generated by the double decomposition reaction, the temperature is controlled to be between 40 and 47 DEG C, so that escape and sublimation of the free ammonia are promoted; and the free ammonia generated in the double decomposition reaction process and the drying process are absorbed by using sulfate radicals (SO4<->) or nitrate radicals (NO3<->), and the generated ammonium sulfate is returned and used as a negative ion promoting agent added into the sodium bicarbonate mother solution, so the loss of ammonia is low, the utilization rate of the ammonia is high, and the method has remarkable energy-saving and environmentally-friendly benefits.

Description

technical field [0001] The invention relates to a method for producing baking soda by metathesis, in particular to a method for treating free ammonia in the production process of baking soda and its application. Background technique [0002] Existing production of baking soda (NaHCO 3 ) process such as figure 1 As shown, add the purified saturated brine (NaCl) into the metathesis kettle, raise the temperature to 33-38°C, and then add ammonium bicarbonate (NH 4 HCO 3 ) for metathesis reaction to generate baking soda, then filter the baking soda, and use saturated soda water (Na 2 CO 3 ) to remove chloride ions (Cl - ), dehydrated and dried by a centrifuge to obtain baking soda; the free ammonia generated during the metathesis reaction and the drying process is emptied; the filtered and dehydrated baking soda mother liquor contains ammonium chloride, free ammonia (NH 3 ), dissolved ammonium bicarbonate and sodium bicarbonate, mainly ammonium chloride aqueous solution, an...

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Problems solved by technology

[0003] 1. After concentrating and recovering ammonium chloride and sodium chloride, the mother liquor still needs to be discharged, which cannot fundamentally solve the problem of environmental pollution caused by waste water discharge;

[0004] 2. Despite the adoption of energy-saving multi-effect evaporation, 0.3-0.5 tons of standard coal is still needed to produce one ton of ammonium chloride, and the cost of each ton of product is increased by 200 to 300 yuan, which increases the cost of the enterprise, the efficiency of the enterprise is low, and the saturated brine must be processed first. After purification, the metathesis reaction with ammonium bicarbonate can be carried out, which increases the production cost;

[0005] 3. Since the content of ammonium chloride in the solution is only 12% to 18%, the evaporative cooling time is long, usually 6-8 hours, and 8-10 firemen and evaporative cooling workers must be added, which is time-consuming and labor-intensive. High labor cost and low production efficiency

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