1.1 Production Method
The production method of soda ash adopts the traditional intermittent method of pot cooking 30-50% liquid caustic soda through intermittent causticizing in large pots. The caustic soda is boiled at high temperatures for dehydration and concentration into a molten state, with NaOH content in the molten alkali exceeding 99%. Subsequently, the molten alkali is cooled into flakes through a flaking machine.
1.2 Process Flow Description
⑴ Intermittent Pot Cooking
30-50% liquid caustic soda purchased externally is pumped into raw material storage tanks through unloading devices, and the alkali from the raw material tanks is pumped into causticizing pots using alkali pumps. The caustic soda is pumped until the pot is filled to the required level. Once all the pots behind the triple pot are filled with alkali, the raw material alkali is pumped into the alkali blending tank for later use. After the alkali level in the pots meets the liquid level requirements, the causticizing stove is ignited. Heat generated by coal combustion heats the caustic soda in the causticizing pot gradually until it reaches the boiling point. Water in the caustic soda evaporates continuously as steam through the exhaust chimney, maintaining the boiling temperature. As the evaporation progresses, the liquid level in the pots decreases, and alkali liquid from the high-level alkali blending tank is continuously added to maintain the liquid level. This process continues until the temperature of the caustic soda in the pot reaches about 420°C, at which point alkali blending stops. When the temperature of the caustic soda in the pot reaches 460°C, coal addition to the stove is stopped, and the fire is extinguished for insulation. As the temperature of the caustic soda gradually drops to about 400-410°C, sulfur is added to the pot for coloring. After coloring, the caustic soda settles for about 5-6 hours, and then it is pumped into the flaking machine. The alkali from the high-level tank flows into the arc-shaped pot of the flaking machine under flow control. The alkali in the arc-shaped pot is cooled into flakes by the flaking machine and then sent to a cooling drum for secondary cooling, reducing its temperature to ≤100°C. The resulting soda ash flakes are manually weighed, packaged, and sealed as the final product.
While the causticizing pot is heated directly with coal, the resulting high-temperature flue gas sequentially enters the subsequent preheating pots II and III for preheating, evaporating water in the caustic soda. To ensure the liquid level in the pots, raw material alkali is intermittently added to the pot. After the molten caustic soda is discharged from the causticizing pot, the alkali in the preheating pots is gradually transferred. Once the III-level preheating pot is emptied, raw material alkali is pumped into it to the required level. If all facilities are in order, the causticizing pot is reignited for the next production cycle.
⑵ Soda Ash Flaking
The molten soda ash from the causticizing pot flows into the arc-shaped alkali tank at the bottom of the flaking machine through a finished product separation tank. The surface of the cooling drum of the flaking machine has grooves, with the lower part of the drum immersed in molten alkali in the arc-shaped tank. Cooling water is introduced into the bearing center and sprayed onto the inner surface of the cooling drum, which rotates slowly at a speed of 1.53r/min. A solid soda ash layer with a thickness of 0.81.5mm continuously condenses on the outer surface of the drum, which is scraped off by scrapers to form soda ash flakes that fall into the finished product hopper.
⑶ Cooling and Packaging
Hot soda ash flows naturally from a high position into the drum cooling machine, where it is cooled by spraying water on the external surface of the drum. After cooling to 85-120°C, the soda ash is directly packaged and sealed manually by weight.