At present, the methods of potassium hydroxide still used mainly include diaphragm method, mercury electrolysis method and ion-exchange membrane electrolysis method. There are many methods. Generally, the advantages and disadvantages of a process need to be comprehensively considered from the aspects of finished product quality, cost and equipment cost. Today, we will talk about the process of silver electrolysis method.
The electrolyte preparation of mercury electrolysis method is the same as that of diaphragm electrolysis method. In the electrolytic chamber, graphite (or metal) is used as the positive and mercury as the negative. The chlorine generated by electrolysis is sent to the chlorine drying process, and the generated potassium amalgam flows into the mercury dissolving chamber. Most of the potassium chloride did not react, and then returned to the raw material dissolution process after being treated in the state of light brine. Potassium amalgam reacts with clean water to produce potassium hydroxide and hydrogen. Because the concentration generated from the mercury dissolving chamber is 45% ~ 50%, it can be used as liquid products, and can also be evaporated into solid alkali or made into flake products through alkali boiling pot.
(1) Refining of potassium chloride solution: the raw material potassium chloride is dissolved in the salt tank, and potassium carbide is added. Barium chloride removes impurities such as calcium, magnesium and sulfate, and then enters the clarification tank. The clear liquid overflows. A slight suspension is filtered by a sand filter and sent to the neutralization tank, acidified with hydrochloric acid and flows into the refined brine storage tank, After passing through the brine preheater, pump the refined brine to the brine high-level tank, and then flow into the mercury electrolytic tank. Clarify the salt mud at the bottom of the tank, then filter and recover the brine, and then discharge the mud.
(2) Electrolysis: Mercury electrolytic cell is divided into electrolysis chamber and pump chamber. In the electrolysis chamber, graphite or metal is used as the positive * and mercury as the negative *. The chlorine generated after power on is sent to the chlorine drying process, and the electrolyzed potassium is pumped into the de pumping chamber. Most unreacted potassium chloride is treated in light brine and then returned to brine process. In the DEPUMPING chamber, the potassium pump reacts with the clean water at the end to generate potassium hydroxide solution, which flows into the electrolyte storage tank. The hydrogen generated in the de pumping room is sent to the hydrogen transmission station.
(3) Solid alkali: alkali liquor containing koh45-50% from the pump chamber of mercury electrolytic cell is made into solid alkali by boiling alkali or into products by making machine-made tablets.
The above is the process of potassium hydroxide by mercury electrolysis, which can generally be used to make liquid alkali and solid alkali, both of which can be used.