Potassium hydroxide is prepared by chemical process. At present, most manufacturers adopt ion-exchange membrane method. The core process of the process flow is primary refining of brine, and the key equipment is electrolytic cell and ion-exchange membrane. The main processes are as follows:

1、鹽水一次精制

1. Primary refining of brine

一次鹽水工序的任務是將氯化鉀、回收鹽水、離子膜電槽經過脫氯處理的淡鹽水，進行處理成符合要求的過濾鹽水。由于這些鹽水中含有隔膜所不能允許的雜質（有機物、菌藻類、SO42-、Ca2+、Mg2+、NH3、重金屬、SS等），特別是SO42-、Ca2+、Mg2+在電解槽里會阻塞隔膜或離子膜，導致電解槽鹽水液面上升，使電流效率下降、槽電壓升高、電解槽壽命縮短，甚會造成停車。在鹽水中分別加入精制劑氯化鋇（或采用膜過濾，但許多中小型裝置還是采用鋇法）、氫氧化鉀、次氯酸鉀、碳酸鉀、絮凝劑、亞硫酸鉀等，以分別除去鹽水中的SO42-、Mg2+雜質后，再經過濾器除去SS、CaCO3等雜質以達到工藝要求。

The task of primary brine process is to treat potassium chloride, recovered brine and light brine dechlorinated by ion-exchange membrane electrolyzer into qualified filtered brine. Because these brine contains impurities (organic matter, bacteria and algae, SO42 -, Ca2 +, Mg2 +, NH3, heavy metals, SS, etc.) that cannot be allowed by the diaphragm, especially SO42 -, Ca2 +, Mg2 + will block the diaphragm or ion membrane in the electrolytic cell, resulting in the rise of brine level in the electrolytic cell, the decrease of current efficiency, the increase of cell voltage, the shortening of cell life, and even shutdown. Add refining agent barium chloride (or membrane filtration, but many small and medium-sized devices still use barium method), potassium hydroxide, potassium hypochlorite, potassium carbonate, flocculant and potassium sulfite to remove SO42 - and Mg2 + impurities in the brine respectively, and then remove SS, CaCO3 and other impurities through the filter to meet the process requirements.

2、鹽水二次精制

2. Secondary refining of brine

離子膜電解對鹽水的質量要求高，從一次鹽水工序來的過濾精鹽水還需經過離子交換，進一步降低Ca、Mg離子。離子交換樹脂塔有兩塔流程和三塔流程之分。采用三塔流程，正常情況下兩塔串聯運行，一塔再生。

Ion membrane electrolysis has high requirements for the quality of brine. The filtered refined brine from the primary brine process needs to undergo ion exchange to further reduce Ca and Mg ions. Ion exchange resin tower can be divided into two tower processes and three tower processes. Three tower process is adopted. Under normal conditions, two towers operate in series and one tower regenerates.

3、電解

3. Electrolysis

經過二次精制，即鹽水進入螯合樹脂塔除去其中的鈣、鎂，泵入高位槽后流入離子膜電解槽的陽極室。通入直流電后，在陽極室產生氯氣和流出淡鹽水經分離器分離，氯氣輸送到氯氣總管，淡鹽水一般含氯化鉀200-220g/l，經脫氯氣去飽和槽。在電解槽的陰極室產生氫氣和30-32%液堿同樣也經過分離器，氫氣輸送到氫氣總管。30-32%的液堿可以作為商品出售，也可以送到蒸發裝置蒸濃到48%的液堿。

After secondary refining, that is, the brine enters the chelating resin tower to remove calcium and magnesium, which is pumped into the high-level tank and then flows into the anode chamber of the ion-exchange membrane electrolyzer. After DC power is applied, chlorine gas and outgoing light brine are generated in the anode chamber and separated by the separator. The chlorine gas is transmitted to the chlorine main pipe. The light brine generally contains 200-220g / L potassium chloride and passes through the dechlorination gas desaturation tank. Hydrogen and 30-32% liquid alkali generated in the cathode chamber of the electrolytic cell also pass through the separator, and the hydrogen is transmitted to the hydrogen main pipe. 30-32% of liquid alkali can be sold as a commodity, or it can be sent to the evaporation unit to evaporate to 48% of liquid alkali.

4、蒸濃與氯氣、氫氣、廢氣處理

4. Steam concentration and treatment of chlorine, hydrogen and waste gas