Sodium hydroxide (NaOH) produced by ion-exchange membrane is an indispensable basic chemical raw material in industrial production, widely used in chemical synthesis, textile printing and dyeing, papermaking, electroplating, water treatment, pharmaceuticals, and many other fields. The advancement and stability of production equipment directly determine product quality, production efficiency, and environmental protection standards. Tianli has deep expertise in ion-exchange membrane method for the production of sodium hydroxide, providing complete set of equipment for standardized ion-exchange membrane method. Utilizing mature and advanced ion-exchange membrane electrolysis technology, Tianli covers the entire process including raw material pretreatment, electrolysis reaction, rectification and power supply, and product refining. Leveraging comprehensive technological advantages, we provide customers with efficient, low-consumption, environmentally friendly, and intelligent production solutions, helping them to achieve large-scale, green, and refined production.
I. Properties of Core Materials
The caustic soda produced by ion-exchange membrane method is colorless and transparent liquid (or flaky solid) with the molecular formula NaOH, relative molecular mass of 40.00, density of 1.328 g/cm³, and melting point of 318.4℃. It is highly corrosive, highly alkaline, and hygroscopic. It is mainly available in 32% and 48% liquid caustic soda and 96% and 99% flake caustic soda to meet the needs of different industries. The production process requires strict control of electrolysis parameters to prevent leakage and corrosion.
II. Core Process Flow Introduction
The production of caustic soda using ion-exchange membrane method adopts sodium chloride and pure water as raw materials. It follows a closed-loop process: raw material pretreatment → brine purification → electrolysis reaction → dechlorination of dilute brine → caustic soda purification → finished product storage. This process relies on advanced ion-exchange membrane electrolysis equipment to achieve precise linkage and full controllability across all stages, as detailed below:
1. Raw material pretreatment: the raw salt is crushed and dissolved to make saturated brine. Suspended impurities and silt are removed by sedimentation and filtration. Impurity removal reagent is added to remove impurity ions such as calcium, magnesium, and sulfate from the brine (impurity removal rate ≥99.9%) to avoid clogging of the ion exchange membrane and affecting electrolysis efficiency.
2. Brine purification: the pretreated brine is subjected to precision filtration and deep purification with chelating resin to obtain pure refined brine (impurity content ≤0.1mg/L), which is then sent to a brine storage tank. After being preheated to 80-90℃, it is transported to ion-exchange membrane electrolyzer to ensure stable electrolysis reaction.
3. Electrolysis reaction: refined brine enters the ion exchange membrane electrolytic cell and undergoes electrolysis reaction under the action of direct current. Chlorine gas (Cl₂) is produced at the anode, and hydrogen gas (H₂) and sodium hydroxide (NaOH) are produced at the cathode. The reaction equation is 2NaCl + 2H₂O → 2NaOH + Cl₂↑ + H₂↑. The electrolysis efficiency is ≥98%. The ion exchange membrane can accurately separate ions, ensuring the purity of caustic soda.
4. Dechlorination of brine: the dechlorinated brine (with reduced NaCl concentration) after electrolysis is treated by dechlorination tower to remove residual chlorine. The dechlorinated brine is then returned to the raw material dissolution process for recycling. The recovered chlorine can be recycled after drying and compression, thus achieving resource recycling.
5. Caustic soda refining and exhaust gas treatment: the dilute caustic soda solution (concentration of approximately 30%) generated by electrolysis is first concentrated by an evaporation system to remove excess water, increasing its concentration to 48% for liquid caustic soda. If caustic soda flakes are to be prepared, the 48% liquid caustic soda is further fed into a triple-effect evaporator for further concentration to over 96%, and then fed into a caustic soda flake forming machine. After high-temperature melting (temperature controlled at 320-350℃), film cooling, and slicing, 96% and 99% grade caustic soda flakes are produced. The hydrogen generated by electrolysis is purified, pressurized, and then recovered for reuse; chlorine is treated to meet emission standards; production wastewater is treated and recycled; and the waste heat recovered during evaporation is used for caustic soda preheating, achieving clean production and energy recycling.
III. Core Technical Advantages
1. Technological advantages: it adopts mature ion exchange membrane electrolysis technology, combined with high-efficiency ion membranes and electrolyzers, with electrolysis efficiency of ≥98% and high raw material utilization. The equipment is made of corrosion-resistant and high-temperature-resistant materials to resist corrosion from caustic soda and chlorine gas for long service life. The modular design makes operation and maintenance convenient, enabling continuous and large-scale production and adapting to different output and product specification requirements.
2. Energy consumption advantages: equipped with a high-efficiency rectifier power supply system to reduce electrolysis energy consumption; optimized brine preheating and waste heat recovery process to recover waste heat from electrolysis reaction for brine preheating, resulting in overall energy consumption reduction of more than 15% compared to traditional caustic soda plants, significantly reducing enterprise production costs.
3. Environmental advantages: the entire production process is carried out in a closed system. Chlorine and hydrogen are recycled or purified before being discharged, and there is no leakage of harmful gases. Salt water and production wastewater are recycled to achieve zero wastewater discharge. The waste residue can be recycled for use in the building materials industry, which is in line with the concept of green and low-carbon development and meets environmental protection emission requirements.
4. Product advantages: it can flexibly produce 32% and 48% liquid caustic soda and 96% and 99% flake caustic soda, which can meet the differentiated needs of multiple fields such as chemical, textile and papermaking. Through precise control of electrolysis and refining parameters, the finished caustic soda has features such as high purity, low impurity content, stable concentration, industrial-grade standards, stable product quality and strong market competitiveness.
5. Control advantages: equipped with fully automatic DCS intelligent control system, it monitors key parameters such as electrolysis temperature, current, voltage, brine purity, and caustic soda concentration in real time, achieving precise control throughout the entire process. It has automatic alarm and emergency shutdown functions, can be operated remotely, reduces manual intervention, and ensures stable and safe operation of the equipment and uniform product quality.
Empowering the chemical industry with advanced equipment and setting benchmarks with cutting-edge technology, Tianli focuses on the core needs of caustic soda production by ion-exchange membrane method. We provide efficient, environmentally friendly, intelligent, and safe production equipment, leveraging our comprehensive advantages in technology, energy consumption, and environmental protection to provide complete caustic soda production solutions for various industries. It will help enterprises reduce costs and increase efficiency, meet environmental standards, and achieve safe production, jointly promoting the green and sustainable development of industry.