Experimental Study On The Treatment Of Open Circulating Cooling Water By Membrane Electrolysis Technology

The open circulating cooling water system is an important part of industrial production,and its water consumption accounts for more than 80%of the total industrial water consumption.During the operation of the open circulating cooling water system,there will be problems of scaling,corrosion,and bacteria and algae growth,which will affect the normal operation of the system and endanger production safety.The traditional chemical treatment of circulating cooling water has mature technology and stable descaling,but it will cause secondary pollution to the water body and bring environmental hazards.Electrochemical technology is an emerging environment-friendly treatment technology with low operating cost,good descaling effect,and good application prospects.This paper uses membrane electrolysis technology to treat circulating cooling water,studies the effect of different influencing factors on the descaling effect,and analyzes the operating mechanism and operating economy of the reactor.By designing an orthogonal experiment with four factors and three levels,the paper compares and studies the influence of each factor,and obtains the optimal operating parameters of the electrochemical reactor within a certain range:the distance between the plates is 15mm,the voltage is 10V,the hardness of the influent water is 800mg/L,and the hydraulic retention time is 16min;Influence degree:initial hardness of influent water>voltage>hydraulic retention time>plate spacing.Under the operating parameters,the influence of the material and structure of the electrode plate on the electrochemical descaling effect was studied.The experimental results show that the scale removal effect of the cathode plate material is:titanium-based ruthenium-iridium coating>stainless steel>titanium;the scale removal performance of the cathode plate mesh structure is better than that of the plate structure;the anode plate structure has no significant effect on electrochemical scale removal influence.Under the optimal parameters obtained from the orthogonal test,the effects of anionic and cationic membranes on the descaling effect of the reactor were comparatively studied.Then single-factor experiments were carried out to study the influence of current density,hydraulic retention time,electrode spacing and anolyte sodium chloride concentration on the hardness removal effect and operating energy consumption of the membrane electrolysis reactor,and the hardness removal rate and specific energy consumption were combined.The optimal level of each influencing factor of the reactor is determined:the current density is controlled between 20A/m2and 25A/m2,the hydraulic retention time is 14min,the plate spacing is 12mm,and the anolyte sodium chloride concentration is 4%.The reactor was operated at the optimum level of each factor,and the operating mechanism of the membrane electrolysis reactor was analyzed through the changes of p H,conductivity and cell voltage in the cathode and anode chambers during the operation of the reactor.The ionic membrane in the membrane electrolysis reactor can enrich OH^-in the cathode chamber,increase the p H of the solution in the cathode chamber,promote the conversion of HCO₃^-into CO₃^2-,make the supersaturation of CaCO₃ in the solution exceed the threshold of the supersaturation region,and accelerate the crystallization process of CaCO₃,improve the hardness removal rate;at the same time,due to the chain transfer of H⁺and OH-between adjacent water molecules,the electrical mobility is much higher than that of other ions,so the conductivity increases and the cell voltage decreases during the operation of the membrane electrolysis reactor.Finally,the descaling effects of different electrochemical reactors under the same working conditions are compared and studied.The experimental results show that both the anion membrane and cation membrane reactors have a good hardness removal effect,and at the same time,the specific energy consumption is lower,d during the electrolysis process,the anion membrane reactor has a good removal effect on Cl-in cooling water while descaling,while the anode effective chlorine production of the cation membrane reactor is higher than that of the anion membrane reactor.