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If the ion membrane is to ensure its stable and efficient current efficiency for a long time, the most critical part is the operation of the electrolytic cell. The lifetime of the ionic membrane is affected by the salt water, so the high current density operation will further reduce the efficiency. The electrolytic cell has a cation exchange membrane, so it has the characteristic of being able to permeate the solution. When Ca2+, Mg2+ and other multivalent cations pass through the exchange membrane, they will precipitate with a small amount of OH- migrated back from the cathode chamber to form hydroxide precipitation, which will increase the membrane resistance and block the ion membrane, which will cause the electrolytic cell to appear voltage. The elevated condition, therefore, alters the anti-migration and further reduces the efficiency of the current. Therefore, this paper discusses the current efficiency of ion-exchange membrane electrolyzers as follows.
If the ion membrane is to ensure its stable and efficient current efficiency for a long time, the most critical part is the operation of the electrolytic cell. This operation can change the relevant current amount, prolong the service life of the ion membrane, and further prevent the ion membrane from being damaged, thereby improving the quality of the product, and at the same time, it can reduce the voltage of the electrolytic cell and improve the current efficiency.
1 Influence of brine quality on current efficiency
The service life of the ionic membrane is affected by the salt water, so the high density operation of the current will further reduce the efficiency. The electrolytic cell has a cation exchange membrane, so it has the characteristic of being able to permeate the solution. When Ca2+, Mg2+ and other multivalent cations pass through the exchange membrane, they will precipitate with a small amount of OH- migrated back from the cathode chamber to form hydroxide precipitation, which will increase the membrane resistance and block the ion membrane, which will cause the electrolytic cell to appear voltage. The elevated condition, therefore, alters the anti-migration and further reduces the efficiency of the current. It can select and pass through Na+ in brine, and other cations such as Ca2+, Mg2+, etc. can also pass through.
The chlor-alkali workshop of Shanna Synthetic Rubber Group Company (hereinafter referred to as / Shanna Company 0) requires that the sum of the mass fractions of Ca2+ and Mg2+ in the secondary brine in actual production is less than 20g/l, because when the sum of the mass fractions of Ca2+ and Mg2+ is When 50 g/l brine enters the electrolytic cell twice for 24 h, the current efficiency drops rapidly by 5% each time, and the voltage rises by 100 mV or more. If the brine with high Ca2+ and Mg2+ content is supplied for a long time, the current efficiency will be significantly reduced, thus affecting the accumulation. For ionic membranes, the lifetime is further shortened. Therefore, it is necessary to control the use of salt water in order to protect the life of the ion membrane, and to carry out special training for the relevant operators. In particular, it is necessary to carry out relevant pre-job training and learning. Therefore, continuous training and the ability to calculate the relevant brine components, control the amount of use within the range that does not damage the ionic membrane. In this way, the influence of brine on the life of the ion membrane can be reduced, thereby prolonging the service life of the ion membrane.
2 Influence of NaOH concentration in catholyte on current efficiency
According to relevant data, there is a maximum relationship between NaOH concentration and current efficiency. 
Therefore, the continuous increase of NaOH will make the water content of the cathode side relatively low. Therefore, the concentration will increase relatively. If the concentration continues to increase and there is no tendency to decrease, the OH- concentration in the membrane will increase. When the mass fraction of NaOH exceeds 36%, the influence of the increase in the OH- concentration in the membrane will play a decisive role. , This will reduce the efficiency of the current and affect the electricity consumption. Therefore, for the concentration of the solution, in order to achieve the relevant balance requirements, the NaOH mass fraction of the lye at the outlet of the tank should be controlled at 32%~35%. Analysts and operators need to monitor and analyze various data, so that the concentration of the solution and the situation of the electrolyte can be further considered. Perfect balanced coordination mode, so that the formed current can be properly considered and analyzed.
3 Influence of anolyte NaCl concentration on current efficiency
The NaCl concentration in the anolyte has a very obvious effect on the current efficiency, so the current efficiency decreases with the decrease of the NaCl concentration, and the continuous decrease of the brine concentration will increase the water content of the ion membrane, which will decrease the current efficiency. That is to say, there is a positive relationship between the use of brine and the ion membrane, which is a natural circulation, and the NaCl mass concentration of the anolyte at the outlet of the electrolytic cell is controlled to be 200~220 g/L. It can be seen from the operation of the past few years that the management of the electrolyzer needs to be put in place to be able to skillfully determine the ratio of various solutions. Further improve the use concentration of the cathode and anode solutions, so as to extend the service life of the ion membrane and improve the current efficiency of the electrolytic cell.
4 Influence of current density on current efficiency
In life, there are many cases of load changes in the current, and the voltage will also change greatly. Therefore, the ion membrane is affected by the salt water to a certain extent, especially in its later operation, if the current frequently rises or falls, it will cause The volume fraction of oxygen in chlorine and hydrogen in chlorine in the unit cell increases, even rapidly, and the current efficiency decreases by 4%~5%. Shanna Company has seen that the efficiency of individual cell membranes has dropped to 88%, and the ion membrane needs to be replaced. Therefore, ensuring the stability of the current is the basis for ensuring the smooth operation of production and the development of work, that is, the basis for protecting the ion membrane. The current stabilization can prolong the life of the ion membrane, which has positive significance for long-term stable development and can further save costs.
5 Influence of the temperature of the electrolyte on the current efficiency
According to the data, when the electrolysis temperature drops below 65°C, the current efficiency drops rapidly, and it is difficult to restore the current efficiency to the original position even if the temperature rises again. This is related to the temperature range of the ion membrane. In this range, the increase of the temperature will increase the pores on the cathode side of the ion membrane, increase the number of sodium ion migration, and contribute to the improvement of the current efficiency. In daily production, the bath temperature and pressure of Shanna Company are monitored by the DCS control room, and the technicians have strengthened the on-site inspection. The operating temperature of Shanna Company's Asahi Chemical Film is 882 ℃, which changes with the current density. The operator will keep on-site work records and investigations at all times, and will carry out various measurements on the user's temperature in detail, that is, to ensure that the temperature is stable within the control index, so as to minimize the current consumption and save costs. and increase efficiency.
6 Summary
In general, the operation of the ion-exchange membrane electrolyzer plays a crucial role in prolonging the life of the ion-exchange membrane. Due to the relatively high price of the membrane, it is necessary to further save costs and improve the efficiency, so as to prolong the life of the ion-exchange membrane. Avoid major accidents and do not affect the electrolytic performance of the ion membrane, so that the current efficiency can be further improved, and the use of the ion membrane can be maximized. Only by controlling the operating conditions of the relevant electrolyzers and improving the quality of the operators can the improvement and stability of the entire process system be achieved, the efficiency of use can be further improved, and the work can be done more with less. For this reason, more research is needed to refine the discussion of ion-exchange membrane cell operation, advance experience, and improve work.
