Otimização do processo de tratamento primário da salmoura em uma planta cloro-soda

Abstract

The Chlorine-Soda industry is one of the largest electrochemical technologies in the world. It is responsible for the production of important commodities: caustic soda and chlorine gas. Its production chain is based on the electrolysis of brine mong the methods adopted, membrane electrolysis has been gaining space in the current market due to its modern and non-polluting technology. However, demands high purity raw materials. Thus, the brine needs to be purified until all the ions present, mainly calcium and magnesium ions, are totally removed, guaranteeing maximum electrolytic efficiency and preserving the membrane cell's life. Purification is done, in some cases, by adding coagulants followed by the decantation step. This work aims to optimize the primary treatment of brine in a chlorine-soda plant, seeking through experimental planning via Minitab® 17 Statistical Software to evaluate the effect of important variables in this process and the establishment of true optimum ones. The variables analyzed are: brine concentration, NaOH and Na₂CO₃ excess, polymer concentration and the calcium and magnesium concentrations ratio (Ca/Mg). Once five variables are explored at two levels (upper and lower), the planning carried out was of the type 25, which corresponds to the number of observations of the response variable. The results show the amount of chemicals that need to be added, avoiding losses, as well as the optimal operation value for each variable and the significance level of it one in the process. At the end, the best operating range was obtained for the production of clarified brine with a concentration of Calcium and Magnesium below 30 partes por milhão.