Analysis of Methanol Based Chlorine Dioxide Production : An analysis of sodium chlorate reduction efficiency and investigation of salt cake filter wash on an SVP-LITE® system

Abstract: This work aimed to determine how effective an SVP-LITE® chlorine dioxide plant at Vallviks Bruk was running. This was done by determining the chemical consumption per unit of chlorine dioxide produced. The calculations relied upon online instrumentation that was manually validated. The most important parameters were the conversion ratio of sodium chlorate into chlorine dioxide and the specific consumption of sodium chlorate, methanol, and sulphuric acid. The salt cake filter and dissolver were also examined to determine their impact. The total conversion ratio of sodium chlorate during a whole ECF (Elementally Chlorine Free) campaign were 93.12 %, somewhat lower than the target efficiency of 95.64 %. The specific chemical consumption was 1.695 kg sodium chlorate, 0.183 kg methanol, and 1.007 kg sulphuric acid per kg produced chlorine dioxide. The salt cake filter worked as intended to remove excess sulphuric acid, with the precipitate having the same sulphate and acidic content as the wanted form of sodium sesquisulphate Na3H(SO4)2. However, some sodium chlorate can get through, and the mean concentration in the dissolver was 1.3 g/dm3, equal to approximately 4 tons lost during a campaign. The filter may be more efficient in redissolving acidic species than chlorate salts. The reactor could theoretically be run more efficiently, but its production parameters is close to what is expected of such a plant.