Development of an Automated Continuous Clarification Bypass System To Remove Suspended Particulate Matter

An automated continuous clarification bypass system was developed to remove the suspended particulate matter (SPM) in the prereaction material. Compared to commercially available duty/standby filters, the proposed clarification bypass system is able to self-clean and does not require detachment of the filter and manual cleaning. In a stainless steel (SS) filter, the effects of flow direction, ultrasonication, and viscosity (=f(temperature)) were investigated. The data showed that the filtration performance could not meet the requirement of high clarification efficiency because of the high switch frequency (high switch frequency results from short filtration time before the filter fouls, which is indicated by increasing pressure differential across the filter). The deposition of crystals on the SS filter medium, and not the SPM, was the primary cause of the pressure build-up. Experiments with PTFE filter elements with comparable pore size and surface area to the stainless-steel filter were performed, and improved filtration performance (e.g., after the first cycle, the filtering time was 1–3 min with SS versus 30–60 min with PTFE) was observed. At the beginning of the SPM filtration process with the PTFE filter elements, three filtration mechanisms occurred (i.e., straining, impingement, and entanglement). As the filtration cake formed on the filter element surface, straining gradually dominated the filtration process, while the effects of impingement and entanglement became negligible.