Conversion from Halogen Bath to Environment-Friendly Methane Sulfonic Acid (MSA) Bath in Electrolytic Tinning Line (ETL) at East Japan Works (Chiba), JFE Steel

摘要

In response to stricter regulations on the concentration of fluoride (F) dissolved into water from wastes enforced in the year 2000, JFE Steel's East Japan Works (Chiba) performed a costly detoxification treatment for F-containing halogen sludge discharged from the electrolytic tinning line (ETL), and at the same time, JFE Steel began study of a project to convert this line from a halogen bath process to a low environmental load methane sulfonic acid (MSA) bath. In this changeover, first, the literature on the MSA process was reviewed and MSA tinplate was evaluated experimentally in the laboratory. Tin mill black plate (TMBP) produced by JFE Steel at East Japan Works (Chiba) was then sent to U.S. makers who had already converted to the MSA-ETL process in order to evaluate MSA tinplate produced under industrial conditions, and operational data were collected using JFE Steel's No. 1 ETL at East Japan Works (Chiba). Quality and operational differences between the halogen and MSA baths were identified through these tests, and remodeling of the existing equipment and introduction of new equipment were carried out to overcome these problems. Operation of the modified line producing tinplate with a MSA bath began in January 2005. As a result, none of the feared quality or operational problems have been encountered, and the electrolyte cost, including tin, has been greatly reduced from the initial plan.