ADAPTATION OF DILUTE MODE LIME DUAL ALKALI SCRUBBING AT STILL WATER MINING COMPANY'S PGM SMELTER

摘要

The Stillwater Mining Company (SMC) has operated a platinum-group-metals (PGM) smelter in Columbus, Montana since 1990 to process concentrates produced at its nearby mines. In 1998, SMC embarked on a two-phase project to triple smelter capacity through essentially a complete replacement of the existing facility. Dilute mode lime dual alkali (LDA) technology was selected for meeting the stringent control requirements established for both sulfur dioxide and sulfur trioxide emissions. This same technology had been used in the existing plant and had demonstrated the capability for meeting similar, difficult challenges of handling very high peak levels of sulfur dioxide and sulfur trioxide as well as wide and rapid fluctuations in gas flow and concentrations. Unlike the dilute mode LDA system in the existing facility, though, a streamlined dilute mode LDA concept was envisioned for the new facility. The approach would greatly simplify the design and at the same time significantly reduce both capital investment and operating costs, plus achieve both objectives without sacrificing environmental performance. A joint effort of SMC, the technology supplier and the engineering/design firm has resulted in the successful implementation of this new adaptation of dilute mode LDA technology. The first phase of the expansion was completed in November 1999, and the second phase in November 2001. Over this period, several operational adjustments have been undertaken to optimize process performance such that it is now meeting or achieving all performance expectations - 99.5% sulfur dioxide removal and greater than 90% sulfur trioxide removal. Production of a high-purity gypsum byproduct is now being sold as an agricultural soil amendment and has been qualified for use in cement manufacture.