Bi-gas pilot plant gasifier operation Tests G-3 through G-3G

Abstract

This is the fourth of a series of operating reports to describe pilot plant activities, to present data and conclusions, and to make recommendations appropriate to that operation. This report focuses on the operation of the 2-stage, entrained-bed, high pressure (1500 psig max), oxygen blown, and ash slagging gasifier during eight separate tests (G-3 through G-3G). Subbituminous coal from the Rosebud seam of the Western Energy Company's mine at Colstrip, Montana, was fed to Stage II of the gasifier with Winfield limestone flux during each test. The specific objective of Tests G-3 through G-3G was to determine if slag tapping could be improved if limestone flux was added to the coal feed. Because they shared the same specific objective, Tests G-3 through G-3G were grouped together for presentation. Other objectives are described briefly. With the measures taken during these tests, the slag tapping problems of previous tests were largely overcome. The improved slagging could not be attributed solely to the addition of limestone flux: two other changes had also been made (reduction of water cooling near the tap hole and lengthening of the tap burner) and whether the improved tapping resulted from one or a combination of these changes could not be concluded. The ability to keep the tap hole open did permit tests of longer duration which thereby allowed more of the objectives to be attempted. Although slag tapping was significantly improved, a number of other problems plagued gasifier operation. These included: inadequate solids flow measurement instrumentation, numerous involuntary burner shutdowns, buildups of slag in Stage II, and recurring damage to the burner which resulted in cooling water leaks in Stage I.