Ash deposition during direct limestone injection for sulfur dioxide control at 50-MW power plant

A test program evaluating sulfur removal by furnace limestone injection was conducted at the Otter Tail Power Company's Hoot Lake Station. The program was conducted by Radian Corportation under Department of Energy (DOE) sponsorship. The test program consisted of individual tests during which limestone was injected into flue gas at temperatures ranging from 2300/sup 0/F to 2400/sup 0/F, and by adding limestone to the coal feed immediately upstream of a pulverizer and subsequently conveyed to the burners and into the combustion zone. The burners were operated using the burner-out-of-service (BOOS) method to produce a fuel-rich fireball with reduced combustion flame temperatures. Sulfur dioxide removal efficiencies up to 70-pct were achieved. High rates of ash deposition on secondary superheater steam tubes were observed when injecting limestone; however, the deposits were readily removed using normal soot blowing schedules. The present report presents results of ash fouling rate measurements and the chemical and physical properties of the ash deposits.