Handling and Co-firing of Shredded Municipal Refuse and Coal in a Spreader-stoker Boiler*

A system for handling up to 120 tons/day of municipal refuse has been developed for co-firing with coal in a spreader-stoker boiler at the Colum­ bus, Ohio, Municipal Electric Plant. This system is unique in that the refuse has undergone only shred­ ding to 90 percent minus 4 in. (10 cm) and magnetic separation of ferrous material. The refuse-handling system comprises: (1) a push-pit with a hydraulic ram for receiving the shredded refuse from a transfer truck; (2) appropriately situated augers and a belt to deliver the refuse to the boiler level; (3) an inter­ face consisting of a hopper, augers, and chutes where the refuse is separated into two streams; and (4) two air-swept spouts to inject the refuse into the boiler. The system was developed to study: (1) combus­ tion of the shredded refuse with coal on a traveling grate; (2) corrosion effects on boiler-tube metals; and (3) environmental effects of the co-firing, with respect to emissions and ash residues. Co-firing of the refuse with high-sulfur coal up to a 60:40 mix on a Btu basis has only slightly increased the initial corrosion rate of boiler tube metals beyond that ·This project has been financed in part with federal funds from the Environmental Protection Agency under Grant No. R-804008-2 from the Municipal and Industrial Re­ search Laboratories, Cincinnati, Ohio. The contents do not necessarily reflect the views and policies of the En­ vironmental Protection Agency, nor does mention of trade names or commercial products constitute endorse­ ment or recommendation for use. 61 attributable to the coal alone. Emissions of sulfur oxides from the high-sulfur coal can be reduced to environmentally acceptable levels by dilution with the refuse (0.25 percent sulfur) and by action of the alkalis in the refuse.