Recent Developments in the Burning of Anthracite

Abstract

Abstract The anthracite referred to is that of which at least 95 per cent will pass through a 3/16-in. round-mesh screen and less than 20 per cent through a 3/32-in. round-mesh screen. The coal was burned on Coxe stokers. The paper describes successive furnace designs made at the Amsterdam (N. Y.) steam station of the Adirondack Power and Light Corporation. The boilers are of Babcock & Wilcox design and of 1345 hp. Each boiler has two Coxe stokers. Attempts were made to improve on the customary furnace design to which the following objections are made: (a) tendency to stratification of gases, (b) high carbon content of ash, (c) loss of fines to ashpit and stack, and (d) lack of flexibility. The first experimental furnace had, in addition to the ignition arch, a very short arch over the rear of the grate. With this arrangement improvement, if any, was slight. A three-arch furnace was then built, with better results but with defects due to slagging. A third furnace of two-arch design was finally constructed. Tests reported in the paper show that with the final design stratification can be practically eliminated, as well as ignition troubles, even with low-grade coal. A decided improvement has also been made in the burning of undersizes. Greater capacity was obtained with low-grade coal (60 per cent undersize and 33 per cent ash) in the multiple-arch furnace, where 300 per cent of rating was easily reached, than in the single-arch furnace where 190 per cent was about the limit. The boilers and furnaces are described and illustrated, and a description of the tests with the principal data and results are given in the form of curves.