Recording ASH-PIT Loss From Chain-Grate Stokers

Abstract

Abstract This paper presents certain preliminary data obtained from a device recently developed to record the ash-pit loss from chain-grate stokers and thus enable firemen to effectively control this factor. The device consists of a steel tube or bulb filled with nitrogen and connected through a capillary tube to a recorder consisting of a mercury U-tube, one leg of which is open to the atmosphere and carries a float to which the recorder pen is attached. It has been found that when this bulb is properly located near the rear of a chain-grate stoker, its temperature will respond definitely to changes in the amount of combustiable going to the ash pit and will vary in direct proportion to the heat thus lost. Records of ash-pit loss, excess air, unburned gas, flue-gas temperature, and boiler rating make it possible to plot characteristic performance curves for stokers showing the losses due to unburned combustible, unburned gases and excess air, and to determine the proper amount of excess air to be maintained and also the most efficient capacity. These curves can be used to compare the relative efficiencies of different types of stokers, the suitability of different kinds of coal, and the effectiveness of the control by the fireman.