GB884131A - Improvements in and relating to solid-fuel combustion appliances - Google Patents

Abstract

884,131. Boiler furnaces. C.U.R.A. PATENTS Ltd. April 21, 1959 [March 4, 1958], No. 6972/58. Class 51 (1). A method of operating a solid-fuel furnace having a moving grate comprises detecting variations in the temperature of a body situated within a region over the rear end of the fuel-supporting part of the grate and varying the total rate of supply of primary air and/or the distribution of the primary air along the length of the fuel-supporting part of the grate in accordance with the variations. Apparatus for carrying out the invention in a solid fuel boiler furnace having a chain grate 1 comprises pivoted dampers 16, 17, 18 mounted in partitions 6, 7, 8 of an air chamber beneath the grate for regulating both the total rate of supply of primary air to the grate and the distribution of the supply over the length of the fuel-supporting portion of the grate. A piston-rod 21 operated by a bellows (not shown) in a vessel 28 controls the dampers and is responsive to the temperature of air within a U-tube 34 situated within a region over the rear end of the grate and effective upon an increase in the temperature to open the dampers successively from front to rear and also increase the degree of opening of any of the dampers already open so as to allow primary air to the grate progressively towards the rear of the grate and an increase in the temperature to decrease the degree of opening of any damper already open and to close the dampers successively from rear to front. From the outlet side of a fan (not shown) which supplies through a conduit 32 to the air chamber a tube 33 leads through the chamber and the partitions to the U-tube 34 and thence by a tube 35 back through the chamber beneath the tube 33 to a port in the chamber which gives access to a hollow member 31 and by a tube 36 to the inlet side of the fan. Thus, when the fan operates the pressure difference across it causes air to flow through pipes 32 to 36. When the air in the U-tube is heated and passes to a member 31 it heats a phial 30 therein which is part of a closed system comprising the space between the bellows and vessel 28, a tube 29 and the phial. Liquid in the system expands to compress the bellows and thereby moving the rod rearwardly to operate the dampers. An increase in the rate of fuel supply, which is determined by the water temperature, automatically increases the rate of air supply and the length of grate which is operated since the fuel bed approaches the U-tube with consequential greater heat thereto which automatically opens the dampers. Secondary air is supplied over the front portion of the grate by means (not shown) which comprises a duct from the fan having a valve which is controlled by additional temperature-responsive means connected to the U-tube. In a modification, the bellows vessel 28, tube 29 and phial 30 may be replaced by a bi-metallic element operated by the action of heat from the tube 35.