GB904758A - Improvements in combustion control of fuel burners for pulverised fuel or other generally opaque fuels - Google Patents

Abstract

904,758. Photo-electric control of burners. AISH & CO. Ltd., KYNASTON, J. R., and HATFIELD, J. C. April 21, 1961 [Jan. 21, 1960], No. 2232/60. Class 40 (3). A system for controlling the combustion of pulverized coal or other generally opaque fuel, such as heavy oil, injected into a furnace from a burner B, comprises two photo-cells 1, 2 located in the furnace wall, respectively, at a position prior to the desired position of combustion initiation and at a position where flame should be established, in conjunction with means responsive to the signal differential from the cells for automatically adjusting the supply of air or fuel necessary to initiate and support combustion at the predetermined position in the furnace. When the flame is correctly established, the cell 2 being illuminated, and the cell 1 being in the dark condition, the cell outputs provide a signal differential in a predetermined sense, and other conditions, such as pre-ignition or failure to ignite give rise to a much different derived, or resultant signal which may be zero, or the respective signals approximately equally balanced. The output from the cells 1, 2 is fed to a thermionic bridge circuit 3 connected to a C.R.T. 4 and to a moving-coil meter 5 for the purposes of display and indications of the positional conditions of the flame. The output of the bridge 3 is also fed to a cold-cathode valve bridge 6 connected by leads 7 to a combustionadjusting device, which may be a motor operating an air supply fan or controlling the fuel supply. A timing circuit 8 can be included so that a warning device 9 is operated if the flame position moves outside the area defined by the photo-cells for a period of time in excess of a predetermined interval. In a modification, a timing device 10 controls the cold-cathode bridge 6 to pass its output over the leads 7 at predetermined periodically occurring intervals to prevent over-correction of the faulty condition. In the case in which the established flame is relatively long, subsidiary control photo-cells may be interposed between the two cells 1, 2 which are located respectively at a point prior to the position of combustion initiation and the point where the flame should be established.