Patent GB-377305-A (GB)
Abstract: 377,305. Regulating fuel and air supply to furnaces. ROSSMAN PATENTS, Inc., 20, N. Wacker Drive, Chicago, U.S.A. Jan. 28, 1931, No. 2836. Convention date, Jan. 29, 1930. [Class 51 (i).] A control system for one or more furnaces comprises controlling motors for the fuel and air supply which are adjusted by normally inoperative control motors which receive simultaneous impulses from a main control device, while the air feed control motors receive individual control impulses from auxiliary control devices responsive to the conditions of combustion, the relative rates of response of the controllers being set by adjustable resistances in the circuits of the control motors. In applying the invention to one or more boiler furnaces 3, Fig. 1, coal is fed by feeders 10 driven by motors 12 to pulverizers 7 delivering to burners 5, air being supplied to the burners and to the pulverizers by forced draught fans 22 driven by motors 23 and the waste gases being withdrawn by induced draught fans 30 driven by motors 32. Steam and air flow and CO2 meters 31, 34 and pressure gauges 2, 33 for steam and furnace gases are provided. Any departure of the steam pressure from the normal as indicated by the master control or pressure gauge 2 causes the operation of rheostat adjusting motors for varying the speed of the motors feeding the fuel and air while any departure from normal of the efficiency of the plant as indicated by the meter 31 or any fall of pressure in the furnace from the normal causes operation of the rheostat adjusting motors for the motors supplying air to the exclusion of control by the master control 2. In order to effect intermittent adjustments in the fuel and air supplies and for periods depending on the departure of the steam pressure from normal the timing controller 89 shown in Fig. 2, Part III, is employed. It comprises a motor 94 driving through gearing a shaft 102 carrying discs 97, 104 provided with conducting segments 98, 105. The field of the motor is excited from the mains 100 while the armature 99 is connected to the mains through the brushes 96 bearing on the disc 97 or through a shunt comprising a rheostat 90 adapted to be varied by boiler pressure. When the segment 98 bridges the brushes 96 the motor rotates at maximum speed and as soon as the segment 98 opens circuit between the brushes, the rheostat 90 controls the speed of the motor in accordance with the departure of the steam pressure from normal. The disc 104 operating in synchronism with the disc 97 opens and closes the circuits including the mains 100 brushes 106 pressure gauge pointer 109 and either one other of the relays 114, 115 to close one or other of the switches 116, 117 to permit current to flow to one or other of the increase or decrease control wires 127, 128 and 129, 130, Fig. 2, Part I. The latter wires are connected through load division relays such as 132, of each of the boilers to a switch 138 and increase and decrease control wires 149, 150. The energization of either of these wires effects the operation of one or other of the relays 153, 154 to operate switch 155 or 156 and permit current to flow from the constant potential leads 75 to the armature 76, of the rheostat adjusting. motor 73 and cause its rotation in one or other direction to vary the rheostat 69 and field 68 of the motor generator 65 which delivers current at variable potential to the fuel-feeding motors 12. The master controller or pressure gauge 2 also operates through the control wires 149,150, motors 56, 62 for adjusting the rheostats 53, 58 to vary the speed of the motors driving the induced and forced draught fans 30, 22 respectively. Individual rheostats 77, 78, 79 are provided in the circuits of the motors 73, 56, 62 to adjust the rate of fuel supply with respect to the air supply. The efficiency meter 31 and furnace pressure gauge 33 are adapted to vary the rheostat adjusting motors 56, 62 while at the same time the master control is cut out from the control circuit. The control of the rheostats 69, 53, 58 may be effected by hand and the fuel and air supply to the various boilers may be adjusted by hand or automatically. Specification 351,110 is referred to.