GB1027202A - Improvements in or relating to catalytic burners - Google Patents

Abstract

1,027,202. Catalytic burners. WHIRLPOOL CORPORATION. July 30, 1963 [July 30, 1962 (3)], No. 6922/65. Divided out of 1,027,201. Heading F4T. [Also in Division B1] A catalytic burner for generating a products of combustion atmosphere includes an enclosing frame having a chamber formed therein, support means in the frame for supporting a granular catalyst bed in the chamber, and mounting means for loosely retaining the support means relative to the enclosing frame whereby the support means is substantially free to move toward and away from the enclosing frame. Gaseous hydrocarbon fuel admitted through a line 22, Fig. 1, and air pumped by a blower 21 are mixed in the region of respective adjustable orifices 33 and 37 and the gaseous fuel is then burnt in the air in a catalytic burner 20 operating at a temperature below 2000‹ F., whereby the formation of oxides of nitrogen is avoided. A balancing regulator 31 provides for varying the volume flow of the gas supply directly with the volume flow of the air supplied, so that a constant fuel-gas ratio is achieved. Minimum fuel-gas and air pressures are controlled by a gas switch 28 and air switch 41 at 5À5 and 3À3 inches of water, respectively. If the air pressure in the air-gas regulator 31 is excessive, e.g. above 4À5 inches of water, the safety switch 42 will shut-off the apparatus. Thermostats 62 and 72 shut-off the apparatus if the water-circulating line is overheated, e.g. at above 135‹ F. A standard ignition control system is utilized for starting up the burner by spark plugs 75. When an outlet sensor 78 has sensed a predetermined minimum temperature of about 700‹ F., it causes the operation of the spark plugs to be stopped; if the temperature is not achieved in 45 seconds, both the ignition circuit and the gas supply will be cut off. After about 15 minutes for warming up, an inlet sensor 77 will have reached a predetermined temperature of 800‹ F. signifying normal operation of the burner. The flow of fuel is interrupted by actuation of a flashback sensor 76 if combustion takes place outside the catalytic bed. The burner includes an enclosing rectangular frame 132, Fig. 9, top and bottom closure members each provided with a serpentine passage through which cooling water circulates, and a 10 x 10 mesh wire screen 159 which is provided with spaced parallel embossments extending lengthwise of the screen and is mounted for relative movement between upper and lower spaced flanges 161 and 162. The bed 158 of catalyst and the supporting screen 159 are supported on transverse rods 163 loosely held by brackets 165, Fig. 7, fastened to the frame. The screen is loosely tied to the rods by wire ties 169. The arrangement thus permits movement of the screen and rods towards and away from the enclosing frame 132 under the expansion and contraction due to heating and cooling. A central rod, however, is mounted in partially encircling brackets which limit the lateral movement of the rod but still permit movement longitudinally. Suitable catalysts are #-inch extruded pellets of chrome-alumina containing about 20% chromic oxide and platinum alumina. The burner is preferably operated at a maximum temperature of about 1600‹ F.; the minimum temperature at the centre of the catalyst bed must be about 1200‹ F. for complete combustion.