GB1027201A - Apparatus for providing a controlled atmosphere suitable for food preservation - Google Patents

Abstract

1,027,201. Preserving food. WHIRLPOOL CORPORATION. July 30, 1963 [July 30, 1962 (3)], No. 30260/63. Heading A2D. An apparatus for providing a controlled atmosphere suitable for food preservation includes means for catalystically generating an atmosphere comprising at least carbon dioxide and inert gases, means for removing carbon dioxide from the generated atmosphere and means for directing the resulting gases to a storage chamber. 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. The atmosphere generated is passed through a condenser 23 to an activated carbon absorber 25 for carbon dioxide and the resulting gases are directed to a storage chamber 27 for food chilled to a temperature between 29 and 55‹F. The condenser 23 and the top closure member 63 of the burner are cooled by the flow of water from a line 57. The water then heats in a chamber 65 the air delivered by the blower 21, circulates through the bottom closure member 67 of the burner 20 and finally is run off through a drain 70. The volume flow of water is regulated by a valve 59 controlled by a thermostat 72. Moisture condensed in the condenser 23 is also carried away by the drain 70. Sequential operation of the valves 44, 47, 49, 51 and 55 by electrical circuity, Figs. 2 and 14 (not shown), effects the following sequences: (A) passing the generated atmosphere via lines 24, 43 and 46, through absorber bed 26 and then via lines 48, 50 and 52 to the food storage chamber 27, for 21 minutes; (B1 passing the generated atmosphere directly to the storage chamber 27 via lines 24, 50 and 52 or (B2) passing the generated atmosphere to an outlet 45 via lines 24, 43, 50 and 53 whilst, in either case, hot air passes via lines 35 and 54 to purge the adsorbed carbon dioxide in the bed 26 through line 46 to outlet 45, for 3 minutes; and (C) passing the generated atmosphere via lines 24, 43 and 46, through the absorber bed 26 to remove oxygen entrained during the purging, thence (C1) via lines 48, 50 and 53 to the outlet or (C2) via lines 48, 50 and 52 to the food storage chamber 27, for 3 minutes. 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. When, as sometimes occurs, the products of combustion are in the desired proportions of oxygen, carbon dioxide and inert gases, they are passed directly to the storage chamber 27. A typical atmosphere contains 11% carbon dioxide, 2% oxygen, both by volume, and the balance nitrogen and other inert gases from air. Procedure A+B2+C1 provides a storage atmosphere containing 2% carbon dioxide and 3% oxygen. Procedure A+B2+C1 provides a storage atmosphere containing less than 1% carbon dioxide and 3% oxygen. Procedure A+B2+C2 provides a storage atmosphere containing less than 1% carbon dioxide and 5% oxygen. Finally, procedure A+B1+C2 provides a storage atmosphere containing 2% carbon dioxide and 5% oxygen. In a typical installation, the absorber bed consisted of 250 1bs. of activated carbon, 20 cubic feet per minute of combustion gases at a temperature of 50‹F. were passed through the bed during sequence A and 200 cubic feet per minute of air at 80‹F. were passed through during the regenerating sequence B1 or B2. Atmospheres containing up to 15% carbon dioxide and up to 21% oxygen can be produced by changing the conditions, although the carbon dioxide and oxygen contents are interrelated. Minimum fuel-gas and air pressures are controlled by a gas switch 28 and air switch 41 at 5.5 and 3.3 inches of water, respectively. If the air pressure in the air-gas regulator 31 in excessive e.g. above 4.5 inches of water, the safety switch 42 will shut off the apparatus. Thermostats 62 and 72 shut off the apparatus if the water circulating at these points is over-heated e.g. at above 135‹F. A standard ignition control system is utilized for starting up the burner by spark plugs 75. When the outlet sensor 78 has sensed a pre-determined 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, the inlet sensor 77 will have reached a predetermined temperature of 800‹F. signifying normal operation of the burner. This effects valve changes whereby the gases coming from the burner are diverted from operational sequence B2, utilized during the warming up, to sequence A of the normal operating procedures A-B-C; this subject matter is claimed in divisional Specification 1,027,203. 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 of the burner under the expansion and contraction due to heating and cooling; this subject matter is claimed in divisional Specification 1,072,202 (see Division F4). 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.