GB785398A - The method for indirectly heating a fluid - Google Patents

Abstract

<PICT:0785398/III/1> <PICT:0785398/III/2> In the boiler shown, water or other fluid flowing through tube banks 36 is heated by the fluidized bed 14 in which the banks are immersed. The particles of the bed comprise a catalytic material and fuel entering the base of the bed through a pipe 32, a distributer 30 and perforated pipes 34 is oxidized, and consequently consumed, solely by the catalytic oxidation action of the bed material. The material is kept at a catalytically active temperature by heating the air which maintains the bed in a fluidized condition. For this purpose air is forced by a blower 17 up through the bed - entering the latter through a perforated base-plate 12-after being heated to a desired temperature by a burner 18 which is supplied with fuel and air through valve - controlled lines 20, 22 respectively. Gaseous, liquid or pulverized fuel may be supplied to the bed through pipe 32. The water or fluid to be heated is passed to the banks 36 through tubes 42 from a header 38 which is divided into three sections each communicating with a fluid feed conduit 44 through a valve 46. Each tube 42 is provided with a metering device at its inlet. The heated fluid flows from the banks 36 through further tubes 42 to a header 40. The banks 36 are connected to the headers so that the direction of fluid flow across the bed through adjacent banks is respectively reversed. The combustion gases arising from the bed may be conveyed over additional heat exchange surface or passed through a fluidized bed of inert material within which a heat exchange surface is disposed. The combustion gases may be passed through a cyclone separator. Particles of fused silica, sands, clays, &c. may be added to the fluidized catalytic bed. The material forming the bed may comprise activated forms of metal oxides such as alumina, beryllia, thoria, zirconia, or magnesia, or mixtures of these oxides, impregnated with minor amounts of finely divided metals such as platinum, palladium, rhodium, ruthenium, silver, copper, chromium, manganese, nickel, cobalt, or combinations of these metals such as a silverchromium, copper - chromium, copper - manganese combination. Gamma alumina may be prepared from natural bauxite by removing the impurities such as iron and silicates then heating at a temperature below about 2000 DEG F. to drive off the combined water. The amount of metal when impregnating with a silver-chromium combination to form a suitable catalyst is from 2 per cent to 5 per cent by weight based on the weight of the activated metal oxide. In a described example, a bed consists of pellets of activated alumina impregnated with 0.2 per cent by weight of platinum, the pellets being in the shape of cylinders having a diameter and length of about 0.086 inch.