GB1112372A - Cascade heat exchanger or reactor - Google Patents

Abstract

1,112,372. Contact apparatus. N. J. HASSETT. 17 June, 1965 [17 June, 1964; 15 July, 1964; 18 July, 1964], Nos. 25015/64, 29057/64 and 29626/64. Heading B1F. [Also in Division F4] A contact heat exchanger for heating or cooling falling granular solids by means of a rising gas comprises a casing within which horizontal or inclined shelves are vertically staggered on alternately opposite sides, the shelves extending halfway across said casing, and inlet and outlet means for the gas and for the granular materials being provided at the appropriate ends of the casing. The flow of the granular material is such that it falls freely in thin sheets from one shelf to the next whereby there is a relatively low pressure drop in the gas as it passes through the chamber. The outlet of said chamber is so constructed that the material accumulates at the base thereof effectively to form a gas seal. Two heat exchangers may be arranged one above the other (Fig. 2 not shown) and the granular material e.g. sand, crushed refractories, metal oxides, garnet or zircon said acts as a heat carrier between hot waste gases passing through the upper heat exchanger and air for combustion passing through the lower heat exchanger. The air for combustion is preheated by the sand &c. when it transports the latter from the outlet of the lower heat exchanger to the inlet of the upper heat exchanger via a cyclone separator. For drying wet sand a combustion zone is arranged in the middle of the heat exchanger as shown, the fuel being fed directly to the zone and the air for combustion being admitted at the base of the heat exchanger. The wet sand is dried by (a) removing hot sand from the heat exchanger just above the combustion zone mixing the wet sand therewith and returning the mixture to the heat exchanger just below the combustion zone or (b) mixing the wet sand, by means of a special shelf, with the hot sand in the area just below the combustion zone; or (c) feeding the wet sand directly into the top of the heat exchanger. In cases (a) and (b) a portion of the dry sand is separated off and recycled through the heat exchanger. The time of stay of the sand may be increased by withdrawing the sand from a lower shelf and recycling it through a higher shelf. The two heat exchanger combination is also said to be suitable for absorption-desorption processes and stripping-regenerating operations by provision of heating elements or tubes within the heat exchanger or by passing a heat transfer fluid through hollow shelves.