GB772814A - Improvements in evaporators for steam generators operating according to the loefflersystem - Google Patents

Abstract

772,814. Direct contact steam boilers. FOSTER WHEELER, Ltd. Oct. 21, 1955 [Dec. 3, 1954], No. 35123/54. Class 123(2) In a Loeffler boiler wherein a major proportion of steam which has been highly superheated in a furnace is used to generate saturated steam in an evaporator, the remainder being delivered as the boiler output, and the saturated steam is dried and circulated to the superheater by means of a compressor, the superheated steam at about 1000‹F. passes from an inlet header 15 disposed in the evaporator drum 10 through a nest of tubes 12 in indirect heat exchange contact with the water in the drum and enters a header 13 at about 650‹F. with some 20‹F. superheat. About 9/10 of the desuperheated steam flows from the header 13 directly to the evaporator outlet 22 through a pipe 14. The remainder is directly injected into the water in the drum through ejector nozzles 16 which ensure a flow of water over the tubes 12. The steam-water mixture from the nozzles flows into centrifugal separators 18 whence the steam passes to the outlet 22 through chevron driers. 20. With this arrangement the steam drying apparatus has to deal with the generated secondary steam but with only a small proportion of the primary steam so that its bulk may be correspondingly reduced. In modifications, the primary steam injected into the water is pre-cooled in separate tubing and circulation in the drum is promoted by feedwater nozzles or by convection circulation between a drum containing the desuperheaters and a superposed drum housing the steam-drying apparatus.