GB736175A - Improvements in or relating to a boiler installation and method of generating and heating steam - Google Patents

Abstract

736,175. Forced flow water tube steam boilers ; steam superheaters. COMBUSTION ENGINEERING, Inc. June 12, 1953 [Oct. 17, 1952], No. 16216/53. Classes 123 (2) and 123 (3). A forced-circulation steam generating and heating unit has two separate furnaces, a superheater furnace SF and a reheater furnace RF which are respectively fired by pulverized fuel burners B<SP>1</SP> . . . B<SP>4 </SP>and B<SP>5</SP> ... B<SP>8</SP>, the burners being of the corner-mounted, tangential, tilting type and being fed with fuel and primary air from pulverizing mills M<SP>1</SP> ... M<SP>8</SP>, secondary air being supplied by fans 72, 72<SP>1</SP> through heaters 65, 65<SP>1</SP> to windboxes W in which the burners are mounted. The side walls of both furnaces are lined from top to bottom with steam generating tubes WT which extend between lower headers 15 and a steam and water drum 17 whilst the lower portions only of the front and rear walls of the furnaces are lined with generating tubes WT<SP>1</SP>, these tubes extending from headers 15 to headers 19 from which upcomer tubes 20 lead the steam-water mixture to drum 17. Headers 15 are fed with water from drum 17 through downcomers 21, circulating pumps 22 and pipes 23. The upper parts of the front and rear walls of furnaces SF, RF are lined respectively with radiant superheating tubes ST and radiant reheating tubes 39, 40. Combustion gases leave the furnaces through respective lateral passes 34, the pass from furnace SF housing high temperature convection superheaters HS, HS<SP>1</SP> whilst that from furnace RF locates a convection reheater CS and superheater HS<SP>2</SP>. The gases then flow downwardly through outlet passages FO, FO<SP>1</SP>, each locating one of the halves LS, LS<SP>1</SP> of a low temperature primary superheater and of an economizer E, E<SP>1</SP> and pass through the air heaters 65, 65<SP>1</SP>, dust precipitators 66, 66<SP>1</SP> and induced draught fans 67, 67<SP>1</SP> to the stack. The steam from drum 17 passes through the superheater tubes ST to an upper header 30 whence it flows through pipes 52 to an inlet header 53 common to both sections LS, LS<SP>1</SP> of the primary superheater through which sections the steam then flows in parallel, the flows from superheater sections LS, LS<SP>1</SP> passing respectively through intermediate superheaters HS<SP>1</SP>, HS<SP>2</SP> and then uniting for flow through the final superheater HS to the final outlet header 58. Steam to be reheated is led into headers 41, 42 for flow through the wall lining tubes 39, 40 and the convection reheater CS to the reheated steam outlet header 44. The temperature of superheat and reheat is maintained constant over a wide load range by regulating the fuel feed rate and degree of tilt of the burners and by recirculating flue gas to the furnaces, the flue gas being withdrawn from passages FO, FO<SP>1</SP> respectively by fans 64<SP>3</SP>, 64<SP>4</SP> and passed through ducts GRD, GRD<SP>1</SP> to furnace inlets GO, GO<SP>1</SP> located below the burners. The unit is suspended from overhead girders 38, the space left between the separate furnaces locating an intermediate row of support columns 105, so that the span between the outer columns 103, 104 is decreased and the size of the girders 38 can consequently be greatly reduced.