GB609674A - Improvements in or relating to tubulous vapour generating and heating units - Google Patents

Abstract

609,674. Water-tube steam &c. boilers; steam superheaters. BABCOCK & WILCOX, Ltd., and ZOLLER, R. E. March 20, 1946, No. 8632. [Classes 123(ii) and 123(iii)] A marine steam &c. boiler, Fig. 1, comprises a furnace with two separately-fired furnace chambers 6, 7 divided by a wall 8 and provided with individual gas outlet passages 18, 22 between which and the said chambers respectively are located banks of steam-generating tubes 4, 5 extending between an upper steam-and-water drum 1 and lower water drums 2 ,3. The tube banks 4, 5 are each constituted by upper and lower sections 4a , 4b and 5a, 5b between which are defined spaces locating, in the bank 4, a first superheater section 24 and, in the bank 5, a second superheater section 30 and a reheater 31. In operation, steam is led from the drum 1 by a pipe 41 to the superheater section 24 and from thence by a pipe 42 to the section 30, some of the steam from the section 24 being, if desired, cooled by passage through desuperheating pipes 43 disposed within the water drum 3; simultaneously, steam from between stages of an associated prime mover is circulated through the reheater 31. The arrangement is such that, during ahead working, both furnaces are fired at an aggregate rate corresponding to the necessary steam output and pressure, the relative rate of firing the furnace 7 being adjusted to the required temperature of reheat and the superheat temperature being regulated by valves 44, 45 which are fitted in the pipe 42 to control the steam flow through the desuperheater 43, but during astern working, when no reheat is required, only the furnace 6 is fired so that the superheater section 30 and reheater 31 becomes ineffective. The wall 8 preferably comprises a row of studded tubes which extend from the drum 1 to a header 10 below the floor of the furnaces and are covered with refractory material applied in plastic condition; such material is also applied to the uppermost row of tubes in the lower sections 4b, 5b of the banks 4, 5 to form baffles 28, 29 and 37, 38, 39 to prevent furnace gases by-passing the superheater sections and reheater. The superheater section 24 preferably comprises two rows of looped tubes extending between headers 25, 26 at the rear of the boiler, the section 30 five rows of tubes connecting headers 32, 33, and the reheater six rows of tubes connecting headers 35, 36, these three units being secured in place by plates mounted on tube rows 27, 34 extending within the banks 4, 5 between the sections thereof. A two-part economizer 19, 23, as described in Specification 551,700 for example, may be located in the gas uptakes 18, 22. The invention may be applied to a boiler in which each of the tube banks 4, 5 has an associated upper steam- and-water drum instead of a single drum common to both banks. In a modification, the desuperheater 43 is dispensed with and the degree of superheat controlled by adjustment of a damper 53, Fig. 4, in a gas by-pass formed by a wall 50 with a metal extension 51 which divides the tube bank 4 into front and rear portions 4a<1>, 4b<1> and 4a<11> and 4b<11>, the first superheater section 24 being located wholly between said tube bank portions 4a<11>, 4b<11>.