GB781974A - Improvements in or relating to vapour generating plants comprising tubulous boilers - Google Patents

Abstract

781,974. Boiler furnaces. BABCOCK & WILCOX, Ltd. Feb. 28, 1955 [Feb. 26, 1954], No. 5717/54. Class 51 (1). [Also in Group XIII] The space beneath the fuel-bearing surface of the travelling grate 6 of the boiler shown in Fig. 1 is divided into compartments 54 all but one of which is provided with an individually operable damper 56 for the supply upwardly therethrough of primary combustion air whilst the other compartment is adapted to receive further combustion air which has been passed through a humidifier 60. In operation, the combustion air is forced through an air heater 42 and some passes to the humidifier 60 through dampercontrolled line 68, whilst the remainder passes via line 49 and opening 52 into riddling, ash and clinker hoppers 37, 38, 40 respectively for passage up through the damper-controlled compartments 54. The water spray device 64 of the humidifier is fed via line 62 and valve 66 from the cooling water system 36 of a condenser 32 attached to a steam turbine 30 supplied by the boiler. All the compartments 54 may be fed with humidified air, branch lines from the moist air supply line 69 being provided for this purpose. Each branch line is fitted with a damper and these dampers together with the dampers 56 can be set so as to permit either humidified or non-humidified combustion air to any of the associated compartments 54. In a modification, water in the line 62 is passed through a heat exchanger deriving its heat from the closed cooling gas circuit of an alternator. In another modification, water in the line 62 is heated in a heat exchanger which acts as a condenser for steam from a steam jet air pump utilized to extract non-condensable gases from the condenser 32. Fig. 4 shows an arrangement in which moist air or steam is taken from a cooling tower 76 through a line 78 to the air heater 42. Cold, relatively dry air may be admitted to the heater for admixture with the moist air or steam through a damper 80. All the compartments 54 may be supplied with humidified air. This arrangement may be modified by providing a fan to promote a humidified air flow directly to an appropriate part of the grate instead of the supply through line 78. The invention is also applicable to oil or pulverized fuel fired boilers. With the latter fuel usually only a proportion of the secondary air is humidified.