GB764414A - Steam generating unit - Google Patents

Abstract

764,414. Combustion apparatus. RILEY STOKER CORPORATION. Jan. 13, 1955, No. 1057/55. Class 51 (1). [Also in Group XIII] A water-tube boiler has a generating-tube lined furnace 11 the upper part of which is divided into four compartments 73 ... 76, Fig. 3, by water walls formed of tubes which extend inwardly from vertical headers 40, 43 located outside the front and rear walls respectively of the furnace and then upwardly to its roof 23 along which they are led to the steam and water drum 17 of the boiler, the water walls extending up through a furnace nose 89 to divide the lateral outlet pass 90 from the furnace into four separate passes. Combustion gases flow upwardly through compartments 73 ... 76 and then laterally through the four passes; the outer passes housing secondary superheater sections 21 whilst the two middle passes house reheater sections 22. The gas streams then unite for downward flow through a pass 26 locating the primary superheater 20 and an economizer 30, the downpass being flanked by gas by-pass passages 81, 82. The gas flow through pass 26 and bypasses 81, 82 is controlled by outlet dampers 87, Fig. 4. Furnace 11 is fired by twenty oil, gas or pulverized fuel burners arranged in four vertical rows, such as the burner row 52, 51, 63, 64, 65, Fig. 2. The two lower burners, e.g. 51, 52, of each row fire into the undivided lower part of the furnace whilst the upper burners, e.g. 63 ... 65 fire into the respective compartments 73 ... 76. Thus by varying the firing rate of the burners firing into compartments 74, 75 the temperature of reheat can be regulated. To correct the rising characteristic of the convection heated reheater sections 22 the rear walls of compartments 74, 75 are lined with radiantly heated reheater tubes 79 which extend between an inlet header 78 and an outlet header 36 from which the steam flows in parallel through the said reheater sections 22. In operation, the temperature of superheat is regulated by adjustment of the by-pass and down-pass dampers 87 whilst reheat temperature is regulated by controlling the firing rate of the selected burners, auxiliary desuperheater controls being provided in both cases for emergency use. The tube platens dividing the furnace provide sufficient water-cooling area therein to cool combustion gases so that ash carried in the gases is dry when it reaches the superheater and reheater surfaces. To prevent damage to the steam heating surfaces during starting up, only the lowermost burners in the outer rows are lit initially, the hot gases by passing the reheater compartments. The superheater sections 21 are partly filled with condensate. When sufficient steam is being returned from the turbine to the reheater additional burners are lit until full operating pressure and normal load is attained.