GB935462A - Waste heat boiler - Google Patents

Abstract

935,462. Waste heat steam boilers. HEAD WRIGHTSON & CO. Ltd. Jan. 18, 1962 [Oct. 18, 1960], No. 35746/60. Class 123 (2). In a waste heat boiler installation for maintaining at a constant flow rate a continuous supply of superheated steam to a site main and in which the source of heat supply to the boiler is intermittent, a thermal storage plant is supplied with steam in excess of said flow rate through a control valve which is normally closed but which opens automatically to admit steam to the storage plant when the rate of flow of steam to the site main exceeds said flow rate. In the form shown a waste heat boiler receives heat from a steel converter plant, the boiler comprising a steam drum 1, an evaporator 3, a circulating pump 5, and an economizer 2. Saturated steam is passed from the steam drum 1 through a line 6 to a superheater 7 whence it passes to the site main through a steam main 8. An attemperator 9 under control of a valve 10 ensures that the superheated steam is maintained at a constant temperature. When the amount of steam generated exceeds a predetermined flow rate, as may occur at peak heat imput conditions during the blowing of the converter, a normally closed control valve 13 automatically opens to admit the excess steam to an accumulator 12 which acts as a thermal storage device. The accumulator 12 is preferably designed to accommodate all the excess steam generated during the peak period. However, should the excess steam exceed the capacity of the accumulator a shut-off valve 14 is arranged so that it closes when the pressure in the accumulator reaches a valve corresponding to the pressure on which the design was based. As the valve 14 closes a further valve 16 in a blow-down line 15 is arranged to open to divert the remaining excess steam to atmosphere and maintain the flow rate to the site main at a constant value. The excess steam stored in the accumulator 12 is discharged from the same through a control valve 25 in a discharge line 17 leading to a feedwater heater 18, the valve being controlled by a temperature controller set to discharge the accumulator over a given period to suit the time between flow periods of the converter. The steam entering the feed heater 18 heats the feed water for the boiler and is condensed, the water so formed being led via a line 19 to a feed tank 20. Feed water is fed to a steam drum from the feed tank 20 via a feed pump 24, the feed heater 18 and line 22. Auxiliary firing may be used to heat the boiler if the period between the blow periods is longer than the accumulator can accommodate.