GB858928A - Method of and apparatus for discharging liquid working medium out of the separator of a forced through-flow steam generator - Google Patents

Abstract

858,928. Regulating forced-flow steam boilers. SULZER FRERES S.A. May 11, 1959 [May 22, 1958], No. 16095/59. Classes 123(2) and 123(3) In a method of regulating a forced-flow once-through steam generator, which method remains flexible in spite of the approach of the live steam pressure toward the critical pressure, water, collected in a separator 16 located between a vaporizing section 14 and a superheating section 18, is discharged through an outflow line 19 equipped with a valve 21 which is regulated in accordance with the quantity of liquid present in the separator and is also fed through a line 23 to an injection point 25 in the superheater 18, the amount of injection being controlled by a valve 24 which is incorporated in the line 23 and is controlled by a thermostat 39 heated at the steam-discharge end of the superheater. The discharge valve 21 is controlled by a float 35 acting through a lever 36, a bellcrank lever 37, and a link 38. If desired the thermostat 39 may be located at another point in the superheater such as at the injection point 25 or at a point 42. Steam from the superheater is delivered through a line 26 to a turbine plant 27 which exhausts through a Ine 28 to a condenser 31 from which condensate is urged by a pump 33 through a line 34 to a water vessel 10. A pump 11 feeds water to an economizer 13 connected to the vaporizer 14. In operation, if e.g. the intensity of firing is suddenly increased as a result of a change in load so that the quantity of water separated out in the separator 16 is considerably reduced, the float 35 drops to close the valve 21 accordingly. Fig. 2 shows two-stage injection where additional injection water is branched-off in a line 43 having a valve 44 controlled by a thermastat 46, and in order to meet the greater injection-water requirements an auxiliary supply line 47 is led from the feed line 12. The line 47, containing a valve 48 which is connected to the bellcrank lever 37 by a lever 49 and a link 51 to operate in the opposite sense to the valve 21 so that when the latter is closed the valve 48 opens, joins the line 23 a non-return valve 52 being inserted between the union and the separator 16 to prevent discharge from the line 47 into the separator 16. A valve 53 in the line 47 reduces the pressure in that line to a value slightly above that prevailing in the line 23 thus ensuring, on change over to injection supply from the line 47, that a large pressure rise does not suddenly occur at the injection points while still maintaining sufficient pressure difference to close the non- return valve 52. The valve 53 may be located upstream of the valve 48. Alternative means of reducing an abrupt pressure rise on change over includes a second regulating valve which is disposed in the line 47 downstream of the valve 48 and which is operated by a servomotor which is influenced by the difference in signals received from two pressure sensing devices located respectievly in the line 23 upstream of the non-return valve 52 and downstream of the junction between the lines 23, 47. In a modification, Fig. 5, the valve 48 is by-passed by a line 59 incorporating a valve 61 adjusted in dependence on signals from an instrument 62 which measures the salts concentration of the feedwater in the line 12. If the salt concentration becomes too high then, independent of the float regulation, the injection of water from the separator is discontinued and injection from the feed line 12 is substituted. The instrument 62 could be arranged at another location, e.g. at the separator 16, and the non-return valve 52 could be replaced by valve which is influenced by a salts concentration measuring instrument and is closed on the opening of one of the valves 48, 61. A second vaporizing section may be provided between the separator 16 and the superheater 18 which may be followed by a second separator the outflow of liquid medium to the superheater being from either separator of from both.