GB909537A - A drumless, forced-flow, once-through steam generator with accumulator property - Google Patents

Abstract

909,537. Forced-flow steam boilers. LICENTIA PATENT-VERWALTUNGS-G.m.b.H. July 13, 1959 [July 11, 1958], No. 23982/59. Class 123 (2). In a forced-flow, once-through steam boiler comprising a preheating section 1, an evaporating section 2, a transition zone 3 and superheater 4, the tubes of the sections 2, 3 are made of larger diameter and greater wall thickness than the tubes of the superheater so that on a sudden fluctuation of steam demand the steam temperature at the outlet of the superheater will be maintained substantially constant as the increased volume of steel in the thickened tubes takes up or delivers heat to the working medium while the normal boiler controls adjust the firing rate &c., to the new load. In the lower half of the Figure the upper curve represents the working medium temperature through the boiler under steady conditions when, for example, steam is being delivered at 150 atmospheres pressure. The lower curve shows the temperature conditions on a sudden increase in load. The increase temporarily lowers the boiler pressure to, say, 120 atmospheres, causing a fall in the evaporator outlet temperature. Heat is transferred from the thick walls of the sections 2, 3 to the working medium so that its temperature at the outlet from the transition zone is almost that obtaining at the higher pressure. A smaller amount of heat transferred from the walls of the superheater tubing restores the outlet temperature to its previous level, thus bridging the delay in the operation of the firing &c. controls.