Abstract: A method for rapidly changing the amount of pulverized coal supplied to a coal-fired furnace (10) equipped with a coal pulverizer (20) from a first steady-state level to a second steady-state level in response to a change in operating load demand. The amount of pulverized coal supplied to the furnace is instantaneously increased by providing pulverized coal to the furnace from a source (42) independent of the pulverizer or instantaneously decreased by diverting away from the furnace a portion of the pulverized coal being supplied by the pulverizer.

Abstract: A once through steam generator (10) for sliding pressure operation from supercritical pressure at high loads into the subcritical range at low loads, having vertical tubes (14) lining the furnace (12) walls and passing their entire length without a mixing header. The furnace tubes are internally rifled and have orifices (47) associated with them to proportion the flow at full load. A steam separator (26) receiving effluent from the tubes sends steam to the superheater (70) and at low ratings returns water (32,40) to the tubes for recirculation therethrough. The tubes (14) are sized in accordance with a specified criteria based on the mass flow rate at full load, or on the ratio of friction drop to static head.