The injection system of solid materials flowable for example for blast furnaces

摘要

981,826. Pneumatic conveyers. PULLMAN Inc. May 31, 1963 [June 15, 1962], No. 21867/63. Heading B8A. In a method of supplying particular solid material such as powdered coal to a furnace 184, Fig. 4, under elevated pressure conditions, the flow is divided into separate and independently controlled conduits 164 (one only shown) leading to separate lances 176 and in which the flow is maintained at a predetermined rate irrespective of pressure fluctuations in the furnace. The powdered coal delivered from a bowl mill, drying plant, cyclone separator (Fig. 2, not shown) operating at sub-atmospheric pressure is transferred in batches through an air lock system (Fig. 2, not shown) to a pressurized surge tank (Fig. 3, not shown) from which the coal is pneumatically conveyed through parallel conduits 150 (only one shown) to four distributer hoppers 152. Each of the hoppers 152 has four withdrawal conduits 164 to which air is controllably supplied from one of sixteen manifolds 340 through a series of parallel restriction orifices 342-352. The flow of powdered coal to the furnace is maintained substantially constant over a wide range of pressure conditions in the tuyeres 178 by means of a differential pressure controller 382 which maintains a constant pressure differential between the bustle pipe 182 and each distributer hopper 152 by controlling a valve (not shown) in a fines recovery line 160 from the hoppers 152. This thereby maintains pressure drop of about 3 to 6 p.s.i. across the control valve 168 in the withdrawal conduits 164. Substantially constant gas velocities are automatically maintained throughout the system irrespective of pressure changes in the distributer hopper 152. For this purpose an absolute pressure recorder 384 in the hopper system is adapted to control the supply of conveying air to various parts of the system, through pressure compensated flow controllers. These comprise ratio meters 386, 390 and 388 (Fig. 3, not shown) which through recording controllers and control valves maintain desired constant velocity flow of air to the supply conduit 150, manifold 340 and conduit 172 for injecting conveying air into the lances 176. Further pressure control means are provided for maintaining constant pressure drops through the powdered coal supply system leading to the supply conduit 150 so that a steady flow of solids is maintained independently of variations of pressure in the surge vessel 152. Automatic level controllers are provided on the various hoppers 152 &c. whereby flow is adjusted to maintain a constant level of material either by adjustable valves or by stopping and starting the pulverizing plant (Fig. 2, not shown) supplying the system. Temperature recorders are also provided and may operate alarm systems. Provision for injection of carbon dioxide into overheated regions may also be made.