GB1495831A - Coal gasification process with procedure for continuously discharging ash particles and apparatus therefor - Google Patents

Abstract

1495831 Removing ash from gasifiers KAMYR Inc 12 Feb 1975 [15 Feb 1974] 5958/75 Heading F4B A process for separating ash from pressurized synthetic gasifiers includes the steps of (i) confining the liquid within a first path 16 wherein the liquid is at a high pressure, by having a surface 12 communicating with the gas pressure at the ash particle discharge end of the gasifier 14, (ii) discharging ash particles into the high pressure liquid through the surface 12, (iii) maintaining a continuous flow of the liquid along a second path 18, at a pressure lower than that of the liquid in the first path, and (iv) continuously moving batches of liquid and entrained ash particles from the first path and adding the batches to a second path. The only liquid specified is water. Preferably the batchwise transfer of ash particles and water is performed using a cylindrical sluicing device 26 which includes a rotating wheel containing four diametric channels 74 arranged in two crossing pairs, each pair offset by 45 degrees from the other. Each channel may be rotated to communicate with an inlet 78 of a liner 76, the inlet being in permanent communication, through a hole in a housing 60, with the first, high pressure path 16, thereby filling the channel with ash and water. On rotation through 90 degrees (dashed lines in Fig. 1) the channel then communicates with the inlet 80 from the low pressure path 18 and water flow caused by pump 20 caused discharge of ash and water through sluicing device outlet 84 and then pipe 34. A temperature responsive valve 52 allows cold water to flow into the gasifier to prevent boiling of water in the gasifier and a throttle valve 56 bleeds water and ash from the high pressure path through channel 74 in response to increase in the level of the surface 12 to compensate for cold water input. A sieve 92 in an outlet 82 of the liner 76 allows flow to the throttle valve 56 but retains larger ash particles in the channel 74. Ash and water from valve 54 and pipe 34 fall on to a continuous foraminous belt 30 which retains ash and allows water to pass to a recycling tank 32 which supplies the pump 20 and a pump 38 which pumps water into the gasifier. In a further similar embodiment (Fig. 4, not shown), the gasifier incorporates a device to crush the ash (above or below the surface 12 of the water). Discharge through the sluice channel from the high pressure is recycled to the gasifier. Temperature is controlled by venting high pressure water, sieved free of ash, from the high pressure recycling line to the low pressure path in response to temperature; the level of the surface 12 is then maintained by cold water supplied in response to a fall in the level of the surface 12. In a final embodiment (Fig. 5, not shown) the high pressure outlet of the sluicing device is blocked by replacing the sieve 92 with a solid plate whereupon the channels of the sluicing device fill by gravity and leakage from the sluicing device. To control temperature, high pressure water is bled from the gasifier in response to the temperature of the water in the gasifier into the low pressure path, and cold water is supplied to the gasifier in response to lowering of the level of the surface 12. As a safety feature the raising of the level of the surface 12 is controlled by a further direct bleed from the high pressure gasifier water, which bleed is fed into the low pressure path when the level of the surface 12 exceeds a predetermined level.