| 摘要 |
Multi-stage gas cleaning process to remove unwanted gases, vapours, mists and dust from gas streams for cleanup of roaster off-gases in pyrometallurgy, where sulphur dioxide-contg. roaster gas is used to produce sulphuric acid. The system consists of two stages of (co-current) gas scrubbing with a recirculating scrubber liquor, followed by at least one stage of electrostatic pptn. in a special system employing irrigated cylindrical collecting electrodes. - The gas cleaning system consists of an initial co-current scrubbing tower (1) with a top inlet (3) and bottom outlet (5) for gas. The gas is initially scrubbed with a scrubber liquor (e.g. 5-10% sulphuric acid at 40 deg.C) using spray nozzles (9) at the top of the tower while contaminated liquor collects in the tower bottom (6), passes to a settling tank (15) and is recirculated via pump (13) and cooler (11). The initial gas feed temp. is typically 250 deg.C and it may contain say 7% SO2, 2g/cu.m dust and 1 g/cu.m arsenic and selenium vapours. The gas velocity in the primary scrubber tower is 30-40 m/sec. and the gas is cooled to its adiabatic saturation temp.. The second-stage scrubber (2) is a venturi scrubber in which the gas velocity is 50-70 m/sec. and the gas is cooled to 40-50 deg.C by scrubbing with liquor via nozzle (19) near venturi throat (17). Gas leaves at (24) and liquor collects at (22) for recirculation via settler (15). The gas is then cleaned in one or more electrostatic precipitators (25,26) before leaving at (31) to the sulphuric acid conversion and absorption sections of the plant. |
