| 摘要 |
1,227,092. Sulphur trioxide; sulphuric acid. RALPH M. PARSONS CO. 20 March, 1969 [21 March, 1968], No. 14667/69. Heading C1A. In the production of sulphur trioxide wherein the SO2 content of a gas stream is converted to S0 3 in a series of catalytic steps with an intermediate sulphur trioxide extraction step, the feed stream 14 to the converter 18 which is at a temperature higher than that required by the first catalytic step is cooled to the required catalytic conversion temperature by indirect heat exchange with the cool gas stream 22 returning to the converter from the intermediate S0 3 extraction step in absorber 20, and this return stream also serves to cool by indirect heat exchange the product stream 28 passing to a catalytic conversion step subsequent to the first but before the intermediate absorption step, but is not used to cool the product stream emanating from the catalytic step immediately before the absorption step, the said return stream thereby being heated to a suitable temperature for catalytic conversion in a further step. A plurality of catalytic conversion steps may be accomplished between the said first step and prior to the intermediate SO 3 extraction step and the product stream passing to each catalytic conversion step subsequent to the first and prior to the intermediate extraction step is cooled by indirect heat exchange with the return gas stream. Sulphuric acid may be produced by absorbing the SO 3 produced in an aqueous liquor. The SO 3 may be absorbed in sulphuric acid, and the S0 2 absorbed with the SO 3 in this acid may be stripped from it, e.g. using air in tower 60, and recycled via line 16 back to the converter inlet stream. The reaction product from the last catalytic conversion step before the intermediate extraction stage may be cooled by indirect heat exchange, e.g. with water in heat exchanger 39, to a temperature required by the extraction step. As shown in Fig. 1 the return gas stream may be split into two streams 24 and 32 one serving to cool the converter inlet stream 14 and the other cooling the reaction product stream 28. In alternative embodiments (Figs. 2 and 3, not shown) the return gas stream may cool these two gas streams successively either one of them being taken first. The reaction product stream emanating from the final catalytic stage is extracted in a final absorber 48 before the residual gas is passed to the stack. |
