| 摘要 |
A multi-stage apparatus suited for concentrating sulphuric acid comprising at least one high temperature stage and one low temperature stage, the high temperature stage including a surrounding wall defining a flue gas channel, means for delivering hot flue gas to said channel, and means for withdrawing from said channel cooled flue gas, the flue gas heating said surrounding wall which in turn imparts heat to material to be heated thereby, the low temperature stage including a heat exchanger with a first flow path for a heating agent and a second flow path for a material to be heated thereby, means for supplying the said second flow path material to be heated, means for withdrawing from said second flow path material after having been heated therein, and means for withdrawing from said first flow path spent heating agent, the means for withdrawing cooled flue gas from said flue channel of said high temperature stage forwarding heat from said cooled flue gas to said first flow path of said low temperature stage to serve as the heating agent in said low temperature stage. Advantageously the high temperature stage involves transfer of radiant energy from a surface heated by hot flue gas to a falling film of sulphuric acid flowing down a quartz tube separated from the radiating surface by an air space. An intermediate heating stage may be provided in which the cooled flue gas heats an exchanger liquid which is the heating medium in the low temperature stage. |
