| 摘要 |
<p>PROBLEM TO BE SOLVED: To maintain the reactivity of limestone at a high level and greatly reduce cost by allowing a specified amount of ammonium ions to be present in an absorbing solution when oxidizing and neutralizing sulfurous acid contained in the absorbing solution by bringing the absorbing solution which has brought into contact with a flue gas, into contact with a coarsely crushed limestone. SOLUTION: After being supplied to a spray pipe 12 in an absorption tower 10 and brought into contact with an untreated flue gas A containing sulfurous acid gas, the absorbing solution is sent to the bottom part of a limestone pit 20 through piping 22. In the process in which the absorbing solution ascends the limestone pit 20, passing through a fixed bed 21, the absorbing solution comes into contact with a coarsely crushed limestone E in the fixed bed 21, and the limestone dissolved in the absorbing solution chemically reacts with sulfuric acid to produce gypsum. The absorption tower 10 is of such a construction that ammonia gas, aqueous ammonia or an ammonium salt can be supplied as required, into the untreated flue gas A to be introduced into the absorption tower 10 or the absorbing solution circulating through the device. The ammonium ion of the absorbing solution should be 10 mmol/liter or more.</p> |
