| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method for producing plaster with waste acid extraneously generated from exhaust gas from copper refining as a material, in which productivity of plaster product is improved by suppressing reduction in capacity of a reaction chamber in which neutralization agent is supplied.SOLUTION: There is provided a producing method of plaster, in which mixture of waste acid 4 generated in a sulfuric acid producing step S2 supplied with calcium compound is converted into plaster particles during circulation in a plurality of reaction chambers 1, 2, 3 to n and a part of the plaster particles obtained the most downstream reaction chamber n is re-introduced into the most upstream reaction chamber 1 as a seed crystal. A reaction chamber which is one reaction chamber selected from the plurality of reaction chambers 1, 2, 3 to n in which calcium compound is charged is changed to another upstream reaction chamber when a predetermined operation time is elapsed.</p> |
