| 摘要 |
<p>PURPOSE: To produce a fibrous plaster board by a new combination of wet molding and dry recrystallization by preparing a suspension from a beaten fiber material and calcium sulfate dihydrate and dehydrating the same to mold a board and heating the board to recrystallize the same to a hemihydrate which is subsequently converted back into the dihydrate. CONSTITUTION: A suspension consisting of raw material plaster and wet-adjusted fiber is mechanically dehydrated by using an endless filter 13 so that hot distillation moisture becomes about 30-40% to be molded into a board. At this time, a dihydrate is recrystallized into aβ-form of a hemihydrate in air and moisture necessary for coagulation is absorbed through the board. The raw material board is dried and calcined in a continuous heating furnace 15 at a board temp. of 100-170 deg.C, pref., 115-140 deg.C. Next, moisture necessary for coagulation is absorbed into a board core part by an absorbing apparatus 17. It is advantageous to set moisture excessiveness to at least 2.5 times a stoichiometric moisture demand. A press 19 is connected after absorption. By this constitution, penetration is equalized and the board is compressed to perform additional dehydration and calibration.</p> |
