METHOD FOR CONTROLLING CALCIUM HARDNESS

摘要

PURPOSE: A method for controlling calcium hardness in paper manufacturing process is provided, which is characterized in that sodium carbonate or calcium hydro carbonate is added to white water to settle calcium ion. CONSTITUTION: Silo white water which is shortly circulated is purified by settling calcium ions, and the calcium carbonate ions are absorbed. Carbonate ion and sulfate ion react with calcium ion and produce precipitate. Sodium ion which replaces calcium ion does not react with other ions and does not produce scales in the water. The precipitates can be removed by using a sedimentation chest, but because the sedimentation chest requires an extra device for neutralizing, a floating method is appropriate. Carbon dioxide which replaces air can remove calcium carbonate and control the concentration of hydrogen ions.