White Mud's Comprehensive Utilization

At present, the development of our country's paper industry is rapid and paper making raw material is primarily non-lumber (grass class) fiber. The processing of alkaline process papermaking black liquor is still primarily by alkali recycling , and its waste liquid treatment causes to produce massive waste white mud which pollutes the environment. This has become one of attentive points of environmental protection worker's work.In this article the main components of causticizing white mud which comes from the alkaline process production of straw pulp are analyzed. According to the feature that the main component of white mud is CaCO₃, white mud's two applications to calcium carbonate refinement and flue gas desulphurization are given discussion and investigation. We find the best method to use white mud to refine calcium carbonate through experiments, and prove the feasibility that white mud can be used as desulfurizer, providing the basis for engineering use and playing certain guiding effect on practical production.Refining methods of straw pulp white mud have been studied, and three simple and convenient methods of refining white mud for CaCO₃ used as papermaking have been found. There are washing process, drying process and additive process. The conclusion are as follows:The brightness of CaCO₃ refined by washing process is 84.5-85.3%(ISO).Water consumption with the process in the lab is about 20-40 ton for one tons white mud. The process operation affects the water consumption.The brightness of CaCO₃ refined by drying process is 88.2%(ISO).The lowest water consumption with the process in the lab is about 5-10 tons for one ton's white mud.The brightness of CaCO₃ refined by additive process is 87.4%(ISO). Total water consumption with the process in the lab is about 10-30 tons for one ton's white mud.The content of silicon in products of CaCO₃ refined by above three methods is basically stable, and the content of residual alkali in products of CaCO₃ refined accords with papermaking requirements. Products of CaCO₃ refined by drying process have the best brightness and the least water consumption. It is considered by summary of the relevant dates: equipment, process and cost of production, the drying process is optimum to refine white mud for papermaking filler above three refining methodsAccording to Paper Mill using CaCO₃ refined from white mud as paper filler, the products of CaCO₃ can be completely used as paper filler in theory.At the same time, we also studied the applications of desulfurization with straw pulp white mud. The feasibility of white mud used as desulfurizer has been verified by experiment. We also compared white mud with limestone in desulfurization, under the same condition, if white mud and limestone have the similar CaCO₃ content, the same weight of white mud has better desulphurizing effect.The feasibility of white mud used as refining CaCO₃ and desulfurizer has been verified by experiment, and provides a practical base for papermaking white mud recycling, to attain the purpose of waste treated by waste.