Hayami Ito

Study on a CWM preparation system.

In order to develop a preparation system of a highly loaded coal water mixture (CWM) a bench scale test, a pilot scale test and a demonstration test were conducted, where a high concentration wet grinding method was employed.CWM prepared by the high concentration wet grinding method contains desirable quantity of fine particles which are needed for ensuring lower viscosity at high concentrations and also for good statical stability. One of the major subjects of this grinding method is how to decrease coarse particles over 150μm because the coarse particles tend to become unburned carbon when CWM is burned.In the grinding tests, it was found that the increases of the length/diameter ratio (L/D) and the number of compartments of mill were both effective to decrease coarse particles. A two-stage grinding method was also effective. Based on these findings, an 1-stage feed and 2-stage grinding system using multi-chambered long tube mills was developed.In the demonstration test with a capacity of 26t/h, a CWM prepared by this system was found to contain a very little amounts of coarse particle with good rheological properties. The statical stability and the combustibility were also found satisfactory.