Clinker burning in the fluidized bed - an innovative technology

A number of international cement plant manufacturing companies looked into the subject of clinker burning in fluidized beds a few decades ago. Bunting clinker in a fluidized bed has a great many advantages. While retaining th e cyclone preheater and calciner it replaces both the rotary kiln and the c linker cooler by an arrangement of static reaction vessels, which reduces t he capital and maintenance costs. The fluidized bed with its ideal heat tra nsfer properties permits the use of low grade fuels, contributes to a signi ficant lowering of the NOx emissions because the temperature level is lower than in the rotary kiln process, and also leads to a certain reduction in the specific heat consumption as a result of lower wall losses. On the othe r hand, more electrical power is needed to overcome the higher pressure dro ps. However one crucial precondition for industrial implementation of clink er production in a fluidized bed is stable raw meal granulation in the kiln system. After working on the problem for a decade the Japanese cement plan t manufacturer Kawasaki Heavy Industries Ltd., has succeeded in getting the raw meal granulation process to start automatically at a temperature level of 1300 degrees C without making use of so-called granulation nuclei intro duced from outside. An extensive report is given, of the conditions of the granulation process and the mechanism of the granulation itself. The basic research into clinker burning in a fluidized bed at Kawasaki was started in 1984; this led to small test plant with a throughput of 2 t/d, then in the next research stage to a pilot plant with a throughput of 20 t/d, and in 1 995 to the construction of a 200 t/d plant, which was operated until the en d of 1997. The development work was partially subsidized, and the various s tages ran in, close cooperation with Japanese cement manufacturers, the Cen tre for Coal Utilization and the Japanese Cement Association. As the temper ature in a fluidized bed can be controlled very accurately the fluidized be d process is virtually ideal for producing different grades of cement clink er.