The full scale ceramic tube filter (CTF) for hot gas cleaning installed in the 71MWe PFBC combined cycle power plant was successfully demonstrated to establish extremely low emission and stable pressure drop.The pressure drop across both the filter element and the ash accumulated on its surface was analyzed and predicted based on the actual PFBC plant operation data. The equivalent electric circuit model for the flue gas system of the actual PFBC including CTF was built in the simulation program where the characteristic equations were set up to describe the pressure drop across filters. Then the dynamic simulator was constructed and tuned in order to follow the actual plant behaviors. The reverse cleaning is a very important control factor for the stable operation of CTF. There are four parameters to determine the reverse cleaning conditions: fast pulse cleaning valve open time, pulse cleaning pressure, pulse cleaning interval and pulse cleaning mode. The former two parameters were fixed, while the latter two were controllable. The optimum condition to satisfy both the lowest maximum pressure drop across CTF and the smallest range of pressure drop variation was explored using the developed simulator. In our case, the three compartments for each CTF vessel were equipped. Then the mode of uniform cleaning against the compartments was suggested as the optimum cleaning one. Such an optimization can be performed exclusively by the simulator, because of too much complexity due to the interaction among the compartments in the actual plant operation. The possible improvement for the characteristic equations and its corresponding equivalent circuit model were discussed, to allow its application for the commercial plant design.
A preliminary study on supercritical methanol extraction of a brown coal, Loy Yang, was conducted. The experiments were done at 400°C with varying the extraction time or the coal/solvent ratio. When the extraction time was extended from 60min to 300min, the extraction yield remained constant but the liquid yield was reduced from 70% to 60%. This suggested that the extract further decomposed into gaseous components during the extended extraction. The increase in the coal/solvent ratio led to the decreases in the extraction and liquid yields, and the decrease in the liquid yield was more remarkable than that in the extraction yield . The pressure in the autoclave increased with the increasing coal/solvent ratio. These observations indicated that the increase in the coal/solvent ratio led to pyrolysis of coal as a dominant chemical process rather than the degrading reaction of coal polymer by the action of supercritical methanol as a reagent. A GC-MS study on a liquid extract revealed that the major chemicals were methyl-substituted phenols and a phenol-methyl ether.