Research On Pressurized Drop Tube Furnace And Its Experiment

The drop tube furnace (DTF) is one of the important experiment devices used in coal reaction process research, and the development of pressurized drop tube furnace (PDTF) used for coal dynamics research at high temperature, high pressure, and high heating rate conditions is the trend of DTF. In this paper, on the basis of analysis of the DTF home and abroad, the PDTF had been investigated and established, and then thermal reaction characteristics of typical coal under independent operation parameter were investigated with PDTF.The main research contents and results are summarized as follows:(1) Two microfeeders working in atmospheric and pressurized conditions were established individually. The microfeeder adopted shaftless screw mode and showed good stability with precision is±7.2%when feeding rate is0.4-1.0g/min at pressurized conditions. The feeding rate of microfeeder depends on the speed of agitating screw and conveying screw, and is independent of flow rate of carrier gas, stack height of paticles and operating pressure.(2) The pressurized drop tube furnace was investigated and established. The pressure keeps balance between inside and outside the reaction tube by pipe design of corundum fixed components on the furnace top. The feasibility and reliability of fiber lining under pressurized conditions were proved by porosity and compressive strength tests. Horizontal staggered arrangement and multiple zone tempreture control of SiC heaters improved temperature uniformity of the reaction zone. Designed ePTFE components seal SiC heaters under pressurized conditions. A series of length-adjustable injection probes realize economically and conveniently continuous sampling under pressurized conditions. The structure design of pressurized preheater has characteristics of both PDTF and packed beds. In addition, the specific design parameters of SiC heaters, injection probe, collection probe and preheater were calculated. (3) The Integration and commissioning of PDTF system were performed. The feeding rate operation criterion of controlled particle reaction behavior was proposed. According to actual temperature distribution of reaction zone, the control accuracy was obtained. Moreover, temperature and heating rate of particles under different conditions was calculated. Data monitoring system was developed and experiment error was analyzed.(4) The pyrolysis and gasification experiment of typical coals with high heating rate were studied. Ash tracer method has been developed in pyrolysis experiment, and the reaction conditions of pulverized coal was controlled and adjusted individually with temperature (heating rate) and residence time. Nitrogen tracer method and chromatographic analysis has been developed in gasification experiment, and the reaction conditions of pulverized coal was controlled and adjusted individually with temperature (heating rate), residence time, O2/Coal and pressure. The results of experiment showed conversion of typical coals changed with individual operation parameters and were accord with reaction basic rules and existing experimental results of DTF and verified reliability of PDFT established in this paper.