Development Of A Coal Char Isothermal And Differential In-situ Reaction Experimental Apparatus

The study of coal thermochemical conversion rules extensively involves thekinetics of gas-solid reaction. The micro-fluidized-bed reaction analyzer(MFBRA)developed by IPE, CAS enhances heat and mass transfer of gas and solid byfluidization, achieves isothermal and differential reaction by instantaneously feedingminute samples into the micro-fluidized-bed, measures the concentration change ofgas composition online, calculates kinetic parameters by isothermal and differentialkinetic equation, and proposes the reaction mechanism. It can be expected thatMFBRA has good functional upgradings and applications in pulverized coal reactionresearch.Gasification or combustion of coal includes multi-staged reactions, such as hightemperature fast pyrolysis, residual char burning out or gasification. A coal charisothermal and differential in-situ reaction experimental apparatus developed by thisdissertation strengthens the management of reaction temperature and atmosphere inmicro-fluidized-bed, for which the functions of MFBRA is developed based oncharacteristics of coal thermochemical conversion. In the equipment, pulverizedcoal pyrolysis happens at a specified temperature and the residual char turns togasification or combustion immediately, which avoids loss of char reactivity causedby moving or leaving unused chars.For the design of gas preheating pipe, engineering calculation, thermocouplemeasuring and FLUENT simulation are carried out to study the heat transfer inpreheating pipes. The results show that the heating furnace has a excellenttemperature uniformity. The required pipe lengths for the same flow of one gas bepreheated to an identical temperature are unrelated to pipe diameters. It is notappropriate that bare thermocouples are used to measure gasflow temperature whena sizable temperature difference exists between the wall and gasflow, whichprobably leads to large deviation. Spiral preheating pipe can achieve high efficiencypreheating in a wider flow range and a smaller heatspace and the atmosphere switchdelay time can be easily limited to less than1s.Peclet Number have an inverse relationship with the pipe diameter. The airflowis more close to plug flow when decreasing the pipe diameter, which can restraineffectively the backmixing in preheat pipe. The designed spiral preheating pipereacter has fully reached the dynamometer indexs of fully pre-heat, backmixingrestraining and the atmosphere switching delay time.Pulse feeding is experimentally confirmed applicable to the instantaneousfeeding of pulverized coal. Under the feed pressure of0.2MPa and pulse width of12ms, a pulse jet volume is6.6mL and pulse jet ratio is97.4%. To explore the required operating conditions when testing pulverized coal reactions, GASMETFT-IR is connected to the equipment to test the pyrolysis and combustiojn ofpulverized ZHUNDONG coal. A larger of the gas flow (e.g.1.4NL/min), highoxygen concentrations(e.g.50%) gas and fewer reactants(e.g.10mg) are required torestrain the lack of oxygen during the initial char combustion.The severe airflow backmixing of GASMET FTIR passageway decides itsunsuitability for the detection of concentration changes during pulverized coal fastreaction.