Studies On Two-stage Coal Gasification Technology With Calcium Salt

With the problems of slow reaction rate and low production capacities in the two-stage coal gasification process, coal pyrolysis and gasification processes in the secondary stage gasifier could be affected by loading calcium salt to accelerate the reaction rate. It was studied that effects of calcium salt and ashes on the processes of coal pyrolysis and gasification in the fixed-bed experimental system. For the coal pyrolysis process, experimental results showed that calcium salt makes an evident change of peak value of gas release rates, the temperature corresponding the peak value of gas release rates, and cumulative gas release quantity. In the whole range of pyrolysis temperature, calcium slat could enhance effectively cumulative release quantity of CO and CO2 of Inner Mongolia lignite pyrolysis, and hinder the release of the larger aromatic ring systems during pyrolysis to reduce the cumulative release quantity of H2. With the increase of calcium slat quantities on Inner Mongolia lignite, the influence of Ca additives on gas release rates in pyrolysis behavior was increasing.For coke gasification process, the influence of calcium salt on coke gasification reactivity became diminishingly with the increase of gasification temperature. Apparent activation energy of Inner Mongolia lignite coke and the coke loading calcium salt are 81.53kJ.mol-1 and 71.5kJ.mol-1. Apparent activation energy of the raw cokes decreases about 12% with the addition of calcium salt. The mineral substances in Inner Mongolia lignite make the largest contribution on the process of coke gasification, with the value of number 49.8%. The contribution number of calcium salt for the gasification reaction is 11.3%, which is lower than the effects of minerals in the coal.It was also studied that the effects of coke particle sizes on combined two stage coal gasification technology and the primary experiments in the new constructed gasifier. It showed that the optimal size range is 10～15 mm size. Under this size distribution, carbon dioxide cumulative conversion is 10% in the 2h reaction time and reaction rate reaches the peak value after 30 min. Due to heat loss becoming evidently in the experimental process, the effects of heat loss and O/C in the first stage gasifier on the two stage coal gasification technology were studied with the Aspen Plus simulation software.