Study On Reactivity Of Semi-coke From Low Rank Coal

Semi-coke is the main product of pyrolysis process of low rank coal. It is urgently need to research for efficient and clean utilization of semi-coke, opening up the new utilization way of semi-coke, solving the problem of efficient and clean utilization of low rank coal.An integrated experimental apparatus for low rank coal（Inner Mongolia lignite and Shaanxi coal） pyrolysis was implemented to simulate the pyrolysis process of coal in externally heated upright carbide furnace. It was researched influence of pyrolysis conditions to yield and properties of low rank coal pyrolysis semi-coke. The results demonstrate that: As the pyrolysis temperature and time increases, the yield of semi-coke gradually reduces, volatile content of semi-coke gradually reduces, ash and fixed carbon content increases; Carbon content in the semi-coke gradually increases, hydrogen and oxygen content reduces. With the increases of pyrolysis temperature, calorific value of Inner Mongolia semi-coke first increases then decreases; As the extension of pyrolysis time, calorific value of semi-coke increases gradually. With the increased of pyrolysis temperature, vibration intensity of hydroxyl absorption peak, C-H stretching vibration band and aromatic ring C=C stretch vibration absorption spectra gradually weakened or disappeared, which illustrated that the higher of pyrolysis temperature, the higher degree of coalification of semi-coke.Using temperature programmed thermogravimetric experiment method to study the combustion characteristic of low rank coal semi-coke. The relationships between pyrolysis conditions, quality parameters of semi-coke and combustion performance of semi-coke were studied. The mechanism of combustion performance difference between different semi-cokes was revealed. The results demonstrate that: The combustion performance of semi-coke deteriorates with the increase of temperature and time during the pyrolysis process. Fuel ratio of semi-coke and its combustion performance shows a good regularity. For the same coal, the fuel ratio of semi-coke can predict its combustion performance. BET surface area and micro surface features of semi-coke are the main reasons affecting combustion performance.Using temperature programmed thermogravimetric experiment method to study the reactivity of low rank coal semi-coke in CO₂.The relationships between pyrolysis conditions, quality parameters of semi-coke and reactivity of semi-coke in CO₂ were studied. The mechanism of reactivity difference in CO₂ between semi-coke and coal was revealed. The results demonstrate that: The reactivity of semi-coke in CO₂ deteriorates with the increase of temperature and time during the pyrolysis process. Volatile content of semi-coke and its gasification reactivity presents a good regularity. Gasification reactivity of semi-coke is better than coal with the same quality parameters. Gasification reactivity of Inner Mongolia semi-coke is superior than Shaanxi semi-coke with the same quality parameters and pyrolysis conditions.The combustion performance of the mixture of coal and semi-coke was studied. The results show that: With the proportion of coal increasing in mixture, combustion performance of mixture gradually gets better. The combustion performance of mixture and coal with the same volatile content is similar, so mixture can burn instead of coal.