Preparation and Performance Study on Lignite Briquette Coke
In order to promote the energy utilization efficiency and reduce the environmental pollution in the process of lignite direct utilization, lignite briquette and its coke were prepared. The effects of pyrolysis temperature and holding time on the briquette coke were investigated through the pyrolysis experiments of lignite briquette. The results showed that the changes of yield, volatile, ash, fixed carbon, elemental composition and oxygen functional groups content of briquette coke were dependent on increasing pyrolysis temperature and holding time. The mechanical properties of the briquette coke were assessed by means of their cold strength, compressive strength, thermal strength, immersion strength, falling strength, and so on. The fine quality briquette coke prepared from lignite briquette with high strength, heat stability more than 96%, low calorific value on dry basis higher than 6600Cal/g, and its volatile content could reach no more than 3%.
Forming and Releasing of Gaseous Products of Coal During Pyrolysis in Western China
Three coals from Shendong,Lingwu and Hami mine in Western China and one coal from Pingshuo mine in Central China were selected to research the effects of the structural characteristics and reducibility of coals on the gaseous products during pyrolysis.The pyrolysis experiments were completed in a fixed bed reactor at 200-1 000 ℃.The results show that the change trends of gaseous products CO,CO2,H2,CH4 and C2 hydrocarbon are similar with increasing temperature for all coal samples.The yield and maximum releasing temperature are obviously different for different kinds of coal sample.The releasing amount of containing-H and containing-O gaseous products is consistent with the element content of H and O in coal.Compared with Pingshuo coal,the pyrolysis characteristics of three coals with weaker reducibility are obviously different.The accumulative yields of gases containing-O are higher and that of gases containing-H are lower during the pyrolysis of three coals in Western China.
A New and Simple Method to Estimate f(E) and k0(E) in the Distributed Activation Energy Model from Three Sets of Experimental Data
Complex reactions such as coal pyrolysis reaction are often analyzed using the distributed activation energy model, in which the reactions are assumed to consist of a set of irreversible first-order reactions that have different activation energies and a constant frequency factor. The difference in the activation energies has been usually represented by a Gaussian distribution a priori. In this paper, a simple method is presented for estimating both the distribution curve of the activation energy, f(E), and the activation energy dependent frequency factor, k 0 (E), without any a priori assumptions for f(E) and k 0 (E). Only three sets of experimental data obtained under different heating profiles are required to obtain both f(E) and k 0 (E). The presented method was applied to estimate f(E) and k 0 (E) for the pyrolysis of three kinds of coals. f(E) was different significantly among the coals. It had a maximum at E = 240-260 kJ/mol and was spread over 150-400 kJ/mol. Estimated k 0 vs E relationship was little dependent on coal types, and k 0 increased from 10 11 to 10 26 s -1 as E increased from 150-400 kJ/mol. The applicability of the presented method to single reactions is also discussed.