Study On The Influence Of Different Metal Salt And Metal Oxide Catalysts On Characteristics Of Pyrolysis Of Lignite

At the present energy situation of rich coal with lack of gas and oil in our country,which give rise to a high efficiency utilization of coal resources.There are abundant low rank coal resources in our country,a lot of useful materials can be obtained through the catalytic pyrolysis of low rank coal,and also the pollution and waste of resources caused by direct combustion can be avoided.The introduction of the catalyst can improve the pyrolysis conversion rate and regulate the distribution and composition of pyrolysis products,which is of great significance to the fine and clean utilization of coal.In this paper,the catalytic pyrolysis characteristic of Inner Mongolia Huolin River lignite by loaded different types of metal salt catalysts?K₂CO₃?CaCl₂?FeCl₃ and MoS₂?and metal oxide catalysts?CaO?MgO?Al₂O₃?MnO₂?Fe₂O₃ and NiO?were studied.Experiments that study pyrolysis characteristic of different coal samples are carried out by Thermal-Gravimetric Analyzer?TGA?.By analyzing the TG-DTG curves obtained under constant heating rate,we investigated the catalytic effects on pyrolysis conversion rate,the maximum weight loss rate and the corresponding temperature with the addition of different kinds of catalyst.Under the condition of adding metal oxide catalyst,the pyrolysis conversion rate of lignite with addition of Ca O and NiO are relatively increased7.00% and 7.53%.And all the metal oxides exhibited distinct catalytic effect in lively pyrolysis stage except Al₂O₃.NiO shows the most significant catalytic effect in thermal condensation stage with peak temperature ahead of nearly 10 ? and the peak value of weight loss rate increased 0.0041 %/? compared with the raw coal.Under the condition of adding metal salts catalyst,the pyrolysis conversion rate of lignite with addition of FeCl₃ was increased 9.22% relatively.And the catalytic effect is mainly shows in the advance of the peak temperature in the lively pyrolysis stage.And all the metal salts exhibited distinct catalytic effect in thermal condensation stage except MoS₂.The peak temperature is ahead of nearly 10 ? and the peak value of weight loss rate increased0.0061 %/? with addition of CaCl₂ in this stage.The lignite pyrolysis reactions were descripted by means of kinetic model to simulatethe pyrolysis process and calculate the relevant kinetic parameters.The activation energy of coal with addition of catalysts are decreased to 22.49²9.29 kJ/mol,lower than that of raw coal which is 29.53 kJ/mol in lively pyrolysis stage.And also the activation energy of coal with addition of catalysts are decreased to 24.46 41.28 kJ/mol,lower than that of raw coal which is 44.52 kJ/mol in thermal condensation stage.In this paper,we systematically carried out the study on catalytic pyrolysis characteristics of lignite in a fixed bed reactor.The effect of catalyst on the yield of pyrolysis products?coal gas and tar?was investigated.Gas products were collected and analyzed by Gas Chromatography?GC?.The contents of CO₂,CO,CH4 and H2 in different coal samples were quantitatively analyzed.It is found that the relative content of each component in the pyrolysis gas can be changed at both 450 ?and 750 ?.And the liquid products were analyzed by Gas Chromatography-Mass Spectrometer?GC-MS?,and the characteristics of pyrolytic coal tar obtained by different coal samples were qualitatively and quantitatively analyzed.It was found that the main components of the tar derived from lignite and raw coal with the addition of catalyst all were light aromatics hydrocarbons,phenols,polycyclic aromatic hydrocarbons,aliphatic hydrocarbons and heterocyclic compounds.The addition of different kinds of catalysts all increased the content of phenols,polycyclic aromatic hydrocarbons and heterocyclic compounds while decrease the contents of light aromatic hydrocarbons and aliphatic hydrocarbons in different degrees.