Co-combustion Characteristics Of Coal Slime And Corn Stalk

A large amount of coal slime is formed during coal washing.The productivity of coal slime is very huge and it can cause serious environmental problem.Combustion is one of the most important ways to exploit it,but it is difficult to burn due to its characteristics of high contents of ash and it releases a great of polluting gases in the process of combustion and utilization.The corn stalk has the characteristics of loose tissue,low sulfur content and high content of volatile that it is easy to ignite,and carbon residual rate is low during combustion.Co-combustion of coal slime and corn stalk can improve combustion characteristics of coal slime and reduce emissions of polluting gases.At present,some work about co-combustion of coal and biomass has been done.As to the coal and biomass species and experimental conditions are different,the results are not the same.At the same time,most of the related studies are only about co-combustion of coal and biomass by simply mixing,but have no comprehensive analysis.At present,co-combustion of coal slime and biomass has not been reported yet.Aimed to current situation,coal slime and corn stalk were selected as raw materials,and the combustion characteristics of coal slime and corn stalks,coal slime and corn stalk char and the influence of mineral on co-combustion of coal slime and biomass were studied,the main conclusions were as follows:(1)Corn stalk could improve the combustion characteristics and combustion efficiency of coal slime,and decrease ash fusion temperature of blends.The combustion of coal slime was mainly the combustion of fixed carbon by analyzing the TG-DTG curves of coal slime,corn stalk and the blends.The presence of higher volatile matter in corn stalk could greatly lower the ignition temperature and burnout temperature of coal slime,and improved burn-out rate and combustion efficiency of coal slime.There was no synergistic effect between coal slime and corn stalk in the combustion process.Reaction order was determined by Coats-Redfern method.The coal slime combustion approached first-order reaction and the corn stalk combustion approached the second order reaction.The activation energy of coal slime combustion was about 71 kJ/mol and the E of corn stalk was about 35-62kJ/mol.Moreover,activation energy decreased as the percentage of corn stalk increased initially and increased afterwards.With the increasing of the percentage of corn stalk,coal slime ash melting point decreased,which was contributed to the formation of hypothermia amalgam by alkali and alkaline earth metal in corn stalk with silicate in coal slime.(2)Corn stalk char could promote the combustion of coal slime.The corn stalk can promote the combustion of coal slime due to higher content of volatile matter.In order to investigating the impact of corn stalk char on the combustion of coal slime,corn stalk pyrolysis was at 400 ℃.According to the TG-DTG curves of coal slime,corn stalk char and blends,corn stalk char can also promoted the combustion of coal slime,but its promoting effect weakened as compared with raw samples which were not pyrolysis.The corn stalk char combustion approached the second order reaction,the E of blends decreased as the percentage of corn stalk char increased.(3)The inorganic matters in coal slime hindered the combustion of coal slime.In contrast,the inorganic matters in corn stalk promoted the combustion of corn stalk significantly.Minerals are inorganic microscopic components in fuel,which have significantly effect on combustion.By TG-DTG curves analysis of demineralized coal slime,corn stalk and blends,we found that the inorganic matters in coal slime inhibited the decomposition and released of volatile matters and the combustion of fixed carbon.However,the inorganic matters including CaO,K2O and MgO in the corn stalk catalyzed the decomposition of volatile matters and accelerated the combustion of biomass char.Comparison of combustion process between raw samples and demineralized samples showed that the presence of mineral in coal slime increased the activation energy and ignition temperature,while the role of inorganic minerals in corn stalk were exactly opposite.