| Chinese lignite resources is extremely rich.As the largest coalfield in South China,Zhaotong lignite has the characteristics of high moisture content,high ash content,low calorific value and poor stability.These characteristics affect the utilization of Zhaotong lignite pyrolysis,gasification and combustion.For these reasons,Zhaotong lignite has not yet been large-scale industrial applications.However,there is abundant humic acid content in Zhaotong lignite.The extraction of humic acid is an economic and environmental protection direction,and from a technical point of view,this is also a practical way to make use of Zhaotong lignite.However,after the extraction of humic acid,residue,but also contains more than half of the organic matter.At home and abroad,the use of this part of the residue is very little.If it is not used,will cause a great waste of resources.In this paper,the pyrolysis characteristics of lignite residue from Zhaotong lignite were studied.In order to realize the basic data for the realization of cascade utilization of "Extraction of humic acid from lignite in Zhaotong——residue pyrolysis".In this paper,the yield of pyrolysis gas,tar and char,the composition and content of pyrolysis gas,the composition and content of tar and the industrial analysis of char were analyzed and compared.The following four parts of research work are carried out:Firstly,a comparative study of the pyrolysis of residue and Zhaotong lignite was carried out to investigate the effect of humic acid on the pyrolysis characteristics of lignite.Secondly,the effects of temperature,heating rate,pyrolysis atmosphere and constant temperature time on the pyrolysis characteristics of residue were studied.Thirdly,the residue was treated by demineralization and compared pyrolysis characteristics before and after ash removal.To study the influence of the inherent minerals in the residue on pyrolysis characteristics.The effects of the addition of minerals on the pyrolysis characteristics of residue were studied by adding metal salts(KCl,NaCl,CaCl2,MgCl2,FeCl3,and so on).Fourthly,the kinetic analysis of the pyrolysis process was carried out to investigate the pyrolysis kinetics of residue and the effect of minerals on pyrolysis kinetics.The results show that:(1)Compared with Zhaotong lignite,the pyrolysis gas and tar yield of residue are decreased.The pyrolysis gas yield of lignite is 0.3532L/g and the pyrolysis gas yield of residue is 0.2240L/g.The tar yield of lignite is 3.24%and the yield of residue is 2.60%.The char yield of residue is higher than that of lignite.The char yield of lignite is 49.16%and the residue is about 57.40%.The content of H2 in lignite pyrolysis gas is 30.15%,and the H2 of residue pyrolysis gas is 38.52%.The main component of the residual pyrolysis gas(H2+CO+CO2)accounted for more than 60%.In the tar of residue,the molecular structure is complex,the carbon content is high,and the average molecular mass of is larger.The content of organic matter in char of residue is decreased,the ash content of char is increased and the calorific value of is decreased,but the calorific value si higher than the national minimum calorific value.(2)Temperature,heating rate,pyrolysis atmosphere and constant temperature affect the pyrolysis characteristics of residue in varying degrees.When the pyrolysis temperature increased from 400? to about 800?,the yield of char decreased from 67%to 57%,the yield of tar increased from 0.48%to 2.3%,and the yield of pyrolysis gas increased from 0.0536L/g to 0.1572L/g.The content of H2 and CO in the pyrolysis gas increased steadily.The trend of the content of CH4,CO2 and C2H4,C2H6 are similar to that of temperature,and all of them increased with the increasing of temperature and then decreased.The content of polycyclic aromatic compounds in tar increased gradually,and the content of chain alkanes and alkenes increased.As the heating rate increased to 35K/min from 15K/min,the char yield increased from 61.84%to 63.36%,the yield of tar decreased from 1.92%to 1.61%,the pyrolysis gas yield decreased from 0.1396L/g to 0.1324L/g,pyrolysis gas component content decreased,can be detected in the tar compounds decreased,alkanes,olefins content decreased.Aromatic compounds in tar will increase loop phenomenon,the molecular weight of tar component will increase.Pyrolysis under the steam atmosphere can get higher gas and tar production rate and the content of H2 in pyrolysis gas is higher,low molecular weight fractions of tar increased;oxygen atmosphere the pyrolysis product yield decreased,more in the gas content of CO2,increase the content of polycyclic array of component in CO2.under the atmosphere of char yield more,higher gas content in CO.In the atmosphere of CO2,the yield of char is higher,and the content of CO in prolysis gas is higher.In the process of constant temperature time from 10min to 20min,the yield of pyrolysis gas is improved and the yield of tar and char are decreased.In the process of constant temperature time from 10min to 50min,the relative content of H2 increased from 19.90%to 20.78%,the content of CO2 decreased and the content of CH4 increased slightly.In the process of constant temperature time extended from 10min to 30min,the content of CO is gradually rising,then with the prolonging time basically showed a stable trend,the content of C2H4 with the prolonging time decreased slightly,the content of C2H6 does not change significantly.With the increase of the temperature time,the tar components are transformed into the macromolecular components.(3)The presence of inherent minerals in residue reduced the yield of pyrolysis gas and tar,increased the content of H2 in the pyrolysis gas,increased the number of aromatic rings,increased the content of heavy tar,and increased the average molecular weight of tar components.The addition of metal salt can increase the yield of pyrolysis gas and char.The difference is that alkali metal salt reduces the yield of tar,increase the contents of H2 and CO2 in the gas,increasing the content of 'fatty compounds in tar,reduced the content of phenolic compounds in tar and phenanthrene,tar components of low molecular weight substance increased,tar more lightweight components,improve the quality of the tar.Alkaline earth metal salt can improve the content of H2,CO and CO2 in prolysis gas,increase the number of aromatic rings and molecular tar component quality,the tar component becomes heavier.The transition metal salt can decrease in the content of H2 in prolysis gas,increase the prolysis gas contents of CO2 and CH4,and a significant increase the tar component in aliphatic hydrocarbons,reduce the content of single ring and three ring aromatic hydrocarbons.(4)The pyrolysis of residues can be described by a first-order kinetic model.The kinetic results indicate that inherent minerals inhibit the pyrolysis of residue.while the addition of metal salts plays a catalytic role in the pyrolysis of residues.By calculating the apparent activation energy parameters show that the catalytic effect of the metal salt in the order:MgCl2>CaCl2>FeCl3>KCl>NaCl>NiCl2. |
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