Integrated Process Of Coal Pyrolysis With Dry Reforming Of Low Carbon Alkane

Coal is the major primary energy of China which accounts for more than 50%of primary energy consumption.With the stricter requirement of enviromental protection,it is significant to develop clean and effective technology of coal comprehensive utilization for relieving environmental pressure.Coal pyrolysis is an important conversion technology of clean and efficient coal utilization,which is the basic process of coal conversion.Pyrolysis tar is the main source of polycyclic aromatic hydrocarbon and the potential alternative to liquid fuel which is important to ensure national energy security.Tar yield of traditional pyrolysis process is low with poor quality.To solve the problem,an integrated process of coal pyrolysis with low alkane reforming（CP-DRA）was used in this paper to improve tar yield and quality by optimization of catalyst composition and process parameters.The mechanism of integrated process was illustrated and the process universality was also studied.The major research works and results of this dissertation are as follows:Dry reforming and integrated coal pyrolysis with different CH4/C2H6 ratio over Ni/Al2O3 were studied.The additional C2H6 can promote the reforming process.The tar yield of CPDRM is 18.4 wt.%,which is 1.06 times that of CP-N2.The optimization of CH4/C2H6 ratio can promote tar yield.When CH4/C2H6 ratio is 8:1,2:1 and 1:1,the tar yield is 18.6,19.2 and 18.7 wt.%,respectively.Also,the light oil content of CP-DRA is 10 wt.%which is higher than CPN2（6 wt.%）.10 wt.%Ni/La₂O₃ was papered and studied the effect for reforming and integrated pyrolysis process.To compare with Ni/Al2O3,Ni/La₂O₃ shows a higher gas conversion with less carbon deposition of DRA and higher tar yield of CP-DRA.At 600℃,the tar yield of CPDRA is 20.6 wt.%,which is 1.09 and 1.18 times that of CP-N2 and CP-DRM,respectively.After many times regeneration,tar yield stables at 20.5 wt.%which shows good stability of Ni/La₂O₃.And the carbon deposition of Ni/La₂O₃ is 0.3 g/gcat which is less than 0.38 g/gcat of Ni/Al2O3.The characterization shows that La₂O₃ can transform to La2O2CO3 during the reaction which can inhibit carbon deposition.The weight loss detected by TG and CO2 signal detected by in-situ Py-TOF-MS confirm the formation of La2O2CO3 and the decomposition for CO2 which can reduce carbon deposition from 0.38 g/gcat of Ni/Al2O3 to 0.3 g/gcat of Ni/La₂O₃.ZrO2 was used to modify La₂O₃ to inhibit carbon deposition and improve stability.The La/Zr ratio was studied for DRA and CP-DRA.The result shows when ratio La/Zr is 4:1（Ni4LaZr）,the carbon deposition is 0.1 g/gcat of DRA at 600℃.Tar yield is 20.5 wt.%of CPDRA which is stable during the regeneration.The result indicates the good stability of Ni4LaZr.The catalyst was characterized by several ways.The La2Zr2O7 formed by ZrO2 addition which has a stable pyrochlore structure to improve catalyst stability.With excess La₂O₃ to inhibit carbon deposition,Ni4LaZr shows a good performance with less carbon deposition and higher tar yield.According to the process parameter study over Ni4LaZr,the increase of Ni loading,gas flow and decrease of space velocity can improve tar yield.Small amount of C2H6 addition also can improve tar yield.The CP-DRA shows a lower tar average molecular weight than CP-N2,which is 415 and 424 amu,respectively.Tar of CP-N2 contents more aliphatic components than aromatic components.CP-DRA tar contents more aromatic component than that of CP-N2.Isotopic trace method was used to explore the integrated process mechanism by CD4 and C2D6.The signal of D was detected by D-NMR which means that CD4 and C2D6 participate in pyrolysis process by production of·D,·CD3,·C2D5 and other radicals.The tar yield is improved by reaction between gas radicals and coal radicals during pyrolysis.According to the tar analysis,the isotope ion peak intensity of aromatic components increases obvious which means alkane radicals react with aromatic radicals to improve tar yield which also improve the content of aromatic and CH3 group of tar.The universality of process was also tested.CP-DRA of three different coal samples（BYH,BLG and YL coal）also shows higher tar yield than that of CP-N2.And integrated process is also suitable for CP-SRA and CP-DSRA.The tar yield of CP-DSRA shows a higher tar yield than other process which is 20.7 wt.%.The result shows that a good adaptability of coal and process for integrated process.The tar upgrade also be tested over Ni4LaZr which shows a higher light tar content which also can be tar upgrading catalyst.