Integrated Process Of Coal Pyrolysis With Catalytic Reforming Of Methane

The coal pyrolysis-based staged conversion technology is an important direction of coal polygeneration technology and an effective method of realizing clean and efficient utilization of low-staged coal. The key issue of improving economy and feasibility of coal pyrolysis-based staged conversion technology is improving tar yield and quality at low-medium pyrolysis temperature. Focusing on the interaction between coal pyrolysis and methane-riched gas activation, aimed for improving tar yield and tar quality of coal pyrolysis, the main research works and results of this dissertation are summarized as follows:(1) Xilinguole lignite (XL) pyrolysis under methane or methane activated by Ni based catalyst was analyzed by TG-MS, while tar and char products distribution of XL pyrolysis were obtained by fixed-bed reactor. Results show that, methane is activated by Ni based catalyst into active species, which reacted with free radicals and fragments of coal pyrolysis, promoting the evolution of lighe aliphatic hydrocarbon and light aromatic hydrocarbon and increasing tar yield. In coal pyrolysis under methane without catalyst, due to the catalysis effect of minerals in coal or the induce action of coal radicals, methane is activated to promote the evolution of light aliphatic hydrocarbon and light aromatic hydrocarbon of coal pyrolysis. The results from kinetics computation of Huolinhe liginite (HL) pyrolysis under methane calculated by distributied activation energy model (DAEM) proved that coal pyrolysis under methane have lower activation energy with narrower distribution ranges.(2) The integrated process of coal pyrolysis with steam reforming of methane (CP-SRM) was investigated. The results of the effects of pyrolysis conditions on tar yield shows that the key point for higher tar yield of coal pyrolysis is increasing the active species produced from steam reforming of methane. With the pyrolysis condition as total gas flow rate 500 mL/min, methane flow rate 220 mL/min, steam to methane ratio 1 and pyrolyzed for 30 min, XL-SRM achieves highest tar yield at 550-750 ?, which is 1.7-2.1 times and 1.4-1.9 times that from coal pyrolysis under nitrogen and hydrogen, respectively. The content of light tar (< 360 ?) from XL-SRM at 650 ?, accounts for 73.6%, which is 1.3 times and 1.2 times the light tar content from coal pyrolysis under nitrogen or hydrogen, respectively. Meanwhile, the content of phenol, naphthalene and C1-C3 alkyl substituted benzene; phenol and naphthalene in tar from CP-SRM are improved. Results from gas analysis, tar test and designed coal pyrolysis experiments proved that, CP-SRM is beyond the process of coal pyrolysis under mixed gas of steam reforming of methane (SRM), but a process during which active species from SRM participated in coal pyrolysis for coal radicals'stabilization, and improving tar yield.(3) The integrated process of Huolinhe lignite pyrolysis with methane catalytic reforming was investigated focusing on the effect of gas feed composition on tar yield and quality. In catalytic reforming of methane (steam reforming of methane with oxygen, CO2 reforming of methane with oxygen and tri-reforming of methane), methane conversion increase with the increase of O2 content. In coal pyrolysis with catalytic reforming of methane, the effect of O2 content on tar yield has different rules with different methane catalytic reforming process, but the effect on tar quality is similar as lower the asphaltene content. During all the integrated process of coal pyrolysis with catalytic reforming of methane, integrated process of coal pyrolysis with tri-reforming of methane (HL-TRM) achieves highest tar yield as 21.0%(700 ?), which is 1.8 and 1.6 times that from coal pyrolysis under N2 and H2,rrespectively. Meanwhile, CP-TRM achieve tar with higher light tar content, further improving tar quality.(4) Mechanism of the integrated process of coal pyrolysis with methane catalytic reforming of methane was investigated through experiments with D2O\CD4 or 13CH tracers. Tar products as phenols and naphthalenes were analyzed by GC/MS. Through the MS comparison of tar products as phenols and naphthalenes, the integrated process of coal pyrolysis with methane catalytic reforming was further vertify:in the integrated process of coal pyrolysis with catalytic refoing of methane, active species produced in catalytic bed transport into coal bed, reacting with coal radicals, adding onto the active site of broken coal bond to form stable tar components or char structures. Results of the analysis of D or 13C content in tar and char detected by IRMS shows that D content in char were higher than that in tar in integrated process with D tracer, tar from CP-TRM has higher D content and char has lower than those from CP-SRM while 13C in char accounts for content content in both process. This implies that during the reaction of coal radicals and active species produced from methane catalytic reforming, H has higher reactivity and larger amount taking part in coal pyrolysis than-CHX, while structures formed from coal radicals stabilized by-CHV are more stable.