Co-pyrolysis Characteristics Of Rice Husk And Cow Manure

As a large agricultural country,China is rich in agricultural biomass resources.As the fourth largest energy,biomass energy has the characteristics of renewable,clean and pollution-free.Pyrolysis technology can convert biomass into high-quality syngas.The quality of syngas is affected by temperature,residence time,pyrolysis atmosphere and pyrolysis substances.Tar,a black viscous by-product,will be produced during pyrolysis.Condensation of tar in the pipeline will block the pipeline,reduce efficiency,and cause great harm to human body and environment.In this paper,two typical agricultural wastes,rice husk and cow dung,were used for co-pyrolysis.The effects of the co-pyrolysis ratio of rice husk and cow dung,temperature,pyrolysis atmosphere and additives on their co-pyrolysis characteristics were investigated,and the effects of the prepared semi-coke catalyst on the co-pyrolysis hydrogen production and tar removal were also investigated.The main work is as follows:（1）First,the co-pyrolysis process and product characteristics of rice husk and cow dung were studied on a thermogravimetric analyzer and a fixed bed.From the thermogravimetric process,with the increase of the proportion of cow dung added,the shoulder peak moved to the high temperature zone,which promoted the completion of biomass pyrolysis at a higher temperature.The final thermal mass loss rate of cow dung is relatively high.The results show that the actual thermogravimetric loss rate of co-pyrolysis is higher than the theoretical thermogravimetric loss rate,and there is a synergistic effect.The product analysis of the fast pyrolysis experiment in a fixed bed showed that the addition of cow dung improved the hydrogen production effect of rice husk pyrolysis and increased the hydrogen production;Rice husk improved the problem of low CH₄ content and calorific value caused by high moisture content of cow dung.Co-pyrolysis causes ring opening of monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons,and also causes complete decomposition of nitrogen-containing components such as cellulose.Compared with N₂ atmosphere,CO₂ atmosphere reduces the activation energy of the reaction,promotes the deep pyrolysis of lignin,increases the content of aliphatic hydrocarbons,reduces the content and types of polycyclic aromatic hydrocarbons,promotes the fracture of methyl and methylene,and promotes the formation of H₂ and CO.The content of H₂and CO in RHCM11 pyrolysis at 800℃increases by 30.25%and 30.69%respectively.The formation of microporous structure of biochar was promoted under CO₂ atmosphere.（2）On the premise of co-pyrolysis research,three additives,Sn Cl₂,Zn Cl₂ and Fe₃O₄,were selected to investigate the effect of in situ on co-pyrolysis in N₂atmosphere.The results show that the additive can significantly improve the gas quality,increase the content of H₂ and reduce the content of CO.At the same time,additives can improve the distribution of liquid products,promote the pyrolysis of macromolecular heavy polycyclic aromatic hydrocarbons to produce small molecular light aromatic hydrocarbons,and reduce the amount of aliphatic hydrocarbons and oxygen-containing aliphatic hydrocarbons.Sn Cl₂ promoted the pyrolysis of lignin,thus promoting the increase of monomer phenol.Zn Cl₂ promoted the pyrolysis of hemicellulose,increased furfural compounds and inhibited the increase of monomer phenols.Fe₃O₄ promotes the fracture of methyl group and increases the content of CO₂ in the gas phase.（3）In addition,the biochar loaded metal Co catalyst was prepared.After activated by KOH,the pore effect of biochar was good,reaching 1230.8m²/g,and a large number of mesopores were added,which was conducive to the loading of metal cobalt.SEM and XRD characterization showed that the loading effect was good.When the loading metal was too much,the metal grain was larger.During the pyrolysis process of the catalyst,the content of H₂ and CO was significantly increased,with the maximum increase of H₂ from 4.55%to 13.68%,the maximum increase of CO from 19.78%to 32.25%,and the gas production increased by 21.9%.It promotes the fracture of C-C bond and C-O bond in tar,increases the content of phenols,ketones and aldehydes,reduces the content of oxygen in pyrolysis gas,and improves the quality of gas.In the repeated experiment,the production of H₂ is stable at 10%and the content of CO is stable at 27.5%.