Characteristic Research On Gas By Pyrolysis Of Herb Residues Using Ni/CaO Catalysts

As a typical biomass energy,a large quantity of herb residues are produced in our country every year.To date,the basic treatment of herb residues is landfill and storage in fixed areas,both of which cause waste of resources and pollution of the environment.Reasonable utilization of herb residues via the thermochemical conversion technology will produce better economic and environmental benefits.However,the biomass pyrolysis process often produces a significant amount of by-products of CO₂ and tar,thereby limiting the biomass chemical conversion technology for industrial applications.Therefore,decoking and decarburization are critical issues that need to be addressed in the biomass gasification technology.In this paper,Ni is introduced into the CaO structure and Ni/CaO catalysts are prepared to explore the catalytic pyrolysis characteristics of herb residues.The effects of heating rate,pyrolysis temperature and catalyst addition on the pyrolysis process and products are investigated,combined with pyrolysis kinetics and infrared spectroscopy analysis to further explore the mechanism of herb residues catalytic pyrolysis.The absorption capability of recycled CaO declines rapidly with increasing number of cycle.It is well known that Ni-based catalyst has a good catalytic activity for the pyrolysis of tar.The use of calcium-based absorbers in combination with nickel-based catalysts will have a profound impact on the anti-deactivation properties of CaO cyclic absorption.More importantly,simultaneous pyrolysis of biomass,CO₂ removal,conversion of liquid macromolecules,adjustment of gas composition not only facilitate improve the energy density of the product gas and to increase the subsequent gas utilization efficiency but also can promote tar cracking and improve the production of hydrogen and other high-quality gas content.A series of Ni/CaO catalysts with different ratios of Ni content are prepared by using an isovolumetric impregnation method.Through various characterization methods,it is confirmed that Ni is well supported on CaO and the best loading of Ni is 10%Ni/CaO.The cyclic absorption experiment of catalysts showed that the deactivation rate of the catalyst is significantly slowed down after the loading of the nickel catalyst,10%Ni/CaO exhibiting a better resistance to deactivation and maintaining a high absorption capacity.The thermogravimetric apparatus is used to investigate the pyrolysis law of traditional herb residues in the process of temperature programmed.According to the experimental data,the two-component stage reaction model is selected as the kinetic model for pyrolysis of traditional herb residues.The simulation results are well fitted with the experimental data.Through the thermogravimetric infrared spectrometer?TG-FTIR?,the on-line analysis of the escaping gases during the pyrolysis of herb residues shows that the addition of catalyst changes the composition and release time of the pyrolysis gas,which play a role in fixing CO₂ and have a certain ability to remove tar.Compared with CaO,Ni/CaO is more beneficial to the removal of tar.The effects of different pyrolysis temperature and Ni addition on the catalytic performance of Ni/CaO catalyst are investigated on a self-made micro-pyrolysis test bench.The results show that CaO can effectively remove the CO₂ in the gas product,increase the calorific value of the pyrolysis gas,and reduce the yield of condensable liquids such as tar.When Ni is introduced into CaO catalyst,it is found that pyrolysis gas yield and gas calorie are increased,and the yield of condensable liquid is further reduced.The Py-GC/MS instrument is used to analyze the rapid pyrolysis liquid products of herb residues.It is explored that the high temperature and catalysts cause the tar product to be reduced by converting macromolecules such as furan and acid in the tar to light hydrocarbon small molecules.Take into account synthetically,it is considered that the optimal effect of adding10%Ni/CaO catalyst under the conditions of 700?,which the condensable liquid in the pyrolysis products is reduced by 28%,the CO₂ removal rate is over 60%,and catalyzed pyrolysis of herb residues yielded a gas production of 325.3 mL/g and a low pyrolysis gas calorific value of 18.6 MJ/m³.