The Effect Of Feedstock Property And Process Design For “thermal Dissolvent Carbon Enrichment” Of Biomass Wastes

Biomass is one of the most important renewable energy,and there are many methods to convert and use it.This thesis is an in-depth study on a method of biomass named thermal dissolution carbon enrichment(TDCE),which was proposed to deoxidize and upgrade biomass wastes effectively.Upgrading and multi-stage separation of the biomass were conducted under a mild condition using a non-polar solvent.Two main solid extracts were obtained: a high molecular weight extract(Deposit)and a low molecular weight extract(Soluble),along with some liquid,gas and an extraction residue(Residue).The carbon content and oxygen content of Soluble were as high as 81.0-83.3% respectively and as low as 7.3-11.1%,carbon content and oxygen content of Deposit were 76.5-89.5% and 1.1-15.4% respectively.The two extracts have wide application prospects in the preparation of high quality liquid fuel,high value-added carbon fiber and coking binder.On the basis of previous studies,this paper makes a detailed investigation on the influence of moisture and minerals of biomass on TDCE,and designs and optimizes the technological process with Aspen plus,so as to provide theoretical basis for the practical application of this method.The main conclusions were as followed:(1)The moisture in the biomass stimulates the formation of the main products during carbon enrichment,Soluble and Deposit.For example,the yield of Soluble from dry raw straw was 24.34%,while that of wet raw straw reaches 34.57%.The transformation paths to promote the extraction products are H2O+RD/Bio—>DP+SL and H2O+RD/Bio—>DP—>SL.The promoting effects of water on herbs and woody biomass are different,which may result form the comprehensive influence of water and ash.The moisture content have a small effect on the pyrolysis characteristic of Soluble,but it has significant effect on that of Deposit.Deposit from a biomass with high moisture contenthas the highest pyrolysis activity.With the increase ofmoisture content,the aromatic degree of extract increased slightly.On the whole,moisture content can promote the conversion of biomass on TDCE,but has little effect on the physical and chemical properties of the extract(2)The mineral in biomass has obvious effect on TDCE.For straw,86.3% K and 4.9% Ca were removed after washing,98.1% K and 90.4% Ca were removed after pickling.Both washing and pickling can promote the yields of Soluble.In particular,water washing increased the yields from 16.08 % to 19.57 %,but inhibited the production of gas products.Ca exists to promote the formation of Soluble and Liquid;K exists to a certain extent,promote the pyrolysis of Soluble,so as to get more gaseous product.The chemical structure and properties of straw and the extract were not affected by water washing and acid pickling.(3)On the basis of theoretical research,Aspen plus software was used to carry out the process flow design of biomass TDCE technology,and the preliminary design was carried out based on experimental parameters.The scheme well demonstrated the material and energy changes in the process However,the simulation process ignores complex chemical reactions and requires the actual experimental yield as the basis.To more closely linked with practical application,the designed scheme is optimized by streamlining the Soluble and solvent separation module,considering the Soluble and solvent as a mixture used for recycling the solvent,thus further increased the practical application feasibility of TDCE.