Mechanism Study On Concentrated Solar Pyrolysis Of Biomass Three Components

With the rapid development of Chinese economy,energy consumption is increased day by day.In the near future,one of the most urgent problems is failing to keep pace with the every-increasing energy demands and avoiding excessive environmental degradation.Coupling solar energy with biomass resources to replace traditional fossil energy can relieve the problems of China like unreasonable energy structure,high energy consumption and heavy pollution.Recently,however,the specific reaction mechanism and the influence of additives like molten salt to pyrolytic reaction path should be further studied.The essay studied the influence of the ternary eutectic carbonate of LiNaK under a temperature of500-700℃on the biomass pyrolytic reaction path and the dynamics mechanism,used biomass component materials directly to improve universality of the conclusion,had a deep study on different reaction paths and dynamics mechanism of various biomass components under the medium of molten salt and sought for approaches to feed back the conclusion to the whole with the purpose of providing effective theoretical support to coupling application of solar energy and biomass with molten salt in industry.First,the essay had thermogravimetric experiment on the 6 samples under the conditions of having and having no salt and discovered the warming pattern of 20℃/min.Under the N₂ blowing environment of 100mL/min,within a range of 150⁶00℃,addition of ternary eutectic carbonate can greatly improve the average activation energy in the cellulose and hemi-cellulose pyrolysis process,for example,cellulose reached 12.802kJ/mol.However,the influence mainly acted on sections of low temperature.Under the actual working conditions,raw materials would be heated rapidly and reach high temperature at the fourth stage.At this stage,changes brought by ternary eutectic carbonate to biomass component pyrolysis activation energy are not obvious.That is to say,under the working conditions,molten salt does not have a big influence on the biomass component pyrolytic reaction mechanism;moreover,at the same stage,addition of ternary eutectic carbonate would make the pyrolytic reaction frequency factorA₄ of the three components improve by 9.59,3.64and 4.82 times,thus greatly improving pyrolytic reaction rate.Afterwards,the essay made full use of the three-component pyrolysis data obtained in the experiment,as well as the pyrolysis activation data of typical biomass materials in textbooks,and according to the simple overlay model,it had a simple coupling of the total-fraction relationship.In view of the current data,constitution of the biomass pyrolysis activation energy can basically meet the formulaE=x₁ E₁+x₂ E₂+x₃ E₃-5.13n₁-7n₂+25.09.Next,according to the preliminary analysis on whether cellulose,hemi-cellulose and lignin use pyrolysis product distribution of salt the distribution,it proposed the possible influencing mechanism of molten salt on the pyrolysis pathway of three components:in a pyrolytic competitive reaction of cellulose and hemi-cellulose,make the path of producing dehydrated cellulose more advantageous,and meanwhile,improve the percent conversion of the secondary cracking of the three components comprehensively,and thus cause gas-solid productivity increase and liquid productivity decrease;at the same time,during the process,it was found that the carbonate above 600°C would react with the pyrolysis products and generated a large amount of CO₂.Therefore,the subsequent experiments and analysis mainly focused on the action of carbonate of 600°C.Then,the essay analyzed the specific composition of the pyrolysis tri-state products.It was found that the three-component pyrolysis products under salt medium had better quality improvement effect.Moreover,according to the temperature and raw material,molten salt would produce different benefits,heat value of gas below 500°C will be improved comprehensively;although heat value of gas below 600℃had a decline,pyrolysis gas productivity of hemi-cellulose and lignin had a significant increase.Meanwhile,with increase of temperature,H₂ improvement was lower than that of the other three conventional gas products.Even though the production of CO₂ was slightly lower than that of gas hear value,productivity of combustible gas was generally improved as a whole,and thus it can be regarded as active.At the same time,the salt environment exacerbated the secondary pyrolysis of pyrolysis oil and improved the yield of small molecule products in the pyrolysis oil,which is true for the three-component pyrolysis but the product composition is different;in addition,use of salt medium can reduce the ignition temperature of the three-component pyrolysis carbon residue comprehensively（reduced by 90-400°C）and improved its flammability rate（the ignitability of lignin residual carbon can be increased by 63.7%）,which can greatly improve the potential of reuse of solid products.At last,after making sure that application of fusion ternary eutectic carbonate as the medium could have comprehensive active effects on the biomass three-component pyrolysis process,the essay studied its reusability and discovered that under high temperature,ternary eutectic carbonate would react with pyrolytic carbon products and lost its activation.Under the temperature condition of 600℃,the process is slow,but the inactive salt has the capacity to reabsorb CO₂.Moreover,after absorbing CO₂,although it cannot recover to the catalytic activity of the original state,its catalytic ability can be recovered to a certain degree.To sum up,the essay put forward that ternary eutectic carbonate had a favorable catalytic effect on pyrolysis of various components of biomass.Besides improving pyrolytic reaction rate greatly,it could also improve quality of tristate products.Meanwhile,as the catalytic medium,eutectic salt have the favorable repeated practicability and the potential to be developed and used in solar biomass pyrolysis technology.