Experimental Research On Hydrothermal Carbonization Of Wheat Straw By Reutilization Of Reactive Solution

Hydrothermal carbonation(HTC)is a technology to convert biomass into solid product with high carbon content and high calorific value by using at least saturated water.It can achieve the purpose of carbon sequestration and the effective use of biomass energy.It has received widespread concern due to its wide use.With the development and application of the technology,the effective use of liquid products has become one of the key issues that need to be solved urgently.This paper was performed under the auspices of the National Natural Science Foundation of China "Research on migration and sequestration mechanism of carbon in hydrothermal treatment liquid of biomass".The wheat straw was used as raw material,and the hydrothermal carbonation reaction solution was reused as solvent.Organic element analyzer(CHRD),X-ray diffraction(XRD),infrared spectroscopy(FTIR)and thermogravimetry(TG)were used to analyze the composition,microstructures,chemical functional groups,and thermal stability of the HTC solid product of wheat straw.High Performance Liquid Chromatography and Mass Spectrometry(HPLC-MS),Ion chromatography and iodometric method were used to quantitative analysis of5-hydroxymethylfurfural(5-HMF)and furfural,acetic acid and reducing sugar in the liquid product.The resource utilization of the reaction solution was studied under different reaction conditions.The main workis:(1)The kinetic model of HTC reaction considering the whole component of biomass was established and verified by the experimental data of HTC wheat straw obtained at 200~240? and30~180min.The kinetic parameters of HTC of wheat straw were calculated.The results showed that the biomass components interacted with each other during the hydrothermal carbonation process.The activation energies of the hydrothermal reactions of the hemicellulose and cellulose were 54kJ/mol and136kJ/mol,respectively.(2)he reaction solution of HTC wheat straw obtained at 220? and 120 min was used as solvent,and then the HTC experiments of wheat straw was carried out at 160~240? and 120 min.It was found that with the increase of the reaction temperature,the HTC solid yield of the wheat straw with reaction solution increased by about 2~5% compared with the pure water environment.The degree of aromatization and the thermal stability of the solid product increased.The concentration of reducing sugar in liquid product decreased from 7.572g/Lat 160? to 2.753g/Lat240 ?,the concentration of acetic acid increased from 2.698g/L to 6.852g/L,and the concentrations of furfural and 5-HMF changed very small.The accumulation of acetic acid catalyzed the hydrothermal carbonation process,and the reaction solution recovery was beneficial tothe carbon sequestration in the liquid product andthe decrease ofthe reaction severity.(3)The hydrothermal carbonation of wheat straw was conducted with recycling the reaction solution 10 times.The experimental conditions were at 220?,120 min and the liquid-solid ratio of30:1.The results showed that the yield and carbon sequestration rate of the solid product increased with the times of the reaction solution increasing,the order,the degree of graphitization of the microcrystalline structure and the thermal stability of the solid product increased.The yield and the carbon content of the aqueous product reduced.When the reaction solution was recycled 6 times,the yield of the water soluble product was 15% and the carbon mass fraction was 5%,and the change was not significant.The reducing sugar,furfural and 5-HMF concentration decreased,while the acetic acid concentration increased to be the catalyst in the hydrothermal carbonation reaction.When the reaction solution recycled 10 times,the concentration of the acetic acid reached18.32g/L.(4)The saccharide compounds are the main components of the hydrothermal carbonation solution of wheat straw.In order to explore the effect of the recovered reaction solution on the hydrothermal carbonation process of the wheat straw,the hydrothermal carbonation of wheat straw was carried out with different amounts of glucose addition in water at 220 ?,120 min and liquid-solid ratio of 30.The results showed that the yield of solid and gas products increased gradually with the increase of glucose content,and the yield of liquid products decreased gradually.When 4g of glucose was added,the yield of the solid product was 68.56%.The infrared absorption characteristic peaks,XRD diffraction peaks and thermal stability of the solid product polymers were decreased.The concentrations of furfural,5-HMF and acetic acid increased compared with the liquid products in the pure water environment.The concentration of 5-HMF was 20.21 g / L as4 g glucose was added.