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Effect Of Hydrothermal And Acid/Alkali-hydrothermal Pretreatment On Hydrolysis And Anaerobic Digestion Of Corn

Posted on:2017-02-23Degree:MasterType:Thesis
Country:ChinaCandidate:S Y FanFull Text:PDF
GTID:2271330485968776Subject:Environmental Science and Engineering
Abstract/Summary:PDF Full Text Request
Corn straws are considered to be the abundant source of renewable biomass. China produces large amount of agricultural lignocellulose every year, and a big part of them is burnt or wasted, which cause resource waste as well as environmental pollution. Converting corn straws to reducing sugar by enzymatic hydrolysis or CH4 by anaerobic digestion is a good way to enhance the sustainablility of economy, environment and ecosystem. However, the cell wall structure of corn straw is extremely stable and can not be degraded easily. Thus, research on pretreatment of corn straws with low pollution and high efficiency is very important for the biomass degradation and energy production.Hydrothermal pretreatment is one kind of pretreatment methods. Hydrothermal pretreatment could remove hemicellulose, and hemicellulose content reduced to 2.87% when the pretreatment temperature was 200℃. The highest yield of reducing sugar (1.69 mg/mL) was achieved at a hydrothermal temperature of 160℃, which was 83.7% higher than that of control. At a hydrothermal temperature of 180℃, the maximum biogas production was achieved, which was 1.66 times as much as that of control. Hemicellulose content reduced to 7.2% after hydrothermal pretreatment at 160℃ under 120 min. The optimal hydrothermal time was 120 min, which led to a highest reducing sugar yield of 1.56 mg/mL, 2.43 times as much as that of control. The hydrothermal pretreatment for 30 min reached a highest amount of biogas production of 1561 mL,2.06 times as much as that of control. The ratio of solid to liquid was an insignificant influencing factor. Hemicellulose content kept stable under different solid:liquid ratio. Reducing sugar yield was the highest when the solid:liquid ratio was 3:30.To improve the effect of hydrothermal pretreatment on corn straws, a certain amount of H2SO4 or NaOH was added into the hydrothermal pretreatment system. NaOH could neutralize H+ produced during hydrothermal pretreatment process, which hinder the destruction of surface structure of corn straws. NaOH improved the biodegradability of corn straws through dissolving lignin. When the NaOH dosage was 0.5%wt, reducing sugar yield of NaOH-hydrothermal pretreatment was 3.78 times as much as that w ith hydrothermal pretreatment alone and the biogas production was 1.46 times as much as that with hydrothermal pretreatment alone. H2SO4 could improve the destruction of surface structure of corn straw by increasing the H+ concentration. When the H2SO4 dosage was 0.5%wt, reducing sugar yield was 3.53 times as much as that of control. However, the enhancement in biogas production with H2SO4 addition was insignificant.
Keywords/Search Tags:Corn straws, hydrothermal pretreatment, enzymatic hydrolysis, anaerobic digestion
PDF Full Text Request
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