【作者】 孙优善；

【导师】 张书廷；

【作者基本信息】 天津大学 ， 环境工程， 2011， 博士

【摘要】 秸秆规模化厌氧发酵制沼气是最为有效资源化利用方法之一。由于秸秆木质纤维素含量高,直接对其进行厌氧发酵,不仅发酵速度慢、产气量少,而且利用率低。因此,需要对其进行适当的预处理,以提高其可利用性。本文针对秸秆难水解的问题,从原料特性和预处理两方面,对改善秸秆性质的保质贮存（或称青贮）方法以及提高可生化性的可溶化方法进行了探讨。实验将鲜玉米秸秆切成1-3 cm的小段,通过添加硝酸、乙酸和氨水等添加剂对切段后秸秆进行青贮。此外,还利用家用榨汁机,对切段后的秸秆进行榨汁处理,并以乙酸作为添加剂对秸秆榨汁渣进行青贮。通过分析青贮期完成后秸秆组成的变化,对青贮效果进行了初步评价。结果表明,与风干杆相比,青贮秸秆的木质素含量降低了12.3-25.8%,结晶度指数降低了4.4-20.1%。对上述青贮秸秆进行高温热水预处理,并与风干秸秆在相同反应条件下的处理效果进行比较。结果发现,乙酸组青贮秸秆的总糖得率最大值是风干秸秆最大值的2.4倍。采用ZnCl₂, FeSO₄, Fe₂（SO₄）₃, FeCl₃和Fe（NO₃）₃作为催化剂对对照组（无添加剂）青贮秸秆进行催化水解,研究发现,硝酸铁对秸秆中半纤维素水解的催化效果最好。利用硝酸铁对氨水组（添加氨水）青贮秸秆进行处理,并对硝酸铁浓度、反应时间和反应温度进行了优化。结果表明,硝酸铁为0.05 M,在150℃下,处理10 min时,水解液中的木糖产率达到91.8%理论木糖值,水解液中总糖浓度为33.48 g/L,糠醛浓度仅为0.03 g/L。为了进一步提高秸秆水解效率,降低催化剂用量,本研究还探索了秸秆经不同溶液低温浸泡,再对浸泡后的渣进行高温硝酸铁催化水解的两步处理法。结果表明,Tween-80溶液和去离子水作为低温浸泡液的两步处理法的总糖得率比直接硝酸铁处理法分别提高了17.5%和12.1%,硝酸铁用量分别减少了31.9和28.3%,而氨水作为浸泡液的两步处理法总糖得率小于直接处理法。虽然Tween-80浸泡处理效果比去离子水稍好,但考虑到Tween-80的添加会增加试剂成本,因此,去离子水是比较适宜的低温浸泡液。此外,还利用去离子水作为低温浸泡液的两步处理法对不同的秸秆进行了处理,均取得了较好的水解效果。本文还对硝酸铁催化对照组和硝酸组（添加硝酸）青贮秸秆中的半纤维素水解动力学进行了研究。采用Seaman模型对实验数据进行分析,得到木糖的生成速率和降解速率。结果表明,Saeman模型能够很好的预测硝酸铁催化青贮玉米秸秆中半纤维素的水解反应。并应用阿累尼乌斯方程计算出对照组和硝酸组青贮秸秆的半纤维素水解活化能分别为44.4和3.1 kJ/mol。更多还原

【Abstract】 Using corn stalk to produce biogas by anaerobic fermentation in large-scale is one of the most effective and promising utilization methods for agricultural wastes. While the lignocelluse content in corn stalk is very high, it will lead low efficieny, low biogas production and low utilization rate if corn stalk was used to produce biogas by anaerobic fermentation without pretreatment. Therefore, suitable pretreatment to corn stalk is very necessary for good utilization and biogas production. In this thesis, the ensiling methods and pretreatment methods were investigated to improve corn stalk and enhance anaerobic digestion process.Corn stalk was cut to pieces with length of 1-3 cm, and some additives of nitric acid, acetic acid and ammonium hydroxide were added to make corn silages. Moreover, some corn stalk was compressed by extractor and acetic acid was added to the residues after compressed to make silage. The quality of the silages were evaluated by determining the varieties of chemical compostion in corn stalk after silage period. The results showed that the content of Klason lignin and crystallinity index for corn stalk silage decreased 12.3-25.8% and 4.4-20.1% compared to air-dried corn stalk.Corn stalk silage and air-dried corn stalk were treated with liquid hot water. The pretreatment results showed that the maximum soluble sugar yield of corn stalk silage was 2.4 times compared with that of air-dried corn stalk.Five inorganic salts, ZnCl₂, FeSO₄, Fe₂（SO₄）₃, FeCl₃ and Fe（NO₃）₃ were chosen as catalysts to determine their effects on hemicellulose hydrolysis in control silage （no silage additive）. The results indicated that Fe（NO₃）₃ was the most efficient catalyst for hemicellulose hydrolysis. The effects of Fe（NO₃）₃ pretreatment conditions on sugar yields were investigated for corn stalk silage. Optimum pretreatment condition was obtained at 150 oC for 10 min with 0.05 M Fe（NO₃）₃, at which the yields of xylose in liquid achieved 91.8% of initial xylose, and the concentration of total sugar achieved 33.48 g/l,while the inhibitor concentration was only 0.03 g/l.In order to improve the hydrolysis efficiency of corn stalk and decrease the dosage of catalyst, the study introduced two-stage method to pretreat corn stalk. First, corn stalk was immersed by different solution at low temperature, and then the residues after immersion were pretreated by Fe（NO₃）₃ at high temperature. The results showed that compared with pretreated by only Fe（NO₃）₃, the total sugar yield improved 17.5% and 12.1%, while the dosage of Fe（NO₃）₃ reduced 31.9% and 28.3%, respectively, when Tween-80 and deionized water used as immersed solution. When ammonia water was used as immersed solution, the total sugar yield was lower than that pretreated by only ferric nitrate. Though the effect of Tween-80 is a little bit better than deionized water, while it can increase the cost of the process, so deionized water was recommended to be used as immersion solution. Moreover, the two-stage method was used to pretreat different types of corn stalk when deionized water was used as immersion solution, and all the experiments got good results.The kinetics of Fe（NO₃）₃ catalyzed hydrolysis for control silage and acid silage （treatment with HNO₃） were investigated at various pretreatment conditions. The results demonstrated that Saeman model was well consistent with Fe（NO₃）₃ catalyzed hydrolysis reaction for corn stalk silage, and kinetic parameters for this model were developed by the Arrhenius equation. The activation energies for hemicellulose hydrolysis in control and acid silage were 44.3 kJ/mol and 3.1 kJ/mol, respectively.更多还原