【作者】 宋籽霖；

【导师】 杨改河；

【作者基本信息】 西北农林科技大学 ， 生态学， 2013， 博士

【摘要】 随着农村环境污染和能源短缺问题的日益严重，户用沼气的发展受到人们的广泛关注，成为了我国新农村建设的重要组成部分和农村能源发展的主要内容。大力开发生物质能源，利用农业废弃物进行厌氧发酵生产沼气，是解决我国农村能源紧张和环境污染问题的关键。本研究对比分析了户用沼气和大中型沼气工程在我国农村的适用性，并针对因规模化养殖代替散养模式造成的户用沼气发酵原料不足的问题，提出了通过化学预处理提高秸秆沼气化利用效率的方法，重点研究了不同预处理剂、预处理时间和预处理温度对水稻、玉米和小麦三种秸秆厌氧发酵的影响，并对处理效果较好的酸、碱试剂进行工艺优化，得出最佳预处理参数，在此基础上，对两种预处理方法的沼气经济实用性进行了分析，旨在为我国农村秸秆沼气高效利用提供理论依据和数据支持。研究得到如下结论：1.选用双氧水（H₂O₂）、醋酸（CH₃COOH）、硫酸（H₂SO₄）和盐酸（HCl）对水稻、玉米、小麦三种秸秆进行厌氧消化预处理，结果表明，不同浓度的酸预处理剂对秸秆的纤维素含量、沼气产量以及产气效率影响较大。其中，H₂O₂和CH₃COOH预处理的最佳浓度为3%，HCl和H₂SO₄的最佳浓度为2%。四种试剂中，3%H₂O₂的预处理效果最好，产气效率分别达315、320和285mL/g VS。2.选用氢氧化钠（NaOH）、氢氧化钙（Ca（OH）2）和氨水（NH₃·H₂O）对水稻、玉米、小麦三种秸秆进行预处理，结果表明，不同浓度的碱预处理剂对秸秆的纤维素含量、沼气产量以及产气效率影响较大。其中，8%Ca（OH）2的预处理效果最好，产气效率分别达325、285和320mL/g VS。3.不同预处理时间对秸秆厌氧发酵的影响显著。其中，H₂O₂、CH₃COOH、HCl、H₂SO₄和NaOH对纤维素和半纤维素的降解程度随预处理时间的延长而增加，Ca（OH）2和NH₃H₂O则在预处理1天和4天后纤维素含量无显著变化，但预处理7天后，其含量显著降低。H₂O₂、CH₃COOH、Ca（OH）2和NH₃·H₂O预处理的秸秆产气效率均随预处理时间的增加而升高，HCl和H₂SO₄预处理的产气效率则在预处理4天时最高。4.不同预处理温度对秸秆的厌氧发酵具有一定影响。在15℃、35℃和55℃预处理中，H₂O₂、CH₃COOH、Ca（OH）2和NH₃H₂O在15℃和35℃下纤维素和半纤维素含量以及产气效率无显著差异，而在55℃下纤维素和半纤维素含量显著降低，产气效率显著升高。HCl、H₂SO₄和NaOH预处理的纤维素和半纤维素含量均随预处理温度的升高而降低，产气效率随温度的升高而增加。5.以水稻秸秆为原料，对H₂O₂和Ca（OH）2的预处理过程进行优化。选择预处理时间、预处理剂浓度和接种物量3个参数分析两种试剂对水稻秸秆厌氧发酵产气特性的影响。结果表明，H₂O₂的最佳处理参数为：6.18天（预处理时间）、2.68%（浓度）以及1.08（接种物比），在最优条件下沼气产量理论值为287.9mL/g VS；Ca（OH）2的最佳处理参数为：5.89天（预处理时间）、9.81%（浓度）以及45.12%（接种物量），在最优条件下产气量理论值为217.8mL/g VS。H₂O₂和Ca（OH）2优化模型的决定系数（R2）分别为95.2%和96.0%，表明两个产气模型利用试验值对实际厌氧发酵进行预测具有较高的可信度。为验证优化方案的可信度，分别采用两种预处理剂在预测的最优条件下进行发酵试验，结果表明，H₂O₂预处理后产气量达到290.3mL/gVS，Ca（OH）2预处理达到225.3mL/g VS，较对照分别增加了88.0%和73.3%。因此，H₂O₂和Ca（OH）2可作为秸秆厌氧发酵的预处理剂，能够有效提高秸秆的能量转化效率。6.水稻秸秆经H₂O₂和Ca（OH）2处理后分别与牛粪、鸡粪混合发酵，结果表明，预处理能够显著提高秸秆混合发酵的沼气产量和产气效率。与未处理的秸秆相比，预处理后的秸秆混合发酵产气量增加了29%-43%，产气效率增加了24%-31%。因此，采用H₂O₂和Ca（OH）2预处理提高厌氧发酵效率，不仅适用于秸秆单一原料，同样也适用于混合原料。7.化学预处理秸秆厌氧发酵的经济实用性评价表明，与使用原煤作为燃料相比，使用H₂O₂和Ca（OH）2预处理秸秆进行厌氧发酵每年每户可节约311.41元和312.4元。对秸秆沼气利用潜力和温室气体减排进行估算，我国每年产生的农作物秸秆直接焚烧会产生8.85×108t CO₂，若将这些秸秆全部进行户用沼气发酵，每年可生产12.97×106万m3的沼气，同时可减少6.70×108t CO₂的排放。化学预处理技术不仅能够提高秸秆的能量转化效率，而且秸秆沼气化利用可有效减少温室气体的排放，因此，应推广化学预处理技术在农村户用沼气中的应用，从而达到秸秆的沼气化高效利用。更多还原

【Abstract】 With the deterioration of rural envirionment pollution and energy shortage, thedevelopment of rural household biogas has attracted the people’s attention. It has been animportant part of new countryside construction and main content of rural energy developmentin China. The development of biomass energy and the utilization of agriculture wastes foranaerobic biogas production are important for solving the energy crisis and environmentpollution in rural China. The present study compared the characteristics of household biogasand large-medium biogas plants in rural China, and also put forward the chemicalpretreatment for straw to improve its biodegradability in order to solve the problem ofhousehold biogas raw material shortage caused by large-scale farming. The effect of differentacid and alkaline chemicals pretreatments on the anaerobic digestion of rice straw, wheatstraw and corn straw was investigated, and the effective acid and alkaline pretreatmentschemicals was optimized to obtain the optimal operation parameters. On the basis ofabovement, the economic-practical application of two chemical pretreatment was analyzed toprovide the theoretical basis and data support for the efficient utilization of straw bigasficationin rual China. The main results are as follows:1. In the present study, the effect of rice straw, corn straw and wheat straw pretreated byhydrogen peroxide （H₂O₂）, hydrochloric acid （HCl）, sulfuric acid （H₂SO₄） and ethylic acid（CH₃COOH） on the biogasfication performance was investigated. The results showed the acidpretreatements with different concentration have a different effect on the the cellulose content,biogas yield and biogas efficiency of straws. The optimal treatment of H₂O₂and CH₃COOHfor bigas production was3%, and the optimal treatment of HCl and H₂SO₄was4%. Amongthe four pretreatments, the optimal treatment biogas production was2%H₂O₂, which yieldedthe biogas of315、320and285mL/g VS for rice straw, wheat straw and corn strawrespectively.2. The effect of rice straw, corn straw and wheat straw pretreated by sodium hydroxide（NaOH）, calcium hydroxide （Ca（OH）2） and aqueous ammonia （NH₃·H₂O） on thebiogasfication performance was investigated. The result showed the the alkalinepretreatements with different concentration have a different effect on the the cellulose content,biogas yield and biogas efficiency of straws. Among the three pretreatments, the optimal treatment for biogas production was8%Ca（OH）2,which yielded the biogas of325,285and320mL/g VS for rice straw, wheat straw and corn straw respectively.3. Pretreatment time has a significant effect on the anaerobic digestion of straws.Degradation of H₂O₂、CH₃COOH、HCl、H₂SO₄and NaOH on the cellulose and hemicelluloseincreased with the increase of pretreatment time. There was no significant difference between1d and4d pretreatment on the cellulose content for Ca（OH）2and NH₃H₂O, while the7dresulted in a great decrease on it. The biogas efficiency of straw pretreated by H₂O₂,CH₃COOH, Ca（OH）2and NH₃·H₂O increased with the increase of pretreatment time whilepretreated by HCL and H₂SO₄have the higest value in the4d pretreatment.4. Pretreatment temperature can affect the anaerobic digestion of straw. amongthe15℃,35℃and55℃pretreatment, no significant difference was found between the15℃and35℃on the cellulose, hemicellulose and biogas efficiency of straw pretreated byH₂O₂, CH₃COOH, Ca（OH）2and NH₃H₂O, while at the55℃, the cellulose, hemicellulosecontents greatly decreased and biogas efficiency significantly enhanced. The cellulose andhemicellulose contents of straw pretreated by HCl, H₂SO₄and NaOH significantly decreasedand its biogas efficiency increased with the rise of the pretreatment temperature.5. The pretreatment time, chemicals concentration and inoculum amount of wereselected as parameters to investigate the effect of H₂O₂and Ca（OH）2on rice strawbiggasfication. The result showed the the optimal conditions of H₂O₂treatment foranaerobic digestion were6.18d treatment time,2.68%H₂O₂and1.08inoculum ratio,which yielded the max theoretical methane of287.90mL/g VS. The optimal conditions ofCa（OH）2treatment for anaerobic digestion were5.89d treatment time,9.81%H₂O₂and45.12%inoculum content, which yielded the max theoretical methane of217.82mL/gVS. The determination coefficient of H₂O₂and Ca（OH）2optimal model are95.2%and96%, this indicated two optimal models to predict the the actual anaerobic fermentationprocess have high credibility. To verify the the incredibility of predicted resutls, H₂O₂andCa（OH）2pretreatment was used for straw anaerobic digestion at the optimal conditions. Theresult showed the methane yield of rice straw pretreated by H₂O₂and Ca（OH）2were90.36mL/gVS and225.3mL/g VS, respectively, which was increased by88%and73.3%,respectively, compard to the untreated rice straw. In conclusion, H₂O₂and Ca（OH）2can usedas pretreatment for rice straw biogasifciaton, and both can effectively improve the energyconversion efficiency of straw.6. The anaerobic digestion of cow manure and rice straw mixture was conducted toinvestigate the effect of pretreatment on the mixture anaerobic digestion. The results showedthat the pretreatment on straw after can significantly improve the biogas yield and biogas yield efficiency. Compared with the straw without pretreatment, the biogas yield and biogasyield efficiency of pretreated straw mixture was increased by29%-43%and24%-31%. Thus,H₂O₂and Ca（OH）2pretreatment is an effective method for single material and mixturematerial to improve the anaerobic digestion.7. The economic practicability analysis of chemical pretreatment for straw anaerobicdigestion indicated that compared with the use of raw coal for fuel, the use of H₂O₂andCa（OH）2as pretreatment for straw anaerobic digestion can save311.4and312.4Yuan peryear per household, respectively. The evaluation of straw biogas potential and the estimationof greenhouse gas emission reduction showed that the direct buring of straw will annuallycause the8.85×10⁸t CO₂in China, if these straws was all used for anaerobic digestion, notonly12.97×10¹¹m³biogas can be produced per year, but the reduction of6.70×108t CO₂emission can be made. Considering the advantage of chemical pretreatments for stawanaerobic digestion in energy conversion efficiency improvement and the greenhouse gasemission reduction, our study recommend that chemical pretreatment technology should bewidely promoted for straw anaerobic digestion in the rural househould biogas development.更多还原