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生物质微波预处理过程研究及连续反应器研制
Alternative TitleInvestigation on Microwave Pretreatment Process of Biomass and Design of Continuous Microwave Reactor
彭华栋
Subtype硕士
Thesis Advisor徐建
2013-04-01
Degree Grantor中国科学院研究生院
Degree Discipline生物工程
Keyword生物质预处理   微波   球磨   反应器设计   技术经济分析
Abstract在生物质预处理技术中,微波因其具有热效率高、渗透能力强、方便和易操作等特点而引起了广大科研人员的关注。本研究则从以下几个方面阐述微波技术应用于生物质预处理的高效性和可行性。 首先以结构简单,成份单一的微晶纤维素(MCC)为原料,考察了四种不同尺寸的MCC在微波和/或碱预处理前后的固形物回率率(Rs),颗粒尺寸(Particle size),结晶度(CrI),微晶尺寸(Sc)和比表面积(SSA)的变化。结果表明高浓度的碱或高温是溶解或降解纤维素的必要条件。碱处理可适当降低CrI、Sc,增加SSA、酶解速率和发酵速率,且其作用强度要高于微波的作用强度。微波联合碱处理的累积强度会高于单独碱或单独微波作用的强度。SSA与酶解速率正相关,而物料尺寸、CrI、Sc与酶解速率负相关。底物的结构差异对发酵所造成的影响在经适宜强度的预处理后,会在一定程度上被消除,且尺寸和预处理条件在生物转化过程中体现出来的重要性会随着反应时间变化。 其次,通过结合预处理过程中生物质结构参数的变化与生物转化效率之间的偶联关系,开发了一种新颖、环境有好、高效的球磨耦合微波的生物质预处理工艺。在该预处理过程中,没有添加任何化学试剂。经球磨/微波预处理后的MCC的酶解试验表明,球磨1 h、微波20 min是较理想的预处理条件,与球磨3 h(BM3)、球磨6 h(BM6)相比,该条件能在分别降低能耗54.8%,77.40%的前提下,产生相同或更多产量的葡萄糖。 然后,基于实验室现有的批次MCR-3微波化学反应器,研制了一台生物质微波连续预处理反应器,其设计处理能力为5 kg/h。该设备具有功率连续线性可调,传质、传热效果好,智能化程度较高,可实现连续操作等优点。采用响应面分析方法中的中心组合设计方法(CCD)实验设计方法进行条件优化,验证了该反应器的处理效果,最优的预处理条件为:功率:4.50 kW,时间:30 min,NaOH:3.50%。在此条件下,木素质去除率、葡萄糖产量(g/100 g 干重(DM))和乙醇产量(g/100 g DM)实际测得的值分别为:54.76%,62.60,31.89。与未处理的原料相比,葡萄糖产量与乙醇产量分别提高了4.37,3.88倍。扫描电镜(SEM)分析表明,玉米秸秆经微波加碱预处理后,玉米秸秆的形貌结构遭到破坏,增加了物料对纤维素酶的可及性。FTIR分析发现,木质素得到有效地去除,其纤维素组分中的结晶结构发生改变,木质素、纤维素等关键组份的特征官能团的含量也发生了改变。此外,验证了固形物回收率可以作为预测预处理后的生物质生物转化潜力的一个指标。 最后探讨了微波连续预处理玉米秸秆生产燃料乙醇的方案的可行性。基于微波预处理技术年产100 t燃料乙醇的项目投资回收期为9.30年,益本比大于1,内部收益率大于16.44%,产品成本为7200元/t。而在同样的国家补贴情况下,玉米秸秆未经处理直接生产燃料乙醇的方案由于由于其投资回收期无限长(远大于15年),不存在内部收益率,累计净现值一直为负等而导致其不具有可行性。因此,微波预处理技术有一定的可行性和商业价值。此外,经济敏感性分析表明,国家补贴、电价、NaOH价格、玉米秸秆价格等因素的波动对燃料乙醇的生产成本和项目的利润影响较大。 本论文研究工作中的相关数据和理论揭示了微波预处理过程中生物质结构变化的规律及其与生物转化之间的偶联关系,尝试了生物质微波连续预处理反应器的研制及条件优化,探讨了微波预处理玉米秸秆生产燃料乙醇工艺的技术经济可行性,这些将为微波技术在生物质能应用行业奠定基础,有利于推动相应工艺进一步工业放大。
Other AbstractAmong the exsiting biomass pretreatment technologies, microwave irradition arouses more and more concerns due to its high thermal efficiency, strong irradiation and permeability capacity, convenient, easy operation, etc. The aim of the present study is to elaborate the effectiveness and feasibility of microwave pretreatment on biomass in the following aspects: (1) The variation on solid recovery rate (Rs), particle size, crystalline index (CrI), average size of crystal (Sc) and the specific surface area (SSA) of the four different sizes of microcrystalline cellulose (MCC) were investigated in the process of microwave/alkali pretreatment. The results indicated that high concentration of alkali or high temperature were necessary to dissolve or decompose the cellulose. Alkali treatment was found to be superior to single microwave pretreatment in decreasing the CrI/Sc and increasing SSA. The combination of microwave and alkali pretreatment was much stronger than that of single alkali or microwave. The SSA had a positive effect on the enzymatic hydrolysis rate, while the particle size, CrI and Sc showed negative. The effect of the structure differences of the feedstocks on the fermentation efficiency was eliminated after the appropriate pretreatments. (2) A novel, environment-friendly, high-efficient ball milling (BM) pretreatment combined with microwave irradiation (MWI) was developed. The potential of enzymatic hydrolysis of MCC pretreated by BM-MWI showed that BM for 1 h, followed by MWI for 20 min was an optimal pretreatment condition. Compared to BM3, BM6, the energy consumption of the BM-MWI was decreased by 54.8%, 77.40% with the similar amount of glucose produced. (3) Based on the bench scale microwave reactor (MCR-3), a continuous reactor with the pretreatment capacity of 5 kg/h was inventeded which has the following advantages: continuous operation with power adjusted linearly between 0 kW and 6 kW, high-effective in heat transferand mass transfer, highly intelligent etc. The central composite design (CCD) within response surface method (RSM) was used to optimize the pretreatment condition. The obtained optimal condition was: 4.5 kW; 30 min; NaOH ( 3.50%, w/w). The actual measured lignin removal rate, glucose production (g/100 g DM) and ethanol production (g/100 g DM) were 54.76%, 62.60, 31.89, respectively. Compared with that of raw corn straw, glucose and ethanol production were improved by 4.37 and 3.88 times, respectively. The SEM analysis showed that the morphology of corn straw was destroyed dramatically when pretreated by the combination of microwave and alkali. The analysis of FTIR showed that the lignin was removed effectively and the content of special functional groups within lignin and cellulose was changed. In addition, the crystalline structure was also found to be changed by FTIR. By correlating solid recovery rate with glucose and ethanol yield, it was found that the solid recovery rate could be used as an indicator to predict the bioconversion potential of the pretreated biomass. (4) The tech-economical feasibility of bioethanol production (100 t/a) from corn stover pretreated by microwave was analyzed. With the public subsidy in the bioethanol plant using MWI pretreatment, the pay back period of investment (T) was 9.30 years; benefit-cost ratio (B/C) was greater than 1; the internal ratio of return (IRR) was 16.44%; the bioethanol cost was 7200¥/t. While for the plant using untreated corn straw, the tech-economical analysis showed not to be promising even with the same public subsidy: the T was infinite, greater than 15 years; the IRR was not exist; the accumulative total net present value was kept negative within 15 years. Thus, the microwave pretreatment technology is feasible and of commercial value. Besides, the analysis of economic sensitivity showed that the cost of the bioethanol and benefits of the projects was affected much by the public subsidy, the price of electricity, NaOH, corn straw, etc. This study revealed the relationship between the varitaion of biomass structures in the microwave pretreatment process and its bioconversion potential; tried to develop an biomass microwave continuous pretreatment reactor and optimize the pretreatment condition; discussed the tech-economic feasibility of the program involved the production of bioethanol using the corn straw pretreated by microwave. The results obtained in this thesis will provide the basic theoretical knowledge and practical experience in biomass refinery, especially in the innovation of pretreatment technologies.
Pages107
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8380
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
彭华栋. 生物质微波预处理过程研究及连续反应器研制[D]. 中国科学院研究生院,2013.
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