【作者】 韩伟；

【导师】 李永峰；

【作者基本信息】 东北林业大学 ， 生态学， 2012， 博士

【摘要】 由于传统化石能源的过度使用导致一系列的环境污染问题,因此,人们迫切寻求可以实现友好环境的可替代能源。氢能具有清洁、高效、可再生和不产生有害副产物等优点,已经引起了世界范围内的广泛关注。厌氧发酵生物制氢技术一方面可以处理有机废弃物(废水)减少对环境的危害,另一方面还可以利用有机废弃物(废水)而产生清洁能源(氢气)而更具发展前景。悬浮生长系统和附着生长系统是目前最为常用的厌氧发酵生物制氢系统,本文在研究了上述两种制氢系统的建立与运行后,提出一种新型的连续流混合固定化污泥反应器(CMISR)发酵制氢,以期为厌氧发酵生物制氢技术的产业化应用提供基础的技术和理论依据。本文利用糖蜜废水作为发酵底物,以连续流搅拌槽式反应器(CSTR)作为反应装置,采用经好氧预处理污泥作为接种污泥,探讨了悬浮生长制氢系统的建立及运行特性。研究表明,当反应器温度控制在35℃,水力停留时间(HRT)为6h时,pH值和ORP分别稳定在3.7～4.57和-230～-464mV之间,反应器运行35d后可实现稳定的乙醇型发酵。此时,液相末端发酵产物以乙醇和乙酸为主,占液相末端发酵产物总量的83.55%。发酵气体中氢气含量及产氢量分别为30%～45%和1.53m3/m3d。此外,氢气和乙醇是具有发展前景的生物燃料,被认为是化石能源的可替代能源。在上述系统达到稳定乙醇型发酵基础上,探讨了不同有机负荷(OLR)对发酵法生物制氢和生物制乙醇的影响。结果表明,当OLR在8-24kg/m3d范围内变化时,产氢速率和产乙醇速率随着OLR的提高而增加,并且在OLR为24kg/m3d时分别得到最佳的产氢速率(12.4mmol/hl)和产乙醇速率(20.27mmol/hl).然而,当OLR进一步提高到32kg/m3d时,产氢速率和产乙醇速率却呈现下降趋势。在液相末端发酵产物中乙醇含量占31%-59%,为主要的代谢产物。线性回归方程表明产乙醇速率(y)和产氢速率(x)成正比关系,方程式为y=0.5431x+1.6816(r2=0.7617)。基于氢气和乙醇的热量值,总产能速率被用来衡量整个发酵系统的产能效率,在OLR为24kg/m3d时发酵系统得到最大产能速率31.23kJ/hl。采用连续流搅拌槽式反应器(Continuous flow Stirred-Tank Reactor, CSTR)作为反应装置,以颗粒活性炭为生物载体,利用糖蜜废水厌氧发酵生物制氢。研究表明,在污泥接种量(以VSS计)为17.74g/L,温度为35℃,水力停留时间(HRT)为6h,控制有机负荷(OLR)在8kgCOD/(m3d)-24kgCOD/(m3d)范围内,连续流附着生长制氢系统可在22d内达到连续稳定产氢。此时,系统pH值为4.28,氧化还原电位(ORP)在-420mV左右,产气量和产氢量分别为10.6L/d和5.9L/d左右。液相末端发酵产物中,乙醇和乙酸的含量占挥发酸总量的89%,为典型的乙醇型发酵。连续流附着生长制氢系统表现出较高的抗负荷冲击能力和一定的耐低pH值能力,颗粒活性炭可作为固定化活性污泥发酵制氢载体。同时,还考察了有机负荷(OLR)对连续流附着生长制氢系统发酵制取氢气和乙醇的影响。研究表明,H2和乙醇的产率随有机负荷的增加(8-24kg/m3d)而提高。最高的产氢率(10.74mmol/hl)和乙醇产率(11.72mmol/hl)都是在OLR=24kg/m3d的运行条件下得到的。乙醇为主要的液相发酵产物,其含量占总的液相代谢产物的38.3%-48.9%。线性方程表明了乙醇产率和H2产率呈正相关,可表示为y=1.5365x-5.054(r2=0.9751)(y:乙醇产量；x：氢气产量)。产能效率以H2和乙醇的热值来计算,从而评估CSTR反应系统的整体产能效率。当OLR为24kg/m3d时,反应系统得到最大的产能效率为19.08kJ/hl。此外,液相代谢产物乙醇和乙酸的产量能够影响厌氧发酵系统的产氢效率,当乙醇和乙酸的比例接近1得到最大产氢速率,分析认为,这是由于NAD+/(NADH+H+的调整)影响发酵代谢途径造成的。利用活性炭作为载体,糖蜜废水为发酵底物,采用新型连续流混合固定污泥反应器(Continuous Mixed Immobilized Sludge Reactor, CMISR)作为反应装置,厌氧发酵生物制氢。研究表明,当CMISR反应器控制进水COD浓度为2000～6000mg/L,水力停留时间(HRT)为6h,温度为35℃,pH值和氧化还原电位(ORP)分别在4.06～4.28和-416～-434mV变化时,CMISR反应器在运行40d后可形成稳定的乙醇型发酵,此时的乙醇和乙酸含量占总液相发酵代谢产物的89.3%。氢气含量和COD去除率分别为46.6%和13%。此外,考察了有机负荷(OLR)变化对CMISR产氢效能的影响。结果表明,当CMISR反应器中OLR为32kg/m3d时,系统可得到最大产氢速率(the maximum hydrogen production rate)12.51mmol/hL; OLR为16kg/m3d时,系统可得到最佳底物转化产氢量(the maximum hydrogen yield by substrate consumed)130.57mmol/mol。由此可以看出,连续流混合固定化污泥反应器(CMISR)作为有发展前景的固定化系统,而用作厌氧发酵生物制氢。更多还原

【Abstract】 Environmental pollution due to the burning of fossil fuels makes it necessary to find alternative energy sources that are environmentally friendly. A great deal of attention is being paid to the usage of hydrogen (H2), a sustainable energy carrier which is clean, efficient and renewable; moreover it does not generate any toxic by-products. Through biological processing, hydrogen can be produced through dark fermentation from organic wastes. Additionally, there is also a need to dispose of human-derived wastes in an environmentally friendly manner, using wastes to produce hydrogen offers a possible alternative to current waste-disposal methods. Therefore, fermentative hydrogen production has attracted increasing attention in recent years. The suspended cell system and attached cell system have been frequently used for fermentative hydrogen production. Based on the above two systems for biohydrogen production, it was developed a novel continuous mixed immobilized sludge reactor (CMISR) for hydrogen production, so as to provide basic technical and theoretical foundation for industrial hydrogen production.A study of biohydrogen production was performed in a continous flow anaerobic fermentation reactor. Under the operational conditions of the inoculants, batch experiments were carried out to convert molasses wastewater pretreated by using anaerobic mixed bacteria at35℃, when the pH value, chemical oxygen demand (COD) and oxidation-reduction potential (ORP) of the efflunt ranged from3.7to4.57,1980to6407mg/L, and-230to-464mV, respectively. Soluble metabolites were predominated by acetate and ethanol, with smaller quantities of butyrate, valerate and propionate. The total amount of ethanol and acetate accounting for83.55%of the total terminal products after35days operation and stable ethanol-type fermentation was formed. The hydrogen volume content was estimated to be30-45%of the total biogas and the biogas was free of methane throughout the study. Furthermore, together with the corresponding degradation efficiencies and metabolites were compared. The rate of COD removal reached at a peak values of40.91%and stable at a value about20%. A mixed culture fermentation in a CSTR reactor system under the operational conditional was employed to convert this substrate into hydrogen with a yield of1.53m3/m3.d. Hydrogen generation using the fermentation process is possible with various type of wastewater using either mixed or pure cultures. This CSTR system showed that mixed microbial is an a promising high-efficient bioprocess for enhancing the hydrogen production from high-strength wasterwater. Moreover, hydrogen and ethanol are promising biofuels and have great potential to become alternatives to fossil fuels. The influence of organic loading rates (OLRs) on the production of fermentative hydrogen and ethanol were also investigated in a continuous stirred tank reactor (CSTR) from fermentation using molasses as substrate. Four OLRs were examined, ranging from8to32kg/m3d. The H2and ethanol production rate in CSTR initially increased with increasing OLR (from8-24kg/m3d). The highest H2production rate (12.4mmol/hl) and ethanol production rate (20.27mmol/hl) were obtained in CSTR both operated at OLR=24kg/m3d. However, the H2and ethanol production rate tended to decrease with an increase of OLR to32kg/m3d. The liquid fermentation products were dominated by ethanol, accounting for31%～59%of total soluble metabolities. Linear regression results show that ethanol production rate (y) and H2production rate (x) were proportionately correlated which can be expressed as y=0.5431x+1.6816(r2=0.7617). The total energy conversion rate based on the heat values of H2and ethanol was calculated to assess the overall efficiency of energy conversion rate. The best energy conversion rate was31.23kJ/hl, occurred at OLR=24kg/m3d.A continuous stirred-tank reactor (CSTR) process with granular activated carbon (GAC) was developed for fermentation hydrogen production from molasses-containing wastewater by mixed microbial cultures. Operation at35℃, an initial biomass of17.74g/L and hydraulic retention time (HRT) of6h, the CSTR reactor presented a continuous hydrogen production ability of5.9L/d and the biogas was free of methane throughout the experiment. Dissolved fermentation products were predominated by ethanol and acetate acid, with smaller quantities of propionic acid, butyric acid and valeric acid. It was found that GAC could make the immobilized system durable and stable in response to organic load impacting and low pH value. When the organic loading rate (OLR) ranged from8kgCOD/(m3d) to4kgCOD/(m3d), stable ethanol-type fermentation was formed, and the ethanol and acetate concentrations account for89%of the total liquid products. Moreover, the effects of organic loading rates (OLRs) on fermentative productions of hydrogen and ethanol were also investigated in a continuous stirred tank reactor (CSTR) with attached-sludge using molasses as substrate. The CSTR reactor with attached-sludge was operated under different OLRs, ranging from8to24kg/m3d. The H2and ethanol production rate essentially increased with increasing OLR. The highest H2production rate (10.74mmol/hl) and ethanol production rate (11.72mmol/hl) were obtained both operating at OLR=24kg/m3d. Linear regression results show that ethanol production rate (y) and H2production rate (x) was proportionately correlated and can be expressed as y=1.5365x-5.054(r2=0.9751). The best energy generation rate was19.08kJ/hl, occurred at OLR=24kg/m3d. In addition, the hydrogen yield was affected by the presence of ethanol and acetic acid in the liquid phase, and the maximum hydrogen production rate occurred while the ratio of ethanol to acetic acid was close to1.A novel continuous mixed immobilized sludge reactor (CMISR) containing activated carbon as support carrier was used for fermentative hydrogen production from molasses wastewater. When the CMISR system operated at the conditions of influent COD of2000-6000 mg/L, hydraulic retention time (HRT) of6h and temperature of35℃, stable ethanol type fermentation was formed after40days operation. The H2content in biogas and chemical oxygen demand (COD) removal were estimated to be46.6%and13%, respectively. The effects of organic loading rates (OLRs) on the CMISR hydrogen production system were also investigated. It was found that the maximum hydrogen production rate of12.51mmol/hL was obtained at OLR of32kg/m3d and the maximum hydrogen yield by substrate consumed of130.57mmol/mol happened at OLR of16kg/m3d. Therefore, the continuous mixed immobilized sludge reactor (CMISR) could be a promising immobilized system for fermentative hydrogen production.更多还原