干式厌氧生物转化.doc

【精品文档】如有侵权，请联系网站删除，仅供学习与交流干式厌氧生物转化.精品文档.Bio-energy recovery from high-solid organic substrates by dry anaerobic bio-conversion processes: a review通过干式厌氧生物转化过程从固体含量较高的有机基质中回收生物能源：综述SEVEN PARTS这篇论文主要分为七个部分1 Overview 1概述2 Substrate characterization for D-AnBioC processes2 干式厌氧生物转化系统的底物特性3 Reactor configurations and operational sequences for D-AnBioC processes3干式厌氧生物转化过程的反应器的配置和操作顺序4 Techniques to enhance the bio-energy recovery by D-AnBioC process 4 通过干式厌氧生物转化的过程来提高生物能源回收的技术5Factors affecting D-AnBioC efficiency 5干式厌氧生物转化效率的影响因素6 Digested residue management from D-AnBioC process6干式厌氧生物转化过程中消化残余物的管理7 Energy and economic factors associated with D-AnBioC process7 与干式厌氧生物转化过程相关的能源及经济因素8 Summary and future research directions8 总结及未来研究方向1 OverviewCurrently, anaerobic bio-conversion (AnBioC) of organic substrates (OS) is considered as the most common biotechnological solution due to its economical and energy recovery benefits.目前，由于固体含量高的有机基质的干厌氧生物转化在经济和能源回收方面的优势，使其成为了最常见的生物技术解决方案。In brief, OS are biochemically converted into bio-methane (CH4) under anaerobic conditions by the major groups of bacteria/archaea, such as hydrolyzers, acidogens, acetogens and methanogens.总之，在厌氧条件下，有机基质（OS）被一群主要为细菌/古生菌的菌群通过生化反应生成甲烷，主要的菌群如水解菌、产酸菌、产乙酸菌和产甲烷菌。2 Substrate characterization for D-AnBioC processes2 干式厌氧生物转化系统的底物特性The D-AnBioC system is mainly designed to treat OS from four different sources, including, agriculture waste, community waste, animal waste and industrial waste.干式厌氧生物转化系统主要是设计处理四个不同来源的有机基质（OS），包括农业废物、社区垃圾、动物废物和工业废物。Thus, TS of the OS substrates along with physicochemical properties of the substrates are to be mainly considered for the D-AnBioC process to control overall CH4 yield.因此，底物的有机基质（OS）中的总固体量连同底物的物理化学性质都被认为是干式厌氧生物转化过程中控制甲烷产生的主要因素。It was noted that the TS of OS influenced the following parameters: rheological properties and viscosity of the reactor contents, fluid dynamics, clogging and solid sedimentation that can directly affect the overall mass transfer rates within the bioreactors.于是得出，有机基质（OS）的总固体含量会影响以下几种参数：流变学特性和反应器内的物质的粘度，流体动力学，堵塞，固体沉降会直接影响整个生物反应器中的传质速率。However, the D-AnBioC systems seem to be more economical than W-AnBioC in treating OS because of the following: a smaller reactor volume, no internal mixing arrangement for continuous mixing (in some cases), can handle a variety of feed stocks, and can attain maximum CH4 yield.然而，在处理有机基质（OS）上，干式厌氧生物转化系统比湿式厌氧生物转化系统更经济，原因如下：它的反应器容积更小，内部没有用于连续混合的混合装置（在某些情况下），能够处理各种各样的原料，能够获得最大的甲烷产量。3 Reactor configurations and operational sequences for D-AnBioC processes3干式厌氧生物转化过程的反应器的配置和操作顺序A number of commercial plants, pilot plants and proto-type bio-reactors to treat OS have been developed using the D-AnBioC processes. Four major considerations with the bio-reactor design for continuous operations include:很多商业性质的处理厂，中试处理厂和原生物反应器在处理有机基质（OS）上已经开始开发利用干式厌氧生物转化过程。四个连续运行的生物反应器的设计考虑的主要因素包括：Organic Loading Rate (OLR)（1）有机负荷率（OLR）有机负荷率（OLR）是测量厌氧系统的生物转化能力的一种方法。Solid/Digestate Retention Time (SRT)（2）固体/沼渣的保留时间（SRT）SRT是在单位时间内流入的体积和有机基质（OS）流出的体积比。是固体停留在消化池中的平均停留时间。Hydraulic Retention Time (HRT)（3）水利停留时间（HRT） CH4 Yield（4）甲烷产量甲烷产量最大化是最重要的生物反应器设计参数，并且在操作运行的条件中起着关键的作用。3.1 Microbial dynamics and metabolite distribution with respect to bio-reactor design3.1微生物动力学和代谢产物的分布与生物反应器设计In general, four major classified groups of microorganisms are involved in the bioconversion of OS into CH4, as depicted in Fig. 3.一般情况下，四大类的微生物参与生物将有机基质（OS）转化成甲烷，如图3所示。It has been reported that the hydrolysis/acidogenesis microorganisms have a faster growth rate (30 min) resulting in more than 90 % in total digester population during the initial stages. 有关报道表明，水解/酸化作用使微生物的增长速度更快（30分钟），从而导致在初始阶段产生的沼气比例大于90。As a first step in the AnBioC process, hydrolysis/acidogenesis of complex organic substrates produce VFAs, amino acids, alcohol, carbon dioxide (gas phase) and hydrogen (gas and liquid phase) within the system. Among the different acids produced, acetic acid will be more abundant than other acids like formic, propionic, valeric and butyric acids. Due to the accumulation of these organic acids, the system pH and ORP values will be 4.5 ± 0.5 and ±50 mV (Eh), respectively (Gerardi 2003).作为干式厌氧生物转化过程的第一步，水解/酸化过程的有机底物在系统中产生复杂的物质如挥发性脂肪酸，氨基酸，醇，二氧化碳（气相）和氢气（气相和液相）。在不同的酸产生过程中，乙酸会比其他酸，如甲酸，丙酸，戊酸和丁酸更加丰富。由于这些有机酸的积累，该系统的pH和氧化还原电位（ORP）分别为< 4.5 ±0.5和± 50mV（Eh）（Gerard,2003）。In the second step, that is, the acidogenesis/ acetogenesis process, products like acetate, hydrogen and less amounts of CH4 are formed under a pH range of 3.56.0 and ORP -170 ± 50 mV (Eh) (Gerardi 2003). Homoacetogen, a special group of bacteria, involved in the utilization of H2 and CO2 during this stage, produces acetate via the Wood-Ljungdahl pathway. 在第二步骤中，也就是酸化/产乙酸过程，产物如乙酸盐，氢和少量的CH4，形成的pH值范围为3.5-6.0和氧化还原电位(ORP)为-170 ±50mV（Eh）（Gerard,2003）。同型产乙酸菌是一群特殊的细菌，在这个阶段中涉及H2和CO2的利用率，通过Wood-Ljungdahl途径产生醋酸。Also, acetogensis of propionic and butyric acids proceed under very low H2 partial pressure/ concentrations during the third stage (that is, acetogenesis) of anaerobic conversion. 同时，丙酸及丁酸的产酸菌产酸是在H2 分压/浓度非常低的情况下进行的，发生在厌氧转换期间的第三阶段 即，产酸。Followed by acetogenesis, acetoclastic methanogens which utilize acetate as a carbon source (Eq. 5), hydrogenotrophic methanogens which utilize hydrogen and carbon-dioxide (Eq. 6), and methylotrophic methanogens which utilize methyl alcohol (Eq. 7) produce CH4 during the last step. 随后，通过产乙酸菌，产甲烷菌（使用醋酸酯作为碳源（Eq.5），产氢产甲烷菌（利用氢气和二氧化碳（Eq.6），甲醇产甲烷菌（利用甲醇（Eq.7）在最后一步产生甲烷。4 Techniques to enhance the bio-energy recovery by D-AnBioC process4 通过干式厌氧生物转化的过程来提高生物能源回收的技术There are a number of techniques proposed in the literature to improve the bio-energy recovery from OS under D-AnBioC processes. Generally, all these techniques were used either alone or in combinations for the better performance of the bioreactor. The details are discussed below.有很多文献中提出提高有机基质（OS）的干式厌氧生物转化过程回收生物能源的技术。一般来说，所有这些技术单独使用或在生物反应器中结合使用以达到更好的性能。在下面进行详细地讨论。4.1Temperature4.1 温度Temperature is one technique to improve the efficiency of the system and reduce the overall SRT in D-AnBioC processes.温度在干式厌氧生物转化过程可以提高系统效率、减少整体的固体/沼渣的停留时间。Thermophilic temperatures convert organic acids at a faster rate, with higher CH4 production (2535 %) than the mesophilic system.高温系统比中温系统转换有机酸的速度更快，CH4的产量也更高（25-35）。Net energy gain of more than 5075 % was reported with the thermophilic D-AnBioC system (Zeshan et al. 2012).Zeshan等人在2012年曾报道在适温的干式厌氧生物转化系统中，净能量的收益超过50-75%。4.2Pre-treatment of substrates4.2 底物的预处理Generally, pre-treatment technologies were adopted to alter or remove these structural/compositional impediments to increase the yields of fermentable simple sugars/intended products in order to further process utilizations (Mosier et al. 2005).一般来说，预处理技术是通过改变或移除一些结构/成分障碍，增加可发酵单糖的产量/预期的产物，以进一步提高利用率的过程（Mosier等人，2005）。Specifically, any pretreatment technology is intended to: 预处理技术的目的：(1) free as much carbohydrates as possible into monomers; （1）使尽可能多的碳水化物尽可能转化成单体；(2) provide easy accessibility for bacterial or enzymatic action; （2）提供容易操作的细菌/酶促作用；(3) minimize sugar degradation and lignin solubilization;（3）减少糖降解和木质素的溶解； (4) be environmentally friendly and a less energy intensive process; （4）成为环境友好型和低能量密集型的过程；and (5) be a scalable, simple and robust system.（5）是一个可伸缩，简单的和强有力的系统。 Particle size affects the overall bioconversion efficiency and determines the digestate quality. Therefore, size reduction is an important pretreatment technique for D-AnBioC processes (Forster-Carneiro et al. 2008b; Guendouz et al.2010; Nizami and Murphy 2011; Zeshan et al. 2012) to obtain a uniform particulate size. This can improve the active surface area for faster enzymatic reactions. 但是采用干式厌氧生物转化系统处理有机基质（OS）时，粒子大小是一个重要的因素。粒子大小会影响整个生物的转化效率，并且决定消化的质量。因此，粉碎是干式厌氧生物转化过程中的一个重要的预处理技术，以获得尺寸均匀的颗粒（Forster-Carneiro等人，2008b；Guendouz等人，2010；Nizami和Murphy，2011；Zeshan等人，2012）。这可以提高颗粒活性的表面积，使酶促反应更快。The alkaline pre-treatment technique is most commonly reported.报道最多的是碱性预处理过程。Thermal and acid pretreatment methods are less explored with OS, especially for use in the D-AnBioC processes.用热和酸的预处理方法处理有机基质（OS）的研究较少，特别是干式厌氧生物转化的过程。Whereas, the biological pre-treatment of OS for the D-AnBioC process is less attempted due to major factors like: 然而，在干式厌氧生物转化过程中，用生物法对有机基质（OS）进行预处理的尝试较少，其主要因素有：(1) a longer retention time compared to physicochemical methods; （1）生物法与物理化学方法相比需要的保留时间更长；(2) the need to provide adequate environmental conditions; （2）生物法需要提供充分的环境条件；and (3) its cost effectiveness.（3）生物法的成本效益。4.3 Co-digestion4.3 共消化 The use of mono-substrate for D-AnBioC processes sometimes affect the overall process conversion due to nutrient limitations. 在干式厌氧生物转化过程中的采用纯培养基，由于营养条件的限制，有时会影响整个过程的转换。It would require treatment to provide an external nutrient supply throughout operations.这需要在整个过程中提供外部营养。The various mixing ratios of OS for co-digestion studies were considered more important and were expected to affect the overall microbial community distribution within the system.Liu等人在2009年也报道了不同有机基质（OS）的共消化（比率）可以提高消化动力学，但不能提高沼气潜力。Co-digestion of OS has important benefits, such as:用共消化的方法处理有机基质（OS）有非常重要的优势，比如： (1) reduced fugitive gas emissions; （1）减少挥发性气体的排放；(2) ability to manipulate the C/N ratio to improve process stability; （2）控制C / N的能力，以提高工艺的稳定性；(3)providing a balanced buffering capacity; （3）提供平衡的缓冲能力；(4) improved the rheological properties within the system; （4）改进的系统内的流变性能；(5) reduced external nutrient supply; （5）减少外部养分的供应；(6) minimized the effe cts of toxic or inhibitory compounds towards microbial community within the systems;（6）使毒性效应影响最小化或抑制化合物对系统内的微生物群落的影响； (7) improved the nutrient quality of the digested residue for land applications; （7）为土地的利用，改善消化剩余土地的营养质量；and (8) improved biogas yield.(8) 提高的沼气产量。4.4 Digester mixing and leachate exchange practices4.4 沼气池混合渗滤液交换的方法Due to the high-solid content within the digester, there is a chance for black pockets, or dead zone formations, during continuous operation under the D-AnBioC process. 在干式厌氧生物转化连续运行中，由于消化池内的固体含量高，容易形成黑口袋或死区。That is, the overall bioconversion process will be affected should there be aminimum biogas yield. 也就是说，整体的生物转化过程将受到影响，使产气量降到最低。This will result in digester failure.这将导致消化池出现故障。 To avoid such consequences, internal mixing arrangements, or even, the recirculation of digested residue, should be practiced. 为了避免这样的后果，内部应进行混合安排，甚至使消化残渣进行再循环。The use of mixing arrangements使用混合安排的优点：: (1) provides a homogenized environment; （1）提供了一个同质化的环境；(2) prevents stratification and formation of surface crust;（2）防止分层和表面地壳的形成； (3) improves contact between microbes and biodegradable particles; （ 3 ）增大了微生物和可生物降解的颗粒之间接触面积；(4) helps to release gas bubbles trapped inside air pockets;（4）有助于释放气穴里的气泡； (5) improves the diffusivity co-efficient of moisture (free water) and other nutrients; （5）提高了水分（游离水）和其他营养物质的扩散率；(6) supports the growth of active microorganisms;（6）支持有效微生物的生长； and (7) re-suspends heavier particles 7）使较重的粒子再次悬浮起来(Buendia et al. 2009; Jha et al. 2011; Ghanimeh et al. 2012).In addition, providing mixing arrangements also affects the overall net energy gains and reduces biogas production from the D-AnBioC processes.此外，混合安排也影响了整体的净能量收益，并减少了干式厌氧生物转化的过程中沼气的产生.4.5 Inoculum and enzyme addition4.5 接种物和酶促反应A major problem with the D-AnBioC process is that it requires a larger amount of inoculum for better biogas yield especially for batch operations. 干式厌氧生物转化过程中的一个主要问题是，它需要较大的接种量才能得到更好的沼气产率，尤其是对于批处理操作系统。Inoculum generally contains a mixed population of bacteria and archaea originally obtained from the previous batch of digestion. 接种量一般包含一个混合菌群和最初从前几批消化过程中获得的古细菌。This bacterial population from the previous batch is called adapted culture. 这种从上一批处理中获得细菌群体的方法被称为适应培养。But, the best used inoculum is reported as anaerobically digested sewage sludge from wastewater treatment plants (Forster- Carneiro et al. 2007b).但是，据报道，最好的接种方法是污水处理厂中污水污泥的厌氧消化.Other than sewage sludge,digested material from an established reactor or ruminant cultures or manure is often used as seed inocula.除了污水污泥，还有已建立的反应器的消化物，反刍物或粪便经常被用来作为菌种的接种物。4.6 Altering the feedstock and OLR4.6改变原料和有机负荷率（OLR） Varying the OLR to the bioreactors can be done to improve biogas yield.生物反应器的有机负荷率的变化可以改善沼气产量。Also, it is possible to get an inoculum which is stable within the system, that is, an inoculum which is able to withstand adverse environmental conditions. 此外，在系统内可还以得到一个的稳定的接种物，即能够承受恶劣的环境条件的接种物。Similarly, lower OLR could be used for the bioreactor system under lower biogas yield conditions. This is also done to avoid "short circuiting" (Zeshanet al. 2012).同样，在生物反应器系统的沼气产量低的条件下，可以采用低的有机负荷率。这样做也是为了避免出现“短路”的情况（Zeshan等，2012）.4.7 Neutralization techniques4.7中和技术 The single-stage D-AnBioC process requires initial neutralization to support the growth of methanogenic populations and to reduce time at the start-up phase.单级的干式厌氧生物转化过程开始需要中和作用来维持产甲烷菌的生长以及降低启动阶段的停留时间。In that case, the addition of alkali to increase the pH to near neutral can reduce the time required to start the methanogenesis process within the system, as reported by Zeshan et al. (2012).在2012年Zeshan等人曾报道，既然那样，通过加入碱来提高pH值使其接近中性，可以减少启动系统内的产生甲烷所需要的时间。Chen et al. (2010) reported that the alkalinity of about 2,500 mg CaCO3/L and a pH of above 7 is maintained by adding 0.2 g NaOH/g VS for effective CH4 conversion. Chen等人（2010）报告说，为了使CH4进行有效的转化，需要约2500mg碳酸钙/ L的碱度和7以上的pH值，这可以通过加入0.2gNaOH /gVS来维持。因此，在干式厌氧生物转化过程中添加碱性溶液以中和该系统，能够快速的产生甲烷。Therefore, the addition of an alkaline solution to neutralize the system can be used for the quick onset of methanogenesis process during D-A-BioC processes.4.8 Nutrient supplement4.8 补充营养Micro elements like iron, cobalt, nickel, tungsten, molybdenum, and selenium were reported to be important co-factors of enzyme or co-enzymes involved in the biosynthesis of CH4 and the growth of anaerobic bacteria. 据报道，在生物合成CH4和厌氧细菌的生长中，铁，钴，镍，钨，钼，硒等微量元素是重要的酶或酶的辅因子（ Nges等，2012）。While operating the system, particularly under high ammonia- N concentration, the addition of micronutrients supported process stability.在操作系统中，特别是在氨氮浓度很高时，添加微量营养素能够提高过程的稳定性。5 Factors affecting D-AnBioC efficiency5干式厌氧生物转化效率的影响因素The D-AnBioC processes frequently encounter inhibition problems which are harder to control (Guendouz et al. 2010). 干式厌氧生物转化过程经常遇到难以控制的抑制问题The main inhibiting compounds are VFAs, ammonia-N, metals and cations 主要的抑制化合物的挥发性脂肪酸（VFAs），氨氮，金属阳离子，.In addition, the accumulation of gases such as CO2, H2 and H2S also affect the overall process performance.此外，如CO2，H2和H2S气体的积累也会影响整体的工艺性能。5.1 Volatile fatty acids (VFAs)5.1挥发性脂肪酸（VFAs）VFAs are important intermediate compounds in the metabolic pathway of CH4 fermentation. 挥发性脂肪酸（VFAs）是CH4发酵代谢途径中的重要的中间体化合物。VFAs cause microbial stress particularly at very high concentrations.挥发性脂肪酸（VFAs）会导致微生物的压力，特别是浓度非常高时。Acetic, butyric and propionic acids are the major VFAs present during anaerobic bio-degradation.乙酸，丁酸和丙酸是厌氧生物降解中的主要的挥发性脂肪酸（VFAs）