沼气是利用粪便、农作物秸秆等有机物在厌氧的条件下，经过微生物生理代谢产生主要成分为CH4和CO2，还有少量的H2、H2S、CO等可燃性气体，属生物质能源。开展沼气发酵的研究有着重大的意义和作用，本文沼气脱硫设备厂家就沼气发酵的影响因素进行了探讨。
Biogas is a kind of biomass energy, which utilizes feces, crop straw and other organic substances to produce CH4 and CO 2 through microbial physiological metabolism under anaerobic conditions. It also has a small amount of combustible gases such as H2S, CO and so on. The research on biogas fermentation is of great significance and function. In this paper, the influencing factors of biogas fermentation are discussed by the manufacturer of biogas desulfurization equipment.
1.温度
1. Temperature
沼气发酵可分为三个温度范围：50～65℃称高温发酵，20～45℃称中温发酵，20℃以下称低温发酵。此外，随自然温度变化的发酵方式称常温发酵。
Biogas fermentation can be divided into three temperature ranges: high-temperature fermentation at 50-65 degrees C, medium-temperature fermentation at 20-45 degrees C and low-temperature fermentation at 20 degrees C. In addition, the fermentation mode that changes with natural temperature is called normal temperature fermentation.
沼气发酵受到温度和温度波动的影响。在同一温度类型条件下，由于沼气发酵微生物的代谢活动随着温度的上升而增加，在一定的温度范围内，温度越高，发酵产气速率越快；短时间内若温度波动幅度过大时，可能导致停止产气。
Biogas fermentation is affected by temperature and temperature fluctuation. Under the same temperature type, because the metabolic activity of biogas fermentation microorganisms increases with the increase of temperature, in a certain temperature range, the higher the temperature, the faster the fermentation gas production rate; if the temperature fluctuation is too large in a short time, it may lead to the cessation of gas production.
2.酸碱度（PH值）
2. Acidity and alkalinity (PH value)
通常沼气池中的产甲烷细菌适宜的PH值范围为6.5～7.8，PH值的变化会直接影响产甲烷菌的生存和代谢。一般情况下，沼气池的PH值应维持在6.8～7.5之间，好在7.2左右。
Usually, the suitable PH value of methanogens in biogas digesters ranges from 6.5 to 7.8. The change of PH value will directly affect the survival and metabolism of methanogens. In general, the PH value of biogas digester should be maintained between 6.8 and 7.5, preferably around 7.2.
pH值在5.5以下，产甲烷菌的活动完全受到抑制，而pH值上升至8甚至8.5时，仍保持一定的产气率。产酸菌的pH值范围为4.0～7.0，在超过甲烷菌的佳pH值范围，酸性发酵可能超过甲烷发酵，造成反应器内“酸化”现象的发生。
When the pH value is below 5.5, the activity of methanogens is completely inhibited, while when the pH value rises to 8 or even 8.5, a certain gas production rate is maintained. The pH value of acid-producing bacteria ranges from 4.0 to 7.0. Acidification may occur in the reactor when acidic fermentation exceeds the optimum pH value of methanogens.
影响pH值变化的因素主要有以下几点：一是发酵原料的pH值；二是在厌氧发酵启动时，投料浓度过高，接种物中的产甲烷菌数量不足，以及在消化器运行阶段突然升高负荷，都会因产酸与产甲烷的速度失调而引起挥发酸的积累，导致pH值下降，这往往是造成厌氧发酵启动失败或终止的主要原因。
The main factors affecting the change of pH value are as follows: firstly, the pH value of fermentation raw materials; secondly, when anaerobic fermentation is started, excessive feed concentration, insufficient number of methanogens in inoculate, and sudden increase of load in digestion stage will cause the accumulation of volatile acid due to the imbalance of the speed of acid production and methanogenesis, resulting in the decrease of pH value, which often results in anaerobic fermentation. The main reasons for failure or termination of startup.
3.氧气含量
3. Oxygen content
沼气发酵启动和投料时带入的一部分氧气对沼气发酵危害不大，不会破坏沼气发酵的正常进行。这是因为沼气池中存在一部分好氧菌和兼性菌，带入的氧气很快会被不产甲烷细菌中的好氧菌或兼性菌消耗掉，使池内保持厌氧环境，同时这一部分氧气也使好氧菌、兼性菌与厌氧菌保持着动态的平衡关系，但为了保持好的厌氧环境，发酵过程中必须不漏气。
The oxygen brought in during the start-up and feeding of biogas fermentation is not harmful to the biogas fermentation and will not destroy the normal process of biogas fermentation. This is because there are some aerobic bacteria and facultative bacteria in the biogas digester. The oxygen brought in will soon be consumed by the aerobic bacteria or facultative bacteria in the methane-free bacteria, so that the anaerobic environment will be maintained in the digester. At the same time, this part of oxygen also keeps a dynamic balance between the aerobic bacteria, facultative bacteria and anaerobic bacteria. But in order to maintain a good anaerobic environment, no leakage must be found in the fermentation process.
4.沼气发酵原料的碳氮比
4. C/N Ratio of Biogas Fermentation Materials
发酵原料的碳氮比（C/N），是指原料中有机碳含量和氮含量的比例关系。沼气发酵微生物需要的一定的碳、氮、磷等营养物质，才能正常生长和进行生命活动。碳元素为微生物生命活动提供能量，是形成甲烷的重要物质；氮元素也是构成微生物细胞的主要元素。这三种营养元素之间的比例，不论是好氧发酵还是沼气发酵，氮与磷的比例是确定值，为5：1。碳与氮的比值则范围较宽，以往的实践认为发酵原料的C/N以（13～30：1）为宜，大于30：1效果不佳，小于13：1还可正常发酵。但是，实际上以人粪便为主要原料（C/N=3.9：1）的沼气池也能很好的运行。所以，正常的沼气发酵要求合适的碳氮比，但不严格，要重视沼气池的启动和培养好相适应的菌种，提高沼气发酵细菌的适应能力。
The C/N ratio of fermentation raw materials refers to the ratio of organic carbon content to nitrogen content in raw materials. Biogas fermentation microorganisms need certain nutrients such as carbon, nitrogen and phosphorus to grow normally and carry out life activities. Carbon provides energy for microbial life activities and is an important material for methane formation. Nitrogen is also the main element for microbial cells. The ratio of nitrogen to phosphorus, whether aerobic fermentation or biogas fermentation, is determined to be 5:1. The ratio of carbon to nitrogen is relatively wide. Previous practice considered that C/N of fermentation raw materials should be (13-30:1). The effect of more than 30:1 is not good. Fermentation can be normal if the ratio is less than 13:1. However, in fact, biogas digesters with human excrement as the main raw material (C/N=3.9:1) can also operate well. Therefore, normal biogas fermentation requires appropriate carbon-nitrogen ratio, but not strict. We should pay attention to the start-up of biogas digester and cultivate suitable strains to improve the adaptability of biogas fermentation bacteria.
5.沼气发酵接种物
5. Biogas fermentation inoculum
沼气发酵细菌的多少和质量的高低直接影响沼气发酵、产气速率和沼气的质量。沼气发酵能否快速启动与高质量和大量的接种物有关。
The quantity and quality of biogas fermentation bacteria directly affect biogas fermentation, gas production rate and biogas quality. The rapid start-up of biogas fermentation is related to high quality and a large number of inoculants.
如果沼气发酵启动时的接种物不够，可能会出现启动缓慢，经过很长时间，产气速率仍然较低的情况；接种物质量较差，产甲烷细菌数量较少，活性较低，此时水解性细菌和产氢产酸细菌很快繁殖，而产甲烷细菌繁殖较慢，导致不产甲烷作用较快，产甲烷与不产甲烷过程的平衡失调，就可能造成有机酸的缓慢积累，发酵液pH值下降，沼气池酸化，出现产气慢和沼气中甲烷含量低且质量差的情况。
If the inoculum is not enough at the start of biogas fermentation, the start-up may be slow, and after a long time, the gas production rate is still low; the inoculum quality is poor, the number of methanogenic bacteria is small, and the activity is low. At this time, hydrolytic bacteria and hydrogen-producing acidogenic bacteria multiply quickly, while methanogenic bacteria multiply slowly, resulting in a faster non-methanogenic effect, and methanogenic and non-methanogenic effects. The imbalance of methane process may result in the slow accumulation of organic acids, the decrease of pH value of fermentation broth, the acidification of biogas digester, the slow production of gas and the low content and poor quality of methane in biogas.
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2019-06-19
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