During the biogas power generation process, due to the design and material characteristics of the biogas generator set itself, the generator set is particularly sensitive to some components in the biogas (such as H2S, moisture, solid impurities, etc.). If not handled properly, the generator set will not be able to operate normally.
Impact of hydrogen sulfide:
Hydrogen sulfide (H2S) is highly corrosive to metals such as iron, and is also easily adsorbed on metal surfaces and reacts with various metal ions to form water-insoluble sulfide precipitation. When biogas is burned, the H2S in it can also be converted into highly corrosive sulfurous acid mist, which will pollute the environment and corrode machinery and equipment. At the same time, H2S is highly corrosive to metal pipes, combustion equipment, detection equipment and instruments in a humid environment, so the H2S contained in the biogas must be removed before it is used. When using biogas for power generation, the hydrogen sulfide in the biogas will cause serious corrosion to the intake pipe, supercharger, intercooler, spark plug, cylinder liner, exhaust pipe and muffler of the biogas generator set, affecting the life of the unit. Therefore, biogas must be pre-treated before entering the generator set to reduce H2S to the allowable range of the unit to ensure the reliable operation of the unit.
Impact of moisture:
If the moisture content of biogas is too high, it will cause excessive intake pressure loss of the generator set. In severe cases, it will cause engine power fluctuations, knocking, and shutdown, which will seriously affect its service life.
Its specific manifestations are: engine ignition is difficult; lowering the temperature of the combustion chamber and reducing the efficiency of the internal combustion engine; due to the presence of reactive gases such as water vapor, the power consumption of boosting increases; water vapor and other acidic substances combine to produce intermediate products, which corrode the machine itself, shorten the service life of the machine, and reduce the reliability of the machine.
Impact of solid impurities:
Dust is a pollutant in the atmospheric environment that involves a wider range and is more harmful. Dust is an impurity that is clearly restricted by the engine.
It will block the pipeline, sluggish circulation, increase pressure loss, increase operating costs, increase mechanical wear, and reduce the service life of the equipment.
Solution:
In view of the engine's requirements for biogas, installing a pre-treatment system in front of the biogas engine to solve the contradiction between the gas source side and the gas use side is an effective way to solve the problem of biogas generator utilization. It is mainly divided into two parts: reducing the relative humidity of the gas and reducing the content of gas impurities.
Considering the specific situation, the removal of moisture can be simply divided into two parts: the removal of condensed water and the removal of uncondensed water. The former can be achieved by using a steam-water separator, and the latter is more complicated to achieve. The main methods are: low-temperature dehumidification, adsorption, and membrane filtration.
There are three main methods for removing sulfides, mainly hydrogen sulfide, namely physical, chemical, and biological methods. Among them, the physical method mainly refers to physical adsorption desulfurization, which is easy to operate, but often requires equipment that occupies a large area, and the adsorbent needs to be regenerated. The chemical method refers to solidifying sulfur by chemical reaction. There are currently dry and wet methods. The difference is mainly whether the physical form of the reactant is solid or liquid. Biological desulfurization is a relatively new method. Its main principle is to cultivate suitable bacteria in the reaction tank. These bacteria use sulfide as nutrients to fix the sulfur in it. For gases with low sulfur content, physical adsorption or dry desulfurization is generally more economical and practical, and easy to operate.
In addition to H2S, it also contains CH4, CO2, O2 and other gas components. If you want to ensure the quality of biogas of biogas generator sets, improve the calorific value of biogas, and ensure the efficiency of biogas combustion and power generation, in addition to reducing the H2S content, it is also necessary to monitor the concentration of CH4 and CO2 in biogas to provide a reference for optimizing anaerobic fermentation processes, increasing CH4 content, and reducing CO2 content.
