1. The influence of hydrogen sulfide on generating units
Hydrogen sulfide (H2S) is a colorless, toxic, flammable gas with a strong odor of rotten eggs. When the volume of hydrogen sulfide in the air exceeds 0.1%, it can cause headache, dizziness and other poisoning symptoms. Hydrogen sulfide (H2S) is highly corrosive to iron and other metals. It is also easy to absorb metal surface and various metal ions, resulting in water-insoluble sulfide deposition. In the process of biogas incineration, H2S can also be converted into highly corrosive sulfite mist, which will pollute the environment and corrode machinery and equipment. At the same time, H2S has intense corrosiveness to metal pipelines, incineration equipment, detection equipment and instrumentation in wet environment. Therefore, it is necessary for biogas to remove the H2S contained in it before use.
Hydrogen sulfide in biogas will cause severe corrosion to intake pipes, superchargers, intercoolers, spark plugs, cylinder liners, exhaust pipes and mufflers of biogas generating units. So it is necessary to pretreat the biogas before the biogas enters the generating unit and reduce the H2S to the allowable range of the generating unit in order to ensure the reliable operation of the generating unit.
2. The influence of moisture on generating units
In the process of using biogas to generate electricity, if the moisture content of biogas is too high, it will lead to excessive loss of intake pressure of generating units. In severe cases, it will cause engine power shaking, cylinder knocking, shutdown and other severe impact on its service life. Its detailed manifestations are as follows:
(a) Engine burning is difficult;
(b) Reducing the temperature of the incinerator and the power of the internal combustion engine;
(c) Because of the presence of reactive gases such as water vapor, the power consumption of turbocharging increases.
(d) The combination of water vapor and other acidic substances produces a central product, which corrodes the machine itself, shortens the service life of the machine and reduces the reliability of the machine.
3. Effect of Solid Impurities on Generator Units
Dust is one of the most widely involved and severely damaged pollutants in the atmospheric environment. Dust is an impurity that is clearly limited by the engine. Its primary influence lies in:
(a) Blocking pipelines, poor circulation, increasing pressure loss and operating costs;
(b) Increase the mechanical wear and tear, and decrease the service life of the equipment.
According to the requirement of biogas engine, installing treatment system before biogas engine to deal with the opposition between the gas source side and the gas side is an effective way to deal with the use of biogas generating units. The main manifestations are as follows:
1. Relative humidity of falling gas
The removal of water can be divided into two parts: the removal of condensed water and the removal of non-condensed water. The former can be accomplished by steam-water separator, while the latter is more complex. Now the following methods are the first to be used:
(a) Low temperature dehumidification: the temperature of the gas is lowered by the refrigeration equipment, so that the water vapor condenses between them, and then the system is eliminated;
(b) Adsorption: Select adsorbents with strong adsorptive effect to separate water from gas;
(c) Membrane filtration: Water is separated from gases under specific conditions by using membrane materials with special structures.
2. Decrease the content of impurities in gases
Impurities in gases are more complex components, because they are for the use of engines, so the determination of impurities should first be based on the requirements of the engine, and the following are the main ones:
(a) Removal of sulphur:
Physical, chemical and biological methods are the main methods for the removal of hydrogen sulfide-based sulfides. Physical method mainly refers to physical adsorption desulfurization. This method is simple to operate, but often requires large equipment, and adsorbent needs regeneration. Chemical method means that sulfur is solidified by chemical reaction. Now there are dry and wet methods. The main difference is that the physical shape of the reactant is the difference between solid and liquid. Biological desulfurization is a relatively new method nowadays. Its primary principle is to cultivate suitable bacteria in the reaction tank. These bacteria are fed with sulfide and fix the sulfur between them. For gases with low sulfur content, physical adsorption or dry desulfurization is generally economical and practical, and the operation is simple.
In addition, according to the environmental protection regulations of our country, when biogas is used as power, the content of H2S in biogas should not exceed 200 mg/Nm3. Therefore, after desulfurization treatment of biogas, it is necessary to use biogas analyzer to monitor the H2S content in biogas on-line in real time, to provide real-time and accurate data reference for owners, to help them optimize and adjust the pretreatment process of biogas, to improve the intake quality of biogas generating units, so as to ensure that the H2S content meets the requirements of biogas power generation.
Because the composition of biogas is complex, besides H2S, it also contains CH4, CO2, O2 and other gas components. If we want to ensure the biogas quality of biogas generating units, improve the calorific value of biogas, and ensure the power generation of biogas incineration, besides reducing the content of H2S, monitoring the concentration of CH4 and CO2 in biogas, in order to optimize the anaerobic fermentation process, improve the content of CH4 and reduce the content of CO2, it is also very important. Necessary.
(b) Removal of dust (particulate matter):
Generally, the method of filtration is used to limit the particulate matter to a certain range. In addition, some particles can be removed in the process of adsorption. In order to achieve a better removal effect, particulate matter in the gas is generally classified, filters with different precision are set up, and particulate matter is processed to the final requirements of the system step by step. This can not only reduce the cost of precision filtration, but also increase the reliability of the system operation.