1. Biogas quality
To use biogas for power generation, the first step is to meet the requirements of biogas power generation units for biogas quality. The requirements for biogas quality in the "Medium and High Power biogas power generation units" (GBT29488-2003) and "Technical Specifications for biogas power plants" (NY/T1704-2009) are as follows.
(1) The low calorific value of biogas is ≥ 14MJ/Nm, which is equivalent to a methane volume fraction of no less than 30% in biogas. The change rate of methane volume fraction in biogas within 30 seconds should not exceed 2%, and the change rate of methane volume fraction in biogas during continuous operation of the unit should not exceed 5%.
(2) The temperature of biogas shall not exceed 50 ℃.
(3) The specific requirements for biogas composition of biogas generator units are shown in the table below.
Note: The standard reference conditions for biogas volume are 101.3kPa, 20 ℃; Calculate based on the conversion of all sulfur-containing components in biogas into hydrogen sulfide.
① The impact of H2S on generator sets
During biogas power generation, H2S in biogas will cause serious corrosion to the intake pipe, supercharger, intercooler, spark plug, cylinder liner, exhaust pipe and silencer of the biogas generator set, thus affecting the service life of the unit. Therefore, biogas must be pretreated before entering the generator set, and the reliable operation of the unit can be ensured only by reducing H2S to the allowable range of the unit.
② The impact of moisture on generator sets
In the process of biogas power generation, excessive moisture content in biogas can lead to excessive loss of intake pressure of the generator set. In severe cases, it can cause problems such as engine power fluctuations, cylinder knocking, and shutdown, seriously affecting its service life. Its specific manifestation is:
(a) Difficulty in engine ignition;
(b) Reduce the temperature of the combustion chamber and reduce the efficiency of the internal combustion engine;
(c) The presence of reactive gases such as water vapor can increase pressure and power consumption;
(d) The intermediate products produced by the combination of water vapor and other acidic substances can corrode the generator set, shorten its service life, and reduce its reliability.
③ The impact of dust on generator sets
Dust is a clearly restricted impurity in engines, and its main impact is:
(a) Blocking the pipeline, poor circulation, increased pressure loss, and increased operating costs;
(b) Increase mechanical wear and reduce equipment service life.
2. Biogas pressure
The biogas pressure of the biogas generator set at a distance of 1 meter from the gas branch pipe of the unit shall not be less than 3 kPa. When the gas supply pressure is less than 3 kPa, gas boosting equipment shall be equipped; When the gas supply pressure exceeds 5kPa, it is necessary to add a suitable pressure reducing valve. When the biogas generator set is running, the allowable biogas pressure fluctuation of the engine is generally less than 0.4kPa/s.
3. Biogas consumption
The amount of biogas used in a biogas generator set should be determined based on the efficiency and load of the generator set, and the supply of biogas during power generation should be relatively stable. When calculating the usage of biogas, it should be less than 1.2 times the rated power consumption of the biogas generator. The gas supply system should be equipped with facilities for regulating gas consumption and gas measuring instruments. When the biogas generator unit operates continuously, the capacity of the gas storage device should be designed based on the total rated power of the operating unit exceeding 3 hours of gas consumption. When the biogas generator unit operates intermittently, the capacity of the gas storage device should be designed based on the total amount of biogas greater than the intermittent power generation time.
Among them, the gas regulation system of the biogas generator unit is generally achieved by using an electronic speed regulation system to control the opening of the disc door. The speed regulation system consists of a speed sensor, speed controller, actuator, and driver, forming a closed-loop speed regulation and control system to achieve control of the mixed gas intake volume. Gas measuring instruments generally use biogas flow meters, such as the Ruiyi self-control ultrasonic gas flow meter BF-3000/BF-3000B, to measure the instantaneous and cumulative flow of biogas in real-time, providing scientific data support for calculating biogas usage.
This article is dedicated by the biogas generator unit. For more relevant knowledge, please click on: https://www.huannengpower.cn
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