在沼气发电过程中,沼气发电机组对沼气的成分、温度、压力、用量特别敏感,发电机组要求进气系统必须保持空燃比的恒定和适度,避免空燃比过大,引起熄火;也要避免空燃比过小,引起温度高及爆震。空燃比是影响沼气发电机燃烧性能的重要因素之一,而沼气温度、压力、成分的变化都会影响空燃比,因此,在选择进行沼气发电前,不对沼气气质进行合理的把控,将导致发电机组无法正常运行,造成较大的经济损失。
In the process of biogas power generation, biogas generator units are particularly sensitive to the composition, temperature, pressure, and amount of biogas. The generator unit requires that the intake system must maintain a constant and moderate air-fuel ratio to avoid excessive air-fuel ratio that may cause flameout; It is also necessary to avoid excessively low air-fuel ratio, which can cause high temperature and detonation. The air-fuel ratio is one of the important factors that affect the combustion performance of biogas generators, and changes in the temperature, pressure, and composition of biogas can affect the air-fuel ratio. Therefore, before choosing to use biogas for power generation, not properly controlling the biogas quality will lead to the inability of the generator unit to operate normally, resulting in significant economic losses.
1、沼气质量
1. Biogas quality
利用沼气发电,要满足沼气发电机组对沼气质量的要求,《中大功率沼气发电机组》(GBT29488-2003)、《沼气电站技术规范》(NY/T1704-2009)对沼气质量的要求如下。
To generate electricity using biogas, it is first necessary to meet the requirements for biogas quality of biogas generating units. The requirements for biogas quality in the Medium and Large Power biogas generating units (GBT29488-2003) and the Technical Specifications for Biogas Power Plants (NY/T1704-2009) are as follows.
(1) 沼气低位发热值≥14MJ/Nm,相当于沼气中甲烷体积分数不小于30%。沼气中甲烷在30s内的体积分数变化率不应超过2%,机组连续运行期间沼气中甲烷体积分数变化率不超过5%。
(1) The low calorific value of biogas is ≥ 14MJ/Nm, which is equivalent to the methane volume fraction in biogas not less than 30%. The change rate of methane volume fraction in biogas within 30s shall not exceed 2%, and the change rate of methane volume fraction in biogas during continuous operation of the unit shall not exceed 5%.
(2) 沼气温度不高于50℃。
(2) The temperature of biogas shall not be higher than 50 ℃.
(3) 沼气发电机组对沼气成分的具体要求如下表。
(3) The specific requirements for biogas components of biogas generator units are shown in the table below.
注:沼气体积的标准参比条件是101.3kPa,20℃;按照沼气中所含硫成分全部转化为硫化氢计算。
Note: The standard reference condition for biogas volume is 101.3kPa, 20 ℃; Calculated based on the conversion of all sulfur containing components in biogas into hydrogen sulfide.
①H2S对发电机组的影响
① Impact of H2S on generator sets
沼气发电时沼气中的H2S会对沼气发电机组的进气管道、增压器、中冷器、火花塞、气缸套、排气管和消音器等造成严重腐蚀,从而影响机组寿命,所以沼气在进入发电机组之前必须进行沼气预处理,将H2S降到机组允许的范围内才能保证机组的可靠运行。
During biogas power generation, H2S in biogas can cause serious corrosion to the intake pipes, superchargers, intercoolers, spark plugs, cylinder liners, exhaust pipes, and silencers of the biogas generator unit, thereby affecting the unit's life. Therefore, biogas pretreatment must be conducted before biogas enters the generator unit to reduce H2S to the allowable range of the unit to ensure reliable operation of the unit.
②水分对发电机组的影响
② Effect of moisture on generator sets
沼气发电过程中,沼气水分含量过大,会导致发电机组的进气压力损耗过大,严重情况下,会引起发动机功率波动、敲缸、停机等问题,严重地影响其使用寿命。其具体表现为:
During biogas power generation, excessive moisture content in biogas can lead to excessive intake pressure loss of the generator set. In severe cases, it can cause engine power fluctuations, cylinder knocking, shutdown, and other issues, seriously affecting its service life. The specific performance is as follows:
(a)发动机点火困难;
(a) Difficulty in ignition of the engine;
(b)降低燃烧室温度,降低内燃机效率;
(b) Reduce combustion chamber temperature and reduce internal combustion engine efficiency;
(c)水蒸气等无功气体的存在,会增压和增大功耗;
(c) The presence of reactive gases such as water vapor can pressurize and increase power consumption;
(d)水蒸气与其他酸性物质化合产生的中间产物,会对发电机组产生腐蚀,缩短使用寿命,降低可靠性。
(d) The intermediate products produced by the combination of water vapor and other acidic substances can cause corrosion to the generator set, shorten its service life, and reduce its reliability.
③粉尘对发电机组的影响
③ Impact of dust on generator sets
粉尘是发动机明确限制的杂质,它主要影响在于:
Dust is a clearly restricted impurity in the engine, and its main impact is:
(a)堵塞管路,流通不畅,加大压损,增加运行费用;
(a) Blocking the pipeline, impeded circulation, increased pressure loss, and increased operating costs;
(b)增大机械磨损,降低设备使用寿命。
(b) Increase mechanical wear and reduce equipment service life.
2、沼气压力
2. Biogas pressure
沼气发电机组在距离机组燃气支管钱1m处的沼气压力不低于3kPa,当供气压力低于3kPa时,应配置气体增压设备;当供气压力超过5kPa时,则需要增加合适的减压阀。在沼气发电机组运行时,发动机允许的沼气压力波动一般要小于0.4kPa/s。
The biogas pressure of the biogas generator unit at a distance of 1m from the unit gas branch pipe shall not be lower than 3kPa. When the gas supply pressure is lower than 3kPa, gas boosting equipment shall be equipped; When the air supply pressure exceeds 5kPa, it is necessary to add a suitable pressure reducing valve. When the biogas generator unit is running, the allowable biogas pressure fluctuation of the engine is generally less than 0.4 kPa/s.
3、沼气用量
3. Biogas consumption
沼气发电机组的沼气用量应根据发电机组的效率和负荷确定,发电时沼气的供气量应相对稳定。在计算沼气使用量时,应小于沼气发电机额定功率耗气量的1.2倍。供气系统应设有调节用气的设施和气体计量仪表。沼气发电机组连续运行时,储气装置容量应按照运行机组总额定功率大于3h的用气量设计。沼气发电机组间歇运行时,储气装置容量应按照大于间断发电时间的沼气总量设计。
The amount of biogas used in a biogas generator unit should be determined based on the efficiency and load of the generator unit, and the amount of biogas supplied during power generation should be relatively stable. When calculating the amount of biogas used, it should be less than 1.2 times the rated power consumption of the biogas generator. The gas supply system shall be equipped with facilities for regulating gas consumption and gas metering instruments. During continuous operation of biogas generating units, the capacity of the gas storage device should be designed based on the gas consumption with the total rated power of the operating unit greater than 3h. When the biogas generator unit operates intermittently, the capacity of the gas storage device should be designed based on the total amount of biogas that is greater than the intermittent power generation time.
其中,沼气发电机组的用气调节系统,一般采用电子调速系统控制碟门开度来实现的,调速系统由转速传感器、速度控制器、执行器和驱动器组成,构成闭环的速度调节与控制系统,实现对混合气体进气量的控制。气体计量仪表一般是采用沼气流量计,如锐意自控超声波气体流量计BF-3000/BF-3000B,用以实时计量沼气的瞬时流量和累计流量,为计算沼气使用量提供科学的数据支撑。
Among them, the gas consumption regulation system for biogas generating units 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 rotational speed sensor, a speed controller, an actuator, and a driver, forming a closed-loop speed regulation and control system to achieve control of the intake amount of mixed gas. Gas metering instruments generally use biogas flow meters, such as the Ruiyi Automatic Ultrasonic Gas Flowmeter BF-3000/BF-3000B, to measure the instantaneous and cumulative flow of biogas in real time, providing scientific data support for calculating the amount of biogas used.
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