600 MW燃煤机组脱硫浆液循环泵变频改造及节能优化研究

Study on frequency conversion transformation and energy saving optimization of desulfurization slurry circulating pump in 600 MW coal-fired unit

自超低排放政策实施以来,部分燃煤机组脱硫系统存在偏离设计工况运行、设备自动化水平低、调节灵活性差、脱硫关键设备选型不合理等问题,造成脱硫系统能耗高、辅控人员操作量大。从浆液循环泵变频改造边界条件确定、技术路线、节能控制优化调整等方面进行研究。在边界条件确定方面,综合考虑了入炉煤硫分波动大、负荷率低、总排口SO_(2)排放浓度低、浆液循环泵裕量大等因素,当上述因素至少满足一项时,浆液循环泵便可进行变频改造。在技术路线选择方面,根据不同脱硫系统特性,主要是确定变频泵改造的数量、功率、喷淋层是否分区等。在节能优化调整方面,通过节能方式固化、建立扰动量数学模型、特殊工况控制策略等方面进行优化。通过600 MW燃煤机组浆液循环泵变频改造项目的研究,结果表明,在机组80%负荷工况下,单塔1台浆液循环泵变频后,年节电量809.28(MW·h);双塔3台泵变频后,年节约电量1763(MW·h);双塔中3台变频泵自动调频时,在480 MW负荷、入口SO_(2)浓度2200 mg/m^(3)工况下,运行5台泵比4台泵节电115.5 kW。通过浆液循环泵变频改造,脱硫系统节电效果明显,循环泵启停次数显著减少,脱硫系统可靠性及自动投入率提高,辅控操作量降低30%。上述措施可为同类改造项目设计优化、运行调整提供一定的参考意义。

Since the implementation of the ultra-low emission policy,the desulfurization system of some coal-fired units has problems such as deviation from design conditions,low level of equipment automation,poor adjustment flexibility,and unreasonable selection of key desulfurization equipment,resulting in high energy consumption of the desulfurization system and a large amount of auxiliary control personnel.This paper studies the determination of boundary conditions,technical route,energy-saving control optimization and adjustment of slurry circulating pump frequency conversion transformation.In terms of determining the boundary conditions,comprehensive consideration has been given to the large fluctuations in the sulfur content of the coal entering the furnace,the low load rate,the low SO_(2)emission concentration at the total outlet,and the large margin of the circulating pump.When at least one of the above factors is satisfied,the pump can be modified.In terms of technical route selection,according to the characteristics of different desulfurization systems,determine the number,power,and whether the spray layer is partitioned and so on.In terms of energy-saving optimization and adjustment,optimization is carried out through the standardization of energy-saving methods,the establishment of a mathematical model of disturbance,and control strategies for special working conditions.Through the research on the frequency conversion transformation project of the slurry circulating pump of a 600 MW coal-fired unit,under the 80%load condition of the unit,the frequency conversion transformation of one slurry circulating pump in the absorption tower can save 809.28(MW·h)of electricity annually.After the frequency conversion of columns in series,1763(MW·h)of electricity was saved.Under the working condition of 480 MW load and inlet SO_(2)concentration of 2200 mg/m^(3),when the three pumps in the series tower are automatically frequency adjusted,running 5 pumps saves 115.5 kW of electricity compared with 4 pumps.Through the frequency conversion transformation of the slurry circulating pump,the power saving effect of the desulfurization system is obvious,the number of starting and stopping of the circulating pump is significantly reduced,the reliability of the desulfurization system and the automatic input rate are improved,and the auxiliary control operation volume is reduced by 30%.The above-mentioned measures can provide certain reference significance for the design optimization and operation adjustment of similar transformation projects.