超超临界燃煤发电机组湿法脱硫系统优化研究 - -

针对某1 000 MW超超临界机组湿法脱硫系统运行中存在运行能耗大、成本高等技术难题,采用NGA2000-MLT3型烟气分析仪实时测量湿法脱硫系统进出口SO_2及O_2浓度,得到机组脱硫效率,并测试或计算试验期间石灰石、SO_2排污费及脱硫系统主要设备电耗等成本。根据试验结果分别研究了浆液循环泵组合方式、浆液pH、吸收塔液位对脱硫效率的影响,并根据试验期间机组运行状况计算出脱硫系统总成本,得到脱硫系统最优运行方式。结果表明:1 000 MW负荷工况下,机组运行过程中,选择BD浆液循环泵组合时,烟囱出口SO_2浓度较低,但浆液循环泵电耗偏高;选择BC浆液循环泵组合成本适中,吸收塔脱硫效率可达97.06%,同时烟囱出口SO_2浓度有一定裕度,是此工况下最优的浆液循环泵组合方式;吸收塔浆液pH值过高,不利于石灰石的溶解,pH值过低时,SO_2吸收速率下降。1 000 MW负荷、BC浆液循环泵组合时,最佳浆液pH值为5.50～5.60,pH值进一步降低,SO_2排放将超过电厂排放限值;吸收塔液位对脱硫系统运行成本有重要影响,吸收塔液位升高,可提高系统脱硫效率,但会相应增加氧化风机电耗。最佳浆液循环泵组合方式及pH值时,通过不断调整吸收塔液位,研究吸收塔液位对脱硫系统总成本的影响,结果表明:此工况时最佳吸收塔液位为8.00～9.00 m,吸收塔液位由9.53 m降至9.01 m,脱硫总成本由2 010.45元/h降至1 916.65元/h,降低了9.64%。 In view of the technical problems of large energy consumption and high cost in the operation of the wet desulfurization system ina 1 000 MW ultra-supercritical boiler,the SO_2 and O_2 concentration on the inlet and outlet of the flue gas desulfurization system was meas-ured timely by using a NGA2000-MLT3 type flue gas analyzer,the desulfurization efficiency of the system was obtained,and the operation-costs including limestone,SO_2 discharge fee and the main equipment power consumption of desulfurization system during the test were cal-culated or tested. According to the test results,the effect of the slurry circulating pump combination mode,pH value of the slurry liquid and the liquid level of absorber on the desulfurization efficiency were studied respectively. The desulfurization cost was calculated according tothe operation condition of the unit during the test period,and the optimum operation mode of the desulfurization system was obtained. Theresults indicate that during the operation process,when slurry circulating pump combination of BD is used,the SO_2 concentration at outletof the chimney is low,but the power consumption of slurry circulating pump is high under 1 000 MW load. When choosing the slurry circu-lating pump combination of BC,the costs are moderate,the desulfurization efficiency of absorption tower can reach 97.06%,and there is a margin of SO_2 concentration at outlet of the chimney at the same time,therefore the optimal choice of slurry circulating pump combinationunder 1 000 MW is BC. A high pH value of slurry in the absorption tower is not conducive to the dissolution of limestone,while when thepH value is too low,the SO_2 absorption rate decreases. The test results show that the best pH value of slurry is in the range of 5.50-5.60 under 1 000 MW and the slurry circulating pump combination of BC. As the pH value is further reduced,SO_2 emissions will exceed thelimit of power plant emissions. The level of the