title: Measurement of slurry droplets in coal-fired flue gas after WFGD.
abstract: China owns the world's largest capacity of coal-fired power units. By the end of 2012, the capacity of installed national thermal power has been 819.68 million kilowatts. The latest standard requires that newly built power plants emit SO2 in no more than 100 mg/m(3) and the emission of old ones be lower than 200 mg/m(3) while in some key areas the emission should be controlled under 50 mg/m(3). So by the end of 2012, 90% of the active coal-fired units have been equipped with flue gas desulfurization devices. Among the desulfurization methods adopted, limestone-gypsum wet flue gas desulphurization accounts for 92%, causing the problem of fine droplets in the exhaust gas after defogger, which may even form "gypsum rain." At present, sampling methods are widely used at home and abroad, such as magnesium ion tracer method, modified magnesium ion tracer method and chemical analysis. In addition, some scholars use aerodynamic methods, such as ELPI, to measure the diameter distribution and concentration. The methods mentioned above all have their own demerits, such as the inability to on-line, continuous measurements and the need of prolonged measuring time. Thus, in this paper some potential optical on-line methods are presented, such as Fraunhofer diffraction pattern analysis and wavelength-multiplexed laser extinction. Also brought up are their measuring scope and merits. These methods have already been utilized to measure small liquid droplets and their demonstrations and evaluations are as well stated. Finally, a 3D imaging method based on digital holographic microscope is proposed for in-line measurement of size and concentration of slurry droplets. The feasibility of this method is demonstrated by preliminary experimental investigation.
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China.
authors.forename: Xue-Cheng
authors.initials: XC
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China.
authors.forename: Hua-Feng
authors.initials: HF
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China.
authors.forename: Yong-Xin
authors.initials: YX
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China.
authors.forename: Cheng-Hang
authors.initials: CH
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, 310027, China. xgao1@zju.edu.cn.
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000517:prevention & control; D002119:Calcium Carbonate / Q000032:analysis; D002133:Calcium Sulfate / Q000032:analysis; D002681:China; D003031:Coal; D008274:Magnesium / Q000032:analysis; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D011210:Power Plants
chemical_list: D000393:Air Pollutants; D003031:Coal; D052638:Particulate Matter; D002119:Calcium Carbonate; D008274:Magnesium; D002133:Calcium Sulfate
keywords: Coal-fired power plant; Concentration measurement; Defogger; Slurry droplet; Wet flue gas desulphurization