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.

Emission Characteristics of Particulate Matter from Two Ultralow-Emission Coal-Fired Industrial Boilers in Xi’an, China

“…The PM 1 mass concentration at the #3 scrubber inlet was 0.97 mg/Nm 3 , while that at the #1 scrubber inlet was 4 mg/Nm 3 . When the PM mass concentration at the scrubber inlet is low, the entrainment of the micrometer-size circulating slurry droplets or micrometer-size insoluble particles in the slurry by flue gas could offset the PM removal performance of the scrubber, resulting in the increase of the PM concentration …”

“…When the PM mass concentration at the scrubber inlet is low, the entrainment of the micrometer-size circulating slurry 23 Wang et al, 22 Ge et al, 45 Wen et al, 46 Shang et al, 44 and Cao et al 24 droplets or micrometer-size insoluble particles in the slurry by flue gas could offset the PM removal performance of the scrubber, resulting in the increase of the PM concentration. 40 The #1 WESP can effectively remove PM 10 , PM 2.5 , and PM 1 , and the removal efficiency varies in the range of 29.25−29.58% (relative to the PM concentration at the WFGD inlet). The removal efficiency of PM 10 , PM 2.5 , and PM 1 by #3 WESP was higher, which is 30.12, 62.27, and 88.60%, respectively.…”

A study on air-cooling waste heat recovery from molten slag of slag-tap boilers

“…Then ''gypsum rain'' (particulate pollution) and ''white smoke'' (visual pollution) will occur. [22][23][24] Through heating the desulfurized flue gas, the proposed system can effectively mitigate these problems. 3.…”

“…Then “gypsum rain” (particulate pollution) and “white smoke” (visual pollution) will occur. 22–24 Through heating the desulfurized flue gas, the proposed system can effectively mitigate these problems. The proposed system can improve the flue gas treatment system economically. When the desulfurized flue gas goes through the chimney (E7), the formation of sulfuric acid mist tends to cause low-temperature corrosion on the inner surface, which will increase the investment on chimney.…”

Effect of Gas-Liquid Contact Intensification on Heat and Mass Transfer in Deflector and Rod Bank Desulfurization Spray Tower

“…Wet flue gas desulfurization (WFGD) is used to treat most of the flue gas produced by the power and heat production and supply industries in China [1]. Through the countercurrent contact between acidic flue gas and alkaline slurry, the acidic gas is absorbed by the slurry, thus achieving the purpose of removing sulfur dioxide [2,3].…”