Influence of mass air flow ratio on gas-particle flow characteristics of a swirl burner in a 29 MW pulverized coal boile
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RESEARCH ARTICLE
Rong YAN, Zhichao CHEN, Shuo GUAN, Zhengqi LI
Influence of mass air flow ratio on gas-particle flow characteristics of a swirl burner in a 29 MW pulverized coal boiler
© Higher Education Press 2020
Abstract In a gas/particle two-phase test facility, a threecomponent particle-dynamics anemometer was used to measure the characteristics of gas/particle two-phase flows in a 29 megawatt (MW) pulverized coal industrial boiler equipped with a new type of swirling pulverized coal burner. The distributions of three-dimensional gas/particle velocity, particle volume flux, and particle size distribution were measured under different working conditions. The mean axial velocity and the particle volume flux in the central region of the burner outlet were found to be negative. This indicated that a central recirculation zone was formed in the center of the burner. In the central recirculation zone, the absolute value of the mean axial velocity and the particle volume flux increased when the external secondary air volume increased. The size of the central reflux zone remained stable when the air volume ratio changed. Along the direction of the jet, the peak value formed by the tertiary air gradually moved toward the center of the burner. This tertiary air was mixed with the peak value formed by the air in the adiabatic combustion chamber after the cross-section of x/d = 0.7. Large particles were concentrated near the wall area, and the particle size in the recirculation zone was small. Keywords industrial pulverized coal boiler, swirl burner, air/particle flow, particle dynamic analyzer (PDA)
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Introduction
In China, coal-fired industrial boilers are a primary type of coal-fired equipment, with the exception of utility boilers. Received Oct. 18, 2019; accepted Jul. 7, 2020; online Sept. 10, 2020
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Rong YAN, Zhichao CHEN ( ), Shuo GUAN, Zhengqi LI School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China E-mail: [email protected]
There are almost 600000 such industrial boiler units, consuming nearly 640 million tons of coal a year. In many developed countries, coal-fired industrial boilers mainly use pulverized coal; however, those in China primarily use lump coal. The main problems associated with China’s coal-fired industrial boilers are [1] that they have a low actual average thermal efficiency of approximately 65% and they produce excessive pollutant emissions which generally cannot meet the national and local emission standards. Medium and small-capacity pulverized coal industrial boilers became mature products in developed countries in the mid-to-late 1990s, especially in Germany and France [2]. Compared with the layered coal burning boiler, pulverized coal industrial boilers use a combustion mode for chamber combustion. The pulverized coal particles are sprayed into the furnace with air to facilitate suspension combustion. This makes the boiler’s thermal efficiency reach more than 90%, and pollutants effectively controlled. In the 1960s, Feng [3] successfully transformed a han
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