Numerical simulation of the influence of stationary louver and coal particle size on distribution of pulverized coal to the feed ducts of a power plant burner

Abstract

One of the key requirements related to successful utilization of plasma technology as an oil-free backup system for coal ignition and combustion stabilization in power plant boilers is provision of properly regulated pulverized coal distribution to the feed ducts leading the fuel mixture to a burner. Proper regulation of coal distribution is deemed essential for achieving an adequate pulverized coal concentration in the zone where thermal plasma is being introduced. The said can be efficiently achieved by installation of stationary louver in the coal-air mixing duct ahead of the feed ducts of a burner. The paper addresses numerical simulation of a two-phase flow of air-pulverized coal mixture in the mixing ducts, analyzing the effects of particle size distribution on pulverized coal distribution to the burner feed ducts. Numerical simulation was performed using the FLUENT 6.3 commercial code and related poly-dispersed flow module, based on the PSI-CELL approach. Numerical experiments have been performed assuming a mono-dispersed solid phase with particle diameter ranging from 45 mm to 1200 mm. Distance between the louver blades and the resulting effect on the flow profile was analyzed as well. Results obtained indicate that the size of coal particles considerably influence the overall solid phase distribution. While fine particles, with diameters at the lower end of the above specified range, almost fully follow the streamlines of the continuous phase, coarser particles, which hit the louver blades, deflect towards the thermal plasma zone. In this manner, a desired phase concentration in the considered zone can be reached. For the said reason, installation of stationary louver have been deemed a very efficient way to induce phase separation, primarily due to more pronounced impact of the installed louver on discrete phase flow then the impact on the flow of the continuous phase.

Numerical and experimental study of temperature distribution on thermal plant coal mill walls

“…The calculation of heat losses comprises the following elements: natural convection outside the mill and ducts, radiated losses from the external surfaces and the internal convection of the preheated air and the pulverized coal mixture. The experimental and numerical studies of the multiphase flow and temperature distribution in the VM, presented in , illustrate this aspect of the coal mill characterization. The heat balance calculation for the Kostolac B thermal power plant coal mills shows that the heat emitted from the mill body to the environment is about 1200 kW, which is 4% losses of the total amount of heat contributed by hot primary air entering the mill and the heat generated by grinding.…”

“…The technical characteristics of the VM are described in .The multiphase flow (air mixture) in the VM consists of recirculated gases, coal powder and abrasive particles. The milling quality, the coal powder distribution, and the ventilation characteristic of the mill depend on the mill design as pointed out in . The pulverization of coal into fine particles is carried out in order to increase the specific surface area and to optimize the rate of heat and mass transfer between coal particles and the surroundings hot gas.…”

Numerical simulation of multiphase flow in ventilation mill and channel with louvers and centrifugal separator

“…It is especially useful when investigations on complex thermal power plants are needed [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. There is a wide range of software for numerical simulations.…”

Review of the investigations of pulverized coal combustion processes in large power plants in laboratory for thermal engineering and energy: Part B

“…This unit built in 1979, with nominal steam capacity 920 t/h and gross power 308 MWe, at the end of 2006 had more than 150000 hours on electric network, with 750 stop/starts and generated 235 GWh. In period 2006 to 2011 applied research including measurements and analysis, calculation and numerical simulation of mills/boiler process parameters made a basis for investment decision and step by step realization [25][26][27][28][29][30][31][32]. Improved mills capacity (up to 110 t/h), coal dust concentration distribution over main/vapour burner, and tightness of mills/air tract and boiler, enabled improved combustion process, higher heat generation in the whole furnace with originally projected flue gas temperature at the furnace exit and lower NO x emission (from 440-510 mg/Nm 3 before to <330 mg/Nm 3 after rehabilitation and modernization).…”