Numerical Analysis of NO_x Control by Combustion Modifications in Pulverized Coal Utility Boiler

Abstract

Considerable research efforts focus on modeling NO x formation/destruction and predicting NO x emission so that it can be controlled. A motivation for this numerical study was to examine the efficiency of combustion modifications in the furnaces of Kostolac B 350 MWe boiler units, tangentially fired by pulverized lignite. Numerical analysis was done by an in-house developed NO x submodel, coupled with differential comprehensive combustion model, previously developed and validated. The NO x submodel focuses on homogeneous reactions of both the fuel and the thermal NO formation/destruction processes. The submodel was validated by comparison of predicted NO x emissions with available measurements at the boiler units. Selected predictions of the emission, the furnace exit gas temperature, NO concentration, gas temperature, and velocity field are given for the case-study furnace under different operating conditions. The individual or combined effects of coal and preheated air distribution over the individual burners and the burner tiers, the grinding fineness and quality of coal, and the cold air ingress were investigated. Reduced emissions of up to 20–30% can be achieved only by proper organization of the combustion process. Obtained results were verified by the boiler thermal calculations. An optimal range of the furnace exit gas temperatures was proposed, with respect to the safe operation of the steam superheater. Simulations by means of a computer code developed for the purpose, showed that the air staging using overfire air ports might provide the NO x emission reduction of up to 24% in the test-cases with relatively high emission and up to 7% of additional reduction in already optimized cases.

Numerical analysis on effect of furnace scale on heat transfer mechanism of coal particles in pulverized coal combustion field

“…Numerical simulation is a powerful tool for understanding such phenomena in each furnace with a different design. Recently, numerical simulations of pulverized coal combustion field in large-scale furnaces have been conducted by various research groups [1][2][3][4][5][6][7][8][9]. For numerical simulations of pulverized coal combustion, simplified models are generally employed because of the limitation of computational resources.…”

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

“…In order to enable analysis of processes for NO x /SO 2 emission reduction, submodels of NO x formation/destruction reactions and Ca-based sorbent calcination/sintering/sulfation reactions were selected, coupled with the in-house developed combustion code and applied for investigation of de-NO x primary measures and de-SO 2 by Furnace Sorbent Injection (FSI) method [78][79][80][81][82][83][84][85][86]. In order to enable efficient data input and meet the real engineering needs, a new user-friendly software interface, was developed as well [80,83].…”

“…An extensive numerical study, first of its kind in Serbia, was performed for the EPS to optimize the primary measures in the tangentially fired pulverized lignite furnaces of 350 MW e TPP Kostolac B boiler units [78]. Optimal combustion modifications in the casestudy furnaces were suggested: injection of 85% of coal through the main (lower-stage) burners, local excess air control by proper distribution of preheated air between the burner tiers and the usage of finer grinding of coal, enabling over 30% of NO x emission reduction and simultaneous control of the flame position; standalone application of over-fire air provided 25% of the NO x emission abatement [79,80]. Effects of the measures on the steam boiler efficiency and safety were examined by thermal calculations, in cooperation with the Faculty of Mechanical Engineering Belgrade.…”

Numerical Analysis of Pulverised Coal Fired Boiler with Different Burner Geometries

“…The developed sub-model of NO x formation/destruction is described in [9]. The NO x sub-model consists of reactions of fuel NO formation and depletion [10].…”