Effects of Bias Concentration Ratio on Ignition Characteristics of Parallel Bias Pulverized Coal Jets

Abstract

To further advance pulverized coal (PC) combustion theory and enable the rational development of horizontal bias combustion technology, combustion experiments were conducted in a 250 kW pilot-scale bias combustion simulator; multiple research means of combustion temperatures, flame spectra, burnout rates of residual solids, and NO x formation were used. A blend of sub-bituminous coal from Indonesia and bituminous coal from Australia was tested. The effects of bias concentration ratio (BCR) on the ignition characteristics of parallel bias PC jets in a reducing atmosphere were investigated. The results indicate that with increasing BCR for parallel bias PC jets, the standoff distance gradually decreased; the peaks of subsequent combustion temperature and visible-light intensity gradually increased; the continuous flame regions became advanced and concentrated; the flame stability gradually increased; the burnout rate gradually increased; the NO x formation gradually decreased, and the ignition characteristics gradually improved. Except at a BCR of 1, the PC ignition of the fuel-rich jet was better than that of the fuel-lean jet, and the continuous flame region of parallel bias PC jets leaned obviously in the direction of the fuel-rich jet. The bias combustion changed the ignition mode of primary air PC jets. There was homogeneous ignition mode at a BCR of 1; when BCR increased to no less than 3, the ignition mode changed to homogeneous–heterogeneous combined ignition, which is beneficial to the PC ignition conditions. Based on the research results in this paper, the recommended BCR for the design of a horizontal bias combustion PC burner is 4–5.

Numerical study of further NO x emission reduction for coal MILD combustion by combining fuel‐rich/lean technology

“…The modification of the original burner to two fuel-rich/ lean jets is inspired by previous studies, 20,21,[27][28][29] of which the details are shown in Figure 2A. The original burner is split into two identical rectangular jets with a small distance in between provided that the total area remains unchanged.…”

“…[20][21][22][23][24] In specific, Zeng et al 20 experimentally investigated how the equivalence ratio impacts on the NO x emission for a furnace with fuel-rich/lean technology implemented. The implementation of fuelrich/lean technology can be achieved by simply replacing the original jet with two parallel jets with different equivalence ratios.…”

“…Many studies have reported the applications of fuel-rich/lean technology on the pilot and industrial scale boilers/reactors with mitigated NO x emissions. [20][21][22][23][24] In specific, Zeng et al 20 experimentally investigated how the equivalence ratio impacts on the NO x emission for a furnace with fuel-rich/lean technology implemented. The results showed mitigated NO x emissions with the increase of the difference between the equivalence ratios at the two fuel-rich/lean jets.…”

Influence of nozzle height to width ratio on ignition and NOx emission characteristics of semicoke/bituminous coal blends in a 300 kW pulverized coal-fired furnace

“…Compared with DTFs, the miniature pilot-scale experimental system has achieved better experimental results for industrial applications due to the different ignition characteristics achieved with various heating modes [14,15]. The researchers from HIT, Zeng et al [16][17][18] and Zhao et al [19], established a PF test burner in this pilot-scale test furnace, which simulated the ignition and combustion process of a bias PF tangential burner of actual tangentially fired boilers. The effects of primary air (PA) properties, pulverized coal (PC) concentration, raw coal equivalent moisture, and pulverized coal fineness on the ignition characteristics of parallel bias PF jets were systematically studied, which improved the design and operation parameters for rational tangential burner industrial applications.…”

“…Based on Refs. [16][17][18], the SC co-firing characteristics of parallel PF jets with different burner nozzle height to width ratios (i.e., h f /b) were studied in this work to achieve a strong and steady ignition, reduce NO x emissions, and prevent slagging [20]. In this work, to study the ignition characteristics of the blending combustion of bituminous coal and SC, three tangential burners with different nozzle h f /b values were produced, which were installed on a 300 kW pilot-scale PF combustion test furnace with six jet intersections [16], and a large SC blending ratio (50%) and highly volatile bituminous coal were used.…”