RESUMO
Most published works focused on the characteristics of chemiluminescence in homogeneous flames, but the research about radiation spectrum in heterogeneous flames was still limited. In this paper, improved hot oxygen burner (HOB) technology is applied to ignite coal water slurry (CWS) directly in the open space, for stable combustion. Radiation spectrum and two-dimensional OH* chemiluminescence in methane and CWS diffusion flames are measured by a fiber optic spectrometer and a high-spatial-resolution UV imaging system. The results show that OH* (309.12 nm), CH* (431.42 nm) and C2* (463.52~563.43 nm) radicals exist in both methane and CWS diffusion flame, but Na* (589.45 nm), Li* (670.88 nm), K* (766.91, 770.06 nm), H* (816.04, 819.99 nm) radiation spectrum line and continuous black-body radiation have been detected only in the CWS flame. These differences can be used to characterize the combustion or gasification of CWS and distinguish whether CWS is ignited or not. In addition, the injection of CWS into methane flame leads to a significant reduction in OH* and an increase in C2* and CH* radiation intensity. This is because a lot of heat is absorbed in the processes of CWS combustion reactions. Then the generation of CH is inhibited, and the production of OH* is reduced. The increase of C2* and CH* is due to simple substance carbon produce more after injecting CWS. Besides, axial OH* radiation intensity increases at first then decreases, and the position of peak intensity is closer to outlet of hot oxygen burner compared with methane flames. Radial OH* radiation distribution is bimodal in methane flame because reactions take place in the thin layer where methane and oxygen meet. However, in CWS flame, radial OH* radiation distribution is always unimodal since CWS diffuses fiercely and mixes with oxygen sufficiently. As the ratio of oxygen atom to carbon atom ([O/C]e) increases, the reaction region of OH* radicals becomes larger in methane and CWS flame. This indicates that increasing oxygen can promote reactions and benefit OH* radicals' generation. Moreover, with the increase of CWS flow, reaction center is closer to burner outlet, OH* distribution range and peak intensity decrease obviously, CH*, C2*, Na*, Li*, K*, H* and black-body radiation intensities markedly rise. And these characteristics can reflect the changes of operation loads.
RESUMO
Rapid pyrolysis of rice straw (RS) and Shenfu bituminous coal (SB) separately, and rapid co-pyrolysis of RS/SB blends (mass ratio 1:4, 1:4, and 4:1), were carried out in a high-frequency furnace which can ensure both high heating rate and satisfying contact of fuel particles. Synergies between RS and SB during rapid co-pyrolysis were investigated. Intrinsic and morphological structures of residual char from co-pyrolysis, and their effects on gasification characteristics were also studied. Synergies occurred during rapid co-pyrolysis of RS and SB (RS/SB=1:4) resulting in decreasing char yields and increasing volatile yields. Synergies also happened during gasification of the char derived from co-pyrolysis of RS and SB with mass ratio of 1:4. The increased mass ratio of RS to SB did not only weaken synergies during co-pyrolysis, but significantly reduced the gasification rates of the co-pyrolysis char compared to the calculated values. Results can help to optimize co-conversion process of biomass/coal.