氧体积分数对炭黑燃烧特性影响的热天平研究

Thermogravimetric study of the effect of oxygen concentrations on combustion characteristics of natural gas soot

利用热天平对天然气扩散火焰中生成的炭黑在不同氧体积分数下(21%、15%、10%和5%)的燃烧特性进行了研究,选用蜡烛炭黑、4种工业炭黑以及无烟煤焦炭作为对比。基于试验结果确定了燃烧特性参数,并分析了燃烧特性。天然气扩散火焰中生成的炭黑明显早于其他试样着火燃烧,着火温度在所有试样中最低,氧体积分数为21%下为483.0℃,比焦炭约低114℃,比蜡烛炭黑低近127.8℃。自制天然气炭黑可燃指数比焦炭低,着火后前期燃烧反应能力较弱。随着氧体积分数的降低,各试样着火温度在50℃内变化。比较各试样的燃尽特性可知自制天然气炭黑在不同燃尽率下的相对燃尽时间最长,氧体积分数为21%下完全燃尽为6.03min,比焦炭长21.3%。蜡烛炭黑相对燃尽时间也较长。随着氧体积分数降低,各试样燃尽时间都延长,尤其是自制天然气炭黑,氧体积分数从21%降到5%,相对燃尽时间延长2.97倍,氧体积分数降低明显延长其燃尽过程。

The combustion characteristics of soot generated in natural gas diffusion flame （home-made natural gas soot, NGS ） were investigated using thermogravimetric analysis under different oxygen concentrations （21%, 15%, 10% and 5% ）, and compared with those of candle soot, 4 industrial NGS and one anthracite coke. The combustion characteristic parameters of the test samples can be achieved through data analysis. The results show that NGS sample has better ignition features and lower ignition temperature than other NGS samples and the coke with the low volatile matter. Under oxygen concentration of 21% the ignition temperature of home-made NGS is 483.0℃ which is 114 ℃ and 127.8 ℃ lower than those of the coke and the candle soot, respectively. The burning index （ （ dG/dt ） max/ ti^2 ） of home-made NGS is lower than that of coke due to its high volatile matter. The combustion reactivity of home-made NGS is weak in the late combustion stage. With decreasing oxygen concentration the ignition temperatures of samples change within 50 ℃. The relative burn-out time of home-made NGS is longest, 6.03 min under 21% oxygen concentration, which is 21.3% longer than that of coke. The difference of burn-out property between home-made NGS and coke is small. The burn-out time of candle soot is also long due to the small particle size of the soot. With decreasing oxygen concentration the burn-out times of the samples are prolonged. For home-made NGS the burn-out time is 2.97 times longer when oxygen concentration decreases from 21% to 5%.