臺灣博碩士論文加值系統

本研究的主要目的, 在以實驗方法探討不同種揮發物含量的單一毫米尺寸
煤粒於熱對流流場中引燃與燃燒的現象. 本文以改變煤炭的種類, 氣流之
溫度(900-1100K),流速(0.1-1.3 m/s),煤粒直徑(7.5-14mm)和氧濃
度(11- 31%)的方式來了解以上參數對於熱解與燃燒速率, 引燃時間, 熄
滅時間,和引燃位置的影響及它們之間互動的關係. 本文主要的結論如下:
當引燃位置發生在煤粒之前端和側邊時, 在相同的煤粒直徑下, 煤粒的引
燃時間隨拉伸率的增加而有先下降後上升的現象, 而存在最短的引燃時
間 , 低於此時間所對應的臨界流速的區域稱為熱解控制區域, 反之為氣
相反應控制區域. 在相同的條件下, 高揮發物含量的煤炭引燃時間較短,
且其臨界流速較低. 當引燃位置發生在尾流區時, 隨著流速的增加引燃時
間呈現上升, 下降而又上升的現象. 無論引燃的位置為何, 在其他條件固
定的情況下煤炭的熄滅時間和引燃時間隨著流速的改變均有相同的變化趨
勢,而且火焰燃燒時間均隨著流速的提高而縮短, 其關係接近直線. 在溫
度 1000 K, 流速0.7m/s的條件下, 印尼煤 (揮發物含量42.07%) 和美南
煤 (揮發物含量33.87%) 因為介於熱解控制區域和反應控制區域之間, 煤
粒的引燃時間幾乎不隨煤粒直徑的不同而改變, 而澳洲煤 (揮發物含
量25.60% ) 則因為在熱解控制區域之中, 引燃時間隨粒徑增加而增長.
引燃位置和氣相區反應速率及自由流速度有關. 在本實驗中, 當其他條件
固定時, 煤炭揮發物含量或溫度較高者, 引燃位置較靠近停滯點.

The purpose of this study is to investigate the ignition and
the combustion of different kinds of single coal particle in
the convective flow field. The parameters of this experiment
contain coal types, free stream temperatures(900-1100K), free
stream velocities(0.1-1.3m/s), the diameters of coal particles
(7.5-14 mm) and oxygen concentration(11-31%). The combustion
rates, ignition times, extinction times and ignition position
are measured.When the ignition happened at the front half of
coal particle in the same diameter, the ignition times decrease
first and then increase as the flow velocities increase. The
lower velocities range up to the minimum point corresponds to a
pyrolysis-control region. At high velocities above the minimum
point, the pyrolysis-control region changes to a reaction-
control region. At the same condition, the ignition time of
high volatile coals is shorter, and its critical flow
velocities are lower. When the ignition happened in the wake
region of coal particles, the ignition times increase, decrease
and then increase. No matters where the ignition position
happened, the extincton and ignition times vary in the same
trend as the velocities change. The flame combustion times are
also decrease linearly as the velocities change. In our
experiment conditions, the ignition times of high volatile
coals are linearly constants as the particle size change
because they are between the pyrolysis-control region and
reaction-control region. The low volatile coals are in
pyrolysis-control region, and the ignition times lengthen as
the particle size increases. The ignition position depends on
the gas-phase reaction rates and free stream velocities. In our
experiment,the ignition position near the stagnation point as
the volatiles and temperatures increase.