Hirofumi Tsuji

Effects of moisture in coal on pulverized coal combustion characteristics

Effects of moisture in coal on pulverized coal combustion characteristics are investigated by means of a three-dimensional numerical simulation. The results show that as the moisture increases, flame temperature and NOx mole fraction decrease, while O2 mole fraction increases in the region near the burner, and the peaks of the flame temperature and NOx mole fraction shift downstream. Also, the increase in the moisture increases the unburned carbon fraction and decreases the NOx conversion at the outlet of the furnace. These trends agree well with the previous experimental results. It is found that the contribution of thermal NOx to the total NOx drastically decreases with an increasing moisture content, whereas the emission of fuel NOx increases.

Observation of detailed structure of turbulent pulverized-coal flame by optical measurement - (Part 2, instantaneous two-dimensional measurement of combustion reaction zone and pulverized-coal particles)

The purpose of this study is to elucidate of the primary air combustion zone in pulverized-coal combustion by means of advanced laser-based diagnostics with high temporal and spatial resolutions. An open-type burner is fabricated to apply various optical measurement techniques. In this paper, simultaneous measurement of OH-planar laser-induced fluorescence (PLIF) and Mie scattering images of pulverized-coal particles is performed, and the spatial relationship between the combustion reaction zone and the pulverized-coal particle zone is examined. It is found that, in the upstream region, combustion reaction occurs only in the periphery of the clusters of pulverized-coal particles where the high-temperature burnt gas of a methane pilot flame is entrained and oxygen supply is sufficient, and that, in the downstream region, however, combustion reaction can be seen also within the clusters of pulverized-coal particles. This is because, in the downstream region, the devolatilization process of the coal particles proceeds with the temperature rise of the particles, and the mixing process between the volatile matters and ambient air is prompted. From these results, it can be said that the present diagnostic techniques are effective for evaluating the pulverized-coal flames.

Classification and collection of fine particles by means of backward sampling

Abstract Due to human activities, such as the combustion of fossil fuels, the influence on our environment of particulate matter (PM), including aerosols, is being investigated by many research organizations. In particular, fine particles have become very important because they are major components of suspended particulate matter (SPM). Therefore, it is very important to collect fine particles from the exhaust ducts of industrial facilities. Although the method for sampling fine particles less than 2.5 μm (PM 2.5 ) from ambient air has been established by the United States Environmental Protection Agency (EPA), a method for fine particles in exhaust ducts has not been proposed. In this study, a collection method of fine particles by means of backward sampling, in which the sampling probe is aligned at 180° to the main stream velocity, is proposed. This method is investigated numerically and experimentally. The sampling efficiency of backward sampling is calculated by a numerical simulation method under various sampling conditions and an equation, which predicts the sampling efficiency, is derived. The accuracy of this equation is confirmed by measurement of the sampling efficiency in an exhaust duct of a pulverized coal combustion test furnace. By use of this equation, an investigation is made to elucidate the conditions in which the fine particles can be effectively classified.

New Estimation Method of Particle Size Distribution by Anisokinetic Sampling.

固気二相流中の粒径分布の測定は, 粉体プロセスの性能管理, 排煙中の粒子状物質の性状評価などにおいて, 極めて重要な操作である.従来の測定法では, 等速吸引によりサンプリングを行い, その後, 複雑な分級器を用いて粒径分布が計測されていた.本論文は, 非等速吸引による濃度測定誤差が粒子径によって異なることを粒径分布測定に利用する技術について検討したものである.非等速吸引の際の流速比 (主流流速の吸引流速に対する比率) が, 測定濃度と直線関係を持つことから容易に真濃度が求められ, また当然, 流速比は濃度比 (測定濃度の真濃度に対する比率) とも直線関係を持ち, その傾きは粒径分布によって異なる.本技術は, この概念を粒径分布測定に応用したもので, フライアッシュ, 灯油燃焼ばいじんなどについて測定した結果, 従来法と良い一致を示し, 十分な測定精度を有していることが明らかになった.