Enhancement of combustion efficiency with mixing ratio during fluidized bed combustion of anthracite and bituminous blended coal

In order to investigate the effect of mixing ratio of bituminous coal to blended coal on the enhancement of combustion efficiency, combustion experiments of blended coal with anthracite and bituminous are done in a laboratory scale fluidized bed combustor (10.8 cm ID and 170 cm height). The gross heating values of anthracite and bituminous coal used in this study are 2,810 cal/g and 6,572 cal/g, respectively. Experimental parameters are fuel feed rate, superficial gas velocity and mixing ratio of bituminous coal to blended coal. The combustion efficiency increases with the mixing ratio of bituminous coal due to the lower unburned carbon losses and higher burning velocity of bituminous coal. The rate of combustion in the combustor was increased with mixing ratio resulted from a higher burning velocity of bituminous coal. The measured combustion efficiency experimentally is about 3.5-12.4% higher than that of the calculated value based on the individual combustion of anthracite and bituminous coal under the same operating conditions. The optimum mixing ratio (MR) of bituminous coal determined is around 0.75 in this study. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 1. The basic characteristics of HCCI combustion

This article investigates the basic combustion parameters including start of the ignition timing, burn duration, cycle-to-cycle variation, and carbon monoxide (CO), unburned hydrocarbon (UHC), and nitric oxide (NO_x) emissions of homogeneous charge compression ignition (HCCI) engines fueled with primary reference fuels (PRFs) and their mixtures. Two primary reference fuels, n-heptane and iso-octane, and their blends with RON25, RON50, RON75, and RON90 were evaluated. The experimental results show that, in the first-stage combustion, the start of ignition retards, the maximum heat release rate decreases, and the pressure rising and the temperature rising during the first-stage combustion decrease with the increase of the research octane number (RON). Furthermore, the cumulative heat release in the first-stage combustion is strongly dependent on the concentration of n-heptane in the mixture. The start of ignition of the second-stage combustion is linear with the start of ignition of the first-stage. The combustion duration of the second-stage combustion decreases with the increase of the equivalence ration and the decrease of the octane number. The cycle-to-cycle variation improved with the decrease of the octane number.     

K- and Cs-FeV/Al2O3soot combustion catalysts for diesel exhaust treatment

Alkali-doped FeV oxide catalysts supported on -alumina were prepared and their catalytic activity in the combustion of diesel soot is reported. The catalysts were characterized by XRD, TPR and SEM–EDX analysis. The influence of the nature of the alkali metal (K and Cs), the temperature of treatment of the catalysts and the stability to sulfur poisoning have been investigated.

Catalysts doped with Cs were the most active and stable also after several combustion cycles and in the presence of sulfur in the stream. The activity measurements and microstructural results suggest that the combustion of soot is favored on catalysts where amorphous phases and/or mixed Fe---V---O phases, ensuring an intimate contact between iron and vanadium, are present. A reaction mechanism involving the participation of the redox couple Fe(II)–Fe(III) in the activation of the vanadium combustion sites, is proposed.     

Ethanol combustion over strontium- and cerium-doped LaCoO3 catalysts

Ce- or Sr-doped LaCoO₃ bulk perovskites were prepared by citric acid method as well as 10 wt.% of LaCoO₃ was deposited on alumina carrier stabilized with lanthanum. Properties of prepared materials were characterized by determination of surface area, acid-basic properties and XRD, XPS, TPDO₂, H₂-TPR measurements as well as catalytic activity and selectivity for ethanol combustion was tested. It was found that substitution of La in LaCoO₃ with either Sr or Ce has only small effect on its activity in ethanol combustion. Strontium inserted into LaCoO₃ structure increases basic character of the perovskite surface as well as selectivity to acetaldehyde (ACA). Substitution of La with cerium has no effect on the concentration of basic sites and does not affect the selectivity to ACA. Activity of LaCoO₃-based catalysts in ethanol combustion and their selectivity to ACA formation can be explained on the basis of the presence of both -oxygen species and sites with basic character on the material surface.

Acid-basic properties of supported LaCoO₃ are dominated by acidic character of the carrier. Results of XPS and H₂-TPR measurements of LaCoO₃ supported on La–Al₂O₃ suggest that perovskite remains in strong interaction with carrier and probably is partially decomposed. Deposition of perovskite on stabilized carrier significantly increases the rate of ethanol combustion.     

Evolution of chemistry and morphology during the carbonization and combustion of rice husk

Both fine carbon/silica and pure silica powders can be obtained by carbonization and combustion of rice husk under non-isothermal conditions, and the products can be used for preparation of high-quality ceramic materials. Studies on the morphology, chemical and physical characteristics of products were carried out by N₂-adsorptionmeter, SEM, XRD, FTIR, ICP-MS and EA. Results indicate that decreasing the heating rate increased the specific surface area, pore volume and pore diameter. At a heating rate of 5 °C/min, the specific surface areas of both the carbon/silica and pure silica powders were 261 and 235 m²/g, and the average pore diameters were 2.2 and 5.4 nm, respectively. The products obtained from various heating rates were all amorphous. Thermogravimetric analysis was employed to study the reaction characteristics during carbonization or combustion, indicating that decomposition process of rice husk could be divided into three temperature zones. This results of the study can also provide the important information on the recovery of biomass material from rice husk.     

超细CaCO3与金属氧化物M2O3对Al/AP/HTPB推进剂燃烧的催化协同效应研究

对超细及市售ＣａＣＯ３在低含量（≤１％）的情况下对丁羟推进剂燃烧性能的影响进行了研究，结果发现ＣａＣＯ３低含量时可提高推进剂的燃速且超细ＣａＣＯ３比市售ＣａＣＯ３的催化效率高。进一步研究了超细ＣａＣＯ３与金属氧化物Ｍ２Ｏ３组合对推进剂燃烧的催化作用，结果表明两者有协同效应，其组合的燃烧催化效果较各自单独使用的催化效果要好。     

The structures of VOx/MOx and alkali-VOx/MOx catalysts and their catalytic performances for soot combustion

Vanadium oxides supported on γ-Al₂O₃, SiO₂, TiO₂, and ZrO₂ were studied on their molecular structures and reactive performances for soot combustion. To investigate the effect of different alkali metals on the structures and reactivities of supported-vanadium oxide catalysts, they were doped into the V₄/TiO₂ catalyst which had the best intrinsic activity for soot combustion in the selected supported vanadium oxide catalysts. The experimental results demonstrated that the catalytic properties of these catalysts depended on the vanadium loading amount, support nature, and the presence or the absence of alkali metals. The spectroscopic analysis (FT-IR and UV–vis) and H₂-TPR results revealed that the higher activity of alkali-promoted vanadium oxide catalysts could be related to the ability of alkali metal promoting the redox cycle of the active vanadyl species. TG results showed that adding alkali to V_m/TiO₂ catalyst was beneficial to lowering their melting points. Low melting points could ensure the good surface atom migration ability, which would improve the contact between the catalyst and soot. Due to the alkali metal components promoting the redox ability and the mobility of the catalysts, alkali-modified vanadium oxide catalysts could remarkably improve their catalytic activities for soot combustion. The catalytic activity order for soot combustion followed Li > Na > K > Rb > Cs in the catalyst system of alkali-V₄/TiO₂, and the reason why it followed this sequence was discussed.     

煤炭复合型助燃固硫剂的开发与研究

通过对不同粒径煤样的全硫量及黄铁矿硫量的测试分析,以及在燃烧过程中生成酸性气体,从而选用复合型碱性固硫剂来进行固硫试验。通过对这几种试验方案的优选比较分析,确定按煤90%∶CaO 9%∶NaCl 1%的配方脱硫率高且成本低廉,可适合工业化生产使用。同时,用高精度微机全自动量热仪做上述配方的煤燃烧热效率实验,结果表明,煤热效率有明显的提高。这说明复合型碱性添加剂不但可促进煤炭的燃烧,同时在燃烧的过程中取到固硫的作用。     

阻燃剂对软质聚氨酯泡沫燃烧特性的影响

利用锥形量热仪对添加了不同阻燃剂的软质聚氨酯泡沫，在25kW／m^2下，其热释放速率、产烟量、一氧化碳产生量、二氧化碳产生量和点燃时间等进行了试验研究。结果表明，含氯化铵的聚氨酯泡沫燃烧时热释放速率最小，仅是未经阻燃处理的聚氨酯泡沫的热释放速率的11．5％；含硫酸铵的聚氨酯泡沫的产烟量最少，仅是未经阻燃处理的聚氨酯泡沫的产烟量的6．4％；含氯化铵的聚氨酯泡沫燃烧时产生的一氧化碳和二氧化碳都是最少的，分别是未经阻燃处理的聚氨酯泡沫的2，4％和1．6％；点燃时间最长的是含四硼酸钠的聚氨酯泡沫，几乎是未经阻燃处理的聚氨酯泡沫的15倍，其它阻燃剂对聚氨酯泡沫的燃烧性能都有不同程度的影响。     

煤质分析报告与燃烧计算

燃烧计算所需要的工作质的碳、氢、氧、氮、硫、灰分和水分7项成分的煤质分析数据,一般的煤质分析报告提不出来。本文作了某些简化的、近似的工程处理。计算出“空气干燥基”的上述7项成分数值,用以代替常用的工作基成分,通过实例计算,发现能很好地与实际情况相符合,提示这种工程处理在实用上的可行性。