A study of the properties of carbon foam reinforced by clay

A novel carbon foam with high strength and very low thermal conductivity was prepared by thermal treating of coal tar based mesophase pitch mixed with montmorillonite clay. SEM observation showed that less micro-cracking appeared on the cell wall of foam by adding of clay-montmorillonite. Foam mechanical properties were improved and its thermal conductivity was markedly decreased. The compressive strengths were increased by 64%, 96% and 100% when the additive amounts of clay were 2%, 5% and 10% (wt%), respectively. Due to the high thermal insulation and lamellar structure of clay, the thermal conductivity of carbon foam decreases from 2 W/m K to 0.25 W/m K.     

Preparation of zinc ferrite in the presence of carbon material and its application to hot-gas cleaning

In order to develop an efficient absorbent of H₂S in coal gasification, zinc ferrite (ZnFe₂O₄) was prepared in the presence of carbon materials such as activated carbon (AC), activated carbon fiber (ACF), and Yallourn coal (YL). The absorption behavior of absorbents for H₂S was examined using a fixed-bed flow type reactor equipped with a quadrupole mass spectrometer.Carbon material-supported ZnFe₂O₄ exhibited larger desulfurization capacity for H₂S than unsupported ferrites. They could efficiently remove H₂S from 4000 ppm levels in a simulated coal gasification gas to less than 1 ppm at 500 °C. The absorption capacity of H₂S with ZnFe₂O₄/AC, ZnFe₂O₄/ACF, and ZnFe₂O₄/YL exhibited nearly 100% of stoichiometric amount of loaded metal species. They could be regenerated by an air oxidation in O₂-Ar (50 vol%) at 450 °C for 30 min. The regenerated ferrite can be used for repeated absorption of H₂S with a very slight decrease in the absorption capacity.     

FORMATION AND FLOW OF GAS BUBBLES IN A PRESSURIZED BUBBLE COLUMN WITH A SINGLE ORIFICE OR NOZZLE GAS DISTRIBUTOR

The characteristics of gas bubbles in a 5 cm diameter bubble column equipped with a single orifice of 1,3 or 5 mm diameter were investigated under system pressure of 0.1-15 MPa. The formation of gas bubbles was strongly affected by the system pressure. Under high pressures a dispersed gas jet was formed at gas velocities where spherical gas bubbles would have been formed at atmospheric pressure. The critical gas velocity between the bubbling regime and the jetting regime was correlated with the liquid phase Weber number and the gas phase Reynolds number based on the gas velocity at the orifice. Bubble size and gas holdup in the main part of the bubble column were also affected by the bubble formation pattern at the distributor     

蒸发段长度与充液量对高温钠热管启动过程的影响

通过对 7根结构参数不同、充液量不同的高温钠热管进行实验研究 ,给出各种情况下高温钠热管启动过程中温度随时间变化曲线 ,分析了蒸发段长度的变化及充液量的变化对高温钠热管启动过程的影响。实验结果表明直径为 2mm ,长 1 0 0 0mm的钠热管 ,蒸发段长度为 5 80mm且充有 78～ 90 g左右的充液量 ,其启动运行工作为最佳     

Sulfur transformation during rapid hydropyrolysis of coal under high pressure by using a continuous free fall pyrolyzer☆

The behavior of sulfur transformation during rapid hydropyrolysis of coal was investigated using a pressurized, continuous free fall pyrolyzer under the conditions of temperature ranging from 923 to 1123 K and hydrogen pressure up to 5 MPa. The yields of sulfur converted to gas, tar and char were determined, together with the analyses of sulfur form distributions in coals and chars. The results showed that the decomposition of inorganic sulfur species was affected only by the temperature, while the increases in temperature and hydrogen pressure obviously enhanced the removal of organic sulfur from coal. The extent of organic sulfur removal was proportional to the coal conversion, depending on coal type. A significant retention of gaseous sulfur products by the organic matrix of the char was observed during hydropyrolysis of a Chinese coal above 1023 K, even under the pressurized hydrogen atmosphere. The kinetic analysis indicates that the rate of organic sulfur removal from coal was 0.2th-order with respect to the hydrogen pressure, and the activation energy for total sulfur removal and organic sulfur removal is 17-26 and 13-55 kJ/mol, respectively. The low activation energies suggest that the transformation and removal of sulfur from coal might be controlled by the diffusion and/or thermodynamic equilibrium during hydropyrolysis under the pressurized conditions.     

Numerical study of coal particle cluster combustion under quiescent conditions

Behavior of ignition and combustion of coal particle cluster under a quiescent condition was numerically simulated by solving balance equations of mass and enthalpy with combustion kinetic models of volatiles and char. Two-flame structure, one flame penetrating into the cluster and the other moving out of the cluster, was predicted during the combustion of coal particle cluster. Effects of radiative heat transfer, group number, ambient temperature, coal particle size, and oxygen concentration on ignition and combustion of coal particle clusters were also analyzed. Simulations indicated that the gas volume fraction of coal particle cluster increases with time after devolatilization. Gas velocity passing through the cluster surface varied significantly at volatile liberation. The ignition time delay was reduced with the increase of ambient temperature. The cluster devolatilization rate and char burning rate increased while the ignition time delay decreased with the increase of ambient oxygen concentration.     

煤矸石混合材对标准稠度影响的灰色关联分析

利用灰色关联分析的数学方法,对利用煤矸石作水泥混合材所产生的标准稠度用水量改变的影响,做了分析。论述了不同细度水泥条件下,煤矸石粒径分布范围对水泥需水量的影响。发现了在水泥较细时,在粒径范围<5 μm下的煤矸石颗粒,对标准稠度用水量影响最大;在水泥较粗时,粒径范围在5～10 μm下的煤矸石颗粒,对标准稠度用水量影响最大。     

烧劣质低挥发分燃料700t/d预分解窑的综合优化改造

七里岗水泥厂700t／d预分解窑使用劣质低挥发分煤时，熟料产量仅619t/d。对窑系统热工检测和诊断后，对预热预分解系统进行了个性化技改，72h达标考核期间熟料平均产最达到918t／d。     

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.     

焦化柴油不安定因素考察

对焦化柴油的不安定因素进行了研究.通过研究发现,焦化柴油中的酸性物质、碱性物质、微量金属及可见光均是影响焦化柴油安定性的因素,空气对焦化柴油的安定性影响较小.