Principle of uniformity of temperature difference field in heat exchanger

A principle of uniformity of temperature difference field (TDF) in heat exchangers is advanced.It states that the more uniform the temperature difference field,the higher the effectiveness of heat exchanger for a given NTU and C,.Analytical and numerical results on the uniformity of TDF and effectiveness of thirteen types of heat exchangers show the validity of the uniformity principle.Its further verification is given by the asymptotical solution of TDF in terms of a recurrence formula of heat transfer area distribution.The analyses of entropy generation caused by heat transfer indicate that the uniformity principle is based on the second law of thermodynamics.Two ways,redistributing heat transfer areas and varying the connection between tubes,are presented for the improvement of the uniformity of TDF and the consequent increase of effectiveness for crossflow heat exchangers.     

Chemical composition of fuels and emissions from a coal + tire combustion experiment in a power station

Medium-sulfur bituminous coal and a mixture of 95 wt.% coal plus 5 wt.% tire-derived fuel (TDF) in the form of shredded automotive tires were combusted in a stoker boiler under the same conditions. This paper presents quantitative chemical compositions of the fuels and of the gaseous and particulate emissions. The coal + TDF mixture is considerably richer in Zn than the pure coal as a result of the high Zn content of the shredded tires (∼1 wt.% Zn). Atmospheric emissions of Zn increased from 15 g/h to nearly 2.4 kg/h when coal + TDF was combusted. Similarly, emissions of most other metals and metalloids, as well as those of HCl increased when TDF (∼3000 ppm Cl) was added. The enhanced metal emissions might be due to formation of gaseous metal chloride species in the stack gases. On the other hand, emissions of CO decreased slightly, whereas those of NO_x, SO₂, and total particulate matter remained virtually unchanged. These results help in assessing the environmental impact of energy recovery from scrap tires in stoker boilers.     

Kinetics of tire derived fuel (TDF) char oxidation and accompanying changes in surface area

The oxidation behavior of tire-derived fuel (TDF) char has recently been studied by several groups. In the present study, TDF char oxidation has been examined between 670 and 825 K, at oxygen partial pressures ranging from 2 to 19.8 kPa. The order of reaction with respect to oxygen varied with burnoff, and was in the range 0.72-0.86. The activation energy of reaction ranged with burnoff from 138 to 150 kJ/mol. The reaction rate does not correlate well with BET surface area, but did correlate well with the surface area in pores ranging in size from 1.2 to roughly 7 nm in width. Pores smaller than 1.2 nm exist in the char, but appear not to be used or developed by the oxidation reaction. Results for chars that have been acid washed to remove some inorganic matter show lowered reactivity, and a distinctly different pattern of pore development with burnoff. This is, in turn, reflected in a very different pattern of reactivity change with burnoff for such materials.     

水溶性膳食纤维聚葡萄糖含量检测方法的进展

新型水溶性膳食纤维聚葡萄糖不能被测定总膳食纤维(TDF)的AOAC方法985.29定量测定,从而影响了其推广应用。本文简要介绍了聚葡萄糖的结构特点,详细讨论了聚葡萄糖含量检测方法的沿革,并详细介绍了FCC方法和最新的能够把聚葡萄糖作为纤维测定的AOAC方法2000.11。     

Dietary fibre fractions in cereal foods measured by a new integrated AOAC method

The reliable determination of soluble, insoluble and total dietary fibre in baked goods and cereal flours is an important issue for research, nutritional labelling and marketing. We compared total dietary fibre (TDF) contents of selected cereal based foods determined by AOAC Method 991.43 and the new AOAC Method 2009.01. Fifteen bread and bakery products were included in the study. Our results showed that TDF values of cereal products determined by AOAC Method 2009.01 were always significantly higher than those determined by AOAC Method 991.43. This was explained by the inclusion of low molecular weight soluble fibre fractions and resistant starch fractions in the TDF measurement by AOAC 2009.01. This documents that nutritional labelling of cereal products poses the challenge how to update TDF data in nutrient databases in a reasonable time with an acceptable expenditure.     

时滞滤波器抑制残留振荡:理论、 方法及应用

回顾了时滞滤波器的发展背景和近年来的研究状况,介绍了对滞滤波器的各种设计方法和主要研究领域。时滞滤波器可从根本上避免激发对象的振动模态而消除残留振荡,在柔性结构系统中得到了广泛应用。最后 对时滞滤波器技术中存在的问题及未来的研究方向进行了探讨。     

Investigation into the removal of sulfur from tire derived fuel by pyrolysis

There is growing interest in the use of scrap tires as both a fuel and a feed material for petroleum feedstocks due to their abundance and their chemical composition. However, the sulfur content of scrap tires is a potential obstacle to scrap tires utilization as a fuel. In this paper, the partitioning of sulfur was investigated from the two major pyrolytic products from passenger car tires, liquid oils and solid chars, and the potential of producing a low sulfur char for fuel applications. The removal of sulfur during tire pyrolysis offers the greatest potential for the separation of sulfur products from the evolved gases and vapors. The influences of heating rate and pyrolysis temperature were investigated from 325 to 1000 °C, a range where substantial devolatilization occurs. The pyrolysis char and derived oil were analyzed for sulfur, and compared to the original parent sulfur content in tire derived fuel (TDF) samples. The results of sulfur determination verify that the overall desulfurization from the pyrolysis reaction is essentially unaffected by the heating rate but is affected by the ultimate pyrolysis temperature.     

不同类型分解炉分煤燃烧脱硝的改造和调试

中材水泥有限责任公司生产线主要的分解炉炉型有TTF型、TDF型、RSP型，他们对其均进行了分煤燃烧的脱硝改造，文章对其主要改造内容和效果进行了分析总结。