1、翻译部分英文原文Influence of temperature on coal sorption characteristics and the theory of coal surface free energyLei Zhang,Naj Aziz,Ting X Ren, Zhongwei WangUniversity of Wollongong, Wollongong, NSW 2500, AustraliaAbstract:An experimental study was undertaken to examine the sorption and desorption charac
2、teristics of coal at temperatures of 35 C, 45 C and 55 C. The study focused on the effect of changes in temperature and coal particle sizes on gas sorption and desorption characteristics. The coal size used ranged from fragmented coals, 16 mm, 8 mm, 2.4 mm, powdered coal of 150 m and 54 mm core samp
3、les. The samples were tested in pressure vessels, known as “bombs”, charged with CO2 gas at different pressure levels up to a maximum of 4000 kPa. It was found that temperature has a significant influence on the sorption and desorption behavior of gas in coal. The degree of hysteresis phenomenon was
4、 found to be influenced by the coal surface area as well as temperature. Based on the principle of surface chemistry, the method of calculating coal surface energy with sorption parameters was used and the main parameter of surface tension was analysed. The calculation result showed that reduced val
5、ue of surface tension parameter decreased with increasing temperature. Also the reduced value of surface tension parameter of adsorption is smaller than the desorption. The theory of coal surface free energy can be used to explain the coal sorption characteristics with CO 2 at higher temperatures. R
6、esults from this study have useful implication for enhanced CBM and gas drainage in coal mines.1. IntroductionGas sorption in coal has been studied over the years by many researchers 1, 2, 3, and in recent years, the coal sorption characteristics at high temperatures, beyond the normal temperature o
7、f 20 29 C, have been identified as an attractive option which can shed light on the behaviour of gas sorption in and desorption from coal in situ, especially when mining is taking place at increasingdepth.Lama and Bodziony 4 reported that the term “sorption” consists of two parts: adsorption and abs
8、orption. Adsorption refers to the accumulation of gas on the surfaces of pores and cracks and absorption means the penetration of gas into the internal structure of coal. Sorption is an exothermic process and is opposite to desorption, which is endothermic. Studies reported by Moffat and Weale5; Yan
9、g and Saunders 6; Stevenson et al. 7, cited by Lama and Bodziony 4, indicated that the heat of sorption is less than two or three times the heat of desorption/ vaporisation.Siemons and Busch 8 measured CO2 sorption isotherms on both dry and moist coals of various ranks from coal basins from around t
10、he world and these measurements were made in temperature of 45 C. Day et al. 9 carried out experiments on supercritical gas sorption of carbon dioxide on moist coals at temperatures of 21 C and 55 C and pressures up to 20 MPa. The differences of gas content due to different temperatures were not com
11、pared and the samples for the experiment were prepared by crushing and screening fresh air-dried lumps of coal to a particle size range of 0.5 1.0 mm.Jun 10 reported that the changes of surface free energy of coal was the most important reason when different rank of coal sorbed different quantity of
12、 gas. Based on the principle of surface chemistry, coal surface free energy which indicates the interaction capacity between the coal surface and gases can be calculated. In his study, Jun found that the coal surface free energy is related to the rank of coal.2. Experimental2.1. ApparatusThe indirec
13、t gravimetric method was used to calculate the volume of gas adsorbed and desorbed from coal. The gas sorption apparatus shown in, has been described previously by Aziz and Ming-Li 11 and Lei et al. 12. In this apparatus, each vessel, known as “bomb”, has its own pressure transducer so that the sorp
14、tion process and changes in bomb pressure can be readily determined. The equipment has since been further modified to accommodate increases in temperature up to 100 C. The addition of a heat isolation jacket outside the water bath as well as the insulation cover enabled the coal bombs to maintain th
15、e desired experimental temperature with an accuracy of 0.1 C. the gas sorption apparatus shown as Fig. 1.Fig. 1. Schematic diagram of the gas sorption apparatus.2.2. Coal sample preparationThe coal samples used in the study were collected from longwall panel 520, Area 5, West Cliff Colliery. Details
16、 of the coal samples are shown in Table 1 and Table 2 13. The coal core samples were prepared according to the International standard of rock core sample preparation 14. In addition to coal cores, larger coal lumps were freshly dug out of the development headings. They were wrapped in plastic sheets and taken to the laboratory where they were immersed in water tanks to minimise oxidation and adverse environmental effe
