scholarly journals Experimental study of the moisture content influence on CH4 adsorption and deformation characteristics of cylindrical bituminous coal core

2018 ◽  
Vol 36 (7-8) ◽  
pp. 1512-1537 ◽  
Author(s):  
Dingyi Hao ◽  
Lei Zhang ◽  
Mingxue Li ◽  
Shihao Tu ◽  
Cun Zhang ◽  
...  
Keyword(s):  
Moisture Content ◽  
Adsorption Capacity ◽  
Exponential Decay ◽  
Coal Mine ◽  
Bituminous Coal ◽  
Gas Adsorption ◽  
Decay Function ◽  
Exponential Decay Function ◽  
Adsorption Deformation ◽  
Original Moisture

Moisture content in coal is an important factor affecting the coal seam gas extraction. It directly affects the storage and flow of gas in bituminous coal. In this paper, the cylindrical bituminous coal cores of Xutuan coal mine in Huaibei coal mine group were studied as experimental objects, using the laboratory self-designed experimental device Gas Adsorption and Strain Testing Apparatus system. The influence of the bituminous coal moisture content on gas adsorption characteristics was studied. Drying experiments of coal samples showed that they lose the original moisture content following the exponential decay function of time. At wetting, the saturated moisture content in coal samples increased following the Exponential Association function of time. The experimental results show that the average original moisture content and average saturated moisture content of raw coal samples are 1.3 and 2.4%, respectively. On this basis, the gas adsorption experiments on samples with different moisture contents under different gas pressures were carried out. With the moisture content increase, the gas adsorption capacity and saturation value decreased and the decrease rate gradually reduced. The single exponential decay function describes the gas adsorption capacity dependence on moisture content. Moisture content also affects the adsorption deformation of bituminous coal. At high moisture content, the adsorption deformation of bituminous coal is less.

scholarly journals The binary gas sorption in the bituminous coal of the Huaibei Coalfield in China

2018 ◽  
Vol 36 (9-10) ◽  
pp. 1612-1628 ◽  
Author(s):  
Lei Zhang ◽  
Zhiwei Ye ◽  
Mingxue Li ◽  
Cun Zhang ◽  
Qingsheng Bai ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Sorption Capacity ◽  
Bituminous Coal ◽  
Gas Adsorption ◽  
Langmuir Equation ◽  
Separation Coefficient ◽  
Gas Sorption ◽  
Langmuir Adsorption ◽  
Gas Molecules ◽  
Huaibei Coalfield

Knowledge of the gas sorption characteristics of a coal not only helps to explain the mechanism of enhanced coalbed methane recovery but also provides an important basis for simultaneous coal and gas extraction. In consequence, the pure and binary gas excess sorption capacity of methane, carbon dioxide, and nitrogen of bituminous coal samples derived from the Xutuan Coal Mine in Huaibei coalfield, in Anhui Province in China, was measured using the volumetric method. The fitting analysis of the pure gas Langmuir adsorption model was carried out. The binary gas excess sorption measurement showed that the final sorption capacity of bituminous samples was the same no matter what the gas adsorption order of competitive adsorption and displacement adsorption. Hence, coal gas adsorption is physical adsorption, i.e. the different adsorption and desorption process of gas molecules does not affect the final adsorption amount of coal to each component of gas. Using the fitting parameters obtained by the Langmuir equation, the extended Langmuir equation was used to predict the adsorption capacity for each component of the binary gas. The comparison between predicted adsorption capacity and measured adsorption capacity showed that the extended Langmuir equation can better describe the trend of the adsorption isotherm curves of a binary gas under different pressures. The separation coefficient and displacement coefficient were defined from Langmuir adsorption theory. The separation coefficient involves the proportion of each component in the free phase and the proportion of each component in the adsorption phase. The displacement coefficient involves the displacement ability of gas molecules at adsorption sites by free gas molecules.

scholarly journals Retinal Degeneration in Choroideremia follows an Exponential Decay Function

Ophthalmology ◽  
2018 ◽  
Vol 125 (7) ◽  
pp. 1122-1124 ◽  
Author(s):  
James W. Aylward ◽  
Kanmin Xue ◽  
Maria I. Patrício ◽  
Jasleen K. Jolly ◽  
Jonathan C. Wood ◽  
...  
Keyword(s):  
Retinal Degeneration ◽  
Exponential Decay ◽  
Decay Function ◽  
Exponential Decay Function

scholarly journals The influence factors for gas adsorption with different ranks of coals

2017 ◽  
Vol 36 (3-4) ◽  
pp. 904-918 ◽  
Author(s):  
Deyong Guo ◽  
Xiaojie Guo
Keyword(s):  
Moisture Content ◽  
Specific Surface ◽  
Pore Structure ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Gas Adsorption ◽  
Total Pore Volume ◽  
Factors Influencing

In this paper, scanning electron microscopy, low-temperature N2 adsorption and CH4 isothermal adsorption experiments were performed on 11 coal samples with Ro,max between 0.98 and 3.07%. The pore structure characteristics of coals (specific surface area, total volume distribution) were studied to assess the gas adsorption capacity. The results indicate that there is significant heterogeneity on coal surface, containing numerous channel-like pores, bottle-shaped pores and wedge-shaped pores. Both Langmuir volume (VL) and Langmuir pressure (PL) show a stage change trend with the increase of coalification degree. For different coalification stages, there exist different factors influencing the VL and PL values. For low-rank coals (Ro,max < 1.1%), the increase of VL values and decrease of PL values are mainly due to the abundant primary pore and fracture within coal. For middle-rank coals (1.1% < Ro,max < 2.1%), the moisture content, vitrinite content and total pore volume are all the factors influencing VL, and the reduction of PL is mainly attributed to the decrease of moisture content and inertinite content. Meanwhile, this result is also closely related to the pore shape. For high-rank coals (Ro,max > 2.1%), VL values gradually increase and reach the maximum. When the coal has evolved into anthracite, liquid hydrocarbon within pore begins pyrolysis and gradually disappears, and a large number of macropores are converted into micropores, leading to the increase of specific surface area and total pore volume, corresponding to the increase of VL. In addition, the increase of vitrinite content within coal also contributes to the increase of VL. PL, reaches the minimum, indicating that the adsorption rate reaches the largest at the low pressure stage. The result is mainly controlled by the specific surface area and total pore volume of coal samples. This research results will provide a clearer insight into the relationship between adsorption parameters and coal rank, moisture content, maceral composition and pore structure, and it is of great significance for better assessing the gas adsorption capacity.

Time resolved fluorescence of aqueous tryptophan

1978 ◽  
Vol 56 (5) ◽  
pp. 743-745 ◽  
Author(s):  
D. M. Rayner ◽  
A. G. Szabo
Keyword(s):  
Exponential Decay ◽  
Emission Spectra ◽  
Fluorescence Decay ◽  
Time Resolved Fluorescence ◽  
Decay Function ◽  
Time Resolved ◽  
Exponential Decay Function

The fluorescence decay of aqueous tryptophan is shown to be described by a two exponential decay function whose components have life-times of 3.14 ns and 0.51 ns. These components are assigned as the solvent equilibrated 1La and 1Lb, states respectively. The time-resolved emission spectra are presented and can be resolved into two spectra with λmax at 350 nm and 335 nm corresponding to these two states.

A new method of determining brightness and size of cometary nuclei

2020 ◽  
Vol 492 (3) ◽  
pp. 4175-4188 ◽  
Author(s):  
Mieczyslaw Leszek Paradowski
Keyword(s):  
Bulk Density ◽  
Exponential Decay ◽  
Linear Dependence ◽  
New Method ◽  
Nuclear Density ◽  
Decay Function ◽  
Cometary Nuclei ◽  
Exponential Decay Function ◽  
Visual Magnitude ◽  
The Mean

ABSTRACT This paper presents a new method of determining the brightness and size of cometary nuclei that has been applied to the following 32 observed comets: 2P/Encke, 29P/Schwassmann-Wachmann 1, 102P/Shoemaker 1, 103P/Hartley 2, 168P/Hergenrother, 189P/NEAT, 260P/McNaught, 315P/LONEOS, P/2012 NJ (La Sagra), P/2013 J2 (McNaught), C/2006 S3 (LONEOS), C/2009 P1 (Garradd), C/2010 S1 (LINEAR), C/2010 X1 (Elenin), C/2011 J2 (LINEAR), C/2011 L4 (PANSTARRS), C/2011 W3 (Lovejoy), C/2012 F6 (Lemmon), C/2012 J1 (Catalina), C/2012 K1 (PANSTARRS), C/2012 S1 (ISON), C/2013 R1 (Lovejoy), C/2013 US10 (Catalina), C/2014 B1 (Schwartz), C/2014 E2 (Jacques), C/2014 Q2 (Lovejoy), C/2015 F4 (Jacques), C/2015 V2 (Johnson), C/2015 ER61 (PANSTARRS), C/2015 VL62 (Lemmon-Yeung-PANSTARRS), C/2016 A8 (LINEAR), and C/2017 O1 (ASASSN). The method consists in fitting the exponential decay function to the measured coma brightness in the aperture radius range from 0.5 to 2 pixels, and extrapolating this function to 0 pixels to obtain nuclear brightness. The R-band absolute nuclear magnitude RN(1, 1, 0), and the logarithm of the nucleus diameter DN expressed in kilometres, follow a linear dependence with the absolute total visual magnitude H. This dependence is of the form RN(1, 1, 0) = 12.5943 + 0.648H, and log DN[km] = 1.2415 − 0.13H. Comet 2P/Encke does not fit this dependence due to its high nuclear density of 800 kg m−3 (Sosa & Fernández 2009). The mean bulk density of the observed comets (except 2P/Encke) is 453 ± 29 kg m−3. The accuracy of the method in determining the brightness of comet nuclei at a level of 1σ is 8 per cent.

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