Methane, equilibrium sorption

Equilibrium Sorption Studios of Methane on Pittsburgh Seam and Pocahontas No. 3 Seam Coal... 

Logarithmic plots of the Freundlich equation, Q = kpn, where Q is the amount of methane adsorbed at a pressure p, and k and n are constants, for methane adsorption at 0°, 30° and 50°C. in Figures 6 and 7 indicate that the equation is valid up to at least 1000 torr. Equilibrium sorption points obtained on different samples in a manostatic adsorption apparatus are shown as solid points in Figures 6 and 7. The exponent n varied from 0.72 at 0° to 0.87 at 50°C. for the Pocahontas coal and from 0.78 at 0° to 0.94 at 50°C. for Pittsburgh coal (Table III). 

Loughiin, K. F Hassan, M. M. Fatehi, A. 1. Zahur, M. Rate and equilibrium sorption parameters for nitrogen and methane on carbon molecular scieve. Gas Sep. Purif. 1993,... 

The maximum equilibrium pressures applied in laboratories in measuring the methane/coal sorption isotherm were about 6-10 MPa, however, the geostatic pressure, during and after the coalification process, may be much greater. This case especially may occur when the coal seam is a sunken lock and the methane was still present in the coal at the time of the tectonic movement. Therefore, it is... 

In recent years, new concepts to produce hydrogen by methane SR have been proposed to improve the performance in terms of capital costs reducing with respect to the conventional process. In particular, different forms of in situ hydrogen separation, coupled to reaction system, have been studied to improve reactant conversion and/or product selectivity by shifting of thermodynamic positions of reversible reactions towards a more favourable equilibrium of the overall reaction under conventional conditions, even at lower temperatures. Several membrane reactors have been investigated for methane SR in particular based on thin palladium membranes [14]. More recently, the sorption-enhanced steam methane reforming (Se-SMR) has been proposed as innovative method able to separate CO2 in situ by addition of selective sorbents and simultaneously enhance the reforming reaction [15]. 

ABSTRACT. An isosteric sorption system has been used to study the sorption of methane, ethane, ethene, propane, N2 and CO2 and some of their binary mixtures in silicalite-1. Isotherms of some of these sorbates have been determined at equilibrium pressures up to 20 atmospheres. Isosteric heats of sorption have been obtained from the slopes of the isosteres. Separation factors calculated from the Henry s Law constants determined from the initial slopes of the single conq>onent isotherms are found to be in good agreement with experim tal separation factors. The Langmuir-Freundlich equation has be used to lit the single component data and the Ideal Adsorbed Solution theory has be used to predict a binary sorption isotherm from the respective single component data. Comparison of the sorption behaviour of the hydrocarbons in silicalite-1 and NaY zeolites has been made. 

At 5°C, no hydrogen could be detected in the slurry and the heat of sorption was negligible. We wish to separate a gas feed at 5°C that contains 100 Ib/h of hydrogen and 30 Ib/h of methane. An oudet gas concentration of 0.05 wt frac methane is desired. The entering slurry will contain no methane and flows at a rate of 120 Ib/h. Find the number of equilibrium stages required for this separation and the mass fraction methane leaving with the slurry. 

Zhou, L., Liu, X., Li, J., Sun, Y, and Zhou, Y. 2006. Sorption/desorption equilibrium of methane in silica gel with pre-adsorption of water. Colloids Surf. A Physicochem. Eng. Aspects 273 117-120. 

In sorption-enhanced reforming (SER) reactors, one of the products is extracted from the reaction zone, thus shifting the reaction equilibrium to the product side. In SER, the methane steam-reforming catalyst is mixed with a CO2 sorbent ( acceptor ). The CO2 produced during the reaction is adsorbed and the reverse... 

In Figure 5 is represented the normal sorption hysteresis of the hazardous coal sample. It is an open hysteresis function measured by Sartorius 4112 Type micro balance applicable to 12 MPa pressure fl.3]. The open hysteresis indicates that at very low equilibrium pressure range a great amount of methane remains in the inside structure of coal. This phenomenon cannot only be explained by very slow kinetic process of desorption because the remained amount of methane is independent of time required to formation of desorption equilibrium pressure. The remained amount of methane can better be emphasized by data shown in Figure 6. 

The empty circles indicate the normal sorption data, however, the full symbols represent non-equilibrum data measured by the following way [13], After every sorption processes the methane was expanded to pressure 1 bar and was measured the desorbed amount of gas. It means, that the full circles in Figure 6 relate to the remained sorbed amount of methane when every current equilibrium pressure is reduced to 1 bar. It is very interesting that there are coals with the same age (Jurassic) which can absorb more methane (see Figure 7) than coals shown in Figures 5 and 6, however, these coals in Figure 7 have only smaller open hysteresis than that of the hazardous coals and in these coal entries never were observed any proneness to outburst. 

Finally, K is also a constant (it depends on the temperature only) and it is expressed in (MPa ). K is in direct connection with the adsorptive potentials of the heterogeneous surface [18]. The parameters of Eq. (1) applied to sorption isotherm shown in Figures 6 and 7 are tabulated in Table 2. From the extrapolated data of Eq. (1) to the estimated or sometimes measured geostatic equilibrium pressures can be calculated that coal seams beeing in a depth of 700-1000 m and having a mass about 40 million metric tons may contains 50-60 thousand million cubic meters methane wich is comparable with a good sandstone reservoir. 

The velocity profiles and the axial distribution of volume fraction of solid particles are shown in Fig 4.12. The solid velocity pattern did show a non-axial symmetric behavior. The axial distribution of the solid phase was close to uniform. Figure 4.13 displays the outlet fractions of hydrogen, methane, and CO2 in the gas phase as achieved for the SMR and SE-SMR processes operated in a BFB reactor. In the SMR results, the outlet molar fraction of H2 is only 75 %, thus a considerable amount of CO2 and CH4 are emitted out of the reactor. In the SE-SMR process results, both the conversion of methane and the adsorption of CO2 are larger than 99 %. The simulation results show that the integration of CO2 sorption in the SMR process can enhance the methane conversion to hydrogen to near the equilibrium composition in the BFB reactor. 

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