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Abstract  Gases like CO2 and CH4 are able to adsorb on the coal surface, but also to dissolve into its structure causing the coal to swell. In this work, the binary adsorption of CO2 and CH4 on a dry coal (Sulcis Coal Province, Italy) and its swelling behavior are investigated. The competitive adsorption measurements are performed at 45 °C and up to 190 bar for pure CO2, CH4 and four mixtures of molar feed compositions of 20.0, 40.0, 60.0 and 80.0% CO2 using a gravimetric-chromatographic technique. The results show that carbon dioxide adsorbs more favorably than methane leading to an enrichment of the fluid phase in CH4. Coal swelling is determined using a high-pressure view cell, by exposing a coal disc to CO2, CH4 and He at 45 and 60 °C and up to 140 bar. For CO2 and CH4 a maximum swelling of about 4 and 2% is found, whereas He shows negligible swelling. The presented adsorption and swelling data are then discussed in terms of fundamental, thermodynamic aspects of adsorption and properties which are crucial for an ECBM operation, i.e. the CO2 storage capacity and the dynamics of the replacement of CH4 by CO2. [ABSTRACT FROM AUTHOR]

Abstract   Simulated moving bed (SMB) is a cost-efficient separation technique that offers high productivity and low solvent consumption. SMB has gained importance in the pharmaceutical and fine chemical industry to perform complex separation tasks. However, an open and challenging problem is the optimal, robust operation of the SMB process. We have developed a control scheme that integrates the optimization and control of the SMB unit. A significant feature of the controller is that only minimal information of the system has to be provided, i.e. the linear adsorption behavior of the mixture to be separated and the average void fraction of the columns. Therefore, a full characterization of the adsorption behavior of the mixture and the columns is no longer required. In this ‘cycle to cycle’ control scheme, the measurements, optimization and control actions are performed once in every cycle. This paper presents simulation results of the control scheme applied to the separation of binary mixtures characterized by generalized Langmuir isotherms. The results are presented and analyzed in the frame of the triangle theory that has been recently extended to encompass these types of isotherms. Besides, online optimum performance of the SMB unit is compared with off-line optimization carried out using genetic algorithm. The results show that the controller fulfills the product and process specifications while operating the SMB unit optimally, regardless of the different types of Langmuir isotherms that the systems exhibit. [ABSTRACT FROM AUTHOR]

Abstract   The excess adsorption of CO2 on 13X zeolite and of N2O on silica gel has been studied at high pressure using a magnetic suspension balance, i.e. a gravimetric method. Recently, a detailed study on the density distribution in the measuring cell of the magnetic suspension balance showed that a proper approach to thermostatting the unit should be used in order to obtain reliable and accurate excess adsorption measurements. This is particularly important in the vicinity of the critical point of the fluid, where the density is strongly dependent on pressure and temperature. In the past, several effects were observed in our laboratory when measuring near-critical adsorption on 13X zeolite and on silica gel, namely critical adsorption and critical depletion. In the present study, these effects have been checked using the balance in the new thermostatting configuration, and the conclusion can be drawn that the accuracy of the measurement is not sufficient to prove that they indeed occur. More accurate adsorption data for the two systems have been measured and reported. [ABSTRACT FROM AUTHOR]