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ABSTRACT
Cyclic adsorption processes of PSA, VSA, and TSA were modeled and numerically simulated using SAPO-34 core-shell adsorbent. The results were compared with ordinary SAPO-34 to achieve a more efficient process for CO2–CH4 separation. OCM coupled with method of lines was used for numerical solution of the mechanistic model. The simulation results revealed higher efficiency of core-shell adsorbent with less usage of SAPO rather than the ordinary adsorbent to achieve the same degree of purification and recovery. VSA and TSA processes against PSA resulted in CH4 purification capability more than 99% with more than 73% recovery. However, VSA process has revealed higher productivity rather than TSA.
Nomenclature
| C | = | gas phase molar concentration (mol/m3) |
| = | gas phase molar specific heat at constant pressure (J/mol K) | |
| D | = | bed diameter (m) |
| = | axial mass transfer coefficient (m2/s) | |
| = | crystal (micro-pore) mass transfer coefficient (m2/s) | |
| = | heat of adsorption (J/mol) | |
| = | equilibrium constant in the multi-site Langmuir isotherm (1/Pa) | |
| = | LDF rate constant (1/s) | |
| L | = | bed length (m) |
| = | molecular weight (kg/mol) | |
| P | = | bed pressure (Pa) |
| = | volume averaged loading in adsorbed phase (mol/kg) | |
| = | loading in equilibrium with bulk gas (mol/kg) | |
| = | maximum saturation loading (mol/kg) | |
| R | = | ideal gas constant (J/mol K) |
| t | = | time (s) |
| T | = | gas or solid phase temperature (K) |
| u | = | superficial velocity (m/s) |
| U | = | overall heat transfer coefficient (W/m2 K) |
| z | = | axial position (m) |
| = | transformed axial position (-) | |
| A | = | first-order collocation matrix (-) |
| B | = | second-order collocation matrix (-) |
Greek letters
| = | porosity | |
| = | axial heat transfer coefficient (W/m K) | |
| = | gas phase viscosity (kg/m s) | |
| = | density (kg/m3) |
Subscripts
| b | = | bulk phase |
| c | = | particle core |
| i | = | gaseous species |
| T | = | total gas phase |
| J | = | jacket |
| p | = | particle phase |
| s | = | solid phase |
| sh | = | shell |
| ads | = | adsorption step |
| dpe | = | depressurize–equalization step |
| bdn | = | blowdown step |
| prg | = | purge step |
| peq | = | pressurize-equalization step |
| peqc | = | pressurize-equalization with cooling step |
| rep | = | re-pressurization step |
Supplemental Material
Supplemental data for this article can be accessed on the publisher’s website.