Abstract
Over the past decade, membrane contactors (MBC) for CO2 absorption have been widely recognized for their large intensification potential compared to conventional absorption towers. MBC technology uses microporous hollow-fiber membranes to enable effective gas and liquid mass transfer, without the two phases dispersing into each other. The main contribution of this paper is the development and verification of a predictive mathematical model of high-pressure MBC for natural gas sweetening applications, based on which model-based parametric analysis and optimization can be conducted. The model builds upon insight from previous modeling studies by combining 1-d and 2-d mass-balance equations to predict the CO2 absorption flux, whereby the degree of membrane wetting itself is calculated from the knowledge of the membrane pore-size distribution. The predictive capability of the model is tested for both lab-scale and pilot-scale MBC modules, showing a close agreement of the predictions with measured CO2 absorption fluxes at various gas and liquid flowrates, subject to a temperature correction to account for the heat of reaction in the liquid phase. The results of a model-based analysis confirm the advantages of pressurized MBC operation in terms of CO2 removal efficiency. Finally, a comparison between vertical and horizontal modes of operation shows that the CO2 removal efficiency in the latter can be vastly superior as it is not subject to the liquid static head and remediation strategies are discussed.
Highlights
The lab-scale module experiments were conducted with the binary feed gas mixtures of CH4/CO2 and N2/CO2 at 11 bar, while the pilot module was up-scaled by a factor of about 800 to be operated under industrially relevant operating conditions at 54 bar in a natural gas processing plant in Malaysia
Pilot-scale membrane contactors (MBC) module The CO2-rich natural gas was fed to the tube side of the MBC, while the lean amine was pressurized to ca. 54 bar and fed to the shell side, in a counter-current and vertical configuration
This paper has developed a mathematical model of highpressure MBC using chemical solvents, which describes the effect of membrane pore-size distribution and operating conditions on membrane wetting and CO2 absorption
Summary
The sales gas specification for NG typically imposes a CO2 content lower than 2–3%. Natural gas (NG) is presently the third most-utilized form [TransCanada, 2016]. In liquefied natural gas (LNG) plants, of fossil fuel energy and is widely used for both electricity CO2 should be removed further to meet the tight specificaproduction and transportation. Surpassing coal as the second most utilized fuel by pipeline transport is concerned, CO2 removal avoids pump-. NG consists of a mixture of combustible hydrocarbon ing any extra volume of gas and reduces the risk of corrosion gases typically from methane (CH4) to pentane (C5H12), with impurities such as carbon dioxide (CO2). Removal of CO2 from when moisture is present in process equipment and pipeline. Regarding NG utilization lastly, the presence of CO2 reduces the heating value of NG
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