Use of nanoporous ceramic membranes for carbon dioxide separation

Natural gas processes accounts for about 5.3 billion tonnes per year of carbon dioxide (CO2) emission to the atmosphere. At this rate of emission, the expectation will drastically rise if not curtailed. In order to achieve this, a cost-effective and environmental friendly technology is required. In recent times, membrane technology has been widely applied for CO2 removal from raw natural gas components. This article examines CO2 separation from natural gas, mainly methane (CH4), through a mesoporous composite membrane. A laboratory scale tubular silica membrane with a permeable length of 348 mm, I.D and O.D of 7 and 10 mm, respectively, was used in this experiment. Scanning electron microscopy (SEM) was used to analyze the morphology of the membrane. Single gas permeation of helium (He), CH4, nitrogen (N2), argon (Ar) and CO2 were determined at permeation temperature range between 25 and 100°C and feed gauge pressure of 0.05 to 5.0 barg. Before silica modification, He recorded the highest flow rate (0.3745 l/min) while CO2 recorded the least flow rate (0.1351 l/min) at 0.4 barg and 25°C. After silica modification, CO2 flow enhances significantly (3.1180 l/min at 1.0 barg) compared to CH4 (2.1200 l/min at the same gauge pressure) due to the influence of surface flow mechanism. Temperature variation described the applicability of Knudsen diffusion for He. A combination of viscous, surface and Knudsen diffusion transport mechanisms were obtained throughout the experiment. Membrane thickness was also calculated to be 2.5 × 10−4 m

Purification of gases using nanoporous inorganic membranes.

The application of membranes has gained acceptance in the chemical and process industries for separation and purification for over three decades and is currently being practiced for natural gas processing, waste water treatment among others. A crack-free composite membrane was employed in this paper. Scanning electron microscopy (SEM) observation was carried out to characterize the membrane. The operational parameters such as feed flow rate, permeation pressure, permeation temperature, kinetic diameter and gas molecular characteristics are examined at 25C to 450C and 0.05 to 1.0 barg feed pressure. The performance of gas selectivity is also provided. Separation factor of 2.554 was obtained for H2/CO2 at 450C and 0.8 barg. Activation energies of 1.0 and 0.42 kJ/mol were also obtained for H2 and CO2/CO/H2 gas mixtures at 1.0 barg

Development and characterization of a catalytic membrane for volatile organic compound combustion

Platinum-alumina (Pt/γ-Al2O3) catalytic membranes were obtained using the reservoir technique for the combustion of volatile organic compounds (VOCs). The membranes were characterized by scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDXA) observation, Brunauer-Emmett-Teller (BET) measurement and gas permeation. Propane (C3H8) and n-butane (C4H10) combustion was obtained. Maximum VOC conversion for propane and n-butane of 93 and 48 (%) was achieved on 3.52wt% Pt catalyst at a temperature of 427 and 259 (0C) and flow rates of between 185-222 and 295-379 (ml/min) without any changes in conversion. The combustion results of C3H8 and C4H10 corroborate with literature on Pt/γ-Al2O3 catalysts. The conversion was achieved using flow-through catalytic membrane reactor operating in the Knudsen flow regime

The use of NF and RO membrane system for reclamation and recycling of wastewaters generated from a hard coal mining

In this study, the possibility of treatment of wastewater generated from underground hard coal mining excavation was experimentally investigated using Nano filtration (NF) and Reverse Osmosis (RO) membrane systems. Two-stage sequential treatment method was applied to perform the study. In the first stage, the raw wastewater was treated using NF membrane filtration system without any pre-processes. In the second stage, the effluents of NF membrane system were fed into RO membrane system for the treatment. To determine the treatment performance of the NF and RO membrane system, the operating pressures were fixed at 10, 20 and 30 bar (KN/m2) for both systems during the experimental study. Turbidity, sodium, calcium, magnesium, manganese, iron, copper, aluminium, ammonium, sulphate and electrical conductivity were analysed in raw wastewater and permeate flow of NF and RO membrane systems to determine the treatment performances. Treatment performance of RO membrane system was observed to have highest yield of80% for all parameters examined at 20 bar operating pressure.Keywords: Polymeric membrane, wastewater treatment, coal excavation, water recycle and reus

A study of gas diffusion characteristics on a micro porous composite silica ceramic membrane.

The purpose of this study is to investigate gas permeation behaviour of five gases (CO2, He, H2, N2 and Ar) across two silica modified ceramic membranes, Membrane Y and Membrane Z. An examination of the variations in their layer thickness and flow rate was determined. Solution-dip coating process was used for the modification process specifically for pore size reduction. This resulted in some level of modifications in the layer thickness after a successive dipping time as well as flow rate in relation to pressure drop. The effect of number of dips generally influenced the layer thickness of both membranes. Membrane Y layer thickness through five successive dipping was in the range of 89.2-36μm while Membrane Z ranges between 150.72 and 43.69μm. Gas permeability as a function of mean pressure for Membrane Z was calculated using data obtained experimentally. The permeation tests confirmed the contribution of both Knudsen and viscous flow mechanism with an estimation and prediction of the membrane pore radius

Latent relationships between Markov processes, semigroups and partial differential equations

This research investigates existing relationships between the three apparently unrelated subjects: Markov process, Semigroups and Partial difierential equations. Markov processes define semigroups through their transition functions. Conversely particular semigroups determine transition functions and can be regarded as Markov processes. We have exploited these relationships to study some Markov chains. The infnitesimal generator of a Feller semigroup on the closure of a bounded domain of Rn; (n ^ 2), is an integro-diferential operator in the interior of the domain and verifes a boundary condition. The existence of a Feller semigroup defined by a diferential operator and a boundary condition is due to the existence of solution of a bounded value problem. From this result other existence suficient conditions on the existence of Feller semigroups have been obtained and we have applied some of them to construct Feller semigroups on the unity disk of R2.Decision SciencesM. Sc. (Operations Research

Experimental study of gas flux characteristics in a CO2 selective silica based modified membrane.

The purpose of membrane gas separation for CO2 capture from flue gas process is to reduce greenhouse emissions as well as associated environmental challenges globally. This study looks at gas separation in a single gas permeation experiment using CO2, O2, CH4 and N2 gases by means of a highly selective and permeable inorganic ceramic membrane. A fresh ceramic membrane has been prepared by dip-coating technique through immersion in a silica-based precursor solution for pore size modification and used for gas purification purposes. Results obtained show excellent performance of the silica based membrane for CO2 recovery applications through adsorptive transport mechanism. Effect of pressure drop on gas flux showed a linear proportionality. The gas flux has high CO2 flux of 1.71mols-1m-2 at room temperature in comparison to that of other gases. Further results show that CO2 permselectivity to that of N2 supported the theoretical Knudsen with a high selectivity factor of 3.83 confirming a reasonable capture of CO2 to that of N2 as a major component of a flue gas stream.;\\$aCarbon capture; Composite membrane; Gas permeation; Gas flux; Perm selectivit

Catalytic membrane reactor-separator for environmental applications.

Flow-through catalytic membrane reactors offer the potential for improved conversions at reduced operating temperature due to product separation and catalyst activity. An experimental work dealing with a forced flow-through membrane reactor is the subject of this thesis. The focus is on the performance and transport characteristics of selective thin-supported silica membranes and flow-through catalytic membrane systems. The improvement of VOC-selective, H2-selective and CO2-selective membrane properties by the use of systematic dip-coating techniques and the application of the technique in a bi-layer membrane repair concept for gas separation membranes has been studied. In addition, several methods were used to characterize the membranes, including scanning electron microscopy, energy diffraction X-ray, nitrogen adsorption and gas permeation. In the first part of this work, CO2 permeance (3.39 x 10-8 mol m-2 s-1 Pa-1 at 25 0C for γ-Al2O3 membrane after exposing boehmite to the support) was mainly attributed to the Knudsen diffusion mechanism. CO2/CH4 selectivity of 24.07 was obtained from the silica membrane at 25 0C and 0.7 bar. Such a selectivity value could be useful in small-scale carbon dioxide removal units for natural gas treatment processes. In addition, H2/N2 selectivity of 1.36 and 2.72 at 1 bar were obtained from macro and meso porous membranes at 25 0C. The selectivity of propylene (C3H6) over N2 was also obtained. Higher selectivity of 1.79 at 0.05 bar was obtained. This selectivity increased by a factor of 2 compared to the ideal Knudsen selectivity (0.82). Remarkable propane conversion of 95.47% was achieved at a temperature of 378 0C on a 3.52 wt% platinum (Pt) catalyst at different total flow rates, ranging from 166 to 270ml/min. The temperature at which the catalytic combustion takes place for the VOC corroborates with (or is lower than) the one obtained from the literature for the same VOC on 5 wt% Pt/γ-Al2O3 catalysts

Validation of a novel approach for CO2/N2 gas separations by means of a hybrid ceramic membrane.

Global warming has been documented as one of the world's foremost ecological concerns. Although it is difficult to totally end human related global warming, there is a possibility to alleviate these effects through a wide spectrum of options. One such possibility is the reduction of atmospheric carbon dioxide emissions, a major greenhouse gas widely thought to be responsible for global warming. This paper therefore looks at an experimental validation of gas separation by means of a high selective membrane for CO2 recovery applications. Analysis of the results obtained is in good agreement with literature experimental data. Additional results show that CO2 selectivity factor is reasonable for capture of CO2 from N2 as a key constituent in a flue gas stream

Performance evaluation of an inventive CO2 gas separation inorganic ceramic membrane.

Atmospheric carbon dioxide emissions are considered as the greatest environmental challenge the world is facing today. The tasks to control the emissions include the recovery of CO2 from flue gas. This concern has been improved due to recent advances in materials process engineering resulting in the development of inorganic gas separation membranes with excellent thermal and mechanical stability required for most gas separations. This paper, therefore, evaluates the performance of a highly selective inorganic membrane for CO2 recovery applications. Analysis of results obtained is in agreement with experimental literature data. Further results show the prediction performance of the membranes for gas separation and the future direction of research. The materials selection and the membrane preparation techniques are discussed. Method of improving the interface defects in the membrane and its effect on the separation performance has also been reviewed and in addition advances to totally exploit the potential usage of this innovative membrane