A.M. Shariff

Process simulation and optimal design of membrane separation system for CO2 capture from natural gas

Abstract Membrane process, a relatively new technology among other available techniques, can be used for the purpose of CO 2 capture from natural gas. Over the decades, membrane performance has been described by different mathematical models, but there is limited work done in the field of process simulation where membrane models can be incorporated with other unit operations using commercially available simulator. In this paper, a two dimensional cross flow mathematical model for membrane separation has been incorporated with Aspen HYSYS as a user defined unit operation in order to optimize and design the membrane system for CO 2 capture from natural gas. Parameter sensitivities, along with process economics, have been studied for different design configurations (including recycle streams and multiple stages). It has been observed that double stage with permeate recycle system gives the optimum design configuration due to minimum process gas cost involved with it.

Removal of high concentration CO2 from natural gas at elevated pressure via absorption process in packed column

Abstract Carbon dioxide (CO2) removal is an essential step in natural gas (NG) processing to provide high quality gas stream products and minimize operational difficulties. This preliminary study aims to investigate the removal of CO2 at high concentration level from the mixture of CO2-NG gas stream at elevated pressure via absorption process. This is to explore the possibility of exploring high CO2 content natural gas reserves by treatment at offshore platform. A mixed amine solvent, Stonvent-II, was used for the absorption of approximately 75 vol% CO2 in CO2-NG stream at a pressure of 10 barg. The initial solvent temperature was varied in order to study the impact of initial temperature on the absorption performance. Preliminary study at temperatures of 35°C and 45°C indicates that Stonvent-II was able to perform almost 100% removal of CO2 under both conditions. However, the CO2 absorption effect took place faster when the initial liquid temperature was lower. This is because when the initial liquid temperature is high, the temperature increase in the packing bed caused by the reaction heat is high which impacts the efficiency of absorption negatively.

Synthesis and Thermal Degradation Studies of Melamine Formaldehyde Resins

Melamine formaldehyde (MF) resins have been synthesized at different reaction temperature and pH values. Different molar ratios of melamine and formaldehyde were used to synthesize the corresponding resins. The prepared resin samples were characterized by using molecular weight determination viscometry and thermogravimetric analysis (TGA). The maximum percentage of solid content (69.7%) was obtained at pH 8.5 and 75°C temperature. The molecular weight of MF resin was increased with an increase of melamine monomer concentration. The highest residual weight 14.125 wt.% was obtained with sample 10.

Thermo Physical Analysis of 2-amino-2-methyl-1-propanol Solvent for Carbon Dioxide Removal

Removal of acid gases such as carbon dioxide (CO2) is normally carried out by aqueous solutions of alkanolamines. The traditional amines used for acid gas removal include; mono-ethanolamine (MEA), di-ethanolamine (DEA) and N-methyldiethanolamine (MDEA). There is a need to investigate new solvents to minimize the carbon emissions since the traditional amines have low CO2 loading capacity and require high energy for regeneration. Recently, a new class of amines, sterically hindered amines is identified as one of the potential solvent for acid gas removal due to their relatively higher CO2 absorption capacity, low heat of regeneration and higher values of rate constant. One of the identified solvent that has potential for commercialization is sterically hindered amine known as 2-amino-2-methyl-1-propoanol (AMP). The investigation of thermophysical properties of this solvent is essential in the design and optimization for smooth operation of acid gas removal process. The density, viscosity, surface tension and refractive index are the most important physical properties for this purpose which is presented in this paper. These properties of aqueous solutions of 2-amino-2-methyl-1propanol (AMP) are investigated over the industrially important temperature range of 298.15 K to 333.15 K. The thermal analysis of aqueous solutions was also carried out using TGA (Thermal gravity analyzer) with the heating rate of 10 °C·min under nitrogen (N2) environment in order to investigate the thermal stability of the solvent. All the investigated properties are correlated as a function of temperature for ease of usage in the design of acid gas removal system. The correlated and measured data are in good agreement.

Effect of Modified MIL-53 with Multi-Wall Carbon Nanotubes and Nanofibers on CO2 Adsorption

There is a growing need of counter assessing the increase of releases greenhouse gases such as carbon dioxide by researching an alternative technology that can help to reduce carbon dioxide content in atmosphere. This research work investigates the potential of MIL-53 as CO2 capture and storage candidate by conducting an experiment with different pressure between the synthesised and modified MIL-53. To investigate the effect of the Multi-wall carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) in MIL-53 towards CO2 adsorption performance. The synthesised samples were characterized by Fourier Transform Spectroscopy (FTIR) and Brunauer, Emmett and Teller (BET) techniques. A significant change is observed in the region of the aromatic deformation vibrations due to the different substitution patterns of the aromatic ring. BET surface area for MWCNT@MIL-53 is higher than CNF@MIL-53 and MIL-53. MWCNTs showed the adsorption of CO2 uptake is 0.3mmole-1/g at 100Kpa.

A Review on Robustness of Covalent Organic Polymers for CO2 Capture

The presence of carbon dioxide (CO2) in natural gas stream is a critical problem; besides causing corrosion it also reduces the energy contents and heating value of natural gas. Various separation techniques are available to separate CO2 from natural gas, such as metal organic framework (MOF), covalent organic framework (COF) and Covalent Organic Polymer (COP) adsorbents. The criteria of adsorbent selection that need to be fulfilled include high adsorption capacity, high selectivity of CO2 and hydrothermal stability at operating conditions. COPs are crystalline porous materials having high CO2 capacity and selectivity in the presence of water vapors. However, the research on COP material development is new and scarce information is available in literature. In this prospect, the paper highlights the different types of COPs, their basic constituents and the adsorption capacities.

Synthesis and CO2 adsorption study of modified MOF-5 with multi-wall carbon nanotubes and expandable graphite

MOF-5 was synthesized by solvothermal method and its reactivation under anhydrous conditions. This research is conducted to investigate the effect of MOF-5 and MOF-5 modified with multi-wall carbon nanotubes (MWCNTs) and expandable graphite (EG) on the performance of CO2 adsorption. The synthesized MOFs were characterized using Field emission scanning electron microscopy (FESEM) for surface morphology, Thermogravimetric analysis (TGA) for thermal stability, X-ray diffraction (XRD) for crystals plane, Brunauer-Emmet-Teller (BET) for surface area and CO2 adsorption. The result had showed that the modified MOF-5 enhanced the CO2 adsorption compared to the pure MOF-5. The increment in the CO2 uptake capacities of MOF materials was attributed to the decrease in the pore size and enhancement of micropore volume of MOF-5 by multi-walled carbon nanotube and EG incorporation. The BET surface area of the synthesized MOF-5@MWCNTs is more than MOF-5. The CO2 sorption capacities of MOF-5 and MOF-5@MWCNTs were observed...

Computational insights on the role of film thickness on the physical properties of ultrathin polysulfone membranes

Although it has been reported that physical properties of polymeric membranes inherit thickness dependent characteristics, typically when they are subjected to confinement at an ultrathin dimension (<1000 A), deviations from their bulk counterpart are still not completely understood. An empirical investigation of physical properties for an ultrathin membrane at laboratory scale is difficult, time consuming, and costly which is attributed to challenges to fabricate defect-free films with ultrathin thickness and that requires special instruments at critical conditions. In our current work, a Soft Confining Methodology for Ultrathin Films was conducted to simulate ultrathin polysulfone polymeric membranes of varying thicknesses, l, to resemble their actual size in the thickness dimension. Subsequently, physical properties of the constructed ultrathin films, e.g., density and glass transition temperature, have been elucidated from an atomistic insight. Quantitative empirical models have been proposed to capture thickness-dependent physical properties upon ultrathin confinement. In addition, free volume and cavity distribution was also quantified in order to elucidate the evolution in membrane morphology and to satisfy a previous research gap of deficiency in system dimension dependent cavity sizes. On the whole, it was found that a thinner structure exhibits higher structural density and lower glass transition temperature, as well as lower free volume and cavity sizes. The findings from the present work are anticipated to propose an alternative from a molecular simulation aspect to circumvent complexities associated with experimental preparation and testing of ultrathin polymeric membranes, while providing direct elucidation and quantification of thickness-dependent physical properties in order to enhance understanding at a molecular perspective.

Solubility of CO2 in Piperazine (PZ) Activated Aqueous Solutions of 2-Amino-2-methyl-1-propanol (AMP) at Elevated Pressures

The solubility of carbon dioxide (CO2) was measured in aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) and Piperazine (PZ) activated aqueous solutions of (AMP) at two different temperatures (303.15 and 333.15)K and at various concentrations of studied solvents. The measurements were made over the pressure range of 5 to 60 bar. The results are presented as a function of pressure. It has been found that the addition of PZ to the aqueous solutions gives significantly higher CO2 loadings at higher pressures. The influence of pressure on solubility is found to be positive. However, solubility decreases with the increase of temperature.

Mathematical modelling of thickness and temperature dependent physical aging to O2/N2 gas separation in polymeric membranes

Polymeric membranes are glassy materials at non-equilibrium state and inherently undergo a spontaneous evolution towards equilibrium known as physical aging. Volume relaxation characteristic during the course of aging is governed by the surrounding temperature in which the polymeric material is aged. Although there are studies to understand how polymeric materials evolve over time towards equilibrium at different operating temperatures, the theories have been developed merely in response to experimental observations and phenomenological theory at bulk glassy state without the implementation of sample size effects. Limited work has been done to characterize the physical aging process to thin polymeric films using reasonable physical parameters and mathematical models with incorporation of thermodynamics and film thickness consideration. The current work applies the Tait equation of states and thickness dependent glass transition temperature, integrated within a simple linear correlation, to model the temperature and thickness dependent physical aging. The mathematical model has been validated with experimental aging data, whereby a small deviation is observed that has been explained by intuitive reasoning pertaining to the thermodynamic parameters. The mathematical model has been further employed to study the gas transport properties of O2 and N2, which is anticipated to be applied in oxygen enriched combustion for generation of cleaner and higher efficiency fuel in future work.