Oxygen Enrichment Membranes for Kuwait Power Plants: A Case Study.

Power plants are considered as the major source of carbon dioxide pollution in Kuwait. The gas is released from the combustion of fuel with air to convert water into steam. It has been proven that the use of enriched oxygen can reduce fuel consumption and minimize emissions. In this study, UniSim (Honeywell, Charlotte, NC, USA) was used to estimate the fuel savings and carbon dioxide emissions of the largest power plant in Kuwait (Alzour). Results showed that at 30 mol% oxygen, the fuel consumption was lowered by 8%, with a reduction in carbon dioxide emissions by 3524 tons per day. An economic analysis was performed on the use of a membrane unit to produce 30 mol% oxygen. At current market prices, the unit is not economical. However, the system can achieve a payback duration of 3 years if natural gas price increases to USD 6.74 or the compressor cost decreases to USD 52 per kW. Currently, the research and development sector is targeting a membrane fabrication cost of less than USD 10 per m2 to make the membrane process more attractive.

Optimization of Mordenite Membranes Using Sucrose Precursor for Pervaporation of Water-Ethanol Mixtures.

Post-treated mordenite membranes were prepared using sucrose (C12H22O11) as a carbon precursor to block any pinholes and defects in the zeolite layer. The pervaporation (PV) process was used to separate ethanol from the water. The effects of the sucrose concentration and the pyrolysis temperature (650-850 °C) were investigated, and the resulting high separation performance compared to those post/pre-treated membranes was reported in the literature. In this study, mordenite carbon membranes yielded a water/ethanol separation factor of 990.37 at a water flux of 9.10 g/m2h. The influence of the operating temperature on the performance of the membrane also was considered. It was concluded that the selective adsorption of water through zeolite pores was achieved. The entire preparation procedure was achieved using a rapid, low-cost preparation process.

A simulation study for the treatment of Kuwait sour gas by membranes.

Sour gas of the west fields of Kuwait is reported to have a concentration of 12 mol% carbon dioxide and 4 mol% hydrogen sulfide along with moistures. The gas is treated at the gathering center using amine and ethylene glycol units. However, the two processes are energy-intensive and work with solvents that necessitate proper disposal. On the other hand, polymeric membranes provide an energy-efficient solution for acid gas removal with gas dehydration in one step. A simulation study by UniSim was performed to determine if the cellulose acetate membranes are sufficient to treat 70,000 m3 h- 1 of gas by producing a stream that meets the pipeline requirements. Results show that the membranes met the standards but the hydrocarbons recovery was extremely low. It was concluded that the sour gas should contain no more than 3.5 mol% of carbon dioxide and 0.15 mol% hydrogen sulfide to attain a hydrocarbons recovery of 97%.

Minimizing Solvent Toxicity in Preparation of Polymeric Membranes for Gas Separation.

Toxic solvents such as dimethylformamide (DMF) are widely used for the preparation of polymeric membranes due to the strong dissolving power. Environmentally friendly solvents are available, but the developed membranes suffered from low performance due to the poor solubility of the polymer in the solvent. In this work, polyetherimide membranes were prepared using DMF with the addition of the biodegradable solvent γ-butyrolactone (GBL). Results show that mixing 75 wt % of DMF with 25 wt % GBL enhanced the membrane gas permeability toward hydrogen, methane, helium, carbon dioxide, and nitrogen. The overall permeability was increased by 9.6% compared to the permeability of the membrane made by 100 wt % DMF. Hydrogen-to-methane selectivity was also raised from 26.3 to 29.3.

Microscopy and Spectroscopy Techniques for Characterization of Polymeric Membranes.

Polymeric membrane is a proven technology for water purification and wastewater treatment. The membrane is also commercialized for gas separation, mainly for carbon dioxide removal and hydrogen recovery. Characterization techniques are excellent tools for exploring the membrane structure and the chemical properties. This information can be then optimized to improve the membrane for better performance. In this paper, characterization techniques for studying the physical structure such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) are discussed. Techniques for investigating the crystal structure such as X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS) are also considered. Other tools for determining the functional groups such Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and nuclear magnetic resonance (NMR) are reviewed. Methods for determining the elemental composition such as energy-dispersion X-ray spectroscopy (EDS), X-ray fluorescent (XRF), and X-ray photoelectron spectroscopy (XPS) are explored. The paper also gives general guidelines for sample preparation and data interpretation for each characterization technique.

The Implementation of a Carbon Precursor to Produce ZSM-5 Membranes for the Separation of Isomers in the Pervaporation System.

The separation of p-xylene from its bulkier m-xylene and o-xylene is of great importance in the petrochemical industry. This paper presents the experimental results of the separation of xylene isomers using a zeolite carbon composite membrane in a pervaporation system. The preparation method involves the use of an inexpensive carbon precursor, sucrose, to avoid the lengthy conventional preparation methods used in the literature (e.g., hydrothermal synthesis). The composite membranes that were prepared exhibited a separation performance with a p-xylene/o-xylene separation factor of 5.35 and permeability of 76 g/m2 h for 95% o-xylene at 25 °C. The preparation procedure was designed from an economical perspective to facilitate any possible future commercialization.

The use of a sucrose precursor to prepare a carbon membrane for the separation of hydrogen from methane.

In this study, we present the use of sucrose (C12H22O11), which exists in abundance in nature, to prepare a carbon membrane without any preceding treatments. The preparation procedure was conducted using a low pyrolysis temperature, i.e., in the range of 300-500 °C, followed by complete formation of the structure of the carbon membrane. The gas separation characteristics of the resulting membranes were assessed by evaluating both hydrogen and methane permeation. The highest selectivity obtained for H2/CH4 was 31.34 with H2 permeability of 459.24 GPU. The entire fabrication procedure was designed to be economical in order to facilitate any future commercialization.

Preparation of polyetherimide membrane from non-toxic solvents for the separation of hydrogen from methane.

Polymeric membranes are usually prepared from solvents like n-methylpyrrolidone (NMP) because of the strong dissolving power and high boiling point. Yet, the solvent is costly, toxic and has environmental issues. In this work, nontoxic solvents such as methyl L-lactate, ethyl lactate, propylene carbonate, tributyl o-acetylcitrate, tributyl citrate, triethyl phosphate, and γ-butyrolactone (GBL) were introduced during membrane preparation. It was found that all the solvents were unable to dissolve polyetherimide except GBL. The membranes made by GBL and NMP were evaluated for gas separation, and they have almost similar hydrogen-to-methane selectivity, but, hydrogen permeance was better in NMP membranes.