CO2 Feed Concentration Research Articles

Energy and cost estimates for capturing CO2 from a dry flue gas using pressure/vacuum swing adsorption

Few energy/cost estimates exist in the literature for adsorption-based CO2 capture. We study a pressure/vacuum swing adsorption (PVSA) process using zeolite 13X for post-combustion capture of CO2 from dry flue gas, and report useful insights into the effects of column dimensions and feed CO2 concentration. We propose a configuration for a full-scale CO2 capture and concentration plant for a 500MW power plant, and then develop a mathematical programming formulation to minimize its total annualized cost (TAC). Our estimated TAC for capture from a 500MW power plant flue gas with 15% CO2 is US$33.4–40.3 per tonne of CO2 avoided (US$30.4–36.7 per tonne of CO2 captured). The key result is that the energy penalty for CO2 capture amounts to less than 25% of TAC. Thus, using TAC as the design objective for a capture facility may be more appropriate than the popular choice of energy.

CO2-selective membranes for hydrogen production and CO2 capture – Part II: Techno-economic analysis

Syngas processing often requires separation of CO2 and hydrogen for hydrogen production, and the resulting CO2-enriched stream presents an opportunity for simultaneous CO2 capture. For example, syngas-based integrated gasification combined cycle (IGCC) power plants are envisioned as an efficient means of producing power from coal where CO2 capture technologies can be applied relatively easily. Membrane technology is an attractive approach for CO2 capture because of inherent process advantages such as simplicity, reliability, compactness and modularity. This paper (Part II of a two-part study) performs techno-economic analysis for CO2-selective membranes in three hydrogen production or utilization applications: methane reformer/pressure swing adsorption processes, oxygen-blown coal-fired IGCC power plants using GE gasification technology, and air-blown coal-fired IGCC power plants using Transport Integrated Gasification (TRIG) technology. These processes require membranes with CO2/H2 selectivities of 10–20, which can be provided using PolarisTM membranes. Hybrid approaches using a combination of membrane and cryogenic processes are evaluated for the production of high-pressure liquid CO2 ready for utilization or sequestration. The optimal membrane CO2/H2 selectivity and influence of CO2 capture rate on the cost of CO2 capture are determined, providing general guidelines for future membrane development. The cost of CO2 capture with these membrane processes depends not only on the feed CO2 partial pressure, but on the feed CO2 concentration as well.

Hybrid fixed-site-carrier membranes for CO2 removal from high pressure natural gas: Membrane optimization and process condition investigation

The hybrid fixed-site-carrier (FSC) membranes were prepared by coating the carbon nanotubes (CNTs) reinforced polyvinylamine (PVAm)/polyvinylalcohol (PVA) blend selective layer on the top of the polysulfone (PSf) ultrafiltration membranes. The influences of membrane preparation parameters of support, heat treatment condition and pH value of casting solution on the membrane separation performance were systematically investigated. The hybrid FSC membranes prepared under the optimal condition (PSf 20K − 95°C − 0.75h – pH 10) showed high CO2 permeance and relatively good CO2/CH4 selectivity based on high pressure gas permeation testing. Moreover, process operating parameters such as feed pressure, temperature, feed CO2 concentration, and feed flow rate as well as water vapor content were found to significantly affect the membrane performance, which need to be optimized in the real application. Small pilot-scale modules with relatively large membrane areas (110–330cm2) were additionally tested. The results could be used to guide process simulation and economic feasibility analysis of CO2 removal from high pressure natural gas process with the developed FSC membranes in the future work.

Effect of recycle ratio on the cost of natural gas processing in countercurrent hollow fiber membrane system

The separation of the countercurrent hollow fiber membrane module has been characterized adapting a “Multi-component Progressive Cell Balance” approach and incorporated within the Aspen HYSYS process simulator. The simulated data is found to exhibit good accordance with published experimental result. The study of the double staged membrane module with permeate recycle system, which was proposed to be the optimum configuration in previous works, has been extended by altering the recycle ratio of the permeate stream to study the process economics. Parameter sensitivities of typical membrane selectivity and CO2 feed concentration adapted in industrial application have been conducted. The study of high CO2 content is highlighted since it represents the future expansion of natural gas extraction considering that most of the remaining fields contain high concentration. It is observed that the recycle ratio is an important parameter to be considered in the industrial design process since it affects the gas processing cost significantly. Increasing the recycle ratio is proposed to increase the membrane area and compressor power while improving the hydrocarbon recovery, with substantial impact observed at low selectivity membrane and high CO2 feed concentration. A tradeoff must be determined among these parameters for determination of the optimal recycle ratio configuration.

Mixed matrix membranes comprising of Matrimid and –SO3H functionalized mesoporous MCM-41 for gas separation

Ordered mesoporous silica spheres (MCM-41) were used as fillers in polyimide (Matrimid) based mixed-matrix membranes (MMMs). The filler particles were functionalized with sulfonic acid (–SO3H) groups to increase the separation performance of the membranes by increasing the CO2 solubility. The fast diffusion of gases through the mesoporous materials, accompanied by this increased interaction with CO2, resulted in the simultaneous increase of gas permeability and selectivity. The functionalized membranes showed up to 31% increase in CO2 permeability and 14% increase in CO2/CH4 selectivity. In order to study the stability of these newly developed MMMs, they were tested at different operating conditions (temperatures, mixed-gas feeds and CO2 feed concentration).

Dynamic Adsorption of CO2 from Methane: Studies on Mass and Heat Transfer

AbstractThree‐dimensional computational fluid dynamics studies related to dynamics adsorption of CO2 from natural gas is found to be limited. 3D analyses for dynamics adsorption are substantially crucial to give a better prediction on the adsorption process by considering the actual fluid flow behavior within the packed‐bed porous media. A kinetic adsorption model has been integrated in a commercial fluid dynamics simulator to simulate the 3D hydrodynamics and adsorption phenomenon in a zeolite‐filled packed column for a CO2‐methane separation system. The effects of various parameters such as Reynolds number, CO2 feed concentration, feed temperature, and column dimension on CO2 adsorption efficiency have been investigated. A correlation for adsorption efficiency based on the CO2 concentration profiles has been developed and validated.

Nanocomposite MFI-Alumina Hollow Fiber Membranes: Influence of NOx and Propane on CO2/N2 Separation Properties

This study provides a detailed survey of the effect of moisture, NOx and light hydrocarbons (i.e., propane) on the CO2/N2 permeation and separation properties of MFI-type hollow-fiber membranes in view of on board CO2 capture applications in Diesel vehicles. Five different MFI-alumina samples have been prepared including different degrees of isomorphous boron and germanium substitution, as well as ex framework proton exchange by copper. The quality of the synthesized hollow fibers has been primarily assessed by pure N2 permeation and n-butane/H2 and SF6/N2 separation at room temperature. The different materials show preferential CO2/N2 and CO2/NO selectivity at low CO2 feed concentrations (∼10%) in the temperature range 298–373 K, which can be appreciably promoted under the presence of propane (1 v/v %). The materials show stable and high CO2 permeances even in the presence of large amounts of water in the feed stream. On the basis of the permeation and separation data measured in this study, we present a refined simulation study of a membrane cascade system constituted of two hollow-fiber membrane modules coupled to a DeNox unit for on board CO2 capture and liquefaction/supercritical storage in heavy vehicles (>40 tn).

High temperature H2/CO2 separation using cobalt oxide silica membranes

In this work high quality cobalt oxide silica membranes were synthesized on alumina supports using a sol–gel, dip coating method. The membranes were subsequently connected into a steel module using a graphite based proprietary sealing method. The sealed membranes were tested for single gas permeance of He, H2, N2 and CO2 at temperatures up to 600 °C and feed pressures up to 600 kPa. Pressure tests confirmed that the sealing system was effective as no gas leaks were observed during testing. A H2 permeance of 1.9 × 10−7 mol m−2 s−1 Pa−1 was measured in conjunction with a H2/CO2 permselectivity of more than 1500, suggesting that the membranes had a very narrow pore size distribution and an average pore diameter of approximately 3 Å. The high temperature testing demonstrated that the incorporation of cobalt oxide into the silica matrix produced a structure with a higher thermal stability, able to resist thermally induced densification up to at least 600 °C. Furthermore, the membranes were tested for H2/CO2 binary feed mixtures between 400 and 600 °C. At these conditions, the reverse of the water gas shift reaction occurred, inadvertently generating CO and water which increased as a function of CO2 feed concentration. The purity of H2 in the permeate stream significantly decreased for CO2 feed concentrations in excess of 50 vol%. However, the gas mixtures (H2, CO2, CO and water) had a more profound effect on the H2 permeate flow rates which significantly decreased, almost exponentially as the CO2 feed concentration increased.

Hybrid membrane cryogenic process for post-combustion CO2 capture

Reducing the energy requirement for the capture step is a major challenge in Carbon Capture and Storage (CCS) technology. Different capture processes have been investigated in the literature, such as absorption, adsorption, chemical looping and membrane separation. In this paper, the potential for a hybrid process combining membrane and cryogenic separation to achieve efficient post-combustion carbon capture has been investigated through a simulation study. The hybrid process combines a first step CO2 pre-concentration with a membrane unit and a second step CO2 cryogenic condensation. The influence of three CO2 feed contents (5, 15 and 30%), 3 different compression strategies and two membrane selectivities (a CO2/N2¼ 50 and 100) on the separation performances have been investigated for a required CO2 purity of 0.9 and a capture ratio larger than 85%. It is shown that the use the use of feed compression with Energy Recovery System (ERS) membrane module offers the best performances when energy requirement and membrane surface area taken into account. More specifically for a CO2 feed concentration ranging between 15 and 30%, the hybrid process shows a reduced energy requirement compared to the reference technology, chemical absorption in MonoEthanolAmine (MEA). In this CO2 concentration range, a minimum energy requirement lower than 3 GJth/ton CO2 is obtained (including compression of CO2 to 110 bar), with a CO2 recovery ratio above 85% and CO2 purity above 89%.

Two-Stage VPSA Process for CO2 Capture from Flue Gas Using Activated Carbon Beads

Carbon dioxide removal from flue gas with a two-stage vacuum pressure swing adsorption (VPSA) process, which uses activated carbon (AC) beads as the adsorbent, was investigated both theoretically and experimentally. First, single-column VPSA experiments were studied for CO2/N2 separation with high CO2 feed concentration. Then, a two-stage VPSA process composed two columns for each stage was designed, and the effects of different parameters were investigated. The first-stage VPSA unit operates with a four-step Skarstrom cycle, which includes feed pressurization, adsorption, blowdown, and counter-current purge with N2. For the second-stage VPSA process, a cycle with feed pressurization, adsorption, pressure equalization, blowdown and pressure equalization was employed. With the proposed two-stage VPSA process, a CO2 purity of 95.3% was obtained with 74.4% recovery. The total specific power consumption of the two-stage VPSA process is 723.6 kJ/kg-CO2, while the unit productivity is 0.85 mol-CO2/kg·h.

Hybrid Membrane Cryogenic Process for Post–combustion Co2 Capture

Reducing the energy requirement for the capture step is a major challenge in Carbon Capture and Storage (CCS) technology. Different capture processes have been investigated in the literature, such as absorption, adsorption, chemical looping and membrane separation. In this paper, the potential for a hybrid process combining membrane and cryogenic separation to achieve efficient post-combustion carbon capture has been investigated through a simulation study. The hybrid process combines a first step CO2 pre-concentration with a membrane unit and a second step CO2 cryogenic condensation. The influence of three CO2 feed contents (5, 15 and 30%), 3 different compression strategies and two membrane selectivities (a CO2/N2¼ 50 and 100) on the separation performances have been investigated for a required CO2 purity of 0.9 and a capture ratio larger than 85%. It is shown that the use the use of feed compression with Energy Recovery System (ERS) membrane module offers the best performances when energy requirement and membrane surface area taken into account. More specifically for a CO2 feed concentration ranging between 15 and 30%, the hybrid process shows a reduced energy requirement compared to the reference technology, chemical absorption in MonoEthanolAmine (MEA). In this CO2 concentration range, a minimum energy requirement lower than 3 GJth/ton CO2 is obtained (including compression of CO2 to 110 bar), with a CO2 recovery ratio above 85% and CO2 purity above 89%.

Separation of binary mixtures of carbon dioxide and methane through sulfonated polycarbonate membranes

AbstractPolycarbonate (PC) was sulfonated to varying degrees using acetyl sulfate. FTIR and NMR experiments were carried out to confirm sulfonation. The membranes were characterized by DSC and TGA to assess thermal stability. Ion exchange capacity (IEC) and degree of sulfonation (DS) were determined and their effect on permeation of CO2 and CH4 gases was investigated. Free volume fractions (FVF) of the membranes were found to decrease from 0.31 to 0.19 as the DS increased from 0 to 39.4%. Single gas permeation studies revealed that sulfonated PC exhibited higher selectivities than unmodified PC at reduced permeability. For a DS of 14.4%, sulfonated PC exhibited a selectivity of 36.1, which was 1.7 times that of unmodified PC, whereas the permeability dropped from 8.4 to 4.7 Barrers. In case of binary CO2/CH4 mixture permeation through PC membrane of the same DS, an increase in CO2 feed concentration from 5 to 40 mol % produced an increase in permeability from 0.24 to 2.0 Barrers and a rise in selectivity from 11.7 to 27.2 at constant feed pressure (20 bar) and temperature (30°C). A rise in the feed pressure from 5 to 30 bar at a constant feed composition of 5% CO2 resulted in a reduction in permeability from 0.38 to 0.2 Barrers and selectivity from 15.6 to 10.2. Sulfonated PC was found to be a promising candidate for separation of CO2 from CH4. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Production of Pipeline-Quality Natural Gas With the Molecular Gate CO2 Removal Process

Summary In May 2002, the first Molecular Gate* Carbon Dioxide Removal system for the removal of carbon dioxide and water was started at the Tidelands Oil Production Co. facility in Long Beach, California. The feed source for the unit is hydrocarbon-rich, water-saturated, associated gas from waterflood enhanced-oil-recovery (EOR) operations. The feed CO2 concentration varies widely and is typically more than 30%, while the unit reduces the carbon dioxide level to less than 2%. The unit removes the carbon dioxide, heavy hydrocarbons, and water-producing pipeline specification gas for sale to the local natural gas utility company.

Adsorption separation of CO<SUB align=right>2 from simulated flue gas mixtures by novel CO<SUB align=right>2 "molecular basket" adsorbents

Adsorption separation of CO2 from simulated flue gas mixtures containing CO2, O2, and N2 by using a novel CO2 "molecular basket" adsorbent was investigated in a flow adsorption separation system. The novel CO2 "molecular basket" adsorbents were developed by synthesising mesoporous molecular sieve MCM-41 and modifying it with polyethylenimine (PEI). The influence of operation conditions, including feed flow rate, temperature, feed CO2 concentration, and sweep gas flow rate, on the CO2 adsorption/desorption separation performance and CO2 breakthrough were examined. The CO2 adsorption capacity was 91.0 ml (STP)/g-PEI, which was 27 times higher than that of the MCM-41 alone. Further, the adsorbent showed separation selectivity of greater than 1000 for CO2/N2 ratio and approximately 180 for CO2/O2, which are significantly higher than those of the MCM-41, zeolites, and activated carbons. Cyclic adsorption/desorption measurements showed that the CO2 "molecular basket" adsorbent was stable at 75°C. However, the CO2 "molecular basket" adsorbent was not stable when the operation temperature was higher than 100°C.

Nonisothermal model for gas separation hollow‐fiber membranes

AbstractA model for multicomponent gas separation using hollow‐fiber membrane modules is presented that explicitly accounts for heating or cooling inside membrane permeators due to gas expansion. The model permits simulation of countercurrent contacting with permeate purging (or sweep). The numerical approach permits rapid and stable solutions for cases with many components, even when the mixture contains components with widely varying permeability coefficients. Simulation results are presented for natural‐gas sweetening, a commercially significant application, using polymer permeation properties similar to those of a high‐performance polyimide. For some conditions, temperature decreases from the feed to residue end of the module by as much as 40°C. As CO2 concentration in the feed increases or as stage cut increases, the temperature decrease from feed to residue increases. Relative to an isothermal case, expansion‐driven cooling reduces stage cut at a given feed flow rate since gas permeability decreases with decreasing temperature. Neglect of expansion‐driven cooling in natural‐gas separation simulations can lead to large errors in estimating the amount of feed gas that can be treated to achieve a fixed residue composition. For 30% CO2 feed concentration, if the effective membrane thickness is halved, only a 20% increase (rather than almost a factor of 2) in the amount of gas that can be treated per unit area is obtained due to the impact of expansion‐driven cooling on gas flux.

99/01178 Oxidative conversion of hydrocarbons into synthesis gas and unsaturated hydrocarbons assisted by gliding electric arcs : Czernichowski, P. and Czernichowski, A. PCT Int. Appl. WO 98 30,524 (Cl. C07CS/32), 16 Jul 1998, FR Appl. 97/364, 13 Jan 1997, 31 pp.

Syngas processing often requires separation of CO2 and hydrogen for hydrogen production, and the resulting CO2-enriched stream presents an opportunity for simultaneous CO2 capture. For example, syngas-based integrated gasification combined cycle (IGCC) power plants are envisioned as an efficient means of producing power from coal where CO2 capture technologies can be applied relatively easily. Membrane technology is an attractive approach for CO2 capture because of inherent process advantages such as simplicity, reliability, compactness and modularity. This paper (Part II of a two-part study) performs techno-economic analysis for CO2-selective membranes in three hydrogen production or utilization applications: methane reformer/pressure swing adsorption processes, oxygen-blown coal-fired IGCC power plants using GE gasification technology, and air-blown coal-fired IGCC power plants using Transport Integrated Gasification (TRIG) technology. These processes require membranes with CO2/H2 selectivities of 10–20, which can be provided using PolarisTM membranes. Hybrid approaches using a combination of membrane and cryogenic processes are evaluated for the production of high-pressure liquid CO2 ready for utilization or sequestration. The optimal membrane CO2/H2 selectivity and influence of CO2 capture rate on the cost of CO2 capture are determined, providing general guidelines for future membrane development. The cost of CO2 capture with these membrane processes depends not only on the feed CO2 partial pressure, but on the feed CO2 concentration as well.

CO2/CH4 separation by facilitated transport in amine‐polyethylene glycol mixtures

AbstractIn this work, the separation of carbon dioxide from methane by reactive liquid membranes consisting of the secondary amines, diethanolamine, and diisopropanolamine in polyethylene glycol with an average molecular weight of 400 was studied. A mathematical model was developed to describe the transport process. This model employs the zwitterion mechanism for the CO2 amine reaction kinetics. Membrane flux experiments utilizing a flat plate device were carried out to verify the model predictions. It was found that large permeabilities and separations were achieved for low CO2 feed concentrations. The results also show that DEA based solutions give better separation than DIPA based solutions.

Kinetics of CO oxidation over Co3O4/γ‐Al2O3. Part II: Reactor dynamics

AbstractThe transient responses of a fixed‐bed reactor to step increases and decreases in CO, O2, and/or CO2 feed concentrations were measured and interpreted. It is shown that dynamic methods yield vastly more phenomenological and mechanistic information than steady state measurements, with significantly less experimental effort.