CO2 Removal Process Research Articles

Long-term photosynthetic CO2 removal from biogas and flue-gas: Exploring the potential of closed photobioreactors for high-value biomass production

The long-term performance of a tubular photobioreactor interconnected to a gas absorption column for the abatement of CO2 from biogas and flue-gas was investigated. Additionally, a novel nitrogen feast-famine regime was implemented during the flue-gas feeding stage in order to promote the continuous storage of highly-energetic compounds. Results showed effective CO2 (~98%) and H2S (~99%) removals from synthetic biogas, supported by the high photosynthetic activity of microalgae which resulted in an alkaline pH (~10). In addition, CO2 removals of 99 and 91% were observed during the flue-gas operation depending on the nutrients source: mineral salt medium and digestate, respectively. A biomass productivity of ~8 g m−2 d−1 was obtained during both stages, with a complete nitrogen and carbon recovery from the cultivation broth. Moreover, the strategy of feeding nutrients during the dark period promoted the continuous accumulation of carbohydrates, their concentration increasing from 22% under normal nutrition up to 37% during the feast-famine cycle. This represents a productivity of ~3 g-carbohydrates m−2 d−1, which can be further valorized to contribute to the economic sustainability of the photosynthetic CO2 removal process.

Thermodynamic modelling using e-UNIQUAC model for CO2 absorption by novel amine solutions: 1-Dimethylamino- 2-propanol (1DMA2P), 3-dimethylamino-1-propanol (3DMA1P) and 4-diethylamino-2-butanol (DEAB)

The proper selection of thermodynamic models is an important step in the design and simulation of CO2 removal processes using amine solutions. In this study, we aim to study the thermodynamic behaviour of the CO2 removal process by employing the extended-universal quasichemical (e-UNIQUAC) model for three novel amine systems, namely CO2+1DMA2P + H2O, CO2+3DMA1P + H2O, and CO2+DEAB + H2O. The thermodynamic behaviour was studied in terms of the CO2 loading of amines, the ion speciation profiles, the isothermal pressure-composition (Pxy) profiles, and the pH of the amine solutions. Adjustable parameters of the model include binary interaction parameters, and the volume and surface area parameters of the amine and protonated amine were determined using different objective functions based on the experimental data available in the literature. The ion and molecular speciation profiles are obtained and compared with nuclear magnetic resonance (NMR) data for CO2+1DMA2P + H2O and CO2+DEAB + H2O systems. The model predicted the experimental data with average absolute relative deviations (AARDs) of 8.06%, 13.39% and 16.50% for CO2 loading values of DEAB, 1DMA2P, and 3DMA1P, respectively. In addition, the results of Pxy profiles at different temperatures show that the azeotrope does not form in the 3DMA1P + H2O system. The adjustable parameters and predicted data of the applied e-UNIQUAC model may contribute to the rate-based simulation of CO2 absorption processes using novel amine systems.

Enhancing mass transport in direct methanol fuel cell by optimizing the microstructure of anode microporous layer

The microstructural characteristics of the anode microporous layer (MPL) can significantly affect the mass transport in direct methanol fuel cells by influencing the methanol delivery and CO2 removal processes. The hydrophilic‐hydrophobic balance and pore structure of the flow path were established by optimizing the content of polytetrafluoroethylene (PTFE) in the anode MPL. An empirical model was developed to design and optimize the anode MPL to achieve better mass transport and cell performance. From the simulated and experimental results, increasing the content of PTFE enhanced the CO2 removal ability in the anode MPL, thereby alleviating CO2 blockage in the anode catalyst layer, whereas the narrowed flow path hindered methanol delivery in the anode MPL. A good balance between methanol delivery and CO2 removal in terms of mass transport was achieved when the PTFE content was adjusted to 15 wt %, leading to the best cell performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3519–3528, 2018

Ionic Liquid (1-Butyl-3-Metylimidazolium Methane Sulphonate) Corrosion and Energy Analysis for High Pressure CO2 Absorption Process

This study explores the possible use of ionic liquids as a solvent in a commercial high-pressure CO2 removal process, to gain environmental and energy benefits. There are two main constraints in realizing this: ionic liquids can be corrosive, specifically when mixed with a water/amine solution with dissolved O2 & CO2; and CO2 absorption within this process is not very well understood. Therefore, scavenging CO2 to ppm levels from process gas comes with several risks. We used 1-butyl-3-methylimidazoium methane sulphonate [bmim][MS] as an ionic liquid because of its high corrosiveness (due to its acidic nature) to estimate the ranges of expected corrosion in the process. TAFEL technique was used to determine these rates. Further, the process was simulated based on the conventional absorption–desorption process using ASPEN HYSYS v 8.6. After preliminary model validation with the amine solution, [bmim][MS] was modeled based on the properties found in the literature. The energy comparison was then provided and the optimum ratio of the ionic liquid/amine solution was calculated.

Initial solubility & density evaluation of Non-Aqueous system of amino acid salts for CO2 capture: potassium prolinate blended with ethanol and ethylene glycol

Amine scrubbing is the state of the art technology for CO2 capture, and solvent selection can significantly reduce the capital and energy cost of the process. Higher energy requirement for aqueous amine based CO2 removal process is still a most important downside preventive its industrial deployment. Therefore, in this study, novel non-aqueous based amino acid salt system consisting of potassium prolinate, ethanol and ethylene glycol has been studied. This work presents initial CO2 solubility study and important physical properties i.e. density of the studied solvent system. Previous work showed that non-aqueous system of potassium prolinate and ethanol has good absorption rates and requires lower energy for solvent regeneration. However, during regeneration, solvent loss issues were found due to lower boiling point of the ethanol. Therefore, ethylene glycol was added into current studied system for enhancing the overall boiling point of the system. The good initial CO2 solubility and low density of studied solvent system offers several advantages as compared to conventional amine solutions.

Enhancement of separation performance of nano hybrid PES –TiO2 membrane using three combination effects of ultraviolet irradiation, ethanol-acetone immersion, and thermal annealing process for CO2 removal

Separation of CO2/CH4 is an essential process in methane-based fuel gas production. The membrane system is currently developed for gas separation due to its small footprint, low capital cost and operating cost, environmentally friendly, and process flexibility. The main purpose of research in the membrane for gas separation is to develop novel membranes with high performance, following by high permeability and selectivity. In this paper, nano-hybrid polyethersulfone (PES) membranes contained nano TiO2 are fabricated and evaluated for CO2 removal. The nano-hybrid PES membranes are fabricated using dry-wet phase inversion to form flat sheet membranes, with nano TiO2 concentrations are 0.5%-wt, 1%-wt, and 1.5%-wt, respectively. For modification purpose, the membrane was subjected by irradiated under UV rays for 1, 2, 3 min, immersion in the ethanol-acetone mixture, and then followed by thermal annealing for 20 s at 180 °C. Experimental results show that the nano-hybrid PES-nano TiO2 with 0.5 wt-% nanoparticles loading showed the best pweformance in term gas permeability. Indeed, the combinations of UV rays irradiation, immersion in the ethanol-acetone mixture, and thermal annealing combination treatments exhibited the best performance. In this study, the CO2 permeability and selectivity gas CO2/CH4 for modified membrane are 680.60 GPU and 43.09, respectively. It is expected that this study can guidance for improving new strategies to facilitate nanohybrid PES – nano TiO2 membrane for CO2 removal in CH4.

Scale-up of amine-containing thin-film composite membranes for CO2 capture from flue gas

Membrane technology is a cost-effective and energy-efficient separation process for CO2 removal from flue gas. Recently, there have been remarkable advances in the development of polyvinylamine (PVAm)/piperazine glycinate (PG)-containing facilitated transport membranes for CO2 removal. The advanced PVAm/PG-containing membranes have demonstrated desirably high CO2/N2 selectivity of greater than 140 and good CO2 permeance of > 700 GPU (1 GPU = 10−6 cm3 (STP)/(s cm2 cmHg)) at the typical flue gas temperature of 57 °C. This work investigated the scale-up fabrication of the PVAm/PG-containing membranes and demonstrated it successfully. Effective and efficient continuous fabrication of the membranes in a roll-to-roll manner was developed using the thin-film coating (TFC) assembly of the pilot-scale machine at Ohio State. The design of the TFC assembly was improved and several operating parameters were optimized for the fabrication with desirable membrane thickness and gas transport performance. A total of > 2000 feet long and 14-in. wide membranes with a selective layer thickness of < 200 nm was successfully fabricated. In addition, small representative samples taken from the scale-up membranes were tested, showing the CO2 permeance and CO2/N2 selectivity at 57 °C in reasonably good agreement with those obtained from the lab-synthesized membranes.

Molecular Dynamics Study of the Solution Structure, Clustering, and Diffusion of Four Aqueous Alkanolamines.

CO2 sequestration from anthropogenic resources is a challenge to the design of environmental processes at a large scale. Reversible chemical absorption by amine-based solvents is one of the most efficient methods of CO2 removal. Molecular simulation techniques are very useful tools to investigate CO2 binding by aqueous alkanolamine molecules for further technological application. In the present work, we have performed detailed atomistic molecular dynamics simulations of aqueous solutions of three prototype amines: monoethanolamine (MEA) as a standard, 3-aminopropanol (MPA), 2-methylaminoethanol (MMEA), and 4-diethylamino-2-butanol (DEAB) as potential novel CO2 absorptive solvents. Solvent densities, radial distribution functions, cluster size distributions, hydrogen-bonding statistics, and diffusion coefficients for a full range of mixture compositions have been obtained. The solvent densities and diffusion coefficients from simulations are in good agreement with those in the experiment. In aqueous solution, MEA, MPA, and MMEA molecules prefer to be fully solvated by water molecules, whereas DEAB molecules tend to self-aggregate. In a range from 30/70-50/50 (w/w) alkanolamine/water mixtures, they form a bicontinuous phase (both alkanolamine and water are organized in two mutually percolating clusters). Among the studied aqueous alkanolamine solutions, the diffusion coefficients decrease in the following order MEA > MPA = MMEA > DEAB. With an increase of water content, the diffusion coefficients increase for all studied alkanolamines. The presented results are a first step for process-scale simulation and provide important qualitative and quantitative information for the design and engineering of efficient new CO2 removal processes.

Retuning PI controller to improve the control performance in CO2 removal process, subang field

A proportional - integral controller retuning is performed on CO2 removal process, Subang field. Retuning is carried out to improve the control performance on the process. The method used is to evaluate the controllers that are retuned the controller parameters, identify the system using the first-order plus dead time model (FOPDT), tune the controller parameters using the Ziegler-Nichols, Wahid-Rudi-Victor (WRV), Cohen-Coon, autotuning, and fine tuning, and the last, the control performance tests using set point (SP) tracking and disturbance rejection with performance indicator is integral of square error (ISE). The result is that there are three controllers that are retuning the control parameters, i.e., the feed gas pressure control (PIC - 1101), the makeup water flow control (FIC - 1102), and the amine circulation flow control (FIC - 1103). Only a fine tuning method produces the best control performance compared to previous settings in the field, with performance improvements of 77,42% (PIC - 1101), 90,59% (FIC - 1102), and 13,06% (FIC - 1103) for -5% set point (SP) tracking. While for disturbance rejection, fine tuning gives performance improvements of 86,04% (PIC - 1101), 90,8% (FIC - 1102), and 24,8% (FIC - 1103). Thus, retuning PI controllers work well.

Application of multivariable model predictive control to overcome the intervariable interaction in CO2 removal process

Multivariable model predictive control (MMPC) was applied in CO2 removal process in a natural gas treatment from an industry located in Subang field, which used chemical absorption. MMPC is a variation of model predictive control (MPC) which can account for more than one control variable at once and is classified in advanced control category. MMPC is expected to give a better performance in handling the process as well as being able to overcome intervariable interaction that is prone to happen in multiple input multiple output (MIMO) system. MMPC was applied in the process to get a better process control performance compared to the one using PI controller and to make any intervariable interaction in the process more manageable. The indicator for each goal was integral square error (ISE). The result showed that identified intervariable interaction was between the pressure of gas feed in and the flow of make-up water to absorber. By using MMPC, the ISE of controller’s performance was improved from the PI-controller that was used in the plant. The improvement for ISE was 32.62% (PIC-1101) and 72.67% (FIC-1102) in the SP tracking, and 52.54% (PIC-1101) and 57.41% (FIC-1102) in the disturbance rejection. MMPC implementation also showed a better response in handling intervariable interaction in the process.

Study of the robustness of a low-temperature dual-pressure process for removal of CO2 from natural gas

The growing use of energy by most of world population and the consequent increasing demand for energy are making unexploited low quality gas reserves interesting from an industrial point of view. To meet the required specifications for a natural gas grid, some compounds need to be removed from the sour stream. Because of the high content of undesired compounds (i.e., CO2) in the stream to be treated, traditional purification processes may be too energy intensive and the overall system may result unprofitable, therefore new technologies are under study. In this work, a new process for the purification of natural gas based on a low temperature distillation has been studied, focusing on the dynamics of the system. The robustness of the process has been studied by dynamic simulation of an industrial-scale plant, with particular regard to the performances when operating conditions are changed. The results show that the process can obtain the methane product with a high purity and avoid the solidification of carbon dioxide.

Novel dense skin hollow fiber membrane contactor based process for CO2 removal from raw biogas using water as absorbent

Abstract CO2 removal from raw biogas is required in order to meet standards for the gas grid or as a vehicle fuel. Among biogas upgrading available techniques, pressurized water absorption using packed column (PWA) is one of the most well-established technique. In this work, a novel absorption/desorption loop using dense based hollow fiber membrane contactor (HFMC) process and water as absorbent is proposed and investigated by simulation. Thanks to the ability of dense membranes to withstand a high transmembrane pressure, neither water depressurization before the desorber nor water recompression before the absorber is needed. 1D modeling based on a resistances in series approach is used for the modeling of both absorption and desorption units. HFMC process performances are compared to state of the art packed column (PWA) process reported in literature. Using commercially available dense based HFMC, the process is able to recover 96.6% of CO2 and reach biomethane purity of 98%. The corresponding energy requirement is of 0.17 kWh/Nm3 of raw biogas, which is 20 to 35% lower than that reported for packed column based process, under comparable gas inlet conditions and product specifications. HFMC process offers absorption intensification factor of about 1.68, corresponding to a volumetric reduction of about 68% of the absorption unit. Under the investigated operating conditions and due of the preponderant liquid side mass transfer resistance, process selectivity is mainly controlled by the absorbent selectivity. Without flash recovery, CH4 loss is of about 8%. No significant methane loss reduction is obtained from increasing membrane selectivity from 17 to 60 with membrane mass transfer coefficient of 5.10-4 and 5.10-5 m/s respectively. Perspectives for further process optimization are exposed.

Prediction of heat capacity of amine solutions using artificial neural network and thermodynamic models for CO2 capture processes

In this study, artificial neural network (ANN) and thermodynamic models were developed for prediction of the heat capacity (C P ) of amine-based solvents. For ANN model, independent variables such as concentration, temperature, molecular weight and CO2 loading of amine were selected as the inputs of the model. The significance of the input variables of the ANN model on the C P values was investigated statistically by analyzing of correlation matrix. A thermodynamic model based on the Redlich-Kister equation was used to correlate the excess molar heat capacity $$ \left({C}_P^E\right) $$ data as function of temperature. In addition, the effects of temperature and CO2 loading at different concentrations of conventional amines on the C P values were investigated. Both models were validated against experimental data and very good results were obtained between two mentioned models and experimental data of C P collected from various literatures. The AARD between ANN model results and experimental data of C P for 47 systems of amine-based solvents studied was 4.3%. For conventional amines, the AARD for ANN model and thermodynamic model in comparison with experimental data were 0.59% and 0.57%, respectively. The results showed that both ANN and Redlich-Kister models can be used as a practical tool for simulation and designing of CO2 removal processes by using amine solutions.

Mesoporous alumina and alumina-titania supported KCuFe catalyst for Fischer-Tropsch synthesis: Effects of CO2 and CH4 present in syngas

In this work, mesoporous alumina (mAl2O3) and alumina-titania (mAl2O3-TiO2) were synthesized and used as support materials for promoted (K, Cu) iron catalyst. The catalysts were tested for Fischer-Tropsch synthesis in a fixed bed flow reactor operating at 2000h−1 GHSV, 270°C, 330psi and H2/CO ratio of 1.25. The catalytic activity was measured in terms of CO conversion, CO2 selectivity and hydrocarbon selectivity. The catalyst KCuFe/mAl2O3 performed better and showed ~17% higher CO conversion to hydrocarbons as compared to that shown by KCuFe/γ-Al2O3.The effect of CO2 and CH4 present in produced syngas (through gasification/reforming) and recycled syngas was also studied for KCuFe/mAl2O3 and KCuFe/mAl2O3-TiO2 catalyst. 0–15% of CO2 and 0–12.5% of CH4 was added in syngas, while maintaining GHSV constant. Methane in syngas acted as diluent and resulted in increase in CO residence time, which helps in increase in CO conversion. However, increase in CO conversion and decrease in partial pressure of CO leads to increase in CH4 and CO2 selectivity, thus, lowering the amount of percentage of CO converted to C5+ hydrocarbons. Addition of CO2 in syngas leads to decrease in CO2 selectivity, indicating hydrogenation of CO2 to hydrocarbons. Hence, slight increase in amount of percent CO converted to hydrocarbons was observed. Both catalysts showed increase in chain growth probability and alcohol production with increasing CH4 and CO2 content in syngas. However, the catalyst KCuFe/mAl2O3 performed better with CO2 and CH4 present in syngas, and has the potential to bring economic benefits to FTS process by relaxing the expensive syngas purification process for complete removal of CO2 and CH4.

High-efficiency negative-carbon emission power generation from integrated solid-oxide fuel cell and calciner

Direct air capture of CO2 has the potential to help meet the ambitious environmental targets established by the Paris Agreement. This study assessed the techno-economic feasibility of a process for simultaneous power generation and CO2 removal from the air using solid sorbents. The process uses a solid-oxide fuel cell to convert the chemical energy of fuel to electricity and high-grade heat, the latter of which can be utilised to calcine a carbonate material that, in turn, can remove CO2 from the air. The proposed process was shown to operate with a net thermal efficiency of 43.7–47.7%LHV and to have the potential to remove 463.5–882.3 gCO2/kWelh, depending on the fresh material used in the calciner. Importantly, the estimated capital cost of the proposed process (1397.9–1740.5 £/kWel,gross) was found to be lower than that for other low-carbon emission power generation systems using fossil fuels. The proposed process was also shown to achieve a levelised cost of electricity of 50 £/MWelh, which is competitive with other low-carbon power generation technologies, for a carbon tax varying between 39.2 and 74.9 £/tCO2. Such figure associated with the levelised cost of CO2 capture from air is lower than for other direct air concepts.

Purification of Aggressive Supercritical Natural Gas Using Carbon Molecular Sieve Hollow Fiber Membranes

In this paper, we describe polyimide-derived carbon molecular sieve (CMS) hollow fiber membranes with CO2/CH4 separation factors ∼60 under a supercritical (1800 psia) natural gas feed comprising 50% CO2 and 500 ppm highly condensable C7 hydrocarbons. Long-term tests extending for 200 h proved membrane stability. Temperatures ranging from −50 to 100 °C were also tested, and the membrane showed attractive performance under the diverse conditions studied. With attractive and stable separation performance, the CMS hollow fiber membranes studied in this work can potentially enable next-generation CO2 removal processes for challenging natural gas feeds.

Simulation Model Evaluation of CO2 Capture by Aqueous MEA Scrubbing for Heat Requirement Analyses

Carbon dioxide is a powerful greenhouse gas, whose massive presence in the atmosphere causes gradual global warming. Absorption by means of chemical solvents is the most commonly used process for CO2 removal. It can be applied to gaseous streams in power plants, natural gas, and refinery gas. Amine scrubbing is widely considered the most mature technology for PCC (post-combustion CO2 capture), and 30% wt. MEA aqueous solution can be taken as the baseline solvent to be used as reference for studies focused on modelling and simulation. Thermodynamics, kinetics and mass transfer influence the chemical absorption process. The thermodynamic model exerts an influence also on the determination of the overall heat of absorption of the acid gas in the solvent, being the heat released at chemical equilibrium related to the extent of reactions. Its estimation is of paramount importance, since it is directly related to the energy requirement at the reboiler of the solvent regeneration column and determines the temperature profile along the absorber. The model used in this work has been previously validated by comparison with data of absorption performances with regard to mass transfer phenomenon. In this work, results obtained from simulations have been checked against experimental data, by focusing on the thermodynamic framework and its influence on the evaluation of the reboiler duty, for possible energy saving solutions in scale-up design.

Gas Separation Process for CO2 Removal from Natural Gas with DDR-type Zeolite Membrane

The DDR-type zeolite membrane (DDR Membrane) with an aperture of 0.36 × 0.44nm was formed on a porous alumina substrate by hydrothermal process. We have succeeded in scaling up the DDR Membrane element into a large monolithic structure with a diameter and length of 180mm and 1,000mm, respectively. The CO2/CH4 selectivity exceeded 100 for mixed gas of 70 mol% CO2 at 8.0 MPag, 45 degC. This high selectivity improves hydrocarbon recovery compared to the conventional polymeric membrane. The DDR Membrane is suitable for CO2 separation for high CO2 natural gas fields.

Degradation and Emission Results of Amine Plant Operations from MEA Testing at the CO2 Technology Centre Mongstad

In 2015, the CO2 Technology Centre Mongstad (TCM DA), operated a test campaign using aqueous monoethanolamine (MEA) solvent at 30 wt%. The main objective was to demonstrate and document the performance of the TCM DA Amine Plant located in Mongstad, Norway. This paper will present several aspects concerning degradation of the solvent and atmospheric emissions from amine based CO2 removal processes. The work aims to; (1) quantify the amounts and compositions of the degraded solvent (2) report results from atmospheric emissions measurements of amines and amine based degradation products; and (3) present Ambient Air measurement done during a 2 month campaign.

Optimized Simulation of CO2 Removal Process from Coal Fired Power Plants with MEA by Sensitivity Analysis in Aspen plus

The World Energy consumption has been increasing steadily since industrialization, this recent increase is also the major cause for the raise of CO2 concentration in the atmosphere. Fossil fuels play a central role in our energy consumption; actually the CCS technology and their operations in power systems must get a prominent role in reducing total CO2 emissions. An attempt to tackle the problem of solvent based Post Combustion Carbon Capture process optimization requires the availability of a rigorous process model along with a design methodology. During the modeling, much physical and chemical process should be considered in order to get more realistic results, this complexity process addressed as Reactive Separation. This report presents detailed descriptions of the process sections as well as technical documentation for the ASPEN Plus simulations including the design basis, models employed, key assumptions, design parameters, convergence algorithms, concentration and temperature profiles and calculated outputs. The main purpose is to minimize the amount of energy required in the desorption process through the optimum operating condition to the actual CO2 absorption experimental setup. The case of study is on MEA 30wt% in a coal Hired power plant. Electrolytic method is considered; the sensitive analysis was used for the Optimization.