CO2 Capture Rate Research Articles

Solubility of CO2 in Ionic Liquids with Additional Water and Methanol: Modeling with PC-SAFT Equation of State

The superior properties of specific ionic liquids (ILs), such as negligible volatility, high thermal stability, flexible designability, and their affinity to capture CO2, make them an attractive alternative to chemical and physical solvents that are currently used in CO2 capture processes. However, a limitation to use ILs for industrial CO2 capture is their high viscosity compared to conventional solvents, which leads to a lower CO2 capture rate and higher pumping cost. The viscosity of ILs can be reduced by adding a co-solvent, such as water or methanol. In this work, solubility, vapor–liquid equilibria (VLE), and liquid–liquid equilibria (LLE) for binary and ternary mixtures involving CO2, ILs, water, and methanol have been systematically investigated by employing perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state with two different strategies. ILs were considered as self-associating chain molecules with two association sites in the first strategy. As a comparison, they were regarded as strong electrolytes that dissociate into anions and cations in the second strategy. It was found that both strategies provide accurate correlations in modeling CO2 solubilities in ILs and LLE of binary ILs/water systems. Four ternary systems were selected to verify the predictive capability of the two strategies. For water-containing systems, both strategies performed excellently when binary interaction parameters (BIPs) can be obtained by fitting to experimental data, while they performed poorly for system with few experimental data. For cases where methanol acted as a co-solvent, accurate predictions were obtained with both strategies, even without any BIPs. PC-SAFT was found to be a potential practical tool to develop CO2 capture processes with new alternative solvents when there are sufficient experimental data for binary mixtures.

Capture of CO2 from Steam Reformer Flue Gases Using Monoethanolamine: Pilot Plant Validation and Process Design for Partial Capture

Carbon dioxide (CO2) capture from a slipstream of steam reformer flue gas (18–20 vol %wet CO2) using 30 wt % aqueous monoethanolamine was performed for ∼500 h in a mobile test unit (∼120 kg CO2/h). Specific reboiler duties (SRDs) of 3.6–3.8 MJ/kg CO2 were achieved at 90% capture. The pilot data validate the modeling of off-design partial capture, that is, operation at lower CO2 capture rates (at constant gas flow) than the absorption column was designed to achieve. This paper demonstrates that off-design partial capture enables significant energy savings (SRD, cooling) relative to on-design capture. The accrued savings depend on the column design (packing height, flooding approach) and the feed CO2 concentration. Finally, a concept for stepwise deployment of carbon capture and storage in industries with high-CO2 concentration sources (e.g., steel and cement manufacturing and refining) is introduced. Thanks to its inherent full-capture-ready design, the initial energy-efficient, off-design partial capture operation can be extended to full capture over time.

The impact of climate on solvent-based direct air capture systems

Direct air capture (DAC) is increasingly seen as a critical technology to reach mid-century net-zero targets and limit climate change to well below 2 °C. While the commercialization of DAC technologies is being pursued by numerous companies, there remains remarkably little information on their performance under “real-world” conditions. In this paper, for the first time, we investigate the influence of temperature and relative humidity of air on the CO2 capture rate at the air contactor, overall energy requirement, CO2 capture efficiency, and levelized cost of liquid-solvent based DAC systems. We observe that the overall energy demand decreases from 11.1 to 8.3 GJ/tCO2 as the CO2 capture rate increases from 40 to 85 % and that high capture rates can only be achieved in hot and humid climate conditions. We observe that a CO2 capture rate of 75 % is only possible above 17 °C and 90 % relative humidity, and this drops dramatically at lower temperatures. It is also observed that water evaporation in the air contactor is highest at dry and low relative humidity, as expected. The sensitivity analysis showed that CO2 capture efficiency is relatively insensitive to climate conditions for the liquid-solvent based DAC plant. Lastly, the levelized cost of natural gas standalone scenario varies from $240/tCO2 to $409/tCO2, and this is more sensitive to temperature than relative humidity. The levelized cost of the natural gas stand-alone case is between 7 % and 10 % lower than that of an electric grid-connected case across all climate conditions.

Energy and economic analysis feasibility of CO2capture on a natural gas internal combustion engine

AbstractCO2capture by amine scrubbing is a widely developed technology in its most advanced stage of evolution. However, it has never been used to capture CO2from mobile sources. The present study performs an energy and economic analysis of an amine scrubbing CO2capture storage (CCS) system, which takes for the amine regeneration process the waste heat from the exhaust gases of a turbocharged natural gas internal combustion engine (mobile source). The selected engine for the study is an M936G, widely used in freight and passenger transport. A primary and a tertiary amine were chosen for the simulations. In order to reduce volume and increase autonomy, captured CO2is stored as a liquid, therefore, a specific installation is planned. The system is hybridised with an organic rankine cycle (ORC) to reduce the energy penalty on the CCS system. Results show that a CCS system operating with Monoethanolamine (MEA) at 30 wt% achieved a maximum CO2capture rate of 66%, with a penalty over the power engine of only 10%. On the other hand, the economic analysis showed that the CCS system with MEA and without ORC is 31.8% cheaper than a hydrogen fuel cells bus and 26% cheaper than a battery‐electric bus. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

The FastCarb project: Taking advantage of the accelerated carbonation of recycled concrete aggregates

Recycled concrete aggregates (RCA) incorporate hydrates that can be carbonated. The FastCarb project aims to mineralize CO2 within RCA, improving the quality of these aggregates by the clogging of the porosity and finally decreasing the CO2 impact of concrete in structures. It has two main objectives: to optimize in laboratory conditions the accelerated carbonation process which can be transposed at an industrial scale at a suitable cost and to show that the process could be used in industrial conditions. This paper presents firstly the results obtained in laboratory conditions: it confirms that it is possible to store between 10 and 50 kg of CO2/t of RCA depending on several factors (natural carbonation, water content, temperature, size of RCA…) and that the treatment allows an improvement of the properties like the water absorption. The feasibility of accelerated carbonation has been also demonstrated by setting up two industrial-scale demonstrators. The first results without optimization showed a CO2 capture rate in the order of 3–4 %, i.e. 30 kg of CO2 per ton of crushed concrete. 80 t of carbonated RCA were produced and used to produce C25/30 and C45/55 concretes. The measurement of the main properties (performance in the fresh state, mechanical performance, and durability) shows that the use of the carbonated RCA doesn’t affect these properties. A variety of precast products (blocks, curbs, stairs) and parts of cast-in-situ structures (construction of walls) were fabricated showing the feasibility of using these aggregates in real situations. Finally, our project considers whether the accelerated carbonation process is environmentally acceptable and economically viable. The first results show that the distance of transport (by trucks) is a major factor and that transportation should be limited to maintain a positive impact of the accelerated carbonation (i.e. local sources of CO2 should be used). The LCA and the economic study confirm that the sand fraction of RCA is the most interesting material for the uptake of CO2. This is also interesting for a circular economy objective because recycled concrete sand is not easily used in concrete made with RCA.

Study of an integrated gas turbine -Molten carbonate fuel cell-organic Rankine cycle system with CO2 recovery

A huge amount of energy is consumed by recovering CO2 in the gas turbine (GT) exhaust gas with the traditional method because of the low CO2 concentration. A new system integrated with gas turbine, MCFC and ORC with CO2 capture is proposed in this article. CO2 in the gas turbine exhaust gas is concentrated by the MCFC electrochemical reaction. Compared with traditional CO2 capture methods, it effectively decreases the energy consumption of CO2 capture. The mid-temperature exhaust gas heat is recovered by two stages organic Rankine cycle systems. The influences of the major parameters on the new system performance are deeply studied. Also, the thermal and economic performances of the new system are compared with those of the reference system without CO2 capture and with CO2 capture based on the traditional mono-ethanol ammine (MEA) method. The results show that, when the CO2 capture rate is 0.85, the thermal efficiency of the new system is 62.34%, 3 percentage points higher than that of the gas steam combined cycle system without CO2 capture; and the exergy efficiency is 60.08%, 2.47 percentage points higher than that of the gas steam combined cycle system without CO2 capture. Its economic performance will be improved with the reduction of the MCFC cost in the future.

Chemical looping combustion of lignite using iron ore modified by foreign ions: Alkaline-earth and transition metal ions

In the chemical looping combustion (CLC) of lignite, oxygen carrier reactivity is the key to combustion performance. In this paper, the effects of particle size and temperature upon the CLC of lignite are investigated in a fixed bed reactor using iron ore as the oxygen carrier. Under optimized working conditions, the iron ores are loaded with alkaline-earth metals (K, Na and Ca) and transition metals (Ni, Mn and Cu) in a mass ratio of 10%, and their effect upon its CLC reactivity are studied. The carbon conversion rate, carbon capture rate, CO2 capture rate, CO2 selectivity, and other parameters are obtained. The size of lignite particles had a direct effect on the carbon capture rate of the fuel reactor. The particle size with the best effect on carbon and CO2 capture for both the Yunnan and Yizhong lignite is 80–200 mesh. The increase in temperature effectively promotes the reaction between oxygen carrier and volatiles, thereby resulting in an increase in CO2 concentration. The capacity of the oxygen carrier to transform the lignite is effectively enhanced by the modification with Cu, K, Na, Ca and Mn. In particular, the CO2 selectivity is greatly improved (up to 94.84%) for the Cu-modified oxygen carrier. These results provide important references for the CLC process, especially for the design of the oxygen carrier.

Attached microalgae converting spent coffee ground into lipid for biodiesel production and sequestering atmospheric CO2 simultaneously

The impacts of simultaneous exposures of arbitrary light intensities and photoperiods on attached Chlorella vulgaris microalgal growth onto spent coffee ground (SCG) were studied, and subsequently optimized using Response Surface Methodology (RSM) tool. The statistical analysis revealed the optimum light intensity and photoperiod were achieved at 100 μmol/m2s and 20:4 dark:light hours/cycle, respectively, producing microalgal density of 0.358 g/g and lipid productivity of 16.8 mg/Lday. The biodiesel yielded from the optimum condition possessed high cetane number and oxidative stability due to the high saturated fatty acid methyl esters (FAME) content of 63.7 %. In fact, the major FAME compositions ranged within C16 to C18 which were favourable for quality biodiesel production. Furthermore, the viability of SCG to serve as a carbon source was also evidenced by the high productivities of microalgal protein and carbohydrate at 94 and 168 mg/L day, respectively. The capability of attached microalgal cultivation in sequestering atmospheric CO2 was finally unveiled, with high CO2 capture rate being recorded at 9.38 mg/L h. Accordingly, growing attached microalgae onto SCG was recognized as an alternative approach for sustainable CO2 reduction, while producing green diesel to assuage the global warming phenomenon.

The role of energy supply in abatement cost curves for CO2 capture from process industry – A case study of a Swedish refinery

Carbon capture and storage (CCS) activities need to be ramped up to address the climate crisis. Abatement cost curves can help to identify low-cost starting points and formulate roadmaps for the implementation of CCS at industrial sites. In this work, we introduce the concept of energy supply cost curves to enhance the usefulness and accuracy of abatement cost curves. We use a multi-period mixed-integer linear programming (MILP) approach to find an optimal mix of heat sources considering the existing site energy system. For a Swedish refinery, we found that residual heat and existing boiler capacities can provide the heat necessary for CCS that avoids >75% of the site’s CO2 emissions. Disregarding the existing site energy system and relying on new heat supply capacities instead, would lead to capture costs that are 40–57% higher per tonne of CO2-avoided (excl. CO2 liquefaction, transport, and final storage). Furthermore, we estimated that temporal variations of heat sources (intermittent residual heat) increases the heat supply cost and emissions by 7–26% and 9–66%, respectively. The proposed method for optimization of the energy supply mix considering temporal variations of heat sources enables detailed estimates of energy supply costs for CO2 capture rates ranging from partial to full capture, and thus, improve abatement cost curves.

Integration of molten carbonate fuel cell and chemical looping air separation for high-efficient power generation and CO2 capture

Molten carbonate fuel cell (MCFC) allows concentrating the CO2 from the cathode side to the anode side, generating electricity concurrently. Chemical looping air separation (CLAS) can produce an O2 and CO2 mixture stream as cathode feeding gas of MCFC. In this paper, a natural gas-fueled MCFC with internal reforming is integrated with CLAS as O2 and CO2 source for high-efficient power generation with CO2 capture. An O2 and CO2 mixture stream is produced from CLAS by recirculating a portion of CO2-rich flue gas after the afterburner to CLAS. The system is analyzed through thermodynamic and economic performance. At the baseline case, the plant net power efficiency is 59.5%, with 99.9% CO2 capture rate. Based on sensitivity analysis, the higher fuel cell temperature and fuel utilization factor can increase the plant net power efficiency, while the steam carbon ratio and the CLAS reduction reactor temperature are preferable to be at lower levels for higher plant net power efficiency. Finally, economic analysis is conducted. With a MCFC specific cost of $1327/kW and a natural gas price of $2.79/million Btu, the cost of electricity (COE) is $0.094/kWh. The results show the proposed system is attractive for natural gas-fueled power generation with CO2 capture.

Direct Air Capture of CO2 Using a Liquid Amine-Solid Carbamic Acid Phase-Separation System Using Diamines Bearing an Aminocyclohexyl Group.

The phase separation between a liquid amine and the solid carbamic acid exhibited >99% CO2 removal efficiency under a 400 ppm CO2 flow system using diamines bearing an aminocyclohexyl group. Among them, isophorone diamine [IPDA; 3-(aminomethyl)-3,5,5-trimethylcyclohexylamine] exhibited the highest CO2 removal efficiency. IPDA reacted with CO2 in a CO2/IPDA molar ratio of ≥1 even in H2O as a solvent. The captured CO2 was completely desorbed at 333 K because the dissolved carbamate ion releases CO2 at low temperatures. The reusability of IPDA under CO2 adsorption-and-desorption cycles without degradation, the >99% efficiency kept for 100 h under direct air capture conditions, and the high CO2 capture rate (201 mmol/h for 1 mol of amine) suggest that the phase separation system using IPDA is robust and durable for practical use.

DMC-PID cascade control for MEA-based post-combustion CO2 capture process

The capture and recovery of carbon dioxide (CO2), the main source of greenhouse gases, are the principal means to reduce CO2 emissions. The optimization and control of the CO2 capture process plays a vital role in reducing energy costs, with the post-combustion CO2 capture (PCC) device using amine-based solvents considered to be the most feasible strategy to reduce CO2 emissions from coal-fired thermal power plants. In this paper, a DMC-PID cascade strategy is proposed to manipulate the PCC process order to obtain better performance. PID algorithm is used to adjust the flue gas flow to stabilize the flue gas entering absorber, and DMC algorithm is adopted to manipulate and constrain the lean solvent flow optimally order to increase CO2 capture rate. First, the corresponding steady-state model is established in Aspen Plus to get the best operating point parameters. Next, a dynamic model is built in Aspen Plus Dynamics to analyze the dynamic changes between the main variables of the system through dynamic testing, and the transfer function of the system is obtained through experimental data. Finally, three control strategies of DMC-PID, PID-PID and DMC are used to compare the control effect of CO2 capture rate. The results show that the proposed DMC-PID cascade control strategy has better performance, which improves the stability and flexibility of the PCC system, and provides a more feasible and effective operation for the CO2 capture.

Sensitivity Analysis and Cost Estimation of a CO2 Capture Plant in Aspen HYSYS

A standard CO2 capture process is implemented in Aspen HYSYS, simulated, and evaluated based on available data from Fortum’s waste burning facility at Klemetsrud in Norway. Since amine-based CO2 removal has high costs, the main aim is cost-optimizing. A simplified carbon-capture unit with a 20-m absorber packing height, 90% CO2 removal efficiency, and a minimum approach temperature for the lean/rich amine heat exchanger (ΔTmin) of 10 °C was considered the base case simulation model. A sensitivity analysis was performed to optimize these parameters. For the base case study, CO2 captured cost was calculated as 37.5 EUR/t. When the sensitivity analysis changes the size, the Power Law method adjusts the equipment cost. A comparison of the Enhanced Detailed Factor (EDF) and the Power Law approach was performed for all simulations to evaluate the uncertainties in the findings from the Power Law method. The optimums calculated for ΔTmin and CO2 capture rate were 15 °C and 87% for both methods, with CO2 removal costs of 37 EUR/t CO2 and 36.7 EUR/t CO2, respectively. With 19 m of packing height to absorber, the minimum CO2 capture cost was calculated as 37.3 EUR/t and 37.1 EUR/t for the EDF and Power Law methods, respectively. Since there was a difference between the Power Law method and the EDF method, a size factor exponent derivation was performed. The derivation resulted in the following exponents: for the lean heat exchanger 0.74, for the lean/rich heat exchanger 1.03, for the condenser 0.68, for the reboiler 0.92, for the pump 0.88, and for the fan 0.23.

Modeling of Vacuum Temperature Swing Adsorption for Direct Air Capture Using Aspen Adsorption

The paper evaluates the performance of an adsorption-based technology for CO2 capture directly from the air at the industrial scale. The approach is based on detailed mass and energy balance dynamic modeling of the vacuum temperature swing adsorption (VTSA) process in Aspen Adsorption software. The first step of the approach aims to validate the modeling thanks to published experimental data for a lab-scale bed module in terms of mass transfer and energy performance on a packed bed using amine-functionalized material. A parametric study on the main operating conditions, i.e., air velocity, air relative moisture, air temperature, and CO2 capture rate, is undertaken to assess the global performance and energy consumption. A method of up-scaling the lab-scale bed module to industrial module is exposed and mass transfer and energy performances of the industrial module are provided. The scale up from lab scale to the industrial size is conservative in terms of thermal energy consumption while the electrical consumption is very sensitive to the bed design. Further study related to the engineering solutions available to reach high global gas velocity are required. This could be offered by monolith-shape adsorbents.

Comment on “How green is blue hydrogen?”

AbstractThis paper is written in response to the paper “How green is blue hydrogen?” by R. W. Howarth and M. Z. Jacobson. It aims at highlighting and discussing the method and assumptions of that paper, and thereby providing a more balanced perspective on blue hydrogen, which is in line with current best available practices and future plant specifications aiming at low CO2 emissions. More specifically, in this paper, we show that: (i) the simplified method that Howarth and Jacobson used to compute the energy balance of blue hydrogen plants leads to significant overestimation of CO2 emissions and natural gas (NG) consumption and (ii) the assumed methane leakage rate is at the high end of the estimated emissions from current NG production in the United States and cannot be considered representative of all‐NG and blue hydrogen value chains globally. By starting from the detailed and rigorously calculated mass and energy balances of two blue hydrogen plants in the literature, we show the impact that methane leakage rate has on the equivalent CO2 emissions of blue hydrogen. On the basis of our analysis, we show that it is possible for blue hydrogen to have significantly lower equivalent CO2 emissions than the direct use of NG, provided that hydrogen production processes and CO2 capture technologies are implemented that ensure a high CO2 capture rate, preferably above 90%, and a low‐emission NG supply chain.

Decarbonization options for cement production process: A techno-economic and environmental evaluation

The long-term environmental targets require significant cuts of CO2 emissions in fossil fuel-intensive industrial processes. Currently, the cement production sector is responsible for approximate 8% of world anthropogenic CO2 emissions. The present paper assesses from the technical, environmental and economic point of view different decarbonization systems integrated into cement production plants. As CO2 capture technologies, the tail-end post-combustion capture using amine-based chemical scrubbing, membrane and calcium looping were assessed as well as the partial and total oxy-combustion options. The size of decarbonized cement concept has a capacity of 1 Mt/y with 90% CO2 capture rate. The overall techno-economic assessment was based on modelling and simulation to assess the key performance indexes. A non-decarbonized cement plant was also assessed for comparison to calculate the energy and economic penalties for decarbonization. The membrane and oxy-combustion concepts have the lowest cement production cost in comparison to the reactive absorption and adsorption concepts (112–119 vs. 125–145 €/t). The full oxy-combustion plant followed by the membrane concept exhibit the lowest CO2 avoided costs comparable with the current emission tax (60–70 vs. 60–80 €/t). The reactive gas–solid system (calcium looping) exhibits superior indicators than the chemical scrubbing system due to high temperature heat recovery.

Thermodynamic modeling and exergy investigation of a hydrogen-based integrated system consisting of SOFC and CO2 capture option

The current study deals with the thermodynamic modeling of an innovative integrated plant based on solid oxide fuel cell (SOFC) with liquefied natural gas (LNG) cold energy supply. For the suggested innovative plant the energy, and exergy simulations are fully extended and the plant comprehensively analyzed. According to mathematical simulations of the proposed plant, a MATLAB code has been extended. The results indicate that under considered initial conditions, the efficiencies of SOFC and net power generation calculated 58% and 78%, respectively and the CO2-capture rate is obtained 79 kg/h. This study clearly shows that the integrated system reached high efficiency while having zero emissions. In addition, the efficiencies and net amount of power generation, cooling or heating output and SOFC power generation are discussed in detail as a function of different variables such utilization factor, air/fuel ratio, or SOFC inlet temperature. For enhancing the power production efficiency of SOFC, the net electricity, and CCHP exergy efficiency the plant should run in higher utilization factor and lower air/fuel ration also it's important to approximately set SOFC temperature to its ideal temperature.

Potential of enhanced weathering of calcite in packed bubble columns with seawater for carbon dioxide removal

Enhanced weathering of minerals is one option being considered for removing CO2 from the atmosphere to help combat climate change. In this work, we consider the weathering of calcite with seawater in a reactor using air enriched with CO2. A mathematical model of the packed bubble column reactor was constructed with the key mass transfer and chemical reaction components validated with experimental data. The modelling results for a continuous process reveal the performance in terms of the specific energy consumption and the CO2 capture rate, which are affected by parameters including particle size, superficial velocities of gas and liquid, reactor bed height and feed CO2 concentration. The major energy requirements are for pumping liquid and compressing gas, and for CO2 enrichment; energy needed for supplying solid particles (mining operations, transport and comminution) was found to be comparatively minor. A trade-off was possible between ground area requirement (determined by CO2 capture rate) and energy requirement. To capture 1 tonne of CO2 at the reactor, optimal designs were predicted to consume 2.1–2.3 GJ of electricity and occupy 1.8–5.2 m2 year of space, depending on the feed CO2 concentration. These would increase to 5.7–8.2 GJ and 7.1–13.1 m2 year per tonne of CO2 captured, after allowing for degassing of the weathering product in the ocean. This increased energy intensity is still within the range of the CO2 removal options previously reported, while the space requirement quantification provides essential information for future feasibility assessment of this scheme.

A Pathway Towards Net-Zero Emissions in Oil Refineries

Rapid industrialization and urbanization have increased the demand for both energy and mobility services across the globe, with accompanying increases in greenhouse gas emissions. This short paper analyzes strategic measures for the abatement of CO2 emissions from oil refinery operations. A case study involving a large conversion refinery shows that the use of post-combustion carbon capture and storage (CCS) may only be practical for large combined emission point sources, leaving about 30% of site-wide emissions unaddressed. A combination of post-combustion CCS with a CO2 capture rate well above 90% and other mitigation measures such as fuel substitution and emission offsets is needed to transition towards carbon-neutral refinery operations. All of these technologies must be configured to minimize environmental burden shifting and scope 2 emissions, whilst doing so cost-effectively to improve energy access and affordability. In the long run, scope 3 emissions from the combustion of refinery products and flaring must also be addressed. The use of synthetic fuels and alternative feedstocks such as liquefied plastic waste, instead of crude oil, could present a growth opportunity in a circular carbon economy.

Investigation of molten carbonate electrolysis cells performance for H2 production and CO2 capture

Molten carbonate electrolysis cells have recently gained interest for the sustainable production of H2 or syngas to substitute fossil fuels. However, they can be also used for CO2 sequestration, as they pump it from one electrode inlet to the opposite electrode outlet. Thus, they can easily be applied to segregation of CO2 from H2 based fuels while also increasing the fuel heat of combustion for example after a steam reforming reactor.To explore the use of molten carbonate electrolysis cell for this application, in this work the authors investigate the performance of the cell under different operating conditions in term of both operating temperature and fuel electrode gas composition. Polarization curves, gas crossover and electrochemical impedance spectroscopy are used to evaluate specific issues (high electrolyte losses due to water and temperature) or benefits (excess of H2O in regard to CO2 that allows for higher CO2 capture rate). After, a series of long-term tests at −150 mA cm−2 and 650 °C are performed to demonstrate long term stability. In particular, before electrolyte loss made the performance unstable, different cells are operated for about 1000 h with an average voltage of about 1.14 V demonstrating also the repeatability of such tests.