Amine-based Process Research Articles

Techno-economic analysis of blue ammonia synthesis using cryogenic CO2 capture Process-A Danish case investigation

Ammonia is a vital chemical with numerous applications. Currently, the primary methods for generating the necessary reactants for ammonia production involve steam methane reforming (SMR) and cryogenic air separation unit (CASU), while the Haber-Bosch process converts these reactants into ammonia. However, the SMR process releases substantial amounts of CO2, making it imperative to employ an efficient and cost-effective CO2 capture technology to mitigate emissions. This investigation focuses on evaluating the cryogenic CO2 capture (CCC) process for blue ammonia production and provides a thorough economic analysis, estimating both the initial investment costs and operational expenses involved in producing blue ammonia. The results indicated that the CCC process can capture 90% of the CO2 content in the flue gas emitted by the SMR, incurring an energy penalty of 0.724 MJe/kgCO2 while capturing CO2 in the liquid phase with purities exceeding 99.9%. In this case, the estimated CO2 capture costs would be 18.05, 45.1, and 16.65 USD/ton in 2021, 2022, and 2023, respectively. This represents a 40% reduction compared to the CO2 capture costs associated with conventional amine-based technology. The results of this study indicate that the annual electricity costs for ammonia production increase by 38.5% and 64.2% when employing the CCC and amine-based processes, respectively. This investigation employed an isothermal reactor for ammonia synthesis, using the heat from the exothermic reaction in a water ammonia absorption refrigeration cycle (ARC) to condense and purify ammonia. The results show that the ARC system can effectively condense ammonia at −6 °C, producing a liquid ammonia stream with 99.3% purity. This leads to a 95% reduction in power consumption compared to a vapor compression refrigeration cycle (VCRC). Consequently, this method has the potential to decrease the annual operational costs for ammonia production by 2.92%, 2.69%, and 3.13% in 2021, 2022, and 2023, respectively. This study indicated that the hydrogen production unit incurs the highest initial investment costs, as well as operating costs, in the blue ammonia production process, followed by CASU and the Haber-Bosch process.

Evaluating the thermodynamic potential for carbon capture from internal combustion engines

This work explores the potential for use of carbon dioxide separation processes, colloquially known as carbon capture, to accelerate decarbonization of the transport sector. Thermal swing absorption processes using an aqueous, CO2-selective solvent, provide an efficient means of separating CO2 from other exhaust gas constituents. Amine-based solvents–well known from acid gas treating and other post-combustion carbon capture processes–are highly selective, have a fast rate of reaction with CO2, and can use waste heat to drive the separation process. This work demonstrates how amine-based processes can be deployed for carbon removal from a generic exhaust gas source produced by an internal combustion engine (ICE) using waste heat in the exhaust. It includes an estimation of the exhaust enthalpy-limited capture rate for various sources considering the capture system performance, the CO2 concentration, and the exhaust temperature.CO2 capture rates of around 25–80% are shown to be thermodynamically feasible for various ICE applications using waste exhaust heat for solvent regeneration. Rates of around 15–50% are attainable without providing additional energy, if exhaust heat is also used to power the capture system pump and compressor. Although a higher exhaust CO2 concentration reduces the specific energy requirements of the separation process, the total energy required for a given capture rate increases due to the greater amount of CO2 removed. Thus, maximum capture rates are highest for applications with high exhaust temperature and low CO2 concentration (such as diesel generators), and lowest for applications with very low exhaust temperature such as ships. This analysis also shows that the potential for CO2 avoidance using carbon capture systems far exceeds that of organic rankine cycle waste heat recovery systems. Overall, expanding the use of carbon capture to ICE applications can provide an efficient means of utilizing waste exhaust heat while providing significant reductions in the energy industry's scope 3 greenhouse gas emissions.

Adsorption Assisted Cryogenic Carbon Capture: an Alternate Path to Steam Driven Technologies to Decrease Cost and Carbon Footprint

Carbon capture has gained momentum in addressing CO2 emissions where substitution of carbon feedstock by renewables is very challenging, such as in steel, refining, chemical, and cement industries. Gas streams containing 15% to 50% CO2 are low-hanging fruits for applying CO2 capture due to their prevalence in industry and lower capture cost linked to their high concentrations. Amine-based processes are historally considered as reference solutions for these applications, but they are no longer the only commercially viable solution today. Air Liquide has been working on a smart combination of its proprietary Adsorption and Cryogenic technologies, where Pressure Swing Adsorption (PSA) is used as a CO2 preconcentration and Cryogenic as CO2 purifiers: the Cryocap™ FG. This paper studies the influence of utilities (steam and electricity) on the carbon footprint and total cost of ownership of both amine and Cryocap™ FG technologies. The paper also studies Scope 1, 2, and 3 emissions and the TCO per ton of reduced CO2 for various footprint scenarios and typical utility costs. As it is a high efficiency power-driven technology, Cryocap™ FG resulted in a 90% reduction of Scope 1 emissions compared to 69-74% reduction with amine, depending on steam footprint, where limited waste heat is available for steam production. Cryocap™ FG was also found to be the most economical choice for electricity prices below 60€/MWh at any steam price, and the breakeven is at 120 €/MWh for a steam cost at around 10 €/t.

Investigation into an energy-saving mechanism for advanced stripper configurations in post-combustion carbon capture

Abstract In a standard post-combustion carbon capture (PCC) process, the regeneration energy of CO2 lean solvent constitutes the majority of overall energy consumption. The energy reduction achieved by advanced stripper configurations, such as the cold-split bypass (CSB), interheated (IH) stripper, and lean vapor compression (LVC), have been reported in relevant literature. Energy-saving performance may be enhanced by combining the different modifications. In this study, the energy-saving mechanism for advanced stripper configurations was investigated using a standard amine-based process, in which 30 wt% monoethanolamine (MEA) aqueous solution was applied. Contrary to the literature reviewed, the energy-saving performance attained by combining the different modifications was limited. This was due to the major contribution of energy reduction in the various modifications sharing the similar mechanism. In addition, this study demonstrated that the overall energy required, as needed by the heat recovery in the cross-flow heat exchanger (HX) and the reboiler duty, is dominated by overhead vapor generation. Reducing the amount of vapor generated may effectively relieve the overall energy burden. Thus, when energy reduction is reliant on a HX with a poor heat recovery system, the energy-saving purpose is not fulfilled. Therefore, a successful energy-saving design may significantly reduce the amount of vapor generated, whilst maintaining a reliable heat recovery.

Energy harvesting from amine-based CO2 capture: proof-of-concept based on mono-ethanolamine

Amine-based processes are the leading technology for CO2 capture, but their commercial deployment is hindered by their large energy requirement. In practice, the energy consumption of this CO2 capture process is a result of an inability to offset the energy required for CO2 desorption against the enthalpy released in CO2 absorption. Here, we propose a metal-mediated CO2-regenerative amine-based battery (CRAB) to directly convert the CO2-reaction enthalpy into electrical energy. Using the benchmark mono-ethanolamine (MEA) absorbent, we developed and validated a CRAB process model that is used to predict the energy harvesting performance. We then harvested an electrical energy of 8.3 kJe/mol CO2 from the lab-scale flow battery, demonstrating the proof-of-concept of energy harvesting from amine-based CO2 capture. Techno-economic analysis indicates that the CRAB energy harvesting system improved the power generation efficiency by 1.75% and decreased the CO2 avoided cost when integrated with a coal-fired power station, suggesting its potential to improve the techno-economic competitiveness of amine-based CO2 capture process.

Role of absorber and desorber units and operational conditions for N-nitrosamine formation during amine-based carbon capture

The formation of carcinogenic N-nitrosamines from reactions between solvent amines and flue gas NOx is an important concern for the application of amine-based processes to capture CO2 post-combustion. Using an advanced test rig with interconnected absorber and desorber units, we evaluated the importance for N-nitrosamine formation of the desorber relative to the absorber, and any synergism between the two units. Variations in desorber temperature and in flue gas composition indicated that N-nitrosamine formation from fresh monoethanolamine (MEA) occurred predominantly in the absorber. N-nitrosamine formation was driven by high NO2 and O2 flue gas concentrations, although NO also contributed. In contrast, N-nitrosamine formation from piperazine (PZ) was driven by reactions with nitrite in the heated desorber, and accelerated concurrent with nitrite accumulation. A complementary experiment simulating aged MEA solvent (high nitrite, 1.5% sarcosine as a proxy of secondary amine degradation products) suggested the desorber becomes an order of magnitude more important than the absorber for N-nitrosamine formation. For fresh MEA solvent, increasing the desorber temperature from 110 °C to 130 °C promoted thermal decomposition of N-nitrosamines, reducing N-nitrosamine accumulation rates two-fold. Compared to the test rig, the prevailing practice of using separate absorber columns and autoclave-like treatments to mimic desorber units predicted the direction, but underestimated the magnitude of N-nitrosamine formation. Because N-nitrosamine accumulation rates are the net result of competing formation and thermal decomposition processes, use of continuously cycling test rigs may be necessary to understand the impacts of different operating conditions.

Rational design of a porous gel encapsulated bio-hybrid solvent for accelerated CO2 capture and low energy stripping

The removal of CO2 has become an essential step in many industrial processes including flue gas separation, natural gas, and biogas purification in view of environmental concern. The most commonly used process for CO2 capture is by amine solvents. The amine-based process has inherent limitations such as oxidative or thermal degradation of solvent and energy-intensive solvent regeneration. In the present study, a polymeric porous gel (PPG) was developed using polyvinyl alcohol (PVA) and agarose (AG). This gel showed very high activity for CO2 capture when modified with a sterically hindered amine ‘2-amino-2-methyl-1-propanol’ (AMP) and a thermo-stable enzyme ‘carbonic anhydrase’ (CA) (AMP + CA hereafter designated as bio-hybrid solvent). PPG shows a high porosity of 86% and efficiently encapsulated the bio-hybrid solvent (HS). The resulting material (PPG/HS) shows CO2 uptake of 9.3 wt% and stripping at relatively low temperature. This gel has further ability to regain its porosity once reached to room temperature. Moreover, the oxidative degradation studies confirmed that PPG can significantly enhance the stability of encapsulated amines.

Mechanism Investigation of Advanced Metal-Ion-Mediated Amine Regeneration: A Novel Pathway to Reducing CO2 Reaction Enthalpy in Amine-Based CO2 Capture.

The high energy consumption of CO2 and absorbent regeneration is one of the most critical challenges facing commercial application of amine-based postcombustion CO2 capture. Here, we report a novel approach of metal-ion-mediated amine regeneration (MMAR) to advance the process of amine regeneration. MMAR uses the dual ability of amine to reversibly react with CO2 and reversibly complex with metal ions to reduce the enthalpy of the CO2 reaction, thus decrease the overall heat requirement for amine regeneration. To elucidate the mechanistic effects behind MMAR's ability to reduce CO2 reaction enthalpy, we developed a comprehensive chemical model describing the chemistry of Me(II)-monoethanolamine(MEA)-CO2-H2O system. The model was then validated using experimentally determined CO2 partial pressures via vapor-liquid equilibrium (VLE) measurements. We used the validated chemical model to gain insight into VLE behavior and solution chemistry, and to identify the specific changes in CO2 reaction enthalpy with and without metal ions. Two metals and five amines were evaluated in detail, which revealed that metal-ions with high complexation enthalpy and amines with large carbamate stability constant are preferred in MMAR, owing to their large reduction in reaction enthalpy and regeneration duty. We anticipate that MMAR could provide an alternative pathway to reducing the energy consumption of absorbent regeneration, ultimately making amine-based processes more technically and economically viable.

Surfactants Facilitating Carbonic Anhydrase Enzyme-Mediated CO2 Absorption into a Carbonate Solution.

Carbonic anhydrase (CA) enzyme-mediated absorption processes are regarded as promising alternatives to the conventional amine-based process for CO2 capture because of their low energy penalty and low risk of causing secondary pollution. The activity and stability of the CA enzyme are crucial to reducing the equipment and operating costs of the enzyme-mediated process. This work investigated three cationic and nonionic surfactants to improve the activity and stability of a technical-grade CA enzyme in a 20 wt % potassium carbonate solution. Experimental results revealed that the impact of the surfactants on the CA enzyme depended on their properties. For example, the cationic surfactant significantly enhanced the activity of CA enzyme but adversely affected enzyme stability. However, in the presence of the cationic surfactant after 30 days at 50 °C, the activity of the CA enzyme still outperformed that of CA without added surfactant. The nonionic surfactant significantly improved enzyme stability. Furthermore, the addition of surfactants within a critical micelle concentration of 1.0 did not distinctly influence the gas-liquid mass transfer, indicating that surfactant-enzyme interaction was responsible for the observed variations in the activity and stability of the tested enzyme.

Self-Assembled Enzyme Nanoparticles for Carbon Dioxide Capture.

Enzyme-based processes have shown promise as a sustainable alternative to amine-based processes for carbon dioxide capture. In this work, we have engineered carbonic anhydrase nanoparticles that retain 98% of hydratase activity in comparison to their free counterparts. Carbonic anhydrase was fused with a self-assembling peptide that facilitates the noncovalent assembly of the particle and together were recombinantly expressed from a single gene construct in Escherichia coli. The purified enzymes, when subjected to a reduced pH, form 50-200 nm nanoparticles. The CO2 capture capability of enzyme nanoparticles was demonstrated at ambient (22 ± 2 °C) and higher (50 °C) temperatures, under which the nanoparticles maintain their assembled state. The carrier-free enzymatic nanoparticles demonstrated here offer a new approach to stabilize and reuse enzymes in a simple and cost-effective manner.

Life cycle assessment of CaO looping versus amine-based absorption for capturing CO2 in a subcritical coal power plant

Cradle-to-gate life cycle assessment was used to compare the environmental impact of capturing CO2 from the flue gases in a subcritical coal power plant by using three technologies, namely, absorption with two types of amine processes (Econamine and Econamine FG+) and CaO looping. The results were benchmarked against the same power plant with no capture unit. The intended application of the study is to evaluate whether CaO looping can be an alternative to conventional chemical absorption by amine-based processes for capturing CO2. The inclusion of the CO2 capture unit showed a net reduction only in those impact categories directly associated with the reduction of CO2 as flue gas emissions, i.e. climate change, particulate matter and terrestrial acidification. Emissions for the Climate Change category were 0.33, 0.27 and 0.26kgCO2-eq/kWh for the two amine based systems (Econamine and Econamine FG+, respectively) and the CaO looping capture unit, thereby reducing the emissions of the same plant without a capture unit (0.96kgCO2-eq/kWh). Consequently, with the assumptions and system boundaries defined in this study, the CaO looping is a viable alternative to amine-based systems from the environmental point of view. However, taking into account that CaO looping is a process still under development, additional research and process scale-up is necessary to confirm this result.

A Simulation of a Claus Tail Gas Treatment Unit in a Petroleum Refinery

More treatment is needed for sulfur recovery unit tail gas, due to its high pollution. In this research, an Iranian petroleum refinery was selected as a case study. In the proposed refinery, incineration is used for treatment of tail gas. As incineration is not an environment-friendly process, an amine-based process has been selected as the best method for treatment of tail gas. The selected process was simulated with HYSYS and Aspen-Plus software. Different parameters and their changes were investigated through the simulation and optimum conditions were achieved. Also, comparison of results of two simulation softwares was done.

Analysis of a precipitating solvent absorption process for reducing CO2 emissions from black coal fired power generation

Carbon capture and storage (CCS) is a technology that has the potential to provide deep cuts in CO2 emissions from coal-fired power generation. This paper describes retrofitting the CO2CRC's low cost “UNO MK 3” precipitating potassium carbonate (K2CO3) process to a 335MW (net) black coal-fired subcritical power station, typical of those in Australia.The use of heat integration to reduce the net energy penalty of retrofitting CO2 capture is also studied and the modifications required to the steam cycle for these cases are outlined. Retrofitting the UNO MK 3 process has a smaller energy penalty compared with amine-based processes. Heat integration strategies can reduce this energy penalty by an additional 20%.To further reduce the impact of CO2 capture on the net output of the power station, the option of partial capture of CO2 is also described here. In the partial capture case, the CO2 emissions intensity of the coal-fired power station is equivalent to that of a natural gas combined cycle (NGCC) power station.A detailed cost analysis of various cases of CO2 capture with and without heat integration is also performed. The results suggest that compared to standard amine-based solvent technologies, the UNO MK 3 process can provide up to 50% cost savings in the cost of CO2 avoided. The levelised cost of electricity also reduces by up to 35% using UNO MK 3 compared to commercial amine-based solvent technologies.

Application of the Taguchi Method for the Optimization of an Amine-based Tail Gas Treating Unit in Petroleum Refineries

Taguchi experimental design method was used as a process optimization tool for an amine-based process. Quench temperature, quench flow, absorber pressure, absorber packing, amine flow, amine temperature, and H2S concentration in lean amine were the processed factors through Taguchi method. Three different orthogonal arrays (L16, L18, and L9) were employed for optimization. The designated experiments were simulated by Aspen-Plus software. It was found that absorber pressure, amine temperature, and H2S concentration in lean amine were the most important factors. The optimum value for these parameters was 6 atm, 40°C, and 1,000 ppm, respectively.

Update on Mixed-salt Technology Development for CO2 Capture from Post-combustion Power Stations

The new mixed-salt technology combines the well-known ammonia and potassium carbonate technologies with improved reaction kinetics and reduced emissions. This technology is capable of capturing CO2 at high cyclic loadings compared to amine-based processes. In addition, mixed-salt technology can strip CO2 at high pressure, reducing the CO2 compression costs, requires no solvent chilling as in aqueous ammonia based processes, and has a low reboiler duty for regeneration (< 1000 Btu/lb.). Mixed-salt technology provides unique opportunities for better energy management to reduce the burden on the power plant steam cycle and is suitable for capturing CO2 from post-combustion, pre-combustion and other industrial gas streams. The mixed-salt technology has already been tested successfully in two small bench-level systems and is currently being tested at a large bench-scale pilot level with the funding from the U.S. Department of Energy (DOE). The technology can easily be scaled up with use of conventional process equipment and can be demonstrated in full scale sooner than second-generation technologies that are currently in development.

Pilot-scale Demonstration of an Advanced Aqueous Amine-based Post-combustion Capture Technology for CO2 Capture from Power Plant Flue Gases

Abstract Post-combustion CO 2 capture (PCC) technology offers flexibility to treat the flue gas from both existing and new coal-fired power plants and can be applied to treat all or a portion of the flue gas. Solvent-based technologies are today the leading option for PCC from large coal-fired power plants as they have been applied in large-scale in other applications. Linde and BASF are working together to further improve a post-combustion capture technology incorporating BASF's novel aqueous amine-based process based on the results of the joint development of BASF, Linde and RWE at the PCC pilot plant in Niederaussem, Germany. This technology offers significant benefits compared to other solvent-based processes as it aims to reduce the regeneration energy requirements using novel solvents that are very stable under the coal-fired power plant feed gas conditions. BASF has developed the desired solvent based on the evaluation of a large number of candidates and long-term small pilot-scale testing has been performed on a lignite-fired flue gas. Linde has evaluated a number of options for capital cost reduction in large engineered systems for solvent-based PCC technology. Pilot-scale demonstration on a coal-fired power plant flue gas at a 1-1.5 MW e scale is currently planned under a project supported by DOE (project award DE-FE0007453). Mechanical completion of the pilot plant was achieved in July 2014 and the final commissioning activities are being completed to enable start-up of operations in late 2014. The pilot plant incorporates the capability to test a number of unique features of the Linde-BASF technology aimed at lowering the overall energy consumption as well as resulting in capital cost reduction. In this presentation, the details of the fabrication, construction and start-up of the pilot plant will be discussed. The pilot plant incorporates significant instrumentation and control features to enable automated and stable operation, and the ability to reliably check and verify mass and energy balance closures with adequate redundancies. Detailed plans for the parametric and long-term testing will be discussed; these tests are aimed at validating the technology performance against targets set based on a preliminary techno-economic assessment, and, the stability of the solvent with continued operation over an extended period.

Pilot Plant Results with Piperazine

Concentrated (40wt %) piperazine (PZ) with two-stage flash regeneration is an advanced second generation amine-based process for CO2 capture. Two pilot campaigns with the two-stage flash process were completed in 2011 and successfully demonstrated high temperature stripping at 150°C with concentrated piperazine. Data reconciliation for the absorber with intercooling return spray was completed using Aspen Plus® Data-Fit. Data reconciliation for the two-stage flash with warm rich bypass was completed using Aspen Plus® Data-Fit and a dynamic model developed in MATLAB®. The results of data reconciliation analysis found that the CO2 loading in the lean and rich streams needed to be systematically shifted upward, 4.6–4.7% in the stripper analysis and 7.5% in the absorber analysis.An analysis of the October 2011 campaign pilot plant data identified the two configurations with the lowest equivalent work as the high temperature two-stage flash with warm rich bypass and low pressure simple stripper. The calculated equivalent work for the two-stage flash with warm rich bypass from raw pilot plant data and reconciled pilot plant data is approximately 35kJ/mol CO2 and 36.6kJ/mol CO2, respectively. Intercooling with a spray return improved absorber CO2 removal performance by 6–7% at the lower gas rates and was found to be equivalent to a 7– 20% increase in packing height based on reconciled data results. Warm rich bypass to the low pressure flash tank reduced piperazine volatility by factor of two in the condensate. In addition, analysis of the pilot plant piperazine inventory at the end of the campaign identified the following degradation products (mmol/kg): N-formyl PZ (1.3), ethylenediamine (13), aminoethylpiperazine (3.6), Hydroxyethylpiperazine (3.9), formate (1.0), and N-nitroso- piperazine (0.09). The solvent analysis also found that the CO2 capacity has decreased by 17%, with a slight decrease in CO2 absorption rate and heat of vaporization.

The Effects of Membrane-based CO2 Capture System on Pulverized Coal Power Plant Performance and Cost

Membrane systems are under development for cost-effective carbon dioxide (CO2) capture. This study is to investigate the effects of adding CO2-selective polymeric membrane systems to coal-fired power plants using newly developed performance and cost models. Sensitivity analysis is further carried out to explore the influences of key parameters and factors on the power plant and the membrane-based capture system. The results show that adding a two-stage membrane system for 90% CO2 capture to a coal-fired power plant nearly doubles the plant cost of electricity and incurs a high energy penalty up to about 30% of the gross electrical output; using both compressors and vacuum pumps to produce driving force for membrane gas separation is effective with reducing the capture cost; and recycling a portion of CO2 via a multi-stage/step membrane configuration with air sweep would significantly reduce the overall system energy penalty and the cost of CO2 avoided by roughly one-third in comparison with the two-stage membrane system, which exhibits that membrane capture systems could be a viable alternative to current amine-based processes.

Phase Behavior of Liquid Crystals with CO2

Liquid crystals are being considered as novel process solvents for CO(2) capture. The solubility of CO(2) is higher in the isotropic phase than in the structured (e.g., nematic) phase. CO(2) can be captured in the isotropic phase, and regeneration of the solvent is achieved by cooling down the mixture a few degrees until a phase transition to the structured phase occurs. This CO(2) capture process has the potential to consume less energy than the conventional amine-based processes. To address the potential of liquid crystals to efficiently capture CO(2), experimentally obtained P,T-phase diagrams of five liquid crystals with 5 mass % CO(2) are reported. The liquid crystals used in this study are 4'-(pentyloxy)-4-biphenylcarbonitrile, 4'-pentyl-4-biphenylcarbonitrile, 4-ethyl-4'-propyl-bicyclohexyl, 4-propyl-4'-butyl-bicyclohexyl, and 4'-(octyloxy)-4-biphenylcarbonitrile. It is found that a weakly polar liquid crystal had a higher CO(2) solubility than apolar and more polar liquid crystals.

Activation Strategies for Calcium-Based Sorbents for CO2 Capture: A Perspective

The chemical looping process (CLP) using calcium-based sorbents to capture CO2 through cyclic carbonation–calcination reaction (CCR) before, during, or after the conversion of carbonaceous fuel occurs, is a viable CO2 control technology. With extensive past and current research efforts, the basic process concept has been found to be attractive at larger scales. Additionally, process simulations based on experimental results indicate that the parasitic energy consumption for this high temperature process is relatively low compared to low temperature processes such as the amine-based process. The ability of the calcium-based sorbents to maintain stable reactivity and physical integrity in cyclic reaction under severe operating conditions is one of the most important criteria for the success of the calcium looping technology. Despite being abundant and cheap, calcium-based sorbents derived from naturally occurring precursors, such as limestone and dolomite, suffer from rapid reactivity deterioration after hi...