Energy Demand For Regeneration Research Articles

Adsorption-based post-combustion carbon capture assisted by synergetic heating and cooling

Adsorption carbon capture has shown its superiority in energy consumption and cost investment when compared with common amine scrubbing technologies. However, high regeneration energy demand of adsorbents is still a challenge for large-scale application. This paper proposes a temperature vacuum swing adsorption system integrated with auxiliary heating and cooling technology. Absorption chiller and double-stage absorption heat transformer (DAHT) are introduced from the perspective of adsorption and desorption process of CO2 capture system. Results indicate that when the duration of each step increases from 25 min to 45 min, the CO2 recovery rate decreases from almost 100 %–75.7 %, and CO2 purity increases slightly from 89.6 % to 91.1 %. Considering the temperature grade of waste heat, heat consumption of the absorption chiller assisted system is lower than that of DAHT for original and adjusted cases at a generation temperature of 58 °C. If the desorption temperature decreases from 120 °C to 100 °C, heat consumption of the absorption chiller decreases from 1.90 GJ·ton−1 to 1.76 GJ·ton−1, but the average capture capacity decreases from 306.3 ton·ton−1ad to 272.1 ton·ton−1ad. It is demonstrated that both absorption chiller and absorption heat transformer could be promising solutions to reducing the energy consumption of CO2 capture system. Absorption chiller has a priority over DAHT in regions with low temperature heat sources. Moreover, a tradeoff between adsorbent loss and heat consumption should be found when choosing the appropriate heat pump for practical application.

Amine Chemistry of Porous CO2 Adsorbents.

ConspectusAs renewable energy and CO2 utilization technologies progress to make a more significant contribution to global emissions reduction, carbon capture remains a critical component of the mission. Current CO2 capture technologies involve operations at point sources such as fossil fuel-based power plants or source-agnostic like in direct air capture. Each strategy has its own advantages and limitations, but in common, they all employ sorption-based methods with the use of sorbents strongly adhering to CO2. Amine solutions are the most widely used absorbents for industrial operations due to the robust chemical bonds formed between amines and CO2 under both dry and humid conditions, rendering excellent selectivity. Such strong binding, however, causes problematic regeneration. In contrast, purely physisorptive porous materials with high surface areas allow for the confinement of CO2 inside narrow pores/channels and have a lower regeneration energy demand but with decreased selectivity and capacity. The most promising solution would then be the unification of both types of sorbents in one system, which could bring about a practical adsorption-desorption process. In other words, the development of porous solid materials with tunable amine content is necessary to leverage the high contact surface of porous sorbents with the added ability to manipulate amine incorporation toward lower CO2 binding strength.To answer the call to uncover the most feasible amine chemistry in carbon capture, our group has devoted intense effort to the study of amine-based CO2 adsorbents for the past decade. Oriented along practicality, we put forth a principle for the design of our materials to be produced in no more than three synthetic steps with economically viable starting materials. Porous organic polymers with amine functionalities of various substitutions, meaning primary, secondary, and tertiary amines, were synthesized and studied for CO2 adsorption. Direct synthesis proved to be feasibly applicable for secondary and tertiary amine-incorporated porous polymers whereas primary-amine-based sorbents would be conveniently obtained via postsynthetic modifications. Sorbents based on tertiary amines exhibit purely physical adsorption behavior if the nitrogen atoms are placed adjacent to aromatic cores due to the conjugation effect that reduces the electron density of the amine. However, when such conjugation is inhibited, chemisorptive activity is observed. Secondary amine adsorbents, in turn, express a higher binding strength than tertiary amine counterparts, but both types can merit a strengthened binding by the physical impregnation of small-molecule amines. Sorbents with primary-amine tethers can be obtained via postsynthetic transformation of precursor functionalities, and for them, chemical adsorption is mainly at work. We conclude that mixed-amine systems could exhibit unprecedented binding mechanisms, resulting in exceptionally specific interactions that would be useful for the development of highly selective sorbents for CO2.

Enhanced CO2 absorption and reduced regeneration energy consumption using modified magnetic NPs

This study aimed to investigate the ability of nanofluids in improving CO2 absorption and reducing regeneration energy demand in a bubble column reactor in the presence of functionalized-magnetic NPs. The first step was to synthesize Fe3O4 nanoparticles (NPs), which were then functionalized with Aspartic-acid and Lysine. Next, to study CO2 absorption and stripping performances, the NPs with different concentrations were dispersed in an aqueous methyl diethanol amine (MDEA) solution (10 wt%). The investigation of CO2 absorption performance, CO2 loading and pH of all nanofluids were reported at different times of absorption experiments. The obtained results indicated that Fe3O4@Aspartic (Fe3O4@Asp) and Fe3O4@Lysine (Fe3O4@Lys) NPs improved CO2 loading up to 15.3% and 21.4%, respectively, as compared to Fe3O4 NPs. In addition, the functionalized-magnetic NPs showed more positive effects on CO2 desorption compared to bare Fe3O4. To show regeneration efficiency, the outlet gas flow rate and its CO2 concentration were measured and the CO2 loading and pH were determined at the end of the desorption experiment. The results revealed that at 70 °C, the CO2 loading was reduced by 58.9% and 55.1% applying Fe3O4@Lys and Fe3O4@Asp, respectively. Therefore, more energy could be saved in desorption process using functionalized magnetic NPs.

Influence of design and operating parameters for additively manufactured intensified packing devices on CO2-Absorption column cooling and capture efficiency

Solvent-based CO2 absorption is technologically a matured CO2 capture pathway but suffers from: high regeneration energy demand, and solvent temperature rise and decreased capture efficiency caused by the heat of reaction. While research has focused on developing non-aqueous and low-aqueous solvents for decreasing the regeneration energy, the temperature bulge due to exothermic absorption is typically dealt with by cooling the solvent with an external inter-stage heat-exchanger. This approach may increase the overall process footprint, as well as capital and operating costs. The current study explores a process intensification approach by incorporating inside the column an additively manufactured intensified packing device that consists of corrugated plates and internal coolant channels. The corrugated plates provide surface area for mass transfer between gas and liquid, while cooling fluid inside the internal channels removes heat from the exothermic reactive system. Two different intensified devices with specific surface areas of 266 m2/m3 and 359 m2/m3 were designed, manufactured, and tested inside a 2.06-m long and 0.203-m diameter column packed with commercial Mellapak 250Y packing. The device with a lower surface area showed up to 27 % reduction in cooling performance. A steady-state heat transfer model provides good agreement with the experimental column temperature and intra-stage heat removal data. Although a decrease in heat transfer performance was observed for the device with lower surface area, CO2 capture experiments performed with simulated flue gas and low-aqueous solvent demonstrated that both intensified devices lead to a similar improvement of 12 % in capture efficiency. This study provides an understanding on simplifying the intensified packing device geometry and decreasing the device fabrication cost by 25 % without compromising with the CO2 absorption performance of the packed column.

Review of recent trends and various techniques for CO2 capture: Special emphasis on biphasic amine solvents

In the present scenario, the hazardous impacts of greenhouse gases can be restricted by adopting carbon capture and storage (CCS) technology that captures most of the CO2 emitted by numerous industries, human activities, and mostly from thermal power plants. This paper reviewed the main CO2 capturing technologies, i.e., pre-combustion, post-combustion, and oxy-combustion, along with their different operating conditions, performances, and comparisons. Some industrial processes used to capture CO2 by physical solvents are presented with their properties and working conditions. Methodologies like absorption, adsorption, membrane technology, cryogenic separation, and microalgae process are presented. Single alkanolamine-based solvents have limited CO2 loading and high regeneration energy demand, attracting researchers to work on their various amine blends. In today’s scenario, biphasic solvents play a vital role in the field of CO2 capture. Some amine solvent blends show biphasic behavior, leading to faster reaction, higher absorption capacity, and lower regeneration energy. The solvent screening for the biphasic solvent is very rigorous and still challenging. In this work, various blends selected by the researchers with the potential for phase-splitting behavior are reviewed, and the best among them is reported.

Defining Targets for Adsorbent Material Performance to Enable Viable BECCS Processes.

Target properties of CO2 capture adsorbents that would ensure economic viability of bioenergy with carbon capture and storage (BECCS) are defined. The key role of sorbent lifetime in the process cost is demonstrated, and an optimal heat of adsorption for BECCS is postulated through a balance of adsorbent–adsorbate affinity and regeneration energy demand. Using an exponential decay model of sorbent capacity increases the process cost and results in an optimum sorbent lifetime. To ensure a levelized cost of carbon below $100/tonne-CO2, adsorbents should be designed to have working capacities above 0.75 mol/kg, lifetimes over 2 years, heats of adsorption of approximately −40 kJ/mol, and exponential degradation decay constants below 5 × 10–6 cycle–1 (equivalent to a half-life of 1.3 years). Our model predicts a BECCS process cost of $65/t-CO2 can be achieved with a degradation-resistant adsorbent, $40/kg sorbent cost, 2.0 mol/kg working capacity, −40 kJ/mol heat of adsorption, and at least a 2 year lifetime.

Analysis of flexible operation of CO2 capture plants: Predicting solvent emissions from conventional and advanced amine systems

In our previous work, we reported results on solvent management, emissions, and dynamic behavior from an 18-month testing campaign with monoethanolamine (MEA) at the PCC pilot plant at Niederaussem. In this study, we extended our work to include the CESAR1 solvent, a blend of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) in water, as part of our efforts in the ALING-CCUS project to evaluate if CESAR1 could be established as a new benchmark solvent for post-combustion capture. From our long-term (>12,275 h) testing experience, CESAR1 has shown a substantial promise in terms of lower specific solvent regeneration energy demand and stability to degradation in comparison with MEA. However, during a comprehensive series of parametric tests with the CESAR1 solvent, it was observed that amine emissions are significantly higher, especially under transient operation (AMP: 30 – 100 mg/m3 (STP); PZ: 2 – 30 mg/m3 (STP); MEA: <8 mg/m3 (STP)). This work presents step response functions for predicting the time delay and gain in emissions for each parametric/dynamic test performed. Some dynamic tests show a fast response and high emission values and, therefore, can be used to reduce emissions during flexible plant operation. These control actions are mainly the lean solvent and/or water wash temperature increase and are similar to those observed in the MEA campaign. Our testing campaign helps in advancing the fundamental understanding of emissions, establishing optimal mitigation strategies, and providing important insights for future development of models regarding solvent emissions and degradation.

FAU zeolite membranes for dewatering of amine‐based post‐combustion CO2 capture solutions

AbstractIn amine‐based CO2 capture processes, aqueous amine solvent is circulated between absorber (CO2 absorption) and stripping (solvent regeneration) columns. To reduce solvent regeneration energy demand, a selective membrane can dewater and enrich the CO2 concentration in solution prior to the stripper, lowering steam requirements for solution heating. In this work, a facile synthesis strategy was developed to prepare faujasite (FAU) zeolite membranes built upon polydopamine (PDA) modified α‐Al2O3 substrates. PDA facilitated the attachment of zeolite phases onto the substrate surface to form a 3 μm membrane layer. Membrane permeation flux of 4.45 kg m−2 h−1 and 95% rejection rate calculated by either CO2 loading or total alkalinity was achieved in dewatering of CO2 loaded 30 wt% monoethanolamine (MEA) solution. The effects of temperature on membrane dewatering performance and stability were investigated. This study highlights the potential for process integration of membrane technology in amine‐based post‐combustion CO2 capture operations.

A Framework for the Experimental Characterisation of Novel Solvents in a Pilot-plant Scale CO2 Capture Process under Industrial Conditions Using a Data-driven Modelling Approach

In order to improve the performance of a carbon capture process, novel solvents are being developed and uniquely adapted to different applications. The process performance is highly dependent on the choice of the solvent, given by a major share of the energy demand for regeneration. In addition, plant design and operation conditions both affect the process performance, thus energy efficiency and have to be investigated before designing a large-scale plant and optimally operating it. In this contribution, a framework is presented for the systematic characterisation of novel solvents in an industrial pilot-plant using a data-driven modelling approach, which takes into account plant characteristics and industrial operation conditions. The framework is designed to determine optimal operation conditions regarding maximum energy efficiency with reduced number of experiments due to the fact experimental absorbent screening is time-consuming and costly. The proposed three-step framework is based on the assumption that for a novel solvent little to no thermodynamic knowledge is available. Therefore, Monoethanolamine (MEA) is taken as a baseline for the general performance of amine-based solvents. In the first step, data from physical simulations with MEA serve for the development of a surrogate model describing the general behaviour of a carbon capture process and is used for further solvent comparison. Followed by pilot-scale experiments under industrial operation conditions with the reference solvent (step two) and the novel solvent (step three), the surrogate model is adapted to experimental data to account for plant characteristics. By means of the surrogate model, optimal operation conditions regarding maximum energy efficiency are derived in 13 experiments for the reference solvent and in 16 experiments for the novel solvent. Finally, the optima allows for a fair solvent ranking.

Absorption of Carbon Dioxide using Enzyme Activated Amine Solution in Columns with Random Packings

Packed columns with structured or random packings are widely used in gas cleaning processes. Especially columns filled with random packings cover a large part of such applications in industrial practice. However, most of the recent investigation on carbon dioxide absorption from flue gases or other gas sources containing carbon dioxide (CO2) has been performed in columns equipped with structured packings, mostly due to their low pressure drop compared to other internals. CO2 usually is absorbed from the gas stream by means of a solvent. Amongst others, amine mixtures have gained a major role as a chemical solvent in this context. Beside the absorption kinetics and capacity, the energy demand for the regeneration of the solvent is a key factor for the operating costs of CO2 absorption plants.In previous studies, enzyme activated amines have been studied in lab scale, in order to enhance the absorption kinetics and to reduce the energy demand for regeneration. Besides the small scale, these studies focused almost exclusively on columns with structured packings. Despite the known benefits of structured packings, they can be inferior to random packings for systems with solid content and systems with mass transfer resistance in the liquid phase. Therefore, this work investigates columns at significantly larger scale equipped with random packings and presents the results of an extensive experimental study using the enzyme activated amine solution for the absorption of CO2. In particular, the different random packings McPac (Mackowiak 2001) from stainless steel and ENVIPAC from plastic have been studied in a test plant with diameter of ?? ?? =600 mm. Fluid dynamics and mass transfer characteristics have been measured using various liquid and gas loads, packing height and column diameter using the CO2 inlet concentrations of = 15 vol%.The experimental results are used for the validation of a process model, implemented in Aspen Plus® simulation software. A good agreement between experimental results and the simulation of the complex, reactive absorption system is established.

Ultra-microporous adsorbents prepared from vine shoots-derived biochar with high CO2 uptake and CO2/N2 selectivity

There is a growing interest in developing renewable biomass-based adsorbents to be used in numerous applications, including CO2 capture in postcombustion conditions. In the present study, several activated carbons (ACs) were produced from vine shoots-derived biochar through both physical and chemical activation using CO2 and KOH, respectively. The performance of these ACs was tested in terms of CO2 uptake capacity at an absolute pressure of 15 kPa and at different temperatures (0, 25, and 75 °C), apparent selectivity towards CO2 over N2, and isosteric heat of adsorption. At 25 °C, the chemically ACs with KOH impregnation exhibited the highest CO2 adsorption capacity, which was similar or even higher than those recently reported for a number of carbon-based adsorbents. However, the AC prepared through physical activation with CO2 at 800 °C and a soaking time of 1 h appears as the most promising adsorbent analyzed here, due to its higher CO2 uptake capacity and adsorption rate at relatively high temperature (75 °C), its relatively high selectivity at this temperature, and its apparently low energy demand for regeneration. Given that physical activation with CO2 is more feasible at industrial scale than chemical activation using corrosive alkalis, the results reported here are encouraging for further development of vine shoots-derived adsorbents.

Assessment of zeolite 13X and Lewatit\xae VP OC 1065 for application in a continuous temperature swing adsorption process for biogas upgrading

Two commercially available CO2-adsorbent materials (i.e., zeolite 13X (13X) and Lewatit® VP OC 1065 (Lewatit)) were evaluated for their applicability in a continuous temperature swing adsorption (TSA) process for biogas upgrading. The equilibrium adsorption characteristics of carbon dioxide and methane were determined by fixed bed and TGA tests. While relatively high CO2 capacities were measured for both materials (3.6 and 2.5 mol kg−1), neither of them was found to adsorb significant amounts of CH4. Lewatit showed to be fully regenerable at 95 °C, whereas for 13X, the regeneration was not complete at this temperature. However, 13X showed no degradation up to 190 °C, whereas Lewatit started to degrade at 110 and 90 °C when exposed to N2 and air, respectively. Fluidization tests showed that Lewatit provides a high mechanical stability, while on the contrary, the tested 13X showed considerable attrition. An equilibrium adsorption model was fitted to the measured CO2 adsorption data. The adsorption model was then integrated into an existing simulation tool for the proposed TSA process to roughly estimate the expectable regeneration energy demand for both materials. It was found that depending on the operating conditions, the regeneration energy demand lies between 0.32–0.54 kWhth/m3prodgas for 13X and 0.71–1.10 kWhth/m3prodgas for Lewatit. Since heat integration measures were not considered in the simulations, it was concluded that the proposed TSA process has a great potential to reduce the overall energy demand for biogas upgrading and that both tested adsorbent materials may be suitable for application in the proposed TSA process.

Efficiency Improvement of CO2 Capture

Carbon dioxide capturing processes from industrial gases are widely applied to enrich valuable gas and to reduce green-house gas emission. The highest amount of anthropogenic CO2 is emitted in flue gas form. Flue gas composition varies in a wide scale therefore designing such plants that are able to operate on a good removal efficiency scale is vital. A typical method for such gas separation is an absorber-desorber system where the absorbent is 30 w% aqueous monoethanolamine solution.The aim of this work is to setup computer based process model that is capable of simulating CO2 capture from flue gases and to study its performance at different operating conditions. We investigate possible process improvements by enhancing the CO2 removal efficiency with the variation of different key parameters and different plant setups. We also take into account the regeneration energy demand by optimizing the system to the lowest specific energy demand. Results show that the least attractive option is the overload of the existing absorber-desorber system. By introducing a second absorber-desorber step, high removal efficiency can be reached while maintaining low desorber temperature. The best performance can be achieved with increasing the absorber height and elevated desorber pressure that can reduce the specific regeneration energy especially at high removal efficiency region. This result is in agreement with the argued classical absorber design and operation philosophy that the absorber should be operated at extremely low loads, which is in association with overdesigned absorber column packing heights. This offers the possibility for flexible operation.

Pilot-scale experiments for post-combustion CO2 capture from gas fired power plants with a novel solvent

Aqueous MEA is the most common solvent used to absorb CO2. Its problem is that the energy required for solvent regeneration and solvent flow rate is high. This work focuses on introducing and developing a novel solvent to reduce both the regeneration energy demand and solvent flow rate. The novel solvent based on the mixture of MEA, TETA, AMPD and PZEA from Abadan Center of Research (ACOR100) was studied and compared to mono-ethanolamine (MEA). For both solvent, the regeneration energy is determined for different solvent flow rates at a constant CO2 removal rate of 90% and a low partial pressure (54mLbar). The optimum numbers for both the regeneration energy and solvent flow rate are found and compared to each other, for each of solvents. The resulting numbers of the ACOR100 indicate a considerable improvement compared to MEA with a reduction of about 25% in the regeneration energy and 27% in the solvent flow rate.

Non-Aqueous Solvent (NAS) CO2 Capture Process

Abstract The Non-Aqueous Solvent (NAS) CO2 Capture Process is being developed as an advanced, next-generation post-combustion capture technology for CO2 removal from power generation and industrial flue gas streams. The core of the NAS process has been the development of a family of CO2-selective NASs that have the potential to substantially reduce the thermal regeneration energy demand associated with solvent regeneration to ∼ 2,000 kJt/kg of CO2 captured. This paper discusses our rationale for selecting a NAS platform and provides results from the physical and thermodynamic characterization of the NASs, lab-scale testing results, and an update on our efforts to address specific process design challenges related to NAS processes for evaluation of the NAS CO2 capture process at the (large) bench-scale.

Development of HiCapt+TMProcess for CO2Capture from Lab to Industrial Pilot Plant

It is now well known that “first generation” MEA based post-combustion carbon capture processes require high energy consumption and have problems with solvent degradation due to oxygen. Nevertheless, it is the only available process for first industrial units. That is why <i>IFP Energies nouvelles<i/>, has developed HiCapt+ process, based on a conventional MEA solvent but using high performance oxidative inhibitors and higher amine concentration. These oxidative inhibitors enable HiCapt+’s process to use high solvent concentrations without corrosion or degradation problems and lead to reduction of the regeneration energy demand due to solvent flow rate reduction. Moreover, the huge reduction of solvent degradation rate avoids the difficult management of reclaiming unit, as well as avoiding high concentration of light degradation products in the treated flue gas, like NH<sub>3<sub/>.

Economic Evaluation of CO&lt;sub&gt;2&lt;/sub&gt; Separation Technologies in Chinese Refineries

With the clear emission reduction target of China for 2020, the refining industry as a large emission source inevitably plays a significant role. The paper confirmed and assessed three commercially available CO2separation technologies for refineries, vacuum swing adsorption (VSA), monoethanolamine (MEA) and membrane absorption (MA). The economic results indicate that the capital cost of constructing a CO2capture unit is 35.996 M¥, 34.418 M¥, 37.502 M¥, respectively. And the corresponding cost of avoided is 379.8 ¥/tCO2, 249.6 ¥/tCO2and 376.5 ¥/tCO2. Sensitivity analyses are also performed examining the effect of CO2price on economic feasibility, as well as improvements of regeneration energy demand and CO2capture system on the CO2avoided cost. The regeneration energy demand impacts the avoided cost significantly, whereas CO2capture system demonstrates insensitivity. Though the CO2avoided cost for MEA case is highest, MEA has been commercially the most available processe so far for existing refineries. However, MA will be the most promising alternative to chemical absorption in the future, provided that membrane performance is further improved. In addition, the CO2avoided cost of VSA is close to that of MEA, but other economic indicators are optimal due to a large amount of H2recovered. Currently, without any incentive and a major technological break-through, CO2capture from the source of hydrogen production units at Chinese refineries is the most attractive opportunity.

Experimental evaluation of Mg- and Ca-based synthetic sorbents for CO2 capture

Hydrogen with high purity can be directly derived from fossil and renewable energy sources, like natural gas, coal and biomass, by the so-called sorption-enhanced reforming (SER) and water gas shift (SEWGS) processes characterized by simultaneous CO2 capture.This paper deals with CO2 capture on a solid sorbent under cyclic (carbonation/decarbonation), industrially relevant conditions. Hydrotalcite-like compounds (double Mg/Al hydroxy-carbonates), in comparison to CaO-based sorbents, are characterized by a comparatively smaller energy demand for regeneration and the operating temperature range is much lower (200–400°C), making them particularly attractive for SEWGS processes.Different kinds of hydrotalcite were prepared and the Mg2+/Al3+ ratio, the effect of a promoter addition and the substitution of the bivalent cation (Ca instead of Mg) were investigated, with commercial and laboratory synthesized samples.Original and heat-treated hydrotalcite samples were characterized by XRD, BET and SEM-EDX in order to detect composition, crystalline phases and morphology. Sorption capacity was investigated under cyclic conditions by means of TGA-DSC. Step-response experiments were performed in a micro-reactor to evaluate the kinetic behavior, and a first-order-with-dead-time model for gas mixing was used to fit the results and work out the CO2 dynamic load on the solid phase.

Amine-based absorbents selection for CO2 membrane vacuum regeneration technology by combined absorption–desorption analysis

A novel membrane vacuum regeneration (MVR) technology was developed to achieve lower regeneration energy demand for CO2 absorption process. Sixteen different amine-based absorbents including primary, secondary, tertiary amines, polyamines, diamines, and sterically hindered amines were analyzed by combined absorption–desorption screening experiments for selecting the most effective absorbents for CO2 membrane vacuum regeneration (MVR) technology. The CO2 absorption experiments were conducted in a hollow fiber membrane contactor (HFMC) at 25°C and 12.5kPa CO2 partial pressure. The CO2 rich solvent was regenerated at 75°C and 20kPa regeneration pressure by using the MVR technology. The chain length, number of functional groups, side chain, and number of hydroxyl groups of amines were investigated to get a better understanding on the effects of the structure in the MVR process. The results show that the tertiary amines have greater regeneration performances than the primary amines, but the CO2 absorption rates of the tertiary amines are worse than the primary amines. For the polyamines, the absorption performance of polyamines can be improved by increasing the number of amine groups while the MVR performance of the polyamines can be reduced. Steric hindered amines exhibited greater MVR performances. In addition, amines with steric hindrance effect caused by the substitution of hydroxyl group or methyl group to amine group in structure has also shown good performance in the MVR process for CO2 desorption. The overall performance of amine-based absorbents was also investigated by an absorption–desorption characters analysis. It shows triethylenetetramine (TETA) and N-methyldiethanolamine (MDEA) have great average CO2 absorption rates and relatively high cyclic capacities per mole absorbent, and ethylenediamine (EDA) is considered to be the promising absorbent as cyclic capacity in mol CO2/kg absorbent. Diethanolamine (DEA) and 2-Amino-2-methyl-1-propanol (AMP) are found to have the best overall performances in terms of CO2 absorption rate at lean loading and cyclic capacity in mol CO2/mol absorbent. In terms of overall performance, MDEA is mostly recommended for using in MVR process. Sweeping steam can significantly improve MVR performance in most selected absorbents except AMP and 2-amino-2-hydroxymethyl-1,3- propanediol (THAM) absorbents which present the potential to reduce the regeneration energy demand by operating without sweeping steam. The study also finds that MVR shows better regeneration performance as compared to traditional thermal regeneration process at the same regeneration temperature.

Comparative study on differently concentrated aqueous solutions of MEA and TETA for CO2 capture from flue gases

Next to IGCC and oxyfuel technology amine scrubbing is one possible process pursued for industrial-scale CO2 capture from power plant flue gases. Aqueous solutions of Monoethanolamine (MEA) are commonly used for the existing amine scrubbing processes because of their high reaction kinetics during CO2 absorption. However, the required energy demand for regeneration of the MEA solution is comparably high, requiring improvements in process technology and solvent development. Within this work the results from lab-scale experimental research on the CO2 absorption from flue gases using differently concentrated aqueous solutions of MEA and Triethylenetetramine (TETA) are presented and discussed. The amine content of the solutions was varied in order to show the influence of concentration on CO2 loading, cyclic capacity and limitations within physical parameters. The equilibrium CO2 loading of the concentrated amine solutions was obtained at temperatures from 30 to 95°C using synthetic flue gas with different CO2 concentrations of up to 15vol% CO2. From these results the cyclic capacities of the different solutions are calculated and discussed with focus on the influence of the amine concentration. Furthermore MEA and TETA will be compared on molar and mass basis specifying the significance of TETA as polyamine and its advantages regarding the scrubbing process.