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Item type:Publication, Access status: without files , CHAPTER 10: Enzymatic Reactive Absorption and Distillation(Royal Society of Chemistry (RSC), 2019); ; ; ; In this work, innovative concepts for reactive separation processes, such as reactive absorption and distillation, that make use of bio-based catalysts, in specific enzymes, are discussed. Enzymatic Reactive Absorption (ERA) and Distillation (ERD) offer potential for energy and investment savings or improved selectivity by exploiting enzyme merits like high enantioselectivity and high reaction rates at milder reaction conditions than chemical catalysts. Potential process equipment, application strategies to supply enzyme for ERA and ERD processes as well as suitable modeling and design approaches are presented. Despite the huge potential, addressing these issues is crucial in order to promote ERA and ERD as vital technologies for process intensification in bio-based industries. The application of the enzyme carbonic anhydrase in an ERA column with common MDEA-based solvent can drastically improve the absorption of CO2 by more than 9-fold. Furthermore, the production of butyl butyrate and enantiomerically pure (R)-1-phenylethyl acetate or (S)-2-pentanol were successfully demonstrated in an ERD column. These processes provided high conversion rates of the substrates and purities of the product stream at milder process conditions compared to conventional processes.Publicationtype: Book Part209 2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Enzymatic reactive absorption of CO₂ in MDEA by means of an innovative biocatalyst delivery systemDue to the increasing world population and industrialization the worldwide energy requirement is also increasing. About 82% of the world's total primary energy supply stems from fossil sources and coal combustion in power plants accounted for 46% of the 32.4 Gt global carbon dioxide (CO2) emissions in 2014 (International Energy Agency, Key CO2 Emissions Trends: Excerpt from CO2 Emissions from Fuel Combustion (2016 edition)). The reduction of CO2 emissions from power plant flue gases is therefore essential to enable reliable and ecologically benign energy supply. An efficient technology to reduce CO2 emissions is reactive absorption in packed columns with aqueous amine-based absorption solvents, herein also called absorbents. The major drawback of conventional amine absorbents is their high absorption enthalpy, which causes high energy requirements during solvent regeneration. Alternative solvents that offer significantly lower absorption enthalpies suffer from lower absorption rates. To compensate for low absorption rates the enzyme carbonic anhydrase (CA) can be added to the absorbent to accelerate absorption kinetics by catalyzing the reaction between CO2 and water. For industrial applications, it can be desirable to immobilize CA which extends enzyme longevity by confining the enzyme to favorable process conditions, prevents unnecessary exposure to high process temperatures, and enables enzyme reuse. The CO2 absorption characteristics and handling properties of an innovative immobilized CA in the form of microparticles, called biocatalyst delivery system (BDS), were evaluated together with aqueous MDEA solvent. Operational feasibility parameters were validated in lab scale, followed by replicated CO2 absorption performance tests in a small demonstration scale counter-current packed column. A sixfold enhancement in total absorbed mole flow of CO2 in the presence of BDS was demonstrated versus blank MDEA solvent. Recyclability and longevity of BDS were validated.Publicationtype: Journal Article74 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Absorption of carbon dioxide using enzyme activated amine solution in columns with random packingsPacked 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 (Maćkowiak 2001) from stainless steel and ENVIPAC from plastic have been studied in a test plant with diameter of ds=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.Publicationtype: Journal Article25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Energy-efficient solvent regeneration in enzymatic reactive absorption for carbon dioxide capture(2017-12-15); ; ; ; Although recent studies on the application of enzyme-catalyzed reactive absorption of carbon dioxide (CO2) with thermodynamically favorable solvents such as tertiary amine N-methyldiethanolamine (MDEA) have demonstrated competitiveness with kinetically favorable solvents such as primary amine monoethanolamine (MEA), experimental data on the desorption of CO2 in MDEA are scarce. However, these data are necessary to validate the energetic benefit expected from an enzyme-catalyzed reactive absorption process with an aqueous MDEA solvent. To bridge this gap, the current work presents the experimental results of aqueous MDEA solvent regeneration at the pilot scale with consideration of different solvent flow rates, CO2 loadings and applied reboiler duties. Furthermore, a process model that accurately describes the experimental data was developed to evaluate the energy requirements in a closed-loop absorption-desorption process. For this purpose, the desorption process model was extended using a previously validated enzymatic reactive absorption model to determine the energy efficiency of the overall enzymatic reactive absorption-desorption process. Although the MEA benchmark process requires a specific reboiler duty of approximately 3.8MJ·kgCO2-1, it was found that this value could be reduced by more than 40% to 2.13MJ·kgCO2-1 with use of the enzymatic reactive absorption process based on aqueous MDEA solvent.Publicationtype: Journal Article29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Enzyme Carbonic Anhydrase Accelerated CO₂ Absorption in Membrane ContactorMembrane contactors offer a promising alternative to conventional CO2 absorption processes using columns. In a membrane contactor the advantages of absorption technology and membrane technology are combined as direct contact of the solution and gas feed stream is avoided by membrane barrier. In this study, the possibility of employing the enzyme carbonic anhydrase (CA) for the acceleration of CO2 reaction in MDEA and MEA solution in combination with the use of a membrane contactor was investigated in a lab scale module. The membranes employed in this study were microporous and specifically chosen to have both hydrophobic (bulk) and hydrophilic (surface) properties in order to avoid wetting of solution and reduce fouling by the enzymes simultaneously. By adding the enzyme carbonic anhydrase (CA), a significant improvement of CO2 absorption rate was observed in MDEA solution while a negative effect was observed in MEA solution. Meanwhile the porous hydrophobic membranes were coated with a highly selective poly(ionic liquids) layer increasing the affinity of CO2 towards the interfacial area and hence also the driving force. The concept may initially appear counter intuitive, as the dense membrane layer introduces an added resistance, however the active membrane material gave promising results and was observed to accelerate CO2 transport in MDEA solution. The combination of both enzyme and PILs resulted in synergies, which significantly improved CO2 absorption in MDEA solution.Publicationtype: Conference Paper79 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Pilot scale testing and modeling of enzymatic reactive absorption in packed columns for CO₂captureEfficient processes for carbon dioxide (CO2) capture from post-combustion flue gases are required to combat global climate change. A key stage in post-combustion capture is selective CO2 separation from the flue gas stream. Separation of CO2 from mixed gases using countercurrent gas–liquid absorption in packed columns is a well-established technology for treatment of industrial gas streams. This approach can be adapted to remove CO2 from post-combustion flue gas, however, process improvements are needed to minimize the corresponding capital costs and energy requirements. Special challenges for CO2 recovery from flue gas arise from the very large volumes of gas to be processed, the need to operate the process with an inlet flue gas stream at atmospheric pressure, and the high amount of energy required to regenerate the absorption liquid. Aqueous solutions of the tertiary amine N-methyldiethanolamine (MDEA) are commercially used for high pressure CO2 separation due to high loading capacity for CO2, relatively good chemical and thermal stability and low volatility. Application of MDEA-based solutions to ambient pressure separations, such as CO2 capture from flue gases, is challenging since high reaction rates are required. High reaction rates for the MDEA system are achievable at high temperatures, which is conflicting with the preference of low temperatures to exploit high absorption capacity. This conflict can be overcome with the addition of a rate enhancing catalyst that enables high reaction rates at low temperatures. To put this innovative breakthrough technology closer to industrial application CO2 absorption in 30–50 wt.% aqueous solutions of MDEA in absence and presence of the CO2 absorption enhancing enzyme carbonic anhydrase (CA) was evaluated in pilot scale. The pilot scale investigation employed a packed column for parametric testing. Test variables included the liquid phase composition (30–50 wt.% MDEA), the column liquid load (8–24 m3 m−2 h−1), the absorber temperature (20–40 °C), and the application of CA in a dissolved or immobilized form. The CO2 absorption mass transfer enhancement provided by CA was measured. In the presence of dissolved CA, 30 wt.% aqueous MDEA showed superior performance in terms of absorption rates compared to operation using 50 wt.% MDEA(aq). No significant change in the CO2 absorption rate was observed for operation at given loads between 20 °C and 40 °C with dissolved CA present. At 20 °C with 30 wt.% MDEA the absorption rate with dissolved CA increased by more than 9 times compared to the absorption rate without enzyme. These results broaden the operation window for efficient CO2 absorption using MDEA solutions and allow for the exploitation of new process regimes, wherein high equilibrium loadings are achievable by applying lower absorption temperatures. Based on the experimental results obtained with dissolved CA, a simplified rate-based model of enzymatic reactive absorption (ERA), accounting for enzyme accelerated reaction kinetics, was developed which was capable of accurately predicting CO2 absorption rate when compared with experimental data. Implemented in a process simulator the model allows for the detailed investigation of the process behavior and the complex interactions of ab- and desorption operations in the presence of the CA. The validated model is intended to guide future experimental work as well as further performance optimization. In addition to the work exploiting the catalyst in its free form, the utilization of CA immobilized in a granular form and held in the pockets of Katapak-SP packing was successfully demonstrated.Publicationtype: Journal Article61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Improving the energy efficiency of carbon capture processes - Combining enzyme accelerated solvent systems and improved contacting equipmentIn order to achieve the ambitious targets specified by the United Nations Framework Convention on Climate Change in 2011 and reduce GHG emission in the EU by 2020 at least 20% below those in 1990 carbon dioxide (CO2) emissions have to be reduced significantly. Fossil-fired power plants are identified as major targets for carbon capture processes, since they are responsible for 40 % of the total global CO2 emissions (Mondal et al., 2012). Efficient post-combustion capture of CO2is one of the most promising options to face this crucial challenge and to achieve at least the specified short-term targets (Rochelle, 2009).Publicationtype: Conference Paper41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Different Strategies for Accelerated CO₂ Absorption in Packed Columns by Application of the Biocatalyst Carbonic AnhydraseWithin this work, the combination of an energetically favorable aqueous N-Methyldiethanolamine (MDEA) solution and the enzyme carbonic anhydrase is investigated in a packed column pilot plant. The use of aqueous MDEA solution for CO2 separation is already known from natural gas applications, for which an increased driving force due to the higher partial pressures of CO2 overcompensates reaction kinetic limitations. The objective of the addition of carbonic anhydrase is to countervail the loss of separation efficiency caused by the lower driving force in CO2 capture from power plant flue gases. Hence, carbonic anhydrase acts as a key to harness the energetic advantage of these solvent systems. However, application of the enzyme also poses restrictions on the process. Especially compliance with the enzyme stability limits is challenging for desorption, which is generally performed at high temperatures. In order to determine an optimal implementation of the enzyme into the process the current work presents different strategies how to apply CA as a biocatalyst in reactive absorption processes and shows how absorption efficiency is influenced. For introducing the enzyme to a packed column two approaches are investigated in this study. The simplest way of application is to dissolve the enzyme in the solvent. This allows the enzyme to work exactly where the reaction kinetic limitation can be found, in the liquid boundary layer. However, due to the temperature sensitivity of the enzyme an additional enzyme recovery step prior to the desorber might be necessary if desorption is to be performed at high temperatures. The immobilization of the enzyme inside the absorption column presents an alternative to prevent this additional separation, but may cause additional mass transfer limitations at the solid particles in which the enzyme is immobilized. The immobilization and the necessity of a suitable packing in which the enzyme particles can be filled, also makes this strategy more complicated but allows placing the enzyme at a location of most suitable process conditions in the column. But most importantly it completely avoids that the enzymes experience high temperature in the desorber. Systematic investigations of the influence of specific liquid load, liquid inlet temperature, MDEA-concentration and enzyme immobilization on absorption performance are conducted. Dissolved enzyme showed a nearly three times higher absorption performance than the immobilized enzyme under equivalent operating conditions, however the immobilized enzyme concentration used was effectively 50 times lower, meaning the result is actually quite promising for immobilized CA. From the investigated operating conditions, a liquid inlet temperature of 20 °C, a MDEA concentration of 30 wt.-% and a liquid flow rate of 24 m3 m-2 h-1 showed the best absorption performance with the dissolved enzyme. The measured absorption rate was 7.57 times higher than without enzyme added.Publicationtype: Conference Paper102 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Enzyme Accelerated Carbon Capture in different Contacting Equipment - A Comparative Study(Elsevier, 2016-11); ; ; ; CO2 capture is an essential step for providing a sustainable and ecological solution to cope with increasing energy supply burning fossil fuels. However, industrial application of current CO2 capture technologies is limited due to the significant energy penalty. In order to reduce this energy penalty two different approaches of process intensification are examined in this study. The first approach aims at the intensification of mass transfer to compensate for low absorption rates of solvents with high capacity that would allow for more energy-efficient CO2 capture. Here the tertiary amine methyldiethanolamine (MDEA) is combined with a highly efficient biocatalyst, the enzyme Carbonic Anhydrase (CA), for which significant enhancement of absorption performance was demonstrated in literature. In addition to the intensification of the solvent system, the contacting of gas and liquid streams in ab- and desorption can be improved in intensified contacting devices (ICD). Here especially membrane contactors (MC) and rotating packed beds (RPB) are promising alternatives to classical packed columns. MC provide a well-defined interfacial area that is orders of magnitude higher than for conventional equipment and introduces additional operational flexibility, expressed by the independent flow ratio between liquid and gas phase. In a RPB centrifugal forces are exploited to increase acceleration of the liquid and improve turbulence and mass transfer. The rotational speed of the rotating packing introduces an additional degree of freedom compared to common static equipment. Both ICDs offer a very compact design. While both, ICD and the improved solvent system with CA, can significantly intensify the CO2 capture process, research on the combination of both is scarce. In order to evaluate the potential benefit of a joint implementation, a first step of imminent importance is to characterize the operating windows of such an intensified process. Based on prior results concerning the energy requirements for solvent regeneration, an aqueous amine solution with 30 wt.-% MDEA is investigated in this study without and with dissolved CA. In order to evaluate the potential improvement of a joint application of the ICD and the application of CA absorption experiments in a packed column and in the two ICDs are performed. While all three devices show similar absorption performance without CA added, the RPB offers the advantage to handle exceptionally high gas loads while the MC can be operated over a much wider range of liquid loads. When CA is added to the solvent system the packed column and the RPB show superior performance compared to the MC. While none of the combinations is generally superior, the different means for process intensification extent the operating window and facilitate improved absorption performances.Publicationtype: Conference Paper35 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 64