A comparison of different parameter correlation models and the validation of an MEA-based absorber model

AbstractConsiderable effort on research in CO2 capture technologies has been directed towards steady state systems while less seems to have been done for the same systems in transient state. This work presents a dynamic model for CO2 absorption using aqueous mono-ethanolamine (MEA). Validation against experimental results both obtained at steady state and dynamic conditions is included. A parametric sensitivity study of the underlying model equations is carried out based alternative parameter correlations for the reaction rate constant. It is concluded that validated results for one specific pilot plant don’t necessarily apply to other plants of different sizes under other operational conditions. Furthermore, a parametric sensitivity study for the other parameters as well as for the rest of the CO2 capture process is also warranted

Accelerated CO2 absorption in a membrane contactor using enzyme carbonic anhydrase

At the recent United Nations Climate Change conference (COP21) in Paris, France, 195 countries agreed on a plan to endeavor, to hold the global warming effect at less than 2 °C by 2020. In order to achieve this target, carbon capture technology for post combustion power plants will firmly remain part of the solution. CO2 capture in absorption towers with monoethanolamine (MEA) solvent has been the most investigated technology. Although MEA has a fast CO2 absorption rate, its use results in issues including corrosion of equipment, high energy demand for regeneration and degradation. MDEA (N-methyldiethanolamine) is an attractive alternative as it has a lower energy requirement for regeneration, is less corrosive and has greater chemical stability. The slower CO2 absorption reaction rate is the major drawback. The enzyme carbonic anhydrase (CA) catalyzes CO2 fixation in nature, by hydrating CO2 to bicarbonate, which in turn enhances the CO2 absorption rate [1]. In this study, the possibility of employing carbonic anhydrase for the acceleration of CO2 reaction in MDEA in combination with the use of a membrane contactor is investigated in a lab scale module. In a membrane contactor the advantages of absorption technology and membrane technology are combined, as direct contact between the solvent and gas feed stream are avoided. Operation problems, which are observed in absorption columns such as foaming, channeling and entrainment are minimized. The possibility of independent control of gas and liquid phases offers convenient operation flexibility. Compact membrane modules provide more efficient liquid-gas contact than in an absorption column and hence save space. In contrast to membrane technology, where nonporous selective membranes are used, the membrane contactor uses microporous membranes, which have a higher gas permeance without selectivity since the solvent can take up CO2 exclusively (selectivity is ideally infinitive). However, if the membrane pores become filled with solvent (wetted), the mass transfer resistance of the membrane becomes significant, resulting in unviable operation. The membranes employed in this study were chosen specifically to have both hydrophobic (bulk) and hydrophilic (surface) properties in order to avoid wetting of solvent and to simultaneously reduce fouling from the enzymes. Absorption measurements in the membrane contactor were performed using solvent systems of 30wt% MEA and 30wt% MDEA for comparison where a small amount of the enzyme was added. The enzyme carbonic anhydrase used in this study, was supplied by Novozymes A/S (Bagsvaerd, Denmark) as an extracellular protein of microbial origin [2]. The applied feed gas consisted of 15vol.% CO2 and 85 vol.% N2 represented of flue gas from coal-fired power plants, and the feed gas pressure was varied from slightly higher than atmospheric to ca. 2bar.The influence of the solvent holdup time (contact time) was studied and the duration of the enzyme activity over a test period of one week. In addition, the possibility of the enzyme deployment for desorption at mild temperature range (below 70°C) was investigated. The results showed significant acceleration of CO2 reaction in 30 wt% MDEA when enzyme was added to membrane contactor system. References 1. M.T. Gundersen et al., Enzymatically assisted CO2 removal from fluegas, Energy Procedia 63 (2014) 624–32. 2. Anna-Katharina Kunze et al., Reactive absorption of CO2 into enzyme accelerated solvents: From laboratory to pilot scale, Applied Energy 156 (2015) 676–685. Acknowledgment The authors thank the other partners of the FP7 project INTERACT. The research leading to these results has received funding from the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement n° 608535. See www.interact-co2.eu for further information

Modelling of a Solar Stove: Small Scale Concentrating System With Heat Storage: Potential For Cooking In Rural Areas, Zimbabwe

The central objective of the present research is to serve as an in-depth technical introduction to small-scale concentrating systems tailored for application especially in rural areas in Africa located outside the national electricity grids. For example, MScand doctoral-students recently matriculated on NUFU-sponsership at some universities in Africa (i.e Mozambique, Uganda, Tanzania, South Africa and Ethiopia) for research in solar-concentrator technologies will find most of the material in this work quite useful

Modelling of a Solar Stove: Small Scale Concentrating System With Heat Storage: Potential For Cooking In Rural Areas, Zimbabwe

The central objective of the present research is to serve as an in-depth technical introduction to small-scale concentrating systems tailored for application especially in rural areas in Africa located outside the national electricity grids. For example, MScand doctoral-students recently matriculated on NUFU-sponsership at some universities in Africa (i.e Mozambique, Uganda, Tanzania, South Africa and Ethiopia) for research in solar-concentrator technologies will find most of the material in this work quite useful.dr.scient.dr.scient

Modelling of a Solar Stove: Small Scale Concentrating System With Heat Storage: Potential For Cooking In Rural Areas, Zimbabwe

The central objective of the present research is to serve as an in-depth technical introduction to small-scale concentrating systems tailored for application especially in rural areas in Africa located outside the national electricity grids. For example, MScand doctoral-students recently matriculated on NUFU-sponsership at some universities in Africa (i.e Mozambique, Uganda, Tanzania, South Africa and Ethiopia) for research in solar-concentrator technologies will find most of the material in this work quite useful.dr.scient.dr.scient

CCS on Offshore Oil and Gas Installation - Design of Post Combustion Capture System and Steam Cycle

Most of the released CO2 on offshore oil and gas installation originates from the gas turbines that power the installations. For certain offshore installations, CO2 capture and storage (CCS) could be an alternative to decrease the CO2 emissions. When opting for a chemical absorption CO2 capture system, a heat source for the stripper reboiler is needed. Since most offshore installations are powered by simple cycle GTs, there is typically no steam available that could be used for stripper reboiler heat. A compact steam bottoming cycle could, in addition to providing the reboiler steam, partly or fully provide power from a steam turbine generator to the equipment in the CCS system, including CO2 compressors, pumps, and flue gas booster fan. Three different steam cycle configurations were designed, modeled, and simulated. The design of the post-combustion CO2 capture system is also presented but the main focus in the paper is on the steam cycle design. In addition to the energy and mass balance results, a weight assessment of the major equipment was done with the objective to come up with a simplified weight relationship for changes in the oil and gas installation size in terms of changes in total mass flow from the gas turbines. A steam cycle with a back-pressure steam turbine was ultimately selected. The back-pressure option was able to provide all necessary steam and power (with some margin) to the CO2 capture and compression system.publishedVersio

CCS on Offshore Oil and Gas Installation - Design of Post Combustion Capture System and Steam Cycle

Most of the released CO2 on offshore oil and gas installation originates from the gas turbines that power the installations. For certain offshore installations, CO2 capture and storage (CCS) could be an alternative to decrease the CO2 emissions. When opting for a chemical absorption CO2 capture system, a heat source for the stripper reboiler is needed. Since most offshore installations are powered by simple cycle GTs, there is typically no steam available that could be used for stripper reboiler heat. A compact steam bottoming cycle could, in addition to providing the reboiler steam, partly or fully provide power from a steam turbine generator to the equipment in the CCS system, including CO2 compressors, pumps, and flue gas booster fan. Three different steam cycle configurations were designed, modeled, and simulated. The design of the post-combustion CO2 capture system is also presented but the main focus in the paper is on the steam cycle design. In addition to the energy and mass balance results, a weight assessment of the major equipment was done with the objective to come up with a simplified weight relationship for changes in the oil and gas installation size in terms of changes in total mass flow from the gas turbines. A steam cycle with a back-pressure steam turbine was ultimately selected. The back-pressure option was able to provide all necessary steam and power (with some margin) to the CO2 capture and compression system.publishedVersio

Baseline test of capture from bio flue gas with MEA at Tiller plant

A campaign on carbon capture from biomass flue gas was carried out at Tiller pilot plant during 30th September - 8th November 2019. Biomass was supplied by Drax power station. SRD of 3.57MJ/kgCO2 was obtained for MEA, in agreement with typical values for MEA. The plant was down at various time during the campaign due to operational issues mostly linked to the accidental short circuit of one part of the flue gas filter elements. These incidents, although unwanted, revealed the importance of keeping control of the particulate concentration in the flue gas to prevent high amine emissions due to aerosols. Increased levels of typical degradation products for MEA were found at the end of campaign. This can be explained by the high levels of ash dust in flue gas earlier in the campaign when the filter was not working properly. Flue gas was characterised using various set ups: FTIR, CPC, gravimetric and ELPI, for gaseous and particulate measurements at four different locations between the burner and the flue gas exit to the atmosphere. Zero emission of amine from the plant was achieved when the filter was working properly. Particulate effect on emissions was studied by partial bypass of the filter. Relationship is established between emissions, particle mass and particle number. Particle size distribution measurements identified region of particles responsible for emissions.publishedVersio

Simplified model description of a CLOP reactor for system simulation and analysis

In order to perform overall system simulations and optimization at the flowsheet level, simplified models of process units are required. We present a simplified model of the CLOP reactor (chemical looping for oxygen production) and compare it against a rigorous dynamic fixed bed model, which uses a 1D phenomenological approach. The model is validated towards the detailed model to verify that the performance is captured correctly. In this way, after model validation, system simulations can be performed and optimized both based on process flow configuration, and temperature/pressure ranges. When combined in a process simulation, the model can give an understanding of the potential of a given oxygen carrier material (OCM) for usage in power plants utilizing the novel COMPOSITE concept, which is a concept for energy production with CO2 capture. Both the rigorous and the simplified models are based on using fuel burning to maintain the desired operating reactor temperature. The model can be used for finding equilibrium points in the air and fuel reactors, and thus identify what is the limiting factor for the reactor performance.publishedVersio

Phase Equilibrium Measurements of Ammonia Based CO2 Capture Solvents with FTIRr for Gas Phase Analysis

Vapor-liquid-solid equilibrium (VLSE) was measured for four solvents (blends A-D) at atmospheric pressure in a low-temperature setup at 20 oC and at 20, 35, and 55 oC for blend E. The blends are ammonia-based aqueous solutions selected to evaluate the potential for CO2 capture at post-combustion conditions with high pressure solvent regeneration. The set-up was modified to enable analysis of ammonia and CO2 in the vapor phase using FTIR®. Solid formation in the liquid phase was monitored using optical probes FBRM® and PVM® to determine maximum CO2 loadings for the precipitation-free range