Publications
163 results found
Heuberger C, Staffell I, Shah N, et al., 2017, An MILP modeling approach to systemic energy technology valuation in the 21st Century energy system, 13th International Conference on Greenhouse Gas Control Technologies, Publisher: Elsevier, Pages: 6358-6365, ISSN: 1876-6102
New cannot be measured with old. The transformation of the electricity system from a network of fossil-based dispatchable power plants to one with large amounts of intermittent renewable power generation, flexible loads and markets, requires a concurrent development of new evaluation tools and metrics. The focus of this research is to investigate the value of power technologies in order to support decision making on optimal power system design and operation. Technology valuation metrics need to consider the complexity and interdependency of environmental and security objectives, rather than focusing on individual cost-competitiveness of technologies outside of the power system. We present the System Value as a new technology valuation metric, based on a mixed-integer linear program (MILP) formulation of a national-scale electricity system. The Electricity System Optimization model is able to capture detailed technical operation of the individual power plants as well as environmental and security requirements on the system level. We present a case study on the System Value of onshore wind power plants in comparison with Carbon Capture and Storage (CCS) equipped gas-fired power plants in a 2035 UK electricity system. Under the given emission constraints, the deployment of both technologies reduce total system cost of electricity generation. In the case of CCS-equipped power plants the reductions in total system cost are 2 to 5 times higher than for the deployment of onshore wind capacity.
Bui M, Fajardy M, Dowell NM, 2017, Thermodynamic Evaluation of Carbon Negative Power Generation: Bio-energy CCS (BECCS), Energy Procedia, Vol: 114, Pages: 6010-6020, ISSN: 1876-6102
Bio-energy with carbon capture and storage (BECCS) is an important greenhouse gas removal (GGR) technology with the potential to provide significant reductions in atmospheric CO2 concentration. The power generation efficiency of BECCS can be improved by using heat recovered from flue gas to supply energy requirements of the solvent regeneration process. This paper assesses the influence of solvent selection and biomass co-firing proportion on recoverable heat, energy efficiency and carbon intensity of a 500 MW pulverized fuel BECCS system. The effects of (i) coal type (high and medium sulphur content), (ii) biomass type (wheat straw and clean wood chips, (iii) variable moisture content, and (iv) biomass co-firing % on AFT and emissions of SOX and NOX was evaluated. Compared to firing of coal alone, co-firing low moisture biomass generated higher adiabatic flame temperature. As biomass co-firing proportion increased, SOX emissions decreased, whereas NOX emissions increased with greater AFT. Factors that enhanced BECCS efficiency included the use of high performance solvents and higher heat recovery (higher AFT and flue gas flow rate). These results lead to the development of a performance matrix which summarizes the effect of key process parameters.
Cabral R, Mac Dowell N, 2017, A novel methodological approach for achieving $/MWh cost reduction of CO2 capture and storage (CCS) processes, Applied Energy, Vol: 205, Pages: 529-539, ISSN: 1872-9118
Carbon capture and storage is widely recognised as essential for the cost effective decarbonisation of the power and industrial sectors. However its capital and operating costs remain a barrier to deployment, with significant reduction in the cost per unit of decarbonised product considered vital. In the context of power generation, this is best expressed in terms of cost per MWh of electricity generated. To achieve a meaningful reduction in the cost of low carbon electricity, capital costs must also be reduced. Thus, this work presents a novel approach for identifying system improvements via a combination of process integration and intensification based on minimisation of thermodynamic losses. Application of this methodology to an oxy-combustion CCS process led to a 3% increase of net efficiency and a 13% reduction of £/MWh of electricity.
Heuberger C, Rubin ES, Staffell I, et al., 2017, Power Capacity Expansion Planning Considering Endogenous Technology Cost Learning, Applied Energy, Vol: 204, Pages: 831-845, ISSN: 0306-2619
We present an power systems optimisation model for national-scale power supply capacity expansion considering endogenous technology cost reduction (ESO-XEL). The mixed-integer linear program minimises total system cost while complying with operational constraints, carbon emission targets, and ancillary service requirements. A data clustering technique and the relaxation of integer scheduling constraints is evaluated and applied to decrease the model solution time. Two cost learning curves for the different power technologies are derived: one assuming local learning effects, the other accounting for global knowledge spill-over. A piece-wise linear formulation allows the integration of the exponential learning curves into the ESO-XEL model. The model is applied to the UK power system in the time frame of 2015 to 2050. The consideration of cost learning effects moves optimal investment timings to earlier planning years and influences the competitiveness of technologies. In addition, the maximum capacity build rate parameter influences the share of power generation significantly; the possibility of rapid capacity build-up is more important for total system cost reduction by 2050 than accounting for technology cost reduction.
Leeson D, Fennell P, Mac Dowell N, et al., 2017, Simultaneous design of separation sequences and whole process energy integration, CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 125, Pages: 166-180, ISSN: 0263-8762
This paper presents a novel methodology for the optimisation of the preliminary design of heat-integrated multicomponent distillation sequences. This is achieved through use of a reduced process superstructure where the role of splitting each adjacent key component pair is assigned to an individual separation column, greatly reducing the size and complexity of the problem. This methodology uses information about other process streams on site with which heat can be exchanged within the initial design in order to find a plant-wide optimal separation configuration with the aim of reducing the cost of heating provided by utilities including those used for heating and cooling process streams. In order that this model can be formulated as a mixed-integer linear program, this model utilises a discretised temperature grid where stream temperatures are allowed to vary. This methodology was tested on an example of a mixed alkane feed stream, with the sequence changing dependent on the degree of process integration. The method was found to have the potential for significant cost reductions compared to a heuristic design, with the example exhibiting a cost saving of over 50% and a reduction in CO2 associated with process heating of almost 60%, though the magnitude of these savings is highly dependent on the specific example to which it is applied.
Heuberger CF, Staffell I, Shah N, et al., 2017, The changing costs of technology and the optimal investment timing in the power sector
Brown S, Gadikota G, Mac Dowell N, 2017, Modelling the adsorption-desorption behavior of CO2 in shales for permanent storage of CO2 and enhanced hydrocarbon extraction, 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 6942-6949, ISSN: 1876-6102
Agada S, Kolster C, Williams G, et al., 2017, Sensitivity analysis of the dynamic CO2 storage capacity estimate for the Bunter Sandstone of the UK Southern North Sea, 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 4564-4570, ISSN: 1876-6102
Mota-Martinez MT, Hallett J, Mac Dowell N, 2017, Screening solvents properties for CO2 capture based on the process performance, 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 1551-1557, ISSN: 1876-6102
Soltani SM, Fennell PS, Mac Dowell N, 2017, A parametric study of CO2 capture from gas-fired power plants using monoethanolamine (MEA), International Journal of Greenhouse Gas Control, Vol: 63, Pages: 321-328, ISSN: 1750-5836
The value of dispatchable, low carbon thermal power plants as a complement to intermittent renewable energy sources is becoming increasingly recognised. In this study, we evaluate the performance of post-combustion CO2 capture using monoethanolamine (MEA) retrofitted to a 600 MW CCGT, with and without exhaust gas recycle (EGR). Our results suggest that the EGR ratio plays a primary role in the regeneration energy penalty of the process. We contrast a gas-CCS process with its coal counterpart and show that whilst CCGTs have a greater energy penalty per tonne of CO2 captured than coal (i.e., GJtCO2Gas>GJtCO2Coal), owing to the high thermal efficiencies of CCGTs relative to coal-fired power plants, the energy penalty per MWh of low carbon energy generated is lower for gas than it is for coal (i.e., GJMWhGas<GJMWhCoal), making CCGT-CCS an attractive choice for low carbon electricity generation.
Bui M, Fajardy M, Mac Dowell N, 2017, Bio-Energy with CCS (BECCS) performance evaluation: Efficiency enhancement and emissions reduction, APPLIED ENERGY, Vol: 195, Pages: 289-302, ISSN: 0306-2619
In this study we evaluate the feasibility of the recovery of waste heat from the power plant boiler system of a pulverised fuel power plant with amine-based CO2 capture. This recovered heat can, as a function of fuel type and solvent selection, provide up to 100% of the heat required for solvent regeneration, thus obviating the need for withdrawing steam from the power plant steam cycle and significantly reducing the efficiency penalty imposed upon the power plant by the CO2 capture process. In studying the thermochemistry of the combustion process, it was observed that co-firing with low moisture biomass achieved higher adiabatic flame temperatures (AFT) than coal alone. The formation and emission of SOX reduced as biomass co-firing proportion increased, whereas NOX emissions were observed to be a function of AFT. The power generation efficiency of a 500 MW 50% co-firing BECCS system increased from 31%HHV with a conventional MEA solvent, to 34%HHV with a high performance capture solvent. The heat recovery approach described in this paper enabled a further efficiency increase up to 38%HHV with the high performant solvent. Such a system was found to remove 0.83 MtCO2 from the atmosphere per year at 90% capacity factor.
Mac Dowell N, Fajardy M, 2017, Inefficient power generation as an optimal route to negative emissions via BECCS?, Environmental Research Letters, Vol: 12, ISSN: 1748-9326
Current ambitions to limit climate change to no more than 1.5 °C–2 °C by the end of the 21st century rely heavily on the availability of negative emissions technologies (NETs)—bioenergy with CO2 capture and storage (BECCS) and direct air capture in particular. In this context, these NETs are providing a specific service by removing CO2 from the atmosphere, and therefore investors would expect an appropriate risk-adjusted rate of return, varying as a function of the quantity of public money involved. Uniquely, BECCS facilities have the possibility to generate both low carbon power and remove CO2 from the atmosphere, but in an energy system characterised by high penetration of intermittent renewable energy such as wind and solar power plants, the dispatch load factor of such BECCS facilities may be small relative to their capacity. This has the potential to significantly under utilise these assets for their primary purpose of removing CO2 from the atmosphere. In this study, we present a techno-economic environmental evaluation of BECCS plants with a range of operating efficiencies, considering their full- and part-load operation relative to a national-scale annual CO2 removal target. We find that in all cases, a lower capital cost, lower efficiency BECCS plant is superior to a higher cost, higher efficiency facility from both environmental and economic perspectives. We show that it may be preferable to operate the BECCS facility in base-load fashion, constantly removing CO2 from the atmosphere and dispatching electricity on an as-needed basis. We show that the use of this 'spare capacity' to produce hydrogen for, e.g. injection to a natural gas system for the provision of low carbon heating can add to the overall environmental and economic benefit of such a system. The only point where this hypothesis appears to break down is where the CO2 emissions associated with the biomass supply chain are sufficiently large so as to eliminate the service of CO
Leeson D, Mac Dowell N, Shah N, et al., 2017, A Techno-economic analysis and systematic review of carbon capture and storage (CCS) applied to the iron and steel, cement, oil refining and pulp and paper industries, as well as other high purity sources, International Journal of Greenhouse Gas Control, Vol: 61, Pages: 71-84, ISSN: 1750-5836
In order to meet the IPCC recommendation for an 80% cut in CO2 emissions by 2050, industries will be required to drastically reduce their emissions. To meet these targets, technologies such as carbon capture and storage (CCS) must be part of the economic set of decarbonisation options for industry. A systematic review of the literature has been carried out on four of the largest industrial sectors (the iron and steel industry, the cement industry, the petroleum refining industry and the pulp and paper industry) as well as selected high-purity sources of CO2 from other industries to assess the applicability of different CCS technologies. Costing data have been gathered, and for the cement, iron and steel and refining industries, these data are used in a model to project costs per tonne of CO2 avoided over the time period extending from first deployment until 2050. A sensitivity analysis was carried out on the model to assess which variables had the greatest impact on the overall cost of wide-scale CCS deployment for future better targeting of cost reduction measures. The factors found to have the greatest overall impact were the initial cost of CCS at the start of deployment and the start date at which large scale deployment is started, whilst a slower initial deployment rate after the start date also leads to significantly increased costs.
Brandl P, Soltani SM, Fennell PS, et al., 2017, Evaluation of cooling requirements of post-combustion CO2 capture applied to coal-fired power plants, Chemical Engineering Research and Design, Vol: 122, Pages: 1-10, ISSN: 1744-3598
Whilst CO2 capture and storage (CCS) technology is widely regarded as being an important tool in mitigating anthropogenic climate change, care must be taken that its extensive deployment does not substantially increase the water requirements of electricity generation. In this work, we present an evaluation of the cooling demand of an amine-based post-combustion CO2 capture process integrated with a coal-fired power plant. It is found that the addition of a capture unit translates into an increase in the total cooling duty of ≈47% (subcritical), ≈33% (supercritical) and ≈31% (ultra-supercritical) compared to a power plant without capture. However, as the temperature at which this cooling is required varies appreciably throughout the integrated power capture process, it is found that his increase in cooling duty (MW) does not necessarily lead to an increase in cooling water usage (kg/MW). Via a heat integration approach, we demonstrate how astute cascading of cooling water can enable a reduction of cooling water requirements of a decarbonised power plant relative to an unmitigated facility. This is in contrast to previous suggestions that the addition of CCS would double the water footprint.
Fajardy M, Mac Dowell N, 2017, Can BECCS deliver sustainable and resource efficient negative emissions?, Energy & Environmental Science, Vol: 10, Pages: 1389-1426, ISSN: 1754-5706
Negative emissions technologies (NETs) in general and Bioenergy with CO2 Capture and Storage(BECCS) in particular are commonly regarded as vital yet controversial to meeting our climategoals. In this contribution we present a whole-systems analysis of the BECCS value chain associatedwith the cultivation, harvesting, transport and conversion in dedicated biomass powerstations in conjunction with CCS, of a range of biomass resources – both dedicated energy crops(miscanthus, switchgrass, short rotation coppice willow), and agricultural residues (wheat straw).We explicitly consider the implications of sourcing the biomass from different regions, climatesand land types. The water, carbon and energy footprints of each value chain were calculated,and their impact on the overall system water, carbon and power efficiencies were evaluated. Anextensive literature review was performed and a statistical analysis of the available data is presented.In order to describe the dynamic greenhouse gas balance of such as system, a yearlyaccounting of the emissions was performed over the lifetime of a BECCS facility, and the carbon"breakeven time" and lifetime net CO2 removal from the atmosphere were determined. The effectsof direct and indirect land use change were included, and were found to be a key determinant ofthe viability of a BECCS project. Overall we conclude that, depending on the conditions of itsdeployment, BECCS could lead to both carbon positive and negative results. The total quantity ofCO2 removed from the atmosphere over the project lifetime and the carbon breakeven time wereobserved to be highly case specific. This has profound implications for the policy frameworks requiredto incentivise and regulate the widespread deployment of BECCS technology. The resultsof a sensitivity analysis on the model combined with the investigation of alternate supply chainscenarios elucidated key levers to improve the sustainability of BECCS: 1) measuring and limitingthe im
Mac Dowell N, Fennell PS, Shah N, et al., 2017, The role of CO2 capture and utilization in mitigating climate change, Nature Climate Change, Vol: 7, Pages: 243-249, ISSN: 1758-678X
To offset the cost associated with CO2 capture and storage (CCS), there is growing interest in finding commercially viable end-use opportunities for the captured CO2. In this Perspective, we discuss the potential contribution of carbon capture and utilization (CCU). Owing to the scale and rate of CO2 production compared to that of utilization allowing long-term sequestration, it is highly improbable the chemical conversion of CO2 will account for more than 1% of the mitigation challenge, and even a scaled-up enhanced oil recovery (EOR)-CCS industry will likely only account for 4–8%. Therefore, whilst CO2-EOR may be an important economic incentive for some early CCS projects, CCU may prove to be a costly distraction, financially and politically, from the real task of mitigation.
Mechleri E, Fennell PS, Mac Dowell N, 2017, Optimisation and evaluation of flexible operation strategies for coal- and gas-CCS power stations with a multi-period design approach, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 59, Pages: 24-39, ISSN: 1750-5836
Thermal power plants are increasingly required to balance power grids by compensating for the intermittent electricity supply from renewable energy resources. As CO2 capture and storage is integrated with both coal- and gas-fired power plants, it is vital that the emission mitigation technology does not compromise their ability to provide this high-value service. Therefore, developing optimal process operation strategies is vital to maximise both the value provided by and the profitability of these important assets. In this work, we present models of coal- and gas-fired power plants, integrated with a post-combustion CO2 capture process using a 30 wt% monoethanolamine (MEA) solvent. With the aim to decoupling the power and capture plants in order to facilitate profit maximising behaviour, a multi-period dynamic optimisation problem was formulated and solved using these models. Four distinct scenarios were evaluated: load following, solvent storage, exhaust gas by-pass and variable solvent regeneration (VSR). It was found that for both coal- and gas-fired power plants, the VSR strategy is consistently the most profitable option. The performance of the exhaust by-pass scenario is a strong function of the carbon prices and is only selected at very low carbon prices. The viability of the solvent storage strategy was found to be a strong function of the capital cost associated with the solvent storage infrastructure. When the cost of the solvent tanks has been paid off, then the solvent storage scenario is 3.3% and 8% more profitable than the baseline for the pulverised coal and gas-fired power plants, respectively. Sensitivity analyses showed that, for all strategies, the flexibility benefit declined with reduced carbon and fuel prices, while a “peakier” electricity market, characteristic of one with significant quantities of intermittent renewables deployment, more significantly rewarded flexible operation.
Kolster C, Mechleri E, Krevor S, et al., 2017, The role of CO<inf>2</inf> purification and transport networks in carbon capture and storage cost reduction, International Journal of Greenhouse Gas Control, Vol: 58, Pages: 127-141, ISSN: 1750-5836
A number of Carbon Capture and Storage projects (CCS) are under way around the world, but the technology's high capital and operational costs act as a disincentive to large-scale deployment. In the case of both oxy-combustion and post-combustion CO 2 capture, the CO 2 compression and purification units (CO 2 CPU) are vital, but costly, process elements needed to bring the raw CO 2 product to a quality that is adequate for transport and storage. Four variants of the CO 2 CPU were modelled in Aspen HYSYS each of which provide different CO 2 product purities at different capital and operating costs. For each unit, a price of CO 2 is calculated by assuming that it is an independent entity in which to invest and the internal rate of return (IRR) must be greater or equal to the minimum rate of return on investment. In this study, we test the hypothesis that, owing to the fact that CO 2 will likely be transported in multi-source networks, not all CO 2 streams will need to be of high purity, and that it may be possible to combine several sources of varying purity to obtain an end-product that is suitable for storage. We find that, when considering study generated costs for an example network in the UK, optimally combining these different sources into one multi-source transport network subject to a minimum CO 2 purity of 96% can reduce the price of captured CO 2 by 17%.
Kolster C, Mechleri E, Krevor S, et al., 2017, The role of CO2 purification and transport networks in carbon capture and storage cost reduction, International Journal of Greenhouse Gas Control, Vol: 58, Pages: 127-141, ISSN: 1750-5836
A number of Carbon Capture and Storage projects (CCS) are under way around the world, but the technology's high capital and operational costs act as a disincentive to large-scale deployment. In the case of both oxy-combustion and post-combustion CO2 capture, the CO2 compression and purification units (CO2CPU) are vital, but costly, process elements needed to bring the raw CO2 product to a quality that is adequate for transport and storage. Four variants of the CO2CPU were modelled in Aspen HYSYS each of which provide different CO2 product purities at different capital and operating costs. For each unit, a price of CO2 is calculated by assuming that it is an independent entity in which to invest and the internal rate of return (IRR) must be greater or equal to the minimum rate of return on investment. In this study, we test the hypothesis that, owing to the fact that CO2 will likely be transported in multi-source networks, not all CO2 streams will need to be of high purity, and that it may be possible to combine several sources of varying purity to obtain an end-product that is suitable for storage. We find that, when considering study generated costs for an example network in the UK, optimally combining these different sources into one multi-source transport network subject to a minimum CO2 purity of 96% can reduce the price of captured CO2 by 17%.
Mechleri E, Brown S, Fennell PS, et al., 2017, CO2 capture and storage (CCS) cost reduction via infrastructure right-sizing, CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 119, Pages: 130-139, ISSN: 0263-8762
Bhave A, Taylor RHS, Fennell P, et al., 2017, Screening and techno-economic assessment of biomass-based power generation with CCS technologies to meet 2050 CO2 targets, APPLIED ENERGY, Vol: 190, Pages: 481-489, ISSN: 0306-2619
Biomass-based power generation combined with CO2 capture and storage (Biopower CCS) currently represents one of the few practical and economic means of removing large quantities of CO2 from the atmosphere, and the only approach that involves the generation of electricity at the same time. We present the results of the Techno-Economic Study of Biomass to Power with CO2capture (TESBiC) project, that entailed desk-based review and analysis, process engineering, optimisation as well as primary data collection from some of the leading pilot demonstration plants. From the perspective of being able to deploy Biopower CCS by 2050, twenty-eight Biopower CCS technology combinations involving combustion or gasification of biomass (either dedicated or co-fired with coal) together with pre-, oxy- or post-combustion CO2 capture were identified and assessed. In addition to the capital and operating costs, techno-economic characteristics such as electrical efficiencies (LHV% basis), Levelised Cost of Electricity (LCOE), costs of CO2 captured and CO2 avoided were modelled over time assuming technology improvements from today to 2050. Many of the Biopower CCS technologies gave relatively similar techno-economic results when analysed at the same scale, with the plant scale (MWe) observed to be the principal driver of CAPEX (£/MWe) and the cofiring % (i.e. the weighted feedstock cost) a key driver of LCOE. The data collected during the TESBiC project also highlighted the lack of financial incentives for generation of electricity with negative CO2 emissions.
Budinis S, Mac Dowell N, Krevor S, et al., 2017, Can carbon capture and storage unlock `unburnable carbon'?, 13th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: Elsevier Science BV, Pages: 7504-7515, ISSN: 1876-6102
The concept of ‘unburnable carbon’ emerged in 2011, and stems from the observation that if all known fossil fuel reserves are extracted and converted to CO2(unabated), it would exceed the carbon budget and have a very significant effect on the climate. Therefore, if global warming is to be limited to the COP21 target, some of the known fossil fuel reserves should remain unburnt. Several recent reports have highlighted the scale of the challenge, drawing on scenarios of climate change mitigation and their implications for the projected consumption of fossil fuels. Carbon Capture and Storage (CCS) is a critical and available mitigation opportunity and its contributionto timely and cost-effective decarbonisation of the energy system is widely recognised. However, while some studies have considered the role of CCS in enabling access to more fossil fuels, no detailed analysis on this issue has been undertaken. This paper presents a critical review focusing on the technologies that can be applied to enable access to, or ‘unlock’, fossil fuel reserves in a way that will meet climate targets and mitigate climate change. It also quantifies the impact of CCS in unlocking unburnable carbon in the first and in the second half of the century.
Bui M, Fajardy M, MacDowell N, 2017, Bio-energy with carbon capture and storage (BECCS): Opportunities for efficiency improvement, Pages: 661-674
Mechleri E, Lawal A, Ramos A, et al., 2016, Process control strategies for flexible operation of post-combustion CO2 capture plants, International Journal of Greenhouse Gas Control, Vol: 57, Pages: 14-25, ISSN: 1750-5836
With increasing penetration of intermittent renewable energy into the electricity grid, one can expect thermal power plants to be required to operate in a more dynamic fashion, with more frequent departures from design point operation. However, the application of optimal control strategies can offer solutions to these operational challenges, associated with the integration of the power plant with the capture plant. In this paper a process control strategy is developed in order to select the optimal control variables for a PCC process. In addition, economically efficient control structures for operation of a post-combustion capture process with minimum energy requirements for coal and natural gas power plant are designed. The results have shown that with an appropriate and well-tuned control strategy, it is possible to maintain critical parameters, such as the degree of CO2 capture, at the desired set-point, even during periods of significant fluctuation in the power plant load and even if based on simple and well established control technologies, such as PID, avoids the need for more risky solutions such as adding solvent storage tanks to the process.
Porter RTJ, Fairweather M, Kolster C, et al., 2016, Cost and performance of some carbon capture technology options for producing different quality CO2 product streams, International Journal of Greenhouse Gas Control, Vol: 57, Pages: 185-195, ISSN: 1750-5836
A techno-economic assessment of power plants with CO2 capture technologies with a focus on process scenarios that deliver different grades of CO2 product purity is presented. The three leading CO2 capture technologies are considered, namely; oxyfuel combustion, pre-combustion and post-combustion capture. The study uses a combination of process simulation of flue gas cleaning processes, modelling with a power plant cost and performance calculator and literature values of key performance criteria in order to evaluate the performance, cost and CO2 product purity of the considered CO2 capture options. For oxyfuel combustion capture plants, three raw CO2 flue gas processing strategies of compression and dehydration only, double flash system purification and distillation purification are considered. Analysis of pre-combustion capture options is based on integrated gasification combined cycle plants using physical solvent systems for capturing CO2 and sulfur species via three routes; co-capture of sulfur impurities with the CO2 stream using Selexol™ solvent, separate capture of CO2 and sulfur impurities using Selexol™, and Rectisol® solvent systems for separate capture of sulfur impurities and CO2. Analysis of post-combustion capture plants was made with and without some conventional pollution control devices. The results highlight the wide variation in CO2 product purity for different oxyfuel combustion capture scenarios and the wide cost variation for the pre-combustion capture scenarios. The post-combustion capture plant with conventional pollution control devices offers high CO2 purity (99.99 mol%) for average cost of considered technologies. The calculations performed will be of use in further analyses of whole chain CCS for the safe and economic capture, transport and storage of CO2.
Smit B, Graham R, Styring P, et al., 2016, CCS - A technology for the future: general discussion, Faraday Discussions, Vol: 192, Pages: 303-335, ISSN: 1359-6640
Lee JM, Rochelle G, Styring P, et al., 2016, CCS - A technology for now: general discussion., Faraday Discuss, Vol: 192, Pages: 125-151, ISSN: 1359-6640
Wilson G, Trusler M, Yao J, et al., 2016, End use and disposal of CO2 - storage or utilisation?: general discussion, Faraday Discussions, Vol: 192, Pages: 561-579, ISSN: 1359-6640
Mac Dowell N, Fajardy M, 2016, On the potential for BECCS efficiency improvement through heat recovery from both post-combustion and oxy-combustion facilities, Faraday Discussions, Vol: 192, Pages: 241-250, ISSN: 1359-6640
In order to mitigate climate change to no more than 2 °C, it is well understood that it will be necessary to directly remove significant quantities of CO2, with bioenergy CCS (BECCS) regarded as a promising technology. However, BECCS will likely be more costly and less efficient at power generation than conventional CCS. Thus, approaches to improve BECCS performance and reduce costs are of importance to facilitate the deployment of this key technology. In this study, the impact of biomass co-firing rate and biomass moisture content on BECCS efficiency with both post- and oxy-combustion CO2 capture technologies was evaluated. It was found that post-combustion capture BECCS (PCC-BECCS) facilities will be appreciably less efficient than oxy-combustion capture BECCS (OCC-BECCS) facilities. Consequently, PCC-BECCS have the potential to be more carbon negative than OCC-BECCS per unit electricity generated. It was further observed that the biomass moisture content plays an important role in determining the BECCS facilities’ efficiency. This will in turn affect the enthalpic content of the BECCS plant exhaust and implies that exhaust gas heat recovery may be an attractive option at higher rates of co-firing. It was found that there is the potential for the recovery of approximately 2.5 GJheat per tCO2 at a temperature of 100 °C from both PCC-BECCS and OCC-BECCS. On- and off-site applications for this recovered heat are discussed, considering boiler feedwater pre-heating, solvent regeneration and district heating cases.
Porter RTJ, Mahgerefteh H, Brown S, et al., 2016, Techno-economic assessment of CO2 quality effect on its storage and transport: CO(2)QUEST An overview of aims, objectives and main findings, International Journal of Greenhouse Gas Control, Vol: 54, Pages: 662-681, ISSN: 1750-5836
This paper provides an overview of the aims, objectives and the main findings of the CO2QUEST FP7 collaborative project, funded by the European Commission and designed to address the fundamentally important and urgent issues regarding the impact of the typical impurities in CO2 streams captured from fossil fuel power plants and other CO2 intensive industries on their safe and economic pipeline transportation and storage. The main features and results recorded from some of the unique test facilities constructed as part of the project are presented. These include an extensively instrumented realistic-scale test pipeline for conducting pipeline rupture and dispersion tests in China, an injection test facility in France to study the mobility of trace metallic elements contained in a CO2 stream following injection near a shallow-water qualifier and fluid/rock interactions and well integrity experiments conducted using a fully instrumented deep-well CO2/impurities injection test facility in Israel. The above, along with the various unique mathematical models developed, provide the fundamentally important tools needed to define impurity tolerance levels, mixing protocols and control measures for pipeline networks and storage infrastructure, thus contributing to the development of relevant standards for the safe design and economic operation of CCS.
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