Publications
163 results found
Mechleri E, Staffell I, Lawal A, et al., 2016, Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes, 2016/07
This project focuses on performing an evaluation of process control strategies for normal and flexible operation conditions of CO2 post-combustion capture (PCC) processes. PCC is a promising, near-term technology for large-scale deployment for the decarbonisation of the power generation and other sectors. However, the integration of this technology imposes a well-known efficiency penalty on the power plant with which it is integrated. Once an optimal process design has been identified, this energy penalty can be somewhat reduced via application of an appropriate control strategy to the PCC plant. An appropriate process control strategy is also fundamental to guarantee the safety and feasibility of the process under flexible operating conditions that the power plants may be subject to.The aim of this project is to develop the process control strategy, to select appropriate control variables for a PCC process, and design efficient control structures for operation of a post-combustion capture process with minimum energy requirements for coal and natural gas power plants. The control structures are developed for power plant operating ranges of around 50% to 100% load.
Mechleri E, Rivotti P, Staffell I, et al., 2016, Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes
Mechleri E, Staffell I, Lawal A, Ramos A, Shah N, Mac Dowell Nclose, 2016, Evaluation of Process Control Strategies for Normal, Flexible and Upset Operation Conditions of CO2 Post Combustion Capture Processes, 2016/07
Mac Dowell N, Shah N, Staffell I, et al., 2016, Quantifying the Value of CCS for the Future ElectricitySystem, Energy & Environmental Science, Vol: 9, Pages: 2497-2510, ISSN: 1754-5706
Many studies have quantified the cost of Carbon Capture and Storage (CCS) power plants, butrelatively few discuss or appreciate the unique value this technology provides to the electricity system.CCS is routinely identified as a key factor in least-cost transitions to a low-carbon electricitysystem in 2050, one with significant value by providing dispatchable and low-carbon electricity.This paper investigates production, demand and stability characteristics of the current and futureelectricity system. We analyse the Carbon Intensity (CI) of electricity systems composed of unabatedthermal (coal and gas), abated (CCS), and wind power plants for different levels of windavailability with a view to quantifying the value to the system of different generation mixes. As athought experiment we consider the supply side of a UK-sized electricity system and compare theeffect of combining wind and CCS capacity with unabated thermal power plants. The resultingcapacity mix, system cost and CI are used to highlight the importance of differentiating betweenintermittent and firm low-carbon power generators. We observe that, in the absence of energystorage or demand side management, the deployment of intermittent renewable capacity cannotsignificantly displace unabated thermal power, and consequently can achieve only moderatereductions in overall CI. A system deploying sufficient wind capacity to meet peak demand canreduce CI from 0.78 tCO2/MWh, a level according to unabated fossil power generation, to 0.38tCO2/MWh. The deployment of CCS power plants displaces unabated thermal plants, and whilstit is more costly than unabated thermal plus wind, this system can achieve an overall CI of 0.1tCO2/MWh. The need to evaluate CCS using a systemic perspective in order to appreciate itsunique value is a core conclusion of this study.
Mechleri E, fennell P, Mac Dowell N, 2016, Flexible operation strategies for coal- and gas-CCS power stations under the UK and USA markets, 13th Greenhouse Gas Control Technologies (GHGT) conference
Alhajaj A, Mac Dowell N, Shah N, 2016, A techno-economic analysis of post-combustion CO2 capture and compression applied to a combined cycle gas turbine: Part II. Identifying the cost-optimal control and design variables, International Journal of Greenhouse Gas Control, Vol: 52, Pages: 331-343, ISSN: 1750-5836
A detailed optimization-orientated model of monoethanolamine-based CO2 capture plant and compression train in which all the technical and economic assumptions are defined and/or optimized was developed and used to simultaneously determine the cost optimal control and design variables including feed fraction ratio at different degrees of capture (DOC), which represents the amount of CO2 removed, for plant designs that partially bypass the CO2 capture process so as to achieve low to moderate reductions of CO2, but at lower overall cost. The effects of varying carbon prices on the levelized cost of CO2 capture and compression were also studied. The capture bypass option was observed to be the cost optimal choice for lower than 60% overall DOC. Carbon prices were observed to have a clear impact on the cost optimal DOC, with the cost-optimal DOC shifting from 70%–80% to 85%–90% at carbon prices of $4/tCO2to $23/tCO2 respectively. The study highlighted that if a suitably high carbon price does not materialize through a market mechanism, appropriate policies need to be put in place to achieve decarbonisation targets.
Adams T, Mac Dowell N, 2016, Off-design point modelling of a 420 MW CCGT power plant integrated with an amine-based post-combustion CO2 capture and compression process, Applied Energy, Vol: 178, Pages: 681-702, ISSN: 1872-9118
The use of natural gas for power generation is becoming increasingly important in many regions in the world. Given that the combined cycle gas turbine (CCGT) power stations are lower in capital cost and carbon intensity than their coal-fired counterparts, natural gas fired power stations are considered a vital part of the transition to a low carbon economy. However, CCGTs are not themselves “low carbon” and in order to reach a carbon intensity of less than 50 kgCO2/MWh, it will be necessary to decarbonise them via CCS, with post-combustion CCS currently regarded as being a promising technology for this application. In this study, we present a detailed model of a 420 MW triple-pressure reheat CCGT and evaluate its technical and economic performance under full and part load conditions. We evaluate the technical performance of our CCGT model by comparison to an equivalent model implemented in Thermoflow THERMOFLEX and observe agreement of power output and efficiency to within 4.1% and the temperature profile within the HRSG within 2.9%. We further integrate the CCGT with a dynamic model of an amine based CCS process, and observe a reduction in the base plant efficiency from 51.84% at full-load and 50.23% at 60% load by 8.64% points at full-load and 7.93% points at 60% load. A core conclusion of this paper is that CCGT power plants equipped with post-combustion CCS technologies are well suited to dynamic operation, as might be required in an energy system characterised by high penetrations of intermittent renewable power generation.
Heuberger CF, Staffell I, Shah N, et al., 2016, Levelised Value of Electricity - A Systemic Approach to Technology Valuation, 26th European Symposium on Computer Aided Process Engineering - ESCAPE 26
Budinis S, Krevor S, Mac Dowell N, et al., 2016, Can technology unlock unburnable carbon?
In 2015, the Conference Of the Parties in Paris (COP21) reached a universal agreement on climate change with the aim of limiting global warming to below 2 °C. In order to stay below 2 °C, the total amount of carbon dioxide (CO2) released, or ‘carbon budget’ must be less than 1,000 gigatonnes (Gt) of CO2. At the current emission rate, this budget will be eroded within the next thirty years. Meeting this target on a global scale is challenging and will require prompt and effective climate change mitigation action.The concept of ‘unburnable carbon’ emerged in 2011, and stems from theobservation 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 that is often overlooked. The positive contribution of CCS technology to 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 White 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.The paper includes an introduction to the key issues of carbon budgets and fossil fuel reserves, a detailed analysis of the current status of CCS technology, as well as a synthesis of a multi-model comparison study on global climate change mitigation strat
Mac Dowell N, 2016, About the size of it, TCE The Chemical Engineer, Pages: 27-30, ISSN: 0302-0797
Global anthropogenic CO2 production is vast, currently on the order of 35.5 Gt/yr or slightly > 910 million bbl/day of CO2. Due to serious environmental issues, the world has agreed to mitigate global warming and limit it to no more than 1.5°C above pre-industrial levels by the end of the century. One solution is the conversion of CO2 to useful products, e.g., fuels or plastics or otherwise use the CO2 in processes, e.g., CO2-EOR. This is broadly referred to as carbon capture utilization (CCU). The current scale of global CO2 utilization and the role of CCU option might play in mitigating climate change are discussed.
Mac Dowell N, Staffell I, 2016, The role of flexible CCS in the UK's future energy system, International Journal of Greenhouse Gas Control, Vol: 48, Pages: 327-344, ISSN: 1750-5836
That CCS will be required to operate in a flexible and load following fashion in the diverse energy landscape of the 21st century is well recognised. However, what is less well understood is how these plants will be dispatched at the unit generator scale, and what effect this will have on the performance and behaviour of the plant at the individual unit operation level. To address this gap, we couple an investment and unit commitment energy system model with a detailed plant-level model of a super-critical coal-fired power station integrated with an amine-based post-combustion CO2 capture process. We provide insight into the likely role of coal and gas CCS plants in the UK's energy system in the 2030s, 2040s and 2050s. We then evaluate the impact that this has on the performance of an individual coal CCS plant operating in this system, and chart its evolution throughout this period. Owing to the increased frequency and duration of part-load operation, asset utilisation and average efficiency suffer, leading to a substantially increased LCOE, implying that CCS costs will need to decrease more rapidly than is currently expected. Further, as a direct consequence of the dynamic operation, the interaction of the CCS plants with the downstream CO2 transport network is characterised by highly transient behaviour, including periods during which no CO2 is injected to the transport network, implying that the transport system must therefore be designed to incorporate this variability of supply.
Lozano FJ, Freire P, Guillen-Gozalbez G, et al., 2016, New perspectives for sustainable resource and energy use, management and transformation: approaches from green and sustainable chemistry and engineering, Journal of Cleaner Production, Vol: 118, Pages: 1-3, ISSN: 0959-6526
Alhajaj A, Mac Dowell N, Shah N, 2016, A techno-economic analysis of post-combustion CO2 capture and compression applied to a combined cycle gas turbine: Part I. A parametric study of the key technical performance indicators, International Journal of Greenhouse Gas Control, Vol: 44, Pages: 26-41, ISSN: 1750-5836
In order to mitigate significant capital expenditure and parasitic energy demands associated with post combustion capture plant, many studies focused on improving its performance and efficiency through improvement in the design, integration of utilities and selection of key operating parameters (KOPs) using various key performance indicators (KPIs). In this study, an equilibrium monoethanolamine-based CO2 capture plant and compression train model was developed, validated and then used to assess the effects of KOPs on the performance of the CO2 capture and compression process applied to a 400 MWe combined cycle gas turbine (CCGT) power plant in hot countries using selected non-monetized key economic and environmental performance indicators. These were selected so as to allow performance comparisons without resorting to economic assumptions (e.g., discount rates, costs of energy), which make such comparisons difficult. The results illustrate higher compression power and dramatic increase of cooling water requirements in coolers and washing water systems in hot countries. This work elucidates the complex compromise between minimizing capital and operating expenditure indicators, and environmental impacts. It highlights the importance of considering the whole process, as opposed to simply focusing on the energy penalty associated with solvent regeneration.
Hinchliffe S, van Diemen R, Heuberger C, et al., 2016, Transitions in Electricity Systems Towards 2030, Publisher: Institution of Chemical Engineers
Brown S, Mahgerefteh H, Martynov S, et al., 2015, A multi-source flow model for CCS pipeline transportation networks, International Journal of Greenhouse Gas Control, Vol: 43, Pages: 108-114, ISSN: 1750-5836
As part of the operation of the carbon capture and storage process, there are clear practical and economic incentives in employing an integrated pipeline network system involving the capture of CO2 from multiple emission sources such as power plants or steel works followed by injection into a single storage site. This paper presents the development and testing of multi-source flow model for predicting the entire flow conditions such as pressure, temperature, fluid phase and CO2 composition throughout the pipeline network and the delivery to the storage site. The model also accounts for pipeline elevation and periodic variations in feed source flow rate, for example as a result of the ramping up or ramping down of power production from coal fired power stations connected to the pipeline network. The ability to produce the above information is of vital importance given the large impact of the stream impurities on the CO2 phase behaviour and their physiochemical interactions with the pipeline material of construction, compressor power requirements and the storage reservoir performance.
Martynov S, Mac Dowell N, Brown S, et al., 2015, Assessment of Integral Thermo-Hydraulic Models for Pipeline Transportation of Dense-Phase and Supercritical CO<sub>2</sub>, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 54, Pages: 8587-8599, ISSN: 0888-5885
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- Citations: 7
Mechleri E, rivotti P, mac Dowell N, et al., 2015, Flexibility issues and controllability analysis of a post-combustion CO2 capture plant integrated with a natural gas power plant, 8th Trondheim Conference on CO2 Capture, Transport and Storage (TCCS-8)
Mac Dowell N, Shah N, 2015, The multi-period optimisation of an amine-based CO<sub>2</sub> capture process integrated with a super-critical coal-fired power station for flexible operation, COMPUTERS & CHEMICAL ENGINEERING, Vol: 74, Pages: 169-183, ISSN: 0098-1354
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- Citations: 79
Mehleri ED, Bhave A, Shah N, et al., 2015, Techno-economic assessment and environmental impacts of Mineral Carbonation of industrial wastes and other uses of carbon dioxide, Pages: 576-585
In this contribution, we present the results of an in-depth techno-economic analysis of some leading CO2 capture and utilisation (CCU) and conversion (CCC) options. Specifically, we consider CO2 conversion to methanol, formic acid and urea (CCC) in addition to mineral carbonation of industrial wastes (CCU). We compare the CCC and CCU options using a range of key performance indicators (KPIs), including 2nd law efficiency, CO2 avoided and tonneCo2/tonneproduct. The results indicate that CCU and CCC technologies are unlikely to provide a significant contribution to mitigating anthropogenic climate change. The primary bottleneck to industrial scale deployment of CCC technologies is likely to be the cost effective availability of low carbon-hydrogen in the case that the conversion option requires hydrogen. Further, we find that mineral carbonation may have niche applications in the context of industrial waste remediation but the large scale deployment of this technology as a substitute for the geological sequestration of CO2 is unlikely to be either cost effective or scalable. Moreover, although formic acid offers attractive economic profiles, we note that this process is at a lower TRL (TRL 4-5). Thus, we conclude that CCC and CCU technologies are only likely to be viable at scale in the event that substantial subsidies are available to offset the high costs associated with producing renewable hydrogen and the thermodynamic cost associated with processing such a stable molecule.
Mehleri ED, Mac Dowell N, Thornhill NF, 2015, Model Predictive Control of Post-Combustion CO<sub>2</sub> Capture Process integrated with a power plant, 12th International Symposium on Process Systems Engineering (PSE) / 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 161-166, ISSN: 1570-7946
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- Citations: 9
Buchard A, North M, Kozak C, et al., 2015, Atom efficiency in small molecule and macromolecule synthesis: general discussion, FARADAY DISCUSSIONS, Vol: 183, Pages: 97-123, ISSN: 1359-6640
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- Citations: 1
Akgul O, Mac Dowell N, Papageorgiou LG, et al., 2014, A mixed integer nonlinear programming (MINLP) supply chain optimisation framework for carbon negative electricity generation using biomass to energy with CCS (BECCS) in the UK, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 28, Pages: 189-202, ISSN: 1750-5836
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- Citations: 46
Mac Dowell N, Shah N, 2014, Dynamic modelling and analysis of a coal-fired power plant integrated with a novel split-flow configuration post-combustion CO₂ capture process, International Journal of Greenhouse Gas Control, Vol: 27, Pages: 103-119, ISSN: 1750-5836
We present a model of a coal-fired power plant integrated with a dynamic model of a monoethanolamine (MEA)-based post-combustion CO₂ capture process. We evaluate base- and part-load operating modes of the integrated power and CO₂ capture plant. We propose a simple modification to the base-process which exploits the tradeoff between thermodynamic and rate or kinetic driving forces for mass transfer. This modification returns a portion of the regenerated solvent to the middle of the absorption column at an elevated temperature. Under base-load operation of the power plant, this modification was observed to increase the degree of CO₂ capture by 9.9% and reduce the reboiler duty by 8.3%, improving the net electrical efficiency of the decarbonised power plant from 28.27% to 29.15% - a relative increase of 2.8%. Under part-load operation, the degree of CO₂ capture increased by 1% with a concurrent reduction in reboiler duty of 16.7% and an increase in overall process efficiency of 3.25%
Mac Dowell N, Llovell F, Sun N, et al., 2014, New Experimental Density Data and soft-SAFT Models of Alkylimidazolium ([CnC₁im](+)) Chloride (Cl-), Methylsulfate ([MeSO4](-)), and Dimethylphosphate ([Me2PO4](-)) Based Ionic Liquids, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 118, Pages: 6206-6221, ISSN: 1520-6106
Chen L, Sharifzadeh M, Mac Dowell N, et al., 2014, Inexpensive ionic liquids: [HSO₄]¯-based solvent production at bulk scale, Green Chemistry, Vol: 16, Pages: 3098-3106, ISSN: 1463-9262
Through more than two decades’ intensive research, ionic liquids (ILs) have exhibited significant potential in various areas of research at laboratory scales. This suggests that ILs-based industrial process development will attract increasing attention in the future. However, there is one core issue that stands in the way of commercialisation: the high cost of most laboratory-synthesized ILs will limit application to small-scale, specialized processes. In this work, we evaluate the economic feasibility of two ILs synthesized via acid–base neutralization using two scenarios for each: conventional and intensification processing. Based upon our initial models, we determined the cost price of each IL and compared the energy requirements of each process option. The cost prices of triethylammonium hydrogen sulfate and 1-methylimidazolium hydrogen sulfate are estimated as $1.24 kg−1 and $2.96–5.88 kg−1, respectively. This compares favourably with organic solvents such as acetone or ethyl acetate, which sell for $1.30–$1.40 kg−1. Moreover, the raw materials contribute the overwhelming majority of this cost and the intensified process using a compact plate reactor is more economical due to lower energy requirements. These results indicate that ionic liquids are not necessarily expensive, and therefore large-scale IL-based processes can become a commercial reality.
Boot-Handford ME, Abanades JC, Anthony EJ, et al., 2014, Carbon capture and storage update, Energy and Environmental Science, Vol: 7, Pages: 130-189, ISSN: 1754-5692
In recent years, Carbon Capture and Storage (Sequestration) (CCS) has been proposed as a potential method to allow the continued use of fossil-fuelled power stations whilst preventing emissions of CO2 from reaching the atmosphere. Gas, coal (and biomass)-fired power stations can respond to changes in demand more readily than many other sources of electricity production, hence the importance of retaining them as an option in the energy mix. Here, we review the leading CO2 capture technologies, available in the short and long term, and their technological maturity, before discussing CO2 transport and storage. Current pilot plants and demonstrations are highlighted, as is the importance of optimising the CCS system as a whole. Other topics briefly discussed include the viability of both the capture of CO2 from the air and CO2 reutilisation as climate change mitigation strategies. Finally, we discuss the economic and legal aspects of CCS.
Brown S, Martynov S, Mahgerefteh H, et al., 2014, CO<sub>2</sub>QUEST: Techno-economic assessment of CO<sub>2</sub> quality effect on its storage and transport, 12th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 2622-2629, ISSN: 1876-6102
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- Citations: 16
Mac Dowell N, Shah N, 2014, Optimisation of post-combustion CO<sub>2</sub> capture for flexible operation, 12th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 1525-1535, ISSN: 1876-6102
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- Citations: 29
Lucquiaud M, Fernandez ES, Chalmers H, et al., 2014, Enhanced operating flexibility and optimised off-design operation of coal plants with post-combustion capture, 12th International Conference on Greenhouse Gas Control Technologies (GHGT), Publisher: ELSEVIER SCIENCE BV, Pages: 7494-7507, ISSN: 1876-6102
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- Citations: 21
Mac Dowell N, Shah N, 2013, Identification of the cost-optimal degree of CO₂ capture: An optimisation study using dynamic process models, INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL, Vol: 13, Pages: 44-58, ISSN: 1750-5836
Mac Dowell N, Shah N, 2013, Dynamic modelling and analysis of a coal fired power plant integrated with post- Combustion CO<inf>2</inf> capture process, Pages: 12-13
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