This perspective article aims to identify key research priorities to make the waste-to-energy sector compatible with the societal goals of circularity and carbon neutrality. These priorities range ...from fundamental research to process engineering innovations and socio-economic challenges. Three focus areas are highlighted: (i) the optimization of flue gas cleaning processes to minimize gaseous emissions and cross-media, (ii) the expansion of process control intelligence to meet targets for both material recovery and energy recovery, and (iii) climate neutrality, with the potential for negative emissions via the removal of atmospheric carbon dioxide across the full cycle of the waste resource. For each area, recent research trends and key aspects that are yet to be addressed are discussed.
In future energy supply systems, hydrogen and electricity may be generated in decarbonized industrial clusters using a common infrastructure for natural gas supply, electricity grid and transport and ...geological storage of CO2. The novel contribution of this article consists of using sequential combustion in a steam methane reforming (SMR) hydrogen plant to allow for capital and operating cost reduction by using a single post-combustion carbon capture system for both the hydrogen process and the combined cycle gas turbine (CCGT) power plant, plus appropriate integration for this new equipment combination. The concept would be widely applied to any post-combustion CO2 capture process. A newly developed, rigorous, gPROMs model of two hydrogen production technologies, covering a wide range of hydrogen production capacities, thermodynamically integrated with commercially available gas turbine engines quantifies the step change in thermal efficiency and hydrogen production efficiency. It includes a generic post-combustion capture technology – a conventional 30%wt MEA process - to quantify the reduction in size of CO2 absorber columns, the most capital intensive part of solvent-based capture systems. For a conventional SMR located downstream of an H-class gas turbine engine, followed by a three-pressure level HRSG and a capture plant with two absorbers, the integrated system produces ca. 696,400 Nm3/h of H2 with a net power output of 651 MWe at a net thermal efficiency of 38.9%LHV. This corresponds to 34 MWe of additional power, increasing efficiency by 4.9% points, and makes one absorber redundant compared to the equivalent non-integrated system producing the same volume of H2. For a dedicated gas heated reformer (GHR) located downstream of an aeroderivative gas turbine engine, followed by a two-pressure level HRSG and a capture plant with one absorber, the integrated system produces ca. 80,750 Nm3/h of H2 with a net power output of 73 MWe and a net thermal efficiency of 54.7%LHV. This corresponds to 13 MWe of additional power output, increasing efficiency by 13.5% points and also makes one absorber redundant. The article also presents new insights for the design and operation of reformers integrated with gas turbines and with CO2 capture.
A conceptual design assessment shows that the use of structured adsorbents in a regenerative adsorption wheel is technically feasible for the application of selective exhaust gas recirculation (SEGR) ...in combined cycle gas turbine (CCGT) power plants. As the adsorber rotates, CO
2
is selectively transferred from a flue gas stream to an ambient air stream fed to the gas turbine compressor, increasing the CO
2
concentration and reducing the flow rate of the fraction of the flue gases treated in a post-combustion CO
2
capture system. It imposes an estimated pressure drop of 0.25 kPa, unlike a pressure drop of 10 kPa reported for selective CO
2
membrane systems, preventing a significant derating of the gas turbine. An equilibrium model of a rotary adsorber with commercially available activated carbon evaluates the inventory of the adsorbent and sizes the wheel rotor. Two rotary wheels of 24 m diameter and 2 m length are required per gas turbine—heat recovery steam generator train to achieve an overall CO
2
capture level of 90% in a CCGT power plant (ca. 820 MW
e
) with SEGR “in parallel” to the capture plant. Two to five rotary wheels are required for a configuration with SEGR “in series” to the capture plant. A reduction of 50% in the mass of the adsorbent would be possible with Zeolite 13X instead of activated carbon, yet the hydrophilicity of zeolites are detrimental to the capacity and upstream dehydration of the flue gases is required. A parametric analysis of the equilibrium properties provides guidelines for adsorbent development. It suggests the importance of balancing the affinity for CO
2
to allow the regeneration of the adsorbent with air at near ambient pressure and temperature, to minimise the inventory of the adsorbent within practical limits. An adsorbent with a saturation capacity of 8 mol/kg, a heat of adsorption from 24 to 28 kJ/mol CO
2
and a pre-exponential factor of the equilibrium constant from 2 × 10
–6
to 9 × 10
–6
kPa
−1
would result in an inventory below 200 kg, i.e., approximately the limit for the use of a single rotary wheel system.
Increased consumption of low-carbon hydrogen is prominent in the decarbonisation strategies of many jurisdictions. Yet prior studies assessing the current most prevalent production method, steam ...reformation of natural gas (SRNG), have not sufficiently evaluated how process design decisions affect life cycle greenhouse gas (GHG) emissions. This techno-economic case study assesses cradle-to-gate emissions of hydrogen produced from SRNG with CO2 capture and storage (CCS) in British Columbia, Canada. Four process configurations with amine-based CCS using existing technology and novel process designs are evaluated. We find that cradle-to-gate GHG emission intensity ranges from 0.7 to 2.7 kgCO2e/kgH2 – significantly lower than previous studies of SRNG with CCS and similar to the range of published estimates for hydrogen produced from renewable-powered electrolysis. The levelized cost of hydrogen (LCOH) in this study (US$1.1–1.3/kgH2) is significantly lower than published estimates for renewable-powered electrolysis.
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•Techno-economic analysis of steam reforming natural gas with 76–99.9% CO2 capture.•Impact of process configuration and design choices using existing technology.•Cradle-to-gate greenhouse gas emission intensity of 0.7–2.7 kgCO2e/kgH2.•Levelised cost of hydrogen of US$1.1–1.3/kgH2.•Emission intensity comparable to electrolytic hydrogen at significantly lower cost.
To achieve a sustainable electricity grid, affordable and dispatchable power capacity that supports grid stability and does not increase atmospheric CO2 levels will be required. Combined cycle gas ...turbines (CCGTs) with post-combustion CO2 capture (PCC) can meet these requirements by capturing and permanently storing all combustion CO2 emissions and, coupled with negative emissions technologies, any remaining life-cycle emissions. For the first time, we present a comprehensive analysis of the technical and financial challenges of producing zero-carbon electricity from CCGTs on a life-cycle basis. We conclude that when the design is optimised, fossil CO2 capture fractions can be increased from 96% to 100% with minimal process modification, commercially available technology and an additional 0.5% decrease in thermal efficiency. This represents a significant 60–70% reduction in the additional efficiency penalty required to reach zero CO2 emission operation. The Cost of CO2 Avoided of 100% fossil CO2 capture is just 128 £/tCO2, a 3 £/tCO2 increase over the 95% gross CO2 capture fraction required to permit PCC projects in the UK. Indeed, within the bounds of the UK power CCS business model, we show that 100% fossil CO2 capture maximises both variable and capacity payments to the producer, resulting in a 2% decrease in the cost of power produced. For zero-carbon electricity on a life-cycle basis, the recapture and permanent geological storage of all remaining life-cycle CO2e emissions from plant construction & decommissioning, CO2 T&S network operation and the natural gas supply chain (operational CO2e emissions and methane leakage) increases the median Cost of CO2 Avoided to 178 £/tCO2 (130–371 £/tCO2), leading to the novel conclusion that a market mechanism equating to a CO2 price of over 178£/tCO2 is likely sufficient to incentivise the development of truly CO2-neutral CCGTs.
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•The CCA & LCOE for 100% fossil CO2 capture is estimated at 128£/tCO2 & 104 £/MWhe•Permanent scope 2 and 3 emission recapture adds 10–114£/MWhth to electricity costs.•The recapture of 8.6–11.8 MtCO2 of CO2 over the plant lifetime is required.•Electricity output penalty, capital and operational costs increase by 8, 4 and 2.3%.•CCS business models in the UK support 100% fossil CO2 capture.
•Process modelling of Waste to Energy plants with Post-combustion CO2 capture.•Key Performance Indicators of WtE CCS plants for different steam cycle configurations.•Design options for advanced heat ...integration in WtE CHP plants with CO2 capture.•Absorber design for ultra-high CO2 capture (>99 %) for amine-based CO2 capture.•Specific carbon intensity of WtE CCS plants, featuring different product bases.
Waste-to-Energy (WtE) is becoming an important application sector for carbon capture utilization and storage (CCS) due to its role in urban waste management and its inherent potential of achieving negative emissions. This study is built upon a series of modelling activities, with three representative WtE plant steam cycle configurations selected to integrate monoethanolamine (MEA) based Post-combustion CO2 Capture (PCC). With 60% biogenic carbon in the fuel, a set of key performance indicators of the investigated WtE plant configurations are presented. Results show that there is significant potential for heat recovery from the PCC process to provide heat for District Heating (DH). With advanced heat recovery, the energy utility factor (EUF) of WtE plant could be higher than that for WtE plant without PCC. Results also show that optimised process design can be used to enable ultra-high CO2 capture (99.72% in this study) to be achieved with only a marginal increase in specific reboiler duty when compared with 95% capture. This study also highlights the importance of differentiating carbon intensities for different product bases: electrical or thermal or waste, which are important when comparing WtE CCS with other carbon saving technologies. The findings of this study provide valuable information for the future implementation of carbon dioxide capture technology in the WtE sector.
•Allam Cycle process model with bypass stream heat source achieves 58.0% net efficiency.•Novel operational modes presented to enhance operational flexibility by using O2 storage to decouple O2 ...production from CO2 capture.•Case study of future GB electricity system with conventional and flexible Allam Cycles in bespoke Unit Commitment model.•Allam Cycle plants tend to operate as baseload due to competitive efficiency and minimal CO2 emissions.
The Allam Cycle is a novel oxy-combustion gas turbine power cycle with a reported net cycle efficiency of 58–60% LHV and near-zero operating emissions. An Allam Cycle process model is developed displaying a net cycle thermal efficiency (LHV) of 58.0%, a higher value than previously reported in the literature, due to the inclusion of a bypass stream heat source. Novel modes of operation are added to improve plant operational flexibility, including a temporary increase in cycle efficiency to 66.1%, with the use of liquid oxygen storage to shift the energy penalty of oxygen production. This facilitates decoupling oxygen and electricity production and operates as a form of energy storage. For the first time, a purpose-built Unit Commitment and Economic Dispatch (UCED) model is used to investigate the impact of Allam Cycle plants and of liquid oxygen storage on system costs and grid CO2 intensities, taking the illustrative case of the GB electricity system. Over a representative winter week with high net demand, a fleet of 5–15 Allam Cycle plants operates with a capacity factor of, respectively 97%-90%, reducing system costs by 2.6%–6.7% and reducing electricity grid average CO2 intensity by 7.9%–19.0%. Adding oxygen storage to these plants allows surplus renewable energy generation to be stored, thus avoiding wind curtailment. Our initial findings indicate that oxygen storage can be valuable to both to plant operators and the system operators, but also that further work is required to evaluate non-energy revenue streams from the ancillary service market to determine whether the capital expenditure of liquid oxygen storage could be justified without financial incentives.
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