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- Andersson, Klas, 1977, et al.
(författare)
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Experiments and modeling on oxy-fuel combustion chemistry during lignite-firing
- 2007
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Ingår i: The Proceedings of the 32nd International Technical Conference on Coal Utilization & Fuel Systems, Clearwater, USA, 2007.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents experimental and modeling work on the combustion chemistry of the oxy-fuel(O2/CO2 recycle) process with focus on the difference in NO formation between oxy-fuel and air-firedconditions. Measurements have been carried out in a 100 kW test unit, which facilitates oxy-fuelcombustion with real flue gas recycle. These measurements include in-furnace gas concentrations andtemperature profiles from lignite-fired tests. The tests comprise a reference test in air and three oxy-fuel test cases with different oxygen fractions in the recycled feed gas. Additional oxy-fuelexperiments were performed in order to study the sensitivity of the NO formation to bothstoichiometry and air ingress.The results show that for the burner settings used in this work, lignite oxy-combustion with a globaloxygen fraction of 25 vol % in the feed gas results in flame temperature levels close to those duringair-firing. Similar to previous work, it is seen that the NO emission levels in [mg/MJ] during oxy-fueloperation are reduced to less than 30 % of the emission level during air-fired conditions. The resultsfrom the modeling shows that the reduction of NO emissions during oxy-fuel combustion is caused byan increased destruction of formed and recycled NO. Further experimental tests on the OF 27condition show that an increased stoichiometric ratio (from l = 1.18 to 1.41) as well as an increasedN2 content in the feed gas (from about 1% to 15%) only has a small effect on the NO formation duringoxy-combustion.
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- Beiron, Johanna, 1992, et al.
(författare)
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An assessment of the flexibility of combined heat and power plants in power systems with high shares of intermittent power sources
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is an urgent need to reduce anthropogenic CO2 emissions from the power sector as a climate change mitigating strategy. Thus, the share of renewable energy sources in power systems, for example wind power, is increasing. However, the variability in wind power generation poses a challenge to conventional thermal power plants, as well as yielding volatile electricity prices. Once in place, wind power with low operating cost will replace higher-cost electricity generation units in the merit order, while during low-wind periods the need for thermal plants remains. Traditionally designed for stable base load, thermal power plants might thus face a future with new demands for flexible operation to stay competitive. Combined heat and power (CHP) plants are thermal power plants that produce electricity and district heating simultaneously and, depending on plant type and fuel, they have different possibilities to vary the ratio between power and heat production. However, technical constraints place limitations on flexibility, including ramp rates and efficiency. The interconnection between the power and heat markets provides additional opportunities for load variation management. With the comparably slower dynamics of the heat market, and the possibility to store thermal energy, prospects of adapting to new and profitable operating strategies that can aid the balancing of the power system arise. This study focuses on how CHP plants can provide flexibility in a scenario with fluctuating power demand and associated volatility in electricity prices. Plant and market dynamics are analyzed to estimate the need for flexibility, and what is required of CHP units in terms of operation to meet these requirements. A CHP plant is modelled in detail with a boiler, steam cycle and its link to the district heating system, both under steady state and transient conditions, using the softwares Ebsilon and Dymola, respectively. The models are validated against operational data from a Swedish CHP plant. Transient responses to load ramps are characterized, as well as the flexibility in power-to-heat ratio, and their effects on efficiency.
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- Biermann, Max, 1989, et al.
(författare)
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Efficient utilization of industrial excess heat for carbon capture and district heating
- 2020
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Carbon capture and storage (CCS) from fossil and biogenic (BECCS) emission sources is necessary to limit global warming to well below 2°C. The EU as well as Swedish national agencies emphasize the importance of CCS for emission intensive industries. However, the cost of implementing CCS is currently still higher than the cost of emitting CO2 via the EU ETS, for example. To incentivize rapid deployment of CCS, the concept of partial capture has been suggested, i.e. capturing only a fraction of the site emissions to reduce capture cost. Several studies have found that the utilization of excess heat from industrial processes could significantly reduce the capture cost as the heat required (~120°C) may be available in significant quantities. However, available excess heat will not be sufficient to power full capture at most industrial sites. In Sweden, many industries utilize all or part of their excess heat in heat recovery units or in combined heat and power (CHP) plants to produce electricity and deliver heat to municipal district heating (MDH) systems. A broad implementation of CCS will, thus, effect the availability of excess heat for industrial heat and power generation. The future product portfolio of industrial processes with excess heat export and CHP plants can therefore be expected to include not only heat and power production, but also climate services (CCS/BECCS) and grid services (frequency regulation due to intermittent renewables). The aim of this work is to assess partial capture at sites that have access to low-value excess heat to power the capture process, whilst considering competition from using the excess heat for MDH delivery. The work is based on process modelling and cost estimation of CO2 capture processes using amine absorption for two illustrative case studies, a refinery and a steel mill, which both currently use excess heat for MDH. The main focus is on investigating how seasonal variations in the availability of excess heat as well as the demand of district heating impact cost-efficient design and operation of partial capture at industrial sites. A challenge when utilizing excess heat in connection to a process connected to a district heating system is that the heat source which can be used to power part of the capture process will exhibit seasonal availability, and thus may inflict extra cost for the CCS plant not running at full load, and therefore may counteract the economic motivation for partial capture. To prevent this, heat integration between CCS and municipal district heating is investigated, for example by utilizing heat from the CO2 compression so that low-pressure steam is released from MDH to provide heat to capture CO2 whilst maintaining MDH supply. The design of the amine absorption capture process will have to handle significant load changes and still maintain high separation efficiency within hydrodynamic boundaries of the absorber and stripper columns. The cost of such operation will depend on the solvent circulation flows, the number of absorber columns (including packing and liquid collectors/distributors) and capacity of solvent buffer tanks for storing unused solvent during the winter season. Assuming that a constant amount of CO2 is avoided, the avoidance cost of CCS based on excess heat with seasonal heat load variations is compared to the avoidance cost of CCS based on the use of external fuel to achieve a constant heat load to the reboiler.
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- Biermann, Max, 1989, et al.
(författare)
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Evaluation of Steel Mills as Carbon Sinks
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The iron and steel industry is one of the industries with the largest global contribution to CO2 emissions. Possible mitigation options include use of biomass and carbon capture and storage. Combining these two mitigation options, this study evaluates the potential for BECCS at an integrated steel mill in Sweden. The injection of pulverized biocoal from torrefaction or pyrolysis into a blast furnace and CO2 capture by amine absorption of the blast furnace gas leaving at the top of the furnace can reduce CO2 site emissions by up to 61 %, when accounting for negative emissions (biogenic CO2 being captured). The mitigation cost are estimated to 43 – 100 € per tonne CO2 avoided, depending primarily on biomass prices and the share of biomass used in the process (the study assumes a cost effective capture rate of 84%). Besides a reduction in CO2 emissions, the study highlights the potential for green by-products from injecting biogenic carbon into the blast furnace in the form of renewable electricity and CO2 neutral steel. The study concludes that it is theoretically possible to reach carbon neutrality or even net-negative emissions in an integrated steel mill, but this would require considerable process changes and high demand of biomass. Nonetheless, the implementation of BECCS based on feasible biomass injection volumes in integrated steel mills is interesting as a near-term and possibly cost-effective option for CO2 mitigation.
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- Biermann, Max, 1989, et al.
(författare)
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Scenario for near-term implementation of partial capture from blast furnace gases in Swedish steel industry
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Iron-and-steel making is a carbon-intensive industry and responsible for about 8% of global CO2 emissions. Meeting CO2 reduction targets is challenging, since carbon is inherent in the dominating production route in blast furnaces. Long-term plans to phase out carbon and change production technique are under way, such as iron ore reduction with hydrogen[1][2] won from renewable energies or electro winning[3], however unlikely to be implemented at scale before 2040 [4]. Until a transition to such technologies is completed, carbon leakage will remain to be a threat to steel industry inside EU ETS system. CCS remains an option for steel industry to comply with reduction targets and meet rising allowance (EUA) prices, currently above 20 €/t. Most studies on CCS propose a capture rate of ≥ 90 %[5–7], however, CCS could be considered as a part of a series of measures (e.g. fuel change, energy efficiency measures) that together achieve a significant reduction in CO2 emissions until a carbon-neutral production is in place. This line of thought motivates the concept of partial capture, where only the most cost effective part of the CO2 emissions are separated for storage [8]. In steel industry, high CO2 concentrations at large flows and the availability of excess heat make partial capture attractive. Previous work on the steel mill in Luleå, Sweden, emits around 3.1 Mt CO2 per year, has found that 40-45 % of site emissions can be captured fueled by excess heat alone[9]. Therein, five heat recovery technologies were assessed, ranging from back pressure operation of CHP turbine to dry slag granulation. Promising CO2 sources on site include flue gases from hot stoves and the combined-heat and power plant, and the process gas originating from the blast furnace – blast furnace gas (BFG). BFG is a pressurized, low value fuel used for heating on site. CO2 separation from BFG requires less reboiler heat for MEA regeneration, and the enhanced heating value of the CO2 lean BFG increases energy efficiency of the steel mill [9]. This work discusses the near-term (the 2020s) implementation of partial capture at a Swedish steel mill and the economic viability of such implementation dependent on the energy price, carbon price, and required reductions in CO2 emissions. Based on previous work [9][10,11] on partial capture in steel industry a cost estimation of a capture system for the BFG is conducted including CAPEX and OPEX of the MEA capture unit, gas piping, and recovering heat from the steel mill. The costs are summarized as equivalent annualized capture cost (EAC) and set into relation to transport and storage costs as well as carbon emission costs to form the net abatement cost (NAC) according to Eq. (1) ???=???+ ?????????&??????? ???? −?????? ????? [€/???2] (1) Figure 1 shows how EAC for BFG varies with the capture rate and the cost of steam for different heat recovery technologies represented by the steps in the curve ( see explanation in [9]). Note that partial capture from BFG is more economical than the full capture benchmark. The most cost-efficient case of 28 €/t CO2 captured is achieved for BFG capture fueled by steam from back-pressure operation (at the expense of electricity production), flue gas heat recovery and flare gas combustion. The transport and storage cost applied in Eq (1) represent ship transport from the Bothnian Bay to a storage site in the Baltic Sea , according to Kjärstad et el.[12]. Transport and storage cost range within 17 – 27 €/t CO2 depending on scale. These installation and operation cost for capture, transport and storage are set into relation with various scenarios on future carbon and energy (electricity) prices in Europe and Sweden. For example, Figure 2 illustrates a scenario in line with IEA’s sustainable development scenario to restrict global warming to 2°C. The carbon prices are adapted from WEO 2018 [13] and increase from 20 € to 120 € per tonne CO2 by 2040 and the electricity prices of 42-52 €/MWh (increasing with time) are based on latest results from the NEPP project [14]. In this scenario, partial capture from BFG could become economic viable in 2029, construction in 2020 with operation from 2022/23 onwards is likely to pay off within a lifetime of 20 years only. This work demonstrates the viability of partial capture as cost-efficient mitigation measure for the steel industry and illustrates conditions for an early implementation in the 2020s. This work is part of the CO2stCap project (Cutting Cost of CO2 Capture in Process Industry) and funded by Gassnova (CLIMIT programme), the Swedish Energy Agency, and industry partners.
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