| 1. |
- Òsk Gardarsdòttir, Stefanìa, 1987, et al.
(författare)
-
Improving the flexibility of coal-fired power generators: Impact on the composition of a cost-optimal electricity system
- 2018
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 209, s. 277-289
-
Tidskriftsartikel (refereegranskat)abstract
- A transformation of the electricity generation system is required to drastically reduce the associated CO2 emissions. In future systems, variable renewable energy sources (wind and solar) are expected to provide a significant fraction of the electricity supply, increasing the requirement for variation management compared with today´s situation. This paper investigates the impacts of measures designed to increase the competitiveness of coal-fired power plants in future energy systems, which are facing restrictions related to CO2 emissions and variable operation as a consequence of high penetration levels of wind and solar power. We investigate the cost-optimal compositions of three regional electricity generation systems with different conditions for generation using renewables with a linear cost-minimizing investment model. The model is applied in two energy policy scenarios: one with a tight cap on CO2 emissions, and one with a stringent requirement for generation from renewables. In a system with a stringent requirement for electricity generation from renewables but without a CO2 cap, coal-based technologies with improved cycling properties provide variation management, given that the development of measures for ensuring improved flexibility continues and reaches full-scale implementation at moderate cost. The effects of improved cycling properties on the system composition are especially relevant for regions with moderate potential for wind and solar generation, in that they reduce wind curtailment and improve the underlying conditions for investments in solar power. In the system with a tight CO2 cap, only coal-based technologies with Carbon Capture and Storage (CCS) and co-firing of biomass are feasible. Increasing the share of biomass in co-firing technologies to achieve negative CO2 emissions increases the competitiveness of these technologies to a greater extent than if simply the cycling properties are improved. A larger co-firing fraction reduces the total system costs, since it facilitates the provision of low-cost flexibility by Natural Gas Combined Cycle (NGCC) plants, and it is especially important in regions where nuclear power is otherwise cost-competitive, as low-cost flexibility stimulates investments in wind and solar power at the expense of nuclear power.
|
|
| 2. |
- Ali, Hassan, et al.
(författare)
-
Cost estimation of heat recovery networks for utilization of industrial excess heat for carbon dioxide absorption
- 2018
-
Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 74, s. 219-228
-
Tidskriftsartikel (refereegranskat)abstract
- The absorption of CO 2 using solvents (e.g., amines) is considered a state-of-the-art, albeit energy-intensive process for CO 2 capture. While it is generally recognized that the utilization of waste heat has potential to reduce the energy-associated costs for CO 2 capture, the cost of waste heat recovery is seldom quantified. In this work, the cost of heat-collecting steam networks for waste heat recovery for solvent regeneration is estimated. Two types of networks are applied to waste heat recovery from the flue gases of four process industries (cement, silicon, iron & steel, and pulp & paper) via a heat recovery steam generator (HRSG). A novel approach is presented that estimates the capital and operational expenditures for waste heat recovery from process industries. The results show that the overall cost (CAPEX + OPEX) of steam generated from one hot flue gas source is in the range of 1.1–4.1 €/t steam. The cost is sensitive to economic parameters, installation factors, the overall heat transfer coefficient, steam pressure, and to the complexity of the steam network. The cost of steam from an existing natural gas boiler is roughly 5–20-times higher than that of steam generated from recovered waste heat. The CAPEX required to collect the heat is the predominant factor in the cost of steam generation from waste heat. The major contributor to the CAPEX is the heat recovery steam generator, although the length of the steam pipeline (when heat is collected from two sources or over long distances) is also important for the CAPEX.
|
|
| 3. |
|
|
| 4. |
- Beiron, Johanna, 1992, et al.
(författare)
-
An assessment of the flexibility of combined heat and power plants in power systems with high shares of intermittent power sources
- 2018
-
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.
|
|
| 5. |
- Biermann, Max, 1989, et al.
(författare)
-
Evaluation of Steel Mills as Carbon Sinks
- 2018
-
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.
|
|
| 6. |
- Biermann, Max, 1989, et al.
(författare)
-
Partial Carbon Capture by Absorption Cycle for Reduced Specific Capture Cost
- 2018
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 57:45, s. 15411-15422
-
Tidskriftsartikel (refereegranskat)abstract
- For a sustainable-energy system, the industrial carbon emission should be zero or close to it. The partial capture of CO2, i.e., capturing only a share of the CO2, is discussed as an option for initiating the transition toward the decarbonization of industry by reducing the CO2 mitigation cost at industrial sites. This work models two approaches to achieving partial capture based on amine absorption: (1) capturing 90% CO2 from a split stream of the flue gas or (2) capturing less CO2 (≪90%) from the total flue-gas flow. A techno-economic analysis is carried out that considers scale, CO2 concentration, and process configurations (absorber intercooling and rich solvent splitting) when comparing the cost of partial capture to full capture, i.e., capturing close to all CO2 from the entire gas. Besides lowering absolute costs, the study shows that partial capture from CO2-rich gases may also lower specific cost (€ per tonne of CO2 captured) compared to full capture, despite the economy of scale, during certain market conditions. Operating expenditures, especially the cost of steam, are found to be dominating cost factors for partial capture, even for capture down to 200 000 tonnes per year.
|
|
| 7. |
- Edland, Rikard, 1990, et al.
(författare)
-
Modeling the Contributions of Volatile and Char-Bound Nitrogen to the Formation of NOx Species in Iron Ore Rotary Kilns
- 2018
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 32:2, s. 2321-2331
-
Tidskriftsartikel (refereegranskat)abstract
- Given that more stringent NO x emission limits are expected in the near future, several industrial processes are in need of NO x mitigation measures. The Grate-Kiln process, applied in the iron ore industry, is one such process. NO x formation is inherently high in the process, and due to the combustion conditions, several standard mitigation strategies are impractical. Alternative solutions are thus needed. The current paper aims at developing a model capable of describing the NO formation under conditions relevant in iron ore rotary kilns and to identify governing parameters that may be modified for mitigation purposes. The developed model uses detailed reaction modeling for the homogeneous combustion chemistry combined with simpler modeling with apparent kinetics for the heterogeneous chemistry. The main findings are that thermal NO is of low significance and that the NO formation during char combustion is the main contributor to the high NO x emissions. Attempting to control the partitioning between the volatile nitrogen and the char-bound nitrogen is suggested as a mitigation strategy, since the combustion of char is challenging to control compared to the combustion of volatiles.
|
|
| 8. |
- Edland, Rikard, 1990, et al.
(författare)
-
The connection between NOx and soot in oxygen-enriched propane flames
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Soot and nitrogen oxide are two harmful pollutants that are formed during combustion and strict emission legislation continues to motivate research on how they can be controlled. The current paper investigates how the formation of nitrogen oxide and soot is influenced by increasing the oxygen content in the oxidizer. Propane is combusted (80 kWth) applying oxygen-enriched air. In-flame measurement of temperature as well as soot and gas concentrations are performed with a combination of intrusive and non-intrusive equipment. The results show that increasing the oxygen content in the oxidizer from 21% to 27% increases the formation of nitrogen oxide while soot formation remains relatively low. At 30% however, soot formation increases by order of magnitudes and the emission of nitrogen oxide drops significantly. Detailed reaction modeling is performed and the shift in soot formation is captured by the model. Although the exact reason for the shift is not completely understood, the model shows that for a flame after the shift, soot inception initiates earlier in an environment where the concentration of acetylene and PAHs are relatively high, leading to fast surface growth. High temperatures in the early combustion sequence caused by higher oxygen content is believed to be the controlling factor, rather than the increased oxygen content itself.
|
|
| 9. |
- Edland, Rikard, 1990, et al.
(författare)
-
The formation of NOx and soot in oxygen-enriched suspension flames
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work discusses the formation of NOx and soot in propane flames and how the formation is influenced by the oxygen content in the oxidizer, both in oxy-fuel combustion and in oxygen-enriched air combustion. Experiments were conducted in the Chalmers 100 kW unit applying oxygen-enriched air and a continuous increase in NOx and soot formation was observed when the feed gas oxygen content was increased up to a specific value (around 30%); at that feed gas oxygen content the soot formation increased by order of magnitudes while the NOx emission decreased significantly, see Figure 1. A similar shift in flame characteristics was observed in oxy-fuel combustion but at a higher oxygen content (≈40%). This work aims to examine how NOx and soot chemistry relate and we discuss plausible explanations for the sudden change in the concentration of these two pollutants. According to the literature, there are three main chemical mechanisms by which soot and NOx may interact: 1) gas-phase interactions at a primary precursor level, involving competition for radicals as well as reactions of NOx with hydrocarbon radicals from primary aromatic precursors, 2) reactions of nitrogen included in the polycyclic aromatic hydrocarbon (PAH) clusters with simultaneous PAH-NO reduction or indirect influence of NOx on the PAH oxidation and growth processes, and, 3) heterogeneous interactions between soot particles and NOx through adsorption of NOx on the active sites in soot surface or through soot-catalyzed reactions. The present work is based on combustion modeling. Detailed reaction mechanisms, obtained from the literature, that are relevant to the gas phase nitrogen chemistry and soot formation during combustion in flames, were implemented to investigate possible interactions and their sensitivity to combustion conditions. Various cases were modelled, cases that are characterized by different reactor inlet oxygen concentrations, residence times, temperature conditions and mixing rates. The modeling results show that temperature and inlet oxygen concentration are important to the radical pool and, thus, to the rates of the key-reactions in soot and nitrogen oxide formation. An increasing soot formation in the flame region was observed when the local temperature and the inlet oxygen concentration were increased in the model. The observed NOx reduction is attributed mainly to competition for radicals on a precursor level and to heterogeneous reduction on the soot.
|
|
| 10. |
- Johansson, Jakob, 1990, et al.
(författare)
-
Gas-Phase Chemistry of the NO-SO2-ClO2 System Applied to Flue Gas Cleaning
- 2018
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 57:43, s. 14347-14354
-
Tidskriftsartikel (refereegranskat)abstract
- The chemical interactions that occur between NO, SO2, and ClO2 are investigated. In focus is the oxidation of NO with gaseous ClO2 for simultaneous removal of NOx and SOx from combustion-derived flue gases. Laboratory-scale experiments were conducted to examine the conversion of NO to NO2, under the following conditions: temperature range of 100-180 °C; H2O concentrations in the range of 0%-25%; ClO2-NO molar ratios in the range of 0.2-0.6; and NO and SO2 flue gas concentrations in the ranges of 0-250 ppm and 0-1000 ppm, respectively. The results show that NO is oxidized efficiently by ClO2, whereas the ClO2-SO2 reactions are insignificant. The water concentration had no effect on oxidation, and the temperature had a limited effect, within the investigated ranges. The outcomes favor the process economics of the studied application, since ClO2 consumption is negligible with respect to SO2 oxidation.
|
|
