| 1. |
- Wang, Chuan, et al.
(författare)
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Potential CO2 emission reduction for BF-BOF steelmaking based on optimised use of ferrous burden materials
- 2009
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836 .- 1878-0148. ; 3:1, s. 29-38
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Forskningsöversikt (refereegranskat)abstract
- Currently, the blast furnace (BF) to basic oxygen furnace (BOF) is the dominant steel production route in the steel industry. The direct CO2 emission in this process system exceeds 1 t of CO2/t of crude steel produced. Different ferrous burden materials, for instance iron ore and scrap, can be used in various proportions in this steelmaking route. This paper analyses how energy use, conversion costs, and CO2 emissions can be influenced by the use of different ferrous burden materials when producing crude steel. An optimisation mixed integer linear programming (MILP) model has been applied for analysis. By the use of the optimisation model, it is possible to highlight some issues of special importance, such as best practices to increase production at low conversion cost, or best practices to increase production at low CO2 emission. It is found out that more benefits will be gained when using the system-oriented analysis to the steelmaking process. Furthermore, a comprehensive view of the trade-offs between the objectives of Cost and CO2 can provide useful information for decision makers to generate strategies under the future emission trading. © 2008 Elsevier Ltd. All rights reserved.
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| 2. |
- Rydén, Magnus, 1975, et al.
(författare)
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Novel oxygen-carrier materials for chemical-looping combustion and chemical-looping reforming; LaxSr1─xFeyCo1─yO3─δ perovskites and mixed-metal oxides of NiO, Fe2O3 and Mn3O4
- 2008
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 2:1, s. 21-36
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Tidskriftsartikel (refereegranskat)abstract
- Solid oxygen-carrier materials for chemical-looping applications have been examined by reduction with CH4 and oxidation with air in a fixed-bed quartz reactor at 900ºC. Four perovskite materials, three metal-oxide materials and four metal-oxide mixtures have been studied. It was found that LaxSr1─xFeO3─δ perovskites provided very high selectivity towards CO/H2 and should be well suited for chemical-looping reforming. Substituting La for Sr was found to increase the oxygen capacity of these materials, but reduced the selectivity towards CO/H2 and the reactivity with CH4. La0.5Sr0.5Fe0.5Co0.5O3─δ was found to be feasible for chemical-looping combustion applications. NiO/MgAl2O4 propagated formation of solid carbon, likely due to the catalytic properties of metallic Ni. Fe2O3/MgAl2O4 had properties that made it interesting both for chemical-looping combustion and chemical-looping reforming. Adding 1% NiO particles to a bed of Fe2O3-particles increased both reactivity with CH4 and selectivity towards CO/H2 for reforming applications. Mn3O4/MgZrO2 was found to be suitable for chemical-looping combustion applications, but it could not be verified that adding NiO produced any positive effects.
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| 3. |
- Berguerand, Nicolas, 1978, et al.
(författare)
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The Use of Petroleum Coke as Fuel in a 10 kWth Chemical-Looping Combustor
- 2008
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 2:2, s. 11-179
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Tidskriftsartikel (refereegranskat)abstract
- Tests were made in a 10 kWth chemical-looping combustor with a petroleum coke as the solid fuel and the oxygen carrier ilmenite, an iron titanium oxide. The fuel reactor is fluidized by steam and the oxygen carrier reacts with the volatiles released as well as the gasification intermediates CO and H2. A constant fuel flow corresponding to a thermal power of 5.8 kW was introduced into the fuel reactor and a total of 11 h of operation was reached. The effects of particle circulation and carbon stripper operation on solid fuel conversion, conversion of gas from the fuel reactor and CO2 capture were investigated. The actual CO2 capture ranged between 60% and 75% while the solid fuel conversion was in the range 66 to 78%. The low values of solid fuel conversion reflect loss of char due to low efficiency of the fuel reactor cyclone. The incomplete conversion of the gas from the fuel reactor is expressed as oxygen demand. The oxygen demand corresponds to the fraction of oxygen lacking to achieve full gas conversion and was typically 25%, due to presence of CH4, CO and H2 from the fuel reactor. Typical ratios of CH4, CO and H2 over the total gaseous carbon from the fuel reactor are respectively 5, 10 and 25%. Low loss of non-combustible fines from the system indicates very low attrition of the oxygen carrier.
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| 4. |
- Bryngelsson, Mårten, et al.
(författare)
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The modelling of a hybrid combined cycle with pressurised fluidised bed combustion and CO2 capture
- 2009
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Ingår i: International journal of greenhouse gas control. - : Elsevier BV. - 1750-5836. ; 3:3, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy.
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| 5. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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160 hours of chemical-looping combustion in a 10 kW reactor system with a NiO-based oxygen carrier
- 2008
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 2:4, s. 520-530
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion, CLC, is a technology with inherent separation of the greenhousegas CO2. The technique uses an oxygen carrier made up of particulate metal oxide totransfer oxygen from combustion air to fuel. In this work, an oxygen carrier consisting of60% NiO and 40% NiAl2O4 was used in a 10 kW CLC reactor system for 160 h of operation withfuel. The first 3 h of fuel operation excepted, the test series was accomplished with the samebatch of oxygen carrier particles. The fuel used in the experiments was natural gas, and afuel conversion to CO2 of approximately 99% was accomplished. Combustion conditionswere very stable during the test period, except for the operation at sub-stoichiometricconditions. It was shown that the methane fraction in the fuel reactor exit gas wasdependent upon the rate of solids circulation, with higher circulation leading to moreunconverted methane. The carbon monoxide fraction was found to follow the thermodynamicalequilibrium for all investigated fuel reactor temperatures, 660–950C. Thermalanalysis of the fuel reactor at stable conditions enabled calculation of the particle circulationwhich was found to be approximately 4 kg/s, MW. The loss of fines, i.e. the amount ofelutriated oxygen carrier particles with diameter
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| 6. |
- Mahmoudkhani, Maryam, 1971, et al.
(författare)
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Low energy sodium hydroxide recovery for CO2 capture from atmospheric air – Thermodynamic analysis
- 2009
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 3:4, s. 376-384
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Tidskriftsartikel (refereegranskat)abstract
- To reduce the risks of climate change, atmospheric concentrations of greenhouse gases must be lowered.Direct capture of CO2 from ambient air, ‘‘air capture’’, might be one of the few methods capable of systematically managing dispersed emissions. The most commonly proposedmethod for air capture is a wet scrubbing technique which absorbs CO2 in an alkaline absorbent, i.e. sodium hydroxide producing an aqueous solution of sodium hydroxide and sodium carbonate. In most of the previous works it was assumed that the absorbent would be regenerated and CO2 liberated from the alkaline carbonatesolution using a lime and calcium carbonate causticization cycle. We describe a novel technique for recovering sodium hydroxide from an aqueous alkaline solution of sodium carbonate and present an end-to-end energy and exergy analysis. In the first step of the recovery process, anhydrous sodium carbonate is separated from the concentrated sodium hydroxide solution using a two-step precipitation and crystallization process. The anhydrous sodium carbonate is then causticized using sodium tri-titanate. The titanate direct causticization process has been of interest for the pulp and paper industry and has been tested at lab- and pilot-scale. In the causticization process, sodium hydroxide is regenerated and carbon dioxide is liberated as a pure stream, which is compressedfor use or disposal. The technique requires 50% less high-grade heat than conventional causticization and the maximum temperature required is reduced by at least 50 8C. This titanate cycle may allow a substantial reduction in the overall cost of direct air capture.
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| 7. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Chemical-looping with oxygen uncoupling for combustion of solid fuels
- 2009
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 3:1, s. 11-19
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping with oxygen uncoupling (CLOU) is a novel method to burn solid fuels ingas-phase oxygen without the need for an energy intensive air separation unit. The carbondioxide from the combustion is inherently separated from the rest of the flue gases. CLOU isbased on chemical-looping combustion (CLC) and involves three steps in two reactors, oneair reactor where a metal oxide captures oxygen from the combustion air (step 1), and a fuelreactor where the metal oxide releases oxygen in the gas-phase (step 2) and where this gasphaseoxygen reacts with a fuel (step 3). In other proposed schemes for using chemicalloopingcombustion of solid fuels there is a need for an intermediate gasification step of thechar with steam or carbon dioxide to form reactive gaseous compounds which then reactwith the oxygen carrier particles. The gasification of char with H2O and CO2 is inherentlyslow, resulting in slow overall rates of reaction. This slow gasification is avoided in theproposed process, since there is no intermediate gasification step needed and the charreacts directly with gas-phase oxygen. The process demands an oxygen carrier which hasthe ability to react with the oxygen in the combustion air in the air reactor but whichdecomposes to a reduced metal oxide and gas-phase oxygen in the fuel reactor. Three metaloxide systems with suitable thermodynamic properties have been identified, and a thermalanalysis has shown thatMn2O3/Mn3O4 and CuO/Cu2Ohave suitable thermodynamic properties,although Co3O4/CoO may also be a possibility. However, the latter system has thedisadvantage of an overall endothermic reaction in the fuel reactor. Results from batchlaboratory fluidized bed tests with CuO and a gaseous and solid fuel are presented. Thereaction rate of petroleum coke is approximately a factor 50 higher using CLOU in comparisonto the reaction rate of the same fuel with an iron-based oxygen carrier in normal CLC.
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| 8. |
- Odenberger, Mikael, 1977, et al.
(författare)
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Ramp-up of CO2 capture and storage within Europe
- 2008
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 2:4, s. 417-438
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the role of CO2 capture and storage (CCS) technologies as part of a portfolio for reducing CO2 emissions from the European electricity generation system until the year 2050. Special emphasis is put on the ramp-up of CCS with respect to timing of investments and requirement of corresponding CO2 transportation and storage infrastructure. The investigation comprises scenario analysis through modeling possible development of the electricity supply system for EU25 and together with a more detailed analysis of Northern Europe (Germany, UK, Denmark, Finland, Sweden and Norway). The modeling has been carried out with a techno-economic model (minimizing the system cost) including a detailed description of the present stationary European electricity generation system as obtained from the Chalmers Energy Infrastructure database.It is concluded that CCS can play a significant role in reducing CO2 emissions at a cost in the range of 20–60 €/t over the period studied. In EU25 as much as 39 Gt CO2 may be captured over the period 2020–2050 implying a steep ramp-up, i.e. most CCS capacity is added during the first two decades after 2020 from which it is assumed to be commercially available. Corresponding capture in Germany and UK amounts to 9 and 4 Gt, respectively. The analysis show that a transportation infrastructure can be put in place for about 2–5 €/t CO2. However, the steep ramp-up obtained from the model obviously do not take into account other issues which must be resolved for a large scale implementation of CCS. Examples of such issues are discussed in the paper and concern establishment of a legal framework regulating subsurface storage of CO2, inclusion of captured CO2 in the European Union emission trading scheme and issues related to fuel markets and fuel supply to accommodate an increased use of coal as a fuel.
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| 9. |
- Rydén, Magnus, 1975, et al.
(författare)
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Waste products from the steel industry with NiO as additive as oxygen carrier for chemical-looping combustion
- 2009
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 3:6, s. 693-703
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Tidskriftsartikel (refereegranskat)abstract
- Fe2O3-containing waste materials from the steel industry are proposed as oxygen carrier for chemical-looping combustion. Three such materials, red iron oxide, brown iron oxide and iron oxide scales, have been examined by oxidation and reduction experiments in a batch fluidized-bed reactor at temperatures between 800 and 950°C. NiO-based particles have been used as additive, in order to examine if it is possible to utilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactive combustion intermediates such as CO and H2. The experiments indicated modest reactivity between the waste materials and CH4, which was used as reducing gas. Adding small amounts of NiO-based particles to the sample increased the yield of CO2 in a standard experiment, typically by a factor of 1.5-3.5. The fraction of unconverted fuel typically was reduced by 70-90%. The conversion of CH4 to CO2 was 94% at best, corresponding to a combustion efficiency of 96%. This was achieved using a bed mass corresponding to 57 kg oxygen carrier per MW fuel, of which only 5 wt% was NiO-based synthetic particles. The different materials fared differently well during the experiments. Red iron oxide was fairly stable, while brown iron oxide was soft and subject to considerable erosion. Iron oxide scales experienced increased reactivity and porosity as function of the numbers of reduction cycles.
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