| 25171. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
A fluidized-bed combustion process with inherent CO2 separation; application of chemical-looping combustion
- 2001
-
Ingår i: Chemical Engineering Science. - 0009-2509. ; 56:10, s. 3101-3113
-
Tidskriftsartikel (refereegranskat)abstract
- For combustion with CO2 capture, chemical-looping combustion has the advantage that no energy is lost for the separation of CO2. In chemical-looping combustion oxygen is transferred from the combustion air to the gaseous fuel by means of an oxygen carrier. The fuel and the combustion air are never mixed, and the gases from the oxidation of the fuel, CO2 and H2O, leave the system as a separate stream. The H2O can easily be removed by condensation and pure CO2 is obtained without any loss of energy for separation. This makes chemical-looping combustion a most interesting alternative to other CO2 separation schemes, which have the drawback of a large energy consumption. A design of a boiler with chemical-looping combustion is proposed. The system involves two interconnected fluidized beds, a high-velocity riser and a low-velocity bed. Metal oxide particles are used as oxygen carrier. The reactivities needed for oxygen carriers to be suitable for such a process are estimated and compared to available experimental data for particles of Fe2O3 and NiO. The data available on oxygen carriers, although limited, indicate that the process outlined should be feasible.
|
|
| 25172. |
|
|
| 25173. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Achieving Adequate Circulation in Chemical Looping Combustion─Design Proposal for a 200 MW th Chemical Looping Combustion Circulating Fluidized Bed Boiler
- 2022
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 36:17, s. 9588-9615
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) has unique potential for avoiding the large costs and energy penalties of existing CO2 capture technologies. Oxygen is transferred to the fuel using an oxygen carrier, thus avoiding contact between air and fuel. Consequently, the combustion products, CO2 and H2O, come in a separate stream, and more or less pure CO2 is obtained after condensation of H2O. CLC is normally conceived as a dual fluidized bed process, with high gas velocities in an air reactor driving the circulation, similar to circulating fluidized beds (CFBs), except that the material is led to a fuel reactor before being returned to the air reactor. Crucial for the process is the properties of the oxygen carrier and that circulation is sufficient to transfer needed oxygen and heat to the fuel reactor. Comprehensive literature shows successful use of many oxygen carriers in sustained pilot operation. In contrast, the need for reaching adequate circulation in an industrial-scale system has been given little consideration. Normally, a system similar to CFB boilers is assumed to give sufficient circulation. However, literature data indicate that circulation in CFB boilers is 5–50% of what is needed. Measures to provide sufficient circulation may cause difficulties, such as erosion or bed material loss in the cyclone. Here, a circulation system based on collection of the downflow of particles along the walls is proposed, and a design of a 200 MWth combined CLC–CFB boiler based on this principle is presented. Further, operational strategies and the need for flexibility are discussed. The design is focused on making an industrial-scale demonstration boiler, which can be used in CLC operation with different oxygen carriers and different fuels and that can explore different operational strategies to find optimal conditions. It is recommended that the upscaling of the technology aims directly at the industrial scale.
|
|
| 25174. |
- Lyngfelt, Anders, 1955
(författare)
-
Chemical looping combustion (CLC)
- 2013
-
Ingår i: Fluidized Bed Technologies for Near-Zero Emission Combustion and Gasification. - : Elsevier. - 9780857095411 ; , s. 895-930
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of the greenhouse gas CO2. The technology involves the use of a metal oxide as an oxygen carrier which transfers oxygen from combustion air to the fuel, and hence a direct contact between air and fuel is avoided. Two inter-connected fluidized beds, i.e. fuel reactor and air reactor, are used in the process. The outlet gas from the fuel reactor consists ideally of CO2 and H2O, and the latter is easily removed by condensation. This chapter presents the basic principles, gives an overview of oxygen-carrier materials and operational experiences, discusses the application to gaseous, liquid and solid fuels, and the use for combustion as well as for hydrogen production.
|
|
| 25175. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Chemical-Looping Combustion (CLC) of Solid Fuels (SF-CLC) A Discussion of Operational Experiences, Costs, Upscaling Strategies and Negative Emissions (Bio-CLC)
- 2018
-
Ingår i: GHGT 2018 - 14th International Conference on Greenhouse Gas Control Technologies.
-
Konferensbidrag (refereegranskat)abstract
- Chemical-Looping Combustion (CLC) is a technology which ideally is able to avoid all the costs associated with gas separation, well known to be the major cost, as well as the major reason for large loss in energy efficiency, of CO2 Capture and Storage (CCS). The reason is that the oxygen is transferred from air to fuel using an oxygen-carrier, thus avoiding the mixing of air and fuel, meaning that the combustion products, CO2 and H2O, end up in a separate stream. The H2O is easily removed by condensation resulting, ideally, in a pure CO2 stream. Furthermore, when applied to solid fuels a CLC boiler may be constructed very similar to a circulating fluidized bed (CFB) boiler, and analyses of the cost differences indicate a low added investment cost for a CLC boiler as compared to a CFB boiler. The CLC process has been operated in more than 39 smaller pilots, for a total of more than 10,000 h. The experience with solid fuels show a large variation in performance depending on pilot design, operational conditions, solids inventory, oxygen carrier and fuel. However, there is at present no experience of the process at commercial or semi-commercial scale, although oxygen-carrier materials have been successfully used in commercial boilers for a related process, Oxygen-Carrier Aided Combustion (OCAC) during more than 20,000 h of operation. The paper discusses the lessons learned from pilot operation, the costs, strategies for scale-up, as well as the use of CLC for biomass combustion, i.e. Bio-CLC, in order to attain negative CO2 emissions.
|
|
| 25176. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Chemical-Looping Combustion of Solid Fuels – Operational Experiences in 100 kW Dual Circulating Fluidized Bed System
- 2013
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 37, s. 608-617
-
Konferensbidrag (refereegranskat)abstract
- Results from the first year of operation of a 100 kW chemical-looping combustor for solid fuels arepresented. Gas measurements showed the presence of unconverted gas from the fuel reactor. Withbituminous coal the gas conversion was up to 84%, and significantly higher with low-volatile fuel andchar. The gas conversion was strongly dependent on solids inventory in the fuel reactor. A CO2 captureup to 98-99% was reached.The unit worked well and operation was stable. The operation shows the viability of this technology,which has unique potential for breakthrough in cost and energy penalty of CO2 capture.
|
|
| 25177. |
|
|
| 25178. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Chemical-looping combustion of solid fuels - Technology overview and recent operational results in 100 kW unit
- 2014
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 63, s. 98-112
-
Konferensbidrag (refereegranskat)abstract
- Chemical-looping combustion is a new combustion principle that uses metal oxides for oxygen transfer from air to fuel. Fuel is never mixed with combustion air and the combustion products, CO2 and steam, are recovered in a separate flow without gas separation. Thus, CO2 capture is inherent in the process and costs and energy penalties for gas separation are avoided. The paper includes: An overview of results from a 100-kW chemical-looping combustor for solid fuel. a discussion of technology scale-up and costs based on comparison to conventional circulating fluidizedbed boilers. The added cost for a CLC power plant, compared with a conventional CFB plant, should be in the range 12-27 €/tonne of CO2 avoided, and likely around 19-20 €/tonne.
|
|
| 25179. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Chemical-Looping Combustion of Solid Fuels – What is Needed to Reach Full-Scale?
- 2016
-
Ingår i: 4th International Conference on Chemical Looping, September 26-28, Nanjing, China.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Because the CO2 capture is inherent in chemical-looping combustion (CLC), thus ideally avoiding costly gas separation, this process has a potential for uniquely low costs of CO2 capture. So what is needed to get to the realization of this technology? The purpose of the paper is to discuss the status of the technology, barriers to the implementation of the technology, and also to suggest routes for the critical path from successful testing in small pilots to implementation in commercial-sized units. Thus, operational experiences with oxygen carriers and chemical-looping with solid fuels are discussed, as well as large scale design and important technology challenges. Moreover, possible routes to scale-up are suggested. One way of lowering the costs of intermediate scale-up steps is to build CLC plants without CO2 purification/compression and oxygen production, because CO2 capture normally only makes sense in large scale. Another way to avoid or minimize the cost of the air reactor, would be by using a CFBB (circulating fluidized bed boiler) as the air reactor. This could either be an existing CFBB which is not in operation or can be taken out of operation for a period, or a designed dual purpose air reactor/CFBB where the CFBB can be used as a stand-alone unit after the testing period with CLC.
|
|
| 25180. |
- Lyngfelt, Anders, 1955, et al.
(författare)
-
Chemical-looping combustion - status of development
- 2008
-
Ingår i: 9th International Conference on Circulating Fluidized Beds May 13 - May 16, Hamburg 2008.
-
Konferensbidrag (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a combustion technology with inherentseparation of the greenhouse gas CO2. The technique involves the use of a metal oxide as anoxygen carrier which transfers oxygen from combustion air to the fuel, and hence a directcontact between air and fuel is avoided. Two inter-connected fluidized beds, a fuel reactor andan air reactor, are used in the process. In the fuel reactor, the metal oxide is reduced by thereaction with the fuel and in the air reactor; the reduced metal oxide is oxidized with air. Theoutlet gas from the fuel reactor consists of CO2 and H2O, and almost pure stream of CO2 isobtained when water is condensed. Considerable research has been conducted on CLC in thelast years with respect to oxygen carrier development, reactor design, system efficiencies andprototype testing. In 2002 the process was a paper concept, albeit with some important butlimited laboratory work on oxygen carrier particles. Today more than 600 materials have beentested and the technique has been successfully demonstrated in chemical-looping combustors inthe size range 0.3 – 50 kW, using different types of oxygen carriers based on the metals Ni, Co,Fe, Cu and Mn. The total time of operational experience is more than a thousand hours. Fromthese tests it can be established that almost complete conversion of the fuel can be obtained and100% CO2 capture is possible. Most work so far has been focused on gaseous fuels, but thedirect application to solid fuels is also being studied. Moreover, the same principle of oxygentransfer is used in chemical-looping reforming (CLR), which involves technologies to producehydrogen with inherent CO2 capture. This paper presents an overview of the research performedon CLC and CLR highlights the current status of the technology.
|
|
