| 23531. |
- Leckner, Bo G, 1936, et al.
(författare)
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Nitrogen Oxides Emissions from Fluidized Bed Combustion of Different Fuels
- 1990
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Ingår i: Proceedings of the 2nd Topic Oriented Technical Meeting held in May 1990 in Rueil Malmaison, France.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The emission of NO from FB boilers depends largely on design and operation parameters. However, the content of fuel volatiles do play a role which can be qualitatively described. Until more kinetic data for all the different materials in the bed and catalytic reactions are available a thorough kinetic investigation in the laboratory is necessary before quantative modelling of the fuel nitrogen in a given fluidized bed combustor is possible. A step in this direction has been taken.
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| 23532. |
- Leckner, Bo G, 1936
(författare)
-
On the Regimes of Fluidized Beds for Solid Fuel Conversion
- 2012
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Ingår i: 18th Fluidization & Particle Processing Symposium, The Society of Chemical Engineers, Japan (SCEJ).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Much work has been presented on the regimes of fluidization of Group A particles in chemical reactors, and this area is rather well known. However, the description of the fluidization behaviour of Group B particles at high fluidization velocities in wide vessels is more ambiguous. Bubbling, turbulent, and fast fluidization regimes are analysed here, especially related to boilers. It is found that the bottom bed of boilers is operated in a bubbling regime even at high gas velocities, accompanied by a tall splash zone, as long as there is sufficient bed material in the system. It is shown that conventional circulating fluidized bed boilers operate in a dilute suspension mode. Also for denser flows, a comparison between transport velocity and terminal velocity indicates that clustering flow is much stronger for Group A particles than for Group B. The bottom bed and its mode of fluidization have implications for the modelling of a furnace.
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| 23533. |
- Leckner, Bo G, 1936, et al.
(författare)
-
Operational results from the 16 MW FBB at the Chalmers University
- 1984
-
Ingår i: 3rd International Conference of the Institue of Energy. ; , s. DISC/16/134-143
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Konferensbidrag (refereegranskat)abstract
- The 16 MW fluidised bed boiler was first started in 1982 and has since then run for 3325 hours. After only 1200 hours the material wastage on the in-bed heat transfer surfaces was so great that tubes had to be removed. Wear resistant coatings of various kinds have been tried but the result of their use is not quite clear. Measurements of elutriated solids and the corresponding combustion efficiency is discussed. Finally, in contrast to the problems of material wastage and low combustion efficiency, some positive operational characteristics such as start-up and load control are presented.
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| 23534. |
- Leckner, Bo G, 1936
(författare)
-
Optimization of emissions from fluidized bed boilers
- 1992
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Ingår i: International Journal of Energy Research. - 1099-114X .- 0363-907X. ; 16:5, s. 351-363
-
Tidskriftsartikel (refereegranskat)abstract
- The experiences of emissions of SO,, NO, and N,O from fluidized bed boilers obtained from extensive measurements by the Department of Energy Conversion, Chalmers University of Technology, are briefly summarized. In addition, results from secondary methods to reduce NO and N,O emissions are shown. With this background, possibilities for decreasing the N,O emissions by the optimization of boiler parameters involving the use of secondary methods are discussed. The problem lies in the increase in the SOz and NO emissions when a measure is taken to reduce the N,O emission. In particular, the influence of excess air and temperature is considered in comparison with selective noncatalytic reduction of NO.
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| 23535. |
- Leckner, Bo G, 1936, et al.
(författare)
-
Oxy-fuel combustion in circulating fluidized bed boilers
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 125, s. 308-318
-
Tidskriftsartikel (refereegranskat)abstract
- The conditions for CO2 reduction in a circulating fluidized bed (CFB) oxy-boiler are studied, that is, operationwith pure oxygen, diluted by recirculated flue gases to moderate the combustion process. Two casesare analyzed: the ready-to-convert case, a normal air-fired CFB boiler, only slightly modified to be operatedwith oxygen instead of air for CO2 capture, and a more general option, an entirely new design,employing high oxygen concentration in the input to the oxy-fuel CFB boiler. It is found that at a givenfuel load, the relevant parameters for maintaining the CFB performance (bed temperature and fluidizationvelocity) in the ready-to-convert case cannot be kept entirely equal to those in the air-fired case,and some compromise has to be found. The new-design case results in a smaller boiler than that ofthe comparable air-fired case, depending on the oxygen concentration and the corresponding flue-gasrecirculation. This case is expected to contribute favorably to reduction of the cost of CO2 removal.
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| 23536. |
- Leckner, Bo G, 1936, et al.
(författare)
-
Primary Measures to Reduce the Emissions of Nitrogen Oxide in Circulating Fluidized Bed Boilers
- 1987
-
Ingår i: In proceedings of the Swedish Flame Days held 8-9 September 1987 in Studsvik, Sweden.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During the combustion of coal in a circulating fluidized bed boiler the conversion of the fuelbond nitrogen to either nitrogen oxides or nitrogen can be influenced by design and operational measures. The paper gives a summary of results obtained in a series of tests on a 40 MW circulating fluidized bed boiler in Nykoping, designed by Gotaverken Energy. In this commercial boiler it was not possible to study the influence of primary to secondary air addition independent of thebed temperature. For this reason, a smaller boiler designed by the same manufacturer was adapted to permit independent variations of the primary air ratio and the bed temperature. The results from the 40 MW and the 8 MW boilers are compared and the influence of the distribution of the air supply and of the bed temperature on the reduction of nitrogen oxide emissions are discussed.
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| 23537. |
- Leckner, Bo G, 1936
(författare)
-
Process aspects in combustion and gasification Waste-to-Energy (WtE)
- 2015
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 37, s. 13-25
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Tidskriftsartikel (refereegranskat)abstract
- The utilisation of energy in waste, Waste to Energy (WtE), has become increasingly important. Waste is awide concept, and to focus, the feedstock dealt with here is mostly municipal solid waste. It is found thatcombustion in grate-fired furnaces is by far the most common mode of fuel conversion compared tofluidized beds and rotary furnaces. Combinations of pyrolysis in rotary furnace or gasification in fluidizedor fixed bed with high-temperature combustion are applied particularly in Japan in systems whosepurpose is to melt ashes and destroy dioxins. Recently, also in Japan more emphasis is put on WtE. Incountries with high heat demand, WtE in the form of heat and power can be quite efficient even in simplegrate-fired systems, whereas in warm regions only electricity is generated, and for this product theefficiency of boilers (the steam data) is limited by corrosion from the flue gas. However, combinationof cleaned gas from gasification with combustion provides a means to enhance the efficiency of electricityproduction considerably. Finally, the impact of sorting on the properties of the waste to be fed to boilersor gasifiers is discussed. The description intends to be general, but examples are mostly taken fromEurope.
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| 23538. |
- Leckner, Bo G, 1936
(författare)
-
Radiation from flames and gases in a cold wall combustion chamber
- 1970
-
Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 13:1, s. 185-197
-
Tidskriftsartikel (refereegranskat)abstract
- The calculation of heat transfer in furnaces is usually based on coarse approximations of temperatureand emissivity in the combustion chamber. This paper suggests a method suitable for machinecomputation of the heat transfer from flames and gases to the walls of a furnace. A theoretical derivationof the basic equation is made and the simplifications necessary for execution of the calculation in acceptabletime are discussed The patterns of temperature and flame. emissivity are described by means of simplefunctions, a mathematical model. Experiments were carried out in an experimental furnace of simplegeometry using one oil-burner in order to check the accuracy of the theoretical assumptions. Mcasurementsof flame and gas temperature, flame emissivity, wall heat flux and exterior measurements necessaryfor the heat balance of the furnace were done. The measurements of temperature and emissivity define themathematical model.The heat transfer from flame and gases (including the contribution due to reflexion, non-cold surfacesand convection) was calculated at four different loads of the furnace and compared with the heat fluxmeasurements. The difference between measured and calculated heat flux, due to errors of measurementsand calculations, was less than about 15 per cent of the total heat flux.
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| 23539. |
- Leckner, Bo G, 1936
(författare)
-
Radiative heat transfer calculations in real gases
- 1974
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Ingår i: Waerme-Stoffuebertrag Thermo-Fluid Dyn. - 0042-9929 .- 1432-1181. ; 70:4, s. 236-247
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Tidskriftsartikel (refereegranskat)abstract
- A general formulation for radiative heat transfercalculations is presented, based on integrated quantities such as total emissivities and absorptivities. The procedure is intended particularly for combustion chamber applications of varEing degree of complexity, the radiative active medium consisting of gases such as H20 and CO2 and of soot. First, some preliminary calculations are given for the often treated radiative equilibrium cases of plane parallel plates and infinite concentric cylinders. Then an example of a combustion chamber calculation is studied where the radiative heat transfer calculation is included in a system of partial differential equations describing momentum, hear and mass transfer with combustion.
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| 23540. |
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