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Title	Physical and Heat Transfer Modelling of a 200MW Thermal Corner Fired Boiler
Creator	Jenkins, B. G.; Bertrand, C.; Dhanjal, S. K.
Publisher	Digitized by J. Willard Marriott Library, University of Utah
Date	1989
Spatial Coverage	presented at Short Hills, New Jersey
Abstract	The effect of fuel changes on boiler performance and efficiency can be a major factor influencing the conversion potential of integrated process plant. Converting a 200MW corner fired water tube boiler from heavy fuel oil to natural gas can result in a 5-10% derating due to reduced radiant energy transfer, which would in turn reduce process capacity by a similar amount. As part of an assessment study to convert an alumina (Bayer Process) plant from heavy fuel oil to natural gas, an extensive physical and mathematical modelling project has been carried out to investigate and improve boiler performance to maintain MCR. A physical model of the boiler and associated ductwork has been used in both water and air modelling modes to equalize burner air distribution through the installation of air ductwork flow distributors, straightners etc; and to assess the effects of burner positions, angles, etc. on the radiant section aerodynamics. Results indicated an original maldistribution of air between individual burners of + 8%, which limits the boiler operation to 10-15% excess air conditions. By suitable air balancing the variation can be reduced to +2%, enabling 5% excess air condition to be achieved, with the attendant fuel savings that would ensue. The effects of burner angles on the radiant section aerodynamics can improve the heat transfer in the boiler by increased convection and gas residence time. Air modelling, to provide quantitative mass/momentum transfer data, together with a zone model matrix of 20 gas zones and 48 surface zones to simulate radiant and convective transfer, has been used to optimize the gas burner(s) design and position to give maximum radiant section efficiency in the boiler, and thus mitigate the effects of changing fuel. This novel, combined modelling approach to the study of new plant, and the conversion of existing plant is shown to be an inexpensive, reliable and important tool that can be used in combustion plant engineering design.
Type	Text
Format	application/pdf
Language	eng
Rights	This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
Conversion Specifications	Original scanned with Canon EOS-1Ds Mark II, 16.7 megapixel digital camera and saved as 400 ppi uncompressed TIFF, 16 bit depth.
Scanning Technician	Cliodhna Davis
ARK	ark:/87278/s6br8vrf
Setname	uu_afrc
ID	5787
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6br8vrf

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Title	Page 10
Format	application/pdf
OCR Text	Show 2.4 Discussion of Results When using model testing to investigate existing problems the initial model runs are made at conditions which simulate the current operation of the plant. This is necessary in order to establish the validity of the laboratory results by comparison with the site experience. The two types of physical modelling are used because each contributes to the knowledge of the boiler operation. The water bead modelling is used to create a visual image of the flow pattern in the combustion air ducting and combustion chamber whilst air modelling is used to obtain a quantitative value of the air velocities. The water bead modelling of the existing boiler showed very poor flO¥ distribution in the air inlet to the rotary element preheater and throughout the combustion air ducting. The results showed widely fluctuating and random flows which would be expected to result in poor air distribution between the burners and uneven flows within the burner itself. The air modelling tests confirmed that the air distribution between the burners was indeed poor with the flow through burner number 4 significantly lower than for the other three burners, with Burner 4 having only 80% of the flow through the other burners. Furthermore, the lower air register of burner 4 is particularly affected. Table 1 shows the measured deviations from mean flow in each of the four burner registers. During normal boiler operation, at 2-3% oxygen, Burner 4 will be extremely close to stoichiometric conditions and the lower oil gun/air register will be operating sub-stoichiometrically. Experience has shown tha t, even on large wa ter tube boilers (11), little fuel/air mixing takes place in the combustion chamber beyond the discreet burner flame. It would be expected, therefore, that No. 4 burner (especially the lower oil gun) would tend to produce considerable unburnt carbon. The majori ty of the fouling experienced wi th the air hea ter during the boiler operation probably originates from Burner No. 4. The modelling results imply that the boiler would be impossible to operate at its design excess air level of 3% at MeR for any extended period, since fouling would be a major problem.
Setname	uu_afrc
ID	5749
Reference URL	https://collections.lib.utah.edu/ark:/87278/s6br8vrf/5749