Anaerobic Digestion, conr The enclosed flare systems also use sup plemental natural gas to give the re quired temperatures. Destruction effici encies between the two systems vary because of the residence time in the burner.
The new style open burner destruc tion efficiency is approximately 90% at its rated gas flow volume as compared to 99.999% in the enclosed flare. As
of waste gas may be required. As a re sult, the incinerator can sit for periods of time at ambient outside air tempera tures. When it is necessary to fire the burner at low air temperatures, the in cinerator temperature is raised very rap
ries. Other concerns relate to the con
siderably higher initial cost of the equip ment and to the potentially higher oper ating cost as it relates to use of pilot gas. Intermittent Operation The enclosed flare is constructed from two dissimilar materials which
idly from 0°C or lower temperatures to 900''C. The thermal properties of dif ferential expansion between the ceramic
have broadly varying operating proper ties at high temperatures. The outer steel shell provides environmental protection and support for the inner thermal shell
liner and the outer steel shell can lead
to stresses on the connection system
can be seen, the open flare burner does not meet the 98% destruction efficiency on its own. More recent testing has shown that efficiency in the open flare burner can be improved by reducing the gas flow rate through the flame and at approximately 10% of the rated capac ity it has been rated at 98%.
which is manufactured from 'ceramic'
between the two materials. At some
material which can operate at high tem peratures for long periods. The incin erators were developed to continuously bum in applications such as landfills and industrial plants. When the burner is op erating at temperature, the material dif
plants, the cyclical effects of cold to ex
Operation of enclosed flares
ferences are overcome. In wastewater
From discussions with a number of
consultants; owners and operating au
plants where there is more gas than can be burned by the boilers on a year round
thorities it has been found that the en
basis, the incinerators have worked rea
closed flares have created operational problems for various reasons at a num
treme heat can occur several times each
day and this fatigues the mechanical fas teners.
It was reported in one case where a problem occurred,that the manufacturer indicated a requirement that the pilot fuel be bumed in the incinerator to main
tain the liner at warmer temperatures during the winter to reduce stress. This suggestion would have made the pilot fuel natural gas cost prohibitively high.
ber of installations. Some of incinera
sonably well. At the majority of treatment plants, 'waste gas' is generally present in the
tors work well but there are a number
summer when boiler loads are lower. In
newable energy simply to allow for the
of plants where they have not been suc cessful. Essentially operational prob lems seem to fall into specific catego
the winter, the gas production may meet the normal heating requirements but there are periods of time when burning
tended to control an over abundance of
It also makes no sense to bum non-re mechanical limitations of a burner in
a renewable energy.
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