Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF T!IE INVENTION
A. FIELD OF THE INVENTION
This invention relates to incineration apparatus
and in particular to such apparatus having a large combustion
chamber with a single burner in which the temperature
gradient is quite large.
B. PRIOR ART
Incineration apparatus is known in which an
industrial effluent is introduced in order to reduce
pollution by breaking down its components to simpler and
harmless gases. Some such incineration apparatus uses
the principle of thermal regeneration so that the heat
generated in the combustion or oxidation chamber is
largely recovered before the decomposed effluent is drawn
out and into the exhaust stack, One such thermal regeneration
system is illustrated in U.S. Patent 3,895,918 issued
to James H. Mueller on July 22~' 1975. In that system, a
number of heat-exchange sections are arranged about and
in communication with a central, high-temperature chamber.
Each heat exchange section includes a heat-exchange bed
of a large number of refractory elements made of ceramic
or the like ("stones") confined by inward and outward
perforated retaining walls. The effluent to be purified is
applied to an inlet duct ring which has branch ducts that
distribute the effluent to selected ones of those heat
exchange sections whenever their respective associated inlet
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valves are opened. In such apparatus, the effluent is
made to traverse the heat-exchange bed which may have
a front-to-back temperature gradient by virtue of the heat
generated in the central combustion chamber with which
it communicates.
The combustion chamber itself may be quite
large with a single burner located toward its bottom.
As a result, the temperature in the ~amber is quite
uneven with the chamber being cooler towards its top and warmer
at the bottom where the burner is. Thus, it is possible
that some of the effluent drawn through the heat-exchange
chamber into the combustion chamber may not come up to the
requisite temperature for substantially complete oxidation
of its components so that some of these incompletely
burned compounds may go out of the stack with the rest of
the exhaust.
One possible remedy is to use several burners
distributed at various points throughout the combustion
chamber. However, this is a relatively expensive solution
inasmuch as each burner requires its own set of valves,
controls, heat sensors, and the like Moreover, the
presence of several burners does not insure uniformity of
heat in the chamber. ~ather, there will be created several
zones with varying temperature gradients in the chamber.
Furthermore, each burner will require its own supply of
ambient combustion air which is relatively cool compared with
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the desired temperature within the oxidation chamber.
It is therefore among the objects of the
present invention to provide a system for insuring greater
heat uniformity and hence greater thermal efficiency of the
heat incineration apparatus, especially in large vol~me
apparatus,
Another object of the present invention is to
help to minimize the emission into the air of incompletely
oxidized industrial effluents.
Still another object of the invention is to
provide a uniform-heat-distribution incinerator at a cost
lower than alternative approaches.
A further object of the invention is to provide
incineration apparatus wherein the thermal efficiency of
the system is enhanced by reduction of the use of ambient
combustion air in alternative multi-burner systems.
Other objects of the invention will be apparent
to those skilled in the art upon perusal of the drawings,
specification and claims in this case.
Summary of the Invention
Incineration apparatus for purification of noxious
effluents or the like in which, to insure more uniformly
complete combustion in a chamber, predetermined amounts
of a raw fuel gas are mixed with the effluent before
application to the chamber.
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BRIEF DESCRIPTION OF THE DRAWINE
The sole figure of the drawing is a schematic,
fragmentary and partly sectional view of a preferred embodiment
of the present invention.
DETAILED DESCRIPTION OF THE DRAWING
As stated in the aforementioned Mueller patent,
one known thermally regenerative incineration apparatus
comprises a central, high temperature oxidation chamber 50
having a burner 46 located toward the bottom thereof with
which a plurality of heat-exchanger sections, such as the
section 17, communicate. The section 17 includes a heat-
exchange bed 17e of ceramic elements or '7stones" 17c retained
between ~ front (not sl~own) and back apertured waLl 17b.). Effluent
from an industrial process is applied to one or more of
the sections 17 by way of an inlet duct 12 which communicates
with an inlet duct ring 14. Vertical ducts such as duct
15 couple the ring to the space 17d in back of (outwardly of)
the outer retaining wall 17b, Vertical outlet ducts 19
couple the fipace L7d through outlet valves 27 to the
outlet duct ring 44. The exhaust duct ring 44 is itself
coupled by a duct 42 to the exhaust fan (not shown) whose
output is connected to a stack. A solenoid-controlled valve
13 in duct 15 regulates the input to the section 17. ~hen valve 13 is
open, and when the associated outlet valve 27 is closed,
the negative pressure i.nduced in the central chamber 50
51Z4
by an exhaust fan (not shown) coupled to the outlet duct
ring 44 via exhaust duct 42 conventionally draws the
effluent from space 17d through the bed 17e into the
central incineration chamber 50 and thence out of the
system via a different, relatively cool bed associated
with another one of the sections 17,
The burner 46 is supplied with fuel such as
natural gas by way of inlet valve 34 located in the main
burner supply line 49. Another modulating valve 36, 38
is in series with valve 34 and is coupled to temperature
indicating control 45, The latter has a direct connection
to a thermocouple heat-sensing element 54 located in the
dome 40 of the chamber 50. This thermocouple-control
combination is conventionally so arranged as to permit
a modulated flow of fuel gas to the burner 46 to maintain
an operating temperature as registered at the top of the
chamber 50 of about 1450F. It also acts to shut the
burner down below 1400F in one typical set of operating
parameters. It may also act to shut the burner down if
the temperature of the chamber 50 exceeds a predetermined
maximum, A supply of pilot gas for the pilot of the
burner is taken off from gas line 49 after valve 34
and is carried in line 23 via valve 32 and pilot line
47 to the burner. Valve 30 may be a manual valve which
may be turned off when it is desired to perform maintenance
on the burner or in the system as a whole.
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If the chamber 50 i5 very tall, the existence
of a single burner 46 in the bottom portion 48 will have
produced a wide disparity in the temperatures in the
chamber ranging from the highest at the bottom to the
lowest at the top with the result that some of the
effluent passing from left to right through the heat-ex-
change bed 17e may not be subject to complete combustion.
Therefore, when it leaves the chamber 50, it will ulti-
mately be expelled out of the system through the exhaust
ring 44 together with the purified effluent.
In accordance with the present invention, some
of the fuel gas is also diverted from the line 49 via
branch pipe 23 and supplied to the chamber 50 with the
incoming effluent. The auxiliary line 23 has a restricting
aperture indicated schematically at numeral 28 to limit
operation of the system to 5-6% LEL (Lower Explosive Limit).
Line 23 also includes a solenoid-controlled safety valve
24,26 which is coupled to a control 45 so that the former
will prevent fuel gas from being applied directly to
chamber 50 until the temperature therein attains at least
1400F. This ternperature insures that the raw gas will auto-ignite
when applied to chamber 50 and this tends to prevent
explosions.
In series with valve 24 is a modulating valve
22 and its operator 20 which is ~overned by a temperature-
recording control 18. Control 18 is couple~ to a
second thermocouple heat sensor 52 located in the dome 40.
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This control is also coupled to control 45 and is set so
that its operating setting is above the operating setting
of control 45, i.e., over 1450F. It is installed so
that it can override control 45 and its minimum lower
alarm point is at least as high as the lower setting of
control 45, Thus, the modulating valve assembly 20, 22
will permit the supply of enough raw natural gas, for
example, to the gas distributor or manifold 16 in the
inflow of effluent in inlet ring 14 to bring the central
chamber S0 up to about 1500-1600F and to maintain it
there. At the same time the burner 46 would then be on
low fire because its associated controller may be set to
turn down the main gas supply to it when the temperature
exceeds 1450F, for example, In this way it is the effluent
which furnishes most of the combustion air for the burner
which is operating substantially stoichiometrically, using
a minimum of ambient air.
The use of this system is highly advantageous,
especially where the incinerator has a large volume
combustion chamber and a relatively localized heat source.
In such installations there would be a large heat gradient
throughout the chamber resulting in incomplete combustion
of at least part of the incoming effluent. Mixing that
effluent with some of the fuel gas before application
to the chamber enables uniform auto-ignition of the
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mixture uniformly throughout the chamber. Since this
obviates more burners to solve this problem, less ambient
air, which is cool, is required than for the plural
burner alternative. This makes for more thermal efficiency,
especially since the main burner is usually on low fire
once the rare gas fuel is added and is operating
stoichiometrically with minimum ambient combustion air.
Other modifications of the system which are
embraced within the general scope of the invention will
occur to those skilled in the art upon perusal of the
present specification ~nd drawings. Consequently,
I desire that this invention be limited solely by the
claims which follow.
