Combustion – Process of combustion or burner operation – In a porous body or bed – e.g. – surface combustion – etc.
Reexamination Certificate
1999-10-13
2001-07-10
Price, Carl D. (Department: 3743)
Combustion
Process of combustion or burner operation
In a porous body or bed, e.g., surface combustion, etc.
C431S170000, C431S328000, C122S00400R
Reexamination Certificate
active
06257869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Description
This invention relates to reacting a plurality of reactant gas streams in a matrix bed of heat-resistant matter. More particularly, this invention relates to increasing the volumetric reaction rate of the matrix beds.
2. Description of the Related Art
The prior art discloses reacting a plurality of reactant gas streams in a reactor having a matrix bed of heat-resistant material such that a planar reaction wave front is formed within the matrix bed. Examples of such reactors include stabilized reaction wave flameless thermal oxidizers and recuperative heating flameless thermal oxidizers, as disclosed in U.S. Pat. No. 5,320,518 to Stilger et al. entitled “Method and Apparatus for Recuperative Heating of Reactants in an Reaction Matrix” (“Stilger”), which is incorporated herein in its entirety by reference. In general, flameless thermal oxidizers operate by flamelessly thermally oxidizing gases within a porous matrix bed of heat-resistant material. The oxidation is called “flameless” because it may occur outside the normal premixed fuel/air flammability limits. Other examples and variations of flameless thermal oxidizers are disclosed in U.S. Pat. Nos. 4,688,495; 4,823,711; 5,165,884; 5,533,890; 5,601,790; 5,635,139; 5,637,283; and 6,126,913, all of which are incorporated by reference herein in their entireties.
Prior Art
FIG. 1
shows an example of a stabilized wave flameless thermal oxidizer. The oxidizer comprises a processor
10
having a matrix bed
11
of heat-resistant packing material supported at the bottom by a plenum
12
for distributing a mixture of a plurality of reactant gases
18
entering the matrix
11
. The packing material may be comprised of ceramic balls, saddles, or ceramic foam of varying shapes and sizes or of other suitable heat-resistant packing. A void
13
over the top of the matrix
11
precedes an exit means
25
that penetrates the end wall
14
through which exhaust gases
22
exhaust. Through the bottom of the processor
10
is an inlet means
23
through which reactant gases
18
are introduced into the processor
10
. The reactant gases
18
include control air, fuel, and process gas. If necessary, the fuel, air, or process gas may be heated prior to introduction to processor
10
by applying external heat to the mixed process gas prior to entering the processor
10
. The plenum and lower portion of the matrix
11
may be heated by a suitable preheater
19
that, for example, may pass forced heated air into the processor
10
, or heat the bed by electrical means. At various points in the matrix
11
are located temperature sensing devices such as thermocouples
20
from which the output is fed into a microprocessor or programmable logic controller
21
that, in turn, controls the proportions, volumetric flowrate, and temperature of the input gases entering the processor
10
. The term “volumetric flowrate” shall be understood to refer to volumetric flowrate and/or mass flowrate.
Referring now to Prior Art
FIG. 2
, there is shown a schematic of the internal temperature zones and reaction wave front
22
of the stabilized reaction wave flameless thermal oxidizer. Typically, during operation, there will be a cool zone
27
below the uniform oxidation or combustion temperature that is being maintained within the reaction wave front. A planar reaction wave front
22
occurs in the matrix and has a stable shape with a radial, substantially uniform temperature distribution. Above the planar reaction wave front
22
will be a hot region
26
. By using temperature sensors
20
, the planar reaction wave front
22
may be relocated within the matrix by controlling the volumetric flows and conditions at the input end of the processor
10
.
Referring now to Prior Art
FIG. 3
, a processor
80
of a recuperative heating flameless thermal oxidizer has an inlet port
88
, an exhaust port
90
, a heating port
92
, a barrier
100
, and a matrix bed
104
. The inlet port
88
leads to an inlet plenum
94
at the bottom of the processor
80
. A number of feed tubes
96
extend through an impermeable, rigid tubesheet
98
preferably made of steel or metal alloy, and a heat-resistant ceramic insulating barrier
100
at the roof of the plenum
94
. The tubesheet
98
provides mechanical support for the tubes
96
. The lower ends of the feed tubes
96
are provided with caps
102
to retain the matrix bed
104
inside the tubes
96
. The caps
102
are provided with orifices
106
to permit the flow of gases from the inlet plenum
94
to the tubes
96
. The matrix bed
104
is made up of heat-resistant packing material, as with the stabilized wave flameless thermal oxidizer, that is supported by the barrier
100
. The packing material fills the region between the barrier
100
and the void
108
at the top of the processor
80
including the interior of the feed tubes
96
. The matrix bed
104
may be heated by forcing heated gases, such as air, in through the heating port
92
, and extracting the heated gases through the exhaust port
90
. Alternatively, the bed may be heated by electric heaters or other means. During preheating, a low volumetric flow of ambient air may be bled through the inlet port
88
and up through the heat exchanger/feeding tubes
96
to ensure the tube material is not overheated, and to help establish the desired system temperature profile. Once the matrix bed
104
of the recuperative heating flameless thermal oxidizer has been preheated, the gases are introduced to the processor
80
through the inlet port
88
. An adjusting means (not shown), that is analogous to the microprocessor or programmable logic controller
21
shown in Prior Art
FIG. 1
, also controls the volumetric flowrate and composition of the process gases to maintain a stable, planar reaction wave front that is similar to the planar reaction wave front
22
shown in Prior Art FIG.
2
. Exhaust gases are extracted from the processor
80
through the exhaust port
90
.
Now referring to Prior Art
FIG. 4
, a regenerative bed destruction system
210
, an example of which is disclosed in U.S. Pat. No. 5,188,804 to Pace et al., entitled “Regenerative Bed Incinerator and Method of Operating Same” (“Pace”), and which is incorporated herein in its entirety by reference, may also be used to treat plurality of reactant gas streams
203
. The destruction system
210
comprises a housing
212
enclosing a matrix bed
214
, a lower gas plenum
216
disposed subadjacent the matrix bed
214
, and an upper gas plenum
218
disposed superadjacent the matrix bed
214
. Both the lower gas plenum
216
and the upper gas plenum
218
are provided with gas flow aperture openings
220
and
220
′, respectively. These openings
220
and
220
′ alternately serve as gas flow inlets or outlets depending upon the general direction of the flow of the reactant gas streams mixture through the matrix bed, which is periodically reversed as discussed hereinafter. A heating means
222
, such as an electric resistance heating coil, is embedded within the central portion of the matrix bed
214
. The heating means
222
is selectively energized to preheat the material in the central portion of the matrix bed
214
to a temperature sufficient to initiate and sustain a planar reaction wave front similar to the planar reaction wave front
22
shown in Prior Art FIG.
2
.
During operation of the regenerative bed destruction system
210
, the gas stream
203
flows into the bed
214
through either the lower gas plenum
216
or the upper gas plenum
216
. The gas stream
203
flows through a supply duct
240
to a valve means
230
. The valve means
230
receives the stream
203
through a first port
332
and selectively directs the received streams
203
through either the second port
234
or the third port
236
. When the gas stream
203
is directed through the second port
234
, the gas stream flows through duct
260
and opening
220
and into the lower plenum
216
. When the gas stream
203
is directed through the third port
236
, the ga
Edgar Bradley L.
Holst Mark R.
Martin Richard J.
Stilger John D.
Young John D.
Price Carl D.
Thermatrix Inc.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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