U.S. patent number 3,604,824 [Application Number 05/031,961] was granted by the patent office on 1971-09-14 for thermal incineration unit.
This patent grant is currently assigned to Universal Oil Products Company. Invention is credited to Leslie C. Hardison.
United States Patent |
3,604,824 |
Hardison |
September 14, 1971 |
THERMAL INCINERATION UNIT
Abstract
A thermal incinerator unit with an improved design that provides
a gas recycle passageway means around and in combination with the
combustion section to thereby limit the temperature increase
through such combustion section and provide a controlled burning of
the incinerated portion of the fumes. The recycle arrangement
within the incineration unit is particularly applicable to the
handling of a high B.t.u. content contaminated gas stream which
could normally result in an excessive temperature rise across the
combustion zone.
Inventors: |
Hardison; Leslie C. (Norwalk,
CT) |
Assignee: |
Universal Oil Products Company
(Des Plaines, IL)
|
Family
ID: |
21862336 |
Appl.
No.: |
05/031,961 |
Filed: |
April 27, 1970 |
Current U.S.
Class: |
431/116; 432/65;
432/72; 34/633 |
Current CPC
Class: |
F26B
23/022 (20130101); F23G 7/066 (20130101) |
Current International
Class: |
F23G
7/06 (20060101); F23l 015/00 () |
Field of
Search: |
;431/202,115,116,5,9
;263/3 ;34/155 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Favors; Edward G.
Claims
I claim as my invention:
1. A thermal incinerator unit for use in combination with a curing
zone discharging combustible fumes, which comprises in combination,
an elongated combustion section with a fume inlet opening at one
end and a hot gas outlet from the opposite end thereof, an
axial-positioned burner means directed into said inlet opening and
adjustable fuel supply means to said burner means, gas passageway
means from said hot gas outlet to said fume inlet opening to effect
a hot gas recycle to the latter at said burner means, additional
gas passageway means from said hot gas outlet to the curing zone,
and a gas outlet conduit from said hot gas outlet to effect a
cleaned gas discharge to the atmosphere, at least one adjustable
fresh air inlet means to said unit, and fan means connective with
said unit providing flow of fumes into said combustion section and
through said passageway and conduit means to maintain gas and fume
flows therethrough.
2. The thermal incinerator unit of claim 1 further characterized
that said gas passageway means for effecting hot gas recycle is
provided annularly around said elongated combustion section and in
heat exchange relationship therewith.
3. The thermal incinerator unit of claim 1 further characterized in
that a gas bypass passageway extends longitudinally coextensive
with said combustion section and is connective between said fan
means and said additional gas passageway means from said hot gas
outlet, whereby there may be a recirculation of a fume containing
stream to the curing zone without passage through said combustion
section.
4. The thermal incinerator unit of claim 3 still further
characterized in that said bypass passageway is in heat exchange
relationship with said hot gas recycle passageway means.
5. The thermal incinerator unit of claim 1 further characterized in
that a heat exchange section is provided in communication with the
hot gas outlet from said combustion section and air inlet means to
said heat exchange means provides for preheating air thereto, and
an outlet from said heat exchange section is in communication with
said additional gas passageway means to the curing zone whereby
heated fresh air may be admixed with gas from said hot gas
outlet.
6. The thermal incinerator unit of claim 1 further characterized in
that flow control means are provided in combination with the hot
gas outlet from said combustion section whereby there may be
regulation of the flow gases to said gas passageway means for hot
gas recycle and control of gas flow to said additional gas
passageway from said hot gas outlet.
7. The thermal incinerator unit of claim 1 further characterized in
that said gas passageway means from said hot gas outlet to said
fume inlet opening is of an annular form around said elongated
combustion section and a gas bypass passageway is provided in an
annular form around said annular form recycle gas passageway,
whereby there is a resulting heat exchange relationship between
said gas passageways.
8. The thermal incinerator unit of claim 7 still further
characterized in that flow control means are provided in said
bypass gas passageway whereby to control fume flow from said fan
means to said combustion section and to said gas bypass
passageway.
9. In combination with an oven of the type recirculating at least a
portion of the contaminated gas stream, a thermal incineration
section, comprising in combination, an elongated open-ended inner
shell defining a combustion section with a fume inlet and a hot gas
outlet means therefor, an elongated outer shell spaced around said
inner shell and providing a recycle passageway for recycle of hot
gases, a fume-laden inlet at one end of said outer shell in
alignment with the open gas inlet to said inner combustion
sections, a fume passageway from said oven to said fume inlet of
said combustion section, a burner with fuel supply means thereto
positioned centrally within said fume inlet to the latter, an
incinerated gas outlet from said outer shell, additional wall means
spaced adjacent said outer shell to provide a gas bypass section
therearound which is in heat exchange relationship with said outer
shell, a return passageway means from said bypass section to said
oven, and a blower means within said fume passageway to maintain
gas flow and gas recirculation within said incineration section and
said gas bypass section.
10. The combined oven-thermal incineration section of claim 9
further characterized in that adjustable flow control means is
provided within each of said gas passageways and said gas bypass
sections, whereby the volume of gas flow can be regulated within
each portion of said incineration section.
Description
The present invention relates to an improved form of thermal
incinerator unit and in particular to a type adapted for use with a
drying oven or a curing zone discharging an air-polluting gas
stream containing combustible components of high B.t.u.
content.
In accomplishing thermal incineration of combustible waste products
there is generally provided the direct emission of flame and hot
gases into the waste gas stream. In addition, there should be
provided the customary three elements of good combustion, i.e.,
time, temperature and turbulence. For high-efficiency incineration
systems, there have been various "recouperative" designs which
embody heat exchange means that will transfer heat from the hot
combustion gases to the incoming waste gas stream; however, such
designs are not necessarily adaptable to drying oven systems where
it is desired to reheat and recycle a portion of the waste gas
stream to the oven zone. Also, there may be a problem in the
handling of the high B.t.u. content gas stream in many of the
conventional incinerator units by reason of producing an excessive
temperature rise through the length of the combustor section of the
unit.
It may, therefore, be considered an object of the present invention
to provide a thermal incineration unit, particularly for
combination with a drying oven, such that there is provided means
to dilute the incoming combustible material in the contaminated
stream and thereby increase the effective "inlet temperature" of
such stream while, at the same time, reducing the temperature rise
through the combustor section to thereby hold to a given maximum
temperature at the outlet of the incinerator.
It may be considered a further object of the invention to provide a
unitary oven-incinerator design which provides for the special
blending in of heated gas at the inlet or burner and of the
incinerator section such that combustion of fumes in the gas stream
will be initiated with a minimum of fuel from a burner.
A still further object of the present invention is to provide an
overall unitary oven-incinerator design which will provide a gas
recirculation flow from and back to the oven as well as gas flows
through the incinerator section and to gas bypass sections.
In a broad aspect, the present invention provides a thermal
incinerator unit for use in combination with a curing zone
discharging combustible fumes, which comprises in combination, an
elongated combustion section with a fume inlet opening at one end
and a hot gas outlet from the opposite end thereof, an
axial-positioned burner means directed into said inlet opening and
adjustable fuel supply means to said burner means, gas passageway
means from said hot gas outlet to said fume inlet opening to effect
a hot gas recycle to the latter at said burner means, additional
gas passageway means from said hot gas outlet to the curing zone,
and a gas outlet conduit from said hot gas outlet to effect a
cleaned gas discharge to the atmosphere, at least one adjustable
fresh air inlet means to said unit, and fan means connective with
said unit providing flow of fumes into said combustion section and
through said passageway and conduit means to maintain gas and fume
flows therethrough.
As noted hereinbefore, the present improved design is particularly
adapted to accommodate high B.t.u. content fumes so as to effect an
efficient incineration of the fumes while precluding an excessive
temperature rise through the combustion zone. For example, because
of the limitations of the metal enclosure comprising the combustion
section, it may be undesirable to have a temperature which is
greater than about 1,350.degree. to 1400.degree. F. As a result,
the present design and arrangement provides for a recycle of hot
combustion gases from the outlet zone of the combustor section back
along the latter and into its inlet end in admixture with the fume
stream being introduced thereto. Where the fume stream is at
relatively low temperature, of the order of about 500.degree. F.,
there can be burner means to effect a preheating of this stream;
however, unless a large quantity of burner fuel is utilized, it is
difficult to effect the initiation of the incineration of the
fumes, and even with preheat to effect oxidation, there will be a
temperature rise of some 800.degree. F. to reach a 1,350.degree. F.
temperature at the outlet end of the unit. Thus, by providing
recycle gases, which are at the 1,350.degree. F. temperature level,
into admixture with the fume-laden stream, there can be a resulting
mixture of the order of at least about 1,050.degree. F., whereby
incineration can be started and there will be a lessened
temperature differential through the combustion section with better
operating efficiency.
In a preferred design of the incinerator section, the hot recycle
gases which are to be brought into admixture with the fume stream
will be returned through an annular-form passageway which is in an
indirect heat exchange relationship with the outer wall of the
combustion section so that there is a maximum retention of heat in
the system. Also, preferably, there will be utilized a heat
exchange zone at the downstream end of the combustion section so
that fresh air may be heated by indirect heat exchange means from
the incinerated fumes leaving the combustion section. The heated
fresh air together with a portion of the incinerated gas stream
and, where desired, a portion bypassed fume stream, may be passed
through suitable conduit means to the curing zone or drying oven
from which the fume stream is withdrawn.
In a simplified construction and design arrangement, there may be
utilized a single fan to effect the withdrawal of fumes from a
curing zone and the introduction of the fumes into the combustor
zone, as well as induce hot gas flow trough the recycle passageway
and combined heated gas flow back into the curing zone or oven. Of
course, where desired, additional fan means may be brought into use
in connection with the introduction of fresh air or to effect
increase flow rates with respect to recycle and gas bypass
passageway means.
In a more elaborate construction and design arrangement, there may
be incorporated a fume bypass passageway around or in a heat
exchange relationship with the hot recycle stream passing back
around the combustor zone such that recirculated gas may be carried
back to the oven or curing zone in admixture with a portion of the
oxidized gas stream. The bypass arrangement permits a controlled
portion of the fume-laden gas stream to be introduced into the
combustor zone such that there may be a short residence period in
such zone, say of the order of 0.1 to 0.2 seconds to produce of the
order of 80 percent conversion. However, an extended passageway
from the combustor zone can permit a greater residence time for the
net oxidized gas stream carrying to the discharge stack such that
there is at least about 0.5 to 0.6 seconds of residence time to
produce a greater than 90 percent conversion and an efficient
air-pollution control arrangement.
The recycle of a portion of the hot combustion gases from the end
of the combustor zone has the effect of increasing the effective
"inlet temperature" at a substantially constant outlet temperature
operation and, of course, this reduces the fuel requirements for
the burner means at the inlet means of combustor zone. In still
another aspect, the recycle arrangement provides for the admixture
with the combustible fume stream being introduced to the
incineration zone to effect an increased temperature for such
stream and a reduction in the temperature rise of the gas stream
carrying through the length of the combustion zone. Stated another
way, the practical result of the incinerator design is to provide a
unit that can provide high efficiency and a controlled maximum
outlet temperature which is particularly adapted for use in
combination with a drying oven or other type curing zone which
discharges a fume stream with a high B.t.u. content.
Reference to the accompanying drawing and the following description
thereof will serve to set forth the improved incinerator design and
construction, as well as point out additional advantageous features
which may be obtained from the use thereof in connection with the
incineration of high B.t.u. content gases.
FIG. 1 of the drawing is a schematic elevational view indicating a
thermal incinerator system providing for hot gas recycle in
combination with a curing zone.
FIG. 2 of the drawing is a diagrammatic side elevational view of an
alternate form of a thermal incinerator unit providing for both
recycle gas passageway and fume bypass passageway means which
encompass the combustor section of the unit in a heat exchange
manner.
FIG. 3 of the drawing is a partial elevational view indicating a
modified system for effecting the stagewise introduction of the hot
recycle gases into the combustor section of the unit.
Referring now particularly to FIG. 1 of the drawing, there is
indicated a thermal incinerator unit having a combustor zone which
is encompasses by shell means 2 with an inlet opening 3, formed
from baffle plate means 4, and an outlet section 5 connecting with
a stack means 6. There is also indicated the use of a gas
passageway tubes 7 providing a heat exchange zone 8 therearound to
accommodate the heating of a fresh airstream that is introduced by
way of inlet means 9. The latter, in turn, has a damper means 10
therein to control fresh airflow into the system. Upstream of the
inlet portion of the combustor section there is also provided a
mixing section 11 which is in communication with fan means 12 that,
in turn, receive a fume-laden stream from duct means 13 and fresh
air from duct means 14. The latter is provided with a damper or
valving means 15 to effect the control of the quantity of fresh air
being introduced into the system at this zone.
There is also indicated diagrammatically in FIG. 1 of the drawing a
small drying oven or curing zone 16 encompassed by housing means 17
adapted to accommodate the movement of wires or other coated items
that are passed through such curing zone. A fume-laden gas outlet
passageway from the curing zone is provided at outlet means 18 to
connect to duct means 13 and thence pass by way of fan 12 around
the burner means 19 and into the thermal incinerator section of the
unit. The burner 19 is indicated as being supplied with fuel by way
of line 20 and control valve means 21.
The downstream end of the combustor section 1 is provided with a
sidewall hot gas opening 22 which is connective with a recycle
passageway 23 as well as with a recirculation passageway 24 which
connects with and discharges into curing zone 16. The recirculation
passageway 24 also is in open communication with the heat exchange
zone 8 for the fresh air being introduced by way of inlet means 9,
whereby a resulting mixed gas stream of combustion products are
preheated air will be introduced back into the curing zone.
As a still further feature of the present design, there is
indicated a bypass passageway 25 connective with the fume or
combustor inlet zone 11 whereby a portion of the fume-laden gas
stream from fan means 12 can carry around combustor 1 and directly
back to the curing zone in admixture with preheated fresh air and
hot combustion gases from outlet means 22. In other words, the
bypass arrangement precludes having to pass all of the fume stream
through the combustor zone 1 and permits a controlled incineration
operation with only a desired portion of the total gas stream
having to be discharged as net gas through the stack means 6.
Further advantages of the bypass arrangement provide for the
present improved system of having a controlled temperature rise in
the incinerator section, while also providing for the blending of
the various gas stream, particularly as to quantity and
temperature, for recirculation into the curing zone. A damper 25'
can assist in flow control.
Referring now to FIG. 2 of the drawing, there is indicated a
modified form of incineration unit providing for an encompassing
arrangement of recycle and gas bypass passageways around an
internal combustion zone. Specifically, the is indicated an
internal combustion zone 26 defined by shell 27 which has a gas
inlet opening 28 and a downstream open end discharge arrangement
into tubular means 29 and into an outlet section 30 connecting to
stack means 31. A contaminated gas conduit 32 is indicated as
connecting to fan means 33 and the latter discharging into an inlet
section 34 which in turn is in open communication with a mixing
zone 35 leading to the combustion section inlet 28. A burner 36 is
also shown as being positioned within the inlet passageway 28 so as
to provide controlled heat for the mixed gas stream entering
combustor zone 26, so as to ensure ignition of the fume-laden gas
stream. In addition, burner 36 is provided with a fuel line 37 and
valve means 38 so as to provide controlled quantities of fuel
thereto.
In accordance with the present invention, which provides for
recycle of hot gases at and within the incineration section, there
is utilized an additional housing or shell means 39 concentrically
around shell 27 in order to form a recycle passageway 40. Thus, hot
gases from the outlet end of combustor zone 26 may pass through a
regulated area passageway or zone 41 into recycle passageway 40 and
be deflected from the latter into the mixing section 35 and to the
combustor inlet 38 to therein become admixed with the combustible
fumes entering from fan means 33. As will hereinafter be more fully
set forth, the recycle of hot combustion gases will provide an
effective higher temperature mixed gas stream so as to in turn
reduce the temperature rise across the length of the combustion
section in zone 26. For example, where the solvent or fume laden
gas stream is of the order of 500.degree. F. and below ignition
temperature, the admixture of discharged hot gases at a temperature
of the order of say 1,350.degree. F. can provide, without
particular aid from burner means 36, a mixed gas stream temperature
of the order of 1,050.degree. F. whereby ignition will take place
and the temperature rise through the length of the combustible zone
be held to the order of only 300.degree. F.
In a manner similar to that shown in FIG. 1, there is a heat
exchange zone built within the downstream end of the thermal
incineration unit of FIG. 2, by reason of a fresh air inlet duct
means 42, with damper means 43, leading into an encompassing heat
exchange section 44 around gas passageway tubes 29. Thus, a
preheated fresh airstream may be admixed into the hot gas steam
entering a recirculating gas passageway 45 to in turn be
transferred to a drying oven or curing zone by way of outlet means
46.
The present embodiment also indicates the use of shell means 47 at
a spaced distance around the combustor shell 27 and the recycle
shell 39 to provide a gas bypass passageway 48. The latter has an
inlet opening 49 communicating with the fan discharge section 34
and a downstream section which is an open communication with the
recirculating gas passageway 45 whereby a portion of the fume-laden
gas stream can entirely bypass the incineration zone and be
recirculated into the curing zone, drying oven, etc., in admixture
with at least a portion of the resulting combustion gases and
controlled quantities of preheated air.
Various types of flow control means or dampers may be used in
connection with the various gas passageways of the thermal
incinerator section and for the recirculation to the gas bypass
passageway. However, it is not intended to limit the control means
to any one type valving, dampers, or regulating apparatus, or to
any specific location. Diagrammatically, the present drawing
indicates movable damper means 50 at the passageway 41 so as to
regulate the quantity of hot gases that may be recycled in
passageway 40 and at the same time divert a portion thereof as a
hot gas stream passing into the curing zone from the incinerator
secton. There are also indicated damper means 51 at the inlet
section 49 for the fume bypass 48 so as to control the quantity of
gas being directly recirculated to the curing zone without passage
into the combustor zone. As hereinbefore noted, under certain
operating conditions, it may be desirable to only pass a small
portion of the fume-laden gas stream into the combustor zone 26 and
also pass a relatively small portion of the resulting hot combust
gases to stack means 31.
FIG. 2, as also provided by the construction of FIG. 1, effects an
extended residence chamber for the combustion section by virtue of
the hot gas stream from the combustor zone 26 being connective
through tube means 29 to an outlet section 30 which, in turn,
connects with the discharge stack, whereby adequate time for
thermal conversion of entrained fumes will be obtained to preclude
air-pollution. Still further, other damper or control valve means
may be embodied within the design of FIG. 2, as for example, within
outlet section 30 or upstream of the heat exchange tubes 29,
whereby a more closely controlled gas flow can be obtained.
Actually, it is not intended to limit the present thermal
incinerator unit to any predetermined volumes of gas flows within
the various passageways and within the central combustion section
inasmuch as the volume through the incinerator or combustor zone
may comprise an amount substantially equivalent to that for bypass
passageway 48 or a quantity which is greater or lesser than the
amount in the bypass passageway. However, in all cases, a
substantial quantity of the hot combustion gases leaving the
combustor zone 26 shall be recycled by way of passageway 40 back to
the combustor inlet so as to provide the higher inlet temperature
to such zone to result the desired low-temperature drop in the unit
as well as sustain an ignition temperature for the system. It is
also to be noted that variations may be made with respect to heat
exchange section or to the positioning of certain of the gas
passageways, inasmuch as the drawings may be merely diagrammatic in
this aspect. A preferred unit, however, provide for the heat
exchange relationship between the recycle passageway and the
combustion section 26, as well as a heat exchange relationship
between the recycle passageway 40 and the bypass passageway 48.
With reference to FIG. 3 of the drawing, there is indicated a
modification within the shell defining the combustor zone by reason
of shell 27' providing a plurality of spaced-apart, angularly
positioned gas inlet means 52 which will permit small portions of
the recycle gas stream from passageway 48 to be introduced at
spaced points in the combustor zone 26 and, in effect, reduce the
output from the burner means as well as keep the temperature rise
in the combustor zone to a low differential. The openings 52 as
shown are, of course, diagrammatic and can be varied as to number
and as to angular relationship with the wall of the combustion zone
and still be within the scope of the present invention.
* * * * *