U.S. patent application number 14/425581 was filed with the patent office on 2015-12-10 for radiant heating pipe.
The applicant listed for this patent is WS-Warmeprozesstechnik GmbH. Invention is credited to Joachim G. Wunning.
Application Number | 20150354808 14/425581 |
Document ID | / |
Family ID | 47140779 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150354808 |
Kind Code |
A1 |
Wunning; Joachim G. |
December 10, 2015 |
RADIANT HEATING PIPE
Abstract
Provision is made of a radiant heating pipe 10 which is designed
to conduct hot gas through a central portion 14 in a preferred
direction of flow SV, directed away from the burner 22, into at
least one return portion 16, 18 and preferably at least partially
back into the central portion 14, such that a recirculation flow
through the radiant heating pipe 10 is produced overall. The
smallest flow cross section D.sub.A for the gas in a zone 24, close
to the burner, of the central portion 14 is smaller than the
smallest flow cross section D.sub.E in a zone 26 remote from the
burner. Preferably, the radiant heating pipe 10 according to the
invention has a waist at the transition from a branching portion
13, close to the burner, to the central portion 14.
Inventors: |
Wunning; Joachim G.;
(Leonberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WS-Warmeprozesstechnik GmbH |
Renningen |
|
DE |
|
|
Family ID: |
47140779 |
Appl. No.: |
14/425581 |
Filed: |
August 29, 2013 |
PCT Filed: |
August 29, 2013 |
PCT NO: |
PCT/EP2013/067942 |
371 Date: |
July 1, 2015 |
Current U.S.
Class: |
126/91A |
Current CPC
Class: |
Y02E 20/34 20130101;
Y02E 20/342 20130101; Y02E 20/348 20130101; F23C 3/002 20130101;
F23C 2900/99001 20130101; F23C 9/00 20130101; F27D 99/0035
20130101; F23L 15/04 20130101 |
International
Class: |
F23C 3/00 20060101
F23C003/00; F23C 9/00 20060101 F23C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2012 |
DE |
20 2012 103 366.6 |
Claims
1. Radiant heating pipe (10) comprising: a burner connection (12),
a branching portion (13), a central portion (14) and at least one
return portion (16, 18) located next to the central portion (14),
said return portion (16, 18) forming a loop with the central
portion (14), wherein the central portion (14) comprises a zone
(24) close to a burner, said zone adjoining the branching portion,
and a zone (25) remote from the burner connection (12), and wherein
the zone (24) close to the burner has a smallest diameter (D.sub.A)
that is smaller than a smallest diameter (D.sub.E) of the zone (26)
remote from the burner.
2. Radiant heating pipe as in claim 1, wherein a cross-section of
the central portion (14) widens in a preferred direction of flow
(S.sub.V).
3. Radiant heating pipe as in claim 2, wherein the central portion
(14) is conical.
4. Radiant heating pipe as in claim 1, wherein a ratio of the
smallest diameter (D.sub.A) of the zone close to the burner to the
smallest diameter (D.sub.E) of the zone remote from the burner is
less than 2/3.
5. Radiant heating pipe as in claim 1, characterized in that a
diameter of an opening (21) of the burner connection (12) is
greater than the smallest diameter (D.sub.A) of the zone (24) close
to the burner.
6. Radiant heating pipe as in claim 1 further comprising a total of
two return portions (16, 18), each forming a loop with the central
portion (14).
7. Radiant heating pipe as in claim 6, wherein the central portion
(14) has a longitudinal axis (L), and that the return portions (16,
18) extend parallel to the longitudinal axis (L) of the central
portion (14).
8. Radiant heating pipe as in claim 1, wherein the central portion
(14) and the at least one return portion (16, 18) are located on
one plane.
9. Radiant heating pipe, wherein the central portion (14) and the
at least one return portion (16, 18) consist of sheet steel or cast
steel.
10. Radiant heating pipe as in claim 1, wherein the burner (22) is
connected to the burner connection (12).
11. Radiant heating pipe as in claim 10, wherein the burner (22) is
a burner (22) adapted for flameless oxidation.
Description
[0001] The subject matter of the invention is a radiant heating
pipe displaying improved flue gas recirculation.
[0002] Radiant heating pipes are used for the indirect heating of
industrial furnaces with fuel. Combustion occurs inside the radiant
heating pipe and the resultant thermal energy is transferred to the
material to be heated by radiant heat. Such radiant heating pipes
are described, for example, in publication DE 20 2008 009 065.
Here, special radiant heating pipes are formed in the so-called
double-P structure configuration.
[0003] In general, a radiant heating pipe has a burner connection
in which the burner is located. Adjoining the burner connection is
a branching portion and, adjoining that, a central portion. The
fuel gas supplied to the burner and the supplied air oxidize in the
radiant heating pipe. The oxidation zone takes up a larger space in
the radiant heating pipe. The gas participating in the combustion
moves through the central portion into at least one return. portion
that is connected to the central portion via an intermediate
portion, comprising at least one pipe bend piece. The central
portion and the return portion form a loop that, ultimately,
returns the flue gas to the branching portion. There, part of the
flue gas can be exhausted through the flue gas outlet. In doing so,
it may heat the supplied air, for example, and, furthermore, it may
be returned to the central portion, so that at least a part of the
flue gas is recirculated. Radiant heating pipes exhibiting the
double P structure configuration comprise two return portions
that--like the central section--also have generally the form of a
cylinder. In doing so, the diameter of the central portion is
typically greater than the diameter of respectively one of the two
return portions.
[0004] FIG. 2 illustrates a prior-art radiant heating pipe 10. The
radiant heating pipe 10 comprises a central portion 14 that has the
form of a cylinder. The central portion 14 thus has a diameter that
is constant along the length of the central portion 14. In such a
radiant heating pipe, irregular temperature distributions in the
radiant pipe wall, for example the central portion, as well as
undesirable CO values and NOx values can be observed.
[0005] The described radiant heating pipes having the double-P
structure configuration of prior art have been successfully used.
However, in each of these radiant heating pipes, temperature peaks
of the temperature ditribution were found, for example, in the
initial section of the central portion. This may be undesirable. In
addition, the search for possibilities of reducing CO and NOx
emissions resulting from the combustion process in the radiant
heating pipes has been ongoing.
[0006] It is the object of the invention to provide an improved
radiant heating pipe that minimizes the described disadvantages of
prior art and exhibits reduced CO and NOx emissions.
[0007] In accordance with the invention, this object is achieved
with a radiant heating pipe displaying the features of Claim 1.
[0008] The inventive radiant heating pipe comprises a burner
connection. This is a hollow, in which a burner can be installed.
The burner connection has a burner connection opening. Adjoining
the burner connection is a branching portion. A burner may extend
through the burner connection opening into the branching portion or
terminate in the burner connection. A central portion with a zone
of the central portion close to the burner adjoins said central
portion. Furthermore, the central portion comprises a zone remote
from the burner, said central portion being downstream of said zone
close to the burner. Between the zone close to the burner and the
zone remote from the burner, there may also be provided additional
zones of the central portion. The zone close to the burner and the
zone remote from the burner may, respectively, extend over a more
or less long distance along the central portion or have a length of
zero. At least one return portion is located next to the central
portion. The at least one return portion is connected to the
central portion via an intermediate portion as well as via the
branching portion. The central portion and the return portion,
together with intermediate portion and the branching portion, form
a loop in which a circulating flow may form.
[0009] The zone close to the burner and the zone remote from the
burner of the central portion may each have different diameters
along the central portion (along axial direction) so that,
respectively, a smallest diameter is defined at least in one
location of the zones. The smallest diameter of the zone close to
the burner is smaller than the smallest diameter of the zone remote
from the burner. Circulating flue gas moves through the central
portion into the at least one return portion and back to the
branching portion. Part of the flue gas leaves the radiant heating
pipe through a flue gas outlet, e.g., near the burner, and may thus
heat the supplied air, for example. Part of the gas may move back
into the central portion and recirculate via a return portion. With
the use of such a radiant heating pipe in accordance with the
invention it is possible, in contrast with prior art, to achieve
reduced CO and NOx values and a. more uniform wall temperature
distribution.
[0010] Preferably, the cross-section of the radiant heating pipe,
in any event the central portion, is circular. However, the central
portion and the at least one return portion may also have different
cross-sectional forms. In the case of a non-circular cross-section
of the central portion, both the zone close to the burner and the
zone remote from the burner have a cross-section displaying the
smallest area, wherein the smallest cross-sectional area of the
zone close to the burner is smaller than the cross-sectional area
of the zone remote from the burner.
[0011] In the central portion, the flue gases flow in a preferred
direction from the zone close to the burner into the zone remote
from the burner of the central portion. Preferably, the diameter or
cross-section of the central portion of the pipe body widens in the
direction of the preferred direction of flow. Preferably, the
diameter or cross-section of the central portion of the pipe body
widens in the direction of the preferred direction of flow, without
narrowing again (monotone). The central portion may act as the
diffusor and convert the dynamic pressure to static pressure.
[0012] Preferably, the pipe body of the central portion is
configured so as to widen conically in the preferred direction of
flow.
[0013] Preferably, the ratio of the smallest diameter of the zone
close to the burner to the smallest diameter of the zone remote
from the burner is less than two thirds. In the case of
non-circular cross-sectional areas, the smallest cross-sectional
area of the zone close to the burner amounts to preferably at most
two thirds of the area of the smallest cross-section of the zone
remote from the burner.
[0014] A burner may be installed in the burner connection and thus
be connected to the radiant heating pipe. Usually, a burner has a
basically cylindrical shape. Preferably, the burner connection is
adapted to the basic shape of the burner. The diameter or
cross-section of the burner connection, in particular the opening,
is preferably greater than the smallest diameter or cross-section
of the zone close to the burner.
[0015] Preferably, the radiant heating pipe comprises a total of
two return portions, each forming a loop with the central portion.
In this manner, it is possible to create a relative large surface
of the radiant heating pipe. Preferably, the central portion has a
longitudinal axis, and a return portion extends parallel to the
longitudinal axis on one side of the can portion. The other return
portion extends in parallel direction on the opposite side of the
central portion.
[0016] Existing return portions and the central portion are
preferably located on one plane in order to achieve an overall
compact design.
[0017] Preferably, the radiant heating pipe comprising two return
portion has a so-called double-P structure configuration.
[0018] The central portion and the return portion as well as
additional portions of the radiant heating pipe may be made of
sheet steel, cast steel or other materials. The radiant heating
pipe may also be made of ceramic material.
[0019] A burner such as, for example, a recuperator, e.g., a split
recuperation burner, or a regenerator burner, may be connected to
the radiant heating pipe. Particularly preferably, the burner is
adapted for flameless oxidation.
[0020] Advantageous embodiments of the invention can be inferred
from the dependent patent claims and the description. Advantageous
developments are obtained by combining at least one of the
independent claims displaying the features of one or more dependent
claims. FIG. 1 of the drawings is designed to augment the
description. FIG. 2 is not the subject matter of the present
application. The drawings are schematic representations. They show
in
[0021] FIG. 1 a radiant heating pipe in a double-P structure
configuration;
[0022] FIG. 2 a prior-art radiant heating pipe, said embodiment not
being the subject matter of the present application.
[0023] FIG. 1 shows a sectional view of art inventive radiant
heating pipe 10 comprising a burner connection 12, a branching
portion 13, a central portion 14, a first return portion 16 and a
second return portion 18. The central portion 14 adjoins the
branching portion 13. In the preferred direction of flow S.sub.V
toward the central portion 14, there is provided an intermediate
portion 20 that has two arcuate pipe sections and is connected to
the central portion 14. The first return portion 16 and the second
return portion 18 are connected--via the arcuate pipe sections of
the intermediate portion 20--to the central portion 14 on the side
of the radiant heating pipe 10 that faces away from the burner
connection 12. The first return portion 16 and the second return
portion 18 are connected to the branching portion 13, so that a
total of two loops with one return portion 16, 18, respectively, do
exist. There may also be only one loop, i.e., a return portion 16,
18 or, if more than two return portions 16, 18 are provided, there
may be appropriately more loops.
[0024] A burner 22 is installed in the burner connection 12. In
doing so, this may be a split recuperation burner, for example. The
central portion 14 has a zone 24 close to the burner and a zone 26
remote from the burner. The zone 24 close to the burner of the
central portion 14 adjoins the branching portion 13. The zone close
to the burner has the smallest diameter D.sub.A. The central
portion 14 is connected to the intermediate portion 20 via the zone
26 remote from the burner. The zone 26 remote from the burner--and
this is applicable also to the zone 24 close to the burner--may
extend along a length along the central portion 14, or it may have
a length of zero. The zone remote from the burner has the smallest
diameter D.sub.E. The smallest diameter D.sub.E of the zone remote
from the burner is greater than the smallest diameter D.sub.A of
the zone close to the burner.
[0025] The radiant heating pipe as in FIG. 1 has a waist at the
transition between the branching portion 13 and the central portion
14. Preferably, the ratio of the smallest. diameter D.sub.A of the
zone close to the burner to the smallest diameter D.sub.E of the
zone remote from the burner is less than two thirds. The opening 21
of the burner connection 12 is preferably greater than the smallest
diameter D.sub.A of the zone 24 close to the burner. A preferred
direction of flow S.sub.V is prespecified in the central portion
14, said direction of flow pointing from the branching portion 13
to the intermediate portion 20.
[0026] The diameter of the central portion 14 widens in the
direction of the preferred direction of flow S.sub.V and is
conical. For example, it is also possible for the central portion
14 to initially taper downstream of the branching portion 13 in a
zone 24 close to the burner in order to subsequently widen again in
a conical manner. In the exemplary embodiment, the first return
portion 16 and the second return portion 18 are straight pipe
pieces with a constant circular diameter exhibiting the same
cross-sectional area. Each of them extends parallel to the
longitudinal axis L of the central portion 14. The central portion
14, the first return portion 16 and the second return portion 18
are located on one plane and a form a double-P structure
configuration of the radiant heating pipe. Alternatively, for
example, only a single return portion 16, 18 may exist and the
radiant heating pipe 10 may thus form a P-configuration of the
radiant heating pipe.
[0027] The radiant heating pipe 10 overall is made of
heat-resistant sheet metal, tubular metal or cast steel; however,
it may also be made of ceramic. The burner 22 has at least one
connection for gas 28 and one connection for air 30. Furthermore,
the burner 22 has one or more gas outlets 34.
[0028] The radiant heating pipe 10 described so far operates as
follows:
[0029] Gas and air are fed to the burner 22 via appropriate
connections. On the burner, the gas exits through at least one gas
outlet 32, and the air exits via air outlets 24 at high speed. The
gas and the oxygen of the air react in the radiant heating pipe 10.
The hot gas flows through the central portion 14 in the preferred
direction of flow. Due to the widening of the cross-section of the
central portion 14, a reduction of the flow rate of the gas and an
increase of the static pressure occur. The gas flow is split in the
intermediate portion 20. One part of the gas flows through the
first return portion 16, the other part flows through the return
portion 18. The gas flow enters the volume of the branching portion
13. There, the gas flow is partially discharged through a flue gas
outlet and can be used, for example, for heating the supplied air.
The gas flow is partially mixed with fresh gas and air. In this
manner, an advantageous operation with flame less oxidation can be
achieved. The gas flowing through the radiant heating pipe 10 heats
the radiant heating pipe 10, said pipe releasing radiant thermal
energy into the industrial furnace, for example. The exemplary
embodiment in accordance with the invention exhibits an evened out
temperature distribution on the radiant heating pipe wall.
[0030] Provision is made of a radiant heating pipe 10 which is
designed to conduct hot gas through a central portion 14 in a
preferred direction of flow S.sub.V, directed away from the burner
22, into at least one return portion 16, 18 and preferably at least
partially back into the central portion 14, such that a
recirculation flow through the radiant heating pipe 10 is produced
overall. The smallest flow cross-section D.sub.A for the gas in a
zone 24, close to the burner, of the central portion 14 is smaller
than the smallest flow cross-section D.sub.E in a zone 26 remote
from the burner. Preferably, the radiant heating pipe 10 according
to the invention has a waist at the transition from a branching
portion 13, close to the burner, to the central portion 14.
LIST OF REFERENCE SIGNS
[0031] 10 Radiant heating pipe [0032] 12 Burner connection [0033]
13 Branching portion [0034] 14 Central portion [0035] 16 First
return portion [0036] 18 Second return portion [0037] 20
Intermediate portion [0038] 21 Opening [0039] 22 Burner [0040] 24
Zone close to the burner [0041] 26 Zone remote from the burner
[0042] 28 Connection for gas [0043] 30 Connection for air [0044] 32
Gas outlet [0045] 34 Air outlet [0046] D.sub.A Smallest flow
cross-section of the zone close to the burner [0047] D.sub.E
Smallest flow cross-section of the zone remote from the burner
[0048] S.sub.V Preferred direction of flow
* * * * *