U.S. patent application number 16/327845 was filed with the patent office on 2019-06-27 for cooling screen with variable tube diameter for high gasifier power.
This patent application is currently assigned to Siemens Aktiengesellschaft. The applicant listed for this patent is Siemens Aktiengesellschaft. Invention is credited to Norbert Fischer, Frank Hannemann, Andre Herklotz, Tino Just, Heidrun Toth.
Application Number | 20190194560 16/327845 |
Document ID | / |
Family ID | 59745903 |
Filed Date | 2019-06-27 |
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United States Patent
Application |
20190194560 |
Kind Code |
A1 |
Hannemann; Frank ; et
al. |
June 27, 2019 |
COOLING SCREEN WITH VARIABLE TUBE DIAMETER FOR HIGH GASIFIER
POWER
Abstract
A liquid-cooled cooling screen for an entrained-flow gasifier
for gasification of fuels in dust or liquid form using a gasifier
agent containing free oxygen, at pressures between atmospheric
pressure and 8 MPa and gasification temperatures between 1200 and
1900.degree. C. The liquid-cooled cooling screen of which the
cooling pipes in the central cylindrical section have thinner walls
than the cooling pipes in the lower and upper conical sections. A
cooling screen design has sufficient strength under high pressure
difference over the cooling screen wall, a pipe wall thickness
which ensures reliable operation of the cooling screen and high
heat throughput, and pressure equalization between the cooling
screen gap and the reaction chamber under all operating
circumstances.
Inventors: |
Hannemann; Frank;
(Rottenbach, DE) ; Just; Tino; (Freiberg, DE)
; Fischer; Norbert; (Lichtenberg, DE) ; Herklotz;
Andre; (Halsbrucke, DE) ; Toth; Heidrun;
(Freiberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Siemens Aktiengesellschaft |
Munich |
|
DE |
|
|
Assignee: |
Siemens Aktiengesellschaft
Munich
DE
|
Family ID: |
59745903 |
Appl. No.: |
16/327845 |
Filed: |
August 28, 2017 |
PCT Filed: |
August 28, 2017 |
PCT NO: |
PCT/EP2017/071574 |
371 Date: |
February 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10J 3/76 20130101; C10J
3/84 20130101; C10J 3/485 20130101; C10J 2300/0959 20130101; C10J
2200/09 20130101 |
International
Class: |
C10J 3/76 20060101
C10J003/76; C10J 3/48 20060101 C10J003/48 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2016 |
DE |
10 2016 216 453.8 |
Claims
1. An entrained-flow gasifier for the gasification of fuels in dust
or liquid form using a free oxygen-containing gasifying agent at
pressures between atmospheric pressure and 8 MPa and at
gasification temperatures between 1200 and 1900.degree. C.,
comprising: a reaction chamber connected to a quenching chamber
arranged therebelow via a guide pipe in a pressure shell, a cooling
screen, wherein the reaction chamber is delimited by the cooling
screen, a gasification burner configured to be arranged at the
upper end of the reaction chamber, wherein a cooling screen gap
between the cooling screen and pressure shell is flushed with an
inert gas, wherein the cooling screen is configured by the winding
of a number of cooling screen tubes through which a cooling liquid
flows, wherein the cooling screen has a tapering conical cooling
screen portion at the upper end, a tapering conical cooling screen
portion at the lower end and a central cylindrical cooling screen
portion therebetween, wherein the cooling screen tubes are
configured as a thick-walled cooling screen tube in the region of
the lower and the upper cooling screen portion and as a thin-walled
cooling screen tube in the region of the central cooling screen
portion.
2. The entrained-flow gasifier as claimed in claim 1, wherein a
setting angle of the conical cooling screen portion has an angle of
35.degree. to 60.degree..
3. The entrained-flow gasifier as claimed in claim 1, wherein the
cooling screen is supported by feet which are each fixedly
connected to at least three tube windings of the conical cooling
screen portion at the lower end and to three tube windings in the
cylindrical cooling screen portion situated thereabove.
4. The entrained-flow gasifier as claimed in claim 1, wherein an
outside diameter of the cooling screen tube is constant and the
transition from the thick-walled cooling screen tube to the
thin-walled cooling screen tube is configured to be smooth in an
inner part of the cooling screen tube.
5. The entrained-flow gasifier as claimed in claim 3, wherein the
transition from the thick-walled cooling screen tube to the
thin-walled cooling screen tube is arranged in a horizontal
direction between the feet, and at least one thick-walled cooling
screen tube is arranged above the foot in a vertical direction.
6. The entrained-flow gasifier as claimed in claim 1, wherein the
thick-walled cooling screen tube is continued into the cylindrical
cooling screen portion to such an extent that at least one cooling
screen tube achieves half a revolution in the cylindrical cooling
screen portion.
7. The entrained-flow gasifier as claimed in claim 1, wherein the
cooling screen is configured with a plurality of tubes which are
wound in parallel.
8. The entrained-flow gasifier as claimed in claim 1, wherein
flushing and pressure-equalizing tubes are arranged at an upper end
of the cooling screen.
9. The entrained-flow gasifier as claimed in claim 8, wherein the
flushing and pressure-equalizing tubes bear on bearing plates and
the remaining gap is sealed with fiber mats.
10. The entrained-flow gasifier as claimed in claim 9, wherein each
bearing plate is connected to a cooling screen tube.
11. The entrained-flow gasifier as claimed in claim 7, wherein the
cooling screen is configured with eight tubes which are wound in
parallel.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2017/071574 filed Aug. 28, 2017, and claims
the benefit thereof. The International Application claims the
benefit of German Application No. DE 10 2016 216 453.8 filed Aug.
31, 2016. All of the applications are incorporated by reference
herein in their entirety.
FIELD OF INVENTION
[0002] The invention relates to an entrained-flow gasifier for the
gasification of solid and liquid fuels at temperatures between 1200
and 1900.degree. C. and pressures between atmospheric pressure and
10 MPa (100 bar), wherein solid fuels are coals of different rank
which are ground to fine dust, petroleum cokes or other solid
carbon-containing materials, and liquid fuels can be oils or
oil-solids suspensions or water-solids suspensions, using a free
oxygen-containing oxidation agent, in which gasifier a cooling
screen 8 arranged in a pressure shell 15 delimits a reaction
chamber 9.
BACKGROUND OF INVENTION
[0003] In entrained-flow gasifiers, the thermally highly loaded
reaction chamber 9 is formed by a cooled tube construction. This
construction, the so-called cooling screen 8, as a whole is
pressure-stable only to a limited degree, with the tubes per se
being configured to be pressure-resistant. The cooling screen 8 is
positioned in a pressure vessel 15. For reasons of thermal
stability of the pressure container, a certain distance between the
pressure container and cooling screen is necessary. The thus
resulting backspace 10 (also referred to as cooling screen gap) is
flushed with an inert gas and has pressure equalization in relation
to the reaction chamber, with the result that, in normal operation,
equal pressure prevails in the reaction chamber and in the
backspace.
[0004] Since pressure changes in part constitute highly dynamic
processes, it must be ensured that pressure equalization can occur
in each operating state and that, as a result of a flow directed
into the reaction chamber, the penetration of reaction gas and dust
into the cooling screen gap 10 is limited. In addition, the cooling
screen as a whole must have a certain minimum resistance to
pressure differences over its wall. This minimum resistance to
pressure differences decreases with an increasing cooling screen
diameter and cooling screen height, and therefore this problem is
intensified with an increasing gasifier power. Furthermore, the
cooling screen is exposed to a high thermal loading and, in order
to avoid damage, good heat transfer from the reaction chamber into
the cooling water is required. This requirement can be achieved by
small tube wall thicknesses, this in turn counteracting the
differential pressure resistance of the cooling screen.
[0005] The prior art presents gasifier values of 500 MW, as
described, for example, in DE 197 181 31 A1. In the design
described therein, a cooling screen which consists of cooling tubes
welded in a gastight manner is situated within a pressure vessel.
This cooling screen is supported on an intermediate base and can
freely expand upward. This ensures that, upon the occurrence of
different temperatures on the basis of starting-up and shutdown
operations and resultant change in length, no mechanical stresses
occur which could possibly lead to destruction. To achieve this,
there is no fixed connection at the upper end of the cooling screen
but rather an annular gap between the cooling screen collar and the
burner holder flange that ensures free movability and is filled
with elastic, thermally resistant fiber mats. These mats are not
configured to be gastight and thus allow a dry, condensate-free and
oxygen-free gas to flow behind the cooling screen gap. This
flushing is intended to prevent hot gasification gas from flowing
back into the cooling screen gap upon pressure fluctuations. A
disadvantage with this configuration is that these mats are
positioned in the annular gap only in a form-fitting manner and can
be forced out of the guide under relatively high differential
pressures. Consequently, the mats no longer perform their function
of limiting the dust transfer from the reaction chamber into the
backspace, which ultimately means that reaction gas and dust pass
into the cooling screen gap 10 in spite of oppositely directed
flushing. The dust and gasification gas transfer into the backspace
results, on the one hand, in corrosion occurring on the rear side
of the cooling screen or of the pressure shell, which can lead to
destruction in the long term, and, on the other hand, the entry of
dust into the cooling screen gap 10 also causes an increased CO
concentration, after switching off the gasifier, within the
reaction chamber and the gas-channeling downstream systems.
Inspection and possible repair is thus greatly delayed for
safety-related reasons.
[0006] Alternatively, the gap, as described in DE10 2007 045 321
and DE10 2009 005 856, can be closed by means of a corrugated tube
compensator. In this configuration, the flushing gas is channeled
from the cooling screen gap 10 into the reaction chamber via an
additional pressure-equalizing line connected to the combination
burner, in order thereby to ensure the necessary pressure
equalization between the cooling screen gap and reaction chamber. A
disadvantage with this solution is the high price of compensators
of relatively large diameter and the additional amount of tubing
required for the pressure-equalizing line.
[0007] In order to protect the cooling screen at high gasification
temperatures and to limit the thermal loading, the cooling screen
design described in DE 197 181 31 requires a sufficient layer
consisting of liquid and solid slag on the cooling screen. It has
been found in practice that this slag layer can form a different
thickness depending on the coal used or its ash. As a result
thereof, the input of heat into the cooling screen and the amount
of heat to be removed therefrom can greatly increase and lead to
wall temperatures above the admissible material values and to
relatively high thermal wear.
[0008] In order to avoid damage to the cooling screen in these
cases, what is required is a smaller tube wall thickness, but this,
on the other hand, leads to smaller admissible pressure differences
over the cooling screen wall. This admissible pressure difference
is decreased further with an increasing gasifier power, since here
the reaction chamber diameter and, associated therewith, the
cooling screen surfaces are also increased and result in lower
strength values. A remedy to this is provided by a larger tube wall
thickness, but this counteracts the goal of a lower wall thickness,
reduces the heat transfer and reduces the amount of heat which can
be removed. An increased tube wall thickness causes greater
temperature differences between the tube inner side and tube outer
side, with the result that additional stresses are induced in the
tube wall. Both aspects, higher stresses and higher thermal wear,
lead to potentially shorter service times of the cooling screen.
Consequently, owing to the contrary effect of a changed tube wall
thickness, the area of application and the performance of the
cooling screen are limited to strength of the cooling screen versus
amount of heat which can be removed.
SUMMARY OF INVENTION
[0009] The problem on which the invention is based is to specify a
technical solution for the discussed, mutually conflicting
requirements.
[0010] The problem is solved by an object having the features of
the claims.
[0011] The invention makes use of the finding that, through a
corresponding burner configuration, the temperature release can be
set such that a lower thermal loading can be realized in the
conical regions of the cooling screen.
[0012] The solution according to the invention to the problem lies
in a cooling screen configuration with sufficient strengths under
high pressure difference over the cooling screen wall and a tube
wall thickness which ensures a reliable operation of the cooling
screen and a high heat transfer; also provided is a pressure
equalization between the cooling screen gap 10 and reaction chamber
9 in all operating states.
[0013] Advantageous developments of the invention are specified in
the subclaims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The invention will be explained in more detail below by way
of figures as an exemplary embodiment to an extent that is required
for understanding. In the figures:
[0015] FIG. 1 shows an 8-flight cooling screen according to the
invention having 4 feet distributed uniformly over the
circumference, and
[0016] FIG. 2 shows a configuration according to the invention with
8 bearing plates and 32 flushing and pressure-equalizing tubes
distributed thereon.
[0017] In the figures, identical designations designate identical
elements.
DETAILED DESCRIPTION OF INVENTION
[0018] According to the invention, thin-walled tubes 5 are used in
the region of the highest temperature loading, that is to say the
cylindrical part of the cooling screen, and, in order to ensure the
mechanical strength, thick-walled tubes 3 are used in the conical
regions of the cooling screen (at the top and bottom), in
particular for the purpose of taking up the bending moments through
intrinsic load and under differential pressures which occur.
[0019] The tubes are furthermore chosen such that the tube outside
diameter is kept constant over the entire cooling screen height 8
and the tube wall thickness is varied only over the tube inside
diameter. The transition from the smaller to the larger tube inside
diameters is here configured to be smooth via a gradual diameter
increase 4 in order thus to avoid the creation of "wake areas" in
which, owing to discontinuous flow conditions, sufficient cooling
cannot be ensured. The maintenance of a uniform outside diameter of
the cooling screen tubes leads to a homogeneous configuration of
the cooling screen. In addition to production-related advantages
(for example automatic welding), the thus ensured uniform
tampability of refractory material is particularly
advantageous.
[0020] To further increase the mechanical strength of the cooling
screen, the mechanical load of the cooling screen is dissipated
into the enclosing pressure shell 15 via feet 1, thereby further
reducing the bending moments overall and thus fundamentally
increasing the admissible pressure difference. However, the feet 1
provided simultaneously cause local stress peaks. For this reason,
the wall thickness transitions 4 described are, as far as possible,
positioned for outside the disturbance region of the feet (region
in which local stress peaks can occur by the feet in the presence
of mechanical loading). While maintaining a region of thinner wall
thicknesses 5 that is, as far as possible, large, the wall
thickness transitions 4 are arranged vertically above the feet and,
as viewed tangentially, centrally between the feet 1.
[0021] With a symmetrical configuration of feet, the following
formula for the horizontal arrangement of the wall thickness
transitions can be used for positioning the wall thickness
transitions 4 in the lower cylindrical region:
.gamma. = ? n P * k .times. z ##EQU00001## ? indicates text missing
or illegible when filed ##EQU00001.2##
[0022] where
[0023] .gamma.=angle between the center of the foot and the wall
thickness transition (7),
[0024] n.sub.P=number of feet and
k = n R n F , ##EQU00002##
where n.sub.R=number of cooling screen tubes.
[0025] Symmetrical configuration means that always the same number
of wall thickness transitions is arranged between the feet, that is
to say k is an integral number.
[0026] The vertical distance x between the foot and the first wall
thickness transition is chosen such that at least one further tube
with a large wall thickness is situated between the uppermost tube
connected to the foot and the tube having a wall thickness
transition. Here, the foot is advantageously configured such that
at least three tubes in the conical region and three tubes in the
cylindrical part are fixedly connected to each foot. With an
additional fastening of the foot to the upper tubes of the lower
conically configured cooling screen part, the load take-up of the
cooling screen can be configured to be particularly
advantageous.
[0027] In the upper region of the cooling screen, the thick-walled
tubes are used in the conical part and continued into the
cylindrical part to such an extent that at least one cooling screen
tube achieves half a revolution in the cylinder. A further increase
in the cooling screen strength is possible by an optimization of
the upper and lower conical cooling screen part in association with
an increase in the setting angle 16. However, since, on the other
hand, this increase in the setting angle leads to an increase in
the cooling screen gap 10, the amount of gas to be removed upon
emergency depressurization of the reactor 9 increases. With the
flushing and pressure-equalizing lines 13 remaining the same, an
increased amount of gas in turn increases the pressure difference
over the cooling screen and counteracts an increase in the strength
by a larger setting angle. Therefore, in an advantageous
configuration, an angle 16 of between 35.degree. and 60.degree. is
chosen. In the exemplary embodiment of FIG. 2, this angle 16 is
chosen to be 45.degree..
[0028] FIG. 1 represents an exemplary embodiment with eight cooling
screen tubes (8-flight cooling screen) and 4 feet distributed
uniformly over the circumference. The vertical distance has been
chosen to be four tube diameters and the horizontal distance has
been chosen to be 22.5.degree..
[0029] In spite of the described active measure for increasing the
admissible differential pressure over the cooling screen wall, the
admissible differential pressure in gasifiers of relatively large
output (and hence volume) is less than in the case of relatively
small gasifier powers of up to, for example, 500 MW, which means
that further measures are necessary in order to ensure secure
operation without accumulation of coal dust in the cooling screen
gap or corrosion of the pressure container 15 or of the rear side
of the cooling screen 8. It is ensured in terms of construction
that there is made available, in each operating state, a
sufficiently large flow-traversed area for pressure equalization,
but without allowing unhindered dust and reaction gas entry into
the backspace of the cooling screen. For this purpose, metal
flushing and pressure-equalizing tubes 12 are positioned in the
expansion gap of the cooling screen in such a way that, on the one
hand, the admissible pressure difference over the cooling screen
wall is not exceeded and that, on the other hand, the vertical
thermal expansion of the cooling screen remains ensured. For the
purpose of preventing dust transfer, the necessary gap remaining
for expansion is filled with flexible, thermally stable ceramic
fiber mats 11. For the arrangement of the metal tubes over the
circumference, bearing plates 13 are positioned at the upper
termination of the cooling screen, with the number of these bearing
plates being chosen such that they correspond to the number of
cooling screen tubes. The metal tubes 12 are uniformly distributed
on these bearing plates, and the remaining annular space between
the cooling screen termination and pressure container is sealed by
means of fiber mats 11 which are advantageously arranged above the
tubes. In order to ensure a directed flow or to avoid backflows, a
dry, condensate- and oxygen-free gas as flushing gas is introduced
into the reaction chamber 9 via the nozzle 14 and the flushing and
pressure-equalizing tubes 12.
[0030] FIG. 2 illustrates an exemplary embodiment with eight
bearing plates and 32 flushing and pressure-equalizing tubes
distributed thereon.
[0031] The invention is also provided by a reactor for the
gasification of solid and liquid fuels in the entrained flow at
temperatures between 1200 and 1900.degree. C. and pressures between
atmospheric pressure and 10 MPa (100 bar), wherein solid fuels are
coals of different rank which are ground to fine dust, petroleum
cokes or other solid carbon-containing materials, and liquid fuels
can be oils or oil-solids or water-solids suspensions, using a free
oxygen-containing oxidation means, wherein the reactor has a
cooling screen 8 and a pressure shell 15, wherein a cooling screen
8 delimits a reaction chamber 9 in a pressure shell 15, the cooling
screen is configured with a plurality of tubes which are wound in
parallel and through which a cooling liquid flows, the cooling
screen tubes have wall thickness changes with a thicker wall
thickness in the lower and upper region and a thinner wall
thickness in the central cylindrical region, and the setting angle
of the conical cooling screen region has an angle 16 of 35.degree.
to 60.degree..
[0032] The present invention has been explained in detail for
illustrative purposes on the basis of specific exemplary
embodiments. Here, elements of the individual exemplary embodiments
may also be combined with one another. The invention is therefore
not intended to be restricted to individual exemplary embodiments,
but rather restricted only by the appended claims.
LIST OF REFERENCE SIGNS
[0033] Key: [0034] 1 Foot [0035] 2 Thick-walled cooling screen tube
connected to foot [0036] 3 Thick-walled cooling screen tube [0037]
4 Wall thickness transition of the cooling screen tube [0038] 5
Thin-walled cooling screen tube [0039] 6 Vertical distance between
foot and wall thickness transition [0040] 7 Horizontal distance
between foot and wall thickness transition [0041] 8 Cooling screen
[0042] 9 Reaction chamber [0043] 10 Cooling screen gap [0044] 11
Fiber mats [0045] 12 Flushing and pressure-equalizing lines [0046]
13 Bearing plate for flushing and pressure-equalizing lines [0047]
14 Flushing connection in the pressure container [0048] 15 Pressure
container [0049] 16 Setting angle of the conical cooling screen
part [0050] 17 Conical cooling screen portion at the lower end of
the cooling screen [0051] 18 Cylindrical cooling screen portion
* * * * *