U.S. patent application number 14/758797 was filed with the patent office on 2015-11-26 for pressure vessel and method of heating a gas in a pressurised pipe.
This patent application is currently assigned to SWEREA MEFOS AB. The applicant listed for this patent is SWEREA MEFOS AB. Invention is credited to Thomas Olsson.
Application Number | 20150338126 14/758797 |
Document ID | / |
Family ID | 51062375 |
Filed Date | 2015-11-26 |
United States Patent
Application |
20150338126 |
Kind Code |
A1 |
Olsson; Thomas |
November 26, 2015 |
PRESSURE VESSEL AND METHOD OF HEATING A GAS IN A PRESSURISED
PIPE
Abstract
A flowing pressurised gas is heated by being conveyed through a
gap (18) between two concentric tubes (16, 17) in a pressure vessel
(11, 12, 13). The inner tube (17) is heated by radiant heat from
inside and the tube is kept open towards the flow path of the gas
in the pressure vessel so that pressure equalisation is obtained
between the inside and outside of the inner tube without the tube
being part of the flow path of the gas.
Inventors: |
Olsson; Thomas; (Lulea,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SWEREA MEFOS AB |
Lulea |
|
SE |
|
|
Assignee: |
SWEREA MEFOS AB
Lulea
SE
|
Family ID: |
51062375 |
Appl. No.: |
14/758797 |
Filed: |
December 27, 2013 |
PCT Filed: |
December 27, 2013 |
PCT NO: |
PCT/SE2013/051622 |
371 Date: |
June 30, 2015 |
Current U.S.
Class: |
392/489 |
Current CPC
Class: |
F28D 7/106 20130101;
H05B 3/44 20130101; F24H 2250/02 20130101; F24H 9/0063 20130101;
F24H 3/081 20130101; H05B 2203/014 20130101; H05B 2203/022
20130101 |
International
Class: |
F24H 3/08 20060101
F24H003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 2, 2013 |
SE |
1300001-3 |
Claims
1. Method of heating a flowing pressurised gas in a pipe to a high
temperature by leading the gas through a narrow gap between two
tubes fitted in a pressure vessel, wherein the inner of the tubes
is heated from the inside and the heated gas is allowed to flow
freely from the gap out into the pressure vessel and on to the
outlet of the pressure vessel, comprising heating the inner tube
from inside by radiant heat from an electric element and keeping
the inner tube open towards the flow path of the gas for pressure
equalisation between the inside and outside of the tube without the
tube forming part of the flow path of the gas.
2. Method according to claim 1, comprising heating a first part of
the inner tube seen in the flow direction by a higher power per
unit of length than heating a following part of the tube.
3. Method according to claim 2, comprising keeping one end of the
inner tube closed and leading the buffer gas in towards the closed
end.
4. Pressure vessel intended to be fitted as part of a pressurised
gas pipe and arranged to heat pressurised flowing gas comprising;
two concentric tubes inside the pressure vessel, an inlet for
pressurised gas into the gap formed between the tubes; an outlet
from the pressure vessel; wherein the gap between the tubes has its
outlet in the pressure vessel and the inner tube has a heating unit
for heating the tube from inside; and wherein the interior of the
concentric tubes; is open towards the flow path of the gas in the
pressure vessel for pressure equalisation between the inside and
outside of the inner tube without the tube being part of the flow
path of the gas; and has an electric element for heating the tube
with radiant heat from inside.
5. Pressure vessel according to claim 4, comprising insulation
material in the pressure vessel for protecting the pressure vessel
walls against high temperature.
6. Pressure vessel according to claim 5, wherein the end of the
inner tube towards the outlet in the pressure vessel is closed and
the end of the inner tube towards the inlet is open.
7. Pressure vessel according to claim 6, comprising a conduit for
buffer gas that leads into the inner tube.
8. Pressure vessel according to claim 5, comprising a passage along
the outer of the concentric tubes to hold the inner tube open
towards the outlet in the pressure vessel.
9. Pressure vessel according to claim 8, wherein the passage is a
gap between the insulation and the outer tube.
10. The method of claim 1, comprising keeping one end of the inner
tube closed and leading buffer gas towards the closed end.
11. Pressure vessel according to claim 4, wherein the end of the
inner tube towards the outlet in the pressure vessel is closed and
the end of the inner tube towards the inlet is open.
Description
SCOPE OF THE INVENTION
[0001] The invention relates to a pressure vessel intended to be
fitted as part of a pressurised gas pipe and arranged for heating
the flowing pressurised gas, comprising two concentric tubes inside
the pressure vessel, an inlet for pressurised gas to the gap
between the tubes, and an outlet from the pressure vessel, wherein
the gap between the tubes has its outlet in the pressure vessel and
the inner tube has a heating unit for heating the tube from
inside.
[0002] The invention also relates to a method of heating a flowing
pressurised gas in a pipe to a high temperature by leading the gas
through a small gap between two tubes fitted in a pressure vessel,
wherein the inner tube is heated from the inside and the heated gas
is allowed to flow from the gap freely out into the pressure vessel
and on to the outlet of the pressure vessel.
PRIOR ART
[0003] U.S. Pat. No. 2,797,297 shows a heater that can heat
pressurised gas to a high temperature. The gas flows between the
walls of an outer pressure vessel and an inner tube and then back
through this inner tube along heating coils. EP 089 998 shows a
heater that has an annular gap between two tubes and a burner in
the inner tube that must thus be pressure-classified.
Object of the Invention
[0004] An object of the invention is to provide at relatively low
cost a gas heater for high pressure and high temperatures that is
easily constructed, easy to maintain and easy to adapt to different
conditions.
BRIEF DESCRIPTION OF THE INVENTION
[0005] The object of the invention is achieved when the inner tube
is open towards the flow path of the gas in the pressure vessel for
pressure equalisation between the inside and the outside of the
inner tube without the inner tube being part of the flow path of
the gas, and the inner tube has an electric element for heating the
tube from inside by radiant heat. The two tubes will thereby have
roughly the same pressure on their outside and their inside and
they do not need to be pressure approved. The tubes are therefore
interchangeable without this affecting the pressure vessel
approval. It is only the outer pressure vessel that has to be
approved. The electric element is simply interchangeable and is
separated from the flow path of the gas. For the process industry,
the tube quality can therefore be selected freely and the tubes
adapted to the process gas in question. For example,
powder-metallurgically manufactured tubes or ceramic tubes that do
not tolerate high pressures can be used. With normal tubes, a
catalytic effect on the gas can be obtained and carbon deposition
occure, for example, if the gas is a reduced gas containing an
H.sub.2 and/or CO. The Sandvik Kanthal APM tube (ferritic
iron-chromium-aluminium tube) is an example of a tube that can be
used. The invention is defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 shows a section through a gas heater as an example of
the invention.
[0007] FIG. 2 shows an enlarged inlet part of the heater shown in
FIG. 1.
[0008] FIG. 3 shows an enlarged outlet part of the heater shown in
FIG. 1.
[0009] FIG. 4 corresponds to FIG. 2, but shows an alternative
embodiment.
[0010] FIG. 5 corresponds to FIG. 2 and shows another alternative
embodiment.
DESCRIPTION OF THE ILLUSTRATED EXAMPLE OF THE INVENTION
[0011] FIGS. 1-3 show a gas heater in the form of a pressure
vessel, the outer casing of which consists of a tube 11 with ends
12, 13. The end 12 can be bolted firmly to a pipe, for example, or
directly to a reactor vessel in a process industry in order to
supply heated gas at a high pressure. The entering process gas at a
high pressure, for example 100 bar, that is to be heated to a high
temperature, for example 1000 degrees Celsius, is supplied through
the end 13. The tube 11 is insulated internally by an insulation 14
that is adapted to the high temperature that shall be reached. The
insulation can be a ceramic insulation or a fibre insulation, for
example. Different sections of the tube 11 can have different
insulations adapted according to the temperature, which increases
towards the outlet. The insulation can be created in layers with
different properties.
[0012] Inside the insulation's cavity 15, two concentric tubes 16,
17 are put in as is best shown by FIGS. 2 and 3. The upper ends of
the tubes are joined together in a sealing manner, for example
welded together or bolted together, and the gap 18 formed between
the tubes has an inlet 19 through the end 13 for the gas that is to
be heated, which is clearest from FIG. 2. The gap 18 is maintained
by control projections, which are not shown, on the inner tube. The
gap is open towards the cavity 15 in the insulation and towards the
tapering outlet 20 from the pressure vessel that is formed by this
cavity, which is shown best by FIG. 3. The inner tube 17 has a
closed end 21 at the outlet 22 of the gap 18. The tubes 16, 17 are
kept in place at the inlet 19 and the tubes can expand freely in a
longitudinal direction upon heating.
[0013] The inner tube 17 is open towards the end 13 and has
electric elements in the form of heating coils 23, 24 along its
length. The electric elements have their electric leads 25-28 led
in a sealing manner through the end 13. The inner tube 17 is thus
heated only by radiant heat from inside and the inner tube does not
participate in the flow through the gas heater, which means that
the electric coils are not exposed to chemical or catalytic
reactions to such an extent. The reaction risk can be reduced
further by having a small continuous supply of buffer gas to the
inside of the inner tube. In FIGS. 2 and 3, a supply line 30 for
buffer gas is shown that extends down towards the closed end 21 of
the inner tube 17.
[0014] Between the insulation 14 and the outer tube 16 is a gap 31
that provides pressure equalisation between the inside and outside
of the inner tube 17, since the inside of the inner tube here
remains open towards the gap outlet 22 and thereby towards the part
32 of the insulation cavity 15, i.e. open towards the outlet 20 of
the pressure vessel. The part 32 takes up the longitudinal
expansion of the tubes 16, 17.
[0015] The first coil 23 seen in the flow direction has a tighter
winding and greater power than the second coil 24 and the power of
the coils can be varied respectively so that the power supplied per
unit of length of tube reduces when the gas becomes hotter. The
first part of the flow path can have power that is three times as
great per unit of length as the last part, for example. The
temperature of the electric coils is limited thereby. It is
possible to have more than two zones with different power. The gas
that flows through the gap 18 acquires a large increase in volume
due to heating and pressure reduction. The pressure gradient and
heat transfer can be optimised by having a varying gap along the
length of the tubes.
[0016] FIG. 4 shows an alternative embodiment in which a separating
wall 34 seals between the pressure vessel tube 11 and the tube 16.
Instead of the inner tube 17 communicating with the outlet side of
the flow path of the gas in the pressure vessel, it communicates
with the inlet side through an opening 35. The embodiments are
otherwise the same.
[0017] FIG. 5 shows another alternative embodiment in which the
pressure vessel tube 11 has a flange 36 that is directly bolted to
a flange 37 on the inlet tube 38 for the pressurised gas that is to
be heated. The inner tube 17 is thus open towards the pressurised
inlet side of the flow path of the gas in the pressure vessel. The
gap 18 has its inlet 39. Only one, 25, of the electric connections
is shown.
[0018] The pressure vessel/gas heater can be manufactured in
various sizes and as an example of a typical size it can be said
that the outer tube 16 can have a length of 3.5 m and a diameter of
140 mm, and the pressure vessel tube 11 can have an outer diameter
of 600 mm.
* * * * *