U.S. patent application number 12/231704 was filed with the patent office on 2009-03-05 for method of operating an electrical heating arrangement.
This patent application is currently assigned to Ziemek Cable Technology GmbH. Invention is credited to Gerhard Ziemek.
Application Number | 20090057291 12/231704 |
Document ID | / |
Family ID | 40339839 |
Filed Date | 2009-03-05 |
United States Patent
Application |
20090057291 |
Kind Code |
A1 |
Ziemek; Gerhard |
March 5, 2009 |
Method of operating an electrical heating arrangement
Abstract
A method of operating an electrical heating arrangement of
considerable length using a heating line having at least one
heating conductor surrounded by an insulation resistant to high
temperatures. A metal tube (4) abutting against the insulation (3)
is formed around the heating line (1) and the heating line (1),
which is equipped with the metal tube (4) is inserted into a
metallic tube (5) which has a diameter larger than the metal tube
(4) and encloses, in addition to the heating line (1), an axially
continuous clearance space (6). A non-combustible gas having a
lower kinematic viscosity compared with air is inserted into the
clearance space (6), the gas completely filling the latter and
being kept permanently under pressure.
Inventors: |
Ziemek; Gerhard;
(Langenhagen, DE) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS & ADOLPHSON, LLP
BRADFORD GREEN, BUILDING 5, 755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Assignee: |
Ziemek Cable Technology
GmbH
|
Family ID: |
40339839 |
Appl. No.: |
12/231704 |
Filed: |
September 5, 2008 |
Current U.S.
Class: |
219/260 |
Current CPC
Class: |
H05B 3/42 20130101; F16L
53/38 20180101 |
Class at
Publication: |
219/260 |
International
Class: |
F23Q 7/00 20060101
F23Q007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2007 |
DE |
102007041983.1 |
Claims
1. A method of operating an electrical heating arrangement of
considerable length using a heating line having at least one
heating conductor surrounded by an insulation resistant to high
temperatures, characterized in that a metal tube bearing against
the insulation is formed around the heating line, the heating line
equipped with the metal tube is introduced into a metallic tube
which has a diameter larger than the metal tube and encloses, in
addition to the heating line, an axially continuous clearance
space, and a non-combustible gas having a lower kinematic viscosity
compared with air is introduced into the clearance space, said gas
completely filling the latter and being kept constantly under
pressure.
2. The method according to claim 1, characterized in that a gas
having a kinematic viscosity of at most 90.times.10.sup.-6
m.sup.2/sec at 500.degree. C. is used.
3. The method according to claim 2, characterized in that an inert
gas is forced into the clearance space.
4. The method according to claim 3, characterized in that argon is
forced into the clearance space.
5. The method according to claim 4, characterized in that the gas
pressure is monitored.
6. The method according to claim 5, characterized in that the gas
pressure is regulated to a constant value.
7. The method according to claim 6, characterized in that the gas
is fed from the remote end via a small tube which is fastened to
the metal tube of the heating line.
8. The method according to claim 7, characterized in that the outer
surface of the metal tube of the heating line is roughened,
preferably by sand blasting.
9. The method according to claim 1, characterized in that the gas
pressure is monitored.
10. The method according to claim 9, characterized in that the gas
pressure is regulated to a constant value.
11. The method according to claim 10, characterized in that the gas
is fed from the remote end via a small tube which is fastened to
the metal tube of the heating line.
12. The method according to claim 1, characterized in that the
outer surface of the metal tube of the heating line is roughened,
preferably by sand blasting.
13. An apparatus comprising: a heating line having at least one
heating conductor surrounded by an insulation resistant to high
temperatures, a metal tube bearing against the insulation and
formed around the heating line, wherein the heating line with the
metal tube is positioned in a metallic tube which has a diameter
larger than the metal tube and encloses, in addition to the heating
line, an axially continuous clearance space, and a non-combustible
gas having a lower kinematic viscosity compared with air completely
filling the clearance space, said gas having a constant
pressure.
14. The apparatus according to claim 13, wherein the gas has a
kinematic viscosity of at most 90.times.10.sup.-6 m.sup.2/sec at
500.degree. C.
15. The apparatus according to claim 13, wherein said
non-combustible gas is an inert gas.
16. The apparatus according to claim 15, wherein said inert gas is
argon.
17. The apparatus according to claim 13, further comprising means
to monitor the pressure of said non-combustible gas.
18. The apparatus according to claim 17, further comprising means
for regulating the pressure of said non-combustible gas so as to
maintain the pressure of said non-combustible gas at said constant
pressure.
19. The apparatus according to claim 13, further comprising means
for feeding said non-combustible gas from a remote end of said
clearance space via a small tube which is fastened to the metal
tube of the heating line.
20. The apparatus according to claim 19, wherein an outer surface
of the metal tube of the heating line is roughened.
Description
[0001] The invention relates to a method of operating an electrical
heating arrangement of considerable length using a heating line
having at least one heating conductor surrounded by an insulation
resistant to high temperatures.
[0002] Such heating lines are known and are obtainable on the
market. Their heating conductors are encased, for example, with
mineral or ceramic materials which are resistant at high
temperatures. Such heating lines are used in principle where
heating at high temperatures of, for example, up to 500.degree. C.
is to be effected.
[0003] A special field of use of heating lines for very high
temperatures is crude oil exploration from oil reserves in which
the crude oil is bound, for example, in porous rock, in sand or in
shale. Such oil reserves are located in the ground at a depth of
approximately 300 m. They extend over a large area at this depth.
To deliver the crude oil, therefore, not only are vertically
running bores placed, but said bores are continued in the ground
over large distances of, for example, 600 m. In order to be able to
pump the crude oil out of these reserves as completely as possible
with a conventional technique, it must be brought to a sufficiently
light-bodied state by heating the surrounding earth or rock.
[0004] The object of the invention is to specify a method of
operating an electrical heating arrangement with which it is
possible to also heat deeper regions of the earth's surface with
high efficiency.
[0005] This object is achieved according to the invention in a
method of the type mentioned at the beginning in that [0006] a
metal tube bearing against the insulation is formed around the
heating line, [0007] the heating line equipped with the metal tube
is introduced into a metallic tube which has a diameter larger than
the metal tube and encloses, in addition to the heating line, an
axially continuous clearance space, and [0008] in the operating
case, a non-combustible gas having a lower kinematic viscosity
compared with air is introduced into the clearance space, said gas
completely filling the latter and being kept constantly under
pressure.
[0009] The expression "air" in this case refers to the gas mixture
present at the earth's surface, with 77% nitrogen, about 21% oxygen
and about 2% residual quantities.
[0010] The outer metallic tube serves to protect the heating line
against the oil to be delivered and other aggressive media which
could lead to corrosion of the metal tube of the heating line. The
heat of up to 1000.degree. C. generated by the heating line is to
be transferred as completely as possible to the outer metallic tube
so that the desired heating of the oil to be delivered is
achieved.
[0011] With this method, the heat generated by the heating line is
transferred at high efficiency by optimum heat transfer to the
outer metallic tube, which in the fitted position is in direct
contact with the earth or rock to be heated. This essential
advantage is achieved by the gas located in the clearance space and
having a low kinematic viscosity, by means of which gas the heat
transfer by convection between the metal tube of the heating line
and the outer metallic tube is substantially increased. As a
result, the metallic tube and thus also its surroundings are heated
to a correspondingly more intense degree. Crude oil located in the
region of the metallic tube is thereby heated in such a way that it
becomes light-bodied and can be pumped out more easily.
[0012] The radiation as a further proportion of the heat transfer
between the metal tube of the heating line and the outer metallic
tube can be increased by roughening the outer surface of the metal
tube by the latter being subjected, for example, to sand blasting.
This measures leads to further improved transfer of the heat
generated by the heating line to the outer metallic tube.
[0013] The gas used is preferably an inert gas, such as argon. This
results in the further advantage that corrosion cannot occur in the
space enclosed by the metallic tube, and therefore the material
selection for the metal tube of the heating line is not
critical.
[0014] The method according to the invention will be explained with
reference to the drawings as exemplary embodiment.
[0015] In the drawings:
[0016] FIG. 1 shows a schematic illustration of a heating
arrangement which can be used for the method according to the
invention and with layers removed in sections.
[0017] FIG. 2 shows a section through FIG. 1 along line II-II in an
enlarged illustration.
[0018] FIG. 3 likewise schematically shows a heating arrangement
laid in the ground.
[0019] Shown in FIGS. 1 and 2 is a heating arrangement with a
heating line 1 which has an insulated heating conductor 2 which is
surrounded by a high-temperature insulation 3. Suitable materials
for the insulation 3 are mineral and ceramic substances. The
heating line 1 may also have more than one insulated heating
conductor. It may advantageously consist of three intertwined,
mineral-insulated heating conductors.
[0020] A metal tube 4 is placed over the insulation 3 of the
heating conductor 2 and bears against the insulation. It is
advantageously made of a material that is a good conductor of heat.
To improve the transverse stability and the flexibility of the
metal tube 4, the same may be corrugated transversely to its
longitudinal direction.
[0021] The heating line 1 is arranged in an outer metallic tube 5,
which has a diameter larger than the diameter of the metal tube 4
and additionally encloses a clearance space 6 relative to the
heating line 1. The areas of the outer surface of the metal tube 4
and of the inner surface of the outer metallic tube 5 are
preferably to have a ratio of 1:4. The clearance space 6 is large
enough so that a sufficient quantity of gas under pressure can be
introduced into said clearance space 6 and held therein. The
pressure with which the gas is introduced into the clearance space
6 is to be at least 1 bar. The outer metallic tube 5 is tightly
closed hermetically at its end 7. It has a wall thickness of
preferably 2 to 4 mm and is preferably made of high-grade steel so
that rusting can be ruled out in the long run.
[0022] The heating arrangement also includes a small metallic tube
8, through which gas can be forced into the clearance space 6. The
small tube 8 is fastened to the metal tube 4. It can run
rectilinearly, but can also be placed helically around the metal
tube 4. To increase its transverse stability and its flexibility,
the small tube 8 is advantageously corrugated transversely to its
longitudinal direction.
[0023] For heating a region located deep in the earth 9, first of
all the outer metallic tube 5 is installed in a borehole, through
which oil is to be pumped out of an oil reserve located in the
ground. The borehole comprises a vertical bore having an
approximately horizontally extension of considerable length. The
metallic tube is installed as indicated in FIG. 3. After that, the
heating line 1 with small tube 8 fastened thereto is pushed into
the outer metallic tube 5 to such an extent that its end lies
approximately at the level of the closed end 7. After that, the
metallic tube 5 is also tightly closed at its proximate end 9. The
heating line 1 is then connected to a voltage source 10, such that,
after switch-on, it generates heat preferably up to 1000.degree. C.
The small tube 8 is at the same time connected to a supply of
non-combustible gas provided with a pump 11. The gas is forced into
the small tube 8 by the pump 11. It discharges at its remote end 12
and thus passes into the clearance space 6, which it gradually
fills from the remote end. Air located beforehand in the clearance
space 6 is forced out of the same by the gas. To this end, a
closable valve is advantageously provided in that closure of the
metallic tube 5 which lies at the top.
[0024] As already mentioned, the pressure with which the gas is to
be introduced into the small tube 8 and thus into the clearance
space 6 is to be at least 1 bar. This pressure is monitored, for
example by means of a pressure gauge 13, while the method is being
carried out. It is preferably kept constant through the use of a
corresponding controller.
[0025] The gas forced into the clearance space 6 has a lower
kinematic viscosity than air, which is 96.7.times.10.sup.-6
m.sup.2/sec at 500C. The gas used is preferably to have a kinematic
viscosity of 90.times.10.sup.-6 m.sup.2/sec at 500.degree. C.
[0026] In an especially advantageous manner, the gas used is an
inert gas, such as, for example, and preferably, argon, having a
kinematic viscosity of 72.62.times.10.sup.-6 m.sup.2/sec. With
argon as the gas located in the clearance space 6, the heat
transfer by convection between metal tube 4 and outer metallic tube
5 is increased by about 15%. In addition, an inert gas in the
clearance space 6 prevents any corrosion at the metal tube 4 and at
the inner surface of the metallic tube 5. Therefore any desired
metal, such as steel for example, can be used for the metal tube
4.
[0027] The heat transfer between the metal tube 4 and the outer
metallic tube 5 by radiation can be additionally improved by the
outer surface of the metal tube 4 being roughened. This can be
advantageously achieved by sand blasting. By means of such a
measure, the heat transfer from the metal tube 4 to the outer
metallic tube 5 by radiation can be increased by about 25%, which
leads to an additional improvement in the efficiency of this
method.
* * * * *