WO2014131788A1 - Vorrichtung zur beheizung einer rohrleitung - Google Patents
Vorrichtung zur beheizung einer rohrleitung Download PDFInfo
- Publication number
- WO2014131788A1 WO2014131788A1 PCT/EP2014/053706 EP2014053706W WO2014131788A1 WO 2014131788 A1 WO2014131788 A1 WO 2014131788A1 EP 2014053706 W EP2014053706 W EP 2014053706W WO 2014131788 A1 WO2014131788 A1 WO 2014131788A1
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- WO
- WIPO (PCT)
- Prior art keywords
- power source
- electrical resistance
- heating element
- resistance heating
- pipe
- Prior art date
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Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/42—Heating elements having the shape of rods or tubes non-flexible
- H05B3/44—Heating elements having the shape of rods or tubes non-flexible heating conductor arranged within rods or tubes of insulating material
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
- F17D1/04—Pipe-line systems for gases or vapours for distribution of gas
- F17D1/05—Preventing freezing
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/0004—Devices wherein the heating current flows through the material to be heated
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/0014—Devices wherein the heating current flows through particular resistances
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/42—Heating elements having the shape of rods or tubes non-flexible
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/54—Heating elements having the shape of rods or tubes flexible
- H05B3/56—Heating cables
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/40—Heating elements having the shape of rods or tubes
- H05B3/54—Heating elements having the shape of rods or tubes flexible
- H05B3/58—Heating hoses; Heating collars
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/016—Heaters using particular connecting means
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/021—Heaters specially adapted for heating liquids
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/037—Heaters with zones of different power density
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2214/00—Aspects relating to resistive heating, induction heating and heating using microwaves, covered by groups H05B3/00, H05B6/00
- H05B2214/03—Heating of hydrocarbons
Definitions
- the invention relates to a device for heating a pipeline, comprising an electrical resistance heating element which extends along a pipe.
- the electrical resistance heating element can be formed from the pipeline itself, but also additional heating elements e.g. in the form of an internal heating conductor, which are electrically connected at their ends to a voltage source.
- a device for heating pipelines is required, for example, in linearly concentrating solar power plants, in particular parabolic trough solar power plants or Fresnel power plants, in which pipes are flowed through by a salt melt.
- the pipelines are connected to networks that serve to record solar energy in the solar power plant.
- the radiant energy of the sun is concentrated by means of mirrors on specially thermally insulated pipelines.
- the pipelines are formed by series connected collectors.
- a collector comprises a mirror system that concentrates the radiant energy of the sun onto a section of pipe, a so-called receiver.
- pipelines that are advantageously heated are pipelines that are used to convey melts over long distances, such as liquid sulfur pipelines.
- the radiation energy detected by the receivers is transferred to a heat transfer fluid.
- a biphenyl / diphenyl ether mixture is used as the heat transfer fluid in particular, but limited by its decomposition temperature of about 400 ° C in its maximum operating temperature.
- other heat transfer fluids are required.
- salt melts in particular nitrate / nitrite salt melts, for example so-called solar salt 60, a mixture of sodium nitrate and potassium nitrate in a ratio of 60:40 are used for this purpose.
- a disadvantage of salt melts is their high melting temperature.
- Potassium nitrate mixture melts, for example, in eutectic, that is at a mixing ratio of 56:44 at a temperature of 218 ° C.
- molten salts with high melting points are difficult to operate safely.
- the freezing of molten salt can cause major economic damage in piping systems.
- the cause of the damage is, for example, the strong volume expansion of molten salts during melting.
- fittings and pipelines are pressed open and severely damaged.
- electrical energy can be used or heat from available heat storage can be used.
- heat is used from available heat accumulators, usually a hot heat transfer fluid is pumped through the piping system.
- a pipeline section is generally part of a larger pipeline network. This connected network is naturally at a near-ground potential, called ground potential, since the piping network of a process plant usually has many low-resistance connections to the potential of the environment.
- the wiring of the electrical heating element can be arranged so that the loop-shaped pipe section is connected to ground at the connections to the pipe network of the plant and connected to a pole of a power source at the point of loop reversal.
- the second pole of the voltage source is connected via a low-impedance return path to the grounded end of the heating element.
- the object of the present invention is to reduce the consumption of resources, in particular the consumption of copper, in the creation of heating systems in that it is possible to dispense with a return line completely with full preservation of the heating function.
- a device for heating a pipeline system comprising at least two pipes, along each of which extends an electrical resistance heating element, wherein at each end of a doublheizelement a potential near the earth potential adjusts and at one of this end lying position is connected to a pole of a DC power source or each having a phase of an n-phase AC power source, wherein when using an n-phase AC power source n is an integer equal to or greater than 2.
- a potential near the ground potential means a potential which is established when an electrical conductor is grounded or, alternatively, a potential which is established when two oppositely directed phases with the same magnitude of current and voltage meet in an electrical conductor and cancel each other out in this way, or if in an electrical conductor, a positive and a negative portion of a DC voltage with the same amount of voltage and current meet and in this way cancel each other in a neutral point.
- the circuit therefore corresponds to a double star connection.
- an electrical resistance heating element with one phase of an AC source and a second one electrical resistance heating element to a second phase of the AC power source, which is opposite to the first phase, are connected, and the two electrical resistance heating elements are electrically connected together at their ends.
- an electrical resistance heating element to the positive pole of a DC voltage source and the second electrical resistance heating element to the negative pole of the DC voltage source can be connected.
- the circuit is closed and at the electrical connection of the ends of the electrical resistance heating elements, the potentials fed into the electrical resistance heating elements cancel each other out. In this way, a potential near the ground potential is established at one end of the electrical resistance heating elements, without the electrical resistance heating elements being grounded.
- connection of the electrical resistance heating element to a phase of an AC power source or a pole of a DC power source may be at one end of the electrical resistance heating element or at any position between the two ends of the electrical resistance heating element. It is preferable if the electric resistance heating element at both ends, a potential near the ground potential sets and the resistance heating element between the ends to the pole of the DC power source or the phase of the AC power source is connected. The position at which the electrical resistance heating element is connected to the pole of the DC power source or the phase of the AC power source is dependent on the resistances of the electrical resistance heating element and the desired heating task.
- the resistance of the electrical resistance heating element can be realized, for example, by the use of electrically conductive materials of different conductivity or different conductor cross sections.
- an off-center position of the connection is chosen, for example, if a higher heating power is required in one region of the pipeline to be heated than in another part of the pipeline, for example as a result of poorer insulation in a region.
- an increase in the heat output with a constant line cross section is achieved by shortening the distance between the connection of the pole of the DC source or the phase of the AC source and the end at which a potential approaches the ground potential.
- each electrical resistance heating element is divided into at least two sections, with a potential near ground potential at the ends of each section, and a pole of a DC source or phase of an AC source connected between the ends, with the ends of all the sections, which are fed from a DC power source or an n-phase AC power source, electrically low impedance, that is, with a resistance that is significantly smaller than the resistance of the pipeline, connected together. Due to the electrical connection of the All of the sections fed from a DC source or an N-phase AC source are made to cancel each other's currents in the respective electrical resistance heating elements.
- each section is powered by at least two power sources, each power source may be a DC power source or an AC power source, and the power sources are each connected at different positions on the electrical resistance heating element.
- the DC source or the phase of an AC source are generated in a floating manner, that is to say that only a voltage difference but not an absolute potential is applied to the voltage source. If the self-potential of all power sources is floating, it is basically possible to operate electrically connected power sources at the same time. At alternating voltages, however, interfering couplings via the inductance of the circuits are possible. In particular, if different lengths of track and individual heating powers are to be set, it is possible that at least one power source from which the section is fed is a DC power source and at least one power source is an AC power source. This has the advantage that both power sources can be operated simultaneously.
- the number of pipes to be heated is greater than the number of poles of the DC source or the number of phases of the AC source, it is possible that when using DC sources in a number of pipelines greater than two each two pipes are grouped together, whose electrical resistance heating elements are connected to the poles of a DC power source or, in the case of n-phase AC sources in a number of pipelines greater than n, n pipelines are grouped together whose electrical resistance heating elements are connected to the phases of an AC power source.
- an n-phase AC power source can be realized by forming the multipole feeds from inverter or thyristor circuits. An adaptation to the resistance of the piping enables transformers with matching transmission ratio.
- the electrical resistance heating element used for the heating of pipelines may, for example, be a heating conductor routed in the pipeline.
- the wall of the pipe is at least partially electrically conductive and the electrical resistance heating element is formed by the wall of the pipe.
- a heating conductor routed in the pipeline has the advantage, particularly in pipelines through which molten salts are melted, that in the case of solidification of the salt, the salt is uniformly melted and forms a channel along the heating conductor, through which the salt, the volume of which Melting increased, can drain.
- the electrical resistance heating element is formed by the wall of the pipeline, it is preferred if a metal strip coated with a layer of an electrically highly conductive material is electrically conductively attached to the wall of the pipeline for current introduction and the metal strip has a lug projecting away from the pipeline to which a power source can be connected.
- the heating conductor which is fastened radially to the pipeline, allows the current to be fed evenly over the circumference of the pipeline.
- the metal strip is preferably made of the same material as the pipeline. In particular, when the pipeline and thus also the metal strip is made of a material which is not well electrically conductive, the coating with the electrically highly conductive material ensures a sufficiently small resistance for current introduction, in order to minimize the heating of the metal strip.
- compensators are designed so that mechanical forces due to the linear expansion of the pipeline can be compensated.
- the adaptation conductor is particularly preferably a heating conductor, which can be constructed as described below.
- Salt melts are used in particular in solar power plants, such as parabolic trough power plants or Fresnel power plants as heat transfer.
- Pipelines in such power plants each have curvature-free sections with a length of at least up to 100 m, usually up to 600 m. Due to the large straight sections, it is possible to insert a heating element into the pipe without having to be guided around pipe bends.
- the heating conductor is arranged in the pipe acentric, wherein the distance of the heating element is greater at a downwardly extending pipe section with a maximum slope of 45 ° than upwards.
- the eccentric insertion of the heat conductor in the tube avoids that, when the thermal expansion of the heating conductor causes sagging areas of the heating conductor between two fastening points, the heating conductor touches the inner wall of the pipeline. Even in the case of sagging, it is necessary that the heating conductor has no loose direct contact with the inner wall of the pipeline.
- For fastening the heating element it is possible, for example, to guide it in eyelets in the pipeline through which the molten salt flows.
- the heating conductor runs centrally in the pipeline.
- the device of the invention is also suitable for all other piping systems with at least two pipes to be heated. Such pipes can for example be flowed through by a heat transfer medium.
- the device according to the invention is also suitable, for example, for pipeline lines through which crude oil is transported. Especially at low outside temperatures can be avoided so that the oil in the pipeline solidifies and blocks the pipeline.
- the device according to the invention can also be used in order to stably stabilize the temperature of a medium flowing through the pipeline in addition to an insulation. so as to prevent the medium flowing through the pipeline from cooling down.
- the device according to the invention can also be used to further heat a medium flowing through the pipeline.
- the use of the device according to the invention is particularly preferably in pipelines in solar power plants, in particular a frozen heat transfer medium, for example solar salt, after freezing, as it may occur at a standstill of the solar power plant to melt again.
- a frozen heat transfer medium for example solar salt
- the pipeline forms a heating loop in the solar power plant.
- the electrical heating element can also assume any other shape with which heating of the pipeline is possible.
- an outer heating conductor which bears against the outside of the pipe wall.
- the pipeline with an electrically conductive inner jacket or outer jacket, which acts as a heating element.
- the electrical heating element is particularly preferably a heating conductor located in the pipeline.
- the electrical heating conductor may be insulated and not insulated.
- the heating element electrically isolated.
- the temperature of the medium conducted in the pipeline must also be taken into account.
- the material for the electrical insulation of the heat conductor must be selected so that it is stable with respect to the temperatures occurring in the pipeline and in particular to the temperature of the electrical heating conductor.
- the heating element in the form of a pipe or a channel with an arbitrary cross-section and to provide the wall of the pipe or the channel with openings, through the molten salt into the interior of the in the form of a tube or channel designed heat conductor can be flowed and is transported inside the heat conductor to form the fastest possible time during the melting of the salt a channel through which the molten salt can flow.
- the heating element for example, as an annular knit or fabric. Also for this purpose, a cavity is formed in the interior of the fabric or knitted fabric, through which molten salt can already flow.
- the heating element is also possible for the heating element to have at least one U-shaped or V-shaped depression extending in the axial direction. In the depression, the salt will first melt so that the depression forms a channel through which the molten salt can flow.
- a heating conductor with more than one u shaped or more than a V-shaped recess may for example have a star-shaped cross-section. It is also possible that such a heating conductor is designed, for example, in the form of a channel with a U-shaped cross section.
- a hollow body or a heating conductor having at least one U-shaped or V-shaped recess it is also possible, for example, to provide a solid electrical conductor, which is wrapped with a wire mesh.
- the molten salt may initially flow in the wire mesh before outside of the wire mesh has formed a surrounding the heating conductor channel.
- the heating element is a solid wire or designed in the form of a rope.
- the heating conductor may be formed of a material of good electrical conductivity, for example copper or aluminum, which is enclosed by a corrosion-resistant shell. This avoids that the highly electrically conductive material in the presence of salt, which flows through the pipe, corroded, whereby the heat carrier salt is contaminated and loses its thermal stability.
- a conventional conductor for example with current-carrying core and electrical insulation, as venezmosleiter, wherein in addition to the electrical insulation, a corrosion-resistant shell is applied.
- a protective metal shell as a corrosion-resistant shell can also serve as a return conductor for the current in this case.
- a Zietenelenan extract with insulated outer shell made of stainless steel is used. Such insulated heating conductors can also rest against the wall of the pipeline.
- the heating conductor can also be constructed of segments, in solar power plants, for example, one segment per receiver, which are electrically connected to each other during assembly, for example by screwing, welding or jamming.
- the design of segments also provides a concept for replacing a receiver within a series by cutting and reconnecting.
- the connections must be designed in such a way that permanently sufficiently low contact resistances are realized.
- the heating conductor When the heating conductor is in the form of a rope, one or more strands are twisted into a rope.
- the rope is preferably Holitzig.
- a gusset channel is created in the middle of the rope through which molten salt can flow and thus equalize the pressure.
- a spiral winding By twisting a rope with a strand a spiral winding can be made, which has a gusset channel in its center.
- Another advantage of using a rope is that the horizontal balance of thermal expansion can be facilitated.
- the individual tubes are preferably filled with a gas, for example air.
- the gas in the tubular strands increases buoyancy in the molten salt. This allows a reduction in the holding force required for fixing near the center of the tube springs.
- the tubular strands may have a circular cross section or a non-circular cross section.
- a non-circular cross section is, for example, an oval or an elliptical cross section.
- a non-circular cross-section it is possible that locally occurring increased pressures can be better elastically cushioned when melting the salt.
- the gusset cross-section is increased by non-circular cross-sections, thereby facilitating the pressure compensation flow in the gusset channel.
- tubes for forming the strands and to plate them for example by rolling.
- Another way to form a strand with a non-circular tube is a kidney-shaped cross-section.
- kidney-shaped cross-section which is formed, for example, when squeezing stranded round tubes over a round mandrel, a particularly large Zwickelkanal between the strands is created. Since the strands are taken up in a molten salt, it is advantageous to anneal the mechanically deformed parts stress-free in order to minimize the risk of corrosive attacks.
- the pipe When the pipeline is used as a pipeline in a solar field of a parabolic trough solar power plant or Fresnel power plant, the pipe usually includes an inner tube, which is flowed through by the molten salt and an outer shell made of glass. The space between the inner tube and the outer shell of glass is evacuated. The surface of the inner tube is usually designed so that it absorbs the solar radiation and thus warms up. The heat is then transferred from the inner tube to the heat transfer medium, which flows through the tubes. These areas are generally also called receivers.
- the pipes are usually U-shaped, wherein one leg of the pipe with an inlet and a second leg are connected to a drain.
- the legs of the pipeline extend without curvature over a distance of usually at least 100 m, preferably over at least 300 m.
- the two legs are connected to each other via a transverse piece of pipe.
- the molten salt then flows through an arc into the crosspiece and from the arc into the parallel second tube forming the second leg. tung.
- the pipe bends for flow deflection each have a pipe section which continues in the direction of the pipe, wherein the pipe section is closed with a closure and the heating element is guided through the closure of the pipe section. So that no voltage is transmitted to the pipeline during operation of the insulated heating conductor, the heating conductor is usually conducted with insulation through the closure of the pipeline. The insulation also serves as a seal.
- the closure of the pipe section can be designed, for example, as a blind flange. Also, any other lid that can withstand the pressure occurring in the piping can be used. However, a blind flange is preferred.
- a round rod is preferably attached to the end of the heat conductor.
- This can be connected, for example by a welded connection, a screw connection or a clamping connection with the heating conductor and insulating or non-insulating with the pipeline.
- the connection must be designed so that the round rod is well connected electrically conductive with the heating element.
- the round rod for mounting, for example, electrically insulating or non-insulating out in a stuffing box construction and fastened.
- the stuffing box packing of the stuffing box construction is made electrically insulating.
- a gap between the round rod and the implementation of the heating element is achieved in the pipeline.
- a low voltage of up to 0.7 V can be applied across the gap. Despite the low voltage prevails in the gap and in the vicinity of the gap, a high electric field strength. This high electric field strength causes a flow of current to and over the pipe wall when the piping system is filled with electrically conductive molten salt.
- the electrical insulation can be constructed, for example, in the region of a stuffing box or in the region of a flat gasket. If a gasket is used, electrically insulated fittings should also be used. Since materials used for electrical insulation are generally not resistant to the temperatures prevailing inside the pipes due to molten molten salt, it is possible to produce a temperature gradient by suitable thermal insulating materials. For example, it is possible in the area of the blind flange in the pipeline to take up a fiber material for thermal insulation. As fiber material, for example, a quartz fiber fabric can be used.
- the round rod, to which the heating conductor is attached, is guided through an electrically insulating and high-temperature-resistant sleeve, for example made of ceramic or silicon carbide.
- the first sleeve of ceramic or silicon carbide is followed by a second electrically insulating sleeve, which is no longer so high must be temperature resistant, on.
- a material for the second sleeve is for example polytetrafluoroethylene (PTFE) or another high-temperature plastic.
- PTFE polytetrafluoroethylene
- the two electrically insulating sleeves are enclosed by a further sleeve, which ends in a flange. The flange is closed with electrical insulation with a second flange.
- a stuffing box is used, which is sealed with a seal. Due to the insulating materials used, the temperature in the area of the stuffing box is so low that the seal can be manufactured from a standard material. If the solidified salt is to be melted in the pipeline, the heat conductor may produce only a small amount of heat in the introduction, so as not to jeopardize the formation of a temperature gradient. This can be achieved, for example, by virtue of the fact that the heating conductor has a lower electrical resistance in the region of its introduction into the pipeline than in the actual heating zone.
- the lower electrical resistance can be achieved, for example, in that the round rod into which the heating conductor opens is designed with a larger diameter than the heating conductor in the heating zone.
- the heating conductor can contain a particularly well electrically conductive material in order to avoid heating of the heating conductor in the region of the introduction into the pipeline.
- a suitable electrically highly conductive material is, for example, copper or aluminum.
- the heating conductor in the region of the introduction can be completely or partially made of the electrically highly conductive material.
- a rod with any other cross-section can also be used. However, a round bar is preferred.
- the inner conductor can not be installed in isolation in the piping system.
- the introduction is designed without any isolation measures. This is particularly advantageous if, for example, individual pipe sections of a solar loop are not connected to one another by flange connections, but are welded together. Then it is no longer possible to control the electrical resistance of the entire pipeline by insulating the individual pipe sections. If the heating element is not electrically insulated from the pipe sections welded together, currents will be present when a voltage is applied through the individual pipe sections and the inner conductor, the ratio of which is proportional to the ratio of the conductivity of the pipe to the conductivity of the heating conductor. According to the ratio, heat is generated at the pipeline or at the heating conductor.
- the resistance of the heating element can be lowered so far and the conductivity can be increased so that the current sufficiently led into the inner conductor is concentrated and the heat on the guided inside the pipe heating element to an extent that the mecanicleiter is heated faster than the pipeline.
- Conducive for a faster heating of the inner conductor is that the pipe has a generally much higher mass and thus a significantly higher heat capacity than the inner conductor. In such an arrangement with uninsulated heating element, ideally no potential differences between the heating conductor and the pipeline arise over the entire pipeline.
- the pipeline is to be electrically insulated from the equipment frame carrying the pipeline.
- the heat conductor is not damaged by the molten salt flowing through the pipeline, it is preferably made from a material resistant to corrosion compared to the salt used, in particular to nitrate.
- a corrosion-resistant casing it is possible, as already described above, to provide the heating conductor with a corrosion-resistant casing. If the heat conductor is made of a corrosion-resistant material, then, in particular, stainless steel, for example steels of the type St 1.4571 and St 1.4541, but also St 1 .4301 or nickel-based steels such as St 2.4856 are suitable.
- a passivating, approximately 15 ⁇ m thick corrosion-inhibiting metal oxide / nitride layer first forms on the heating conductor, which counteracts the flow of current to a noticeable resistance.
- the resistance of the protective layer helps to control the potential of the heating conductor system. Even small electrical voltages can cause electrode processes on conductive salts that lead to corrosive erosion. The electrode processes can start at a certain threshold voltage.
- the corrosion-inhibiting protective layer causes overvoltage protection and thus increases the decomposition voltage of the system.
- the use of the heat conductor inside the pipeline allows the control of high melting points of the heat carrier used in the pipeline. This opens up the possibility of using salt mixtures as heat carriers, which have a higher melting point than previously discussed salt mixtures.
- salt mixtures which have a higher melting point than previously discussed salt mixtures.
- nitrate mixtures containing sodium nitrate as the main component can be used. This has the advantage that potassium deposits, which can be used for the production of potash fertilizers, are largely spared.
- so-called “solar salt 60” contains 60% by weight of sodium nitrate and 40% by weight of potassium nitrate, and the proportion of sodium nitrate in the salt can be increased to 80% by weight or even over 90% by weight or more Accordingly, the salt increases from 235 ° C with a mixture of 40 wt .-% potassium nitrate and 60 wt .-% sodium nitrate to 273 ° C with a mixture of 80 wt .-% sodium nitrate and 20 wt .-% potassium nitrate and on 293 ° C. with a mixture of 90% by weight of sodium nitrate and 10% by weight of potassium nitrate When using pure sodium nitrate, the melting point is 306 ° C.
- FIG. 1 shows a plurality of pipelines with a central power supply
- FIG. 2 shows a plurality of pipelines which are divided into sections and wherein each section is connected to a power supply
- FIG. 3 shows a pipeline loop in a solar power plant, which is divided into two sections and in which current is fed into each section at two positions
- FIG. 4 shows a central power supply into a pipeline with internal heating conductor
- FIG. 5 shows an arrangement for feeding high currents into a pipe section in a sectional view
- FIG. 6 shows an arrangement according to FIG. 5 in a three-dimensional arrangement
- FIG. 7 shows a compound of two pipe elements, which are used as resistance heating elements.
- FIG. 1 shows a plurality of mutually parallel pipelines with a central power supply.
- a pipe 1 is equipped with an electrical resistance heating element.
- the electrical resistance heating element may be, for example, an electrically conductive wall of the pipeline to which a voltage is applied.
- a heating conductor can be used as an electrical resistance heating element.
- Such a heating conductor can run inside the pipe 1 or rest against the wall of the pipe 1 inside or outside.
- Each pipeline 1 has a first end 3 and a second end 5.
- a fluid for example a molten salt in a solar power plant or else oil or another liquid, can flow into the pipeline 1 through the first end 3. At the second end 5, the fluid leaves the pipeline again.
- each case it is possible, for example, in each case to connect the first end 3 of a plurality of pipes 1 to a distributor, not illustrated here, and in each case the second end 5 of a plurality of pipes 1 to a collector not shown here.
- the first ends 3 of all pipes 1 are connected to the distributor and the second ends 5 of all pipes 1 are connected to the collector.
- the collector and the distributor can also be designed in the form of pipelines, the pipelines 1 each branching off from the collector or the distributor.
- each pipeline comprises an electrical resistance heating element extending from the first end 3 to the second end 5.
- the electrical resistance heating elements are all electrically connected to each other.
- the electrical resistance heating elements are each connected to a phase 7 of an AC power source 9.
- the number of phases 7 of the alternating current source 9 corresponds to the number of pipelines 1. If the number of phases 7 is smaller than the number of pipelines 1, in each case so many pipelines 1 are combined into one group, as the AC power source 9 has 7 phases. Thus, each pipeline 1 of a group can be connected to a phase 7 of the AC power source 9. For each additional group of pipes 1 then a further AC power source 9 is used.
- each section is constructed in the same way as the shading shown in FIG.
- the positions at which the electrical resistance heating elements are electrically conductively connected to one another in order for a potential to approach ground potential describe the end of a section and at the same time the beginning of a subsequent section. It is not necessary to electrically conductively connect the electrical resistance heating elements immediately adjacent to each other, once to define the end of a section and immediately adjacent to the beginning of a new section. In each case, a position at which a potential near the ground potential and a position at the current is fed in alternate with one another for the section-wise supply of current.
- the current feed in the middle between two positions at which a potential close to the ground potential occurs.
- the power supply may also be outside the middle between two positions where a potential near ground potential occurs.
- the position at which the current is fed in depends on the resistance of the electrical resistance heating element and also on the desired heating power. If not heated homogeneously for example, the electricity is fed off-center. Due to the different lengths of the electrical resistance heating element between the power supply and the position at which sets a potential near the ground potential, resulting in different resistances and thus different heating capacities.
- the pipes can also assume any other shape.
- the pipelines in solar power plants, it is common for the pipelines to be U-shaped.
- each center in each leg to connect the running through the pipe 1 electrical resistance heating element to a power source and the electrical resistance heating both at the upper ends of the legs and in the region of the base of the U-shaped pipe electrically so that a potential close to the earth potential is established both at the connected ends and in the middle of the pipe forming the base of the "U.”
- the ends of the legs to be electrically conductive with one another to connect and provide the power supply in the base of the "U" formed by the pipeline 1.
- FIG. 3 shows a pipeline loop in a solar power plant, which is divided into two sections and in which current is fed into each section at two positions.
- each pipe 1 is formed in the form of a U-shaped pipe loop 1 1.
- the first end 3 of the pipe loop 1 1 is connected to a manifold 13 and the second end 5 of the pipe loop with a manifold 15.
- 1 1 current is fed respectively into the legs 17 of the pipe loop and both at the ends of the legs 17, where they are connected to the collector 13 and manifold 15 and at the opposite end of the legs 17, where this form the base of the "U", the electrical resistance heating elements are electrically connected to each other with low resistance, so that a potential is established near the ground potential.
- each leg 17 of the U-shaped pipeline forms a section 19, which in turn is divided into three sections, a first section 21 with a first resistor R1, a second section 23 with a second resistor R2 and a third section 25 with a third resistor R3.
- a power supply 27 is provided in each case between the first section 21 and the second section 23 and between the second section 23 and the third section 25, a power supply 27 is provided.
- an AC power source 9 is used, which is connected to a transformer 29.
- the transformer 29 is followed by a first switching device 31, for example a thyristor switching device, and a second switching device 33, which are in turn connected to each other with a changeover switch 35, so that either via the first switching device 31 current in the electrical resistance heating elements between the first sections 21st and the second sub-sections 23 is fed or via the second switching device 33 current between the second sections 23 and the third sections 25 is fed.
- a first switching device 31 for example a thyristor switching device
- second switching device 33 which are in turn connected to each other with a changeover switch 35, so that either via the first switching device 31 current in the electrical resistance heating elements between the first sections 21st and the second sub-sections 23 is fed or via the second switching device 33 current between the second sections 23 and the third sections 25 is fed.
- the respective electrical resistors R1 in the first sections 21, the respective electrical resistors R2 in the second sections 23 and the respective electrical resistors R3 in the third sections 25 are preferably the same size, so that cancel the phases at the low-resistance electrically conductive ends and a potential approaches near the earth potential.
- the resistors R1, R2 and R3 can be of different sizes.
- a converter circuit is also possible.
- a floating potential difference is generated by the secondary-side ungrounded transformer 29, on the other hand an adaptation to the resistances of the electrical resistance heating elements is possible through it.
- the function of the circuit shown in FIG. 3 will be described below by way of example.
- the solar loop shown in Figure 3 has six resistor sections in a paired arrangement with the resistors R1, R2 and R3.
- R1 has a much poorer isolation from R2 and R3.
- the switch in Figure 3 can be integrated into a temperature control, which sets the target temperature by varying the turn-on of phase 1 and phase 2.
- FIG. 1 An exemplary embodiment of a central power supply to an internal heating conductor of a pipeline is shown in FIG.
- leads 39 which are designed for example in the form of a stuffing box 41.
- additional strain relief devices for example in the form of hooks and eyes in the region of the feed point.
- FIGS. 5 and 6 show an arrangement with which high current intensities can be fed uniformly distributed over the circumference into a pipe section.
- the wall of the pipeline forms the electrical resistance heating element.
- the high current injection assembly includes a metal strip 43 that is welded to a length of pipe 45.
- the metal strip 43 and the pipe section 45 are made of the same metal.
- the metal strip 43 has a length which is dimensioned so that after welding a flag 47 protrudes laterally from the tube. At the free end 49 of the flag 47 can then be made for example by means of a clamping device or screw not shown, an electrical connection.
- This arrangement has the advantage that the electrical connection is only slightly thermally stressed. A low thermal stress is achieved in particular by the fact that the length of the flag 47 and thus the distance to the pipe 1 are chosen large enough.
- the metal strip 43 is pulled as closely as possible on the pipe section 45 and welded to the pipe section 45. Further improvement in contact can be achieved, for example, by incorporating contact enhancement materials, such as solder materials, between tubing 45 and metal strip 43.
- the metal strip 43 is made of the same material as the pipeline, for example of stainless steel, this has a comparatively poor electrical conductivity.
- a layer 51 made of an electrically highly conductive material for example copper.
- the method for applying the layer 51 must be suitable for applying a thick electrically conductive layer.
- the layer 51 can be applied to the metal strip 43, for example by plating, in particular explosive plating.
- the thickness of the metal strip 43 and the layer 51 of electrically highly conductive material depend in particular on the required electric current. Thus, for example, is suitable for feeding a 1000 A electrical current of about 20 mm wide and 3 mm thick metal strip 43, which is coated with a 3 mm thick layer 51 of copper.
- the pipe section 45 By pulling the metal strip 43 forces are entered into the pipe section 45. To exclude an impermissible deformation, it is therefore necessary, the pipe section 45 sufficiently stable, that is to produce with a sufficiently large wall thickness. In the case of thin-walled pipe sections, the stability can be achieved, for example, by flipping a steel strip to form a reinforced area 53. If the arrangement shown here for power supply is operated on a Joule heater, it can be observed that this has a lower temperature than the heated pipe. By a taper 55 of the metal strip in the vicinity of the pipeline 1, a hot spot can be selectively generated, which can heat the region of the power supply by heat conduction.
- FIG. 7 shows a connection of two pipeline elements which are used as resistance heating elements.
- a good approximation to these conditions is achieved when a compensator 57 is used in the form of a corrugated tube and in this case the wall thickness of the Kompensatorbälge 61 corresponds to the pipeline. In this case, it must furthermore be taken into consideration that the electrical resistance of the compensator 57 tends to increase as a result of the corrugation of the compensator bellows 61. If necessary, expansion joints not based on corrugated pipes can not be integrated into the Joule heating system at all. Also, mechanical requirements on the compensator 57 can greatly complicate the setting of a suitable electrical resistance.
- the matching conductor 63 With the matching conductor 63, the electrical resistance of the compensator 57 can be adjusted to the value of the remaining pipeline without significantly changing its mechanical properties. Possible adaptation parameters are, for example, thickness, length and material of the matching conductor 63.
- the matching conductor 63 it is possible to use all the compensators those not based on corrugated pipes to be included in a Joule heating circuit, besides only one matching conductor 63, it is also possible to use a plurality of matching conductors 63.
- the electrical currents from the matching conductors are introduced into the pipeline at one point.
- metal strips 65 with low electrical resistance can be used, which are drawn around the pipe 1 and welded. For example, copper-plated stainless steel strips can be used for this purpose.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Pipe Accessories (AREA)
- Resistance Heating (AREA)
Abstract
Description
Claims
Priority Applications (9)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ES14706621.1T ES2629908T3 (es) | 2013-02-27 | 2014-02-26 | Dispositivo para calentar una tubería |
MX2015011200A MX345140B (es) | 2013-02-27 | 2014-02-26 | Aparato para calentar una tuberia. |
EP14706621.1A EP2962523B1 (de) | 2013-02-27 | 2014-02-26 | Vorrichtung zur beheizung einer rohrleitung |
AU2014222767A AU2014222767B2 (en) | 2013-02-27 | 2014-02-26 | Apparatus for heating a pipeline |
MA38378A MA38378B1 (fr) | 2013-02-27 | 2014-02-26 | Dispositif de chauffage d'une conduite tubulaire |
CN201480023737.3A CN105191488B (zh) | 2013-02-27 | 2014-02-26 | 用于加热管线的设备 |
BR112015021049A BR112015021049A2 (pt) | 2013-02-27 | 2014-02-26 | dispositivo para aquecimento de um sistema de tubulação, compreendendo pelo menos duas tubulações |
IL240757A IL240757B (en) | 2013-02-27 | 2015-08-23 | Pipe heating device |
TN2015000366A TN2015000366A1 (en) | 2013-02-27 | 2015-08-25 | Apparatus for heating a pipeline |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP13156898.2 | 2013-02-27 | ||
EP13156898 | 2013-02-27 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2014131788A1 true WO2014131788A1 (de) | 2014-09-04 |
Family
ID=47779889
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/EP2014/053706 WO2014131788A1 (de) | 2013-02-27 | 2014-02-26 | Vorrichtung zur beheizung einer rohrleitung |
Country Status (12)
Country | Link |
---|---|
EP (1) | EP2962523B1 (de) |
CN (1) | CN105191488B (de) |
AU (1) | AU2014222767B2 (de) |
BR (1) | BR112015021049A2 (de) |
CL (1) | CL2015002415A1 (de) |
ES (1) | ES2629908T3 (de) |
IL (1) | IL240757B (de) |
MA (1) | MA38378B1 (de) |
MX (1) | MX345140B (de) |
PT (1) | PT2962523T (de) |
TN (1) | TN2015000366A1 (de) |
WO (1) | WO2014131788A1 (de) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3536122B1 (de) | 2016-11-07 | 2020-08-19 | Heatworks Technologies, Inc. | Vorrichtungen zum ohmschen erwärmen eines fluids |
CN107354459A (zh) * | 2017-07-26 | 2017-11-17 | 贵州省兴仁县荣凯五金搪瓷制品有限公司 | 一种搪瓷产品的制作设备 |
CN117730226A (zh) * | 2021-06-11 | 2024-03-19 | 恩文特服务有限责任公司 | 用于电伴热系统管理的系统和方法 |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2722359A1 (fr) * | 1994-07-08 | 1996-01-12 | Electricite De France | Dispositif de chauffage par effet joule a densite de flux variable d'un fluide dans un tube a passage de courant |
US20020122664A1 (en) * | 2000-12-29 | 2002-09-05 | Nexans | Heated flowline umbilical |
US20060102806A1 (en) * | 2004-11-16 | 2006-05-18 | Jim Noseworthy | Bracket for industrial piping |
WO2006075913A1 (en) * | 2005-01-13 | 2006-07-20 | Statoil Asa | System for power supply to subsea installations |
GB2437161A (en) * | 2006-04-10 | 2007-10-17 | Nexans | Power Cable for Direct Electric Heating System |
WO2012156472A1 (de) * | 2011-05-19 | 2012-11-22 | Basf Se | Rohrleitung zur förderung einer salzschmelze |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN2717162Y (zh) * | 2004-08-04 | 2005-08-10 | 张金辉 | 耐干烧电热器 |
-
2014
- 2014-02-26 AU AU2014222767A patent/AU2014222767B2/en not_active Ceased
- 2014-02-26 ES ES14706621.1T patent/ES2629908T3/es active Active
- 2014-02-26 BR BR112015021049A patent/BR112015021049A2/pt active Search and Examination
- 2014-02-26 MX MX2015011200A patent/MX345140B/es active IP Right Grant
- 2014-02-26 WO PCT/EP2014/053706 patent/WO2014131788A1/de active Application Filing
- 2014-02-26 EP EP14706621.1A patent/EP2962523B1/de active Active
- 2014-02-26 CN CN201480023737.3A patent/CN105191488B/zh active Active
- 2014-02-26 PT PT147066211T patent/PT2962523T/pt unknown
- 2014-02-26 MA MA38378A patent/MA38378B1/fr unknown
-
2015
- 2015-08-23 IL IL240757A patent/IL240757B/en active IP Right Grant
- 2015-08-25 TN TN2015000366A patent/TN2015000366A1/en unknown
- 2015-08-27 CL CL2015002415A patent/CL2015002415A1/es unknown
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2722359A1 (fr) * | 1994-07-08 | 1996-01-12 | Electricite De France | Dispositif de chauffage par effet joule a densite de flux variable d'un fluide dans un tube a passage de courant |
US20020122664A1 (en) * | 2000-12-29 | 2002-09-05 | Nexans | Heated flowline umbilical |
US20060102806A1 (en) * | 2004-11-16 | 2006-05-18 | Jim Noseworthy | Bracket for industrial piping |
WO2006075913A1 (en) * | 2005-01-13 | 2006-07-20 | Statoil Asa | System for power supply to subsea installations |
GB2437161A (en) * | 2006-04-10 | 2007-10-17 | Nexans | Power Cable for Direct Electric Heating System |
WO2012156472A1 (de) * | 2011-05-19 | 2012-11-22 | Basf Se | Rohrleitung zur förderung einer salzschmelze |
Also Published As
Publication number | Publication date |
---|---|
CN105191488B (zh) | 2017-07-14 |
EP2962523A1 (de) | 2016-01-06 |
MX345140B (es) | 2017-01-18 |
TN2015000366A1 (en) | 2017-01-03 |
AU2014222767B2 (en) | 2018-11-15 |
MA38378A1 (fr) | 2016-07-29 |
PT2962523T (pt) | 2017-07-10 |
CN105191488A (zh) | 2015-12-23 |
AU2014222767A1 (en) | 2015-09-17 |
ES2629908T3 (es) | 2017-08-16 |
BR112015021049A2 (pt) | 2017-07-18 |
IL240757B (en) | 2019-03-31 |
IL240757A0 (en) | 2015-10-29 |
MX2015011200A (es) | 2015-11-09 |
CL2015002415A1 (es) | 2016-01-15 |
MA38378B1 (fr) | 2017-02-28 |
EP2962523B1 (de) | 2017-03-29 |
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