EP0208241B1 - A heating unit - Google Patents

A heating unit Download PDF

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Publication number
EP0208241B1
EP0208241B1 EP86108966A EP86108966A EP0208241B1 EP 0208241 B1 EP0208241 B1 EP 0208241B1 EP 86108966 A EP86108966 A EP 86108966A EP 86108966 A EP86108966 A EP 86108966A EP 0208241 B1 EP0208241 B1 EP 0208241B1
Authority
EP
European Patent Office
Prior art keywords
frame
metal rod
voltage
insulation
electrical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP86108966A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0208241A1 (en
Inventor
Jorgen Kam
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Svend a Nielsen Ingenior- og handelsaktieselskab
Original Assignee
Svend a Nielsen Ingenior- og handelsaktieselskab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Svend a Nielsen Ingenior- og handelsaktieselskab filed Critical Svend a Nielsen Ingenior- og handelsaktieselskab
Publication of EP0208241A1 publication Critical patent/EP0208241A1/en
Application granted granted Critical
Publication of EP0208241B1 publication Critical patent/EP0208241B1/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H3/00—Air heaters
    • F24H3/02—Air heaters with forced circulation
    • F24H3/04—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element
    • F24H3/0405—Air heaters with forced circulation the air being in direct contact with the heating medium, e.g. electric heating element using electric energy supply, e.g. the heating medium being a resistive element; Heating by direct contact, i.e. with resistive elements, electrodes and fins being bonded together without additional element in-between
    • 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
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/32—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulators on a metallic frame

Definitions

  • the invention relates to an electrical high-voltage and high-power heating system for heating a gas, in particular a process gas, passed through the system, said system comprising a number of units mounted in side by side relation, each unit comprising a great number of heat wire coils connected in series and mounted on thermostable, preferably ceramic, tubes suspended in an inwardly thermostable, insulated frame of an electrically conducting material.
  • the frame floats on an unknown potential, the frame not being electrically connected to anything else, and that the electrically floating frame is surrounded by an outer insulation, which is again surrounded by an outer earthed frame. Thereby the heat wire coils are shielded.
  • a high voltage e.g. 30 KV can be applied to one end of the series connected heat wire coils, suspended on insulators in the floating frame, whereby a heating power rating 1/2 MW for each unit may be achieved.
  • the floating frame considerably diminishes the risks of a voltage breakdown.
  • the plant is preferably dimensioned for a power of at least 1 MW with a supply voltage of about 10 KV. The fact that a high voltage, e.g.
  • a three-phased supply line of about 10 KV or optionally about 30 KV often is available in connection with an industrial plant, is utilized in the inventive system.
  • voltage supply lines to the heat wires are metal rods surrounded by toroides in the places, where the supply lines are passed through the outer and the inner frame.
  • a very compact electrical heating system comprises three units or a multiple of three units, the heat wires of which are star connected, i.e. in one end they are connected to a phase each, and in the other end they are interconnected to form a common floating neutral point. This is advantageous in order to fully utilize the three-phased power supply.
  • An electrically conducting rail is preferably embedded in an insulating layer between the frames of two adjacent units, said rail being connected through a conductor to the floating neutral point of the heating unit, said conductor being monitored through a current transformer connected to a measuring device for detecting a leak current, if any. It is hereby made possible to monitor the system, and in case a leak current is detected, intervene before the leak current causes serious damages.
  • the heating wires may furthermore advantageously be monitored by pyrome- ters in order to disconnect the current to the heating wires, if the wire temperature should exceed a given allowable value of e.g. 500 to 700°C.
  • a triple insulation is provided between the phases (R, S, T) comprising a first layer of insulation located between the heat wire and the vertical sides of the inner frame, a second layer of insulation between said inner frame and the adjacent inner frame located along the horizontal sides of the frames and a third layer of insulation in the adjacent inner frame located between the vertical sides of said frame and the heat wire in said frame.
  • This object is obtained by a terminal box forthe supply of voltage to the metal rod, wherein field distributing plates are provided on both sides of the metal rod said field distributing plates extending to a considerable extent beyond the dimensions of the metal rod and being located substantially approximately in the centre of the air gabs between the metal rod and the closer metallic plate walls in the surrounding terminal box, and in that all connections to the metal rod are spherical, and that cooling means are provided in the box.
  • the heating system illustrated in Figure 1 is formed as a duct passed by the process air to be heated.
  • the duct is thermally and electrically insulated.
  • On the outside the heating system comprises an outer rectangular frame 12, e.g. of steel sections. Within said frame there are two layers of ceramic blocks 14, e.g. of Skamol @ . Three so-called cassettes 20 with a row of serially connected heat wires each are located in this insulated shell.
  • a cassette is built up of a frame 22, which on the inner side is coated with insulated ceramic blocks, preferably Skamol @ , type V 1100.
  • the electrical as well as the thermal insulating capacity is of essential importance in this construction.
  • the frame 22 consists of two rectangular steel sections connected to transverse sections in each corner.
  • transverse members 32 On the narrow vertical sides transverse members 32 are mounted, which are used as supports for a number of ceramic tubes 26 optionally built up of two tubes, innermost a tube of type 710 according to DIN 40685, e.g. Alsint O 99.7 with a great mechanical strength and capable of resisting breakdowns at an operating voltage of 10 KV and a temperature of 800°C. Round and concentrical with the Alsint' 5 tube a tube of type 530 may be provided after Silimanite@ 60 tubes capable of enduring great variations in temperature. This tube ensures an equalization of temperature compared to the Alsint @ tube.
  • a tube of type 710 according to DIN 40685
  • a tube of type 530 may be provided after Silimanite@ 60 tubes capable of enduring great variations in temperature. This tube ensures an equalization of temperature compared to the Alsint @ tube.
  • the ceramic tubes 26 carry the heat wires, wounded as coils 116. They may be of any common resistance material, but a nickel alloy, Ni 80, e.g. of the brand "Kantal @ is preferred, and the coils can advantageously form an almost star- shaped pattern as illustrated in Figure 6, which illustrates an end view of such a heat wire coil. Many similar coil patterns may obviously be used fulfilling the two necessary conditions, viz. that the coil can be firmly fixed round a tube and furthermore is capable of emitting its heat as efficiently as possible to the ambient passing air. Such coils are i.a. described in DE Patent Specification No. 28 50 111. Oxydized heat wires are preferably used, which are consequently surface insulated to some extent.
  • each column comprising e.g. fourteen tubes 26 wound with a heat wire.
  • the individual heat wire coils 16 are connected by heavy connecting wires of bars. All heat wire coils 16 elements in a cassette are, however, preferably substantially formed by a continuous heat wire 40, which on the spots where the wire passes through the intermediate wall 70, are connected in parallel with a suitably thick additional heat wire in order to reduce the heat emission in the place concerned.
  • a preferred coil arrangement is illustrated in Figure 7, where the coils are, however, only indicated.
  • a metal rod 30 forms the supply line to the heat wire 40.
  • the metal rod passes through the insulation 24 of Skamol° and the steel frame 22.
  • the metal rod 30 is surrounded by a toroide 34 ensuring an even field distribution around the metal rod.
  • the three cassettes 20 are preferably situated in side by side relation in such a manner that each cassette is connectable to one of the phases of a three-phased high-voltage system e.g. having a rated voltage of 10 or 30 KV.
  • the heat wires 40 are star connected as illustrated in Figure 8, and the upper metal rods 30 are preferably connected to the phase lines, and the lower metal rods are together connected to the neutral zero line 0.
  • the voltage level in the upper part of the construction is at about 10 KV or whatever high voltage chosen, and from there it drops evenly down to 0 volt in the bottom of the unit.
  • each mounted cassette is inserted on rollers or balls on rails 19 in Fig. 3 in the bottom of the system which is then closed by the outer insulation 14.
  • FIG 8. An electric diagram of the heating system is illustrated in Figure 8.
  • Each heat wire 40 is in one end connected to a phase line R, S, T, and in the other end they are interconnected.
  • the boxes 42 represent the resistance in the inner insulation between the steel frame 22 and the heat wires 40.
  • the conductor 22 represents the steel frame 22 itself, which in the ideal case will be voltage-free.
  • the boxes 44 represent the resistance in the outer insulation 14 on the outside of the steel frame 22 of the cassette.
  • the outer insulation 14 is secured by the outer frame 12, which is earthed.
  • the three inner frames 22 form three shells, which in respect to voltage are floating mutually as well as in relation to earth. Floating means no interconnections, and the voltage difference may assume any value.
  • the part of the construction most exposed to fault currents will be the upper part of the innermost insulation, the great differences in voltage being present in the upper part of the construction. Furthermore, the inner insulation will during operation be heated vigorously, and this heating will reduce the electrically insulating capability.
  • a leakage current from phase to phase has to pass three leakage paths, L1, L2, L3, wherein L1 lies in the inner frame insulation 24, 42, L2 is in the insulation 46 between the frames mutually, and L3 is in the inner insulation 24, 42 in the second frame.
  • the leakage paths are situated in three different places in the construction. The division into three leakage paths situated in three different places in the construction renders it very unlikely that the conditions of forming a voltaic arc will be present in all three places simultaneously.
  • a metal rail X can advantageously be embedded in the insulating layer 46 between the frames, said rail being connected to the internal floating "neutral" point of the heating system. It will then be possible by means of a current transformer to register an incipient leakage current between the phases. Such a leakage current could be caused by a smudging of the insulating material.
  • a set of terminal boxes 51 belongs to the heating system as illustrated in Figure 1.
  • the high voltage is supplied to one of the heat wire coils through the upper three terminal boxes 51, and the other end of the heat wire coils is connected to a common floating neutral point through the three lower terminal boxes in such a manner that the star connection illustrated in Figure 8 is achieved.
  • Figure 9 illustrates a terminal box 51 for a high voltage phase line 61 and the metal rod 30 passing through the side wall of the heating unit through the insulating layers 14, 24.
  • the phase supply line 61 are supplied from the top through an insulating suspension 62 and through a further insulator 66.
  • the supply line 61 is connected to the metal rod 30 in a globe 55 placed approximately in the center of the terminal box.
  • the feed-through into the terminal box of the metal rod 30 is passed through a number of insulating plates 60, cf.
  • Figure 13 which is preferably made of silicone rubber with an Er of about 2.
  • a laminated construction is applied consisting of several plates, which are glued together.
  • the metal rod 30 is further provided with a series of cooling fins 52, e.g. of alumina, as illustrated in Figures 9 and 11. These cooling fins are to keep down the temperature in the metal rod 30, as it must be borne in mind that the metal rod 30 extends from a vigorously heated area.
  • Both the metal rod 30 and the cooling fins 52 as well as the globe 55 are on both sides surrounded by insulating plates 54, and 54' (e.g. of Etranox ® , and preferably of Etronit° No. 1).
  • the plates are suspended with no conducting connection to anything else. A field distribution from the conducting high-voltage supplying parts is obtained by means of these plates.
  • the terminal box 51 is closed at the front by means of a lid 64. On its rear side 65 the lid is provided with ducts for cooling air to keep a suitably low temperature of the air in the terminal box. This is very essential as the breakdown voltage of a gas is very dependent on the temperature.
  • the lowermost terminal boxes for the neutral conductors correspond in principle to the terminal boxes described above, but the three terminal boxes are furthermore provided with feed-throughs allowing a coupling of the neutral conductors.
  • the feed-throughs in the side of the terminal boxes are constructed according to the same principle as illustrated in Figure 13. Toroides are furthermore used in order to obtain a further equalization of the fields.
  • a feed-through of the conductor 48 is provided in the terminal boxes of the neutral conductors, said feed-through connecting the electrically conducting measuring and monitoring rail X to the floating neutral point to enable a monitoring of the heating unit, so that a beginning leakage current will be registered quickly, and so that there is time for the high-voltage to be disconnected, in case a dangerous situation arises (Fig. 14).
  • Fig. 12 shows an enlarged section of the terminal box in Fig. 9 to illustrate the pressure-proof through-feed of a phase line 61.
  • the phase line 61 is surrounded by a coaxial cylindric insulator 66, closed in its lower end by a plug 67 provided with sealing rings 68, sealing against the phase line 61.
  • Below the plug 67 the conductor or phase line 61 is covered by an insulating mantle 69.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Resistance Heating (AREA)
  • Control And Other Processes For Unpacking Of Materials (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
EP86108966A 1985-07-09 1986-07-02 A heating unit Expired EP0208241B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO852759 1985-07-09
NO852759A NO157640C (no) 1985-07-09 1985-07-09 Varmeaggregat.

Publications (2)

Publication Number Publication Date
EP0208241A1 EP0208241A1 (en) 1987-01-14
EP0208241B1 true EP0208241B1 (en) 1989-09-20

Family

ID=19888387

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86108966A Expired EP0208241B1 (en) 1985-07-09 1986-07-02 A heating unit

Country Status (4)

Country Link
EP (1) EP0208241B1 (no)
CA (1) CA1264178A (no)
DE (1) DE3665766D1 (no)
NO (1) NO157640C (no)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3927006C1 (no) * 1989-08-16 1991-03-07 Vdm Nickel-Technologie Ag, 5980 Werdohl, De
CN111372334B (zh) * 2020-04-09 2022-11-01 方城县柞蚕原种一场 一种便携式移动电加温控制器
DE102020111987B4 (de) * 2020-05-04 2024-06-27 Kraftanlagen Energies & Services Se Heizeinrichtung
CN112412410B (zh) * 2020-11-05 2023-02-24 河南理工大学 一种煤层钻孔注热强化促抽方法
CN112412417B (zh) * 2020-11-05 2022-11-18 河南理工大学 本煤层水力造穴结合钻孔注热增透促抽方法
CN112412421B (zh) * 2020-11-05 2022-12-02 河南理工大学 穿层钻孔注热协同水力冲孔强化促抽方法
CN112412416B (zh) * 2020-11-05 2022-11-11 河南理工大学 一种冷冻致裂与注热激励相结合致裂煤体增透促抽方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1008918A (fr) * 1950-01-20 1952-05-23 Materiel Electr Et Mecanique S Dispositif de traversée de paroi pour amenée de courant électrique à un élément suspendu à ou porté par ladite paroi et application aux fours électriques
US2868944A (en) * 1957-06-12 1959-01-13 Foster Wheeler Corp Electric fluid heater
WO1982002460A1 (en) * 1980-12-30 1982-07-22 Nikitin Pavel Zakharovich Joint for connecting high-voltage winding of generator to lead-in rod
US4337390A (en) * 1981-01-22 1982-06-29 National Element, Inc. Electric heating element
FR2530320B1 (no) * 1982-07-19 1984-12-21 Fives Cail Babcock
DE3326463A1 (de) * 1983-07-22 1985-01-31 Egon 6834 Ketsch Könn Elektrische heizplattenmodule

Also Published As

Publication number Publication date
CA1264178A (en) 1990-01-02
DE3665766D1 (en) 1989-10-26
NO157640C (no) 1988-04-20
EP0208241A1 (en) 1987-01-14
NO852759L (no) 1987-01-12
NO157640B (no) 1988-01-11

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