RU2778545C1 - High temperature induction superheater - Google Patents

Abstract

FIELD: heating technology.

SUBSTANCE: invention relates to superheaters. The induction superheater comprises a ferromagnetic core with at least one primary winding and a tubular secondary winding with at least one shorted turn. A feature of the invention is the implementation of a tubular secondary winding in the form of an internal metal pipe covered with a layer of high-temperature ceramics with through pores with an effective diameter from 5 to 300 nm, and a layer of heat-resistant metal on top of a layer of ceramics. At the same time, the inner metal pipe and a layer of heat-resistant metal are connected to a source of electrical impulses.

EFFECT: increase in the reliability of the superheater by providing the possibility of cleaning the surface of the tubular secondary winding and removing deposits during the operation of the superheater, as well as improving heat transfer.

4 cl, 2 dwg

Description

The invention relates to devices for converting electrical energy into thermal energy and creating heat transfer and can be used primarily in high-temperature processes.

A common disadvantage of the known direct-flow steam generators is a sharp drop in the reliability of the pipes with increasing steam pressure and especially the heating temperature. This is an obstacle to the creation of high-temperature devices.

A direct-flow electric steam heater is known, containing a power unit for steam generation of an induction steam generator with a secondary winding, a power unit for superheating an induction superheater with a secondary winding, a ferromagnetic core with a primary winding connected to the network, secondary windings of the steam generator and a superheater located on the specified ferromagnetic core, while the secondary windings The induction steam generator and the induction superheater are made in the form of a tubular conductor with inlet and outlet nozzles for passing water through the inner cavity of the inner conductor, the conductive surface of which is made in the form of a closed one-sided Möbius surface (RU No. 171694 U1, published on 06/13/2017).

Closest to the proposed one is a direct-flow electric steam generator containing a flat ferromagnetic core with rods, primary windings arranged in the form of coils on rods and electrically isolated from them, means of forced water supply to the internal cavity of a common tubular secondary winding, having inlet and outlet nozzles and located in a magnetic field isolated from the primary windings, and covering all the core rods so that around each rod it forms closed turns located in the inter-coil space alternately one above the other and connected electrically inseparably externally in the plane of the pipe diameter parallel to the magnetic induction vector of the rod, and on the periphery remote cylindrical elements are installed in the annular space between the coils, externally connected to the coils by a permanent connection in the plane of the pipe diameter parallel to the magnetic induction vector of the rods (RU 2691726 C1, published on 18.06 .2019).

A common disadvantage of the known direct-flow steam generators is a sharp drop in the reliability of the secondary tubular winding with increasing steam pressure and especially the heating temperature. This is directly related to the design of the secondary tubular winding and is an obstacle to the creation of high-temperature devices, especially induction superheaters, since metals with high electrical and thermal conductivity are used in designs for the secondary tubular winding to achieve maximum efficiency, but such metals do not have the heat resistance and heat resistance required when operating at high temperatures. In addition, there is no protection against scale.

During the operation of superheaters and other heat engineering equipment, when using water, solid deposits form on the heating surfaces. They have high mechanical properties and low heat transfer capacity and therefore cause a number of technical difficulties and individual costs during operation.

Firstly, deposits lead to a significant waste of energy consumption and a decrease in efficiency.

Secondly, if deposits are not removed, then the operation of the apparatus gradually stops due to a decrease in the cross section of the pipes, increasing their hydraulic resistance.

Thirdly, low heat transfer leads to a strong overheating of the metal of the heating surfaces, which causes cracks, swelling and deformation on the pipes.

All this taken together leads to a significant reduction in the service life of the devices by 2-3 times.

Thus, the creation of a high-temperature superheater is possible only by radically changing the design of the heating secondary winding.

In this case, the possibility of normal long-term operation of the secondary tubular winding is achieved in accordance with the requirements imposed on it, including an increase in the operating temperature to 1000 ° C and above and the required operating pressure.

During the operation of known direct-flow steam generators, there is a sharp drop in the reliability of the pipes with an increase in steam pressure and especially heating temperature. This is an obstacle to the creation of high-temperature devices (superheaters).

The technical problem of the present invention is a significant increase in the reliability of the superheater for the production of high temperature and various pressure steam.

The technical result achieved by the invention and allowing to solve this problem is to ensure the cleaning of the surface of the tubular secondary winding and the removal of deposits during the operation of the superheater, as well as to improve heat transfer.

The technical result is achieved by the fact that in a high-temperature induction superheater containing a ferromagnetic core with at least one primary winding, a tubular secondary winding with at least one short-circuited coil, according to the invention, the tubular secondary winding is an electrogaskinetic converter of electrical energy into acoustic energy and includes an internal metal a pipe coated with a layer of high-temperature ceramic with through pores with an effective diameter of 5 to 300 nm, and a layer of heat-resistant metal over the ceramic layer, while the inner metal pipe and the layer of heat-resistant metal are connected to a source of electrical impulses.

In this case, the inner metal tube is preferably made of copper.

Further, the high temperature ceramic is a ceramic based on silicon carbide or zirconia or alumina or boron nitride.

In this case, the heat-resistant metal can be nickel, or trialuminium-niobium, or porous aluminum nickel, or porous aluminum nickelide.

The solution to the issue of protection against deposits is the most important issue associated with the operation of the superheater and the production of high-temperature steam.

Usually, to protect against deposits, preliminary softening of water (chemical, filtration) is carried out.

Known physical reagentless way to prevent the formation and removal of salt deposits in heat exchange devices by creating acoustic ultrasonic vibrations in the walls of pipes of heat exchangers and various devices for its implementation (see, for example, the article on the Internet "Description of ultrasonic technology. Recommendations for the use and selection of acoustic antiscale devices "Acoustic-T2", "Acoustic-T4", https://www.proektant.ru/content/2597.html, posted on 02/04/2013, as well as patents RU 84268 U1, RU 2350878 C2). In known devices for creating ultrasonic vibrations, an ultrasound emitter connected to a magnetostrictive transducer is welded to a pipe or tube plate of a heat exchanger.

The use of the proposed physical reagentless method of protection and removal of deposits will make it possible to solve the set tasks most effectively. The proposed invention uses an acoustic method to prevent deposits (scale), based on the electrogaskinetic effect - a method of converting electrical voltage into acoustic vibrations in a wide frequency range (the effect is described in the article Andrianov S.A. Tunnel kinetic effect. "MIS-RT" -2016 Collection No. 60-1 https://ikar.udm.ru/mis-rt.htm , in international publication WO 2008/057004, published on 05/15/2008 and in patents CN 101573189 B, published on 05/09/2012 and US 8085957 B2, published on December 27, 2011).

Under the influence of acoustic vibrations, hardness salts crystallize directly in the volume of water, forming finely dispersed sludge, and vibrations of the heating surface prevent sedimentation of sludge on the pipe walls. Therefore, the sludge is suspended and removed from the high temperature superheater during operation.

Acoustic vibrations affect the heating surface, create alternating mechanical forces, under the influence of which the strength between the deposits and the metal is broken and small defects of the continuous structure are formed. Water, under the action of capillary forces, penetrates through cracks-capillaries, where it instantly evaporates, causing swelling and flaking of deposits. The gas bubbles contained in the water, also getting into the defects between the deposits and the metal, begin to oscillate with frequency, weakening the adhesion of the scale to the metal. Exfoliated fine particles and flakes are removed in the flow. There is a cleansing and removal of deposits in the process.

Acoustic vibrations in a wide frequency range (20 Hz-150 kHz) also increase the heat transfer of the heating surface by increasing the water flow rate due to a decrease in the hydrodynamic resistance of pipes with oscillating walls (A.M. Gistling, A.A. Baram. Ultrasound in processes Chemical Technology, Leningrad, GHI, 1960, p. 67). The removal of steam bubbles from the surface of heating and degassing of water is improved due to better mixing of the near-wall liquid layer, which also contributes to an increase in heat transfer.

Pipes of heating surfaces have natural defects - narrow micron gaps and cracks, where atmospheric oxygen is stored under normal conditions. With acoustic exposure in a wide frequency range, oxygen easily escapes from these slots, as a result of which one of the mechanisms of oxygen corrosion of pipe metal is excluded. Deformation of the most pliable surface areas near microcracks also occurs. Due to these deformations, the edges of the crack are hardened, as a result of which they turn out to be closed and not subject to the penetration of oxygen into them when water is drained from the equipment. The inner surface of the pipes becomes smooth, and its total area is sharply reduced, which also leads to a decrease in the likelihood of corrosion. The resulting effect of corrosion protection to a certain extent replaces the passivation of the inner surface of the pipes.

In the proposed device, the use of the electrogaskinetic effect makes it possible to obtain steam with temperatures up to 1200°C, in contrast to the known methods of using acoustic vibrations to protect pipes from deposits, which can only provide steam with temperatures up to 200°C.

The invention is illustrated by drawings.

In FIG. 1 shows the proposed superheater.

In FIG. 2 - tubular secondary winding, axial section.

A high-temperature induction superheater (Fig. 1) contains a ferromagnetic core 1 with rods on which primary windings 2 are located. Ferromagnetic core 1 can contain one or more rods with primary windings 2. The figure shows an example with two primary windings 2.

Primary windings 2 are connected to a source of electric current. The common tubular secondary winding 3 is insulated in a magnetic field and coiled so that it covers the rods of the ferromagnetic core 1 and the primary windings 2. The secondary winding 3 has one or more short-circuited turns around each rod. Closing coils jumper connected to the inlet and outlet pipes of the tubular secondary winding 3 (not shown in the drawings).

The tubular secondary winding 3 is connected to the means for supplying water.

The function of the primary windings 2 is to generate an alternating magnetic field. Windings 2 excite a magnetic field, which, passing through the metal of the heat exchanger formed by the tubular secondary winding 3, excites eddy currents in it, which heat it up, and the heat is removed by water with forced circulation, which, when heated, turns into steam.

Tubular secondary winding 3 (Fig. 2) is an electrogas kinetic converter of electrical energy into acoustic. It consists of an internal working metal pipe 4, for example, copper, covered along the entire length with a layer 5 of porous ceramics, on top of which a layer 6 of heat-resistant metal is applied. This is the general design of the electrogaskinetic emitter of acoustic vibrations. The metal layers are electrodes that are connected to a voltage generator.

For the porous ceramic layer 5, a high-temperature ceramic, for example based on silicon carbide, or zirconia, or alumina, or boron nitride, can be used.

Nickel, or trialuminum-niobium, or alpha-tripalladium-niobium, or porous aluminum nickel, or porous aluminum nickelide, or other heat-resistant metal can be used for the outer layer 6 of the heat-resistant metal.

Layer 5 of porous ceramics is a micro- or nanoporous matrix with a system of through capillary micro(nano)pores with an effective diameter of 5 to 300 nm. The layer thickness can be from 0.5 to 300 µm.

Using various technological methods, it is possible to produce a layer with a given texture, i.e. a certain total porosity, a distribution of open and closed porosity, a certain pore size, a pore size distribution, and a pore shape. Experiments have shown that the electrogaskinetic effect takes place in through pores of any configuration and any effective diameter from the above range.

The tubular secondary winding 3 can be made, for example, of a copper pipe 3/4 EN-12735-1 19x0.89, on which a layer of porous ceramics is applied, for example, based on silicon carbide with a thickness of 0.5-1.0 mm. A layer of heat-resistant metal from the above is applied to the ceramic layer. The thickness of the metal layer can be from 0.5 to 500 microns.

Metal plates - pipe 4 and metal layer 6 are connected to a source 7 of electrical impulses, for example, a voltage converter, which can be made, for example, in the form of a high-voltage pulse generator, for example, with adjustable frequency and duty cycle, for example, in the form of an inductive-transistor blocking generator, or in the form of a high-voltage resonant Tesla transformer, and (or) reversible type, and the range of amplitude, duty cycle and frequency of these pulses is selected from the condition of ensuring maximum performance.

The proposed high-temperature induction steam generator operates as follows.

Pressurized water is supplied through the inlet pipe into the internal cavity of the common tubular secondary winding 3. Then the primary windings 1 are connected to the AC mains through outlets 8. As a result, the primary windings 2 induce an alternating magnetic flux in the rods of the core 1. Under the action of an alternating magnetic flux in the turns of the common tubular winding 3 short-circuited around each rod, a strong current is induced, which heats the tubular secondary winding 3. steam exits through the outlet pipe.

When a pulsed voltage is applied to the metal lining - pipe 4 and metal layer 6 - an acoustic field arises that affects the water.

The proposed steam generator allows you to get high temperature steam up to 1200°C. In this case, scale does not form in the tubular secondary winding.

EFFECT: invention provides increased operational reliability of a superheater for producing high temperature steam, increased service life by 2-3 times, fast and economical steam generation, simplicity and compactness of the steam generator, reduced energy consumption.

Claims (4)

1. An induction superheater containing a ferromagnetic core with at least one primary winding, a tubular secondary winding with at least one short-circuited turn, characterized in that the tubular secondary winding includes an internal metal pipe coated with a layer of high-temperature ceramics with through pores with an effective diameter of 5 to 300 nm, and a layer of heat-resistant metal over a layer of ceramics, while the inner metal pipe and the layer of heat-resistant metal are connected to a source of electrical impulses. 2. Superheater according to claim 1, characterized in that the inner metal pipe is made of copper. 3. The superheater according to claim. 1, characterized in that the high-temperature ceramic is a ceramic based on silicon carbide, or zirconium dioxide, or aluminum oxide, or boron nitride. 4. Superheater according to claim 1, characterized in that the heat-resistant metal is nickel, or trialuminum-niobium, or porous aluminum nickel, or porous aluminum nickelide.

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