FR2461425A1 - On-line heating of liquid and viscous material - uses electrical heating plates to define flow channel and is esp. for concrete - Google Patents

Abstract

or continuous electrical heating is applied to the flow of completely liquid or viscous materials esp. concrete. Heating occurs within a cylinder the subject material entering and leaving from opposite ends. The tube shell (1) consists of an electrically insulating material carried on a frame (11) in which the three-phase electrical controls (13) are housed. The tube has a symmetrical Y-shaped channel (15) running along its length defined by three electrical heating plates (14) folded along their centre line to an angle of 120 degs. their edges being attached to the tube inside surface. The triangular form is tapered by insulating profiled pieces to guide the material into the central channel. An insulating section maintaining the channel shape is set between the electrodes and at the exit end of the channel.

Description

The present invention relates to the continuous heating of liquid and pasty products which conduct electricity. It applies more particularly to the preheating of concrete.

 It is known in fact that the preheating of the concrete allows a faster formwork release of the concrete poured into formwork, which has many advantages, hence the economic advantage of the concrete preheating devices.

The applicant described, in its patent application No. 77 or 821 of March 24, 1977 and the first certificate of addition No. 79 074bu Or 'March 15, 197th to this patent application, concrete preheating devices. It was a batch preheating in a bucket or tank previously filled with concrete.

 According to the invention, the continuous heating of a concrete flow is carried out. which conducts electricity, or another liquid or pasty product which conducts electricity.

A device according to the invention comprises, in combination
- A tubular element, made of an insulating material with respect to electricity and open at its two ends, one of the ex ends constituting an inlet opening through which the product to be heated arrives, while the second end constitutes the outlet opening for the heated product,
elongated parts made of an electrically conductive material and arranged inside this tubular element; and
- Means for bringing these parts to different potentials to ensure the passage of electric current through a product to be heated circulating in said tubular element between its inlet opening and its outlet opening, and therefore heating by Joule effect of this product.

 There are generally three elongated parts supplied with three-phase or two elongated parts supplied with single phase.

 Preferably, the tubular element is of revolution about an axis and the device comprises three elongated parts, substantially identical, arranged symmetrically around the axis of the elongated element and bent at 1200, so as to leave a section Y-shaped passage for the product to be heated.

The surface of this Y-shaped section is advantageously identical to the surface of the section of the product supply pipe to
said inlet opening in order to avoid pressure variations.

The elongated parts constituting the electrodes are held in position, inside the tubular element, by insulating parts and are thus perfectly electrically insulated from the outside of this tubular element or -tube.

 At the ends of the tube, connection pieces are preferably provided allowing the connection of the tube to the product supply pipe at the inlet and to the spreading pipe (in the case of concrete) at the outlet.

Such connecting pieces are conductive and grounded to channel into the ground; leakage currents
Between these connecting pieces. of cylindrical section and the channel located between the Y-section electrodes, pieces of electrically insulating material are advantageously provided to serve as a guide for the product and to ensure a constant surface for the passage of the latter.

In a simplified version, these guides can have a form of funnel directing the product to be heated from the inlet opening of the tubular element to the upstream end of the channel.

 Between the pipe bringing the product to be heated and the pipe, an additional relatively fragile piece can be provided, forming a valve and intended to prevent incidents in the event of jamming or blockage inside the pipe.

 The electrodes are preferably supplied with three-phase current.

Of course, it is possible to foresee means of regulation, for example with thyristors or autotransformers. to adjust the degree of heating of the product in, the device, - in. flow rate function
and the nature of the product and the import; porta-nce of heating to be achieved.

The invention may, in any case, be well understood with the aid of the additional description which follows, as well as of the appended drawings, which supplement and drawings are, of course, given mainly by way of indication. - -.
Figure 3 illustrates in elevation; the entire device equipped with improvements according to the invention.

 Figure 2 shows this dispos-itif.-longitudinal section.

Figure 3 illustrates in perspective and with / partial cutaway, the guides bringing the product. to be heated between the electrodes.

 Figure 4 shows in cross section the arrangement of the conductive parts of the device.

 Figures 5 and 6 illustrate, in perspective, shims for positioning these conductive parts.

 FIG. 7, finally, schematically illustrates, in section, the arrangement of the two electrodes or elongated parts in the case of a device according to the invention supplied with single phase.

According to the invention and more particularly according to that of its modes of application, as well as according to those of the embodiments of its various parts, to which it seems that there is reason to grant
preferably, proposing, for example, to produce an electric heating device, continuously, of an electrically conductive liquid or pasty product, in particular concrete, this is done as
follows or in a similar manner.

 Referring first to Figures 1 and 2, we see that the device according to the invention firstly comprises an elongated element or tube 1, not electrically conductive. made for example of polyvinyl chloride.

This tube has an inlet end 3 and an outlet end 4, respectively to receive the product to be heated and to evacuate this product once heated: the product to be heated is delivered by a pump (not shown) which sends it by a pipe of which the downstream end has been shown 5. A safety piece 6 constituting a valve connects this end 5 to the inlet 3 of the tube 1. or more exactly to a conductive piece 7 constituting a connection and fixing the mass for the device. A similar conductive part 8 is also provided at the outlet 4 of the tube 1, this part 8 making it possible to connect the outlet 4 of the tube to a discharge or spreading pipe 9.

The tube 1 is carried, from the ground 10, by feet II; a shelf 12 carries an electrical supply, regulation and protection cabinet 13, including the four output cables 13a,
13b are joined respectively one 13a to the neutral of the three-phase system (parts 7 and 8) and to earth and the other three 13b to the three conductive parts or heating electrodes 14.

Referring now to Figures 3 and 4, we see that these parts 14 are constituted by folded conductive sheets, having a very open V-section, the opening angle being 1200
(figure 4).

The fluid to be heated flows from left to right
(in the direction of the figures), i.e. in the direction of the arrow
F, in channel 15, the section of which has the shape of a star at
three branches or a Y (Figure 4).

Wedges 16a, 16b, 16c made of insulating material (Figures 2, 3 and
4) hold the electrodes 14 in position.

Finally, there are provided upstream of the wedges 16a curved parts
17, of substantially triangular profile, forming between them a funnel directing the product to be heated from the upstream part 18 of the tube 1 towards the inlet 19 of the channel 15.

The operation of the device is as follows.

 The product to be heated arrives through the end 5 of the pipe and, after passing through the valve 6 (which serves as a safety valve in the event of blockage or stuffing of the product inside the tube 1, in particular in the channel 15), it reaches the interior of tube 1 in zone 18; it is directed by the triangular pieces 17 towards the channel 15 which it traverses from left to right (sense of the figures). The product between the electrodes is traversed by electric currents and is heated by the direct Joule effect.

are
The three electrodes 14 / supplied in three phase from the cabinet 13, which may include regulation means, in particular with thyristor or autotransformers, depending on the flow rate and the nature of the product and the temperature increase to be made undergo the product. The heated product leaves the channel 15 and ends up in the zone 20 which it leaves via the outlet 4. The parts 7 and 8 located at the neutral of the three-phase system for supplying the electrodes also fix the mass of the system to earth. It is possible to provide, between the downstream end 21 of the channel 15 and the outlet 4, an inverted funnel constituted by parts (not shown) such as the curved triangular parts 17. but oriented in opposite directions.

 The device which has just been described has numerous advantages.

 Heat is generated within the product itself, resulting in very high energy efficiency.

Heating takes place continuously, which is an economic advantage and makes it possible to achieve homogeneous heating over time.

Heating is almost instantaneous: only the volume located inside the device is lost on start-up, this volume of product not having been correctly heated.

 The product is gradually and uniformly heated during its movement in the tube. The fact that there is no local overheating may be advantageous for the heating of food products (milk, etc.).

 The device according to the invention applies to the heating of homogeneous or heterogeneous products of the concrete type, the preferential current lines being reduced by the circulation of the fluid.

The electrical power called is continuous (no-flicker) and it is relatively constant and independent of variations in the resistivity of the product as a function of temperature.

The currents per phase are balanced.

The equipment is simple and robust enough to be installed on a site.

The invention is particularly applicable to the heating of concrete (resistivity generally between 300 and 1000 Q cm). but it also applies to the heating of other products, homogeneous or not,
Electricity conductors.

The following tests were carried out with the device which has just been described.

The circulation of concrete in the heating tube was obtained by a concrete pump powered by a router.

 The concrete used was a CPJ 45 dosed at 350 kg, the aggregates 0/10 and the slump of 12 cm.

The results obtained with electrodes of one meter show that the power called is of the order of 150 kW, thus making it possible to raise 12.3 m3 / H of concrete of 160C or to raise 3.3 m3 / h of 4B C concrete.

To check the mechanical characteristics in compression of the concrete, twelve cylindrical test specimens were prepared, as well as four parallelepipedic blocks, for resistance measurements by the method of the speed of sound.

 The results at twenty-eight days curiously show no difference in mechanical strength between the test specimens of heated concrete and the control specimens of unheated concrete, whereas traditionally the values are reduced by 10-15% whatever the mode of heating.

It should be noted that the concrete used was relatively soft and electrically conductive. In less favorable use, it may be necessary to put two or more heating tubes according to the invention in series.

As goes without saying and as it already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all its variants.

Thus, in the case of a single-phase supply, the device which is the subject of the patent only comprises flat heating electrodes 14 ′ placed in a tubular element 1 ′, preferably of rectangular shape, and surrounding the channel 15 ′ (FIG. 73.

Claims (14)

1. Electric heating device, continuously, of a liquid or pasty product, electrically conductive, characterized in that it comprises, in combination - A tubular element, made of an insulating material with respect to electricity and open at its two ends, one of the ends constituting an inlet opening through which the product to be heated arrives, while the second end constitutes the opening outlet for the heated product;  - elongated parts made of an electrically conductive material and arranged inside this tubular element; and - - means for bringing these parts to different potentials to ensure the passage of electric current through a product to be heated circulating in said tubular element between its inlet opening and its outlet opening, and therefore the heating by Joule effect of this product.  2. Device according to claim 1, characterized in that the tubular element is of revolution about an axis. 3. Device according to claim 1 or 2, characterized in that the device comprises three elongated parts, substantially identical, arranged symmetrically around the longitudinal axis of the elongated element and folded at 1200, so as to leave a passage section Y-shaped for the product to be heated. 4. Device according to claim 3, characterized in that said Y-shaped section is identical to the surface of the section of a product supply pipe to said inlet opening in order to avoid pressure variations.  5. Device according to any one of the preceding claims, characterized in that said elongated parts constituting electrodes are held in position, inside the tubular element, by insulating parts and are thus perfectly electrically insulated from the- outside of this tubular element. 6. Device according to any one of claims 1 to 5, characterized in that provision is made, at the ends of said tubular element, for connection pieces allowing the connection of the latter to a pipe for supplying the product to the inlet and possibly a spreading hose at the outlet.  7. Device according to claim 6, characterized in that said connecting pieces are conductive and earthed to channel in the ground all the leakage currents.  8. Device according to claim 6 or 7, characterized in that between the connecting pieces and the channel located between the section electrodes in, Y. parts of electrically insulating material are provided to serve as a guide for the product and to ensure a constant surface for the passage thereof.  9. Device according to any one of claims 6 to 8, characterized in that said metal parts have the form of a funnel directing the product to be heated from the inlet opening of the tubular element to the upstream end of the canal. 10. Device according to any one of the preceding claims, characterized in that there is, between the pipe bringing the product to be heated and the tubular element, an additional fragile piece, forming a valve and intended to prevent incidents in the event of stuffing or plugging inside the tubular member.  11. Device according to any one of claims 1 to 10, characterized in that the supply of said elongated parts is done by three-phase current. 12. Device according to any one of claims 1 to 10, characterized in that the supply of said elongated parts is done by c-current single-phase.  13. Device according to any one of the preceding claims, characterized in that it comprises regulation means, in particular with thyristors or autotransformers, for regulating the degree of heating of the product in the device, according to the flow rate and the nature of the product and the importance of the heating to be carried out. 14. Device according to any one of claims 1 and 3 to 13, characterized in that the tubular element is of rectangular section and that said elongated parts are flat.