Abstract:
An electric furnace for converting fly ash into mineral wool. It is critical that fly ash for the production of mineral wool be melted and poured within critical temperature and pour rate tolerances. The electric furnace contains a product exit orifice (16), a plurality of electrodes (26, 28 and 30) located in the vessel to define primary current paths adjacent the orifice, a movable control electrode (200) is positioned for defining an additional current path adjacent the orifice and a circuit (300) for energizing the primary electrodes with multiphase current and for time-sharing the multiphase current with the control electrode. The degree of time-sharing is responsive to the temperature of the product passing through the orifice and/or the rate of flow therethrough. Also, the control electrode is positionable dependent upon the temperature of the exiting product and/or flow rate through the orifice.
Abstract:
Dans un four électrique de fusion du verre (10), l'écoulement du courant entre les électrodes est égalisé pour obtenir un chauffage régulier du verre fondu. Un premier mode de réalisation comprend: une chambre contenant une masse de verre en fusion (18), des électrodes à arc (24) positionnées au-dessus de la masse de verre en fusion et une première et une seconde électrodes (28 et 30) positionnées dans la masse de verre en fusion. Un second mode de réalisation de l'invention utilise uniquement un chauffage à résistance produit par un passage de courant égalisé entre des électrodes individuelles se trouvant dans le verre en fusion. Un troisième mode de réalisation utilise une combinaison des électrodes de chauffage à résistance et une électrode d'arc, l'écoulement du courant étant égalisé entre les électrodes individuelles. L'écoulement du courant est égalisé dans le premier mode de réalisation en fournissant une puissance électrique aux électrodes par l'intermédiaire de circuits ayant un inducteur à prise centrale, les extrémités de l'inducteur étant connectées aux électrodes et la prise centrale à l'alimentation de puissance électrique. Selon des modes supplémentaires de réalisation, les électrodes sont attaquées directement ou indirectement par l'intermédiaire d'inducteurs supplémentaires en cascade de division de courant. En établissant un passage de courant égalisé entre les électrodes ou un arc et des électrodes, l'échauffement localisé ou les points de chaleur dans la masse en fusion sont réduits.
Abstract:
A direct resistance heating method includes placing a first electrode and a second electrode such that a space is provided between the first electrode and the second electrode and such that each of the first electrode and the second electrode extends across a heating target region of a workpiece, moving at least one of the first electrode and the second electrode with an electric current being applied between the first electrode and the second electrode, and adjusting a time during which the electric current is applied for each segment region of the heating target region, the segment regions being defined by dividing the heating target region and are arranged side by side along a direction in which the at least one of the first electrode and the second electrode is moved.
Abstract:
Means for high efficiency induction heating or direct electrical heating, DEH, of a number, M, M∈ [1, N] of a group of parallel subsea pipelines N, where N∈ [2,∞), and where a number of conductor cables, W, supplies electrical power from at least one top side power supply (207, G1, G2) to M of the parallel subsea pipelines N. The numbers of electric conductors, W, from the at least one top side (207, G1, G2) power supply connected to the M pipelines is defined to be in the group W∈ [N, N + 1], where N, W and M are natural numbers. It is furthermore disclosed a system for induction heating or DEH of subsea pipelines.
Abstract:
An ohmic heater for heating a food product, comprising: - an inverter (3) comprising controlled switches (30); - a pair (4) of electrodes that can be positioned in contact with the food product to be heated, said inverter (3) being operatively interposed between a rectifier (2) of the supply voltage and the pair (4) of electrodes; - a transformer (6) located between the inverter (3) and the pair (4) of electrodes for regulating the amplitude of the voltage; - means (7) for determining the continuous component of the current in a zone downstream of the inverter (3) and upstream or at the transformer (6); - a system (800) for regulating the closing duration of the switches (30) of said inverter (3) that operates as a function of the means (7) for determining the continuous component by minimising/suppressing said continuous component.
Abstract:
Dans un four de fusion à l'arc du verre, l'électrode ou les électrodes doivent être soulevées et abaissées en fonction des conditions variables de fonctionnement du four tel que les changements de résistance de l'arc lors des variations du niveau de la coulée ou au fur et à mesure que l'électrode se consume. Un procédé et un appareil de commande de la position d'une électrode (18) par rapport à la surface supérieure (16) d'une masse de verre en fusion (12) dans un four de fusion à l'arc du verre (10) consiste à alimenter en courant alternatif d'une intensité effective constante l'électrode (18), à détecter la tension effective sur l'électrode (18), à déterminer si la tension détectée se trouve dans une plage prédéterminée de tensions, et à modifier la position de l'électrode (18) si la tension détectée ne se trouve pas dans la plage déterminée de tensions.
Abstract:
In a melting furnace forehearth, having opposed electrodes arranged in groups immersed in the melted material such that heating is produced by Joule effect, cross firing between adjacent electrode groups frequently occurs. The cross firing is reduced by connecting the opposed electrodes to a multiphase power source so that the phase relationship between groups of adjacent electrodes along the forehearth (5) is less than 90` and typically 60`. The electrode groups may be arranged along the path of molten material movement in the forehearth (5) and produce a current across the forehearth (5). The electrodes may be arranged to enter from the bottom, side or top the forehearth channel.
Abstract:
An ohmic heater for heating a food product, comprising: -a rectifier (2) for rectifying the supply voltage; - an inverter (3) comprising controlled switches (30); - a pair (4) of electrodes that can be positioned in contact with the food product to be heated, said inverter (3) being operatively interposed between the rectifier (2) and the pair (4) of electrodes; - means (5) for determining an oscillating voltage (X) generated by the rectifier (2); - a system (800) for regulating the closing duration of the switches (30) of the inverter (3) at least as a function of the corresponding voltage (X) generated by the rectifier (2) and determined at a given time instant by the means (5) for determining an oscillating voltage (X).
Abstract:
An apparatus for heating railway rails during the laying down thereof, which comprises: a group (1-5) generating a direct current, mounted on a railway car (A); a pair of first contact vices (7) carried by this railway car (A), connected to the output of the generator group (1-5) and suitable for being tightened each one on a first end of the two rails (R) forming the railway track section to be heated; a trolley (B) provided with a similar pair of second contact vices (13), connected to one another and suitable for being tightened each one on a second end, opposite the first end, of the two rails (R) forming the railway track section to be heated; and means (8-12) for controlling the electric power delivered by the generator group (1-5) in order to produce in the considered railway track section a heating up to a prefixed temperature. Preferably, the group (1-5) generating direct current comprises a motor (1), an alternator (2) moved by the motor (1), a transformer (4) for the current delivered by the alternator (2) and a power rectifier bridge (5) arranged for converting the alternating current coming from the transformer (4) into a direct current to be supplied to the first contact vices (7).