JPS58501951A - Heat recovery in aluminum melting plants - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Heat recovery in aluminum melting plants The present invention is a method for recovering heat from a furnace that produces aluminum by melting and electrolyzing alumina. The furnace gas is passed through a bed of fluidized alumina. It will be done.

The molten electrolysis method has been specially developed for that purpose and is usually made of steel. The process is carried out in a furnace configured as a trough with linings. Normal power The sword is placed at the bottom of the furnace and is made of carbon, while the anode is made of e.g. It can be of the Ku type or S'6 Derberg type, and is usually supplied to the electrolytic bath from above. be done. It wears out during the process and must be replaced continuously.

Alumina and solid attachments are fed into the electrolyte via the anode or laterally, and The aluminum obtained is extracted in patches by siphon or suction.

The gas obtained by the electrolysis, furnace gas, is carbon oxide.

It consists of a mixture of carbon dioxide, hydrocarbons, fluorohydrocarbons, etc., and is usually combined with airflow. In both cases, fluorite is released directly into the atmosphere of the space in which the furnace is located, or in the furnace gas. For the recovery of solid particles consisting of salts, some collection methods, such as metal hoods, are used. Exhaust to dust device 2 It will be done. However, the exhaust furnace gas is 80,000 tons of raw aluminum per year. energy tK phase on the order of 20 MW in a manufacturing plant for I guess.

In order to recover this amount of energy, the fluorite salt mixed in the furnace gas is separated at the same time. 2 To reduce energy losses in aluminum production during recovery, furnace gas The furnace gas passes through the alumina bed through a sump heat exchanger for heat exchange between the airflow and the outside airflow. It has been proposed to pass the furnace gas as it passes (U.S. Patent Specification Letter 3,66 No. 4,935). However, in that case the heat Exchangers clog rapidly, often requiring cleaning of the heat exchanger.

To overcome this drawback, according to the invention, around one or more tubular coils heat between the furnace gas and the outside air flow passing through the tubular coil or tubular coils at It is provided to flow the layer of alumina for exchange.

In this method, the tubular coil or a plurality of tubular coils each move the particles in the fluidized bed. Therefore, not only can the coils be blown continuously, but each of the coils may have a small surface. Therefore, it can be small and cheap for the desired thermal energy transfer. I mean This is because the heat transfer factor increases several times due to the flow.

Special edition Showa 58-5 (11951 (2) If several tubular coils are provided, they can be connected in series.

Before the furnace gas is supplied to the fluidized bed and each of the coils, the furnace gas is used for the melting electrolysis. It is particularly preferred to pass through a cathode located at. The cathode is free convection It is usually cooled by In that case, in winter, when the air is cold, the electrolytic It is necessary to compensate for significant heat losses due to increased energy supply. . Control from the cathode is provided by the furnace gas providing cathode cooling. A reduced heat transfer occurs and therefore energy consumption for electrolysis is reduced.

In order to explain the invention more clearly, a schematic vertical cross-section of the equipment for carrying out the method is shown. The following description is given below with reference to the accompanying drawings, which are illustrated in the drawings.

Furnace 1o for melting and electrolyzing alumina including an anode 11 and a cathode 12 in the nuclear diagram It is shown. A furnace feed port 13 of alumina is placed at the tip.

The furnace space is sealed and a cooling nozzle arranged around the cathode 12 is connected via conduit 14. (c) Connected to 15. The cathode is also connected to a pump 17 via conduit 16. It will be done. The furnace gas sucked from Noyaganoto 15 is jacketed between the conduits 16 and 14. There is a conduit 18 having a bond 19 returning to. Furnace 1o and jacket 15 are exposed from the surroundings. It is insulated. Furnace gas is drawn from the furnace via conduit 14 by pump 17. Via the heat exchanger tube 15 with the cathode 12 cooled as a result. be allowed to pass. Next, the further heated furnace gas is passed through the conduit by the pump 17. It is also supplied to the soil 15 via the conduit 18 by the pump 19. Ru. This device allows controlling the cooling effect and the temperature of the cathode 12. is possible. In case of excessive temperature of the anode 11, automatic reduction of cooling of the cathode correction can be obtained.

This is because the furnace gas, which acts as a cooling fluid, has a high temperature. That's it This means that the consumption of electrical energy during melting electrolysis remains at a fairly constant level at the desired production level. maintained.

The conduit 20 is connected to a container 21 in which a perforated bottom 22 is connected to the lower end of the container. and supporting a layer 23 of alumina. This is done via the inlet opening 24. and then filled into a container. The heating coil 25 for circulation of outside air has a perforated bottom. 22 above and inside the container, and at the tip the container is connected with an outlet conduit 26 . It may be of the cyclone type and has an outlet 28 for separated solid particles at its bottom. The outlet conduit 26 extends to a dust separator which is used for cleaning. Cleaner 29 is below the perforated bottom 22 and is connected to the electric drive motor 30.

It enters the vessel 10 via conduit 20 and contains some ges l- consisting of fluorite salt. Furnace gas flows through the perforated bottom 22 into a layer of alumina flowing around the heating coil 250. Enter within 23. Next, from hot furnace gas having a temperature of 200 to 220°C, , which is exchanged with an outside air flow circulating within the heating coil 25. The dust is also alumina It also adheres to. As the furnace gas exits conduit 26, some of the alumina and deposited fluorite salts enter the furnace gas. The reactor power gas leaving the main part of the heat content and removed from the entrained dust is accompanied by It is separated in a gas tanker 27 before being released into the atmosphere. The dust safety 9res The material separated in the furnace and consisting of alumina rich in fluorite salt is supplied to the furnace through the inlet 13. and is returned to the container 20 through the inlet opening 24.

The heat removed from the furnace gas by each airflow circulating from the heating coil 25 is For example, heat can be used in industrially fresh Remotely summerized to desalinate seawater or other base-containing waters in water production basins For heating, e.g. by conventional steam, barrel or two solute cycles For the production of electrical energy or suction by using e.g. freon IJ mouth fever? used in neotowers for the production of heat and/or low temperatures in be done. Combinations of these two or more uses may also be made. furnace gas The heat exchange between the air flow and the outside air flow circulating in the heating coil 25 takes place in a fluidized bed of alumina. Similarly, clogging of the heat exchanger is avoided and good heat transfer is achieved several times. Is this about it? Requires shorter equipment to process the furnace gas, thus allowing for heat recovery and fluorite salt recovery. can be carried out in one and the same device with a compact construction. Furnace gas is the method By being able to take a certain amount of heat from the cathode 12 that matches the furnace gas temperature The temperature increases and then the furnace gas is concentrated to remove all losses. The method of the invention Substantially facilitates heat recovery from the sword. Because gas aggregation/stem and furnace This is because a common heat exchanger for gas and cathode cooling is used.

Several furnaces for melting electrolysis are connected to one and the same device 21 common to all furnaces. It will be done.

Procedural amendment (formality) %formula% 1 Display of incident PCT/5E82100367 2 Name of the invention Heat recovery in aluminum melting plants 3 Person making the amendment Relationship to the incident: Patent applicant Address: 5-8-1o Toranomon-chome, Minato-ku, Tokyo 105 Date of amendment order August 30, 1981 (Shipping date) 6 Target of correction (1) Translation of drawings (2) Power of attorney and its translation 7 Contents of amendment (Engraving of the translation of 11 drawings (no changes in content) (2) As shown in the attached sheet 8 List of attached documents (1) Translation of drawing IA (2) Power of attorney and its translation, one copy each (2) international search report

Claims (1)

[Claims] 1. Melting of alumina by passing furnace gas through the alumina layer (23) in which the layer is flowing In a heat recovery method in an aluminum manufacturing furnace by electrolysis, the alumina layer is around one or more tubular coils and the tubular coil or plurality of tubes. The coil (25) is made to flow for heat exchange with the outside air flow passing through the shaped coil (25). Heat recovery in an aluminum manufacturing furnace by alumina melting electrolysis characterized by Method. 2. Furnace gas passing through the alumina fluidized bed (23) collects entrained solid particles 2. A method as claimed in claim 1, characterized in that the method is removed from the . 3. Claim 2, characterized in that the recovered solid particles are supplied to the furnace. The method described in section. 4. The furnace gas is passed through the cathode (12) for heat exchange, while the gas is passed through the bed (23) The cathode is cooled before being supplied to the The method described in Scope 1. 5. 1 to allow the furnace gas to pass through the cathode (12) again after passing through the cathode (12); 5. The method according to claim 4, wherein: ■