FI89509C - Improvement in smelting of secondary metal - Google Patents

Description

1 395C9 Improvement in smelting of secondary metal

The invention relates to a process for smelting secondary metal, in which the secondary metal is charged to a first location in an oven and heated with a primary burner or the like, whereby exhaust gases flow from an outlet located at a second location in the furnace. The invention also relates to the corresponding furnace for smelting of secondary metal.

The furnace comprises a charging port, a burner located at a first location in the furnace and an exhaust outlet located at a second location in the furnace.

Smelting of metal waste is generally carried out by means of a rotary kiln or flame furnace, such that the furnace is charged with secondary metal until a high rises, after which the smelting takes place with a flame from a burner (gas, and yes, etc.). At the beginning of the melting before the secondary metal pretty much the melting temperature of the metal, the temperature of the exhaust gas is right. By secondary metal is meant metal waste such as scrap, old electrical components, etc.

If the metal waste hereby contains organic material such as plastic and rubber, which is very common, a pyrolysis of this takes place. Where the gas temperature on the back of the metal waste pile is relatively low and where oxygen deficiency can also occur, some unburned material will be fed to the gases. Although from the leakage resulting from the false air later being supplied to the gas, the unburned material will not be oxidized due to. the low gas temperature. This generation of exhaust gases with unwanted unburned material takes place over a shorter or longer period of melting, depending on the raw material used and the way of charging the furnace.

Normally, the furnace system is provided with a gas treatment system to purify the gases from sublimate and dust and often also to purify the gases from acidic components 2 β 9 5 C 9 such as SO 2, HCl, HF, etc. This system usually comprises admixture. of lime, calcium hydroxide or sodium compounds, which react with the acidic components and then are separated by filters together with the solid dust from the furnace. The filter destroys separating the unburned material, soin is in solid or liquid form, but not gaseous celate.

The problem underlying the invention is that pyrolysis of metal wastes containing organic material produces unburned volatile material, which pollutes the environment. For example, the German standards are mentioned, which allow a quantity of unburned material in exhaust gases of no more than 50 mg C / Nm3 gas. This low value is easily exceeded in the melting of metal waste such as aluminum scrap.

It is previously known to equalize the combustion temperature in melting furnaces throughout the charge using suitably located secondary burners and separate pyrolysis burners (DE-1 227 042, DE-1 508 254 and DE-3 228 432). On the other hand, it is known to insert additional burners into a separate combustion chamber for the exhaust gases from the metal waste burning (Koch, M., Taylor, J.C., Productivity and Technology in the Metallurgical Industries, the Minerals, Metals and Materials Society, 1989, 475) . The object of the present invention is to provide an even heating of metal waste for its melting. The invention also seeks to efficiently purify the exhaust gases generated when heating metal waste. The meal is also used to utilize the heat value of said exhaust gases for heating the metal waste. Last but not least, a practical way of combining these three aims is sought.

The above-mentioned drawbacks have been avoided and grinding has been achieved by the process and furnace according to the invention, the features of claims 1 and 7. According to the invention, a furnace for smelting secondary metal is thus provided with a secondary burner at the outlet 3/9. 509 of the oven. The position of the secondary burner is so directed to the contents of the furnace that a simultaneous and proper mixing of the exhaust gases and the flame is achieved. The exhaust gas temperature from this stage of the melting will rise, but at the same time a more intense melting process is obtained as the back of the scrap heap also participates in the melting process and thus shortens the melting time. About larger amounts of organic matter! is present at the melting and thereby pyrolyzed, the heat value in the pyrolysis gas can be utilized in this secondary combustion.

The present invention is suitable for all types of metal waste which, when heated, emit contaminating exhaust gases.

Examples include various types of scrap such as copper, aluminum, lead and possibly iron scrap. Depending on the quality of the secondary metal, it should be noted that the more effective the invention, the more volatile and combustible waste arises during heating.

The invention is particularly well suited for the treatment of PCB-containing secondary metal, such that the metal is melted and the PCBs destroyed. In this case, the furnace is preferably provided with an afterburner which gives a sufficiently high temperature. 1100 ° C, and sufficiently long residence time for complete degradation of the PCB material.

According to the new method, metal waste is charged to a furnace and heated there with a primary burner or the like located at a first location in the furnace. The waste is preferably charged to said first location in the furnace, the charge opening being advantageously utilized to introduce the primary burner.

To effect the heating of the metal waste, the furnace may be rotated if necessary.

The exhaust gases generated by heating the metal waste are led out of the furnace through an outlet located at another 4> .9 9 9 9 location in the furnace. The outlet is thus placed so that it does not saroinani all with the primary burner.

The improvement has been made so that at said second location 5 in the furnace, where the exhaust gas outlet is located, a secondary burner is placed, which in this position heats the metal waste and combustes the effluent exhaust gases. In order to improve combustion efficiency, the secondary burner is preferably measured with an excess of air and / or oxygen.

Thus, at least the secondary burner operates with an excess of air and / or oxygen, such that the unburned material from the pyrolysis is incinerated at the same time as the exhaust temperature is raised to the required level.

15

The invention also relates to a furnace for smelting metal waste. It includes a charging port, a primary burner located at a first location in the furnace, and an exhaust outlet located at a second location in the furnace. The charge opening is preferably located at the first location of the furnace, the primary burner being heist inserted into this opening. The furnace improvement consists of a secondary burner, which is located at the exhaust outlet at the second location of the furnace. According to an embodiment suitable for non-elongated furnaces, the secondary burner has been placed in the furnace exhaust opening, where it is best when contacted with the exhaust gases and at the same time sufficient to heat the secondary metal from another furnace. In particular, such a structure is suitable for short rotary kilns, the ends of which are said one and the other place and where the metal waste can be heated in its entirety through said openings.

The invention is further illustrated by the following figure, which shows a short rotary furnace to which the invention has been applied.

The refractory rotary furnace 1 according to the figure is provided with a primary burner 2 at a first location in the furnace, which is constituted by its charging opening 3. An exhaust outlet 4 is arranged at a second location in the furnace 1, where also a secondary burner 5 ή 9 5 ϋ 9 is introduced through said exhaust outlet 4. The secondary burner 5 heats and combustes the exhaust gases simultaneously as it contributes to heating the secondary metal 6 in the furnace 1.

5

The short rotary furnace 1 is rotated by rotary means 7. The primary burner 2 and the secondary burner 5 are arranged on respective carriages 8 and 9 or by other means, by means of which they can be moved in the axial direction of the furnace 1 and thereby introduced into the furnace and brought to the desired position. distance from the secondary metal 6.

The embodiment of the process according to the invention shown in the figure is initiated by charging the secondary metal 6 to the furnace 1 through the charging opening 3. Then the charging opening 3 and the primary burner 2 and the secondary burner 5 are introduced through separate openings at the oven's charging opening 3 and exhaust outlet 4. The burners 2 and 5 are preferably effected by pushing the corresponding carriages 8 and 9 or the like on which the burners 2 and 5 are mounted.

After charging and insertion of burners 2 and 5, these were ignited. As the temperature rises, the volatile components initially settle out of the batch. These may consist of any moisture and solvents, but also small molecular additives in plastic and rubber. Scrap of electrical material such as capacitors may also contain superoxides such as PCBs, whose combustion is necessary for environmental reasons.

As the volatile components have dispensed, a pyrolysis of macromolecular material present in the secondary metal, such as plastic and rubber, begins. In the pyrolysis, volatile organic material is produced, which normally settles as a component of the exhaust gases. In the furnace 1 of the present invention, on the other hand, a purification of the effluent exhaust gases takes place so that the volatile pyrolysis material leaving the secondary metal 6 is burned by the burner 5, where it 6> 95.9 flows out through the exhaust outlet 4. The furnace can be rotated by means of the heating. the rotary means 7. The secondary burner 5 also allows for melting of the secondary metal 6 in the form of a pile immediately after charging and before the rotation the secondary metal pile 6 is smoothed along the bottom of the furnace 1.

The secondary burner 5 may, if necessary, be provided with a directional nozzle as shown in the figure. In this way, the position of the burner 10 can be directed in the desired manner towards the secondary metal. The principle is that the secondary burner is directed so that a proper mixture of combustion gases and the flame from the burner is achieved. The secondary burner can also be inserted obliquely in relation to the axis of the rotary furnace and thus optimally directed towards the secondary metal. Such a secondary burner 5 'is shown in dotted lines in the figure. The primary burner 2 and the secondary burner 5 preferably operate with air and / or oxygen excess such that the unburned material from the pyrolysis is burned at the same time as the temperature of the gas 20 is raised to a required level. After burning away the impurities, the secondary metal 6 is melted, the secondary burner 5 contributing to an even melting of the metal. At the end of the melting, the metal is drained and burners 2 and 5 are withdrawn for new charging of the furnace.

Claims (11)

A method for melting a secondary metal (6), wherein the secondary metal is fed to the first location (3) of the furnace (1) and heated therein by a primary burner (2) or the like, the exhaust gases flowing from the outlet (4) in the second location (4) of the furnace (1) , characterized in that a secondary burner (5) is arranged at the second point (4) of the furnace, which heats and burns the exhaust gases while heating the secondary metal (6). A method according to claim 1, characterized in that the furnace is rotated to equalize the heating of the secondary metal. Method according to Claim 1 or 2, characterized in that an excess of air and / or oxygen is fed to the secondary burner. 9,49519 Method according to one of the preceding claims, characterized in that the furnace (1) is connected to at least one afterburner via a discharge opening (4). Process according to Claim 4, characterized in that the furnace and the afterburner are kept at a temperature α of 1100 ° C for melting and burning the PCB-containing secondary metal. A furnace for melting secondary metal, comprising a feed opening in the first point (3) of the furnace 10 (1), a primary burner (2) in said first point of the furnace (1) and an exhaust outlet in the second point (4) of the furnace (1), characterized by a secondary burner ( 5) located next to the exhaust outlet of the second point (4) of the furnace. 15 Furnace according to claim 6, characterized in that the first (3) and second (4) sections of the furnace (1) are provided with respective supply and exhaust openings, said primary burner (2) and secondary burner (2) being arranged in these openings, respectively. 5). Oven according to claim 6 or 7, characterized in that it is a short rotary kiln (1), the ends of the cylindrical casing forming said first (3) and 25 second (4) points. Furnace according to one of Claims 6 to 8, characterized in that the secondary burner (5) is provided with a means for increasing the excess air and / or oxygen. 30 Furnace according to one of Claims 6 to 9, characterized in that the discharge opening is connected to an afterburner. Use of a furnace according to any one of claims 6 to 10 for treating a PCB-containing secondary metal by melting the metal and destroying the PCBs.