Electromagnetic stirring effect and principle in aluminum refining

Today, the era of large consumption of aluminum has ushered in, and aluminum scrap has increased rapidly. Along with this, the waste aluminum containing aluminum chips has surged. Therefore, energy saving, labor saving, improvement of recovery rate, improvement of quality, etc. in the process of melting aluminum scrap, especially improving production efficiency and product quality, will become research topics.
When the aluminum scrap is melted by the reverberatory furnace, the process of the aluminum alloy into the furnace-stirring-melting-heating-recycling of the waste aluminum must be repeated for the melting efficiency.
In the melting process of aluminum, the stirring of the solution is often carried out, but it is often neglected compared with other processes. Recently, it has been recognized that the agitation method for improving the solution plays an extremely important role in rationalizing the melting operation and improving the production efficiency.
Previously stirred smelting of aluminum is achieved by a large truck and a metal rocker arm with a pump and blowing gas. In recent years, a method of stirring by a vacuum device has been employed. Various mixing methods each have their own advantages and disadvantages.
The electromagnetic stirring device described herein can overcome the deficiencies in the various methods described above. The practice of applying electromagnetic stirring has proven that it has many excellent effects.
The electromagnetic stirring effect of the solution electromagnetically agitates the metal solution in the reverberatory furnace, and generally the following effects can be obtained.
. The homogenization of the temperature of the molten metal may be carried out by a different solution agitation method depending on the internal structure of the reverberatory furnace, the amount of unmelted scrap metal, and the depth of the solution in the furnace. If the furnace is all in solution, electromagnetic stirring can make the temperature of the solution uniform in a very short time.
2. Homogenization of the solution components After performing the necessary analysis and setting an appropriate stirring time, the solution components can be homogenized.
3. Shortening the melting time Since the temperature of the molten metal in the upper and lower portions can be made uniform by the stirring of the molten metal, the amount of heat supplied from the burner to the molten metal can be increased. In addition, due to the flow of the molten metal, heat transfer from the molten metal to the scrap metal in the molten metal can be promoted, and the heating efficiency can be improved. Further, since it is not necessary to stop the operation of the burner during the stirring of the molten metal, the heating efficiency can be improved. By the above several functions, the melting time can be shortened.
4. Energy saving is different from the previously used forklift type mixing method, because the electromagnetic stirring is not necessary to open the melting furnace door, thereby reducing heat loss. In addition, since the melting can be performed at a low temperature, it is possible to lower the temperature of the gas in the furnace, thereby reducing heat loss of the exhaust gas and heat loss through the furnace wall. In addition, due to the reduced melting time, the corresponding heat loss can also be reduced. [next]
5. Increasing the yield The metal yield of the melting furnace varies depending on the material composition of the molten scrap metal, the melting method, the refining method, and the reprocessing method of the slag.
Therefore, after the electromagnetic stirring is applied, since the temperature of the molten metal in the furnace is uniform, the temperature control in the furnace is easy, and low-temperature melting can be performed. The homogenization of the metal liquid component prevents segregation. Since the metal loss is reduced after the melting time is shortened, it is expected to increase the metal yield. Further, it is possible to perform smooth agitation with less waves than mechanical agitation such as forklift type stirring, which is advantageous for reducing oxidation loss on the metal surface.
6. Increasing work efficiency The operation of the electromagnetic stirrer is extremely simple, and it is easy to stir in the necessary direction within the necessary time.
For mechanical agitation such as forklifts, mechanical installation, finishing and maintenance are required. In addition, you need to add consumables. For electromagnetic stirring, there are no consumable parts, and almost no daily maintenance is required, thus saving manpower.
Method of Setting the Electromagnetic Stirrer
The device stirs the metal solution by the action of the electromagnetic force at the bottom of the reverberatory furnace, which is a stirring device that does not contact the molten metal at all.
A non-magnetic steel plate must be provided at the bottom of the furnace of the reverberatory furnace, and a place where the electromagnetic stirrer is provided, a pit can be easily carried into the bottom of the furnace, and a stirrer is used to position the stirrer. Therefore, in the case of the original melting furnace, when the stirrer is installed, since the bottom steel plate must be replaced, the form of the electromagnetic stirrer, the installation position, and the operability of the bottom of the pit are fully discussed beforehand. To determine the location of the pit for the electromagnetic stirrer.
When the position of the
electromagnetic stirrer is selected, the type and structure of the reverberatory furnace and the purpose of use of the reverberatory furnace must be considered.
1. Type and structure of the reverberatory furnace According to its application, the reverberatory furnace can be divided into a melting furnace and a holding furnace. According to its construction, it can be divided into a closed type and an open type. According to its shape, it can be divided into square, round, cylindrical and the like. According to the solution discharging method, it can be divided into a fixed type and a tilt type.
In addition, from the point of view of its use and function, it can be divided into a rapid melting furnace and a general melting furnace.
2. Application purpose For the electromagnetic stirrer, since it uses the electromagnetic force to make the solution move, the effect should be evaluated differently for its purpose.
That is, when the pre-furnace solution in the holding furnace and the rapid melting furnace is stirred, it is the main purpose of stirring to achieve uniform temperature and composition in a short time. At this time, it is desirable to perform smooth, up and down stirring. .
Further, when agitation is used for the melting process of the waste, it is desirable to have a large circulation amount of the metal in order to achieve low-temperature melting and rapid heat exchange. Therefore, in this case, it is necessary to select the electromagnetic stirrer at a position where the molten metal is easily circulated. [next]
3. Application examples of electromagnetic stirrers in various reverberatory furnaces .
1). An application example when melting waste in a closed type melting furnace. At this time, the waste is first loaded into the reverberatory furnace. Due to the method of melting the scrap, the molten metal melted in the furnace does not reach a certain degree without using a magnetic stirrer. As the waste is continuously melted, when the molten metal is reached, the molten metal can be reached. When the cycle is carried out, the electromagnetic stirrer can be used for melting, which can promote the supply of heat to the unmelted waste in the molten metal in the furnace. Therefore, the electromagnetic stirrer should be placed at a position away from the center of the reverberating furnace, which can easily form a circulation of the molten metal as shown in Fig. 74.
2). An example of melting a scrap metal in an open melting furnace. In this case, the molten metal supplied from the outside is previously charged into the furnace, and the amount of the molten metal corresponds to 1/3 to 1/4 of the capacity of the furnace. This pre-melted molten metal circulates under the action of electromagnetic stirring force, and promotes the melting of the scrap metal in the open molten pool. Therefore, the electromagnetic stirrer should be placed slightly away from the center of the reverberatory furnace, so that the circulating flow of the molten metal shown in the drawing in the molten pool can be easily formed.
3). On the holding furnace side of the rapid melting furnace, add an open molten pool part to make it a melting furnace capable of melting light scrap metal at the same time. At this time, the plane position of the electromagnetic agitator is substantially the same as the position in Fig. 74(b).
4). In the molten pool portion for circulating the molten metal on one side of the closed furnace, a magnetic stirrer is provided at the lower portion of the molten pool portion for promoting the circulation of the molten metal and the melting of the waste.
At this time, it is necessary to add a pre-melted molten metal to the furnace, and the molten metal forms a circulating flow under the action of the electromagnetic stirrer. The heated molten metal in the furnace flows to the circulating molten pool portion, and the heat released by it is used to melt the metal scrap added to the molten pool, and the molten metal is again flowed back into the furnace to be heated, thereby forming a circulating heat exchange. To continuously melt the exhaust metal.
5). On one side of the melting furnace of the open type molten pool, a furnace for melting molten metal is arranged, and a magnetic stirrer is placed under the furnace to promote the circulation of the molten metal to melt the scrap metal. At this time, the melting of the waste material is carried out in an open molten pool, not in the molten pool for the molten metal circulation. In order to prevent heat dissipation from the circulation portion, the upper portion is covered.
In this case, since there is no scrap metal charge in the molten metal circulation portion above the electromagnetic stirrer, the flow of the molten metal in the open molten pool portion is accelerated, and it is suitable for continuous melting production of metal chips.
6) An example of setting up a magnetic stirrer in a holding furnace. For uniform stirring of the molten metal, it is effective to arrange the electromagnetic stirrer at the center of the furnace shown in the figure. In this case, since there is no scrap metal material that hinders the flow of the molten metal, the molten metal can be stirred left and right and up and down smoothly, and the temperature and composition can be quickly homogenized. [next]
4. Set the electromagnetic stirrer on the original furnace. When observing the operation of the original furnace, it can be seen that even for the same melting furnace, when the variety of the daily waste changes and the amount of feeding and the number of feedings change, the operation Conditions can also fluctuate. In addition, when a magnetic stirrer is placed on the original furnace, the amount of modification should be minimized to minimize the shutdown time. In this sense, the amount of furnace modification can be minimized, which is a method of melting electromagnetic stirring using an electromagnetic stirrer.
Improved Melting Operation In order to more efficiently and flexibly operate the electromagnetic stirrer disposed on the reverberatory furnace, it is necessary to improve the melting process of the furnace and its operation method to accommodate the operation of the electromagnetic stirrer. The melting operation process and the effects obtained are described below.
1. Improvement of the melting process and its effect (1) A magnetic stirrer is preferably provided on the closed furnace.
At this time, after setting the electromagnetic stirrer, open the furnace door, shorten the time for stopping the nozzle operation, and increase the heating time of the molten metal. As a result, the cycle time and the melting time are shortened, and the comprehensive energy saving effect is achieved. For light scrap metal materials, the effect is particularly obvious.
(2) On a closed furnace, a magnetic stirrer is used.
At this time, before setting up the electromagnetic stirrer, a large amount of chips and light scrap metal materials are added to the furnace. When the molten metal and the scrap metal in the furnace form a mixture, the forklift is used for stirring, and then heated by an ordinary heating method. . When the electromagnetic stirrer is installed, the charge is quantitatively introduced into the circulating furnace, using a melting method compatible with the heating capacity of the melting chamber, which makes the temperature in the melting chamber easy to control. Since there is almost no opening of the furnace door and the nozzle operation is stopped, the melting operation can be performed stably. As a result, the melting time is shortened, energy is saved and the yield is increased.
(3) On an open bath furnace, a magnetic stirrer is used.
In this case, before the electromagnetic stirrer is installed, the molten metal in the melting chamber is continuously sent to the open molten pool by a forklift or the like, and the stirring is performed by means of blowing air or the like, but the heat exchange effect is insufficient at this time. . After the electromagnetic stirrer is set, the heat in the melting chamber is sent into the open molten pool in the form of molten metal, and the scrap metal is supplied to melt. At this time, it is rarely necessary to open the furnace door and stop the burner, and the melting operation can be performed stably. Thereby shortening the melting time, saving energy and increasing the yield. [next]
2. Improving the operating environment For the aluminum melting operation with high labor intensity in the past, the use of the electromagnetic stirrer reduces the use of the forklift at high temperatures, reduces the amount of movement of the forklift, and reduces the consumable parts. The maintenance and repair volume can greatly improve the operating environment and provide a clean workplace.
3. Systemization of the melting operation Due to the application of the electromagnetic stirrer, it is possible to realize automatic measurement control while realizing the stability of the molten metal temperature in the furnace and the temperature of the furnace gas. In the future, it is expected that the automation and systemization of the melting operation will be rapidly developed.
In the future, the amount of aluminum scrap that needs to be melted will increase further, which depends to a large extent on the role of the reverberatory furnace. Whether it is a new reverberatory furnace or an original reverberatory furnace, it is necessary to fundamentally re-evaluate the old melting operation method and transform it into a system melting method. Especially for new furnaces, the temperature monitoring and burner control of the reverberatory furnace should be comprehensively improved, the waste heat recovery, the structure of the furnace body in which the metal liquid is stirred, the preheating of the scrap metal material and the manner of adding the charge material, etc. And quickly improve its reasonable use.
In addition, in addition to the furnace-type electromagnetic stirring device described in this paper, the electromagnetic tank type metal liquid circulating device has also entered the popular stage, which has been used for the melting of chips, the delivery and discharge of molten metal. In the future, electromagnetic stirrers should be applied more flexibly.

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