Concerning the development of an arc-type ladle heating system for foundries - Contributing to energy conservation and improvements in the work environment -
October 15, 2012
Chubu Electric Power Co.,Inc.
Chubu Electric Power has teamed up with Toyota Motor Corporation and Tokuden Co., Ltd. to develop an arc-type ladle heating system, which features energy savings, for use in foundries. In response to the excellent results yielded by the field tests undertaken recently at Toyota Motor Corporation and Aisin Takaoka Co., Ltd., the system has now been turned into a product offered for sale on the market.
Today marks the day when Tokuden Co., Ltd. will start receiving orders for the system and marketing it.
At a foundry, initially the molten metal is conveyed using a fire-resistant container called a ladle from the melting furnace, which melts the metals to the molding line where the molds are made. The metal then goes through a pouring process in which the molten metal is poured into the molds, and finally the products (castings) are removed and shipped out.
In order to prevent the temperature of the molten metal from dropping, the inside of the ladle must be preheated before the molten metal is poured in.
Gas burners are normally used for the job of preheating. However, preheating using these gas burners results in significant heat loss due to exhaust, so a great deal of time and energy are required. In addition, the temperature of the atmosphere around the ladle is raised due to the waste heat, and this has constituted another issue.
Furthermore, when periodic maintenance is performed for the ladle, the refractory materials used inside the ladle are replaced, and they are then dried by heating them at the specified rate of temperature increase in order to improve their strength. When gas burners are used for this purpose, there are significant variations in the temperature inside the ladle, resulting in yet another issue.
In contrast, the newly developed system employs an arc heating* system, which has a higher heat source temperature than conventional gas burners, and it virtually seals the ladle hermetically: as a result, the heating time has been cut and the amount of energy expended has been reduced significantly.
An additional feature is that the arc system makes it easier to control the temperature inside the ladle, so the energy loss can be drastically diminished at the dry-by-heating stage as well.
Another disadvantage with gas burners is that large quantities of exhaust heat from combustion are released inside the foundry and the temperature of the atmosphere around the ladle reaches a high level. With the arc system, on the other hand, increases in the surrounding temperature are minimized since exhaust from the combustion of fossil fuels is not generated, and the noise level can also be reduced through the installation of a heat-insulated cover. All in all, this arc-type ladle heating system contributes to improving the overall work environment.
*Arc heating involves heating using the heat generated by arc discharges, and the new system generates the arcs by applying DC current between two carbon electrodes to indirectly heat the refractory materials on the inside walls of the ladle.
Main features of arc-type ladle heating system
(1)Reduced heating times and energy savings
Use of the arc system in which the heat source temperature reaches several thousand degrees Celsius minimizes the exhaust loss, and the heat discharged from the ladle is minimized through the installation of a heat-insulated cover: the results are a shortened preheating time and dramatic energy savings. Furthermore, heating control optimizes the drying conditions, which reduces the drying time, resulting in even more energy conservation.
(2)Improvements in the work environment
The system does not release the exhaust from the combustion of fossil fuels inside the foundry, which is something that happens with heating by gas burners, so the rise in the temperature around the ladle is reduced. In addition, there used to be a lot of noise accompanying burner combustion, but the noise generated during arc heating is diminished through the installation of the heat-insulated cover, and in this way, as well, the work environment is improved.
(3)Reduction in oxides
The installation of the heat-insulated cover makes it possible to maintain a low-oxygen atmosphere inside the ladle so the amount of iron oxides left adhering inside the ladle is less, and a reduction in the oxides (waste) known as slag can be expected.