1. Classification by heating energy
According to different heating energy sources, melting furnaces can be divided into the following two types:
(1) Fuel heating type (including natural gas, petroleum liquefied gas, coal gas, diesel oil, heavy oil, coke, etc.), heating the charge with the reaction heat generated when the fuel is burned.
(2) Electric heating type, where the resistance element is energized to generate heat or the coil is alternating current to generate an alternating magnetic field, and the charge in the magnetic field is heated by the induction current.
2. Classification by heating method
(1) Direct heating method
The heating method in which the heat generated when fuel is burned or the resistance element is directly transferred to the charge is called the direct heating method. Its advantages are high thermal efficiency and simple furnace structure. The disadvantage is that the harmful impurities contained in the combustion products will adversely affect the quality of the charge; the harmful gases evaporated by the charge or cover agent will corrode the resistance element and reduce its service life; during the fuel combustion process, the excess air content in the combustion products is high, Causes great metal burning during heating.
(2) Indirect heating method
There are two types of indirect heating. The first type is that the combustion products or energized resistance elements do not directly heat the charge, but first heat the heat transfer medium such as a radiant tube, and then the heat is transferred to the charge by radiation and convection; the second type is generated by passing the coil through alternating current The alternating magnetic field heats the charge in the magnetic field with an induction current. Heating elements such as induction coils and charges are separated by the lining material. The advantage of the indirect heating method is that the combustion products or electric heating elements are separated from the charge without harmful effects to each other, which is conducive to maintaining and improving the quality of the charge and reducing metal burning loss. The induction heating method also has a stirring effect on the metal melt, which can accelerate the metal melting process, shorten the melting time, and reduce metal burning. The disadvantage is that the heat cannot be directly transferred to the furnace charge. Compared with the direct heating method, the thermal efficiency is low and the furnace structure is complicated.
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