The preheating furnace is divided into two stages: wood (heavy oil or coke is also used) and electric baking. The main purpose of the former is to bake the electrodes in preparation for electric baking. The latter is for drying the furnace lining body, coking the electrode paste in the carbon brick seams and raising the temperature of the furnace lining, and preparing for the furnace opening.
The quality of the furnace is directly related to the service life of the furnace lining and whether the feeding is normal or not. It can be seen that the preheating furnace is a very important process.
The following preparations should be made before preheating the furnace:
1. Install the electrode shell and put electrode paste with a particle size of 50 to 70 mm into it. The amount of electrode paste is usually controlled to the height of the paste column to 2 meters above the copper tile. After installation, cover it with a wooden cover to prevent dust. fall into. During the electrode baking process, as the surface of the paste column decreases, additional electrode paste must be added accordingly.
2. Place the electrode on the 65 mm thick layer of clay bricks laid on the bottom of the furnace. The length of the working end of the electrode should exceed the upper edge of the furnace mouth by approximately 100 to 200 mm. A layer of coke with a thickness of about 100 mm and a particle size of 40 to 50 mm is spread on the bottom of the furnace.
3. Adjust the centerline of the electrode so that the pressure of each copper tile on the electrode is balanced.
4. The water cooling, conduction and hoisting systems were tested normally.
wood preheating furnace
The time required for a wood preheating furnace depends on the electrode diameter (or furnace capacity), and is usually no less than 24 hours. When the electrode on the upper edge of the copper tile is pierced with an iron solder and the paste does not flow (in a plastic state), it means that the wood preheating furnace can be completed. The flame of the preheating furnace should be shorter in the early stage and longer in the later stage. It is best to exceed the electrode holder. Cooling water should be reduced to a minimum. The fan should be turned on and off to keep the electrode paste on the surface from being completely melted and not affecting the electrode roasting. The amount of wood required for a preheating furnace depends on the size of the furnace, generally 20 to 70 tons.
Electric preheating furnace
1. The following tasks should be done before using the electric preheating furnace:
(1) Remove the wood ash from the furnace, and then lay a layer of coke with a thickness of about 250 to 300 mm and a particle size of 25 to 40 mm.
(2) Tight copper tiles.
(3) Recheck whether the water cooling, conductive and hoisting systems are normal.
2. Use a lower voltage and lower the electrode after energization to make it in contact with the coke. In order to stabilize the load, you can add some coke around the electrode and form a cone. The power supply system is carried out according to the compiled power supply system table. The basis for formulating the power supply system is:
(1) Depending on the size of the furnace, the electric preheating time is 30 to 50 hours, and the total power consumption is 20,000 to 100,000 degrees.
(2) The current rises slowly during the electric preheating process, and the maximum current at the end of the electric preheating period should not exceed 50% of the rated current.
3. During the electrical preheating process, there should be as few moving electrodes as possible and the load balance of each phase should be maintained.
4. When the electrode suddenly emits a large amount of yellow smoke, the load should be reduced.
5. When the gas discharged from the ventilation holes of the furnace lining can be ignited and the temperature of the furnace shell reaches 70~80℃, the electric preheating can be completed.
