Brown corundum Smelting process method and characteristics:
(1) Process characteristics: (1) Furnace temperature > 2050 °C. (2) Charge level in the furnace: upper solid layer, middle semi-molten layer, lower molten layer. (3) Electric energy distribution in the furnace: arc heat, resistance heat. (4) In the smelting process, the melting depth and melting area are ensured at any time by controlling the power, batching ratio and material layer thickness.
(2) Process method:
Oven method (submerged arc method):
Features: (1) The furnace with thick material layer and capacity of 1800~2500KVA, the initial thickness is generally about 600~1000mm; The initial thickness of furnaces below 1000KVA is generally about 400~600mm. (2) The granularity is large. (3) The arc is completely covered by the material layer.
Advantages: (1) High heat utilization. (2) The loss of electrode and furnace lining is small, and the degree of high temperature radiation of the upper equipment of the furnace body is small. (3) Reduce the harm of radiant heat to workers.
Disadvantages: (1) There are many recycled materials in the fixed furnace, the consumption of raw materials increases, and the amount of labor is large (little impact on the dumping furnace operation). (2) The hourly feeding amount is large, the operation is improper, the melting speed of the melt is fast, the heat source center is moved up, and the molten pool area is small. (3) Easy to cause spray oven. (4) The fixed furnace is easy to produce the phenomenon of mixed corundum and ferrosilicon or uneven quality of various parts of the frit.
Open furnace method (open arc method)
Features: thin material layer, fine particle size, long arc exposure time, material layer thickness is generally 300mm.
Advantages: (1) High charge utilization rate. (2) The molten pool temperature is high and the melting area is large. (3) The molten viscosity is small, the ferrosilicon alloy is easy to be separated centrally, and the mass of the frit is uniform.
Disadvantages: (1) Low heat utilization. (2) Long smelting time and low production efficiency. (3) The furnace lining and electrode oxidize quickly, and some equipment is often in the high temperature radiation area, which affects the life. (4) The environment in front of the furnace is poor.
General operation process of brown corundum smelting:
(1) Preparation before opening the furnace: (1) Connection electrode: blow static contact surface and tighten the thread. (2) Adjust the length of the electrode: the electrode is in contact with the arc coke, which does not affect the entry and exit or dumping of the furnace body. (3) Measure the distance between the electrode and the distance between the electrode and the furnace wall. (4) Measure secondary conductive system insulation: the resistance value of the insulation part > 0.5MΩ. (5) Check the furnace body transmission, electrode lifting, feeding and other system equipment, water, gas pipes, valves, etc.
(2) Open furnace: (1) Place the starting coke: the starting coke particle size is 30~50mm. There are three placement methods: solid triangle: the amount of starting arc coke is large, it is not easy to break the arc, and it is used in the middle. Hollow triangle: the amount of arc starting coke is small, easy to break the arc, not commonly used. Crystal shape: small amount of arc starting coke, fast arc starting, easy to break arc, for furnace opening.(2) Power transmission: (3) arc starting: using higher voltage, when the current rises to 20~30%, increase the block of bauxite pressure arc, when the current load rises to 80%, it can be added to enter the smelting.
(3) Smelting: mainly divided into two processes: the stewing furnace method and the open furnace method (see the third point brown corundum smelting process method and characteristics) for “control” operation and furnace condition analysis.
(4) Control: generally stop feeding, control the electrode to rise, and small reactions are not processed. The resulting reaction block or “snort” post-processing. In case of levitation.
(5) Refining: (1) Before transferring to refining, adjust the ingredient ratio and appropriately increase the amount of carbon. (2) Stop feeding, thin material layer, low voltage, high current operation.
(6) Pour (out) furnace: (1) Start the electrode first, and then stop the electrode when the current is not less than 5000A. (2) The dumping furnace prepares the package 0.5h in advance and turns off the cooling water. (3) When pouring, follow the principle of first slow and then fast, and finally slightly slower. (4) Leave a little melt liquid to facilitate the next arc start. (5) Pay attention to the pouring angle to prevent the furnace nozzle from touching the crimping package. (6) After the resetting is reversed, when the electrode is 200~500mm away from the molten liquid, start to send electricity.
(7) Precautions: (1) Smelting process, no abnormal phenomenon, send full load as required, and reduce the number of electrode activities. (2) The furnace is not unloaded for a long time, and the movable electrode can be forcibly unloaded for 30~40min. (3) After the electric furnace is destroyed by the large reaction equipment, or the power outage time is long, pay attention to the active electrode. (4) The electrode is glued and should be raised first. (5) Concentrate on running at full load according to the process.
5. Smelting process operation method:
(1) Arc starting: that is, the method of using carbon material as conductor arc initiation when opening the furnace; Operation points: pendulum method of arc starting coke; Higher voltage is adopted, and after the current rise is stable, it is gradually put in to prevent arc breakage.
(2) Oven: that is, the material layer is thick, generally in 0.4-1M arc opaque, high heat utilization; operation essentials: use gap feeding, regular oven cooking, cooperate with “control” operation. Deflate regularly to avoid excessive air pressure and causing the blast oven. Less electrode movement, balanced and full load power supply. The lumpiness of bauxite is < 30mm, and the amount of fine powder is small.
(3) Control: Essentials: Do not add or add less material within a certain period of time, promote the electrode to fall, expand the molten pool area, and increase the melt temperature. Operation method: control feeding, control electrode rise; Generally, small reactions are not treated; The batching layer is lowered, the melt fluidity is good, and the current is unstable and can be transferred to feeding smelting.
(4) Gassing: a large amount of CO gas is generated due to the reduction reaction process, which must be eliminated to prevent large spray furnaces; Operation specifications: the thickness of the material layer, the degree of the melt block should be appropriate, and the air permeability should be maintained; When holes are formed due to the furnace during the simmering period, after the gas runs clean, the cover is plugged with a large block of waste material;
(5) Furnace waste material addition: mostly added in layers with bauxite mixture in the middle of smelting, and added to the melting area of the furnace.
(6) Use of micronized powder in the furnace: when the collapsed hole exposes the liquid surface, first cover the micronized powder to form a hard cover before adding materials; When the material layer appears sintered, it is used to pour it into the solution surface; Add the middle of the three electrodes before stopping the furnace, or pour it in from the electrode root.
(7) Feeding: that is: passing the surrounding charge to the center; In the control and refining phase, the surrounding hot charge is gradually pushed towards the high temperature area.
(8) Pounding: the material layer sintering is serious and the charge sinks; Method: When other measures are ineffective, the furnace can be unloaded; Raise the electrodes, item by item; Overflow the molten liquid, cover with micronized powder, and then stir.
(9) Refining: stop feeding until the charge is melted; Operating specifications: lower voltage; Frequently move the electrode to pat the charge to prevent sintering; Brush the surrounding charge towards the center and gradually melt clean.
(10) Stop the furnace: after melting, the power can be cut off for about 30min after refining; Operation essentials: the electrode can be covered with micronized powder; Stick sticks often to ensure that the quality of the three phases is similar;
Normal situation of furnace shutdown: white-blue flame comes out of the electrode head; The arc is long and extremely unstable; The current is unstable, and a soft cover appears on the liquid level.
