Paper
Knowledge ｜ judgment of electrode and charge in submerged arc furnace production
Updated: 2022-04-26 Attention:
Why are electrodes required to be inserted deeper into the charge?
The charging with deep electrode can improve the furnace temperature and expand the crucible, which creates the necessary heat conditions for the full smelting reaction. Therefore, the deep insertion of electrode into charge is an important link in smelting operation.
When the electrode is inserted deep into the charge, the heat loss is less, the furnace temperature is high, the crucible is large, and the chemical reaction speed in the furnace is fast, so the iron tapping is large and the unit power consumption is low. On the contrary, when the electrode is inserted into the charge shallowly, there will be more stabbing and material collapse, large heat loss, low furnace temperature and insufficient reaction. Therefore, there will be no better technical and economic indicators.
It is mainly related to the depth and capacity of the smelting furnace.
According to practical experience, when smelting 75 ferrosilicon, the electrode insertion depth of large capacity furnace is generally 1000-1200 mm, and that of small capacity submerged arc furnace is generally 700-1000 mm. The electrode insertion depth of smelting 45 ferrosilicon submerged arc furnace with large capacity is generally 800-1000mm, and that of furnace with small capacity is generally 500-800mm.
What are the factors affecting the insertion depth of electrode?
1. Coke addition
Coke is more conductive than silicon. If too much coke is added, it will affect the deep insertion of the electrode. Therefore, under the condition of sufficient reduction of carbon dioxide in silica, coke should not be added too much to facilitate electrode insertion.
2. Coke particle size
If the particle size of coke is small, the surface area increases, the contact surface is increased, and the resistance of charge is large, the electrode insertion is deep; On the contrary, if the particle size of coke is large, the surface area is reduced, and the resistance of charge is small, the insertion depth of electrode becomes shallow.
3. Coke properties
Here mainly refers to the resistance of coke itself. If the resistance of coke is small and the current through the charge is large, the electrode will rise and the insertion depth of the electrode will be shallow. On the contrary, coke has high resistance, such as using gas coke. Because of its high resistance, the electrode can be deeply inserted.
4. Secondary voltage
When the smelting adopts higher secondary voltage, the arc is longer and the electrode is inserted shallowly in the charge. On the contrary, with a lower secondary voltage, the electrode will be inserted deeper into the charge.
5. Operation
If the operation is improper, such as uneven mixing and partial feeding, do not tamp the furnace in time. Sticky furnace conditions, high charge level or lack of charge in the furnace will hinder the depth and stability of electrode insertion into the charge.
⒍ tapping time
Under normal furnace conditions, if the tapping interval is prolonged or the molten iron is not clean, there must be more molten iron accumulated in the furnace, the electrode should rise, and the electrode should be inserted into the charge shallowly.
⒎ slag accumulation in furnace
The slag discharge is not good, there is too much slag in the furnace, the furnace bottom rises, and the insertion depth of the electrode becomes shallow.
8. Diameter of pole center circle between electrodes
For the submerged arc furnace with the same capacity, when the diameter of the polar circle is larger, the distance between the electrodes is longer, the resistance of the charge increases, and the electrode is inserted deeper into the charge. On the contrary, when the diameter of the polar circle is smaller, the electrode insertion depth becomes shallower.
How to judge the depth of electrode entry and exit?
Practical experience can judge the electrode access depth from the following five aspects:
1. Arc sound
In the process of electric furnace smelting, if the arc makes a loud noise, it means that the electrode is inserted into the charge too shallow /. Generally speaking, the electrode insertion depth is more than 800 mm, and the arc sound is small.
2. Material collapse and fire stabbing
Under normal batching conditions, if the phenomena of material collapse and "pricking fire" are frequent, it indicates that the electrode is inserted into the charge too shallow.
3. Crucible area size
Under the condition of normal proportioning ratio, if the charge decreases slowly, it indicates that the electrode is inserted shallowly. Due to the shallowly inserted electrode, the high-temperature area moves upward and the heat loss is large, so the crucible area is small.
4. Furnace mouth temperature
The surface temperature of furnace mouth material is high and the operating conditions are poor, indicating that the electrode insertion is shallow.
5. Iron tapping
Under the condition of normal proportioning ratio, the tap hole is not easy to open, the flow rate of molten iron is slow, the temperature is low, the slag is sticky, the fluidity is poor, and it is difficult to discharge, indicating that the electrode is inserted into the material shallowly.
To sum up, the insufficient depth of the electrode inserted into the charge is often due to excessive coke addition or too short electrode break. At this time, it is necessary to reduce the coke addition or lower the electrode as appropriate.
What should be the normal furnace condition?
One of the basic tasks of smelters should be good at correctly judging the furnace condition, even if the furnace condition is adjusted and handled properly, so that the furnace condition is often in a normal state.
The characteristics of normal furnace conditions are as follows:
1. Insert the electrode into the charge deeply and steadily. At this time, the crucible is large, the material surface has good air permeability, the material layer is soft, the furnace gas is evenly sent out from the furnace mouth, the flame is orange, there is no dark and sintering area on the material surface, and there is no large pricking fire and material collapse. The material level is low and gentle, and the vertebral body is wide. The furnace charge drops rapidly, and the charge surface of the furnace core of the electric furnace with large capacity is slightly sunken.
2. The current is relatively balanced and stable, and can give sufficient load.
3. The iron tapping work is relatively smooth. The tap hole is easy to open, the road hole is unblocked, and the molten iron flow rate is fast. After opening the tap hole, the current drops significantly, the molten iron temperature is high, and the slag fluidity and slag discharge are good. In the later stage of tapping, the pressure of furnace gas ejected from the tap hole is small, and the furnace gas overflows naturally. After tapping, the tap hole is blocked.
The iron tapping is normal and the composition is stable.
Why is the furnace sometimes sticky? How to deal with it?
The situation that the reducing agent in the furnace is insufficient and the air permeability of the charge surface is poor is called sticky in the furnace condition. Some units call sticky in the furnace condition black, that is, the luster of the charge surface is dark.
The characteristics of sticky furnace conditions are as follows:
1. The working of electrode is unstable, the conformity fluctuates greatly, the instrument is difficult to operate, the pointer of ammeter swings frequently, and sometimes insufficient load is given.
2. The air permeability of the charge surface is poor, and the furnace gas is uneven and weak. The material layer is hard. The phenomenon of stabbing fire is serious, and the local stabbing out is a burning white strong flame. There is little flame on the big side.
3. When tamping the furnace, large pieces of bonded materials will be dug out, and even after tamping the furnace, the large surface will not catch fire.
4. It is difficult to remove the root sticking at the working end of the electrode, and even if it is removed, it is easy to stick.
5. The iron tapping work is not smooth. The tap hole is not easy to open, the flow rate of molten iron is slow, the tap hole is not unblocked, the slag is sticky and difficult to discharge, and the pressure of furnace gas ejected from the tap hole is large.
The temperature of molten iron is low, the amount of iron is less, and the silicon content in ferrosilicon is low.
The reasons for sticking in furnace conditions are as follows:
1. Improper dosing ratio, insufficient reducing agent and insufficient chemical reaction in the furnace, resulting in excess silica in the furnace and melting
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