For half a century, brown fused alumina production still uses traditional techniques and has never changed. With the changes of the times, mineral resources have declined sharply, the quality of mineral products has continued to decline, raw material and energy prices have continued to increase, and energy conservation and emission reduction tasks have become increasingly arduous. Brown aluminum oxide production has been besieged from all sides. If there are no new breakthroughs in technology, it can be predicted Ten years from now, the unit energy consumption and production costs of producing brown fused alumina will rise alarmingly, and some brown fused alumina production companies will be forced to shut down as a result. Calculated based on the current market price as a constant price, the production cost of brown aluminum oxide will be between 4,500-5,000 yuan. Energy conservation and emission reduction will become an insurmountable problem. In view of the above factors, future brown aluminum oxide production and development must under the guidance of the scientific outlook on development, we should transform the mode of production and development as soon as possible and take the road of technological innovation.
The smelting process of brown fused alumina is divided into four stages: arc starting, smelting, control and refining.
01 Arc Starting
Arc starting is the prerequisite for brown fused alumina smelting. In order to make the current between the three-phase electrodes the same, the arc starting focus must be placed. When placing the arc starting coke, first add a small amount of alumina to smooth the bottom of the furnace and keep the electrode slightly away from the bottom of the furnace. Iron filings and carbon particles are mixed and laid in a certain shape in the center of the furnace pool, and arc coke is laid at the bottom of the three electrodes to make the three electrodes pass through each other. There are three ways to place arc starting focus: star-shaped placement, solid triangle placement and hollow triangle placement. After practical comparison, the star-shaped arrangement method was selected. Its advantages are less arc starting coke consumption, less carbon addition in the furnace, fast arc starting, and heat concentration in the center of the furnace pool.
After placing the arc starting focus, power is supplied to start the arc. When the three electrodes are dropped to the arc starting focus, when you see the arc light and hear the arc sound, it means that the arc has started. When the current rises to 20% to 50% of the normal load, add a small amount of charge to the outside of the electrode and the arc area to suppress the arc. When the current rises to 80% of the load, the material is added normally and the melting stage is entered.
02 Smelting
Smelting accounts for more than 80% of the total smelting time. It is very important to effectively grasp the smelting stages of brown fused alumina smelting. In the smelting stage, the charge is melted into a liquid state, the impurities are reduced, the iron alloy is formed and separated from the corundum solution. During the smelting process, it is necessary to constantly use sticky sticks to check the quality of the melt and make necessary adjustments before the furnace, and to prevent various "abnormal phenomena" from occurring. The material layer will slowly fall according to the degree of smelting. To ensure that the melt in the furnace is sufficient, charging is required during the smelting process. The main goal of charging is to fill the electric furnace and end the smelting period. The new process improvement is mainly to further control the important link of the smelting stage. The smelting stage is an important link related to smelting production safety, energy consumption, smelting unit time utilization, smoke and dust emissions and worker labor intensity.
03 Control
The so-called "control" means to stop feeding materials within a certain period of time, so that the materials in the furnace can be melted and reduced as much as possible, and the melting area can be expanded outward. If the furnace conditions are "controlled" well, the solution will rise slowly and the entire material surface will sink evenly. The more material is added, the faster it melts. During the control period, try to use the heat to expand the melting area. After completion, the preheated material is put into the furnace to continue smelting. During the control period, the charge is not completely melted. To avoid lowering the temperature of the solution, the charge will slowly enter the melt. The arc will be exposed, resulting in large heat loss in the furnace and excessive power loss.
04 Refining
The purpose of refining is to fully reduce impurities, better precipitate and gather the ferroalloy, discharge the gas in the furnace smoothly, and at the same time further increase the temperature of the melt and expand the melting area. When the electric furnace is transferred to refining, it is necessary to stop feeding materials and use low voltage to melt the input materials as much as possible. The characteristics of sufficient refining are: the material layer in the furnace is very thin, the material and the melt around the electrode are in close contact, and the liquid level is very stable; the pointer of the three-phase electrode ammeter is stable. There is not much gas escaping from the electrode root, and the arc sound is consistent and uninterrupted. If the refining period is not properly controlled, the power consumption will be excessively increased. The quality of refining directly affects the quality and yield of corundum.
Smelting Process
In the long-term practice process, we have continuously improved the smelting process and explored a new smelting method suitable for the current production situation. The new smelting process of the dumping furnace was adopted based on our own conditions and the carbon ratio was adjusted during the smelting process. , to compensate for the unstable furnace conditions caused by laboratory errors and inaccurate formulas. Increase the number of refills to bury the exposed arc light and improve the utilization of arc heat energy. Reduce the height of the material surface, increase the space from the upper part of the furnace shell to the lower part of the water-cooling cover, increase the space inside the furnace, ensure good collection of smoke and dust, and reduce smoke and dust emissions. The thin material surface operation is used to discharge the gas generated by the reduction reaction evenly, reduce the gas pressure in the furnace, and avoid the occurrence of furnace blasting. By comparing the advantages and disadvantages of the open arc method and the submerged arc method, combined with the actual application in our production, the new brown fused alumina smelting process adopts a half-open and half-buried method. The new process controls the input of raw materials and reduces the height of the material surface. Compared with the traditional Compared with the dumping furnace smelting process, the material surface height is reduced by 40cm, which increases the space in the furnace. It reduces the density of smoke and dust in the furnace and effectively treats the discharged smoke and dust so that the smoke and dust does not escape in the operating area. Compared with the traditional dumping furnace smelting process, the environmental protection effect is more obvious and allows workers to avoid contact with the discharged smoke and dust. Smoke and dust can protect workers' health better than traditional smelting processes.
It can be seen from the actual production data that the dumping furnace smelting process can effectively increase output, reduce power consumption, and ensure steady growth of economic benefits.
