Semi-crunchy corundum smelting method
Semi-crunchy corundum is a widely used abrasive. Because its brittleness is between white corundum and brown corundum, it is called semi-brittle corundum. Its TiO2 content is lower than that of brown corundum, so it is also called low-titanium corundum. According to the different cooling rates of corundum melt, semi-crunchy corundum is divided into slow-cooled semi-crunchy corundum and quenched semi-brittle corundum.
Semi-crunchy corundum is produced in a dumping electric furnace for smelting brown fused alumina. The average input power of the electric furnace is 500-1500 KW. The equipment for smelting this corundum is a dumping furnace. The typical process of smelting semi-brittle corundum with a dumping furnace is as follows:
Transport the cooked soil to the covered hopper. The bauxite is transported by the belt conveyor and the bucket elevator to the top of the concrete storage bin, and the cooked bauxite is transported from the storage bin to the mixing bin. In the mixing room, there are also iron filing bins, coke silos, refueling silos and other silos.
After weighing all of the raw materials, they are transported by a collecting belt conveyor to a rotary mixer, and the mixed charge is sent to the electric furnace charging box by a belt conveyor. The input power of the electric furnace is 3500 K W , and the typical charge ratio is:
Bauxite 1000 kg
Iron filings 146 kg
Coke 40 kg
re-furnace material 100-600 kg
The amount of reheating material can be determined as appropriate.
The charge is sent to the funnel-shaped storage hopper through a short belt conveyor from two containers on both sides of the furnace.
Then flow from the storage hopper to the swing feed tube. The furnace worker can rotate the swinging feed tube around the electrode by 1 to 50 degrees, so that the charge can be added to the desired location.
Start a new electric furnace as described below. A layer of 305 mm thick semi-brittle corundum is placed on the bottom of the furnace, and the carbon block or graphite block is placed between the electrodes and then arc-smelted. When refining the corundum melt to a depth of 6 10 m, the electricity supply is stopped and allowed to cool naturally for 24 hours. This is called bottom smelting or " smelted bottom" (that is, refining a corundum furnace bottom).
Then, normal smelting can be carried out. After each four packs of corundum, the ferrosilicon is poured. The package can accommodate 4 53 6 - 5 4 60 kg of corundum melt. The bag is made of steel plate and has a lining of about 150 mm thick. The lining material can be made of bauxite, clay and anthracite, or dried by carbon paste. You can also pour more than four packs of corundum and pour a ferrosilicon. From a practical point of view, it is necessary to prevent the corundum melt poured into the package from containing ferrosilicon, because in the package, the ferrosilicon melt and the corundum melt are in contact, and a sponge-like corundum, a sponge-like corundum is formed. Not suitable for abrasives, so it must be re-refined. Corundum containing ferrosilicon particles has to be re-refined.
The material that is poured out of the furnace is:
First-class semi-crunchy jade 65%-75%
Second-class semi-brittle corundum 10%-20%
The electricity consumption per ton of semi-brittle corundum is 1,700-1,900 kW. This refers to the electricity consumption of the corundum produced, and the bauxite used is high-grade bauxite with an A l203 content of more than 85 %. Because ferrosilicon is a by-product, its energy consumption is not counted in the energy consumption of corundum. If the energy consumption of ferrosilicon is also counted in the first-class semi-crunchy corundum, the electricity consumption per ton of corundum is 2260- 2920 kW·hour .
The electrode used was a carbon electrode with a diameter of 365 mm. , length 1828mm. The electrodes are housed in a sleeve made of 24 gauge iron. The iron sleeve prevents oxidation of the electrode, which has been confirmed in the electric furnace test of single-phase and two-electrode.
Under the same operating conditions, the burning rate of the experimental 30 mm (carbon) electrode is as follows:
Not covered with iron electrode 13.8 kg / hour
Wrapped iron electrode 6.35 kg / hour
Self-baking electrodes are also used for the smelting of semi-brittle corundum and brown corundum. Smelting a ton of corundum requires a consumption of 11.51 kg of pre-sintered carbon electrode. If a Soderberg electrode is used, its consumption will increase by 20%.
The corundum electric furnace has a thinner layer (100-305mm) and produces only a small amount of CO.
After the immersion of the corundum melt is cooled for 2-3 days, the frit is ejected from the bottom of the package with a hydraulic head. The hydraulic head is inserted through a hole from the bottom of the package to slowly push the frit out of the package. When the frit exposes half of the package, the clamp is gripped by the crane to clamp the frit to the crushing site.
After lifting the frit, the bottom of the package must be repaired. Place a metal mesh in the perforated area and fill the hole with a lining. Before the lining is sintered, the gold butcher net serves as a supporting lining.
The quality of corundum must be strictly controlled. To do this, it is necessary to continuously sample and test after the furnace is opened and the furnace condition is normal before pouring. A 1 kg sample was taken from the melt using a thick cast steel spoon. The sample is rapidly cooled, and the small sample is loaded into a small box and sent to the central laboratory by a pneumatic tube. The sample was ground in a central laboratory and the content of TiO2 and SiO2 was measured by a vacuum X-ray photometer. The test results will be communicated to the furnace worker within 15 to 30 minutes. If the quality requirements are met, start pouring; otherwise, the quality needs to be adjusted. After adjusting the quality, the sample should be sampled more frequently so that the melt composition meets the requirements.
This method is also used to control product quality when using a frit method to smelt brown fused alumina.