Factors that affect the recovery rate of ferrotita

Factors affecting the recovery rate of ferrotitanium

ferrotitanium is widely used in iron and steel production, and can be used as deoxidizer, denitrogenation agent and alloy additive. The main factors affecting the recovery rate are as follows:

first, raw material factor

the higher the grade of titanium concentrate and rutile, the better the smelting effect, the more iron is produced, and the Ti content in the alloy is high; When the grade of rutile is more than 90% and the grade of titanium concentrate is more than 50%, the recovery rate is higher; The smelting effect of placer ore is better than that of primary ore. The higher the FeO/Fe2O3 ratio in titanium concentrate, the better the roasting effect and the better the economic and technical indicators before smelting. The particle size of titanium concentrate and rutile should be appropriate, and the flying loss of fine particles should be increased; Too coarse, insufficient thermite reaction, and the recovery rate decreases; Therefore, the particle size of rutile is generally controlled at 100-160 mesh, and that of titanium concentrate is controlled at 40-100 mesh. The ratio of titanium concentrate to rutile should be kept at about 3.5:1. The roasting temperature is generally controlled at 750 ℃ - 850 ℃, and the roasting time is 3-5h, which breaks the old theoretical dilemma. Insufficient roasting temperature and too short roasting time will affect the full progress of unit heat effect and reduction reaction, and adversely affect the recovery rate

a small number of aluminum particles used in the production of ferrotitanium are for private interests. The higher their grade is, the more beneficial it is to the reduction reaction. Generally, aluminum particles with an aluminum content of more than 98% are used. The particle size of aluminum particles will affect the speed of chemical reaction and the utilization rate of aluminum. The aluminum particles are too coarse, the specific surface area is small, and the duration of interface chemical reaction is long, which is not conducive to the concentration of heat, and the slag iron is not easy to separate, the iron is less, the aluminum particles are too fine, and the flying and combustion losses increase. At the same time, the amount of aluminum oxide in the too fine aluminum particles increases, resulting in insufficient aluminum distribution and affecting the reduction of titanium; The appropriate aluminum particle size is generally 60 mesh-1.5mm, accounting for 90%. We are constantly developing new solutions

when lime is added into the charge as a flux, it can reduce the melting point of slag, improve the fluidity of slag, promote the sinking of metal suspended solids, and prevent the combination of TiO and Al2O3, which is conducive to improving the recovery rate of titanium. The CaO content of lime should be high, with a particle size of 1-2mm. There is no need for unburned and powdered lime that absorbs water. The dosage of lime should be appropriate, and the dosage should not be too large. Too much heat is consumed in the reduction process, which reduces the maximum temperature of the system and makes the reaction difficult

silicon in ferrosilicon can combine with titanium in the alloy to synthesize Ti5Si3 and other compounds, prevent the formation of aluminum compounds, reduce the amount of aluminum entering the alloy, and improve the utilization rate of aluminum, which is conducive to the improvement of Ti recovery rate. Ferrosilicon powder with silicon content of about 75% and particle size of 0-1mm is more favorable for smelting ferrotitanium

second, unit heat effect

the factors affecting unit heat effect are: 1) chemical reaction heat of furnace charge; 2) Physical heat brought in by furnace charge. The chemical reaction heat is mainly determined by the grade and batching amount of titanium concentrate, rutile, potassium chlorate and aluminum particles, while the physical heat is mainly determined by the roasting temperature of titanium concentrate and rutile. The production practice shows that the unit calorific value is low, the reduction reaction is difficult to carry out, the slag fluidity is poor, there are more ti containing metal balls in the slag, the slag iron is not easy to separate, and the amount of iron is small; High unit calorific value, intense reaction, splashing caused by slag agitation, large process loss and low output

III. aluminum blending coefficient

it is known from the test that the recovery rate of titanium increases with the increase of aluminum consumption, but excessive aluminum blending will reduce the unit thermal effect of the reaction, thicken the slag, and easily cause the aluminum content of the alloy to exceed the standard, affecting the product quality. Therefore, in order to obtain a high titanium recovery rate, the amount of aluminum must be controlled within an optimal range. The test shows that when the aluminum blending coefficient is 1.03-1.06, the TTI% in the slag is low, the aluminum content in the finished product meets the requirements of gb3282-87, and the smelting effect is the best

IV. feeding speed

the feeding process should follow the principle of "slow first, fast in the middle, and slow last"; When the main material is added after the bottom material reaction, the feeding shall be slow, and the feeding speed shall be increased after the expansion of the molten pool. The appropriate speed shall make the reaction rapid and uniform, and the speed shall be slowed down in the later stage of the reaction to prevent excessive reaction from causing splashing. Proper feeding speed will help to concentrate heat, settle iron particles well and increase iron tapping. It is easy to spray slag if feeding is too fast, the titanium content of the alloy is low, the aluminum content is high, the feeding is too slow, the heat is not concentrated, the heat loss is large, and the iron tapping is low. Finally, pay attention to uniform feeding to prevent the feeding range from changing too much or stopping feeding to cause slag inclusion in the alloy. The production practice shows that it is appropriate to control the feeding time within 9-12min with the total feeding amount of 8t

v. refined material

refined material is also called precipitant. The purpose of adding refined material is to improve the temperature of slag, enhance the fluidity of slag, and make ferrotitanium particles easy to settle from slag; At the same time, when the iron droplets generated by the refining reaction pass through the slag layer from top to bottom, the metal beads suspended in the slag layer with high Ti and small specific gravity can be brought into the molten pool, so as to improve the recovery rate of titanium. At the end of the smelting reaction, with the thickening of the slag layer, the crusting speed of the upper layer of the liquid surface will also accelerate. Therefore, the refined material should have enough reaction heat, and should be preheated as much as possible (temperature 150-200 ℃), and the added material should be timely, uniform and concentrated. After the reaction of refined materials, add 20-30kg lime to protect the slag surface and make it slow down, which is conducive to the settlement of iron particles. Practice shows that in addition to iron scale, aluminum particles and lime, the refined material should also be mixed with the amount of ferrosilicon equivalent to that in the main material, which is conducive to better control the amount of aluminum in the finished product and save aluminum particles

VI. slag discharging and deslagging time

after smelting, pay attention to control the slag discharging and deslagging time, discharge the slag after 5-8min of sedation, and remove the furnace shell after cooling for 12h. If the sedation time is too short, the iron has not completely settled, and the TTI% in the slag is high; If the cooling time is too short, on the one hand, the iron is not fully solidified and easy to leak out when taking off the furnace, on the other hand, titanium is easy to be oxidized at high temperature, increasing losses

VII. Quality of smelting furnace barrel

for the sand pit formed by magnesia or other refractory materials, pay attention to the close vibration, flatten and compact its surface, prevent the alloy from leaking out and increase the bonding amount of the alloy on the surface of the knotting layer, so as not to affect the alloy yield. Practice shows that the particle size of the knotting material at the bottom of the sand pit is 0-3mm, and the particle size of the knotting material on the surface is controlled at 0-1mm, which can reduce the amount of slag iron bonding

VIII. Recovery of fine powder

the 0-10mm fine powder produced in the process of crushing the finished product can only be sold at a lower price, which is 4000-6000 yuan/t lower than the price of the finished product, due to its narrow scope of use. Production practice shows that fine powder is added to the reaction starting material. After the reaction starting material is added, the starting material is made into an annular platform near the edge of the furnace bottom, and the fine powder (50-100kg) is evenly spread on the platform, but the fine powder cannot contact the smelting furnace bottom, which is conducive to the heat absorption of the fine powder. Because the fine powder is on the starting material surface, it does not fully contact the furnace charge, avoiding the titanium in the fine powder from participating in the reduction. In this way, part of the fine powder can be recovered, which indirectly improves the yield of ferrotitanium

IX. other factors

to obtain a good recovery rate, it is also necessary to ensure accurate sampling, uniform mixing, and timely recycling of dust and raw materials scattered on the production site into the furnace for smelting