A kind of bonding agent for iron ore pellet and preparation method thereof
Technical field
The invention belongs to field of metallurgy, particularly a kind of bonding agent for iron ore pellet and preparation method thereof.
Background technology
China is Iron and Steel Production big country, and annual pellet demand to ironmaking usefulness is very big.Pellet has metallurgical performances such as ferrous grade height, Well-recovered, cold strength height, and improving the pellet usage ratio is to optimize the blast furnace burden structure, promotes the ironmaking operation to save energy and reduce the cost, improve output, realize eco-friendly important means.For this reason, Iron and Steel Enterprises in China is all being made great efforts the development pellet.
But be subjected to the restriction of iron ore resource and apparatus processing condition, problem such as China's pellet formation raw material fine iron breeze exists that grade is low, gangue content is high, coarse size, size composition are unreasonable, cause pellet quality and compare abroad that there is a big difference, it is lower to make blast furnace use the ratio of pellet.Wilkinite is with addition of the ratio height in addition, and abroad all in 1%, China is on average up to 3%, and along with day being becoming tight of ore resource, causes the smart opaque amount of pelletizing iron further to worsen, and bentonite consumption also has the trend that increases.
Wilkinite is as binding agent the most frequently used in the acid pellet, be divided into sodium bentonite and calcium-base bentonite, general addition is 1~3%, the performance of general sodium bentonite is better than calcium-base bentonite, adds wilkinite in the pelletizing and can play the adjusting raw material moisture, stablize effects such as pelletizing is operated, raising intensity.But bentonitic main component is SiO
2And Al
2O
3, content is up to about 70%, K
2O, Na
2Detrimental impurity content such as O are up to about 2.0%, when this characteristic has determined that wilkinite is used to make ball, can reduce the grade of finished product pellet, the most of wilkinites of China are second-rate in addition, the powdered iron ore granularity is thicker, often take to strengthen bentonite consumption for improving green ball strength, thereby make above-mentioned shortcoming seem particularly evident.Data rule of thumb, wilkinite is with addition of the every raising 1% of amount, and pellet grade reduces by 0.6%, and the grade of the every reduction by 1% of pellet is made a price reduction 10~20 yuan/ton, and this is to producing millions of tons pelletizing plant per year, and it is huge causing financial loss every year.
Current production is used for the binding agent of powdered iron ore moulding except wilkinite, also useful abroad Peridur organic binder bonds such as (pendant benefits).These organic binder bonds all do not contain detrimental impurity such as Si, Al, K, Na, have improved breeze balling ratio and dropping strength, and consumption is also than wilkinite much less.But this class additive costs an arm and a leg, and in the green-ball drying process, the defective of degradation aspect under the burst temperature occurs in addition, so domestic still do not have enterprise to use organic binder bond in the pellet production process of reality.
Summary of the invention
The purpose of this invention is to provide a kind of bonding agent for iron ore pellet and preparation method thereof, mainly be that the milltailings that utilizes some to have cohesiveness, contains useful element B, Mg make to replace bentonitic binding agent, can satisfy enterprise uses organic binder bond in the pellet production process of reality requirement.
In order to achieve the above object, the present invention is achieved in that
A kind of bonding agent for iron ore pellet, its composition is by weight percentage: sodium bentonite 20~70%, the milltailings 30~79% of boracic magnesium, additive 1~10%.
The granularity of this binding agent user mode is less than 200 orders.
Described milltailings is the mine tailing that contain B, Mg of paigeite behind magnetic separation iron, wherein B
2O
3〉=0.2wt%, MgO 〉=20wt%.
Described additive is at least a in yellow soda ash, limestone tailing or the magnesite mine tailing.
The milltailings of described boracic magnesium can be by the concentrate of boron magnesium ore deposit, ludwigite and ore dressing thereof, at least a the substituting in the mine tailing.
A kind of preparation method of bonding agent for iron ore pellet, its component concentration according to weight percent is: sodium bentonite 20~70%, the milltailings 30~79% of boracic magnesium, additive 1~10%; Said components is mixed and be ground to granularity less than 200 orders, obtain this binding agent.
Described milltailings is the mine tailing that contain B, Mg of paigeite behind magnetic separation iron, wherein B
2O
3〉=0.2wt%, MgO 〉=20wt%.
Described additive is at least a in yellow soda ash, limestone tailing or the magnesite mine tailing.
Described milltailings can be by the concentrate of boron magnesium ore deposit, ludwigite and ore dressing thereof, at least a the substituting in the mine tailing.
Introduce the effect of each component of binding agent of the present invention below.
Sodium bentonite 20~70wt%: with the base-material of sodium bentonite as binding agent of the present invention, its performance is better than calcium-base bentonite, the pellet performance index of being done the binding agent making by wilkinite are better usually, but softening temperature is low, high temperature soft heat poor-performing, research and practice show, can significantly improve its high temperature soft heat performance when containing element B and Mg in the pellet.
Milltailings 30~the 79wt% of boracic magnesium: contain the beneficial element B and the Mg of pellet needs in this paigeite mine tailing, wherein B
2O
3〉=0.2wt%, MgO 〉=20wt%, form the magnesium Solid solution because increase MgO content in the pellet, improved the melt temperature of slag phase in the pelletizing, the MgO solid solution is in the Fu Shi body simultaneously, suppress the infiltration of FeO in slag, thereby reduced low melting point liquid phase growing amount, significantly improved the high temperature metallurgical properties of acidic pellet ore.MgO can also reduce the expansion of pellet simultaneously.B and Fe at high temperature produce the firm body of netted ternary boride eutectic by mutual scattering and permeating, improved the antiknock of pellet when dry and split temperature, simultaneously the ultimate compression strength of pellet and wear-resistant index also be improved significantly.
The milltailings of boron magnesium can be by the concentrate of boron magnesium ore deposit, ludwigite and ore dressing thereof, at least a the substituting in the mine tailing.
Additive 1~10wt%: the additive in the binder formula of the present invention is yellow soda ash, Wingdale or magnesite, be used for improving bentonitic adhesive property, adjust Ca, Mg content in the pellet, change the acidic character of pellet, the balling-up that this kind pellet additive is had improve breeze, boost productivity, reduce the rate of return mine, improve the ultimate compression strength and the wear-resistant index of green ball strength and pellet.Can also improve simultaneously the high temperature metallurgical properties of pellet.
Compared with prior art, beneficial effect of the present invention is to provide a kind of low Si content, contains useful element B and Mg, can replaces the bentonitic binding agent that is used for iron ore pellets fully, the iron ore pellets of preparation can obviously improve green ball strength and burst temperature, can improve pellet iron grade, can improve pellet quality, the raw material of this additive is taken from the milltailings that heap is abandoned simultaneously, and cost is low, has solved the environmental protection difficult problem of mine tailing.
Embodiment
Choose a kind of prescription and test compression strength of green pellet, dropping strength, antiknock respectively and split temperature, do to throw the cage experiment in the shaft furnace of the actual production of then green-ball being packed into, carry out ultimate compression strength and wear-resistant index and high temperature soft heat performance measurement after taking out finished pellet.
Embodiment:
With the sodium bentonite is base-material, allocates quantitative paigeite mine tailing into as additive.Its composition proportion is: sodium bentonite 30~40%, and mine tailing 40~60%, yellow soda ash 5% (content 99%), magnesite 5% (content 99%), granularity is 100% less than 200 purpose ratios after mixing grinds.
Raw material and additive character are selected in table 1 test for use
Powdered iron ore, % |
Wilkinite, % |
Mine tailing, % |
TFe |
SiO
2 |
Al
2O
3 |
-20 orders |
Smectite content |
Water-intake rate |
Expansion capacity |
B
2O
3 |
MgO |
65.35 |
5.75 |
0.49 |
70 |
67.87 |
230 |
13 |
4.5 |
32.8 |
The present invention is tested test compression strength of green pellet, dropping strength, burst temperature, the ultimate compression strength of finished pellet, wear-resistant index, reflowing temperature, indexs such as the cubical expansivity during reduction according to the pellet quality requirement and the method for inspection.
Table 2 shaft furnace is thrown the production thermal technology condition of cage test
Hot gas flow m
3/h
|
Gas pressure KPa |
Combustion-supporting pressure KPa |
Cold flow m
3/h
|
Cold wind pressure KPa |
Chamber temperature ℃ |
Combustion chamber pressure KPa |
12116 |
24.33 |
23.0 |
32765 |
30.0 |
985 |
16.0 |
The chemical ingredients of table 3 test finished product compares %
Title |
TFe |
SiO
2 |
FeO |
MgO |
S |
B
2O
3 |
Wilkinite |
65.02 |
7.79 |
0.91 |
0.36 |
0.08 |
0 |
This binding agent |
65.35 |
6.75 |
0.7 |
1.09 |
0.08 |
0.17 |
Difference |
+0.33 |
-1.04 |
-0.21 |
+0.73 |
|
+0.17 |
Table 4 green-ball and finished ball quality
Quality of green pellets |
The finished ball quality |
Additive |
Proportioning, 1.4% |
Fall, inferior/ |
Resistance to compression, N/ |
Burst temperature, ℃ |
Resistance to compression, N/ |
The reduction swellability rate, % |
Tumbler index, % |
Loading softening performance |
Reduction ratio, % |
T10 |
T40 |
ΔT |
900℃ |
Wilkinite |
5 |
11 |
450 |
2340 |
13.2 |
94 |
915 |
1165 |
250 |
72.6 |
Binding agent |
7 |
14 |
750 |
3250 |
12.0 |
96 |
992 |
1233 |
241 |
74.1 |
From the measurement result of table 3 as can be known, under equal additive amount condition, with the pelletizing grade increase by 0.33% of additive preparation of the present invention, SiO
2Content reduces by 1.04%, and MgO content increases by 0.73%, B
2O
3Content increases by 0.17%.
From the measurement result of table 4 as can be known, under equal additive amount condition, improve 2 times with the pelletizing shatter strength of green pellet of additive preparation of the present invention, ultimate compression strength improves 3N/, 300 ℃ of burst temperature risings; Product pellet ultimate compression strength improves near 1000N/, and the reduction swellability rate reduces by 1.2%, and softening beginning temperature raises 77 ℃, and the reflowing temperature interval dwindles 9 ℃, and reduction ratio improves 1.5% in the time of 900 ℃.