Method for improving pelletizing performance of inferior bentonite

Abstract

The invention discloses a method for improving the pelletizing performance of inferior bentonite. The method for improving the pelletizing performance of the inferior bentonite comprises the following steps: firstly, mixing a proper amount of an additive with the inferior bentonite, then adding a proper amount of water, uniformly mixing again, then drying under the action of a high-pressure external force, and finally grinding the dried inferior bentonite to a certain particle size, thereby obtaining the improved bentonite. According to the method for improving the pelletizing performance of the inferior bentonite, the pelletizing performance of the inferior bentonite can be obviously improved only by adding a small amount of hydroxypropyl distarch phosphate and sodium propionate into the inferior bentonite, and efficient application of the inferior bentonite in iron ore concentrate pellet production is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a method for improving the ball-making performance of inferior bentonite. Background Art

[0002] Bentonite is widely used as a binder in the production of iron ore pellets. Bentonite has good pelletizing performance, high pellet strength, and less powder in production, which can provide high-quality pellets for blast furnace production. Bentonite has poor pelletizing performance, and the quality of the pellets cannot meet the production requirements. The amount of powder in production increases, affecting the production efficiency of the pellets. At the same time, poor-quality pellets will affect the normal production of the blast furnace. Therefore, the selection of high-quality bentonite with good pelletizing performance has become the core of pellet production.

[0003] In recent years, with the development of the steel industry, the demand for high-quality bentonite has become increasingly strong, while the resources of high-quality bentonite have become increasingly scarce, resulting in a shortage of high-quality bentonite, forcing many pellet plants to use inferior bentonite for production. However, the quality of pellets produced using inferior bentonite cannot meet production requirements. The amount of powder in chain grates and rotary kilns is large, which on the one hand causes the ringing of rotary kilns, which is not conducive to smooth production; on the other hand, the generated powder is returned to continue pelletizing, which increases the production load, reduces the output of pellets, and makes production efficiency low. In addition, in order to improve the quality of pellets, increasing the amount of inferior bentonite will not only increase production costs and reduce the iron grade of pellets entering the furnace; but also cause impurity elements such as K to exceed the standard, affecting the normal production of blast furnaces. Therefore, the use of technical means to improve the pelletizing performance of inferior bentonite has become the key to solving the problem of shortage of high-quality bentonite. Summary of the invention

[0004] To achieve the above-mentioned purpose, the present invention provides a method for improving the pelletizing performance of inferior bentonite. The pelletizing performance of the inferior bentonite can be significantly improved by simply adding a small amount of hydroxypropyl distarch phosphate and sodium propionate to the inferior bentonite, thereby realizing the application of the inferior bentonite in the production of iron ore concentrate pellets.

[0005] The invention provides a method for improving the ball-forming performance of inferior bentonite. The method comprises the following steps: firstly mixing an appropriate amount of additive with the inferior bentonite, then adding an appropriate amount of water and mixing them evenly again, drying the mixture after being subjected to high-pressure external force, and finally grinding the dried inferior bentonite to a certain particle size to obtain improved bentonite.

[0006] In a preferred embodiment of the method for improving the ball-forming properties of inferior bentonite provided by the present invention, the additives include hydroxypropyl distarch phosphate and sodium propionate.

[0007] Hydroxypropyl distarch phosphate is an excellent additive that can significantly improve the strength of green balls, while sodium propionate can significantly improve the strength of preheated balls and baked balls while improving the strength of green balls to a certain extent. Using hydroxypropyl distarch phosphate and sodium propionate as additives, on the one hand, has a wide source, low price, and obvious effect, and on the other hand, has little effect on the composition of the balls.

[0008] In a preferred embodiment of the method for improving the ball-forming performance of inferior bentonite provided by the present invention, the addition amount of hydroxypropyl distarch phosphate is 0-20% of the mass of the bentonite; and the addition amount of sodium propionate is 5-8% of the mass of the bentonite.

[0009] In a preferred embodiment of the method for improving the ball-forming performance of inferior bentonite provided by the present invention, the high-pressure external force is a high-pressure roller mill.

[0010] Through high-pressure roller milling, on the one hand, the lattice structure of bentonite is destroyed, so that bentonite is compounded with hydroxypropyl distarch phosphate and sodium propionate, and the hydroxypropyl distarch phosphate and sodium propionate groups enter the lattice structure of bentonite to achieve bentonite modification; on the other hand, the surface properties of bentonite itself, such as specific surface area, are changed.

[0011] In a preferred embodiment of the method for improving the ball-forming properties of inferior bentonite provided by the present invention, the drying is performed at 105° C. for 3 to 4 hours.

[0012] Excessive moisture in the bentonite can be removed by the drying.

[0013] In a preferred embodiment of the method for improving the ball-forming performance of inferior bentonite provided by the present invention, the inferior bentonite after drying is ground to -0.074 mm.

[0014] The lattice structure of bentonite is further destroyed by grinding, and the modification of bentonite by hydroxypropyl distarch phosphate and sodium propionate is strengthened. In addition, the bentonite particle size is less than 0.074 mm so that the finely ground bentonite and iron ore particles can be better bonded into balls.

[0015] Compared with the prior art, the method for improving the ball-forming performance of inferior bentonite provided by the present invention has the following beneficial effects: 1. The present invention can significantly improve the pelletizing performance of inferior bentonite by only adding a small amount of hydroxypropyl distarch phosphate and sodium propionate to inferior bentonite, thereby realizing the application of inferior bentonite in the production of iron ore concentrate pellets.

[0016] 2. The present invention selectively improves the performance of inferior bentonite by adjusting the dosage of hydroxypropyl distarch phosphate and sodium propionate, thereby purposefully improving the strength of the raw balls, preheated balls or calcined balls obtained by the bentonite pelletizing. The method of the present invention is applicable to different types of inferior bentonite and has a wide range of applications. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In each control example and embodiment of the present invention, the same iron concentrate is selected, the pelletizing time is 12 min, and the pelletizing moisture content is 8.5%; the preheating and roasting conditions are: preheating temperature is 950°C, preheating time is 10 min, roasting temperature is 1250°C, and roasting time is 10 min.

[0019] Comparative Example 1 Inferior bentonite was added to iron ore at a ratio of 1 wt%, mixed and pelletized. The resulting green balls had a drop strength of 2.6 times / 0.5 m and a compressive strength of 10.65 N / P; the preheated balls had a compressive strength of 363 N / P; and the calcined balls had a compressive strength of 2024 N / P.

[0020] Comparative Example 2 Inferior bentonite was added to iron ore at a ratio of 1.5 wt%, mixed and pelletized. The resulting green balls had a drop strength of 3.3 times / 0.5 m and a compressive strength of 11.72 N / P; the preheated balls had a compressive strength of 398 N / P; and the calcined balls had a compressive strength of 2373 N / P.

[0021] Comparative Example 3 Inferior bentonite was added to iron ore at a ratio of 1.5 wt% and mixed and pelletized. The resulting green balls had a drop strength of 4.6 times / 0.5 m and a compressive strength of 14.21 N / P; the preheated balls had a compressive strength of 438 N / P; and the calcined balls had a compressive strength of 2669 N / P. Example

[0022] 20 parts of hydroxypropyl distarch phosphate were added to 100 parts of bentonite and mixed, and then an appropriate amount of water was added to mix evenly again, and then the mixture was passed through a high-pressure roller mill and dried at 105°C for 3 hours. Finally, the dried inferior bentonite was ground to -0.074 mm to obtain improved bentonite; the modified bentonite was added to the iron ore at a ratio of 1 wt%, mixed evenly and pelletized, and the resulting green ball had a drop strength of 4.5 times / 0.5 m and a compressive strength of 12.91 N / P; the compressive strength of the preheated ball was 438 N / P; and the compressive strength of the calcined ball was 2445 N / P. Example

[0023] 5 parts of sodium propionate were added to 100 parts of bentonite and mixed, and then an appropriate amount of water was added to mix evenly again, and then the mixture was passed through a high-pressure roller mill and dried at 105°C for 3 hours. Finally, the dried inferior bentonite was ground to -0.074 mm to obtain improved bentonite; the modified bentonite was added to the iron ore at a ratio of 1 wt%, mixed evenly and pelletized, and the resulting green ball had a drop strength of 3.7 times / 0.5 m and a compressive strength of 11.94 N / P; the compressive strength of the preheated ball was 451 N / P; and the compressive strength of the calcined ball was 2825 N / P. Example

[0024] 8 parts of sodium propionate were added to 100 parts of bentonite and mixed, and then an appropriate amount of water was added to mix evenly again, and then the mixture was passed through a high-pressure roller mill and dried at 105°C for 3 hours. Finally, the dried inferior bentonite was ground to -0.074 mm to obtain improved bentonite; the modified bentonite was added to the iron ore at a ratio of 1 wt%, mixed evenly and pelletized, and the resulting green ball had a drop strength of 4.2 times / 0.5 m and a compressive strength of 12.52 N / P; the compressive strength of the preheated ball was 473 N / P; and the compressive strength of the calcined ball was 2973N / P. Example

[0025] 5 parts of hydroxypropyl distarch phosphate and 5 parts of sodium propionate are added to 100 parts of bentonite and mixed, and then an appropriate amount of water is added to mix evenly again, and then the mixture is passed through a high-pressure roller mill and dried at 105°C for 3 hours. Finally, the dried inferior bentonite is ground to -0.074 mm to obtain improved bentonite; the modified bentonite is added to the iron ore concentrate at a ratio of 1 wt%, mixed evenly and balled, and the resulting green ball has a drop strength of 5.1 times / 0.5 m and a compressive strength of 13.11 N / P; the compressive strength of the preheated ball is 487 N / P; and the compressive strength of the calcined ball is 3045 N / P. Example

[0026] 10 parts of hydroxypropyl distarch phosphate and 6 parts of sodium propionate are added to 100 parts of bentonite and mixed, and then an appropriate amount of water is added to mix evenly again, and then the mixture is passed through a high-pressure roller mill and dried at 105°C for 3.5 hours. Finally, the dried inferior bentonite is ground to -0.074 mm to obtain improved bentonite; the modified bentonite is added to the iron ore at a ratio of 1 wt%, mixed evenly and balled, and the resulting green ball has a drop strength of 5.2 times / 0.5 m and a compressive strength of 14.71 N / P; the compressive strength of the preheated ball is 491 N / P; and the compressive strength of the calcined ball is 3051 N / P. Example

[0027] 20 parts of hydroxypropyl distarch phosphate and 8 parts of sodium propionate are added to 100 parts of bentonite and mixed, and then an appropriate amount of water is added to mix evenly again, and then the mixture is passed through a high-pressure roller mill and dried at 105°C for 4 hours. Finally, the dried inferior bentonite is ground to -0.074 mm to obtain improved bentonite; the modified bentonite is added to the iron ore concentrate at a ratio of 1 wt%, mixed evenly and balled, and the resulting green ball has a drop strength of 6.2 times / 0.5 m and a compressive strength of 15.89 N / P; the compressive strength of the preheated ball is 496 N / P; and the compressive strength of the calcined ball is 3080 N / P.

[0028] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for improving the ball-forming properties of inferior bentonite, characterized in that: First, mix an appropriate amount of additives with inferior bentonite, then add an appropriate amount of water and mix evenly again, then dry it after high-pressure external force, and finally grind the dried inferior bentonite to a certain particle size to obtain the improved bentonite.

2. The method for improving the ball-forming properties of inferior bentonite according to claim 1, characterized in that: The additives include hydroxypropyl distarch phosphate and sodium propionate.

3. The method for improving the ball-forming properties of inferior bentonite according to claim 2, characterized in that: The addition amount of the hydroxypropyl distarch phosphate is 0-20% of the mass of the bentonite; the addition amount of the sodium propionate is 5-8% of the mass of the bentonite.

4. The method for improving the ball-forming properties of inferior bentonite according to claim 1, characterized in that: The high-pressure external force is a high-pressure roller mill.

5. The method for improving the ball-forming properties of inferior bentonite according to claim 1, characterized in that: The drying step is to place the mixture at 105° C. for 3 to 4 hours.

6. The method for improving the ball-forming properties of inferior bentonite according to claim 1, characterized in that: The dried inferior bentonite was ground to -0.074 mm.