Binder for Coke Powder Cold Briquetting-Sodium Silicate
Source: internal company
Coke is the main fuel in iron-making industry, but coke is fragile and there are a lot of cheap coke powder. However, the high content of coke powder in iron-making fuel will inevitably affect the air permeability in the furnace during iron making, so it is necessary to block coke powder. At present, coke powder can only be made into blocks by agglomeration method, and the key technology is the development of molding binder. Common binders include inorganic binders, such as hydrated lime, Portland cement and bentonite, which only make the green ball strength of coke powder pellets meet the use requirements, but the dry ball strength cannot meet the use requirements. In addition, there are industrial wastes, such as sulfurous acid pulp waste liquid, which contains sulfur, which will cause harm to iron-making and will not be used in general. Pure organic binder, expensive. Sodium silicate is rich in resources and low in price. When we apply it to the cold setting molding of coke powder, we find that the strength of green balls and dry balls can meet the use requirements at low dosage. However, if the content of sodium silicate in the coke powder pellet is too high, the cost of the pellet will increase and the ash content of the coke powder pellet will be too high. Therefore, it is necessary to improve sodium silicate.
1. Experimental section
1.1 Raw materials and instruments
The coke powder is sieved by 5mm to obtain-5mm coke powder, and dried to constant weight for later use. The modulus of sodium silicate is 3.3, Baume degree is 40Bee, and the average relative molecular mass of polyacrylamide is 3 million. Water soluble phenol, formaldehyde resin. Sodium humate and kaolin, industrial products, glucose, chemically pure, NaHCO3, AlCl3 analytically pure.
FN202-2 electric heating drying oven is used to dry green balls. DLY-10A universal material testing machine for pellet pressing. LJ-1000 tensile testing machine is used to measure compressive strength. Muffle furnace is used to measure thermal performance.
1.2 Selection of Coke Powder Cold Solidification Forming Process Parameters
Retting time: 0.5-1h. Pressing time: 20min. Forming pressure: 35.7 MPa. Drying temperature of green balls: 100 ℃. Drying time of green balls: 2h. The total dosage of water and sodium silicate accounts for 16% of the mass fraction of dry coke powder.
2. Pellet performance test
2.1 Determination of Dropping Strength of Green Ball and Dry Ball
The green ball and the dry ball fell at a height of 0.5 m and 1m respectively until the tested ball was broken. The number of falls was recorded respectively. The average value of the number of falls was obtained through 5 parallel experiments, which was the intensity of falls.
2.2 Heat resistance test
The dry balls were kept at 850-900 ℃ for 10min in a muffle furnace, cooled, and their falling strength and compressive strength were measured according to the dry balls.
2.3 Water resistance test
Soak the dry balls in normal temperature water for 72h, take them out, and measure their falling strength and compressive strength according to the dry balls.
3. Results and conclusions
Under the condition that the total amount of water and sodium silicate remains unchanged, the strength of the pellets increases in turn with the increase of the relative amount of sodium silicate. However, the relative amount of sodium silicate is too large, which seriously affects the quality of coke powder pellets, mainly because the ash content is too high. Therefore, we temporarily chose the ratio of water to sodium silicate to be 3: 7 (mass ratio) to modify sodium silicate. Because the ratio of water to sodium silicate is 3: 7 (mass ratio), the dry ball strength of the pellets basically meets the requirements (in production, the drop strength of green balls and dry balls is generally required to be ≥ 3 times and ≥ 50 times respectively, and the compressive strength is ≥ 0. 8MPa and ≥ 6. 0MPa respectively)