Cold Briquetting From Fine Ore(2)
Source: internal company
Cold Briquetting From Fine Ore
Drying and Consolidation of Cold-pressed Pellets
Two factors determine the strength of cold briquettes. One is the molding pressure, the material mixed with binder forms briquettes under the action of appropriate pressing force. The second is to let the green ball remove water and carry out carbonation reaction through certain drying and consolidation methods to improve its strength. There are many equipment used for drying, such as drum dryer, shaft furnace, consolidation tank, etc. According to the principles of high efficiency, convenience and economy, the advantages and disadvantages of various drying equipment are compared. We find that it is better to adopt the two-time curing method of grate reinforcement and tank formation.
(1) The advantages of rotary drum dryer are wide application range, good drying effect, simple control and reliable operation. Its disadvantages are large floor area and long drying time. As the newly pressed briquette is still very fragile and its strength is very unstable, when it enters the rotating cylinder, it is lifted high and falls heavily, which will break the pellet and affect the briquette forming rate.
(2) Tunnel kiln can effectively avoid the above-mentioned disadvantages of dynamic operation, and the whole drying process is not damaged by external forces. However, its disadvantage is mainly intermittent operation. The track car waited at the lower entrance of the briquetting, filled up with one car and drove away before loading the next car. This intermittent operation is suitable for briquetting and other production.
(3) Shaft furnace is the best drying method for both briquetting and pelletizing. It is not damaged by external force impact, but also can operate continuously. The green balls are continuously transported to the top of the shaft furnace through a belt conveyor and then slowly moved down. The gas is input into the shaft furnace, reacted and burned together with some coke powder in the pellets, and dried for 8-10 hours before being discharged from the furnace.
(4) The drying method of grate reinforcement tank is based on the consideration of low temperature requirement and low investment for cold-pressed briquette drying. The pressed briquettes are sent to the grate (rated load is 19t/h) by the cloth belt conveyor, delivered to the outlet for 1 hour, and then sent to the consolidation tank for drying for more than 8 hours, thus completing the whole consolidation process.
Considering the equipment configuration, there are also factors that affect the strength of pellets, such as mixed grinding, under-screen recycling and metering. As for the process particle size, ratio, binder, moisture, drying temperature and time and many other influencing factors.
(1) Forming pressure: Manganese ore powder pellet is 500kg/cm2, chromium ore powder pellet is 1000kg/cm2.
(2) The process of forming cold-pressed pellets is an alternating cycle process in which the ball press continuously pressurizes the roller material. When the pressing force of the counter roller on the material dominates and reaches the maximum value, the pellet completes the pressing process through this instantaneous contact pressing force.
(3) For the roller ball pressing machine, the machine with high pressing force, good wear resistance of roller skin and easy demoulding should be selected.
(4) The strength of green balls must be improved by certain drying and consolidation methods. There are many drying equipment. According to the principles of high efficiency, convenience and economy, the advantages and disadvantages of various drying equipment are compared and selected.
(5) In terms of process, pellets that meet or exceed the strength index required by the process can be produced by giving the best parameters such as particle size, ratio, binder, moisture, drying temperature and time, and combining with the reasonable configuration of equipment such as pressing force, drying and mixing grinding, under-sieve recycling and metering and testing.