Nibrasco Briquetting Plant
Source: internal company
Nibrasco briquetting plant was completed and put into production in August 1978. This article will describe the process flow of each section of the factory.
1. Raw materials are stored and mixed evenly
Because the change of raw material properties has a great influence on the quality of finished products, the stacker and reclaimer should be used to mix the ore evenly during the storage of raw materials in the stock yard. The storage capacity of the raw material storage yard is 300,000 tons.
2. Grin and concentrating
The raw ore is automatically unloaded into the four ore troughs in front of the ball mill by the shuttle belt conveyor, then quantitatively given by the disc feeder, and a certain proportion of water is added to enter the ball mill together for closed-circuit wet grinding. Each ball mill is equipped with a hydrocyclone. The ore powder with a Brain index of about 1500cm2/g is fed to the thickener with an overflow with a concentration of 20%. The concentrated ore pulp is fed to the ore pulp tank equipped with a mixer by adjusting its concentration to about 70% through a pump with adjustable rotation speed. At the outlet of the ore pulp tank, water is automatically added to dilute to about 65% and sent to dehydration.
3. Dehydration and mixing
The ore pulp is vacuum dehydrated by 8 disc filters in various series, and becomes a filter cake with a water content of about 8%, which is sent to a storage tank for storage. It is quantitatively given by a disc feeder and then fully mixed with hydrated lime added according to a certain proportion in a powerful mixer and a wheel mixer.
In order to improve the quality of briquetts, a double closed-circuit process is adopted for briquetting. Five disc pelletizers of each series are used for pelletizing. Then, before being fed into the roaster, the pellets are whole by the set roller screen. The unqualified pellets will be returned and mixed with the raw materials for pelletizing after being crushed.
1. Drying belt 2. Preheating, roasting and homogenizing belt 3. Cooling belt 4. Roller distribution screening machine 5. Trolley
6. Drying exhaust fan 7. Drying blower 8. Preheating exhaust fan 9. Roasting exhaust fan 10. Cooling blower
The briquetts are transported to the trolley with the base material and the edge material laid, and are in a relatively static state. After blast drying, ventilation drying and preheating, the pellets are roasted and soaked at about 1350 ℃. Then it is cooled to about 150 ℃ by blast on the trolley and then discharged from the tail of the machine, as shown in the figure.
This process takes about 40 minutes, and the high-temperature waste gas passing through the cooling section is used for blast drying, preheating and roasting. In addition, the high-temperature waste gas from the roasting section is circulated and supplied to exhaust for drying. The recycling of this waste gas improves the heat recovery rate and saves fuel consumption. The running speed of the trolley can be automatically controlled according to the feeding amount of pellets, and the temperature and pressure in the furnace can also be automatically controlled, so the finished briquettes have good quality. Even if the properties of the raw materials change, suitable operations can be carried out by adjusting the temperature and air volume. In addition, the base material and the edge material laid on the trolley are used as heat storage layers, which are beneficial to heat recovery, improve the uniform distribution of heat load in the pellets, and strengthen the heat insulation protection of the trolley itself. Even if the supply of green balls is interrupted due to accidents, the bedding material can be used instead of pellets to continuously fill the whole trolley to ensure the continuous operation of the equipment. In this way, the refractory material can be prevented from being damaged due to overheating of the trolley and quenching of the furnace, and the pellets can be reloaded to smoothly operate.