Preparation and processing of sintering raw materials (1)

The amount of sintering raw materials is large, the variety is varied, and the particle size and chemical properties are extremely uneven. In order to obtain high-quality sinter, and to ensure the continuous production process, the storage, neutralization, mixing, crushing and sieving of raw materials is a very important task.
First, the storage of raw materials and neutralization and mixing
In order to ensure continuous production of sintering and neutralization and mixing, a raw material field should be established in or near the sintering plant. The size of the raw material field should be determined according to factors such as the scale of production and the proximity of the raw material base, transportation conditions, and types of raw materials. Raw materials should be kept for 1-3 months. China's major iron and steel enterprises in the company has a large field of raw materials, raw material storage warehouse with a sintering plant, but the lack of equipment and mix.
There are many methods for neutralizing raw materials, but they are generally stored in separate piles and tiled. The ore is laid down layer by layer by the stacker and the moving belt, and then cut along the vertical plane of the pile by the reclaimer. The larger the pile, the longer the material can be used for a longer period of time. Two stockpiles must be set up, one for mining and one for use. Figure 1 is a schematic diagram of the neutralization and mixing operation of the Shougang raw material field iron concentrate.

Shougang Baimiao stockyard covers an area of ​​200,000 ^m3 , using wing-type multi-dumping machine to unload material, electric shovel to build piles, and electric shovel to take materials. Each pile is tiling 8 layers, height #3.5～4.0 meters, each pile can store 1.5~200 tons of concentrate, 23,000 tons of natural ore, after neutralization and mixing, the concentrate contains iron fluctuations of ±1.0% up to 80~ About 95%. Later, the operation management was strengthened, and the mixing method of “three dumping into the pile” was adopted to strengthen the mixing before the pile was piled up, so that the fluctuation of the iron content of the concentrate was reduced from ±2.15% to <±1.0%, and the iron-containing fluctuation was ≤±0.5. The % reached 88.31～92.77%. As a result, the qualified rate of sinter increased from 76.61% to 99.92%, and the first grade rate increased from 32.9% to 86.22%. Since the sinter mineral is the most improved, the blast furnace utilization coefficient is 1.876 tons. / m ³ • day, increased to 2.0867 tons / m ³ • day, increased production by 10%, coke ratio reduced by 10%.
Baoshan Iron and Steel Plant has a modern raw material storage and neutralization and mixing raw material field. The feedstock field covers 820,000 m ^2, about 8% of the total area of the whole plant. The method of using a large centralized arrangement, the ore yard primary, secondary yard, field auxiliary material, mix yard, sinter pellets yard, power coal and coking coal stockyard and ore crushing and screening facilities are arranged together. The total storage capacity is 2.57 million tons. The characteristics and operation process of the mixing and mixing system are as follows.
1) There is a stockyard. After the raw materials are discharged from the raw material terminal, they are stacked and mixed initially in the same material yard according to the variety and composition. In order to prevent particle size segregation of the raw materials, the fabric of the primary stockyard is carried out in a scaly stocking manner, and other plants also have a diamond-shaped or strip-shaped fabric (Fig. 2). The quality of the work of the primary stockyard will affect the next process and mix. Effect.

2) The various mixed raw materials stored in the primary stockyard are sent to the uniforming relay tank by the sampling machine and the belt conveyor (Fig. 3). The relay tank can be used to store, batch and control the feeding amount to improve the mixing operation. Effect. This batching device is identical to the sintering process ingredients, and is automatically weighed. The calculation and adjustment of the ingredients are controlled by an electronic computer. [next]
3) During the stacking operation, the stacker travels back and forth along the length of the stockyard for tiling, and the number of stacked layers is 2584 (the number of times the stacker travels by one line × the number of slots cut at the same time). The double bucket wheel reclaimer Cut it out. Baosteel uses two piles, one pile and one take. At present, a large pile of 180,000 tons needs to be piled up for 10 days. Its length is about 540 meters, the width is 33 meters, and the height is 12.4 meters. It can be used for sintering for 15 days. Among the iron-containing raw materials involved in the accumulation, the powder mine accounts for 57%, the sieve material accounts for 36%, and the miscellaneous auxiliary materials are 7%. In the operation management, a large pile is divided into 4 parts for stacking operation, which is convenient for the accumulation amount. control. The method of mixing and blending is a herringbone cloth, as shown in Fig. 4(a). The cloth method of this method is relatively simple, but the particle size segregation is large, and the effect for storing fine particles is better. Others, such as the Mitsubishi cloth method, the particle size segregation is smaller than the herringbone shape, but the requirements for the stacker are strict. In addition to requiring it to be able to travel longitudinally, it can also move laterally and up and down, as shown in Figure 4(b). The Mitsubishi combination is between the above two, as shown in Figure 4(c).

4) After the neutralization and mixing, the standard deviation σ of the fluctuation of SiO2 can reach 0.15 in the mixed mineral powder sent to the batching tank. There are still some gaps, and the σ is only 0.27.

The Soviet Union had a cold climate and built a covered iron concentrate medium and warehouse and special neutralization machinery. Figure 5 shows the concentrate neutralization process of the Sokolovsk-Selbaysk mining company. The pile is moved by the belt moving trolley on the top of the warehouse in accordance with the prescribed system. There are two piles at the end of the warehouse, each pile is stored. The iron concentrate is 2 to 25,000 tons. It is discharged by the electric shovel with bucket wheel. The electric shovel takes the material along the section of the pile and can be used for radius movement. After the neutralization, the fluctuation of iron content reaches ±1.0%.
Angang's new sintering plant is equipped with two 265 ^m2 sintering machines. Due to its location in the northeastern cold zone, it is equipped with an indoor raw material mixing field, which consists of a concentrate bin and a mixing bin. The concentrate bins are double-row, each column is 22 meters wide and 228 meters long. The various raw materials are separately stored, two piles of each raw material, one pile of feeds and one pile of materials are taken, and the storage time of each pile is 8 days, and the total storage capacity of the two rows of silos is 220,000 tons. There are 3 sets of 20-ton bridge grab cranes, 7 mine tanks, and Ф2500 discs for mining machines and electronic belts. The raw materials in the warehouse are transported from the top belt of the warehouse to the fabric according to the regulations. The bridge grab crane takes the raw materials from the pile horizontally, loads the ore tank, carries out the automatic batching of various iron materials, and then sends them to the mixing bin, the rich mine. The powder can be used as a ingredient or it can be sent separately to the ingredient room. The mixing bins are also double-row, each column is 48 meters wide and 210 meters long. Each stacker and reclaimer are equipped with a capacity of 900 tons/hour. The stacker arm is 33 meters long and the reclaimer is double. Bucket wheel type. The pile height is 13 meters, 32 meters wide and 180 meters long. The storage capacity of each pile is 80,000 tons, which can be used for 6 days. The fabric is herringbone, 500 layers, and can also be used as a herringbone-diamond fabric. Each of the intercepted end pieces can be transferred to another pile of cloth. After the final mixing, the fluctuation of iron content can reach <±0.5%, and the fluctuation of SiO _{2 is} <±0.1%.

China's small and medium-sized steel plants have begun to pay attention to the technical transformation of raw materials and mixing. Figure 6 is the layout of the raw materials mixing field of Maanshan Iron and Steel Co., Ltd. It is characterized by making full use of existing raw material warehouses, and the ancient area is small and new. The increased open-air mixing material pile is adapted to the local conditions, and the storage and mixing of the raw materials are solved under the condition of low investment. The fluctuation of iron content is reduced from ±3% before mixing to ±0.7% after mixing, and a large economic benefit is obtained.

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