In order to solve the difficulties of small and medium steel enterprises in South China during the rainy season operations, E-Steel and Maanshan Iron and summarize the experience of Guangzhou Iron and Steel field mixing of raw materials, the use of indoor mix of programs, and mix warehouse 294 meters long, 44 meters wide (Figure 7) .
Making full use of the potential of existing equipment to carry out the neutralization and mixing of raw materials is an important part of the technological transformation of the old factory. Baotou Steel Sintering Plant utilizes the original three-span concentrate warehouse (length 294 meters, width 90 meters, storage capacity 170,000 tons). Each span has a fixed center reciprocating shuttle medium and belt conveyor, 2 grab cranes, 2 output concentrate moving hopper cars and an output belt, etc., adopting a “one-span ridge and neutralization, a cross-secondary neutralization, The neutralization and mixing operation system of a cross-feeding feed increases the pass rate of fine sputum (including ±0.5% Fe fluctuation) from 47.75% to 80%, and the standard deviation σFe decreases from 0.91% to 0.48%.
There is currently no uniform method for calculating the mixing effect of sintering raw materials. Common methods of maximum and minimum comparison, image method and standard deviation method.
The maximum and minimum comparison method is to analyze the highest and lowest values ​​of a component result through a series of samples. For example, if the iron concentrate has a maximum iron content of 60% and a minimum of 52%, the iron content fluctuates by ±4%. This method is relatively simple. It does not reflect the change frequency and change of the rest except the highest and lowest values. Amplitude. For example, two groups of ore, the fluctuations are 5%, but the first group of 3% of the 3% of the 80%, while the second group of only 60%, it is clear that the first group of uniformity is higher than the second group.
The image method uses statistical images to show the uniformity of each component, and can represent the true image of the thing, and it is clear at a glance. The downside is that you can't use simple text to describe it. Figure 8 is a graphical statistical method of iron-containing fluctuations.
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The standard deviation method is a more scientific representation, which is calculated as follows:
Where σ—the standard deviation, that is, the percentage of the absolute value of the standard deviation of the content of a component in the raw material, the smaller the σ value, the more uniform the composition;
x———data for each sampling analysis;
n———Number of sampling analysis.
The mixing efficiency η is calculated by the ratio of the standard deviation before mixing and after mixing, that is,
Where z i ——— the number of layers of cloth of a certain material;
z———the total number of layers of material pile fabric;
σ i ———corresponds to the standard deviation of the zi layer;
i———variable component number;
k———Number of different types of materials.
Ways to improve the efficiency of mixing are:
1) Increase the number of layers. The relationship between the mixing efficiency and the number of layers of the stack can be expressed by the following formula:
Since the composition fluctuation of the mixed raw material does not obey the normal distribution and the actual mixing process is very different from the ideal process, this formula can only be qualitatively explained. In addition, increasing the number of layers is also limited by the maximum particle size of the material and whether the adjacent layer is statistically independent in its quality fluctuations. The general theoretical stacking layer (in terms of the number of times the stacker travels one way) is roughly 500 layers.
In production, the number of raw materials to be fed into the pile is often taken into account, so the number of layers is equal to the number of single strokes of the stacker multiplied by the number of batch tanks at the same time. This is called the actual stack level. Obviously, in the case where the number of theoretical stacking layers is constant, the number of stacking layers can be increased by increasing the number of batching tanks for simultaneous operations.
2) Adjust the position of various raw materials in the cross section of the pile by rationally selecting the composition of the ingredients. In order to reduce lateral fluctuations, several materials with the highest grade differences should be combined. The raw materials thus combined are mixed into a "one" material close to the average composition of the pile during the batching process, thereby narrowing the difference in composition with other batch materials. Reduced lateral volatility. For example, Baosteel stipulates that high SiO 2 raw materials are simultaneously compounded with low SiO 2 raw materials.
Reasonable arrangement of raw materials into the stack can reduce lateral fluctuations. For example, coarser-grained raw materials are avoided in the final pile, and concentrates with larger moisture are prevented from being finally piled up. Heteroaryl auxiliary raw material such as manganese ore, iron tablets, dusts should be deposited in the middle of the stockpile cross-section, in addition higher grade layer deposition starting material can greatly reduce the fluctuations in the feed composition.
In addition, the water content of the raw materials and the method of stocking also have an impact. The infiltration of the concentrate with more than 8% moisture into the limestone or dolomite powder can greatly improve the mixing efficiency.
1. The arm and crossbeam etc. are reinforced with more load than before, and multiple improvements;
2. Each single hydraulic system has balance valve and hydraulic lock, more secure and reliable;
3. The patent design of auxiliary hooks: with high, low and neutral gear, it adopts normally shut hydraulic brake, more effective. hoisting is more secure, noobject slide- down(double- hook type and single- hook type are optional)
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