Preparation of carbon bearing pellets: weigh and mix the raw ore, internal coal blending and binder according to a certain mass fraction, add a certain mass fraction of water to mix, and then press the roller ball press to obtain carbon bearing pellets.
Determination of green ball strength: including the falling times and compressive strength of wet ball and dry ball. The number of dropping is the number of times that the pellet falls on the 100mm thick steel plate from 50cm height until it is broken. Generally, 4 times meet the requirements. The compressive strength is measured by the intelligent particle strength tester.
Direct reduction roasting magnetic method: after determining the good binder of the pellet, the pellet is directly reduced roasting and grinding weak magnetic separation test. Put the pellets in graphite tongs, cover them and put them into muffle furnace which has been heated to 1200 ℃ for different baking time, take them out and put them into lignite to ensure that the pellets fall to room temperature in reducing ring atmosphere, after the pellets are broken, they are separated by two-stage grinding magnetic separation to obtain direct reduced iron products.
Effect of different binders on the strength of green pellet
A certain amount of raw ore was mixed with 20% Ningxia lignite, proper amount of water and different kinds of binders to carry out ball pressing experiment. The experiment shows that the binder plays an important role in the cold bonded pellet. It can produce a series of physical and chemical changes in the pellet under normal temperature or special conditions, so as to play a role of bonding and improve the strength of the pellet. The binder used in the test includes inorganic binder and organic binder.
Effect of composite binder on the strength of green pellet
It is found that different binders have different effects on improving the falling and compressive strength of wet and dry balls from the single binder test. Therefore, the composite binder is considered to be used and the advantages of various binders are utilized.
Influence of roasting on pellet strength
The compressive strength of dry pellets with different binders is different greatly, but the change trend of the strength is basically the same in the process of high temperature co firing, and the compressive strength of pellets decreases in the first 0-2 min of roasting. At 2-4min, the change speed of the pellet compressive strength slows down, and at 4-8min, the pellet strength increases gradually.
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