Hematite beneficiation process roasting magnetic separation process
Roasting magnetic separation is one of the effective methods for dealing with weak magnetic and complex iron ore, and it is also a relatively mature method. In addition to increasing mineral magnetism, magnetization roasting can also eliminate some harmful impurities such as crystal water, carbon dioxide, sulfur and arsenic in minerals; and can make hard and dense ore into loose structure, which is beneficial to reduce grinding cost. However, due to the high capital investment and production costs, the promotion and application of this technology is limited. When the magnetization amount of fuel consumed during firing of fuel calculated standard 4% to 6% of the ore, which costs 60% to 70% of the cost of baking, without coal gas source, gas generating station requires special construction the supply of gas , the proportion is greater. The cost of the general roasting itself accounts for 45% to 65% of the total roasting magnetic separation cost. The 75-20mm block vertical furnace reduction roasting process is mature, and has long-term production practice experience. The 20-0mm rotary kiln magnetization roasting production practice is less. For the fine magnetic separation, re-election, flotation and other methods commonly used in powder ore and their joint processes are selected. Therefore, some early foreign roasting plants have switched to other methods.
The quality index of magnetization roasting is generally expressed by the degree of reduction R: R = (FeO / TFe) * 100%, where FeO refers to the content of FeO in the reduced calcined ore, and TFe refers to the content of total iron in the reduced calcined ore. In the case of ideal calcination, if the hematite in the ore is all reduced to magnetite, the reduction roasting effect is the best and the magnetism is the strongest. At this time, the degree of reduction of the calcined magnetite was 42.8%, which was used as a measure of the quality of the calcined ore. If R>42.8%, it indicates that the calcined ore has been reduced, and some of the magnetite has become FeO; if R<42.8%, it indicates that the calcined ore is insufficiently reduced, and some of the hematite is not reduced to magnetite. However, the transformation of the ore during the roasting process is not always uniform, and the above values ​​often do not accurately reflect the quality of the roasting ore. Do good separation effect as calcined Anshan hematite quartzite, when the ore particle size of 75 ~ 20mm, the degree of reduction of 52%, it should choose the optimum degree of reduction for different types and different particle size of the ore.
In 1924, China built the first hematite shaft roasting magnetic separation plant, which led to the emergence of “Anshan-type roasting shaft furnaceâ€, which was rebuilt several times in more than 40 years. In the 1960s, it was expanded from the original 50m? shaft furnace to 100m?, and it was applied to the wine steel concentrator, thus improving the stand time capability of the shaft furnace. In the 1970s, the original 50m? shaft furnace was transformed into a cross-beam type shaft furnace. Under the condition of not expanding the size, the furnace structure was changed to increase the furnace capacity to 70m, the capacity of the stage was increased by 74%, and the heat consumption was reduced. %. In the roasting process, the raw ore is classified into the furnace for roasting, and the magnetic pulley is used to form a semi-closed roasting process, which can improve the recovery rate of the concentrate.
For Anshan hematite - quartz rock, use of 75-20mm shaft furnace and blast furnace coke to hematite mixed with the reducing gas is heated to produce artificial magnetite, magnetic separation of iron concentrate then taste and recovery 65.82% 78.41% of the indicators.
The second selection workshop of Qidashan Concentrator used roasting magnetic separation process. After magnetization roasting, the complete hematite ore dressing process consisted of continuous grinding, magnetic separation and stage grinding, and magnetic separation-re-election. The continuous grinding and magnetic separation process is relatively simple. It is two-stage continuous grinding, one-stage dewatering tank, one-time magnetic separation and one-stage fine screening operation. The fine sieve screens out the concentrate, and the fine sieve returns to the second stage grinding and grinding. Re-election; stage grinding, magnetic separation-re-election process is more complicated, it is a medium-magnetic tailing after grinding, and the medium-magnetic concentrate is combined with a coarse subdivided cyclone to form a rough selection spiral chute, a selection The spiral chute is selected as the concentrate, the rough-selected spiral chute, the tailings in the selected spiral chute are combined into the secondary grading cyclone, and the secondary grading cyclone and the second-stage mill constitute closed-circuit grinding. Continuous grinding, magnetic separation and stage grinding, magnetic separation-re-election of concentrates are combined into a second-stage dewatering tank to produce the final concentrate in the workshop. The comprehensive technical indicators are: the original ore grade is 29.26%, the concentrate grade is 63.26%, the tailings grade is 10.44%, and the recovery rate is 77.03%.
The roasting magnetic separation process applied in the 1970s has the characteristics of simple process flow. However, the main problems are as follows: 1. The roasting magnetic separation process has high energy consumption and high production cost; 2. The ore has high magnetic coercivity after roasting, and magnetic inclusions are easily formed during the magnetic separation process, which affects the mineral processing technical index. Due to the above problems, the process has been gradually replaced by other combined mineral processing equipment such as strong magnetic-reverse flotation.
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