CS201157B1 - Process for enriching fine ferrous magnezite raw materials - Google Patents

Description

(54) Method of enrichment of fine-grained ferric magnesia raw materials

The invention relates to a method for enriching fine-grained ferric magnesite raw materials and is based on a low-temperature heat treatment of the input material allowing its subsequent wet magnetic separation.

The previously known and used methods of magnetizing roasting and magnetic separation of ferric magnesite feedstocks are only suitable for lump magnesite feedstock, which can optionally be pretreated by manual picking or sorting in heavy suspensions.

The dry magnetic separation of ferric magnesite fried at higher temperatures is less effective for fine-grained materials, because at increased levels of impurities - quartz, lime and iron oxides, which fine-grained materials exhibit compared to lumps of magnesite concentrates, new chemical compounds are formed during roasting and reacting to each other and mixing to such an extent that the separation of impurities from the useful magnesite component by dry magnetic separation is ineffective. Wet magnetic separation is also unsuccessful in this case. In addition, all the carbonates present in the starting magnesite feedstock are converted into oxides which undergo hydration during wet magnetic separation and partially dissolve in the water used by magnetizing roasting at higher temperatures as a function of roasting time.

Therefore, to obtain dense magnesite clinker, the wet magnetic separation concentrate must be calcined, which increases the total thermal energy consumption for clinker production.

201 1> 6

201 157

In addition, the water used may be purified from dissolved compounds prior to reuse in the process.

Said drawbacks of the known methods of enrichment of fine-grained ferric magnesites are thus eliminated according to the invention. they are subjected to a low temperature heat treatment at a temperature. and a certain composition of the furnace atmosphere so that only iron (II) carbonate decomposes and is converted to the magnetically active oxide form, while the magnesium and calcium carbonates do not decompose.

This process is preferably carried out at a temperature of 450 to 550 ° C with an oxygen content in the surrounding furnace atmosphere of 8 to 15% by volume. The material's residence time at this temperature is specific to each type of feedstock.

The heat treated material thus prepared is then subjected to wet magnetic separation and the concentrate obtained is treated according to the intended use. Process water can be used in a closed cycle during wet magnetic separation of low temperature treated fine-grained magnesite because it is not enriched with soluble components from the treated feedstock.

A new and higher effect of this process is that at the temperature, time and suitable thermal spraying atmosphere used, the decomposition of ferrous carbonate and its conversion to oxygen with strong magnetic properties is achieved, while the magnesium and calcium carbonates remain unchanged. The material thus prepared can then be subjected to wet magnetic separation without fear of hydration of the magnesium and calcium compounds and of chemical contamination of the water used. The finely divided magnesite concentrate having a higher content of magnesium oxide MgO, and the waste will separate the significant level of impurities such as silica Si0 ₂ and calcium oxide CaO. For the production of the finished magnesite clinker or calcinate product, the Sae1 concentrate obtained is treated in the same manner as e.g. magnesite concentrate obtained by a more complex and costly process - flotation.

Example 1 waste from magnesite flotation of less than 0,1 mm grain size and chemical composition: SiO ₂ 6.27% CaO 5.68% ^Fe 2 ° 3 3.22% with. FROM. 49,29% he was brindle at 500 ° C for 1 h under atmosphere containing 8 to 15% oxygen 0 ₂ and then Processed on a wet magnetic separator at mash concentration 500 g / l and size excitation current 12 A (0.99 T) with weight yield concentrate 56% o Ingredients: SiO ₂ 3.3% CaO 4.15% ^Fe 2 ° 3 3.81% with. from. 45,6%

201 157

By calcination of the concentrate thus obtained, a raw material suitable for the chemical production of MgO containing:

SiO ₂ 6.06 CaO 7.62 ^Fe 2 ° 3 7.0 with. from. max. 1.0 Compared to calcinate, which would SiO ₂ 12.35 CaO 11.18 ^Fe 2 ° 3 6.18 with. from. max. 1, o

its use of the magnesium calcate of the concentrate obtained by low temperature roasting and wet magnetic separation is substantially more advantageous since, at a higher content of the active ingredient, MgO contains substantially less heifers and hardly removable CaO components.

Example 2

Subtractive fraction of granulometric treatment of magnesite with a grain size of 0.2 to 1 mm in chemical composition: SiO ₂ 0.29% CaO 3.24% ^Fe 2 ° 3 3.70% s, ž. 49.7% was annealed 0.5 h below atmosphere with a content of 8 to 15% 0 ₂ and then wet-processed magnetic separator at concentration mash 500 g / l a excitation current size 12 A (0.99 T) with concentrate weight yield 61% composition: sio ₂ 0.22% CaO 2,50% ^Fe 2 ° 3. 3,98% with. from. 47,5%

As in the previous example, due to the low temperature heat treatment of the magnesite raw material, the pollutant content of the concentrate obtained by wet magnetic separation was reduced.

Claims (1)

OBJECT OF THE INVENTION Process for enriching fine-grained magnesite raw materials containing isomorphically bound iron, characterized in that the fine-grained magnesite raw materials are low-temperature roasted at 450-550 ° C in an atmosphere containing 8-15% by volume oxygen to enhance the magnetic properties of the magnesium rich phases.