DE2506316A1 - PROCESS FOR CRUSHING PIT-MOISTURE CRUDE PHOSPHATE - Google Patents

Description

Friedrich Dhde GmbH ZDUD4 I Ο

Dortmund

Own symbol: Io o25

Process for the comminution of rock phosphate that is moist in the pit

The invention relates to a method for comminuting moist, pre-crushed rock phosphate into a rock phosphate with a grain size of 80% below 2 μm.

Rock phosphate is a solid, coarse-grained mineral. Among other things, it is used to produce phosphoric acid by reacting with sulfuric acid used. For this reaction it is necessary to reduce the rock phosphate to at least 80% to a grain size of less than 2 mm to zoom out.

For the comminution of the coarse-grained rock phosphate, two methods have so far proven to be applicable, namely dry grinding and wet grinding.

With dry grinding, the coarse-grained rock phosphate, which can have a moisture content of approx. Io% and more, is first subjected to drying to approx. 1 - 3% water content. This drying takes place in large heated drying drums. Since all rock phosphate, including the fine-grained part, is dried, a high heating energy consumption is inevitable. To reduce the natural moisture from, for example, 14% to a residual moisture of approx. 3%, around 50 kg of heating oil / t ^ ₂ ° 5 are required. ^The grinding of the dried phosphate rock is done in mills with an energy demand of the order of 7o kWh / t ^ 2 ⁰ S * ^{To Trennun?} T äes screening material into fine and uberkom air classification was applied.

When wet grinding the rock phosphate in a ball or rod mill, it is necessary to increase the moisture content to over 50%. At moisture contents below 5o%, the grinding media and grinding surfaces are encrusted with the rock phosphate and bonded _g the Äufmahlung is prevented. 609836/0019

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The rock phosphate ground with a water content of over 50% must then be drained again for further processing «This drainage causes difficulties because filter cloths e with large pore diameters only insufficient separation of the fine fraction of the rock phosphate from the liquid and clog filter cloths with small pore diameters.

A combination of grinding and sieving is used when grinding applied by crystals in which raw phosphate was ground but so far only a dry grinding with sifting through an air stream State-of-the-art, as all screen types are caked of the coarse grain with the fine grain only poorly the coarse grain of that Fine grain separated.

It should be noted that a sieving of a completely dry Rock phosphates is quite possible. With humidity but between The grain is electrostatically charged from 1 to about 5%, and bridging occurs during sieving and the fine grain separates of the coarse grain is very bad. Over half of that in the starting product Any fine grain that is present can thus be carried away into the coarse grain.

The invention is based on the object of pit-moist rock phosphate in a simple manner in terms of apparatus, without the use of heating energy and avoiding the disadvantages of the known processes in one to transfer comminuted rock phosphate with a high fine grain content.

This Atifgabe is achieved according to the invention in that the pit-moist The rock phosphate is subjected to at least two sieve classification and the material to be sieved is subjected to the last classification in a smoothing roller mill is ground.

It is essential to the invention that the pit-moist rock phosphate is one is subjected to at least two-stage sieve classification. Just coarse-grained rock phosphate with a grain size larger than 2 mm arrives

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on .the roller burnishing mill. The roller burnishing mill should run at different speeds of the two roller burnishing rollers. The latter measure results in self-cleaning of the rollers as a result of the differential circumferential speed present in the roller gap. The dreaded caking of ground phosphate on the rollers does not occur. The grain that has passed between the rollers is ground by radial and tangential forces, the latter resulting from the differential peripheral speed. '"_ , .-": -.--

The inventive method has the essential advantage of direct processing of pit-moist rock phosphate. Neither one Apparently and energetically expensive drying with subsequent grinding with high power expenditure and an excessive increase in moisture to over 50% with their problem of effective filtration of the rock phosphate mash are required. The inventive Process leads directly to a very fine-grained rock phosphate, whose natural moisture content proves to be advantageous e.g. for further processing into phosphoric acid by means of Sulfuric acid.

The following example gives numerical values for a comminution according to the invention of rock phosphate. The procedure is limited does not refer to these numerical values, but also includes those that are in the approximate range.

1. Wet sieving on vibrating sieves

Moisture of the rock phosphate 13.8%

Grain size starting material

76.3mm 12.4%

6.3. - 2 mm 14%

2 - 1 mm 13.2%

under 1 mm 6o, 4%

It was sieved on two sieves connected in series.

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Sieve inclination 12 for both sieves

1o o25

Mesh size sieve 1 sieve

4 mm 2 mm

Feed quantity sieve 1: 75 kg in the overflow

as coarse grain: 19 kg

Passage: 56 kg

This "passage" served as the task for the second sieve.

in overflow

as coarse grain: 4 kg

Passage: 52 kg

About 3.5% of the grain under 1 mm still adheres to the oversize grain of 19 or 4 kg.

2. Milling in a roller burnishing mill

Circumferential speed: ^u i ⁼ 11.1 m / s

U ₂ = 13.4 m / s

Grain size of

Feed material: overflow of the 2 mm sieve from (1)

Humidity des
Incoming goods: 13, 8th % Bulk weight: 1, O t / m ³ Gap width of the
Finish rolling mill: O, 7th mm

The grist has the following fine grain content:

2 - 1 mm 18.18%

0.5 - 1 mm 24.05%

o.2 - o.5 mm 35.93%

below 0.2 mm 21.84%

spec. Energy requirement: 13.5 kWh / t PO ₁ -

Claims (4)

1ο ο25 patent claims 1. Process for the comminution of moist, pre-crushed Rock phosphate into a rock phosphate with a grain size 8o% below 2 mm characterized by that the moist, pre-crushed rock phosphate subjected to at least two sieve classification and. the coarse grain of the overflow of the sieve classifications in a roller burnishing mill to one grain size is crushed below 2 mm. 2. The method according to claim 1, characterized in that the first sieve classification is a sieve of a maximum grain size of 4 mm and that the second sieve classification has a sieve material with a maximum grain size of 2 mm. 3. The method according to claim 1, characterized in that the screenings at different speeds of the two Smooth rolling is ground. 4. Apparatus for performing the method according to claim 1 to 3 characterized by the combination of a double sieve classification with a roller burnishing mill with an average peripheral speed of 12 m / sec. 609836/0019