DE2018105A1 - Method and device for sieving - Google Patents

Description

Eugene Marie BURSTLEIN, Meudon-Bellevue, Hauts de Seine,

France

Method and device for sieving

The invention relates to a method for sieving dry or moist substances in grain or powder form mithilf e of vibrating screening devices.

Sorting and classifying according to grain size of such substances, raw materials, such as coal, ores, rocks,
Sand, gravel and the like, or Pertik products such as coke, artificial fertilizer, salt, sugar and the like, are of great importance in today's industry

This is generally done mechanically on a single-stage or multi-stage vibrating screening device.

009887/1291

In a single-stage sieving device, the sieve surface gradually divides the material to be sieved into two grain ^{size fractions, the "sieve passage 11} , which consists of the grain sizes that are smaller than the mesh size and has crossed this sieve surface between the entrance and a certain point behind it, and the" Residue "which has not passed through the sieve and consists on the one hand of grain sizes larger than the mesh size and on the other hand consists of smaller grain sizes that do not cross this sieve surface up to this point Advancement on the sieve surface between the entrance and the point under consideration gradually in weight, the weight loss being equal to the weight of the sieve passage i3t that could traverse the sieve surface in this distance.

This also applies to a screening device with η stages, at which the weight loss that the η residues experience in their preliminary evaporation on the η levels in total, is equal to the weight of the sieve passage that has passed through the sieve surface of the lowest stage.

In the known sieving process, the layer height of the one or those moved forward on their respective sieve surfaces increases Residues from the entrance. the exit to off. at

Example wise

a product with a content of / p = 70 % of grains that are smaller than the mesh size, the ratio * - * · the layer height at the entrance and that at the exit is

about 0.33? ie the layer height h ^ at the exit of the sieve surface is about 3 times smaller than the layer height Iolq at the entrance «

009887/1291

The sieve passage crosses the sieve surface with a relatively low mean specific Throughput, therefore the sieve must have very large

Have 2 measurements of, for example, 1UO m to at a mesh size of 5 mm a maximum throughput 800 t / h sieve passage of a viscous, moist and clayey iron ore or a throughput of To allow 400 t / h of dry coal to pass through the sieve, while the actual through capacity such a sieve area is 4 to 5 times larger.

The known methods also do not allow the Production of screening devices with a very large surface area, as they are required today in order to cope with the large throughputs with a single device, resulting from the current concentration of the raw material extraction and processing companies. For example, to increase the throughputs mentioned above reach, at least four devices would have to be connected in parallel to form a screen area of 100 m be, whereby the total flow of the screenings in a disadvantageous manner in at least four fractions would have to be shared.

In view of the high investment, operating and maintenance costs of the screening devices, it is "very useful instead of the known screening method to use a more effective method in which on the one hand the specific mean throughput of the sieve passage through

009887/1291

ORIGINAL INSPECTED

-it-

Screen area and, on the other hand, the dimensions of the screen devices are increased

To this end, the method of the invention is essential characterized in that the layer height of the residue on the sieve surface is from a value Ho at the entry point up to a higher or at least equal A'ert H an. an underlying point is increased by the values of the feed rate V of the residue and the width 1 of the sieve surface are chosen so that the product V.l proportional to that of the lag between these weight loss suffered at both points and inversely proportional to the increase in layer height between them decreases at both points.

Further details of the invention emerge from the following description of two exemplary embodiments are shown on the accompanying drawing. On this drawing show:

FIGS. 1 and 2 are diagrams for the case of viscous iron ore.

Fig. 3 and * J diagrams for the case of dry coal.

Figures 5 and 6 are a schematic side view and a Top view of a sieve device for carrying out the invention Procedure.

These two examples were among the many comparative examples carried out on a semi-industrial scale

009867/1291

2018 108 -5-

Try on a wide variety of fabrics selected there

XJ

they show that the values of ΰ,> 1 as a function of that of the residue on the Siebflächeni traversing path in depend essentially on the viscosity of the residue and its concentration of small grains.

Before treating a certain material to be screened, diagrams corresponding to FIGS. 1 and 2 or 3 and k must first be drawn up according to the invention, these diagrams being determined by experiments on a semi-industrial scale.

Example 1

In the case of a very moist and clayey, i.e. extremely viscous iron ore, which was sieved on a sieve with a mesh size of 5 mm and in which the proportion ρ of grains that are smaller than the mesh size was 70 % , the best results were achieved, by increasing ΰ according to the solid line in FIG. 1 * ⁰

These results are shown on the diagram of FIG. 2 with a solid line. This diagram shows the passage efficiency θ of the sieve passage as a function of the ratio γ , where L is that of the residue on the

1
Sieve area from the entrance to the path traversed and L ^ is the path that the residue must traverse in total so that θ = 95 % .

The broken lines on these two diagrams show the results for known ones for comparison Methods that work with a ratio of r <1.

009887/1291

The path that the residue on the sieve surface must traverse in the process according to the invention in order to reach O = 95 1 ° is therefore 2.55 times smaller than in the known processes. The specific mean throughput of the sieve passage is thus 2.55 times larger, so that a sieve area of 100 m is traversed by about 2000 t / h of the ore in question instead of only 800 t / h.

Example 2

In the case of a dry coal without remarkable viscosity, which was now sieved on a sieve with a mesh size of 5 and in which the proportion ρ of grains smaller than this mesh size was 65 h , the best results were achieved by changing the layer height according to the solid line of Fig. 3 and 4 was kept practically constant ·

For comparison, the curves shown interrupted show the results that can be reached in the known V _er f _a lead at the input to the output to decreasing layer height.

In this case, the specific mean throughput could be increased by 2.1 times, so that, according to the invention, with a sieve area of 100 m ^2, 840 t / h instead of 40o t / h sieve passage is obtained. *

All the results obtained with substances of any kind have shown that the mean specific throughput the sieve passage was more than doubled in all cases compared to the results of the known methods,

009807/1291

201810S

if & ie values «- ) / 1 depending on the viscosity

0
of fabrics, lenau «.

These surprising results can be explained as follows: So that the small grains make up the sieve surface
can traverse, you must first with this in
L-erührunr be splendid. The "through-phase of the _Siebdurch;:. ANF's" t ~ so eht necessarily preceded by a "RuckstandsabsonderunfT.spha.ye", wherein it comes in the residue to a lamination · by the small grains gradually * n lower layers and the large grains are collected in the upper layers.

This stratification is brought about by the vibrating motion of the sieve surface, in which the large grains are due to the difference in mass and kinetic energy
be thrown away more quickly than the little ones.

The "speed of deposition" of the small grains, i.e. the speed of their downward movement, increases with increasing Layer height and increasing viscosity of the residue decrease very quickly.

The mean specific throughput of the sieve passage
does not depend on the throughput capacity of the sieve surface, but on the throughput in which the small grains reach the sieve surface, or directly on the presence of a layer with a high content of small grains
above the sieve surface.

009887/1291

BAD ORiGlNAt

This means that in order to achieve high throughputs, the screen surface must be fed in the correct way.

In the known screening process, the screen surface is not fed enough over the entire length. On the inlet side, where the residue has a high content of small grains, the sedimentation of these grains is too low, since the excessive layer considerably reduces the rate of deposition of the small grains, which have to travel a long way to reach the sieve surface. On the inlet side, the screen surface is clearly insufficiently fed, since there are no longer enough small grains due to the insufficient layer height. For these reasons, the mean specific throughput of the sieve _{through K} "angs in the known processes hardly reaches a quarter of the actual throughput capacity of the sieve surface.

If, on the other hand, the procedure according to the invention is proceeded, the sieve surface is fed much better, since the layer heights - small on the entry side and large on the exit side - correspond to the content of small grains and the viscosities of the residue, which are high and high on the entry side the discharge side are coagulated, which results in a considerable increase in the mean specific throughput of the sieve throughput, which can reach 80 % of the actual throughput capacity of the sieve surface.

The invention thus allows the production of screens large area and with high throughputs, as required by modern industry.

009887/1291

GftiöiNAl.

201810S

According to the invention, this increases the layer height achieves that the values of the feed rate V des Residue and the width 1 of the sieve surface are chosen so that the product V »l according to the formula:

XI ₁ - ¹ = -j «(1 _ Qp) (1)

ο 0

decreases in which

ρ is the content of the substance in grains that are smaller

than the mesh size

θ is the mean transmission efficiency, i.e. the percentage at p, which is the sieve area between the entrance and the one behind it Point could traverse, and

V _Q and l _{o are} the values of V and 1 at the entrance to the sieve surface

If 1 = 1 _Q , i.e. if the width of the sieve surface is constant over its entire length, the formula (1) becomes:

£ - = If (1 - Μ (2)

The value of the product V _Q 1 _Q is given by the formula:

^V o ¹ O = H ₀ (3)

009887/1291

-10- given in which

Not in any particular case

own constant given by the expression:

K = τ (k)

is given in which

T is the hourly number of tons of the substance to be treated and

d is the bulk weight of this

And V and V _Q , 1 and 1, H and H in m / sec, m and mm, respectively

are expressed

Numerical examples are given below for the two examples mentioned above:

Example 1 (Fig. 1 and 2)

3000 t / h of the highly viscous iron ore with a content of 18 i> water and 9% of clay, and a total grain range of 0 to 5 mm ^ will now be screened on a mesh screen. 5

d = 2.5 P = 0.7

009887/1291

BAD ORIGINAL COPY

ι
- it -

The required transmission efficiency is θ = 0.95. The required sieve area is thus about 100 m, ie has a constant width of 1 = 1 _Q = 3 m and a length I ₁ = 33 m.

According to the formula
K = ^T

3.6-2.5

Since the substance is very viscous, it is advisable that H does not exceed the dimensions of the largest grains contained in the fabric, i.e. H = 4 5 mm

According to the formula (3):

^v o = γτϊγ = - ^ h = ² ^ ^m / ^sec

OO

According to the formula (2):

H H

V = V ₀ ^ j (1 - Op) = 2.47 -§ ■ (1- 0.7 Θ)

The experimentally determined diagrams of FIGS. 1 and 2

yield the values \ on ττ and of Θ. at

one obtains in each case:

009887/1291

ORfGINiAL INSPECTED °° ^PY

jr = 1 2.55 5

e = ο ο, 57 ο, 95

This results in:

V _Q = 2.47 m / sec

^V 0.5 ^{= 2} ^ ⁷ * 2755 ( ¹ - ° '7'O.57) = ° »58 m / sec V ₁ = 2.47 · \ (1-0.7 * 0.95) = 0, 16 m / sec Example 2 (Fig. 3 and 4)

1350 t / h of dry coal with very low viscosity and a total grain range of 0 to 3 ° rom sieved on a sieve with a mesh size of 5 mm.

d = 0.7 P = 0.65

The required efficiency is θ = 0.95, the

2 required sieve area is about 100 m, i.e. has a

constant width of 1 = 3 m and a length L. = 33 m.

According to formula (4):

K - _4_ - 1,350 _

Since the carbon has a very low viscosity, H can be equal to 4 times the dimension of the largest in the fabric contained grains, i.e. H = 120 mm.

0 09887/1291

ORIGINAL INSPECTED

2018 $ 10

-43-

According to formula (3):

^v o -

According to the formula (2):

H Η _Λ

V = V ₀ gäO-θρ) = 1.50 g2. (1-0.65 Θ)

The experimentally determined diagrams of FIGS. 3 and

H
provide the values of w— and of Θ.

^H o
at

£ - = ο. o, 5

you get in each case:

■ Π. Λ Λ Λ

j-. 1 1

θ = 0.60 0.95

From this we get:

V ₀ = 1.50 m / sec

V ₀₅ = 1.50 (1-0.65 * 0.6) = 0.92 m / sec V ₁ = 1.50 (1-0.65-0.95) = 0.57 m / sec

009887/1291

The method according to the invention can be carried out in various ways. Benin sieve area with constant For example, width can be done as follows:

a) When the screen surface is from the inlet side to the outlet side is too inclined, their slopes and slopes are chosen so that those defined by the formula (2) are selected Speeds.

b) If the screen surface consists of several sections, each of which has its own drive mechanism, so these independent mechanisms give the individual sections different oscillating movements, whose amplitudes, frequencies and throw angles are chosen so that the speeds defined by the formula (2) receives.

c) If the screen surface is inclined and consists of several sections, each with its own drive mechanism exists, then the slopes, gradients, amplitudes and frequencies and throw angles are chosen so that you can obtained speeds defined by the formula (2). In general, one of several sections each with its own drive mechanism Screen area with variable width, gradient, gradients, amplitudes. Frequencies and throw angles provided all of these factors are chosen so that the product V-I decreases according to the formulas (1), (3) and (4) .

009887/1201

The feed rate of the substance can also be adjusted at the entrance to the sieve surface and the removal of the residue to drink this screen surface can be changed by Obstacles are provided

For example, in order to achieve a speed of about 2.50 m / sec, which may be necessary on the inlet side of a large, * K) m long sieve surface divided into ten sections, the ^? These sections are preferably set in a straight or elliptical oscillation movement, Ug is further characterized by a strong acceleration and a large amplitude. The screen surface is inclined by about 35 ° and the material to be screened is fed in at a speed of about 2.90 m / sec. In contrast, in order to achieve a speed of about 0.03 m / sec, which may be necessary in the output section of the same device, this section is set in an oscillating movement of high frequency and low amplitude, it is given an approximately horizontal position and the residue is drained off slowed down by obstacles. These obstacles also cause eddies to occur, which is beneficial for cleaning the final residue.

To obtain speeds of 1.20 m / sec on the input side Work up to 0.30 m / sec on the output side, as is often the case for a medium-sized screen area with a. Length of 20 m and six sections are suitable, it is sufficient to rely on a single factor, for example the slopes or the movements of the sections.

009887/1291

BAD OFSlGiNAL,

The method according to the invention has the advantage that the 'screen area is reduced by at least 50% for a certain hourly number of tons of the substance to be treated, or that the hourly number of tons is at least doubled for a given screen area.

According to the invention, it is thus possible to screen devices with a large specific throughput and very large area ai build.

This last point is of particular importance

to, because with the same number of tons to be treated every hour βίο
ne single device of 100 m at least eight in parallel

replaced switched devices of 25 m, which is a considerable Reduction in space requirements, which represent investment and production costs.

FIGS. 5 and 6 show an embodiment of a highly effective screening device, at «elcher the invention Procedure is used.

The sieve area of this sieving device is about 100 m ^, it has a length L = 33 and a constant width of 1.5 .

This sieve area is divided into ten sections 1 to 10, which are attached in fiahmen 11 to 2ö.

These sections are against the horizontal rights by the following Inclined angle:

009887/1291

BAD ORiGINAL

35 ° section 1 31.5 ° section 2 27 ° section 3 21.5 ° section 15.5 ° section 5 8.5 ° section 6th 2.5 ° section 7th O ⁰ section 8th -2 ° section 9 -5 ° section 10

Mechanisms 21 to 30 attached to the 'frame set each section in a different, preferably straight or elliptical oscillating movement. This swing motion ^ · has the following characteristics in section 1:

Throwing angle 25 °
Oscillation path 25 mm
Frequency 650 t / min

(The throwing angle is the angle at which the grains of the The residue is thrown into the air opposite the sieve surface).

The oscillating movement of section 10, on the other hand, has the following features j

Throwing angle 70 ° /. Oscillation path 6 mm
Frequency 1400 t / min

009887 / 12Ö1

The characteristics of the oscillating movements of the intermediate sections 2 to 9 change regularly within this * two extreme values.

The material to be screened is transferred to the screen surface by a conveyor M upset. The sieve passage, which consists of grains that are smaller than the mesh size, falls through the >> passage funnel 31 to ^ O on the conveyor * J-2. The grains, which are larger than the mesh size, as well as the small grains that could not pass through the sieve surface, fall on the conveyor ^ 3.

000887/1291

Claims (2)

Claims ^Λ . Process for sieving dry or moist substances in grain or powder form, characterized in that the layer height of the residue on the sieve surface is increased from a value (H- ') at the entry point to a higher or at least the same value H at a point behind it by choosing the values of the feed visual velocity (V) of the residue and the width (1) of the sieve surface so that the product V »l is proportional to the weight loss suffered by the residue between these two points and inversely proportional to the increase in bed height * decreases between these two points. 2. The method according to claim 1, characterized in that that the increase in the layer height is achieved in that the product V ·! according to the formula: ti decreased wii? d j in what _ ρ the collected grains of the screened material !, the smaller than they are half a millimeter, θ, the average of the Seventh Burchgangsaüsbeute ■ "4.h. Her irozeirfesatz is ρ of that observed between the screen surface and the CBFC Bisgarigsptinkt, could cross point lying behind ^ _V-0 and l _o, the values of f 1 and at the input of Sieve marriages are, which according to the formula t 009887/1291 BATH ORIGINAL are interdependent in which is a constant for each particular case, where T is the hourly number of tons of the substance to be treated and d the rubble is weight, V and V, 1 and 1, H and H expressed in m / sec, m and mm, respectively are and Q and j | Charts are taken, the reference in dependence ⁰ of the traversed by the path residue were determined by test experiments. 3 · Method according to claim 1 or 2 in the case of a sieve area with constant width, characterized in that the increase in the layer height by reducing the value of the speed according to the formula: f- = if (1-Op) (2) is achieved. 009887/1291 ^ t Method according to claim 3 in the case of one of the Inlet side inclined sieve surface towards the outlet side, characterized in that the slopes and slopes the sieve area can be determined so that the speeds defined by the formula (2) in claim 3 (V) can be achieved. 5 »Method according to claim 3 in the case of one of several Sections each having their own drive mechanism, characterized in that that these independent mechanisms move the individual sections into different oscillating movements move whose amplitudes, frequencies and throw angles are determined so that the formula (2) in Claim 3 defined speeds can be achieved * 6 «Method according to one of claims 3» ^ or 51 thereby characterized that the slopes and inclines that Amplitudes, frequencies and throw angles are chosen so that that the speeds & r defined by the formula (2) in claim 3 will· ?. Screening device with large throughput and large. Sieve surface for carrying out the method according to one of the preceding claims, characterized in that the length of the sieve surface is divided into several sections (1 to 10), the inclination of which is from; about 35 ° at the entrance decreases to 0 ° and increases again by a few degrees in the last sections, and that the sections _{perform different, mutually independent f,} preferably straight, oscillating movements, 009887/1291 -j * whose 6chv / in {Tunp "3ways from the entrance to the extensions, see below, decrease from about 25 mm to 6 mm, whose frequency can increase from about 65O to 1400 t / min and whose throwing angle can increase from about 25 ° to 70. 009 887/129 1 BAD ORIÖtNAL