DD144151A5 - PROCESS FOR PRESSING SALTS ON ROLL PRESSES - Google Patents

Description

Process for pressing salts on roller presses

Field of application of the invention

The invention relates to a method for pressing salts on roll presses with synchronously driven rolls whose surface is profiled, in particular corrugated or waffled, in which the salt is fed by means of snow core conveyors into the nip.

Various fertilizer salts, especially potash salts, are produced during manufacture as relatively fine-grained goods, which in this form are not suitable for mechanical spreading. These fertilizer salts are therefore usually on roller presses ver. presses, forming a scoop, which is then comminuted by grinding) to granules with grain sizes, for example. --Between 1 and ¹ mm. Even with rock salts is fine-grained salt, pressed in a similar manner and granulated.

Characteristics of the known technical solu tions. _{; :} .

When pressing the salts by means of rollers profiled on their surface, a good entrainment of the salt and thus a good roll filling is achieved. Such roll presses' have been analog roll presses with smooth rolls

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operated. Slugs were produced whose thicknesses are on the order of 8 to 10 mm maximum. An increase in throughput was previously sought by increasing the peripheral speed of the rollers. The increase in the peripheral speed, however, limits are set by the fact that above certain peripheral speeds no adequate squeezing of the scarf is possible. In the known method, a ratio of useful grain to undersize is further achieved, which is smaller than 1: 3. Thus, it is worked with considerable cycle quantities and associated with a high energy consumption.

A quality criterion for fertilizer salt granules is the so-called abrasion resistance, i. the amount of salt that is rubbed off the granules when shaking the granules with steel balls within a given time. The lower the abraded amount of salt, the better the quality.

Object of the invention ·.: .. '.

The aim of the invention is to make the process more economical with simultaneous quality improvement.

Explanation of the essence of the invention

The object of the invention is to provide a method with which slugs of particularly high strength can be produced at high throughput, from which granules with high abrasion resistance can be produced.

This object is achieved according to the invention in that

a. the material to be pressed with a temperature greater than 120 ° C is abandoned,.

b. the pressing is carried out with a specific pressing force equal to or greater than 4.5 t / cm,

c. a circumferential speed of 0.55 to 0.75 m / sec is provided for the rolls,

d. the roll surface is at a temperature less than. 80 ° C is maintained.

With the method according to the invention, a granulate is obtained which has an abrasion resistance which is substantially higher than that of the invention. Abriebsfestigkeit of by known, process compressed salts. Abrasion strengths were improved on the order of 30-50 % .

Surprisingly, it was found that despite the relatively low peripheral speed high throughputs can be achieved ... ':: can, -... and that fact that the pupil thickness in the inventive method is very much increased. In the inventive method to be greater Schülpendicken '..) as Ik mm reach. The pupil thicknesses of 16 mm were achieved with the same abrasion resistance of the granules. When the pupil thickness is increased, the specific pressing force must be adjusted. The pupil thickness of 16 mm was achieved, for example, with potash salt with a specific pressing force of about 5.5 t / cm. With the method according to the invention, a substantial improvement in the cycle ratio of feed to slug was also achieved. For example, a ratio of spout to feed greater than $ 90 was achieved, ie, at least 90 % of the discontinued fine-grained material was compressed into a viable processing slug.

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The slug is crushed in an impact mill. In this case, the granules are sieved into three fractions. Granules with a certain particle size, for example 1 to 4 ram, are removed as useful grain. Granules with a particle size smaller than 1 mm - undersize - is fed back to the fine feed material for the press and pressed again. Granules with a particle size greater than H mm will be ground again.

In the method according to the invention, a ratio of undersize to useful grain of about 1: 1 was achieved. Thus, the circulation amount is reduced to about half of the total material trcjms. In known plain roll presses, the circulation amount is more than 300 % of Nutzkorns.-

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In addition, a reduction of the specific electrical power is achieved in comparison with methods with smooth-roller presses. With respect to the overall system, halving the specific electrical power, i. to be expended for a weight unit of grain useful electrical power.

Due to the relatively low peripheral speed in conjunction with the profiling of the roll surfaces and a particularly favorable ventilation of the goods is achieved, so that the production of a substantially uninterrupted slug is possible. \

Due to temperatures of the roll surface lower than 80 ° C, in particular in the range between 40 ° C and 70 ° C, melting of the salts are avoided on the press surface. The scab is given a bright surface. The achievable temperature of the roll surface depends essentially on the

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Temperature of sur available cooling water and the ambient temperature. The aim is to have the lowest possible temperature, which should preferably be in the range of 40-60 °. , ..-. , , .. '..'. 7. / '

Embodiment:. ·

!. Was used a roller press with horizontal juxtaposed Preßvrests.

1.1 roll diameter 1000 mm

1.2 Working width of the rolls 1250 mm '

1 "3 Surface waffled with cushion-like depressions". ^: '· -'- with ...''.''. .. Λ. ';.;'.'-"' ... 1.3 x 1 maximum depth of 5 mm

1.3.2 lateral offset of the waffle pan in successive rows of 50 % 1.3 · 3 Offset of the waffle troughs on the opposite

Rollers 50 % in the direction of the circumference.

% Λ Cooling of the rolls by means of coolant channels arranged below the roll surface

1.5 drive

1.5.1 installed drive power 630 KW

1.5.2 Speed of the rollers 12 rpm

corresponding to a peripheral speed of 0.6 m / sec 1 "5 '» 3 synchronous drive of the two rollers

1.6 Infeed by filling screws. - 5 "~ times ^

2. Feed Kalilösesalz

2.1 Grain Size 60 (60 Potash Salt). '.'.

2.2 Salt temperature 1 ^ 0 ° C

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3. Operation

3.1 mean pupil thickness 14 mm ^v .

3.2 specific pressing force 4.5 t / cm;

3.3 throughput.

3.3.1 gross 80 t / h

3.3.2 Sludge output 75 t / h

3.3.3 Granule application Grain size 1 -4 mm 45 t / h 3 · 3 · 4 Abrasion resistance high

- ..; 3.4 Power consumption of the press 425 KW

4. Increasing the average school thickness to 16 mm resulted in a proportional increase in power consumption. portion of increase in throughput data below 3.3 achieved

- - .... with the same granulate quality. ·

The process according to the invention is shown in the attached flow chart. The salt, for example a Kalilösesalz with a particle size of less than 0.2 to 0.3 mm, as indicated by the arrow 2, a bunker 4 is supplied, from which it is fed via a line 6 of a roller press, with two to horizontal Axes counter-rotating ') Preßwalzen is provided. The material is fed into the nip via screw conveyors, preferably via multiple screw conveyors, which are arranged side by side in the axial direction of the rollers. The rollers are profiled on their surface, in particular corrugated or gewaffe.it. · The rollers are cooled and the roller press is provided for this purpose with a cooling water inlet 10 and 12 Kühlwasseräblauf.

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The pressed in the roller press rag is fed via conveyor 14 to an impact mill 16. The comminuted material 18 is placed on a triple-wire 20, in which first the oversize with a grain size greater than Ά mm is sieved. This material is returned to the flow of material before the impact mill l6 and re-ground.

The good with the grain size 1 to 4 mm is the Nutzgut.

The screened peeling with a particle size of less than 1 mm is returned via conveying means 22 in the feed bunker 4.

The 'pressed in the roller press 8 Good contains a certain proportion of unpressed fine material. Good, which has a particle size of less than 1 mm, is screened off in a sieve 24 and returned with the conveyor 22 together with the sieved in "the screen 20 fines in the feed bin 4.

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Claims (3)

Claim for invention 1. A process for pressing salts on roll presses with synchronously driven rolls, the surface of which is profiled, in particular grooved or waffled, in which the salt is fed by means of screw conveyors into the nip, characterized j a. the material to be pressed is placed at a temperature greater than 120 ° C, b. the pressing is carried out with a specific pressing force equal to or greater than 4.5 t / cm, c. a circumferential speed of 0.55 to 0.75 m / sec is provided for the rolls, d. the roll surface is kept at a temperature less than 80 ° C. 2. The method according to item 1, characterized in that for the rollers, a peripheral speed of 0.6 - 0.7 m / sec \ is provided. 3. The method according to item 1, characterized in that the pressed material is abandoned at a temperature between 130 ° C and l60 ° C. , M, procedure after point. 1, characterized in that the orphan surface is maintained at a temperature between 40 ° C and 70 ° C, preferably between 40 ° C and 60 ° C, For this purpose "/ page drawing