DE2124880B2 - Process for processing rock phosphate - Google Patents

Description

The invention relates to a method for processing rock phosphate, in which the phosphate-containing minerals are crushed, refined, sieved and desludged.

Many phosphate-containing minerals show a strong accumulation of phosphorites in certain grain classes on. In some cases this accumulation is so great that it is possible to use simple classification Can extract concentrates with commercial contents from the ores. Generally these occur Accumulations of phosphates i.i raw ore in a grain range between about 1 and 0.06 mm, while the coarser and finer fraction; n so poor in P2O5 are that processing these fractions is not economically viable

In most cases, two cuts are sufficient for processing rock phosphate, namely a The upper one for separating the coarser gangue particles and a lower one for separating the fine clay and tone lime-rich fractions. The limits are not always precisely defined and therefore have to be set even for one and the same ore can be redefined over and over again.

However, there are also phosphate ores in which the range of phosphates fluctuates in the coarser range Grain size is so big. that one still has to introduce a so-called intermediate cut, be it for to pull a special PjOy-rich fraction out of the grain range, or to get the more finer » Repel mountain particles occurring in fractions.

With the wet processing of phosphate ores you have according to processing technology No. 3/1970 Crude ore is crushed and then the crushed raw ore by refining, desludging and wet sieving enriched. From processing technology No. 9/1970 there is also a dewatering of raw phosphate sludge known in a centrifuge. Furthermore, an enrichment of the takes place according to known methods Raw ore in a dry way, namely by crushing and then classifying.

The use of the wet process is, however, in terms of the coarse separating cut on one specified grain range. The wet sieve classification fails below a certain separating grain size. Because with regard to a flawless passage through the sieve surface must namely Knitted fabrics were chosen larger than it was for that Screening of the pure phosphorite ooids is necessary, so that in addition to the phosphate-containing minerals also considerable amounts of low-phosphate gaits in pass through the sieve. The wet classification available as an alternative with the help of In many cases, classifiers do not allow the minimum phosphate content usually required for the Set the finished concentrate. This is mainly due to it attributed to that coarser components of the gait

ίο are identical to the smaller phosphorite ooids in the liquid and therefore reduce the phosphate content of the phosphate ore concentrate despite sufficient digestion of the phosphate-containing minerals.
In the case of the known dry processing method for phosphate-containing minerals, the above-mentioned disadvantages in the sieve classification do not occur; However, with the dry processing method it is not possible to break down the raw ore as selectively as is possible with the wet processing method.The phosphate content of the finished product will therefore always be poorer in the dry processing method than in the wet processing method, or else the phosphate output will be with the same P ₂ O ₅ -gelaIt can be much lower. Furthermore, the selectivity in the dry classification in the finest range is worse than that in the wet classification. On the other hand, with the dry processing of phosphate ores, the raw ore must be dried before processing, while with the wet process, this must be done directly

jo crushed crude product can be used as such can.

The object of the invention now consists in the wet process and the dry process, which are known per se to combine with each other so that while avoiding the disadvantages outlined above An optimal processing effect is achieved with the least amount of energy. This is what makes this job solved that the concentrate is after a filter or centrifugal dewatering in a hot gas stream

4n dries and after separation of the hot gases in is sieved in several stages in a cyclone.

By means of these measures according to the invention, a concentrate can be obtained very advantageously which the use of a dry classification with optimal

4 ^r > learning classification effect enabled. The coarse grain fractions obtained during dry classification are mixed with the fine grain fractions in such a way that the finished product has the required minimum content of P2O3. By the procedure according to

V) according to the invention, every required separating cut in the classification can thus be achieved very advantageously and an optimal and particularly economical yield of phosphate-containing ores can be achieved.

The method according to the invention is illustrated in FIG

v- a flow diagram shown schematically in the drawing explained in more detail.

The phosphate-containing raw ore, crushed to a grain size of 0-600 mm, is placed on a sieve 1 and separated on this into two grain fractions. the

m> grain size coarser IO mm is discharged as overflow and fed to an impact crusher 2. The material, which is crushed down to 10 mm in this crusher, ends up on a Sieve 3, from which the gangue is discharged as sieve overflow, while the sieve passage in one of the sieve 3

μ downstream further impact crusher 4 after / crkleincrt will. This impact crusher 4 also has the sieve passage (less than 10 mm) of the sieve 1 / ur After / .reduced. The crushing of the

Goods in the impact chamber 4 are either dry or with the addition of water, depending on the nature of the goods. The use of pulp for the pulverization of the phosphate-containing raw ore has the advantage that essentially only the gangue and not the pear-containing ooids are pulverized by the impact mills, so that they can be separated more easily from the accompanying minerals. The material, which has been comminuted to a grain size of about 2 mm in the impact mill 4, is fed to a refining drum 5, in which, when fresh water is added, it forms a pulp which is intensively mixed by the movement of the drum. In order to achieve thorough mixing or purification of the material fed to the drum, the refining drum 5 is provided with built-in components such as lifting shovels, screw conveyors and the like. By setting the drum speed accordingly, the phosphate ore grains, in particular the phosphorite ooids, can be freed from adhering accompanying minerals. The refining drum discharge flows to a sieve 6 on which the phosphate ore concentrate is classified at 2.5 mm. To support the classification and to better distribute the task on the sieve surface, plenty of water is added with the help of showers or the like. The sieve overflow, which essentially contains mountains, is discharged to the outside, while the sieve passage flows to a further sieve 7, on which a reclassification takes place via Umm P2Os content is very low, can be rejected. The sieve passage of the sieve 7 is fed to a collecting container 8 and from there introduced as a preconcentrate with the aid of a pump 9 into a cyclone IO. In the cyclone 10, the preconcentrate is pre-desludged. The resulting sludge is discharged from the cyclone 10 upwards, while the cyclone discharge flows to an agitator 11 arranged directly below the cyclone. It is very useful here to provide the pump 9 with a controllable drive. In this way, the delivery rate to be fed to the cyclone 10 as well as the speed at which the material is fed into the cyclone and thus the separating cut between the grain discharged upward from the cyclone with the sludge and the preconcentrate discharged downward from the cyclone can be advantageous Influence. If the P2O5 content present in the sludge is insignificantly low, most of the sludge accumulating in the cyclone 10 can be rejected. Otherwise, the entire liquid discharged upwards from the cyclone 10 is returned to the collecting container 8 via the line YZ.

Further mixing takes place in the agitator 11 and cleaning of the individual phosphate ore particles from adhering accompanying minerals. The overflow of the Agitator 11 reaches a collecting container 13 from to which it is continuously fed to a second cyclone 14 with the aid of a pump. One occurs in cyclone 14 Wet classification or post-purification of the pre-concentrate, The fine fraction that arises here is carried out approximately 0.07 mm upwards and over a Line 15 is returned to the collecting container 8. while the Zykio-.unterlauf, its grain size about 0.07 to 0.5 mm, a centrifuge or thrust slinger 16 is output, in which a The pre-concentrate is dehydrated down to approx. 15% moisture

The de-lamelling or purification of the preconcentrate in the cyclones 10 and 14 connected in series with an agitator 11 in between can be carried out very advantageously with an optimal effect, since each ZykJon can be set to the most favorable cutting cut and thus incorrect output can be largely avoided. To intensify this wet aftertreatment of the preconcentrate, fresh water is fed into the line 17 leading from the agitator 11 into the collecting tank 13 via a line 18 the centrifuge 16 are fed to the collecting container 13. The correct setting of the slurry density for the last cyclone stage is not only important 16 for the recovery of a Vorkonzentrates with a specific phosphate content, but also for the follow si drainage in the pusher centrifuge Moreover arbei'en the cyclones of desludging, especially the cyclone 14, with a recirculation of the overflow through the lines 12 and 20, whereby not only losses of phosphate minerals Ίι \ sludge are avoided but also a considerable saving of water is achieved. Apart from these water or turbidity circuits, the collecting tanks 8 and 13 can also have float valves

Ji) len provided and with the feed pumps of the cyclones are interconnected in such a way that the volume flow of the task of the cyclones always remains constant. In this way, on the one hand, the cyclones can be very advantageously tailored to the desired separation

) ■> sections set and on the other hand those set once Separating cuts are retained.

In order to keep the fresh water consumption to a minimum during the process, a controllable addition of water takes place to the impact mill 4, the lauter drum 5 m.d the

4 "Sieves 6 and 7 through branch lines 21, 22, 23 and 24, which are connected to the fresh water line 18. Fresh water is also fed into the pusher centrifuge 16 through a line 25. The filtrate water produced in the centrifuge is circulated through a line 26 In addition, fresh water is only added in the last part of the wet treatment stage of the process according to the invention, and only in an amount that is necessary to remove any grains _{that are still adhering to the P 2} O _{5 -rich}

ίο To wash accompanying minerals freely.

The wet process can be done with the help of fresh water as well as with the help of sea water be performed. When using seawater, you must jitioch to set a limited chlorine concentration

v. if the concentrate is contained in the concentrate, it is subjected to a wash with sweet water, which is expediently coupled with the dewatering process in the pusher centrifuge 16. The drainage takes place in the pusher centrifuge 16

mi expediently two-stage, with the fresh fresh water encounters the already prewashed product with a lower chlorine content and the sequence of the second washing stage, ie is not saturated with chlorine. the post-purge / wipe the both f ivrocyclone stages is fed back. Ks can

■ "'but jo according to the nature and composition the phosphate-containing material to be processed several washing stages with several cyclones and Centrifuges are switched on to \ on a hangar

th to obtain largely freed pre-concentrate.

Following the pre-concentrate obtained in this way in the pusher centrifuge 16 according to the method of the invention, this concentrate is dried in a hot gas stream which flows from an oven 27 through a line 28 into a cyclone 29. The registered from the pusher centrifuge 16 into the hot gas line pre-concentrate is dried by the hot gases at about 800 ⁰ C in the air. The dried and separated from the gases in the cyclone 29 preconcentrate, which still has a temperature of about 9O ⁰ C, isolated on three series-connected sieves 30, 31 and 32 into individual particle classes. The sieve 30 is designed so that the sieve passage has a grain size of 0.3 to 0.07 mm. This passage through the sieve already represents a finished concentrate, as it essentially consists of the phosphorite ooids, whose

Film r. L * «». V 1. 1 «L. * * 1 ' 1Λ CClJ W t U X Γ * &

ι iiOSpiiStgCriS! t DCiSpJCiSACiSC JS, 5 70 DCtrsgt. The sieve overflow of the sieve 30 reaches the sieve 31, the mesh size of which is designed so that the sieve passage has a grain size of 0.4 to 0.3 mm. The sieve overflow of the sieve 31 reaches the sieve 32, on which a separation of the grain size larger than 0.5 mm takes place. The resulting sieve overflow is fed to a bunker 33, while the sieve passages of the sieves 30, 31 and 32 are collected in containers 34, 35 and 36. The collecting containers 33, 35 and 36 advantageously each have two material discharge openings. which are provided with dosing devices, one of which leads to a conveying device for the finished concentrate and the other of which leads to a conveying device for the mountains. In the area of the discharge point of the conveying device for the finished concentrate, the PjOs content of the concentrate is expediently continuously measured with the aid of an X-ray fluorescence device. If the P ₂ O ₅ content of the concentrate obtained in the first sieve 30 is above the required phosphate content, the fine grain fractions are gradually added to the coarser grain fractions in such a way that the finished concentrate discharged from the collecting container has the desired minimum P2O5 content of around 34 , 5%. The collecting containers 33, 34, 35 and 36 can for this purpose also advantageously be provided with appropriate metering devices or slides and can be remotely controlled as a function of an analysis device known per se, thereby ensuring a largely automatic mode of operation.

If in the drying process of the pre-concentrate according to the invention from the cyclone 29 after The gases discharged at the top contain dusts with a phosphate content of more than 30%, these gases become expediently given up to a dedusting device 37, in this the dusts from the hot gases deposited and directly via a line 38 to the finished concentrate located in the collecting container 34 mixed in. Furthermore, it can also be advantageous to equip the sieves 30, 31 and 32 with corresponding gas collection hoods to be provided and to be connected to a dedusting device. Doing this can be very beneficial air is sucked through the sieves and through the goods located on the sieves, whereby not only

Un ** dC

ΐΟΓΐαΰΓΠ Such £! Γ! £ so strong cooling of the classified finished concentrate is effected that the concentrate can be conveyed with any conveying means.

The method according to the invention can thus be adapted very advantageously to the respective circumstances and

2> for the production of phosphate ore concentrates Phosphate minerals of any composition and origin are used with optimal yield wereiip. Sufficient for processing, for example Two cuts of phosphate-containing minerals

jo does not work, so can according to the procedure of the Invention also several separating cuts in a simple manner by adding sieves and / or Cyclones are made. Since the limits of the separating cuts for the phosphate-containing

S3 minerals do not always have to be precisely defined often be redefined again and again for one and the same ore. If the fluctuation range of the If the coarser grains of phosphate-containing minerals are relatively large, it is advisable to use one So-called intermediate cut to introduce a medium grain size in order to obtain a fraction that is particularly rich in PjOs to cut out the concentrate band or to repel the mountains occurring in the finer fractions. The following number table can use the

ti ranges of fluctuation of the phosphate-containing ores in the individual grain classes can be taken.

Grain class mm

Ore 1 Wt%

P ₂ O.

Ore 2

Wt%

P ₂ O,

Ore 3 Wt%

P ₂ O ₅

Ore 4

Wt%

P ₂ O ₅

Ore 5 Wt%

+5.0
5.0-2.5
2.5 -1.2
1.2 -0.8
0.8 -0.6
0.6 -0.3
0.3-0.2
0.2 -0.1
0.1-0.07
0.07-0.06

-0.06
TOTAL..

0.06 April 33 0.30 36.67 2.75 38.01 2.48 37.80 3.11 37.15 8.52 37.84 10.41 36.94 53.54 38.45 6.86 38.16 0.97 34.09

11.00
100.00

29.16
August 37

1.3 17.89 8.76 5.05 20.45 9.56 32.30 100.00 17.01 7.0 7.0 26.96 17.0 20.56 100.0 15.20 1.67 9.78 2.1 22.26 5.10 3.32 21.46 8.8 30.73 17.28 3.42 25.86 3.3 29.43 3.53 27.84 3.9 22.24 5.66 30.27 2.1 31.81 30.62 2.5 23.88 4.99 25.54 2.2 32.54 31.75 2.2 15.0 23.74 6.85 21.92 5.7 34.69 32.09 29.8 30.13 19.39 19.62 9.9 37.05 35.32 6.8 34.22 13.73 25.24 42.4 37.20 9.01 36.35 36.01 28.52 04/28 9.8 35.70 9.28 35.60 31.45 2.75 21.53 14.49 1.60 16.46 21.2 30.15 17.23 1.75 11.42 10.64 100.0 27.62 100.00 22.70

1 sheet of drawings

Claims (3)

Claims; 1. Process for processing rock phosphate, in which the phosphate-containing minerals be crushed, refined, sieved and desludged, characterized in that the the resulting concentrate after filter or centrifugal dewatering in a hot gas stream dried and, after the hot gases have been separated off, sieved in several stages in a cyclone. 2. The method according to claim 1, characterized in that that the comminution of the phosphate-containing minerals takes place in impact mills 3. The method according to claim 1, characterized in that that the resulting liquid in the dewatering of the concentrate at least one the cyclone stage is recycled.