DE1767563A1 - Method and device for the production of granulated slag fertilizer - Google Patents

Description

DR.-ING. BY KREISLER DR.-ING. SCHÖNWALD «/ 67563 DR.-ING. TH. MEYER DR. FUES

COLOGNE 1, DEICHMANNHAUS

Cologne, 20 _o 5o1968 Ke / Ax

Institut de Recherches de la Siderurgle Francaise,

185, Rue President Roosevelt, SAINT GERMAIN-en-LAYK (Seine-et-

Oise) (France).

Method and device for the production of granulated slag fertilizer

The invention relates to the production of granulated fertilizer from phosphate varnish, which is obtained in particular when phosphor pig iron is blown ₀

On an industrial scale, fertilizers are mostly in Palverform manufactured. As is well known, this has great !! a cloud of dust arises when spreading, which worsens the utilization and working conditions of the staff « Furthermore, the application can only be used to a relatively small extent Working widths are carried out so that a large number of passes is required »

Processes have already been studied by which the hachteilo should be eliminated «In particular, these are processes for the production of fertilizers in the form of granules. For example processes are known in which granulation of the type known in Müh L ^ π As is known, the general principle of this process consists in kneading the powdery slag with the addition of water, granulating the resulting dough-like mass and finally drying the granulate Processes of this type are also known in which the kneading is carried out with the addition of a binder, whereby the

109837/0506

BATH ORIGINAL

Hardening of the granulate during drying is favored «These processes are advantageous as they are an optimal one Yield is possible »After sifting, the fine grain that has not been agglomerated can be returned» It is also possible to return the oversized grain after it has been comminuted again. Unfortunately, creating the Systems for performing these procedures often cost research and large investments without In any case, the quality of the product is guaranteed with absolute certainty »Furthermore, it has been shown that the equipment frequently used in these plants, especially the expensive and extensive rotary kiln for the drying of the granulate, as well as the classifying systems are not suitable, the problem in more economical and simple Way to solve. The experience that the applicant has acquired in the field of granulation enabled her to achieve a to find an advantageous solution to the problem of granulation of slag, which requires lower plant costs. The invention provides a method of making granulated fertilizers of good quality at low cost Production price available »

The invention accordingly relates to a process for the production of fertilizer granules from slag, in particular from slag that is obtained from the blowing of phosphorus pig iron, optionally after mixing the ground slag with other plant nutrients for Mixture gives a certain amount of water, the resulting dough-like mass in the presence of a binder to granules deformed, then the granulate dries and classified according to grain size and the proportions that are outside the desired Grain size range, returns. The process is characterized in that the finely ground Granulated slag in a granulating plant, the granulate obtained dries and hardens in a fluidized bed and it separates by air classification according to grain size.

1ÜÜ8J7 / 0506

BATH ORIGINAL

The method according to the invention can also have the following features in combination with the above features:

a) A mixing plant is used to add nutrients to the slag add in powder form

b) An air classification system is used to separate the G-ranulat to separate into two grain size fractions, the boundary between the two fractions preferably between 0.1 and 0.3 mm lies «

c) The granules *, the grain size of which is below this value, is discharged from the classifying system at the top and with With the help of air pressure, the above-mentioned mixing plant is fed back, while the granules with grain sizes above this value is deducted from below from the classification system o

d) The granulate, the grain size of which is above the stated value, is fed to a sieve, through which a separation between granules, the grain size of which is below a second value of preferably 1 to 3 mm, and the represents the end product, and a granulate with a grain size above this second value is made.

e) The granules, the grain size of which is greater than the said second Value is calibrated and added to the end product.

f) The granulate, the grain size of which is greater than the second value, is finely ground again and placed in the mixing plant returned.

g) The return to the mixing plant according to f) is done pneumatically »

h) The granules are dried at a temperature between 120 and 180 ^° C.

The invention also relates to a system for carrying out the method, which is characterized by a device for feeding the finely ground slag, a granulating system, in which water is added, the slag in a dough-like mass is transferred and agglomerated to granules,

109837/0506

BATH ORIGINAL

a fluidized bed drying plant in which the granules are dried and hardened and which has at least one sunk combustion chamber as the main component, and an air classifying device for separating the granules according to size and for cooling the granules ₀

The system according to the invention can also have the following features in combination with the features mentioned above:
n) The above-mentioned granulating device works with a turntable »

b) The water used to agglomerate the powdery product to form granules contains a binder in solution, which preferably consists of calcium chloride.

\ vj.e already mentioned, the invention enables the production of an end product in the form of a granulate, the grain size of which has an upper limit, oils preferably between 1 and 3 mm, for example 2 mm, and a lower limit, which is preferably between 0, 1 and 0.3 mm, Z ₀ B. at 0.2 mm. The air classification system enables the fine grain to be separated from the larger granulate, the cut being 0.2 mm, for example. The granulate with a grain size of less than 0.2 mm is separated from the end product, since its presence in the fertilizer would bring the above-mentioned disadvantage, ie the formation of a cloud of dust when spreading. This fine grain is preferably circulated in order to maintain the good granulation yield. The presence of oversized granules in the fertilizer would also have disadvantages. In particular, it would make an even distribution of the fertilizer on the ground impossible. For this reason, the granulate with a grain size over 0.2 mm, which accumulates at the lower part of the classifying system, is fed to the sieve, on top of which the separation between granulate with grain sizes below 2 ram, cLh, dimensions between 0.2 and 2 mm that the final

1 0 y f <j 7/0 b Ü 6

“AD ORIGINAL

product, and granules with grain sizes over 2 mm are made of the invention, for example, calibrated with a roll stand of known type and added to the end product will. The oversized grain can also be returned to the classifying system after calibration in order to separate the Sc: uib, which can arise during this calibration «According to oinem Another feature of the invention, which is explained in more detail in the example, it is also possible to use the granules with grain sizes over 2 mm, which is retained on the sieve, to grind again and the powder obtained in the mixer due to β

Ss is apparent that the invention in jeüym Pall represents the size setting of the granules, ea j DAT fertilizers, without loss of product and accordingly enabled with optimum yield

The plant of the invention has nußerdoai fu -, -. Miübnv most previously known plants for the production of fertilizer granules the great advantage that only .h> Minimum is used in mechanical parts, "Diaa i.-Jt may best guarantee for good? Operational safety and security; ity. This is possible in particular through the use of a fluidized bed dryer, in which Qm; Uo '. For the thermal energy and the Eneiv Le for the generation: 1er // Lrbelfich t one or more recessed, arranged combustion chambers are used, which are preferably similar to dv? V ^- Or b!>; j ι η un ^ ts chamber are formed, which are described in the franzÖBiaoiiuri Pateubaohelfΐ 1 420 512. the applicant irjf, _u ^; It has been found by the applicant that this burner, which has been etched in the course of studies on the preparation of iron, can be used in part for the granulation of fertilizers. This advantage also results from the combined use of a system in which the pneumatic classification and cooling of the granules coming from the drying system are carried out at the same time. In particular

10983 7'05UÖ

BAD ORiGINAL

is according to the invention the use of a method for pneumatic classification of a powdery product, advantageous / in French patent specification 1,477,593 procedure described by the applicant in this annex Another feature provided according to the invention are pneumatic devices for the return of the provided after sieving the crushed product at the exit of the classifying plant. These devices are from der Arimelderln preferred the known devices where, for example, augers or bucket elevators are used because they are more adaptable in operation and cheaper, in the conversation aind.

The invention is described in greater detail below with reference to a figure explained, which is an embodiment of the invention.

"DLe in the figure daryostollte plant v / eist a bunker au! ', The ground phosphate lacquer is carried out by a mill of the usual type, not shown. having a wiper system 4 of conventional design feeds "the slag is added to the enrichment potassium chloride contained in a hopper 5 Lat and also evenly on the main conveyor belt by means of a conveyor and weighing belt is stored, the mixture obtained on the main conveyor belt is in. lc-r plant 4 kneaded and homogenized. The proportions of the components of this mixture, which are known from the details of the weight camouflaging, which are supplied by the conveyor and weighing binders Ί and 6, are controlled by the Auagarigamen / jen of the bunkers 1 and 5 set.

The mixture from the mixing plant 4 arrives in a granulating device 7 known design, which mainly consists of a turntable 8, which is at constant speed rotates around an inclined axis 9, and the water through

I 0 0 8 3 7 / Ü b (J H

“AD ORIGINAL

a line 10 is supplied. Diesec contains water in Lös ¹ ng an existing calcium chloride "binder in an hienge of about 0.5 to 2 '/ o _f based on the Ge \ * / layer of the dry mix" The water passing from the mixer 4 to the granulating powdery Geni "cii is" moistened and converted into granulate in this way, the preferential price contains 8 to 14 / y volume, based on the weight of the dry equipment. When the grain reaches a certain size, it falls over an overflow a line 11, which is widened at the upper part and connected to a drying system: is o This consists in v / es ent borrowed from a container 12, at the bottom of which a combustion chamber is arranged, which has the task of the granulate dry and harden in a fluidized bed 13 2U. This device is described in the applicant's French patent specification 1 420 512. It includes a combustion chamber 14, which consists of a Blechzylindej · 15 substantially, which is also limited in its upper part by a substantially conical wall 16 of sheet metal * In the cylinder 15 located at the lower part a plurality of tangential openings, such as 17 in are shown. These openings open into the interior of a conically tapering part; 18 made of sheet metal, which expands in the upper part and is arranged coaxially with the cylinder. The chamber 14 is provided with a burner 19, to which heating oil is fed through a line 20 and similar atomizing air through a line 21 which surrounds the line 20. The lines 20 and 21 run inside a main line 22 through which preheated air is supplied. The line 22 opens into a ring 2? Which has four tangential outlets 24. The pre-obtained air arrives in this way in the chamber 14 with a circular motion and ignites the atomized fuel oil. The combustion gases formed flow through the tangential openings 17 into the tapering part 18 and escaped evenly into the container 12, where they pass through the Line 11 keep supplied product in the fluidized bed. The chalking movement favor

ϊ0983V / 0SU6

BAD ORIGINAk

- ο -

Stigt maximally the heat exchange by convection between the chamber and the fluidized bed, however, is not essential for the proper functioning of the device. For example, one could let the line 22 open directly upwards into the chamber fluidized product a very significant additional amount of heat by conduction through the top wall 16 of the chamber fed «, for this reason, by the way, this wall is designed to be conical, since in this way it has a larger surface having. At 25 a line is shown which is used to draw off the dust before the system is started up.

The temperature in the fluidized bed is preferably maintained between 120 and 180 ⁰ C, at about 150 ⁰ C. This temperature ensures rapid drying of the granulate and at the same time limits the amount of thermal energy used, which remains far below the amount required in a rotary kiln. This relatively low temperature also makes it possible to use sheets made of stainless steel for the walls of the combustion chamber and to dispense with parts made of refractory material, so that the system is cheaper. In this way, the water is suddenly driven out of the granulate, leaving pores inside the grain, which make it more soluble in the acids in the soil. The presence of a binder such as calcium chloride in the water introduced during granulation makes it possible to obtain granules with good mechanical strength due to the hardening effect during drying. A fairly high mechanical strength of the granulate is necessary in order to avoid that it disintegrates in the classifying plant or during bagging or transport. Another great advantage of this fluidized-bed drying system is that the drying takes place uniformly and with a high degree of efficiency, since each grain of the air or gas used for whirling up presents a maximum surface.

109837/0506

ORIGINAL

Of course, as with other known methods, it is without It is also possible to promote the hardening of the granulate even more by performing the drying in a gas atmosphere is, which has a higher COp content, whereby a stronger transfer of the lime contained in α er slag into the carbonate took place for this purpose an increase in the amount of heating oil supplied is sufficient.

The dry granulate received in the container 12 then passes through a line 26 to a classifying system which, as already mentioned, serves to sort the granulate according to size while cooling it at the same time. This system is designed in the same way as in that already French patent 1,477,593 mentioned by the applicant. It consists essentially of a fluidized bed container 21, at the bottom of which a grate is arranged, the distribution openings of which, as indicated in the figure, are oriented so that the transport of the product is facilitated. A fan 29 pushes air through a common line 30 into two wind boxes 30a and 30b, which are arranged at an angle to the grate and run in the same direction as the openings of the grate) whirled upwards, but with a lateral component to the larger grain to an exit opening 31 . From the figure it is easy to see that a fluidized bed of granulate is formed in the container 27, the fine red components of which are discharged through the upper outlet openings 32a and 32b into a common line 33, and the larger portions of which remain at the bottom of the fluidized bed move horizontally learn through which they are directed to exit 31 . The limit dimension between the coarse and fine fractions of the granulate, which was chosen by the applicant to be about 0.2 mm » but could be of any size, depends on the amount of air supplied through the line 30,

109837/0506

BATH ORIGINAL

The speed of the air at the exit of the wind boxes is adjusted with the help of the flaps 34a and 34b so that it is slightly higher in the wind box 30a than in the wind box 30b, whereby the separation of the granules is facilitated. It is obvious that this arrangement is not mandatory and that the number of wind boxes depends above all on the length of the fluidized bed tank "

Mm, the granules, which is greater than about 0.2, and is discharged through the outlet 31 at ambient temperature, then passes into a strainer 35. Here, a separation occurs in a granulate of a size below 2 mm, d "h _a between 0.2 and 2 mm, which represents the end product, which is collected in a container 36, and granules with a grain size of more than 2 mm, which are pulverized again in a mill 37 o

The product obtained at the exit of the mill is returned to the mixing system with the aid of a pneumatic conveyor system. Such a device is described in the applicant's French patent application PV 84 141 (November 18, 1966). It consists essentially of a closed container 38 with a round cross-section and a diameter that decreases from bottom to top. The powder entering this container through a conduit 39 is whirled up with the aid of air introduced into the lower part of the container through a conduit 40 provided with a slide 41. This air is blown into the upper chamber of the container 38 through nozzles 42 »An axial line 43 with a slide and a nozzle 45 at its end leads the transport air to the lower part of the chamber near the widened inlet 46 to another axial vertical line 47 is blown. The powder particles are drawn into the line 47 in this way and then returned to the mixing plant in the circuit. This device is simple and adaptable in operation. In particular, it allows, with the aid of the slide 44, the

109837/0506

BAO ORIGINAL

The amount of dust recirculated can be regulated as desired, "The conveying air is dedusted in a cyclone" 48 and escapes through a line 49 to the outside, while the powdery product is collected in a bunker 50 »This The bunker feeds the mixing plant 4 in the same way as the bunkers 1 and 5, but only what has already been mixed Product receives, its exit quantity is essentially equal to the sum of the exit quantities of the bunkers 1 and 5> and this discharge quantity is also regulated with the aid of a conveyor and weighing belt 51

The finer particles, especially those under 0.2 mm, which are discharged from the classifying system through line 33 are also returned to the bunker 50 via a further dedusting cyclone 52, while those for whirling up Serving air, which has carried these particles, is discharged through a line 53 into the open air. A first Partial removal of the dust also takes place from the fluidized bed drying plant. The top of the container 12 is connected to the cyclone 52 by a line 54 for this purpose. The water vapor produced during drying, the combustion gases of the burner and the fluidizing gas are in the same way through the Line 53 discharged *

The complete cycle of the particles, their grain size does not lie between the two desired values, in the present case 0.2 and 2 mm, guarantees one optimal yield without any loss of product. The system described thus enables a considerable reduction the manufacturing costs of the fertilizer in particular due to the simplicity of the devices used, which only one Have a minimum of mechanical parts, and due to the low energy consumption. Of course, this device can also can be used for the production of simple granulated fertilizers exclusively based on phosphate.

109837/0506

BAD ORlGlNAi-

The proportions mentioned in the description were given only as an example. "It would be straightforward possible, the proportions as well as the type and number of plant nutrients and the type of binder that Could just as easily consist of nitrates, silicates or organic products, which are suitable for the nature of this process suitable, as well as to change the grain sizes of the end product. The amount of granulated fertilizer that can be used with this device can be produced is practically unlimited.

Ü b H J 7/0 b U 6

Claims (1)

Claims ■ 1.) Process for the production of granulated fertilizer from preferably incurred when blowing phosphorus pig iron Phosphate slag, if necessary after mixing the ground slag with other plant nutrients Adding water, shaping the resulting paste in the presence of a binder, drying and classifying the resulting paste Granulate and recycling of the proportions lying outside the desired grain size range, characterized in that that the finely ground slag is shaped in a granulating plant and the granulate obtained is dried in a fluidized bed and hardens and separates by air classification according to grain size. 2.) The method according to claim 1, characterized in that the slag is powdered plant nutrients in a mixing plant admits. J5.) Method according to claim 1 or 2, characterized in that the granulate is divided into two grain size fractions in an air classification system, the limit of which is between 0.1 and 0.3 mm, separates. 4,) Method according to claim 1 to 3 *, characterized in that the fine-grained granulate is discharged from the classifying plant above and returned to the mixing plant, and the coarse-grained one Pulls off granules from the classifying system below. 5 _# ) Method according to claim 1 to 4, characterized in that the coarse-grained granulate is separated on a sieve into the end product with a grain size of less than 1 to 5 mm and a coarser granulate, which in turn is either lelibrated and added to the end product or else is finely ground again and returned to the mixing plant . 109837/0506 β.) Method according to claim 1 to 5 *, characterized in that the return to the mixing plant is operated pneumatically. 7.) Method according to claim 1 to 6, characterized in that 3 C and dries at 180 ° C. the granules at temperatures in the range between 120 ° 8.) Process according to Claim 1 to 7, characterized in that calcium chloride is used as the binder. 9.) Device for performing the method according to claim 1 to 8, characterized by means for feeding the fine ground slag, a granulating system with water supply, a fluidized bed drying system with at least one recessed combustion chamber and an air classification system. 10.) Device according to claim 9, characterized by a granulating system with rotating granulating disc. 109837/0506