DE102013012873A1 - Process for the preparation of fine-grained to lumpy starting materials by means of binder-free agglomeration - Google Patents

Abstract

The invention relates to a method for processing fine-grained to lumpy starting materials by means of binder-free agglomeration, in particular lignite with a moisture content in a range of essentially 40 to 60% by mass, the starting material being adjusted to a predetermined grain size range. According to the invention, agglomeration takes place by feeding the starting material into a horizontal mixing agglomerator, whereby the desired porosity can be achieved at the same time as the desired target diameter of the agglomerates.

Description

The invention relates to a process for the preparation of fine-grained to lumpy starting materials by means of binder-free agglomeration, in particular lignite with a moisture content in a range of substantially 40 to 60 wt .-%, wherein the starting material is adjusted to a predetermined particle size range, according to the preamble of Claim 1.

From the DE 10 2008 012 873 A1 a process for the treatment of lignite coal for high fineness is previously known. This process is intended to improve the drying and processing properties of lignite coal. In this regard, the internal solidified particle structure of the lignite coal is converted using its thixotropic properties in a pasty-flowable mass and comminuted into the macromolecular and colloidal area. For this purpose, screw presses, extruders or expanders are used. The hot pasty-flowable carbonaceous material is dry after exiting the above-mentioned pulping units by re-evaporation and obtained by agglomeration further refinement properties. After that, the coal is homogenized with a vortex mixer, in particular a so-called Eirich mixer to a secondary grain size of about 0 to 2 mm and then dried with tube drying to a water content of substantially 10%. The thus dried coal should have the property that during handling and dosing processes no dust is whirled up.

At the solution after DE 10 2008 012 873 A1 should coal components without thixotropic properties, such. B. more condensed humins and gelites and the xylitol fibers are embedded in the flow of material.

It is also known from the DE 196 35 829 A1 a method for the granulation of slaked lime with the aid of brown coal as a binding and embedding matrix. In this process, the slaked lime is intensively mixed with raw lignite coal, the lignite coal being initially comminuted to a high degree of fineness. The comminution of the raw lignite is carried out without predrying with the addition of water. The use of raw lignite should therefore be of process-determining importance, because the raw lignite can be transferred after suitable treatment and with the addition of water in an advantageous manner in a fine-grained granules with the desired grain size and narrow particle size range and the wet raw granules irreversible by drying to a solid material high porosity and high water resistance hardens.

The mixture of comminuted raw lignite coal with fine-grained slaked lime is subject to granulation, which can be realized by mixed agglomeration, pelleting, spray or fluidized bed granulation.

In the generic DE 43 37 494 A1 For example, in a process for producing low-rank coal binder-free pellets, starting from a feedstock into a pelletizer is considered. The coal having a moisture content of up to 60% undergoes compaction and stratification in the pelletizer. By turning the starting material in the pelletizing a smashing of coal components into fines and there is a so-called gel layer on the outside of the pellets, which leads to a Pelletwachstum. In order to form corn pellets and to maintain the gel layer in the growth phase, care must be taken that the moisture content of the carbon pellet is at such a high value that it at least fills the voids within the coal. Thus, the moisture content depends on the porosity of the coal. The aim in the process of pelletizing is to reduce the porosity and the associated minimal supply of water, so that ultimately there is a quasi-dry pelletizing process and the subsequent drying effort can be minimized.

In pelletizers based on a drum or disc type, the tumbling action provides the desired compaction but also grinding of the feed coal. Due to the quasi-coupled effect grinding / compaction, a process engineering optimization is problematic. Depending on the later intended use of the processed starting material, the surface obtained and the low porosity based on a pelletizing step are disadvantageous.

From the above, it is therefore an object of the invention to provide a further developed process for the preparation of fine-grained to lumpy starting materials by means of binder-free agglomeration, in particular lignite with a certain moisture content, which is suitable to obtain a product or intermediate, which as a result by agglomerating has a substantially spherical shape, wherein the surface of the agglomerates and their internal nature is not smooth and impermeable, but has structured and porous properties, so that as high as possible substance or heat exchange is possible for subsequent processing or processing steps.

The object of the invention is achieved by a method according to the teaching of claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

It is therefore assumed that a process for the preparation of fine-grained to lumpy starting materials by means of binder-free agglomeration, in particular starting materials based on lignite with a moisture content in a range of substantially 40 to 60 wt .-%, wherein initially the starting material to a predetermined Grain size range is set. The adjustment of the starting material to the desired predetermined particle size range can be done by means of per se known milling or crushing steps.

According to the invention, a Aufagglomerieren carried out by supplying the starting material in a horizontal mixing agglomerator, which in addition to the desired target diameter of the agglomerates and their shape simultaneously the desired high porosity can be realized.

The set to the predetermined grain size range starting material is moved by means of a rotating shaft of the mixing agglomerator, in the form of product-specifically designed blades through the fixed drum of the mixing agglomerator, wherein a crushing and a compacting process is performed by the blades by means of the blades. By way of the product-specific design, corresponding comminution units can first be designed for an optimum milling process and the blades for an optimized compaction process, which represents a significant advantage over known pelletizing devices.

In particular, in the output side region of the drum of the mixed agglomerator can by heating the drum, the z. B. can be designed double-walled, a drying or drying of the agglomerates are made.

The setting of the starting material to the predetermined grain size range can, as already mentioned, be carried out by means of a grinding process, in particular by means of a hammer mill.

In the horizontal mixing agglomerator, the agglomerating takes place until agglomerates with a diameter of about 0.5 mm to 5 mm, preferably 0.5 mm to 3 mm, are obtained, wherein at least one strength-increasing drying or complete drying to a final moisture content in the mixing agglomerator itself Essentially 15% by mass is made.

The residence time of the starting material in the mixing agglomerator can be controlled by adjusting the speed of the mixer shaft, the length of the drum and / or by the position of an externally adjustable discharge weir.

Within the mixing agglomerator, product cooling can also be carried out after the product drying mentioned.

In one embodiment, the mixed agglomerator and therefore the material present there can be supplied with preheated water and / or water vapor in order to optimize the process of agglomeration.

In comparison to the so-called intensive mixing or pelletizing plates of pelletizing devices, when using a horizontal mixing agglomerator, the residence time of the starting material can be influenced and thus controlled in a wide range. In the case of the pelletizing plate, the strength of the agglomerates is formed solely by rolling in the plate. In the case of ring-layer or flash-shear mixers, the mechanical stress on the green agglomerates which are being formed is very high, so that they are largely destroyed again or there is considerable abrasion. Even with an agglomeration in the fluidized bed, the resulting mechanical stress is very high, so that a large proportion of breakage and abrasion arises, which is not the case with the teaching according to the invention.

The invention will be explained below with reference to an embodiment and with the aid of figures.

The 1 shows here a basic flow chart of the method according to the invention.

The 2 illustrates a simplified system diagram for an apparatus for carrying out the method according to the invention.

In the process according to the invention, the starting material used is fine-grained to lumpy sedimentary rock, preferably brown coal having a moisture content of up to 60% by mass.

The agglomerates are prepared without binder addition and have an approximate spherical shape. The surface and the internal nature of the spherical agglomerates are not smooth and impermeable and compact, but structured and porous, so that the highest possible mass and heat exchange for subsequent process steps is given.

The starting material used ranges in grain size from powdery and fine-grained components to pieces of 50 mm in size and beyond. These may be fertilizers and soil additives, salts, but also other substances. Preferably, however, pit-wet crude lignite is treated with a moisture content of preferably 40 to 60 wt .-%.

According to the invention, the principle of horizontal agglomeration by means of horizontal mixing agglomerator is selected for agglomeration.

Via a mixer shaft of the mixed agglomerator, on which blades with product-specific shapes are mounted, the material is conveyed through the device.

In order to prepare components which are too large for agglomeration, in particular components of greater than 1 mm, for processing, either a separate grinding takes place or modified milling units are particularly advantageously integrated in the mixing agglomerator itself, preferably at the apparatus inlet.

Via a lance it is possible, if necessary, to add preheated water by spraying or by steaming in as an auxiliary agent. Preferably, at the exit of the apparatus, further modified comminution units can be integrated, which have the task of uniforming the agglomerates formed and of contributing to the narrowest possible grain band.

In the horizontal mixing agglomerator, the equalization of the starting product in its grain as well as its homogeneity and additionally the material transport are ensured by the aforementioned functions.

The movement of the blades within the mixing agglomerator results in a milling of the material combined with its compaction, resulting in the formation of initial agglomerates and agglomerate growth by addition.

This build-up agglomeration, which consists of the formation of layers and their solidification and at the same time provides the desired porosity, preferably produces moist agglomerates with a diameter of up to 5 mm, preferably from 0.5 mm to 3 mm. The moisture content of the agglomerates is about 40% by mass to 60% by mass.

The agglomerate properties are influenced by the design and speed of the crushing units and their location in the mixing agglomerator and by the number of crushing units and their distance from each other.

The residence time of the starting material or of the material to be treated in the mixing agglomerator can be influenced in a targeted manner both by the speed of the mixer shaft and by the structural design such as length, weir height or diameter.

In the same mixing agglomerator, after agglomeration in a separate zone at least one drying of the agglomerates can be carried out, whereby their strength is increased and improve the properties for onward transport.

In this constructive design, especially the length of the mixed agglomerator, a complete drying to a final water content of about 15 wt .-% can be performed. In a further, subsequent zone, it is possible to additionally perform product cooling, which improves the shelf life of the agglomerates.

If no or only incomplete drying takes place in the mixed agglomerator, the agglomerates, in a subsequent drying process, obtain the desired strength, which can be further processed in a next process stage, which, for. B. allows extraction.

This drying can consist of a pure contact dryer, a belt dryer or even a vibrating fluidized bed dryer. The drying is preferably carried out by means of a fluidized bed dryer, namely via a version by means of a vibrating fluidized bed. In a moderately fluidized bed, intensive heat exchange is given with high product protection. The vibration gently transports the product through the dryer. The drying medium used can preferably be superheated steam or air, mixed with superheated steam. This has the advantage that with explosive substances, such as lignite, the oxygen limit concentration can be kept below the value critical for a hazard.

An exemplary process flow will now be based on the schema 1 explained.

The relevant example deals with the material use of lignite by extracting the wax constituents from it by means of later extraction. To improve the conditions for the extraction and, consequently, to increase the wax yields, a Agglomeration of brown coal with subsequent or integrated drying.

In the example shown 1 is roughly pre-shredded lignite with a grain size of 50/0 mm and a moisture content of 40 to a maximum of 60% by mass on a conveyor belt 1 given.

About this conveyor belt 1 the starting material enters a mill 2 , in which a preparation to a grain size <1 mm takes place.

By means of a rotary valve 3 The ground coal is discharged and by gravity the actual Mischagglomerator 4 fed.

In mixed agglomerator 4 For example, agglomerates preferably of the mainly desired grain band of 0.5 mm to 3 mm are produced.

Circumferential tools at the entrance of the agglomerator act as additional comminution units.

These rotating tools on Agglomeratoreintritt serve for targeted final processing of the supplied coal, while similarly designed means before the product outlet of the Mischagglomerators produce a uniform grain size as possible.

The agglomerator can be heated to promote agglomeration. For agglomeration as auxiliaries water from a preferably heated storage tank 5 sprayed or steam are injected via a separate supply line.

The produced green agglomerates have 50 to 60 wt .-% water and are of low strength, which is important for further transport. Therefore, the transport must be carried out as gently as possible in order to prevent increased abrasion or breakage of the agglomerates.

In this regard, get away from the mixing agglomerator 4 the green agglomerates on a conveyor belt 6 which consists of a dosing belt or for the product-careful treatment of a vibrating trough.

The agglomerates will now be the vibrating fluid bed dryer 7 added. This is heated with drying air, which superheated steam was added. The absorption of the product moisture is done by this drying medium from drying air and steam, which is passed through the wet agglomerates. This has the advantage that in the case of an explosive substance, such as lignite, the oxygen limit concentration is kept below a relevant value for a hazard.

The product temperature does not exceed 100 ° C in order to avoid damage to the wax quality. The target final moisture content of the product is approx. 15% by mass. Drying gives the agglomerates sufficient strength for further processing in the mentioned extraction.

About the conveyor belt 8th , which in turn can consist of a dosing, the agglomerates from the dryer to the sieve 9 transported. There, the agglomerates are separated into the fractions desired grain band, oversize and undersize.

Overskorn and Unterkorn enter the containers 10 respectively. 11 from which they are supplied for other use or recirculation while the desired grain band in the container 12 is given. From there it gets to further processing, for example, an extraction of the wax components contained in the coal.

Instead of an intermediate storage in the container 12 The agglomerates can also be fed directly to the extraction. In this regard, the agglomerates retain their temperature, which has an energetic effect on the extraction result.

In order to avoid or reduce the problems of the low strength of the green agglomerates, it is particularly advantageous to carry out a drying or drying of the agglomerates already in the outlet-side region of the drum of the mixed agglomerator.

The 2 represents a simplified system scheme for implementing the teaching of the method according to the invention.

Coarsely pre-shredded lignite with a grain size of 50 mm / 0 mm and a maximum moisture content of 50 to 60% by mass is first fed to a metal separator F301 in order to remove any metallic components that may or may not be present.

After separation of the metallic constituents, the coal passes through a dosing belt H301 into a hammer mill Z301, in which it is treated.

The ground coal is discharged by means of a rotary feeder X301 and fed by gravity to the horizontal mixing agglomerator M301, which may have a heated drum.

In this horizontal mixing agglomerator M301 agglomerates are preferably produced of the desired grain band of 0.5 mm to 3 mm.

In this case, special (not shown) rotating tools act at the entrance of the apparatus as additional crushing means.

For improved agglomeration, heating can take place via the jacket of the agglomerator M301. Also can be added as auxiliary water from the heated storage tank B301 or in a separate feed steam.

It was confirmed by experiments that an optimization of the agglomerate formation in the mixed agglomerator is possible, in that in the same apparatus after the agglomeration in a separate zone a drying or drying of the agglomerates takes place. This eliminates the problem of the low strength of the green agglomerates. In another subsequent zone, product cooling can be carried out. Both of the aforementioned process stages can be interconnected in the mixing agglomerator quasi.

In one embodiment, the green agglomerates pass from the M301 agglomerate to the H302 conveyor belt. This band may consist of a vibrating trough for gentle handling.

The agglomerates are then transferred via a feed lock X302 to a vibrating fluid bed dryer T301. On the one hand, the vibrating fluidized bed ensures a very good heat transfer from the drying medium to the product, which, on the other hand, is subject to a very gentle treatment.

The dryer is equipped on both sides by the feeder lock X302 as well as by a discharge lock X303 for the unpressurised infeed and outfeed of the agglomerates.

The agglomerates are dried with superheated steam. This drying medium is circulated and reheated indirectly in a heat exchanger by secondary steam.

Taking into account the recorded product moisture is by the steam drying, the oxygen concentration in the drying medium to a non-critical with respect to the risk of explosion value of z. B. lowered below 12%. A further reduction is possible.

In continuous operation, this results in a permanent inerting by the resulting in coal drying vapors. The drying medium is fed to a scrubber F302 for cleaning. By means of a fan V301, it can then be transported in a closed process to the already described heat exchanger for heating. Excess moisture from the drying is removed. By means of a bypass line of the dryer superheated steam can be added to the outgoing, with vapors from the drying acted drying medium to maintain a required minimum temperature.

The dust separated in the scrubber F302 is discharged with the wastewater, collected and transferred to a landfill or fed to a separate use. If suitable, the product separated in the scrubber can also be returned to the process itself.

Startup and shutdown processes of the drying plant are carried out by means of inerting by nitrogen.

The oxygen concentration in the drying medium is determined before the dryer and readjusted if necessary via a steam addition. Furthermore, the temperature is measured before the dryer. The differential pressure across the fluidized bed and its temperature are determined in the dryer and the dryer pressure is controlled. In the outgoing stream of the drying medium, the temperature is measured and regulated by the steam supply of the heat exchanger. Furthermore, a moisture determination is carried out in this stream to complete the mass balance of the dryer. After the dryer, a temperature determination is made in the product stream. Here it is desirable not to exceed a temperature of 100 ° C in order to avoid damage to the wax quality. By means of the dosing belt H303 the agglomerates are transported from the dryer to the double deck screen F303.

In the double-decker screen F303, the agglomerates are separated and the fractions desired grain band, oversize and undersize are obtained. Oversize and undersize get into the containers B304 and B302. The desired grain band is placed in container B303 for further transport to an extraction stage.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008012873 A1 [0002, 0003]
• DE 19635829 A1 [0004]
• DE 4337494 A1 [0006]

Claims (10)

Process for the preparation of fine-grained to lumpy starting materials by means of binder-free agglomeration, in particular of lignite having a moisture content in a range of substantially 40 to 60% by weight, the starting material being adjusted to a predetermined particle size range, characterized in that agglomeration by means of feeding the starting material is carried out in a horizontal mixing agglomerator, whereby in addition to the desired target diameter of the agglomerates the desired porosity can be realized simultaneously. A method according to claim 1, characterized in that the starting material is fixed by means attached to a rotating shaft of the mixing agglomerator, in the form product-specific blades through a fixed drum of the mixing agglomerator, wherein on the blades, a grinding and compacting process is performed. A method according to claim 2, characterized in that takes place in particular in the output-side region of the drum by heating them on or drying of the agglomerates. Method according to one of the preceding claims, characterized in that the adjustment of the starting material to the predetermined grain size range by means of a grinding process, in particular by means of a hammer mill. Method according to one of the preceding claims, characterized in that in the horizontal mixing agglomerator the Aufagglomerieren until the receipt of agglomerates having a diameter of 0.5 mm to 5 mm, preferably 0.5 mm to 3 mm, wherein in the mixing agglomerator itself at least one strength increasing Drying or complete drying to a final moisture content of substantially 15 wt .-% is made. Method according to one of the preceding claims, characterized in that the dwell time of the starting material in the mixing agglomerator by adjusting the speed of the mixer shaft, the type and arrangement of the blades, the length, the weir height and / or by means of position of an externally adjustable discharge weir is controllable. Method according to one of the preceding claims, characterized in that within the mixing agglomerator product drying is carried out after product drying. Method according to one of the preceding claims, characterized in that the mixed agglomerator and thus the treated material preheated water and / or water vapor can be fed. A method according to claim 8, characterized in that distributed over the length of the Mischagglomerators several agglomeration zones are created to allow a Aufbauagglomeration. A method according to claim 9, characterized in that by the use of the horizontal mixing agglomerator and created working zones on the one hand over the residence time of the treated materials as well as spatially the steps of crushing, agglomeration, Nachzerkleinerns or Vergleichmäßigs, and / or drying and optionally cooling can be realized.

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