FR3023187B1 - PROCESS AND DEVICE FOR DRYING AND MILLING WET MATERIALS - Google Patents

Abstract

The present invention relates to an installation intended for the drying and grinding of inert raw materials, of the type comprising: Drying means comprising an enclosure in which the material to be dried in bulk is introduced; • A source of hot gas pulsed at the entrance of the drying means; • A grinder of the air flow type; • Dust filtering means, at the exit of the mill; characterized in that it comprises a single hot air suction means located downstream of the mill and being common to the drying means and the mill. There are provided means for conveying the hot gas from the source, passing through the various means of drying, grinding and filtering to the single suction means downstream of the installation and arranged downstream of the means of filtering.

Description

PROCESS AND DEVICE FOR DRYING AND MILLING WET MATERIALS

The present invention relates to a method and a device for its implementation, intended to grind, that is to say reduce to a range of particle size, in the form of fine particles or dust, inert raw materials, and having a non-negligible water content, for example having a moisture content between 10% and 90%, and especially between 15% and 85%.

The process of the invention is applicable to any wet material, which is either powdery, plastic, powdery, fibrous, gelatinous, or pasty. Thus, the process of the invention finds application in several fields such as construction, communication routes, or food processing, or the environment, or chemistry, or cosmetics ...

For example, in the construction, the process makes it possible to treat clay, which, once ground, is intended for the ceramic industry. In the agri-food industry, the material may consist of algae, pasta, co-products from, for example, rendering or processing of seafood, dairy products, animal or vegetable protein, oilcake In the field of the environment, the material may consist of sewage sludge. In the field of chemistry, the material may be derived from a precipitation or granulation process. To this end, in known manner, grinders are used, for example, either with rollers, or with pendulum or with attrition. either impact or sprayers, usually grinders type aeraulic.

The high quantities and volumes to be treated and the resistance of the materials to be crushed (rocks and pebbles) therefore require large and resistant installations that consume energy. In addition, the final particle size must be within a narrow range. Finally, grinding generates dust by definition, which should be avoided from the installation.

It is understood that the grinding of such materials raises implementation difficulties. To these difficulties are added others when the raw material is wet, such as clay. The difficulty increases further if the material, in addition to its moisture content, has a fibrous structure, gelatinous, or is high viscosity.

Indeed, before grinding, it is necessary to dry the wet raw material, that is to say to reduce its water content.

To do this, in known manner, two successive installations are used, a first drying, followed by a second for grinding.

A known drying installation comprises an enclosure into which are introduced on the one hand the material to be dried in bulk, and on the other hand a stream of gas (usually air) hot. Known drying systems are diverse and include, among others, so-called fast dryers, spray towers, drying tunnels, rotary dryers.

In the example of the treatment of clay, the moisture content at the start is generally between 10% and 50%. At the outlet of the drying chamber, the dried material is recovered with a reduced moisture content, typically between 0.1% and 20%. The drying chamber is preferably cylindrical and rotary. It is further connected, via a filter, a ventilation means that sucks the hot air loaded with dust, and recovers the latter to add to semi dry material coming directly from the enclosure.

Then, the dried material (at the exit of the dryer) is then directed to a second separate grinding plant, which comprises, in known manner, a "dynamic separator" provided with a known mill (of the roller or pendulum type) and at the base of which is blown a hot gas (usually air). The outlet of the mill is connected to a vacuum means, via a filter that separates the hot air loaded with moisture and dust, to recover the dried milled material. Optionally, the mill base is connected to an additional source of hot pulsed gas to complete the drying.

This known method, based on two separate and successive installations, has disadvantages.

The final material must not only be ground to a given grain size, but must also have a moisture content within a given range, and in particular less than an imposed maximum. This last parameter is crucial for the ceramic industry.

However, the known drying and crushing plants, which operate in series, each have their own operating parameters: gas temperature, gas flow rate, material flow rate to be treated, pressure losses, dust rate.

This has several disadvantageous consequences: - The management of the parameters is made complicated, which increases the uncertainty on the granulometry on the one hand and the moisture content on the other hand. - These double installations are cumbersome. - Installation, maintenance and consumption costs are high.

The present invention overcomes these drawbacks and proposes a method and an installation which makes it possible to obtain in a sure manner the desired grain size and the desired moisture content, which have a reduced overall dimension, which consumes less energy, and this compared with to the two known successive installations. To this end, according to the invention, the plant intended for drying and grinding of inert raw materials, wet, of the type comprising: Drying means comprising an enclosure in which is introduced the material to be dried in bulk; • A source of hot gas pulsed at the entrance of the drying means; • A grinder of the air flow type; • Dust filtering means, at the exit of the mill; is characterized in that it comprises a single means of suction of the hot air (loaded with moisture and possibly dust according to the material) downstream of the mill, said suction means being common to the drying means and to the mill.

Thus, the installation of the invention has the advantage, compared to the prior art, of being simpler and therefore less expensive to construct (only one suction means and consequently only one filtering means) and in operation (energy saving).

In an application given by way of illustration, the material being wet clay, the invention is advantageous in that: • The cooking defects due to the presence of carbonate and / or shells in the clay, are eliminated; • The amount of additives is reduced; • The raw material is more homogeneous; this results in reduced porosity of finished products, such as tiles and bricks, which increases their resistance to frost and weathering. • As the particle size is thinner, the aesthetic and superficial appearance of the finished products is improved. • The life of baking molds usually made of plaster is increased, in some cases doubled. • Some clay quarries considered to be of poor quality, or difficult to handle, can continue to be exploited, whereas with known installations, they are no longer profitable or expensive to operate, or do not allow to manufacture products finished with the required qualities.

According to one characteristic, the installation comprises means for conveying hot gas from the source, passing through the various drying, grinding and filtering means to the single suction means downstream of the installation and arranged downstream of the filtering means.

The term "one or only suction means" means a suction means which is only able to suck up and extract all the gas flowing in the installation from upstream to downstream, and arranged downstream of the installation. However, this suction means located downstream of the installation may include one or more suction elements of the fan type.

In addition, the dust filtering means of the mill are arranged downstream of the mill, and said single suction means is arranged downstream of the filtering means.

In order to complete the drying of high humidity materials, the installation further comprises an auxiliary source of hot gas connected to the inlet of the mill.

The hot gas is preferably air, and can come either from an additional source provided for this purpose, or from a source different from another device and thus recovering the hot air from a process completely independent of the drying / grinding plant of the invention. The drying chamber is for example of the type: fast dryer, spray tower, drying tunnel, rotary dryer.

The air mill is for example of the roller type or the pendular type.

Preferably, there are provided dust collector means, for example of the cyclone type, and in particular two successive cyclones, at the outlet of the drying chamber, and the outlet of said dust collector means being connected to the inlet of the mill. The installation optionally comprises means for feeding and mixing the crushed dried material from the mill with additive materials, such as, for example, sand, wood, pigment, barium or any combination thereof. The invention also relates to a process for manufacturing a dried and ground material, of suitable particle size and having a pre-established moisture content, comprising successively at least one step of drying a material by introducing a hot gas , a step of grinding the dried material, and a step of filtering the dried and ground material to provide the appropriate particle size, characterized in that it comprises a single step of suction and exhaust gas which is carried out only after the filtering step.

According to a characteristic of the process, the hot gas circulates in a single circuit from the drying step, through the milling and filtering steps, to be sucked and extracted after the filtering step.

Advantageously, the grinding step comprises the introduction of a stream of additional hot gas, this additional gas mixing with the gas from the drying step, all of the gases being sucked after the filtering step. The invention will be better understood in the light of the following description of illustrative but nonlimiting examples, with reference

Figure 1 is a simplified flow chart showing the different steps of the method and installation.

Figure 2 is a simplified side diagram of the first part of the installation.

Figure 3 is a simplified side diagram of the second part of the installation.

FIG. 1 shows a schematic view in the form of a flowchart of the different steps of the method, and of the various stations of the installation according to the invention.

The functional block 1 represents the material or materials to be treated, that is to say, to dry and grind to obtain a material of a suitable particle size on the one hand, and having a desired moisture content on the other hand. The invention is described hereinafter in a specific example of a particular material, namely clay, which has a high viscosity, and a high water content (between 10 and 35% moisture). It is understood that the invention is not limited to this material and may include in particular all the wet materials mentioned above.

In the example described, the clay undergoes a prior treatment, known in itself, and consisting of: extraction and removal of the metal bodies, by magnetic means; - shredding; - spraying or reducing to wet powder.

The material thus prepared in a coarsely mechanical manner, is conveyed to a drying station, referenced by the block 2. The drying means are connected to a means 3 for generating hot air (known in itself).

The material of the drying means is conveyed to grinding means 4, then downstream of the latter is provided a filtering means 6. The grinding means 4 are further connected to a second hot air generator 5.

According to the invention, the filtering means 6 from which the dried and ground material is extracted are connected to a single suction means 7.

The materials resulting from the filtering step 6 are conveyed (arrow 8) to a mixing station of the treated material, to additives, represented by the functional block 9. The various additives or added or complementary materials come from different reserves, symbolized by the functional block 10. The additives or complementary products and materials are arranged in storage means or reserves referenced 10A, 10B, 10C, 10D, 10E, and 10F (addition of liquid - water, solute, etc. - in the case clay.

The materials and their additives, once mixed, are subjected to a final treatment for their use, such as cooking for example in the case of clay, and represented by the functional block 11.

With reference to FIG. 2, the means of the invention are represented in detail, namely the drying means (block 2 of FIG. 1), the grinding means (blocks 4 and 5 of FIG. 1), and the filtering means (blocks 6 and 7 of FIG. 1).

The raw material or grossly worked mechanically (block 1 of Figure 1) is conveyed, via a conveyor 12, of known type, to a hopper 13 located vertically above the inlet 14A located in upper part of drying means 14, of known type, such as for example a fast dryer.

The drying means 14 also comprise a second feed inlet 14B located at the rear, and connected to a source of hot air 15 (block 3 of FIG. 1), of the type known per se and drawing ambient air. by an air intake 16.

Thus, in the drying means 14 penetrates on the one hand the product or the wet material, and on the other hand hot air.

To facilitate understanding, the path of hot air, and wet material have been symbolized by lines or curves traversing all the different devices, means and devices to achieve the final product.

The flow or path of hot air is symbolized by discontinuous lines, while the path of the material or wet material, semi-wet or dry, is represented by continuous lines or paths.

The drying means 14 comprise downstream two outlets from which are evacuated three families of materials and products: - A first outlet 14C, in the lower part, from which is evacuated (path 17) the semi-dry material having undergone drying suitable and considered semi-dry or dry; - A second outlet 14D, in the upper part, from which are evacuated o On the one hand a mixture of air and dust of semi-dry or dry materials, represented by the path 18; o On the other hand, the hot air having circulated in the drying means whose evacuation route is referenced 19.

The dry or semi-dry material 17 is conveyed by a conveyor 20, known in itself and arranged substantially horizontally. The upstream end 20A of the conveyor 20 is located vertically below the lower outlet 14C of the drying means 14, while the downstream end 20B of the conveyor 20 is located vertically above a lifting device 23 provided with a noria of buckets or the like attached to an endless chain. This makes it possible to route the dry or semi-dry material upwards on a second horizontal conveyor 24. The dust-laden air 18 of the material and the hot gas 19 (coming from the drying means 14) are conveyed to the inlet. means of the cyclonic type dust collectors, consisting in this case of two successive cyclones 25 and 26.

The two cyclones 25 and 26 respectively have a discharge outlet 25A and 26A, each equipped with a rotary airlock 25B and 26B, from which the larger solid particles emerge from the dust of the semi-dry material or dry while the finest particles are retained in the corresponding cyclone. About 95 to 97% of the dust is thus recovered via cyclones 25 and 26. The material particles from the cyclones are represented by the paths 18A and 18B respectively. The hot air 19 coming from the drying means 14, which contains fine particles of material, with a low content (a few%), enters the two successive cyclones 25 and 26 and emerges at the outlet of the second cyclone 26 along a path 19A. This hot air still contains a little dust (about 2 to 5%).

The material particles 18A and 18B from the two cyclones form dry matter which is poured on the first horizontal conveyor 20, to join the material 17 directly from the outlet of the drying means 14.

On the second horizontal conveyor 24 following the elevator 20, the dry material reaches the downstream end 24B of said conveyor, to be conveyed via a rotary lock 27, at the base of a mill 28 (block 4 of the 1), of the type known per se and of the air flow type. As a preferred example, such a mill may consist of the known mill type pendulum referenced PM. At the base and at the inlet of the mill 28 is also introduced the hot air stream 19A from the cyclones 25 and 26.

To the hot air stream 19A penetrating the base of the mill 28, is added a second stream of hot air 29 from a second hot air generator 30 (block 5 of Figure 1), collecting the ambient air 31 to heat it according to known techniques.

The second hot air generator 30 at the base of the mill is optional.

Thus, in the mill 28, and the base of the latter, penetrates a mixture on the one hand dry or semi-dry material from the previous drying step, and on the other hand a double stream of hot air (19A) from cyclones 25 and 26 and the second hot air generator 30 (stream 29).

The mill 28 delivers, at its upper outlet 28A, via a dynamic classifier known under the trade name DYNAIR, a mixture of dry milled material, in the form of dust, and hot air, along respective paths 31 and 32, which penetrate filtering means or filter 33 (block 6 of FIG. 1) known in itself and of the type for example an automatic compressed-air pulse bag filter known under the trade name INTENSIV FILTER or FB FILTRATION or DELTA NEU.

The filtering means 33 receive a mixture from the mill, containing hot air charged with moisture and dry material, this mixture is filtered to separate the moist air from the material.

Thus, at the base 33A of the filter, via a rotary airlock 33B, the dry product extracted is conveyed under the reference 8 to the means for adding and mixing additives and complementary materials, represented by the block 9 of Figure 1 (and which is not visible in Figure 2).

Moreover, at the upper outlet 33C of the filter 33, the hot, damp, dust-free gas is discharged via a path 34 which opens out according to the invention onto the single suction means 7 (FIG. 1). The latter consists of a vacuum fan 35, of the type known per se, and the output of which is connected to a vent stack conduit 36, to either the atmosphere or to means for recovering the calories that remain in the original hot air stream.

It is noted that from upstream to downstream of the installation, the hot air thus follows a circuit through the various means / successive stations of the plant for manufacturing the dried and milled material at the particle size and at the humidity rate. hoc, this hot air from the first hot air generating means (3, 15) located upstream of the drying means 2 (Figures 1 and 2) to be sucked and extracted only by the single fan 35 (means d suction 7) downstream of the filter 33.

In other words, the hot air has a continuous path in a single circuit, from the hot air generation means 15 located upstream of the installation, to the exhaust 36, connected to the single fan / vacuum cleaner 35, and this through all the means and devices described above, namely the drying means, the dust collector cyclones, the grinder, and the filter.

According to one of the features of the invention, the suction means 7, and the vacuum fan 35, is thus unique for the entire installation.

With reference to FIG. 3, the dry material treated, by drying, grinding and filtering, and referenced 8 is conveyed to a third horizontal conveyor 37, at the base of which, in the upper part, are arranged containers or reserve means of additional materials, additives, additional or other and represented by the functional block 10 (Figure 1).

The containers 10A to 10E are five in the example shown, it being understood that the number and content of these containers are based on the needs, and the material to be treated.

In the example shown, the container 10A contains sand, the container 10B of the wood, the container 10C of the white clay, the container 10D of the pigments, and the container 10E of the barium carbonate, and the water inlet 10F.

These different products or additive materials are arranged on the third conveyor 37 sequentially, within the flow and the delivery of the dry and treated material, to lead to the downstream end 37A of said conveyor 37, in a mixer 38, which may consist of a single, two or more successive mixers, of the type known per se or in themselves, on a fourth horizontal conveyor 39. The latter conveys the final processed product, that is to say dried, crushed, filtered, and with the additives, and therefore a dry product directly usable, referenced 40, to so-called processing means of use, such as for example cooking, in the case of a material of origin under clay form. In this particular example of clay material, the utilization treatment means are also supplied with cooking waste (chamotte resulting from bricks or broken or non-compliant tiles) from a source G, via an additional horizontal conveyor 41 .

The manufacturing process takes into account the various operating parameters of the installation, including: - the flow of hot gas (in this case air); - the temperature of the hot gas; the flow rate of the raw material to be treated, arriving at the drying means; the speed of rotation and displacement of the material and the material in the drying means; - the number of dust collectors; the dimensions of the dust collector cyclone (s); - the dimensions and capacities of the air mill; - operating parameters of the mill, such as speed of rotation, torque ... etc. ; the power and the flow of the single suction means 7 downstream. - Gas volumes, - The pressure and pressure loss parameters of the gas in the ventilation system.

Claims (8)

1. Installation intended for drying and grinding of inert materials, raw, wet, of the type comprising: • Drying means (2); • A grinding machine of the air flow type (28); • Dust filtering means (6) at the outlet of the mill; characterized in that the drying means: - are distinct from the mill; - are arranged downstream of the mill; - comprise an enclosure (14) into which is introduced the material to be dried in bulk; in that it comprises, on the one hand, a source of hot gas (15) pulsed at the inlet of the drying means and, on the other hand, a single means of the suction of the hot air (7) charged with moisture and possibly dust depending on the material, downstream of the mill, said suction means being common to the drying means and the mill, and in that it comprises means for conveying the hot gas from the source passing through the various drying means (2), grinding (4, 5) and filtering (6) to the single suction means (7) downstream of the installation and arranged downstream of the filtering means . 2. Installation according to claim 1, characterized in that the dust filtering means (6) of the mill are arranged downstream of the mill (28), and said single suction means (7) is disposed downstream of the milling means. filter (6). 3. Installation according to one of claims 1 or 2, characterized in that it further comprises an auxiliary source of hot gas (30) connected to the input of the mill. 4. Installation according to one of claims 1 to 3, characterized in that the hot gas is preferably air, and either from an additional source provided for this purpose, or from a separate source of a Another device thus making it possible to recover the hot air resulting from a process completely independent of the drying / grinding plant of the invention. 5. Installation according to one of claims 1 to 4, characterized in that the drying chamber (14) is of the so-called fast dryer type, or an atomization tower, or a drying tunnel, or a rotary dryer, and in that the air mill (28) is of the roller type or the pendular type. 6. Installation according to one of claims 1 to 5, characterized in that there is provided cyclone-type dust collector means (25, 26), at the outlet of the drying chamber (14D), and the output of said dust collector means being connected to the inlet of the mill (28). 7. Installation according to one of claims 1 to 6, characterized in that it comprises means for supplying and mixing the crushed dried material (8) from the mill (28) with additive materials (10), such as as for example, sand, wood, pigment, barium, liquid or any combination thereof. 8. A method of manufacturing a dried and ground material, of suitable particle size and having a preset moisture content, comprising successively at least one step of drying a material by introducing a hot gas, a step of grinding the dried material, and a step of filtering the dried and ground material to provide the appropriate particle size, characterized in that it comprises a single gas suction and exhaust step which is performed only after the filtering step, and in that the hot gas circulates in a single circuit from the drying step, through the grinding and filtering steps, to be sucked and extracted only after the filtering step.