Gypsum drying and/or burning plant

FIELD: devices for gypsum dehydration and semihydrate gypsum production.

SUBSTANCE: method involves supplying hot gases to inlet of the first channel; delivering gypsum to inlet of the second channel, which is concentric to the first one; moving gypsum in the second channel by supply screw; providing indirect heat-exchange between gypsum and hot gases; burning gypsum to obtain semihydrate gypsum. Gypsum movement and indirect heat-exchange stages include drying and partial burning gypsum to create semihydrate gypsum. Gypsum burning at the last stage is terminated in bringing gypsum into contact with hot gases. The last burning operation is of pulsed type. Gypsum movement and heat-exchanging stages continue for 30 sec-5 min. Gypsum burning by hot gases is carried out for 1-10 sec. Device for described method realization and ready product are also disclosed.

EFFECT: increased productivity and product quality.

27 cl, 2 dwg, 1 tbl

The present invention relates to an apparatus for roasting and in particular to an apparatus for firing two-water calcium sulphate (gypsum) in semi-aquatic calcium sulfate (plaster of Paris).

In the patent FR-A-2493826 described method of firing gypsum, in which the layer of gypsum is heated by direct introduction of hot gas and maintain at the temperature required to produce semi-aquatic calcium sulfate, while the water is dispersed inthe hot gases, while they are not in contact with the plaster.

In the patent EP-A-230793 described a method and apparatus for firing two-water calcium sulphate. According to the document gaseous combustion products are injected directly through the first pipeline, extending from top to bottom, a layer of product to be fired. Very hot gaseous products of combustion are cooled before you bring them into contact with the calcining material layer. For this less hot recycled gases, gypsum or both enter into the second pipeline, partially surrounding the first pipe that leads to the absorption of heat of hot gases by conduction through the wall of the first pipeline. Plaster comes in contact with the material layer before re-entering the contact with the hot gases.

This device has several disadvantages. Gypsum is introduced between the two pipelines, tends to Deposit on t is unaproved and linger blocking thus the device for firing. This problem is especially acute when the calcined material is a synthetic gypsum, for example, desulphogypsum.

Device for firing, described in the patent EP-A-0284464, contains the first pipe for introducing hot air into the calcining material layer. First mentioned pipe is surrounded by the second pipeline. Primary material intended for firing, passes through the intermediate space between the first and second pipelines. Between the first and second pipelines in the way of primary material are partitions.

The described device has several disadvantages. This device implies the need for pre-drying of the gypsum prior to its introduction into the device for firing in order to avoid clogging. In addition, this device uses crushed natural gypsum, which should be cut at the outlet of the furnace; thus, this device is unsuitable for desulphogypsum and synthetic gypsum.

These devices are also common shortcomings. Dehydration of gypsum is insufficient and non-uniform. In addition, thermal efficiency of these devices is low. Increased pressure inside these devices requires, to the ome, security measures and additional materials such as an auxiliary compressor to increase the pressure of high costs of installation and repair. In addition, the time of calcination of gypsum in these devices is significant that reduces their productivity, as opposed to their size, and reactivity of the resulting hemihydrate.

In this regard, the object of the invention is to eliminateone or more of the above disadvantages of the known devices.

The task is solved in that the proposed drying/calcining gypsum, containing:

space firing;

the first channel having an input connected to a source of hot gases, and an outlet opening in space firing;

the second channel having an input connected to a source of gypsum, and the exit opening in the space of firing, while the second channel is concentric with respect to the first channel;

- feed screw located, at least partially, in the second channel, with the aforementioned screw moves the gypsum in space firing.

According to a variant implementation of the second channel surrounding the first channel on part of its length.

According to a variant implementation of the second channel surrounding the first channel in a substantial part of its length.

According to a variant implementation of the space firing ratio is esthet camera surrounding, at least partially, the first and second channels.

According to a variant implementation of the space firing coincides at least partially with the inner part of the second channel.

According to a variant implementation of the space firing distributed between the interior of the second channel and the chamber.

According to a variant implementation of the space firing coincides with the interior of the second channel.

According to a variant implementation of the first channel is arranged to rotate relative to the second channel, and drives the feed screw, with which it merged.

According to a variant implementation, the pitch varies along the length of the screw.

According to a variant implementation of the screw is equipped with a stirrer, located at the end of the screw.

According to a variant implementation of the feed screw is driven into rotation, at least two centering levers, combined with a stirrer.

According to a variant implementation of the stirrer is equipped with a baffle, located in front of the exit of the first channel.

According to a variant implementation of the stirrer has an axis located at its end.

According to a variant implementation of the stirrer when the rotation goes bearings, combined with the camera.

According to a variant implementation of the channels are vertical.

According to Varian is the implementation of the input of the second channel has a conical shape, appropriate, at least partially, the feed screw.

According to a variant implementation of the second channel has a shape and design that provides the possibility of grinding.

According to a variant implementation of the feed screw has a shape and structure that enables the grinding.

The subject of the invention is also a method for calcining gypsum, according to which:

(i) served hot gases at the inlet of the first channel;

(ii) serves the plaster to the input of the second channel, concentric with the first channel;

(iii) move the gypsum in the second channel by means of the feed screw;

(iv) provide indirect heat exchange between the plaster and the hot gases, and

(v) calcined gypsum in the plaster.

According to a variant implementation of the plaster is desultory and/or natural gypsum.

According to a variant implementation stage (iii) moving the gypsum and (iv) indirect heat exchange include the drying of the plaster.

According to a variant implementation stage (iii) moving the gypsum and (iv) indirect heat exchange include drying and at least partially sintering (v) gypsum alabaster.

According to a variant implementation of the firing (v) includes bringing the gypsum into contact with the hot gases in the kiln is firing pulse type.

According to a variant of implementation, the time interval between contactyou the receiving gypsum and its full firing is less than 10 C.

According to a variant implementation of the firing (v) includes bringing the gypsum into contact with hot gases, and the firing is carried out in a fluidized bed.

According to a variant implementation stage firing involves moving gypsum from the output of the second channel due to the entrainment of hot gases.

According to a variant implementation of the residence time of the plaster and/or plaster of Paris in the second channel is in the range from 30 seconds to 5 minutes.

According to a variant implementation stage indirect heat exchange between the plaster and the hot gases includes a stage firing.

According to a variant implementation stage (iii) moving the gypsum and (iv) indirect heat exchange include drying and at least partially sintering (v) gypsum alabaster, while firing (v) complete conversion of gypsum into contact with hot gases, and completing the firing is firing pulse type, with the duration of the stages (iii) and (iv) are in the interval from 30 seconds to 5 minutes, and the duration of firing by contact with hot gases is in the range from 1 to 10 seconds.

According to another variant of implementation, the duration of stages (iii) and (iv) is in the range from 1 to 2 minutes, while the duration of firing by contact with hot gases is in the range from 2 to 5 seconds.

According var is the ant implementation of the method according to the invention further comprises a stage (iiib) grinding gypsum during stage movement (iii).

According to a variant implementation of the method is carried out in the drying/firing according to the invention.

The subject invention is also alabaster, which can be obtained by the process according to the invention. Mentioned alabaster has, in addition, specific characteristics, which will be described below.

The invention is further explained in the description of variants of its implementation, given as an example with reference to the drawings in which:

figure 1 depicts the cross-section of the installation for drying and firing according to the first variant embodiment of the invention;

figure 2 is a schematic representation of an example of a screw used in the installation of figure 1.

The invention proposes to arrange the feed screw in the channel for supplying gypsum. This channel is concentric with respect to another channel, the clerk of the combustion chamber of the burner and the channel for supplying hot gases. Thus, the hot gas channel can be an internal or external channel; below will be described a variation in which the hot gas channel is an internal channel, but the invention is applicable with the necessary changes (mutatis mutandi),to the case in which the hot gas channel is an external channel.

Gaseous products of combustion heat the gypsum external channel is for in order to dry and, in some cases, partially or completely degidratiruth (i.e. burn).

Gaseous products of combustion are then in contact with the material to perform a full or partial firing.

Figure 1 represents a transverse section of the installation 1 for drying/firing according to the first method embodiment of the invention. This drying/firing has a camera 2A, designed to accommodate two-water calcium sulphate intended for firing (or to continue firing).

The burner 3 is located in the upper part of the reactor, the yield of the burner 3 is placed in the first channel 4 for the transport of hot gases. The first channel 4 opens approximately at the base of the camera 2A. The second channel 5 surrounds the first channel 4. The feed screw 6 is located between the two channels 4 and 5. This screw is driven by a motor 7, using a suitable transmission. The shape and size of this screw fits precisely and is designed to ensure a good flow of gypsum and high heat output. Two-water supply calcium sulphate 8 enters the space between channels 4 and 5. Thus, the drying/firing zapityvat using two-water source of calcium sulfate. Suitable equipment is provided to ensure the integrity of the camera outside.

the you can use the appropriate burner, for example, with more or less long flame, in particular, described in the prior art. The burner generates hot gases used simultaneously for drying gypsum (evaporation of moisture or free water contained in the gypsum) and for the conversion of the two-water calcium sulphate dried gypsum in water calcium sulfate or alabaster, i.e. for his firing.

Hot gases pass through the channel 4, located, preferably, in the reactor vertically. Channel 4 extends from the burner right up to the bottom of the camera. Hot gases passing through the channel, are, therefore, approximately the level of the bottom of the camera 2A. In order to burn two-water calcium sulfate, hot gases can be introduced in any convenient place on the reactor. You can also include the use of the channel is inclined relative to the vertical installation for drying/firing.

External channel 5 surrounds the inner channel 4, these channels preferably are located in the camera vertically. Mentioned external channel 5 and the feed screw 6 can direct the plaster from the entrance 8 accurately into the camera.

Gypsum passing through the channel 5, absorbs the heat of the gases passing through the channel 4. Teploobmennik between the internal gas channel 4 and plaster external channel 5 allow for evaporation of free moisture gypsum to its direct kontaktierung the gaseous combustion products. The concentric arrangement of the external channel 5 and the inner channel 4 allows efficient heat exchange between the plaster and the hot gases. The specified heat transfer based on phenomena such as convection, radiation and, particularly, thermal conductivity of.The feed screw is partly contributes to heat exchange, in particular, due to the fact that he is, preferably, welded to channel 4, thus forming its axis, and due to the size of the blades, providing a large surface of contact with the plaster.

Moisture is removed through the exhaust pipe 13, located, preferably, in the upper part of the chamber, and adapted the space between the upper part of the channel 5 at the base of the inlet 8 and the outlet 13. You can also supply pipe 13A (not shown)located at the level mentioned fit the space, with the specified pipe may, if desired, release the water vapor, or a part of water vapor, or, conversely, to serve for additional water vapor injection box (or any other gas, if necessary).

Mentioned Teploobmennik allow not only to dry the plaster, but, if necessary, to start the reaction conversion of two-water calcium sulphate semi-aquatic. Thus, the drying/firing has space firing 2 g the dog, who can even begin inside the outer channel 5 with subsequent continuation in the chamber 2A and, in certain cases, in the piping at the outlet of the reactor.

The feed screw 6 is located between channels 4 and 5. This screw is driven by a motor 7, preferably by channel 4, with which it is inextricably linked. The screw allows you to apply the plaster in the external channel 5. This screw extendsfrom the guiding entrance for gypsum 16 external channel 5 having a conical shape, the shape of which can accept a screw.The screw also allows you to avoid clogging of the channel 5 cast, or due Hobbies they plaster mass, or by scraping the blades of gypsum from the inner walls of the outer channel 5. Similarly, the screw homogenizing the primary material as a result of its mixing. The temperature difference between the primary material near the inner channel 4 and the primary material near the outer channel 5 is thus reduced, which further improves the evaporation of free moisture.This is advantageous when the material contains desulphogypsum, as this product is especially great amount of free moisture. The speed of rotation of the screw adjust depending on performance. The resulting water vapor disperses through the top of the system. Set the drying/firing according to the invention allows to prevent blockage of the plaster, in particular damp desulphogypsum, during operation. At the same time, it is preferable to provide a gap between the screw 6 and channel 5.

At the level of the inner end of channel 4 gaseous products of combustion come in contact with the material. In the above-mentioned Teploobmennik temperature gaseous combustion products decreases when they reach the end of the channel 4 and come into contact with the material. So you can burn (or end firing) material emerging from the outer channel 5 at the corresponding temperature of the gas, for example, in the range from 300 to 600°C. thus Avoid formation during roasting junk derivatives, such as anhydrite II.

The characteristic dimensions of the firing installation according to the invention are, for example, (a capacity of 5 t/h):

- the height of the reactor: 2500 mm;

- diameter of reactor: 2100 mm;

the diameter of the bottom of the outer pipe: 700 mm;

the diameter of the upper base of the outer tube: 1710 mm;

- diameter of inner tube: 500 mm

These dimensions are compatible with the transportation of Maritime container that facilitates the transport installation, in particular over long distances.

Under option installation for drying/firing can provide that channel 5 was surrounded by channel 4 on part of its length or in which its length.

The feed screw has, for example, the length comprising from 70 to 90% of the full height of the reactor. The screw has one or more blades extending radially in a spiral. In the example shown in the drawing, the screw has a single blade, the length of which corresponds exactly to the length of the inner channel 4. When channel 4 begins at a higher level (in particular, when the upper part of the channel serves as a combustion chamber), the screw length may be only part of the length of the above-mentioned channel 4 (for example, 80%). Preferably, the screw 6 has a length that exactly matches the length of the outer channel 5. Above the blade is made, preferably, of metal (e.g. stainless steel) or of a material having good thermal conductivity.

Preferably, the feed screw is combined with the internal channel 4 for gaseous products of combustion. You can, for example, to use channel 4 as the transmission shaft of the feed screw 6. The feed screw may also have a mixer/centering element 11. For example, the stirrer is fixed on the lower end of the channel 4, when the screw joint with him (but it could be combined with channel 5, or may be independent from both channels etc). This mixer/centering element plays the role of the centering element screw in the channel 5.

In this embodiment, the channel 4 smo is mounted in such a case, the rotating relative to the camera 2A. This option allows thus to receive the feed screw with a simplified manufacturing. Similarly, when the screw is improvedthermal conductivity between the hot gases and gypsum in the outer channel 5.

Figure 2 illustrates an example implementation of the conveying screw 6. Shaped profile, for example, cross-section 15, used for the transmission of torque from channel 4 to the mixer/centering element 11. She may have, in certain cases, multiple blades, mixing, if necessary, the layer may present, or buildup at the bottom of the reactor. The mixer allows, depending on the type of kiln used in the drying/firing, homogenize material layer and distribute the material, coming from channel 5, the layer or remove any precipitation, re-directing them to the stream of combustible gas. This mixer allows thus to facilitate the emptying of the reactor if necessary (represented by numeral 17 in figure 1).

You can also provide that the blade or blades at the exit of the channels had a step, which would be less than the input feed opening, as represented in the example illustrated in figure 2. Variable pitch allows you to easily get the effect of the tube on the end of the screw, while the hot gases cannot, therefore, again on the rise in the material within the channel 5.

You can also include a tapered screw exactly along its length, in this case, the pitch change is not required. You can also provide the screw with a constant pitch and even, if necessary, with increasing step.

Mixer/centering the11 may be a deflector 12 (represented in figure 1) to improve aerodynamics.This deflector is placed in front of the exit channel 4 for hot gases.

According to a variant implementation of the gases, in some cases, contaminated extracted through the exit 13, then re-use. They can also take place in a cyclone separator or filter 14, which separates the dust particles from the extracted gases. Similarly, you can provide for reuse of the gases extracted through the outlet 9. Residual gases are subsequently directed into the combustion chamber of the burner, thus increasing thermal efficiency of the installation for drying/firing.

Depending on the selected mode and type of burning particles of hemihydrate (plaster of Paris) can be collected in the lower part of the firing installation (in the case of discharge through the pipe 17), the gases coming through the pipe 13 or through the side exit 9 on the upper part of which is formed, in known cases, fluidized bed 10. The firing will be described in more detail below.

At all possible times is ICICI three ways of firing; when this firing is described in more detail below.

According to the first method the plaster completely burn through direct contact with the combustion gases, a simpledrying takes place at the level of indirect contact with hot gases at the level of the space between channels 4 and 5. Space calcining gypsum extends in this case from the output space, located between channels 4 and 5 and includes a camera 2A (in this case coincident with reactor).Preferably, the output of channel 5 is firing, called "pulse". You can also make a regular firing in layer, similar to that produced in the above-described prior art. Depending on the temperature of the gases at the outlet, the firing may, in certain cases, to end after the release of the camera 2A, in particular, in the channels to filter,until the temperature is sufficiently high. In certain cases can be fired, which is called post-firing (the interaction between hot and wet gases and product during cooling). Found that the shorter was the time of firing, the more reactive was obtained semi-aquatic calcium sulfate or alabaster. Practically, it was found that the reactivity of the resulting hemihydrate increased its rate of firing. the thus, the especially advantageous to carry out the firing immediately after drying, in the form of pulse firing.

According to the second method roasting partially carried out already in the channel 5, and the burning continues in the chamber 2A. The burning zone 2 comprises in this case a part of the space located between channels 4 and 5 and the camera 2A. As in the first method, the firing may, in certain cases, to end after the release of the camera 2A, and alsopulse firing is also preferred.

Typically, the calcination is carried out according to the second method. The degree of firing at the exit of the channel 5 is usually from 20 to 70%, preferably from 30 to 60%, mainly approximately 50%.

Mentioned second method are, for example, with the following timing values cyclesdisplacement: the displacement cycle or drying in the outer channel 5 is from 30 seconds to 5 minutes, preferably, from 1 to 2 minutes; the firing cycle of the contacting of the product and the gaseous products of combustion is from 1 to 10 seconds, preferably, from 2 to 5 seconds.

This method is implemented, for example, using the above installation for firing with the screw rotating at a speed in the range from 2 to 12 revolutions per minute, synthetic gypsum with a granularity of 50 microns, such as desultory and heat capacity from 1.5 to 2.0 MW.

According to the third method of functioning the Finance installation for drying/firing, space firing coincides with the space located between channels 4 and 5 (i.e. the inner part of the outer channel 5). In this case, the entire gypsum calcined prior to its exit from the outdoor channel 5. In this case, no camera 2A and she can be omitted.

The difference between the three methods is determined by theseveral factors associated with the installation, operating conditions (thermal capacity and performance) and the characteristics of the plaster.

When processing synthetic gypsum it has very fine granules (average diameter is several tens of micrometers). In General, there is a possibility of drying and partial dehydration in the space between the two pipes (the second method). The degree of dehydration varies depending on the consumption of gypsum and power burners. At the exit of the channel end of the firing is carried out, preferably, pulse for a few seconds (for example, from 2 to 10 seconds). Then the product is entrapped in the flow of gaseous combustion products to the filter, where it is removed.

In the case of treatment of the crushed natural gypsum it has a relatively fine grain size distribution (average diameter of up to several hundred micrometers). In General, this type of gypsum (natural), not with high humidity, can be dried at the level of the conveying screw. CTE is Yan firing at the exit of the screw is also variable. In the case of low degree of burning wind conditions will be selected (see below) in such a way as to form a fluidized bed 10, removing the alabaster through the upper exit 9. In the case of a high degree ofwind conditions will be selected (see below) in such a way as to form a fluidized bed 10 only at a very low altitude, removing alabaster through the bottom exit 9, which almost coincides with the outlet 17 for discharging. In this case, the pulse firing is missing, while the residence time of the product in the layer exceeds a few tens of seconds. The position of the output depends on the degree of roasting on the output of the screw.

In the case of natural gypsum can provide a highly effective method of implementation. According to this method of implementation of the installation according to the invention provides the function of crushing, crushed on the basis of natural gypsum (having a particle diameter of, typically, 3 mm). According to this method of implementation of the second channel and/or the feed screw has (have) the form and structure suitable for grinding. In fact, you can choose the abrasive surface and adjust the gaps between the parts so as to obtain conditions of abrasion, allowing in this way to grind the crushed natural gypsum to particles having a diameter of, for example, the range from 50 to 500 μm. In General, the installation function shredding provided after the drying function.

Conditions (wind, thermal, etc.), generated in the chamber 2A, are, in particular, a function of particle size and dried more or less digidratirovannogo plaster, leaving channel 5, and gas velocity (empty case)in the camera. Known nomograms to determine,under these temperature and degree of humidity, which mode of transportation will be the product.

Are two cases to consider. In the first case, the particles are fond of hot gases. Is the phenomenon of transfer solids gases. In this case, the alabaster emit after separation from gases, for example, in the cyclone separator 14 (you can use any other commonly used type of separator). In this case, you can regulate the heat output of the burner and the flow of hot gases obtained for the implementation of pulse firing for a short time. This option is preferred, in particular, to obtain alabaster, which will be used for the manufacture of alabaster plates. In the second case, particles settle and form in this case, the fluidized bed. In this case, alabaster can be extracted into the chamber 2A on a more or less high level through the output 9, which limit the circumstances may coincide with the outlet 17 for discharging.

In the case of pulse firing chamber 2A is mainly guiding the pipeline for the received hemihydrate. In this case, the camera may be of any suitable form, and not necessarily cylindrical, as in the case of installations for the roasting of the prior art. In the case of firing with a layer of material, the camera 2A performs its normal function.

The method according to the invention provides several advantages over the prior art. This is a continuous and very stable process (quality alabaster is a constant). thermal and aerodynamic equilibrium is established very quickly (usually in less than 15 minutes)that simplifies the management process. Finally, the installation for implementing the method according to the invention is compact and simple, allowing you to reduce costs.

According to the invention can be obtained (in particular, with the firing method using pulse firing) alabaster, with the following properties.

Mentioned alabaster is particularly well suited for the manufacture of alabaster plates, alabaster tiles, alabastro called industrial coatings.

Alabaster according to the invention has very specific characteristics in comparison with stuccos, known from the prior art. The aforementioned features and advantages of the CI alabaster below:

(i) increased the reactivity with a very high speed setting;

(ii) low water demand;

(iii) the high turnover.

The speed setting is measured by various methods.

According to the first variant start setting on Gilmore is in the range from 4.5 to 6 minutes For this measurement used the ASTM C266.

According to the second variant finish setting Vicutu is in the range from 10 to 12 minutes For this measurement used the ASTM C472.

Under the third option, which is preferred, the beginning of the seizure of the knife less than 6 minutes, preferably less than 5 minutes. For definitions apply standard NF B 12-401 or ISO DIN 3050 (Ring Schmidt: inner diameter 60 mm, height 50 mm). When measuring, determine when the beginning of the stiffening fast alabaster, modify the process in accordance with the regulations for fast alabastro as follows: after spraying alabaster in the water in 15 seconds, and pause for 30 s for swelling powder, stirred for 30 s before filling ring Schmidt and raise the ring Schmidt after 1 min 15 sec for measurement setting of the knife.

The demand for water is connected, in particular, knead shares at saturation. It is more than 140 pieces of alabaster in 100 parts of water. For definitions apply standard NF B 12401 or ISO DIN 3050. For comparison, the usual alabaster has got mixed fraction at saturation of about 125 parts of alabaster in 100 parts of water.

Fluidity is excellent (which is also linked to water demand). It is measured by spreading, knead fraction of 0.75, at least 205 mm, preferably at least 240 mm, These values are unexpectedly high enough, when alabaster received pulse firing. In fact, stuccos pulse firing according to the prior art are characterized by a very average flow rate, which forces the use of a large number of additives. Apply standard NF B 12-401 or ISO DIN 3050 (Ring Schmidt: inner diameter 60 mm, height 50 mm). After spraying alabaster in the water in 15 seconds, and pause for 30 s for swelling powder, stirred for 30 s before filling ring Schmidt and raise the ring Schmidt after 1 min 15 sec for measurement spreading.

Alabaster according to the invention does not crack in the water. The BET surface (standard NF X 11-621) alabaster according to the invention is usually more than 8 m²/, Such value does not match the usual characteristics of alabaster, which does not crack in the water (for example, aged alabaster typically has a BET surface less than 4 m²/g and does not crack in the water). Regarding the definition of cracking in water which you can refer to the publication "Eclatement des grains de platre au contact de l'eau", Jean-Claude Weiler, in Ciments, Betons, Platres, Chaux, No. 774, 5/88. The ability alabaster according to the invention to cracking, taking the definition given in the above-mentioned publication, usually less than 5%.

Features alabaster according to the invention allow to obtain interesting properties.

A little time setting allows you to avoid adding curing accelerator, such as gypsum (which may be a residual burnt plaster or added gypsum). Thus, alabaster according to the invention does not contain gypsum (usually the gypsum content is less than 0.4, even : 0.2% wt.).

Low demand for water (mixing fraction at saturation and flow) allows you to add less water in the manufacture of plaster mass of this consistency. This is an advantage, because when installing alabaster plates or tiles, for example, it is necessary to dry the excess water used in the mixing. Thus it is possible to reduce energy consumption. Low water requirement also allows one to obtain the final products (industrial stuccos or alabaster slabs) increased hardness and/or high mechanical strength.

Apply the method according to the invention provided with the parameters included in a well-defined intervals, stuccos with the following characteristically 4 represents the usual alabaster.

The present invention is not limited to the described and illustrated examples and methods of implementation, but implies the presence of numerous variants available to the specialist. In particular, was described by channel 5 for supplying fresh two-water calcium sulphate, surrounding channel 4 for supplying hot gases, however, in the scope of the invention can also provide that channel 4 for supplying hot gases surround channel 5 for supplying primary two-water calcium sulphate. The invention may also be applied to any powdered PR is the product, which must be dried and/or baked.

1. The firing method of gypsum, including the stage at which

(i) served hot gases at the inlet of the first channel;

(ii) serves the plaster to the input of the second channel, concentric with the first channel;

(iii) move the gypsum in the second channel by means of the feed screw;

(iv) provide indirect heat exchange between the plaster and the hot gases; and

(v) calcined gypsum in water-gypsum;

and stage (iii) moving the gypsum and (iv) indirect heat exchange include drying and partially roasting (v) of gypsum in water-gypsum, while firing (v) complete conversion of gypsum into contact with hot gases, and completing the firing is firing pulse type, with the duration of the stages (iii) and (iv) are in the range from 30 s to 5 min, and the duration of firing by contact with hot gases is in the range from 1 to 10 seconds

2. The method according to claim 1, characterized in that the duration of stages (iii) and (iv) is in the range from 1 to 2 min, with a duration of firing by contact with hot gases is in the range from 2 to 5 C.

3. The method according to claim 1, characterized in that the gypsum is desulphogypsum or natural gypsum, or their mixture.

4. The method according to claim 1, characterized in that the calcination of gypsum is carried out in pseudowire the th layer.

5. The method according to claim 1, characterized in that the stage of roasting involves moving gypsum from the output of the second channel due to the entrainment of hot gases.

6. The method according to claim 1, characterized in that it further comprises a stage (iiib) grinding gypsum during stage movement (iii).

7. Installation (1) for drying and calcination of gypsum according to any one of claims 1 to 6, containing

space (2) firing;

the first channel (4)having an input connected to a source (3) hot gas, and an outlet opening into the space (2) firing;

the second channel (5)having an input connected to a source (8) of gypsum, and the exit opening in the space of firing, while the second channel is concentric with respect to the first channel;

the feed screw (6)that is located, at least partially, in the second channel, with the aforementioned screw configured to move the gypsum in space firing.

8. Installation according to claim 7, characterized in that the second channel surrounding the first channel, and the length of the second channel is a part of the length of the first channel.

9. Installation according to claim 7, characterized in that the second channel surrounding the first channel, and the length of the second channel is equal to the length of the first channel.

10. Installation according to claim 7, characterized in that the space contains the firing chamber, surrounding, at least partially, the first and vtoro the channels.

11. Installation according to claim 10, characterized in that the space of firing distributed between the interior of the second channel and the chamber.

12. Installation according to claim 7, characterized in that the first channel is arranged to rotate relative to the second channel, and driving the feed screw, with which it merged.

13. Installation according to claim 7, characterized in that the pitch varies along the length of the screw.

14. Installation according to claim 7, characterized in that the screw is equipped with a stirrer, located at the end of the screw.

15. Installation according to 14, characterized in that the feed screw is driven into rotation, at least two centering levers, combined with a stirrer.

16. Installation according to 14, characterized in that the mixer is equipped with a baffle, located in front of the exit of the first channel.

17. Installation according to 14, characterized in that the mixer has an axis located at its end.

18. Installation according to 14, characterized in that the stirrer when the rotation goes bearings, combined with the camera.

19. Installation according to claim 7, characterized in that the first and second channels are vertical.

20. Installation according to claim 7, characterized in that the input of the second channel has a conical shape corresponding at least partially, the feed screw.

21. Installation according to claim 7, characterized in that the second channel has a shape and structure, is going to grind.

22. Installation according to claim 7, characterized in that the feed screw has a shape and design, suitable for grinding.

23. Semi-aquatic gypsum obtained by the method according to any one of claims 1 to 6, with the following characteristics:

(i) reactivity:

a) start grasping the knife less than 6 min, preferably less than 5 min; and/or

b) setting the Gilmore is in the range from 4.5 to 6 min; and/or

c) after setting Vicutu is in the range from 10 to 12 min; and

(ii) mixing fraction at saturation, at least 140 parts of water of gypsum per 100 parts of water; and

(iii) the turnover is determined by the magnitude of the spreading 205 more, more preferably 240 mm

24. Semi-aquatic plaster according to item 23, having the following characteristics:

(i) reactivity: the beginning of the seizure of the knife less than 5 min, and

(ii) mixing fraction at saturation, at least 140 parts of water of gypsum per 100 parts of water; and

(iii) the turnover is determined by the magnitude of the spreading greater than 240 mm

25. Semi-aquatic gypsum in item 23, the BET surface which is at least 8 m²/year

26. Semi-aquatic plaster according to item 23, which does not crack in the water.

27. Semi-aquatic plaster according to item 23, not containing gypsum and/or chlorinated additives.