CH701702B1 - Calcination of briquettes. - Google Patents

Abstract

In a process for calcining green briquettes (200.3), the green briquettes (200.3) are subjected to a heat treatment for calcination, the green briquettes (200.3) being mixed together with a coal (200.1) containing a proportion of volatile combustibles, and calcined in a shaft furnace (110). An energy required for the calcination is thereby at least partially obtained by a combustion of the fraction of volatile combustible constituents of the coal (200.1). This creates a particularly energy-efficient and cost-effective process for calcining green briquettes (200.3).

Description

Technical area

The invention relates to a method for calcining green briquettes, wherein the green briquettes are subjected to a heat treatment for calcination.

State of the art

When cracking of oil is formed in addition to volatile hydrocarbons (gases, gasoline, diesel, fuel oil, etc.), which are separated, and petroleum coke as a solid. The raw form is called green coke and can be further processed for refining by calcination at high temperatures. In this case, remaining oil components are burned, the remaining calcine consists of a high proportion of carbon. Basically, in calcination, the term "calcination" refers to the heating of a material inter alia with the aim of dewatering it, or of removing or decomposing volatile components. Calcined petroleum coke is u. a. used as electrode coke in the aluminum industry and for carburizing steel.

EP 0 409 014 B describes a process for the production of low-smoke fuel briquettes, in particular for the production of thermal heat, wherein a non-baking fine-grained carbon support, preferably petroleum coke, and a pitch-containing binder are mixed. This starting mixture is briquetted into preforms and from the preforms the fuel briquettes are formed by a solidifying heat treatment. The heat treatment takes place in the rotary kiln at about 500 to 530 ° C. The pitch-containing binder used is a binder mixture of pitch and baking coal.

CH 674 643 (Aimcor) describes a process for producing briquettes wherein quartz sand (0.005-0.2 mm grain size range), a carbon carrier and a bituminous binder are mixed and the mixture is formed into preforms from which by heat treatment calcined briquettes are formed. It works with free from baking coal preforms, which are introduced into a heated rotary kiln and heated to up to 500 ° C. The heat treatment takes place in a quartz sand immersion bed. Over time, a solid carbon envelope forms on the quartz sand of the quartz sand dip bed. This quartz sand can be used for the production of green briquettes. For heating the rotary kiln additionally the volatile components can be used.

DE 3 724 541 A describes a method for the production of briquettes for the production of silicon or of silicon carbide or of ferrosilicon in the electric downhole furnace, wherein quartz sand, a carbon support and a bituminous binder are mixed and the mixture is formed into preforms. From the preforms, the briquettes are formed by a heat treatment. The preforms are fed into a quartz sand immersion bed in a heated rotary kiln for heat treatment.

EP 0 568 984 B describes a process for the production of briquettes. The briquettes have a carbon content of coke and optionally an additive content and are briquetted to green briquettes using a bituminous binder. The Gün briquettes are heat treated in a rotary kiln with a grain bed filling.

The calcination of briquettes by means of a rotary kiln has proved to be unsatisfactory. The mechanical stability of the briquettes thus produced was too low, so that these are disintegrated during transport to granules.

Presentation of the invention

The object of the invention is to provide a method belonging to the aforementioned technical field, which allows an energy-efficient and cost-effective calcination of briquettes.

The solution of the problem is defined by the features of claim 1. According to the invention, the green briquettes are mixed together with a coal containing a volatile combustible constituent and calcined in a shaft furnace, wherein an energy required for the calcination is at least partially recovered by a combustion of the volatile combustible constituents of the coal ,

Under a shaft furnace furnace is understood, which has a geometric shape of a standing on its base hollow cylinder, preferably with a round, oval or rectangular base or a hollow cone, respectively, a hollow body, which has an opening for an entry of educts and above has an opening at the bottom for a discharge of intermediates and / or products. The educts move essentially in a vertical direction from the entry to the discharge. Typically, the height of the furnace body exceeds its length and width many times.

As has been shown, a shaft furnace in the present context, in particular with respect to a rotary kiln, in particular the following advantages: <tb> 1. <sep> Due to the slow throughput of coal through the shaft furnace, all coal particles can reach the same calcination temperature. This achieves high strength, optimum density and high abrasion resistance. <tb> 2. <sep> Coals with high levels of volatile combustibles of up to 50% can be calcined without any negative impact on coke quality. <tb> 3. <sep> There is no significant loss of coal during firing. <tb> 4. <sep> Depending on the proportion of volatile combustible constituents in the coal, the energy obtained from the combustion of the volatile combustible constituents may be sufficient to heat the shaft furnace and / or for further process steps. <tb> 5. <sep> The resulting heat can be partially recovered, for example, to reduce or eliminate a water content of the coal.

The volatile combustible constituents include, for example, volatile hydrocarbons, in particular having the empirical formula CXHY. These are, for example, components with a boiling point below 800 ° C. This can z. As hydrogen, methane, ethane, benzene, toluene, xylene and / or derivatives thereof.

The coal calcined during the process is referred to in particular as coke.

The term briquette in particular the result of briquetting, in which a raw material is crushed and pressed into a uniform shape, called. Brown coal briquettes are usually brick-shaped and are pressed without binder under high pressure. In hard coal briquettes, preferably egg briquettes weighing from 20 to 100 g, coal tar or coal tar pitch is often supplied as a binder.

The coal, especially a non-baking hard coal with a relatively high proportion of volatile constituents, in particular has a certain reactivity, so that the energy for operating the shaft furnace can be obtained at least partially from the combustion of the coal. It is also advantageous if the coal contains as few impurities as possible with regard to metallurgy. Preferably, coal with a low ash content and high porosity is used. This achieves a high reactivity of the briquettes. Further, the coal should not cook together when heated nor with green briquettes. Also, the coal should have a proportion of volatile combustible components, which is preferably high. With the combustion of a part, in particular by means of the complete combustion of this volatile portion of combustible constituents, the shaft furnace can be heated. Preferably, the coal does not have to be comminuted, as this reduces the porosity and thus the reactivity.

It is also conceivable to use renewable materials such as charcoal. However, this has the disadvantage that charcoal is expensive and has a high content of impurities and too low a strength.

A possible specification of usable coal is shown in the following table: <Tb> Properties <sep> <Tb> Water content <sep> 0-15% <tb> Volatile share <sep> 20-50% <Tb> ash <sep> 0-3% <Tb> Sulfur <sep> 0.0-1% <tb> Hardgrove Index <sep> 30-60 <tb> Free Threshold Index <sep> 1-3

In a particularly preferred embodiment, coal is used with the following specifications: <Tb> Properties <sep> <Tb> Water content <sep> 6-12% <tb> Volatile share <sep> 35-37% <Tb> ash <sep> 1.3-1.5% <Tb> Sulfur <sep> 0.4-0.5% <tb> Hardgrove Index <sep> 48-50 <tb> Free Threshold Index <sep> 1-2

Furthermore, the coal may also contain vanadium, nickel, sodium, calcium, silicon and iron as well as trace elements, in particular in the ppm range (part per million).

According to the invention, the following advantages can result: <br> 1. The method according to the invention makes it possible, in particular, to produce briquettes having a high mechanical strength. This allows the briquettes to be transported without breaking or breaking up into granules. The method according to the invention makes it possible, in particular, to produce briquettes which are particularly diffusible and / or can have a high porosity. This achieves a large surface area, with which the briquettes obtain a good reactivity properties. Furthermore, briquettes having a high thermal shock resistance can be produced by the process according to the invention. When introducing the briquettes in a metallurgical furnace at temperatures up to 2500 ° C, thereby a breakage or disintegration into granules can be prevented by the rapid change in temperature. <tb> 4. <sep> The briquettes produced by the process according to the invention may have particularly low impurities, in particular with regard to ash content and trace elements, such as, for example, Boron, Phosphorus, Aluminum, Arsenic, Indium, Antimony and others, which meet the high demands of the metallurgical industry. <tb> 5. <sep> Finally, it achieves a particularly efficient and, in particular, energy-efficient process since, at the same time as the calcination of the coal, it can be calcined with the volatiles of the coal and the green briquettes.

Preferably, the proportion of volatile combustible constituents of the coal is so high that the energy required for the calcination of the coal and the green briquettes can be completely removed from the combustion of the volatile combustible constituents of the coal. Thus, the process can be performed energetically self-supporting and heating costs can be saved. Further, if necessary, a heat surplus can be dissipated and used elsewhere.

Optionally, metallurgical coke can be admixed. This, however, at most in small portions, since the ash content of 4-10% is relatively high.

Preferably, the coal has an ash content of less than 10%, preferably less than 5%, in particular less than 1%. This achieves particularly stable briquettes with good burning properties.

The proportion of the combustible volatiles of the coal is preferably greater than 20%, more preferably greater than 30%, in particular between 30% and 40%. With the combustible volatile components of the shaft furnace is at least partially heated. Therefore, it is advantageous if the proportion of combustible volatiles is high.

The method can also be carried out with coal with a lower proportion of combustible volatile components, the shaft furnace must be heated by other devices stronger. This can be achieved, for example, with burners. The skilled person are also known to other possibilities. Of course, coal with a volatile combustible content of more than 40% can also be used. For this, however, the parameters of the system would have to be adjusted.

The coal preferably has an average particle size between 1 and 20 mm, preferably between 3 and 7 mm. This range was determined by a variety of experiments and proved to be optimal for the process. Thus, a good bulk density is achieved in the shaft furnace, whereby a high throughput can be achieved. The smaller the particle size, the denser the shaft furnace can be loaded. However, the grain size should not be too small, otherwise the grains can completely burn up or cake to lumps.

The coal (wet coal) is preferably dried prior to entry into the shaft furnace, in particular to reduce a proportion of water in the coal. This has the advantage that the combustion chamber of the shaft furnace can be relieved. Since water has a high specific heat capacity, entry of wet coal can cool the shaft furnace. In addition, there is a risk that the water in an extremely hot shaft furnace evaporate explosively and thus could cause damage. Furthermore, it prevents corrosion of water-sensitive materials, in particular the rusting of metals in the shaft furnace. Finally, it can be used to prevent steam emissions from the feeders and corrosion.

Alternatively, could also be largely anhydrous coal and used directly, but this is significantly more expensive, especially since the heat for drying the coal can be removed from the shaft furnace.

The drying of the wet coal is preferably carried out at a temperature of about 100 ° C, especially at below 150 ° C. This ensures that in particular the aqueous portion of the coal can be evaporated, in particular, since water has a boiling point of 100 ° C. The energy required for this purpose can be obtained by means of a heat exchanger, for example in the exhaust gases of the shaft furnace. Of course, the drying of the coal can also be done by means of separate heating means.

Alternatively, the coal could be dried with suitable storage (covered warehouse) even at lower temperatures. This would have the disadvantage that the drying would take more time. Furthermore, it would also be possible to add hygroscopic substances which, after drying, could be separated off again and processed. But this would be more expensive and expensive.

An energy for drying the coal is preferably removed via a heat exchanger from the shaft furnace. During calcination, a large amount of energy is generated by the combustion of the volatile combustible constituents of the coal. This energy can be partially removed by means of a heat exchanger and fed to a drying device for the coal. The energy required for this purpose is preferably taken from the exhaust gases of the shaft furnace. For this purpose, a heat exchanger can be arranged between the chimney and the shaft furnace, which can pass the heat of the exhaust gases to a heat transfer medium. The heat carrier (HTM, or high temperature medium) is typically pumped in the circulation.

The heat could also be dissipated directly from the interior of the shaft furnace, but this is difficult to implement in practice. This would be of particular interest if the heating of the shaft furnace takes place exclusively via the combustion of the volatile combustible constituents of the coal, as a result of which the temperature can be controlled only to a limited extent directly. By using coke with coal, the volatile content can be reduced, which in turn negatively affects the efficiency of the plant.

The coal can also be heated in addition to or exclusively by means of another energy source prior to entry into the shaft furnace. For example, burners can be used for this purpose. In this case, however, it must be prevented that the combustible volatile constituents are ignited in the drying device, since the temperature could rise too high and, moreover, the volatiles for the heating of the shaft furnace would no longer be available or only partially available.

A weight ratio between green briquettes and coal in a feed to the shaft furnace is preferably in the range between 2: 1 and 4: 1, in particular at about 3: 1. The coal must be able to release enough volatile combustible constituents to reach a sufficiently high temperature for the calcination of the green briquettes.

The above information on the weight ratios have been found to be particularly suitable with respect to different shaft furnaces, which does not mean that other weight ratios would not work for specific parameters (dimension of the shaft furnace, residence times of the coal, temperature, etc.).

The shaft furnace is preferably operated at a temperature between 700 ° C and 1400 ° C, in particular between 950 ° C and 1050 ° C, operated. These temperature ranges were determined by means of a variety of experiments as suitable for calcination. However, the temperature also depends on the nature of the green briquettes and the coal, in particular the pitch content of the green briquettes and the volatile content of the green briquettes and the coal. When using green briquettes and / or coal of other specifications, an optimal temperature of the shaft furnace can also be in another range.

The green briquettes preferably contain coke and in particular additionally have silicon dioxide and / or calcined petroleum coke and / or coal tar pitch. This achieves optimal consistency and optimum burning behavior of the briquettes.

The silica may be used in crystalline form, especially in the form of quartz, tridymite and / or cristobalite. Due to the large occurrence on earth but quartz is preferred. The silicon dioxide used preferably has the following composition (in each case in percent by weight): <Tb> Properties <sep> <Tb> silica <sep> 95-100.0% <tb> ferric oxide <sep> ≤ 0.02% <tb> alumina <sep> ≤ 0.15% <tb> Total grain size <sep> 0.1-5 mm1500-1700 kg / m <3> <tb> Bulk density (according to ISO DIS 10236) <sep>

Particular preference is given to using silicon dioxide with the following specification: <Tb> Properties <sep> <Tb> silica <sep> 99-99.8% <tb> ferric oxide <sep> ≤ 0.01% <tb> alumina <sep> ≤ 0.06% <tb> Total grain size <sep> 0.1-3 mm1550-1650 kg / m <3> <tb> Bulk density (according to ISO DIS 10236) <sep>

The silicon dioxide to be used may also have other purity, but preferably a purity higher than 95%, in particular higher than 99%. The nature of the contaminants, especially if not contaminated with metals, is not essential to the production of green briquettes.

Calcined petroleum coke is a by-product of petroleum refinery and is sold as a standard product. Preference is given to using calcined petroleum coke with low impurities. The petroleum coke is prepared in particular by boiling the residual fraction of crude oil at 500 ° C and then calcining in a rotary kiln at 1200-1400 ° C.

Coal tar, for example, occurs in the production of metallurgical coke. From coal tar, coal tar pitch can be produced by distillation. For example, dewatered tar is heated to about 350 ° C and flamed to remove the volatiles of combustibles. This can also be done under partial vacuum. Grain size does not matter because the coal tar pitch is used at a temperature above its softening temperature. In the present process, coal tar pitch with a softening point of between 100 and 120 ° C. is preferably used. In production, the coal tar pitch is preferably used liquid.

The green briquettes preferably contain 40-50% silica (quartz sand), 15-30% granular coke, 15-30% finely ground petroleum coke, and 8-18% coal tar pitch. Depending on the quality and / or composition of these ingredients, the exact composition of the green briquettes is determined by experiment. There may also be provided further additives.

The shaft furnace, a mixture of coal and green briquettes is preferably supplied continuously and heated. Preferably, a mixture of calcined briquettes and coke produced during calcination is discharged from the shaft furnace and separated into calcined briquettes and coke by a separation process. Prior to separation of the mixture into calcined briquettes and coke, the same is cooled on discharge. After separation, the calcined briquettes can be discharged as final products and the coke processed further to produce the green briquettes.

The separation of the coke and the calcined briquettes is preferably carried out by sieve separation. This method is particularly suitable because the briquettes and the coke differ in their size. The sieve has a mesh size which is greater than an upper limit size of the calcined coal particles (coke) and less than a lower limit of the briquette size. For this purpose, for example, a screening machine can be used, which allows a vibration of the screen. For example, a linear oscillation, a circular oscillation or other movements on the sieve can be generated for this purpose. It can also be used optical separation processes, whereby by means of a pulse, the briquettes are sorted out. A variety of variants are known to those skilled in the art. The screen separation has the advantage that it is inexpensive, efficient and low maintenance.

Of course, a separation due to the density differences, the inertial differences or other physical differences could be used. The skilled worker is familiar with a variety of suitable separation methods.

Preferably, the coke discharged from the shaft furnace is mixed with coal to control the level of volatiles and returned to the shaft furnace, particularly if the proportion of volatile combustibles in the coal is greater than 10%, preferably greater than 20% , Thus, a particularly optimized calcination process can be achieved. In particular, if the volatile content of the coal is very high, this can prevent the shaft furnace from overheating and possibly burning. The limits can be varied and, in particular, lower. It should be noted, however, that a mixture of partially calcined coal with the uncalcined coal does not have too high a proportion of partially calcined coal, especially if the process is to remain energetically self-sustaining.

Preferably, a method for the production of briquettes by the coke produced during calcination is formed together with other components to other green briquettes. Thus, the coal passes through the shaft furnace for the first time and becomes coke, then the coke is processed into green briquettes and passes through the same shaft furnace for a second time under the same conditions. As the process of coke is processed into green briquettes and calcined again with coal in the shaft furnace, the mixing ratio is preferably chosen so that in the production of a balance with respect to the entry of coal and green briquettes can arise. Namely, the coke is preferably blended with additional substances in a weight ratio of 1: 3 and formed into green briquettes. Therefore, it is advantageous to choose in the shaft furnace, the weight ratio between green briquettes and coal in the ratio 3: 1. If the weight ratios of green briquette / coal and the weight ratio of the coke to the other components of the green briquettes does not correlate, there may be an excess of coke which can not be processed directly with the same equipment or the productivity of the equipment would be under-utilized. For a different proportion by weight of coke in the green briquettes, the mixing ratio between coal and green briquettes can be adjusted when entering the shaft furnace, with the option of further parameters such as the residence time and / or the temperature also being adapted accordingly.

Preferably, the other components are silica and / or calcined petroleum coke and / or in particular liquid coal tar pitch. Of course, other substances can be added.

Preferably, the process comprises the following steps, in particular for the production of green briquettes: a) the coke is mixed with silica and petroleum coke to a dry matter mixture; b) the dry matter mixture is preheated; c) the dry matter mixture is mixed with the addition of liquid coal tar pitch to a green mass; d) the green mass is pressed to further briquettes; e) the other (hot) briquettes are conveyed through a water bath for cooling.

All promotions of the substances mentioned above can be done via a bucket elevator, conveyor belt, screw conveyor, vibratory conveyor or other funding. The mixture of coke with silica and petroleum coke and the subsequent admixture of coal tar pitch can be carried out both continuously (continuous mixture) as well as discontinuously (batch mixing). The mixer can be static (mixture over deflections of the batch) or dynamically formed. For the mixture, a drum mixer, plate mixer, plowshare mixer, tray mixer, continuous kneader or the like can be used.

The preheating of the dry mixture can be done indirectly or directly. Burners, for example gas burners, can be used for this purpose. Furthermore, heat can be removed from the shaft furnace for preheating by means of a heat exchanger. Finally, an electrical heating could also be provided. This can be achieved in the subsequent pressing a partial baking, making the green briquettes more stable. The mixing temperature should allow optimum compression of the briquettes with optimal mechanical properties.

The pressing of the hot green mass can be pressed into green briquettes, for example by means of rollers or by means of a stamping mechanism, so that the calcined briquettes also have optimum mechanical properties. The corresponding expert is also familiar with other methods. The pressure is chosen so high that the green briquettes remain largely dimensionally stable during calcination.

In the subsequent promotion of green briquettes through the water bath, the hot green briquettes are cooled.

Preferably, the device for calcining green briquettes comprises a shaft furnace, wherein an inlet of the shaft furnace communicates with a second silo for green briquettes and a first silo for coal. For this purpose, the outlets of the second and / or the first silo may be arranged spatially above the entry of the shaft furnace, so that an entry of coal and / or green briquettes can take place gravimetrically in the desired ratio, in particular by means of a conduit through shafts and / or funnels. If the entry of the shaft furnace is offset with respect to a horizontal plane to the omission of the silos, for conveying coal and / or green briquettes, a conveyor may be provided.

Preferably, the separation device for separating calcined briquettes and the coke is arranged in a region of an outlet of the shaft furnace, wherein the separation device is in particular a screen separation device. For a particularly compact design of the device is achieved.

Preferably, in the region of the first silo, a drying device for drying the (wet) coal is attached. If the discharge of the first silo is arranged above the entry of the shaft furnace, the drying device can be arranged between the discharge and the entry in order to achieve a space-saving device. However, in order to be able to gravimetrically control the entry of the coal into the shaft furnace, the drying device is preferably arranged before the entry into the first silo.

From the following detailed description and the totality of the claims, there are further advantageous embodiments and feature combinations of the invention.

Brief description of the drawings

The Fig. 1 used to explain the embodiment shows <Tb> FIG. 1 <sep> is a schematic structure of a possible embodiment of a device according to the invention.

Basically, the same parts are provided with the same reference numerals in the figure.

Ways to carry out the invention

Fig. 1 shows a schematic structure of a possible embodiment of a calcining apparatus according to the invention for calcining green briquettes 200.3.

The calcination apparatus comprises a drying apparatus 102 and a first silo 101 for the dried coal 200.1. The (wet) coal 200.1 is conveyed by the drying device 102 via an entry into the first silo 101. The arrangement may also be chosen such that the silo 101 is arranged in front of the drying device 102. The promotion can be done by gravity, or else supported by a funding and / or controlled by a metering device 103. In the drying apparatus 102, the coal 200.1 is dried, primarily to remove moisture (water). The dried coal 200.1 passes through a discharge of the drying device 102 by means of a metering device 103, which is here exemplified as a conveyor belt with gravimetric measuring device in the shaft furnace 111 of the shaft furnace 110. Parallel to green briquettes 200.3 from a second silo 170 via a gravimetric metering device 171 passed through the shaft furnace entry 111 into the shaft 114 of the shaft furnace 110.

The shaft furnace 110 essentially comprises a shaft 114, designed as a combustion chamber. This can be heated by external and / or internal heating means. According to the present invention, this is only limited or not at all necessary. When starting the method, although the shaft 114 is heated, whereby a proportion of volatile combustible constituents of the coal 200.1 is released and the heating of the shaft 114 supported. The heating then takes place by means of the combustible components via a flue 112, which is arranged on both sides of the shaft 114 of the shaft furnace 110. The Feuerzug 112 is connected to the removal of hot exhaust gases (about 800 ° C) via a heat exchanger 118 to a chimney 119. In an optimal case, the heating power of the volatile combustible component is sufficient to heat the duct 114. In this case can be dispensed with additional heating means, such as burners. Possibly, if the proportion of volatile combustible constituents of the coal 200.1 is sufficiently large, even an energy surplus is achieved, which can be dissipated by the heat exchanger 118 and used elsewhere. Thus, for example, so that the drying device 102 via a heat exchanger 118 via a heat pipe 113 (with the arrow direction is the direction of energy flow), which contains a suitable heat transfer medium (water vapor, oil or other suitable heat transfer medium) with the necessary or with a part of necessary energy to be supplied. With a heat conduction 131, heat can continue to be conducted from the heat exchanger 118 to the drying agent preheating 130 and to the mixing device 140 (see below). Finally, other facilities could be supplied with any excess heat (heat buildings, hot water, etc.). The shaft furnace 110 further comprises a discharge cooling 115 in the region of the discharge in order to cool the coke 200.2 can. This is operated here with water. It is also conceivable to include the discharge cooling 115 in the heat exchange process.

The coal 200.1 is thus guided together with green briquettes 200.3 through the shaft 114 of the shaft furnace 110 and exits after cooling by the Austragskühlung 115 from the discharge as coke 200.2 and calcined briquettes 200.4.

After the discharge of the coke 200.2 and the briquettes 200.4, these are separated by a separating device 116, which is presently designed as a sieve, so that the calcined briquettes 200.4 can be collected in a briquette container 117. The coke 200. 2 is collected in a container 121 of a drier treatment device 120.

The mixing unit comprises three containers 121, 122, 123, namely a container 121 for the coke 200.2, a container 122 for silica and a container 123 for calcined petroleum coke. The three containers 121, 122, 123 all have an adjustable discharge opening, which communicate with a gravimetric metering device 124. The coke 200.2, the silicon dioxide and the petroleum coke are mixed on this metering device 124 and conveyed into a heater inlet of a dry substance preheating unit 130, which is heated by means of the heat exchanger 118 and can thus preheat the substances mentioned above. A conveyor in the Trockenstoffvorwärmungseinheit 130 is not shown, but could for example be designed as a conveyor belt, screw conveyor or the like. The dry matter mixture is introduced into a mixing device 140, which is tempered by means of the heat exchanger 118. At the same time, liquid coal tar pitch is supplied to the dry matter mixture from a tank 141. Thus, preheated coke 200.2, silicon dioxide, petroleum coke and coal tar pitch are mixed in the mixing device 140 to form a green mass.

The green mass is then transferred from a discharge of the mixing device 140 to a briquetting device 150 which forms green briquettes 200.3 from the green mass. The shaping can be done by means of rollers. Methods for this are familiar to the person skilled in the art. After forming the green briquettes 200.3, they are passed to a water bath 160, where they are cooled and washed. From the water bath 160, the green briquettes 200.3 are conveyed by means of a conveying means 161 and transferred to a conveyor 162, which loads the green briquettes 200.3 into the second silo 170. As a result, the starting situation is virtually reached again, where from the first silo 101 coal 200.1 together with green briquettes 200.3 are guided from the second silo 170 into the shaft furnace 110.

If the coal has 200.1 too large a proportion of volatile components and thus only partially calcined in the shaft furnace 110, this can be converted by means of a return 172 back into the first silo 101. Alternatively, the partially calcined coal may also be fed directly into the dryer 102. A return of the coke can also be done if the shaft furnace is too hot (heat regulation).

In the following, an exemplary mass conversion is given, which refers to the educts or intermediates specified at the outset. The effective mass conversion may of course differ and depends on the respective specifications: 422 kg wet coal 200.1 is dried under a weight loss of 9% in the drying device 102, wherein substantially 38 kg of steam are removed. The 384 kg of dried coal 200.1 are conveyed into the shaft furnace 110 together with 1052 kg of green briquettes 200.3. The shaft furnace 110 has a temperature of 1200 ° C. During calcination, the coal loses 40% or 154 kg in weight (essentially by the proportion of volatile combustibles) and thus generates a heat output of about 8.24 gigajoules per tonne. The green briquettes 200.3 lose about 5% in weight, which corresponds to 52 kg and this weight loss may be partly responsible for the heating power. In total, 1436 kg are thus transported into the shaft furnace 110, the weight decreasing by 206 kg during the calcination. The coal 200.1 has in the shaft furnace 110, for example, a residence time between 18-36 hours. 1000 kg of calcined briquettes 200.4 are discharged as end products and conveyed into the briquette container 117 for possible further processing. The 230 kg of coke 200.2 are mixed with 460 kg of silicon dioxide having a particle size of 0.1-0.3 mm and 230 kg of petroleum coke and preheated in a drying substance preheating unit 130. This gives a total mass of 920 kg. The dry matter mixture is mixed in a mixer 140 with 132 kg coal tar pitch from the tank 141 and then formed into 1052 kg green briquettes 200.3. By choosing such a mass balance, it can be ensured that neither an intermediate product surplus nor an intermediate product deficiency can arise in the process. Even if partially calcined coal is fed back into the first silo 101 by means of the return 172, a balance can be set again after a short time.

The metering devices 103, 124, 134, 161, 162 are all shown in FIG. 1 for reasons of clarity as conveyor belts and may each comprise a gravimetric measuring device (balance), whereby the dosage can be carried out by weight. In practice, of course, any funding can be used to. Just as an example of this, the bucket elevator, the screw conveyor, the vibrating conveyor and the conveying by utilizing gravity in a fall or in free fall and discontinuous funding (cars, containers, etc.) are mentioned as continuous funding.

The shaft furnace 110 itself may be e.g. also as in the book "Chinese Raw Materials for Anode Manufacturing" (ISBN 3-9521028-7-3, pages 53-58) be formed. The shaft furnace comprises the following elements: <tb> 1. <sep> The shaft furnace is made of refractory or refractory ceramic material, with typically 12 to 32 shafts forming a shaft furnace. The individual shafts are surrounded on both sides by flues, in which the volatile components are regulated by means of supply of oxygen (air) by means of flaps so that complete combustion is achieved. <tb> 2. <sep> The calcination units are surrounded by heaters with flaps, which ensure a constant air flow. <tb> 3. <sep> Combustion air control ensures complete combustion of the volatiles. <tb> 4. <sep> The heat of the hot exhaust gas is recovered. <tb> 5. <sep> At the discharge, the calcined charge (coke and briquettes) is cooled by means of indirect water cooling.

In summary, it should be noted that a method is provided by the invention, which allows a particularly energy-efficient and cost-effective calcination of green briquettes.

Claims (21)

Method for calcining green briquettes (200.3), in particular green coal briquettes (200.3) for silicon production, wherein the green briquettes (200.3) are subjected to a heat treatment for calcination, characterized in that the green briquettes (200.3) are combined coal (200.1) containing a proportion of volatile combustibles, and calcined in a shaft furnace (110), wherein energy required for the calcination is at least partially recovered by combustion of the volatile combustible portion of the coal (200.1) becomes. 2. The method according to claim 1, characterized in that the proportion of volatile combustible constituents of the coal (200.1) is so high that the energy required for the calcination of the coal (200.1) and the green briquettes (200.3) completely from the combustion of Volatile combustible constituents of coal (200.1) can be removed. 3. The method according to claim 2, characterized in that the coal (200.1) has an ash content of less than 10%, preferably less than 5%, in particular less than 1%. 4. The method according to any one of claims 1 to 2, characterized in that the proportion of the combustible volatile constituents of the coal (200.1) greater than 20%, preferably greater than 30%, in particular between 30% and 40%. 5. The method according to any one of claims 1 to 4, characterized in that the coal (200.1) has an average particle size between 1 and 20 mm, preferably between 3 and 7 mm. 6. The method according to any one of claims 1 to 5, characterized in that the coal (200.1) is dried before being introduced into the shaft furnace (110), in particular in order to reduce a proportion of water in the coal. 7. The method according to claim 6, characterized in that the drying of the coal (200.1) at a temperature of about 100 ° C, in particular at below 150 ° C, takes place. 8. The method according to any one of claims 6 to 7, characterized in that an energy for drying the coal (200.1) via a heat exchanger (113) from the shaft furnace (110) is removed. 9. The method according to any one of claims 1 to 8, characterized in that a weight ratio between green briquettes (200.3) and coal (200.1) in a feed to the shaft furnace (110) in the range between 2: 1 and 4: 1, in particular at ca 3: 1. 10. The method according to any one of claims 1 to 9, characterized in that the shaft furnace (110) is operated at a temperature between 700 ° C and 1400 ° C, in particular between 950 ° C and 1050 ° C. 11. The method according to any one of claims 1 to 10, characterized in that the green briquettes (200.3) contain coke (200.2) and in particular additionally silica and / or petroleum coke and / or coal tar pitch. 12. The method according to claim 11, characterized in that the green briquettes (200.3) contain 40-50% silica, 15-30% coke (200.2), 15-30% petroleum coke and 8-18% coal tar pitch. 13. The method according to any one of claims 1 to 12, characterized in that a mixture of calcined briquettes and coke (200.2) produced during the calcining discharged from the shaft furnace (110) and by means of a separation process in calcined briquettes (200.4) and coke (200.2 ) is separated. 14. The method according to claim 13, characterized in that the separation of the coke (200.2) and the calcined briquettes (200.4) takes place by means of screen separation. 15. The method according to any one of claims 13 to 14, characterized in that from the shaft furnace (110) discharged coke (200.2) for regulating the proportion of volatile constituents with coal (200.1) mixed and fed back into the shaft furnace (110) in particular if the proportion of volatile combustibles in the coal (200.1) is higher than 30%, preferably higher than 40%. 16. Application of the method according to any one of claims 1 to 15 for the production of briquettes, characterized in that the coke produced during the calcination (200.2) is formed together with other components to further green briquettes (200.3). 17. The method according to claim 16, characterized in that it is in the other components to silica and / or petroleum coke and / or coal tar pitch. 18. The method according to claim 17, comprising the following steps: a) the coke (200.2) is mixed with silica and petroleum coke to a dry matter mixture; b) the dry matter mixture is preheated; c) the dry matter mixture is mixed with the admixture of particular liquid coal tar pitch to a green mass; d) the green mass is pressed to further green briquettes; e) the other green briquettes are conveyed through a water bath for cooling. Apparatus for calcining green briquettes (200.3) using a method according to any one of claims 1 to 17, comprising a shaft furnace (110), characterized in that an inlet of the shaft furnace (110) with a second silo (170) for green Briquettes (200.3) and a first silo (101) for coal (200.1) communicates. 20. The apparatus according to claim 19, characterized in that in a region of an outlet of the shaft furnace (110) a separating device for the separation of calcined briquettes (200.4) and coke (200.2) is arranged, wherein it is at the separating device (116) in particular a sieve separating device is. 21. Device according to one of claims 19 to 20, characterized in that in the region of the first silo (101) a drying device (102) for drying the coal (200.1) is mounted.