EP2524729A1 - Assembly and method for dry-grinding and storing lignite fuel - Google Patents

Abstract

Lignite is ground and dried to obtain lignite dust in a mill with a low-oxygen gas and a drying gas inlet temperature more than ignition temperature of lignite. The dried and ground dust is discharged from the mill by a primary carrier gas. The conveyed dust is rinsed with a dry oxygen-poor gas to replace carrier gas with secondary feed gas. The dust is further conveyed by another carrier gas and stored in a silo at temperature of 60[deg] C in low oxygen-containing dry atmosphere. Thus, drying, grinding and storage of lignite are enabled.

Description

During the grinding drying of raw lignite, the lignite is to be ground to a small particle size. At the same time the raw lignite is to be deprived of moisture, so that after the mill drying lignite dust with low moisture is available. In the prior art, it is known to dry the brown coal in a dryer (eg a tube dryer) and thus to extract the moisture from the brown coal. Subsequently, the dried lignite is ground to brown coal dust and stored. In order to avoid the risk of explosion during the grinding process and the risk of spontaneous combustion during storage, maximum temperatures are provided for grinding and storage below the explosion or auto-ignition temperature. In the DE 42 23 151 are specified as temperature ranges for grinding 70 to 85 ° C, for storage maximum 60 ° C. These temperatures can only be achieved by active cooling.

Furthermore, it is known to carry out the grinding of lignite and the drying of the same in a single process stage. For this purpose, the brown coal is dried during the grinding process, for example. By blowing hot gas into the Grinding room of the mill. However, in order to avoid dust explosions in the mill, the drying gas must not exceed a certain temperature when entering the mill. VDI 2263 stipulates that the corresponding gas inlet temperature must not exceed 2/3 of the ignition temperature of the material to be ground. This means for the grinding of lignite a maximum gas inlet temperature of the drying gas of about 270 ° C. The lignite dust produced by a corresponding process has a temperature of about 90 ° C at the exit from the mill and must be actively cooled to below 60 ° C for safe storage.

In processes in which lignite is dry-milled and then fired directly in a boiler, it is also known to use flue gas for drying in the mill. The flue gas has a temperature above the ignition temperature of lignite, for example. 1000 ° C. At the same time, however, this flue gas has a low oxygen content of about 6 to 12 vol .-%, so that dust explosions can be prevented within the mill. Since the lignite dust is then burned directly, there is virtually no danger that there will be a dust explosion and / or spontaneous combustion of lignite dust.

Object of the present invention is to provide a comparison with the above-mentioned prior art improved process or an improved plant for grinding drying and storage of lignite.

This object is achieved by a method according to the main claim and a system according to the sibling Claim. Advantageous developments emerge from the dependent claims.

1. a) Mahlen und Trocknen von Braunkohle zu Braunkohlestaub in einer Mühle mit einem sauerstoffarmen Trocknungsgas und einer Gaseintrittstemperatur oberhalb der Zündtemperatur von Braunkohle;
2. b) Förderung des gemahlenen und getrockneten Braunkohlestaubs aus der Mühle mit Hilfe eines ersten Fördergases;
3. c) Spülen des geförderten Braunkohlestaubes mit einem trockenen, gegenüber dem ersten Fördergas noch sauerstoffärmeren zweiten Fördergas zum Austausch des ersten Fördergases mit dem zweiten Fördergas;
4. d) Weiterförderung des Braunkohlestaubes mit Hilfe des zweiten Fördergases; und
5. e) Einlagerung des weitergeförderten Braunkohlestaubes in einem Silo bei einer Temperatur von über 60°C und sauerstoffarmer, trockener Atmosphäre.

Accordingly, the invention relates to a process for the milling drying and storage of lignite comprising the steps:

1. a) grinding and drying lignite to brown coal dust in a mill with a low-oxygen drying gas and a gas inlet temperature above the ignition temperature of lignite;
2. b) conveying the ground and dried brown coal dust from the mill by means of a first conveying gas;
3. c) rinsing the extracted lignite dust with a dry, compared to the first carrier gas still oxygen poorer second conveying gas for exchanging the first conveying gas with the second conveying gas;
4. d) further promotion of brown coal dust with the help of the second conveying gas; and
5. e) Storage of the further transported lignite dust in a silo at a temperature of over 60 ° C and oxygen-poor, dry atmosphere.

The invention further relates to a plant for grinding drying lignite, comprising a mill for crushing lignite to brown coal dust and a silo for storage of lignite dust, the mill having a Gaszuführöffnung for drying gas and a material outlet for ground and dried lignite dust, with a Dust washing system connected to the material outlet of the mill and the silo for flushing the lignite dust with a dry, oxygen-poor second conveying gas is provided.

"Low oxygen" in the context of this invention means that the oxygen content of a gas or an atmosphere is below the oxygen content of air, preferably by 10%, possibly even below it. In the case of a gas which is still oxygen-poorer than an oxygen-poor gas, the oxygen content is preferably 3% or less. For the purposes of this invention, a gas or an atmosphere is "dry" if the respective water content is less than 3% by volume.

"Rinsing" in the sense of this invention comprises on the one hand the replacement of a first gas by a second gas. On the other hand, it can also be provided that the first gas is mixed with another gas or diluted by it, so that the second gas is formed.

"Brown coal" in the context of this invention includes as a generic term both hard lignite and lignite.

With the method according to the invention, it is possible to reduce the proportion of water in lignite of, for example, originally 30% by volume to 8% by volume and at the same time to achieve comminution to particles having a particle size of less than 500 μm. The invention has recognized that in the lignite drying with subsequent storage temperatures can be used, which are above the maximum temperatures specified in the prior art, without causing explosions or spontaneous combustion when At the same time oxygen and / or water content in the atmosphere surrounding the lignite or lignite dust is sufficiently reduced that an explosion or autoignition reaction is not initiated. This is especially true during milling and storage of lignite dust.

A dust explosion occurs when, in the oxygen-rich atmosphere, e.g. Air, finely divided, solid dust particles of a combustible substance ignited or heated to a temperature above the ignition temperature. Due to the large common surface of the dust particles, there is a sudden explosion-like ignition of the entire dust.

If lignite dust, which is dried under its equilibrium moisture, stored at elevated temperature and freely available humidity, it comes to condensation of humidity, which leads to an increase in the temperature of lignite dust. With increasing temperature then dissolved in the dust particle gap or gusset volume of further oxygen exothermic reactions. With the temperature still rising, the oxygen bound in the coal becomes the free partner for exothermic reactions in the entire lignite dust volume, and the lignite dust is self-ignited.

According to the invention, it is provided that the brown coal is semi-dried in a mill. The drying gas required for the drying has a gas inlet temperature (the temperature of the drying gas entering the mill) above the ignition temperature of lignite. At the same time, the drying gas is one oxygen-poor gas, so that dust explosions are effectively avoided in the mill despite the aforementioned gas inlet temperature. The oxygen content of the drying gas is preferably less than or equal to 12% by volume, more preferably between 8 and 12% by volume. The water content of the drying gas is preferably less than or equal to 35% by volume. It is further preferred if the water content of the drying gas is adjusted so that a water content of less than or equal to 35% by volume is established in the atmosphere within the mill.

In a corresponding drying gas gas inlet temperatures above the ignition temperature of lignite are possible. The gas inlet temperature of the drying gas is preferably below or at 850 ° C., more preferably below or at 625 ° C., more preferably at 625 ° C. With the latter temperature, a good drying effect can be achieved. At the same time - as studies have shown - it is possible to use steel 1.4878 for the different components of the mill. By taking into account the limits of use of this steel, the mill can be manufactured comparatively inexpensively. If higher gas inlet temperatures are required or desired, it may be necessary to manufacture individual components of the mill from more costly materials.

The mill is preferably adjusted so that the milled brown coal or lignite dust has an average product fineness of 40 to 100 microns. The mill is preferably designed as a ball ring mill. However, all types of airflow mills, esp. All types of Wälzmühlen, can be used.

After the mill drying, the brown coal dust is conveyed out of the mill with the aid of a first conveying gas. The lignite dust at this time has a temperature of well over 60 ° C. In particular, its temperature may be 70 to 110 ° C, preferably 80 to 100 ° C, preferably 90 ° C. The first conveying gas may preferably be drying gas. In this case, the drying gas introduced into the mill when leaving the mill can entrain sufficiently finely ground lignite particles and thus convey it out of the mill. If a gas other than the drying gas is used as the first conveying gas, the temperature and oxygen content of this gas must be selected so that the risk of a dust explosion is avoided. The first conveying gas or drying gas generally has a high water content, since the liberated in the mill from the lignite, released water is carried in the first conveying gas or drying gas.

The pulverized lignite coal dust conveyed from the mill with the first conveying gas is subsequently rinsed with a dry second conveying gas, which is still oxygen-poorer than the first conveying gas. In this case, it is preferable for a virtually complete replacement of the first conveying gas by the second conveying gas. The second conveying gas preferably has an oxygen content of less than or equal to 3% by volume and preferably a water content of less than or equal to 5% by volume, more preferably less than 3% by volume. For flushing the lignite dust, for example, a gas conveying trough can be used, in which the lignite dust is passed through a gas-permeable soil. From the gas-permeable bottom then exits the second conveying gas and displaces the first conveying gas from the interstices of brown coal dust. Is it in the first carrier gas to drying gas Both the oxygen and the water content in the lignite dust-gas mixture are significantly reduced by the above flushing, since it is the oxygen-poor, dry gas, the oxygen and water content is generally lower than that of the drying gas in the second conveying gas. Accordingly, this also applies if the first conveying gas is not the drying gas. The second conveying gas thus preferably has a smaller proportion of oxygen and water than the first conveying gas.

Alternatively, it is possible that the mixture of first conveying gas and brown coal dust another gas is mixed, so that the second conveying gas is formed by mixing the first conveying gas with the other gas. The first conveying gas is thus by mixing or dilution by the additional gas to the second conveying gas.

With the help of the second conveying gas the lignite dust is then further promoted and ultimately stored in a silo. The temperature of lignite dust is about 60 ° C during storage, usually around 90 ° C. In order to avoid self-ignition of brown coal dust in the silo, there is a low-oxygen and dry atmosphere in the silo. By introducing the brown coal dust into the silo with the help of the likewise dry and oxygen-poor second conveying gas, a corresponding atmosphere can be maintained even when brown coal dust is supplied. The oxygen content in the atmosphere in the silo is preferably less than or equal to 3% by volume. The water content of the atmosphere in the silo is preferably less than or equal to 3% by volume. In an appropriate atmosphere, it is possible that the temperature of the brown coal dust when stored in silo 70 to 110 ° C, preferably 80 to 100 ° C, preferably 90 ° C, without the risk of auto-ignition.

Furthermore, it can be provided that the silo can be rinsed with dry and oxygen-poor gas. A corresponding flushing can, if necessary, for example. With appropriate monitoring of the atmosphere in the silo, or take place regularly. By means of a suitable flushing it can be ensured that the atmosphere in the silo is constantly dry and low in oxygen, so that self-ignition of the lignite dust in the silo can be effectively prevented.

Furthermore, it is preferred if in the silo and / or the mill, there is an overpressure relative to the atmosphere. As a result, an external air infiltration (unwanted influx of ambient air with a possibly high oxygen and / or water content) is effectively avoided.

As the second conveying gas and / or gas for rinsing the silo, an inert gas, for example nitrogen, is preferably used. In order to achieve the required or desired oxygen and / or water content in the individual aforementioned gases, the inert gas can optionally be adjusted to the desired composition with humidifiers and dehumidifiers, as well as by mixing with air. For the drying gas and / or the first conveying gas, it is also possible, instead of an inert gas combustion gases or the like. to use with a low oxygen content. By mixing with air and / or the use of humidifiers and dehumidifiers, any oxygen and water content can be adjusted even with combustion exhaust gases.

The invention further relates to a plant for grinding drying and storage of lignite, which is designed for carrying out the method according to the invention. The plant according to the invention comprises a mill for comminuting lignite to brown coal dust and a silo for storing lignite dust, the mill having a gas feed opening for drying gas and a material outlet for ground and dried lignite dust, and a dust washing plant connected to the material outlet of the mill and the silo is provided for flushing the lignite dust with dry, oxygen-poor second conveying gas.

Furthermore, it is preferred if the silo has a gas inlet opening for dry and oxygen-poor gas and that a regulating device is provided which controls the gas supply to the mill and / or the silo so that the operating parameters of the method according to the invention are maintained.

It is preferred if the dust washing system is designed to rinse the lignite dust as a gas-driven conveyor trough, in which the brown coal dust flows together with a first conveying gas via a gas-permeable bottom. The second conveying gas flows through the air-permeable bottom and displaces the first conveying gas from the spaces between the lignite dust.

It is further preferred if the silo and / or the mill are formed against fresh air penetration. For this purpose, it can be provided that the mill and / or the silo are particularly sealed. In particular, individual components of the mill and / or the silo can be welded together pressure-tight for this purpose.

The term "silo" is to be construed broadly in the context of this invention. Thus, the term silo includes not only stationary storage but also, for example, tank cars or corresponding trucks.

The lignite dust stored in the silo can be removed at will and used, for example, in coal gasification or briquette production, but also for firing blast furnaces or in power plants.

At the mill cooling elements may be provided which are activated in the event of an interruption in operation to cool down in the mill accumulating lignite dust to the extent that there is no auto-ignition or smoldering. However, the cooling elements are not activated during proper operation and thus do not develop any cooling effect. Furthermore, in the mill, devices, e.g. Ausräumer be provided, which can eliminate deposits of brown coal dust during operation. In the mill, an extinguishing device can be provided with the possibly occurring smoldering fires can be deleted.

Figur 1

eine erfindungsgemäße Anlage zur Mahltrock-nung und Einlagerung von Braunkohle;

Figur 2

eine Detailansicht der Mühle der Anlage ge-mäß Figur 1;

Figur 3a-c

Detaildarstellung möglicher Staubwaschanlage für die Anlage gemäß Figur 1;

Figur 4

eine Detaildarstellung des Silos der Anlage gemäß Figur 1; und

Figur 5

eine schematische Darstellung des mit der Anlage aus Figur 1 durchgeführten, erfin-dungsgemäßen Verfahrens.

The invention will now be described with reference to an advantageous embodiment with reference to the accompanying drawings. Show it:

FIG. 1

a plant according to the invention for Mahltrock- tion and storage of lignite;

FIG. 2

a detailed view of the mill of the plant according to FIG. 1 ;

Figure 3a-c

Detailed representation of possible dust washing system for the system according to FIG. 1 ;

FIG. 4

a detailed view of the silo of the system according to FIG. 1 ; and

FIG. 5

a schematic representation of the with the plant FIG. 1 carried out, inventive method according to the invention.

In FIG. 1 a plant 1 according to the invention for grinding drying and storage of brown coal is shown. In FIG. 5 is performed by this Appendix 1 method 100 is shown schematically.

The plant 1 comprises a mill 20, a dust washing plant 30 and a silo 40. The structure of the mill 20, the dust washing plant 30 and the silo 40 is in the FIGS. 2 to 4 shown in more detail. Furthermore, in the system 1, a feeding device 2a, a filter 2b, a fan 2c, a gas source 3 and a heating element 4 are provided. The heating element 4 may in particular be a hot gas generator.

The brown coal destined for grinding drying and storage reaches the mill 20 via the feeding device 2 in a metered manner. The feeding device 2 is operated in such a way that the filling level in the mill 20 always lies within a predetermined tolerance range.

In the mill 20, the first process step 101, the grinding and drying of the brown coal to brown coal dust, carried out.

The mill 20 is, as in FIG. 2 shown to a ball ring mill, in which the brown coal is fed through a material inlet 21 a grinder 22. The lignite is ground in the grinder 22 in a known manner and then exits laterally from the grinder 22. Arranged annularly around the grinder 22 at the bottom, a nozzle ring 23 is provided, through which the delivery gas flows. The milled brown coal is entrained by the first conveying gas and transported to a sifter 24 in the upper region of the mill 20. By the separator 24 particles that have not yet reached the desired fineness of, in this case, below 500 microns, sorted out and fed to the grinder 22 again. Sufficient fine particles with a particle size of less than 500 microns form the desired lignite dust and are promoted by the first delivery gas through the material outlet 26.

At the mill 20 in FIG. 2 the first conveying gas is at the same time the drying gas according to the invention. The drying gas enters the mill 20 via the connection 27 at a temperature above the ignition temperature of the brown coal to be ground. This gas inlet temperature is 625 ° C. In addition, the drying gas still has an oxygen content of less than or equal to 12% by volume and a water content of less than or equal to 35% by volume.

The volume flow of the drying gas is determined by the fan 2c. The composition of the drying gas results from the hot gases from the heating element 4, the steam vaporized from the coal and possibly entering leakage air flows and possibly an inert gas, which is provided by the gas source 3 available.

The feeding of the aforementioned drying gas into the mill 20 has the result that within the mill 20, a sufficiently high temperature results, which causes a drying of the brown coal. Although corresponding temperatures would lead to dust explosions under normal atmospheric conditions, dust explosions are effectively prevented by the low oxygen content in the drying gas and thus also within the mill 20.

The ground and dried lignite passes together with the drying gas (or first conveying gas) into the material outlet 26, provided that the desired particle size has been reached, ie the lignite is present in the form of lignite dust. The lignite dust has a temperature of about 90 ° C at this point. Since the brown coal dust is still surrounded by the oxygen-poor drying gas, dust explosions are not to be feared.

The lignite dust is conveyed in the next step 102 with the aid of the drying gas (or first conveying gas) from the material outlet 26 of the mill 20 via a connecting line 5 in a filter 2b and deposited there. The separated brown coal dust is further conveyed to a dust washer 30 and rinsed there (step 103). Various embodiments of dust washing systems 30 are shown in FIG FIGS. 3a-c shown in more detail. The dust washer 30 can, depending on the requirement of one of in FIGS. 3a-c systems are realized.

In the dust washer according to FIG. 3a The mixture of drying gas and lignite dust passes through the inlet 31 into the dust washer 30, which is designed as a ventilation box. The dust washing system 30 is characterized in that the flow channel 32 for the lignite dust has a gas-permeable bottom 33 and a gas-permeable upper boundary 34. Seen from the flow channel 32 are located behind the gas-permeable bottom 33 and the gas-permeable upper boundary 34 each have a gas distribution chamber 35, 36. The lower gas distribution chamber 35 is connected to the gas source 3 (see. FIG. 1 ), while the upper gas distribution chamber 36 is connected to the environment. In the lower gas distribution chamber 35, a second conveying gas is introduced from the gas source 3, which flows through the gas-permeable bottom 33 into the flow channel 32. By the second conveying gas flows into the flow channel 32, in which the mixture of lignite dust and drying gases (or first conveying gas) are, the brown coal dust is washed. The second conveying gas displaces the drying gas (or first conveying gas) from the interstices of the lignite dust. The drying gas (or first conveying gas) passes via the gas-permeable upper boundary 34 into the gas distribution chamber 36 and from there into the environment. As a result, there is a mixture of brown coal dust and second conveying gas at the exit of the dust washing system 30.

The dust washing system 30 according to FIG. 3b is designed as a gas conveyor trough and works in principle as the dust washing system 30 according to FIG. 3a , The mixture of drying gas and brown coal dust passes through the inlet 31 into the dust washing system 30. The dust washing system 30 comprises one of the flow channel 32 for the lignite dust, which has a gas-permeable bottom 33. Below the gas-permeable bottom 33 is a gas distribution chamber 35 which is connected to the gas source 3 (see. FIG. 1 ) connected is. In the lower gas distribution chamber 35, a second conveying gas is introduced from the gas source 3, which flows through the gas-permeable bottom 33 into the flow channel 32. By the second conveying gas flows into the flow channel 32, in which the mixture of lignite dust and drying gases (or first conveying gas) are, the brown coal dust is washed. The second conveying gas displaces the drying gas (or first conveying gas) from the interstices of the lignite dust. The drying gas (or first conveying gas) passes through the gas outlet 37 into the environment. As a result, there is a mixture of brown coal dust and second conveying gas at the exit of the dust washing system 30.

The dust washer 30 in Figure 3c is designed as a pneumatic conveyor line. The mixture of drying gas and lignite dust passes through a Einschleußorgan 31 'in the dust washing system 30. The dust washing system 30 includes a flow channel 32 for the lignite dust, which has a gas-permeable bottom 33. Below the gas-permeable bottom 33 is a gas distribution chamber 35 which is connected to the gas source 3 (see. FIG. 1 ) connected is. In the lower gas distribution chamber 35, a gas is introduced from the gas source 3, which flows through the gas-permeable bottom 33 into the flow channel 32. In addition, the gas is still introduced at one end of the flow channel 32, whereby an impulse is exerted on the lignite dust-gas mixture, so that a promotion of lignite dust to the other end of the flow channel 32nd is reached. Due to the gas introduced into the flow channel 32, the drying gas (or first conveying gas) is diluted in such a way that the second conveying gas is formed. The mixture of brown coal dust and second conveying gas then exits at the end of the pneumatic conveying line.

The second conveying gas has a lower oxygen and / or water content than the drying gas (or first conveying gas). This is especially true since the water released from the brown coal during drying is entrained with the drying gas and increases its water content. The second conveying gas is characterized by the fact that the oxygen content is less than or equal to 3% by volume and the water content is less than 3% by volume. A corresponding gas is provided by the gas source 3.

Starting from the dust washing system, the mixture of second conveying gas and brown coal dust is conveyed on via the connecting line 6 to the silo 40 (step 104). The temperature of the lignite dust has not changed substantially by the promotion and the flushing, so that the brown coal dust at entry into the silo 40 has a temperature of about 90 ° C. The brown coal dust is thus stored at a temperature of 90 ° C in the silo 40 (step 105).

The lignite dust arrives together with the second conveying gas in the silo 40 and is stored there. Since constantly second conveying gas flows together with the brown coal dust to the silo 40, an atmosphere with an oxygen content of less than or equal to 3% by volume and a water content of less than or equal to 3% by volume is established in the silo 40. In a corresponding atmosphere is the storage of lignite dust at a temperature of up to 90 ° C possible, in particular, no auto-ignition occurs.

The lignite dust settles due to gravity at the bottom 41 of the silo interior 42 and can be removed through an opening 43 in the bottom 41 of the silo. Since along with the lignite dust constantly second delivery gas flows to the silo, also a vent valve 44 is provided, with the gas can be discharged into the environment. The vent valve 44 is equipped with dust filters, so that it is permeable only to gas.

In order to be able to regulate the atmosphere in the silo interior 42, gas inlet openings 45 are provided on the bottom 41 and / or in the side wall of the silo 40, with which gas originating from the gas source 3 can be fed into the silo interior 42. By a (not shown) control unit, it is possible to monitor the atmosphere in the silo interior 42 and optionally regulate by supplying gas of predetermined composition, so that the atmosphere in the silo interior 42 an oxygen content of less than or equal to 3 vol% and a water content of less than or equal to 3% by volume. Thus, a spontaneous ignition of lignite dust in the silo interior 42 can be permanently prevented.

In Siloinnenraum 42 prevails over the environment, an overpressure. As a result, it can be avoided that ambient air with a higher oxygen and / or water content can penetrate through any leaks in the silo 40 and possibly cause undesired reactions.

Claims (14)

Process for the milling drying and storage of lignite, comprising the steps: a) grinding and drying (101) lignite to lignite dust in a mill (20) with a low-oxygen drying gas and a gas inlet temperature above the ignition temperature of lignite; b) conveying (102) the ground and dried lignite dust from the mill (20) by means of a first conveying gas; c) purging (103) the extracted brown coal dust with a dry, oxygen-poor second conveying gas for exchanging the first conveying gas with the second conveying gas; d) further conveying (104) the brown coal dust with the aid of the second conveying gas; and e) Storage (105) of the further transported lignite dust in a silo (40) at a temperature of over 60 ° C and oxygen-poor, dry atmosphere. A method according to claim 1, characterized in that the drying gas has an oxygen content of less than or equal to 12 vol .-%, preferably 8 to 12 vol .-%, and a water content of less than or equal to 35 vol .-%. Method according to one of the preceding claims, characterized in that the second conveying gas has an oxygen content of less than or equal to 3 vol .-% and / or a water content of less than or equal to 3 vol .-%. Method according to one of the preceding claims, characterized in that the oxygen content in the silo less than or equal to 3 vol .-% and / or the water content is less than or equal to 3 vol .-%. Method according to one of the preceding claims, characterized in that the gas inlet temperature of the drying gas is 625 ° C. Method according to one of the preceding claims, characterized in that the temperature of the lignite dust when stored in the silo 70 to 110 ° C, preferably 80 to 100 ° C, preferably 90 ° C. Method according to one of the preceding claims, characterized in that the lignite dust has a mean product fineness of 40 to 100 microns. Method according to one of the preceding claims, characterized in that the first conveying gas is drying gas. Method according to one of the preceding claims, characterized in that when increasing the oxygen and / or water content in the silo (40), the silo (40) is rinsed with dry, oxygen-poor gas. Method according to one of the preceding claims, characterized in that the second conveying gas is essentially an inert gas, preferably nitrogen. Method according to one of the preceding claims, characterized in that in the silo (40) an overpressure relative to the environment is set. Plant for grinding drying and storage of lignite, comprising a mill (20) for comminuting lignite to brown coal dust and a silo (40) for storing lignite dust, characterized in that the mill (20) comprises a gas feed opening (27) for drying gas and a material outlet (26) for milled and dried lignite dust, and a dust washing plant (30) connected to the material outlet (26) of the mill (20) and the silo (40) is provided for purging the lignite dust with dry, oxygen-poor second conveying gas. Installation according to claim 12, characterized in that the silo (40) has a gas inlet opening (45) for dry and oxygen-poor gas and a control device is provided which controls the gas supply into the mill (20) and / or the silo (40) in that the operating parameters from at least one of claims 1 to 7 are complied with. Plant according to claim 12 or 13, characterized in that the plant 1 for carrying out the method according to one of claims 1 to 12 is formed.

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