EP2709765A1

EP2709765A1 - Installation and method for the mill drying and storage of brown coal

Info

Publication number: EP2709765A1
Application number: EP12708693.2A
Authority: EP
Inventors: Jens-Peter Thiel
Original assignee: Claudius Peters Projects GmbH
Current assignee: Claudius Peters Projects GmbH
Priority date: 2011-05-20
Filing date: 2012-01-12
Publication date: 2014-03-26
Also published as: CN104039455B; US20120292413A1; JP5838261B2; US8517290B2; JP2014520050A; EP2524729A1; WO2012159776A1; CN104039455A

Abstract

The invention relates to a method and to an installation (1) for the mill drying and storage of brown coal. According to the invention, brown coal is ground into brown-coal dust in an oxygen-deficient atmosphere at temperatures which are higher than those in the prior art. Thereafter, the brown-coal dust is washed in an oxygen-deficient, dry, second carrier gas and is stored in a silo in an oxygen-deficient, dry atmosphere at a temperature of above 60°C. The installation (1) according to the invention is designed for implementing the method according to the invention and comprises, for the aforementioned method steps, a mill (20), a dust-washing installation (30) and a silo (40).

Description

Plant and process for grinding drying and storage of

Brown coal

The invention relates to a method and a plant for grinding drying and storage of lignite. During the grinding drying of raw lignite, the lignite is to be ground to a small particle size. Gleichzei ^¬ tig to be removed from the raw lignite moisture so that brown coal dust is available after the drying and grinding of low humidity. In the prior art, it is known to dry the brown coal in a dryer (eg a tube dryer) and thus 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 self-ignition temperature. In DE 42 23 151 are given 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 at exit from the mill at a temperature of about 90 ° C and must be actively cooled to below 60 ° C ^¬ for safe storage.

In processes in which lignite is ground-dried and then burned 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 this flue gas, however, a small sow erstoffanteil of about 6 to 12 vol .-% so that dust has Exploring ^¬ emissions 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.

Accordingly, the invention relates to a process for grinding drying and storage of lignite comprising the steps of: 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; b) promoting the ground and dried lignite lestaubs from the mill with the aid of a first För ^¬ dergases; c) purging the extracted lignite dust with a dry, compared to the first conveying gas still oxygen poorer second conveying gas for exchanging the first conveying gas with the second conveying gas; d) further promotion of brown coal dust with the help of the second conveying gas; and e) incorporation 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 connected to the material outlet of the mill and the silo

Dust washing plant for flushing the lignite dust with ei ^¬ nem dry, oxygen-poor second conveying gas is provided.

For the purposes of this invention, "oxygen-poor" means that the oxygen content of a gas or an atmosphere is ^less than 10%, if appropriate also lower, than the oxygen content of air 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.

For the purposes of this invention, "purging" comprises, on the one hand, the replacement of a first gas with a second gas, but on the other hand, it may also be provided that the first gas is mixed with another gas or diluted by it, so that the second gas is produced.

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

With the inventive method it is possible originally to reduce the water content of lignite, for example. 30 vol% to 8 vol .-% and simultaneously attain a Zerklei ^¬ beautification to particles having a particle size of less than 500 μπι. 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 the grinding and at the insert ^¬ tion of lignite dust.

A dust explosion occurs when in the oxygen-rich atmosphere, such as 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 Staubparti ^¬ cle, there is a sudden explosion-like ignition of the entire dust.

Is pulverized lignite, which is dried under its equilibrium moisture content, stored at elevated temperature and free verfüg ^¬ Barer humidity, there is Kondensati ^¬ on the humidity, which leads to an increase in temperature of the brown coal dust. With increasing temperature then dissolved in the dust particle gap or gusset volume of further oxygen exothermic reactions. As the temperature of the still rising temperature increases, the oxygen bound in the coal becomes a free partner for exothermic reactions in the entire lignite dust volume and spontaneous combustion of lignite dust occurs.

The invention provides that the lignite is mahlgetrocknet in ei ^¬ ner mill. The require derliche for drying the drying gas has in this case (the temperature of the drying gas when entering the mill) above the ignition temperature of brown coal to a gas inlet Tempe ^¬ temperature. 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 less than or equal to 8% by volume, more preferably less than or equal to 6

Vol .-%. It can also be provided that the oxygen content of the drying gas is 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.

With a corresponding drying gas, gas inlet temperatures above the ignition temperature of lignite are possible. Preferably, the gas inlet temperature of the drying gas lies below or at 850 ° C, more before Trains t ^¬ below or at 625 ° C, more preferably below or at 550 ° C. It can also be provided that the gas inlet temperature of the drying gas is 625 ° C., more preferably 500 ° C. With the latter temperatures, 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 ^¬ outlet temperatures needed or desired, individual components of the mill must be manufactured from costly materials works if necessary.

The mill is preferably adjusted so that the milled brown coal or lignite dust is a medium product has fineness of 40 to 100 μπι. The mill is performed before ^¬ Trains t as a ball ring mill. However, it all Ar ^¬. Th airflow mills, especially all kinds of roller mills can be used.

In the mill, so a coal dust, which has a detectable according to DIN EN 50281-2-1 ignition temperature. For a coal dust-air mixture with a product fineness of 45% residue on 90μπι the ignition temperature at an oxygen content of 21 vol .-% according to DIN EN 50281-2-1 so for example. At 400 ° C, with an oxygen content of 12 Vol .-% at 540 ° C. By way of derogation from the cited standard, it is also possible to ascertain when the first ignition sparks occur in the pulverized coal / air mixture, if the test procedure is otherwise the same. At an oxygen content of 12% by volume, this may be the case, for example, from 460 ° C., at 10% by volume from 500 ° C., at 8% by volume from 520 ° C. and at 6% by volume of oxygen ^¬ part from 650 ° C. For the example described carbon, but also for at ^¬ particular comparable coals, can according to the invention Ver ^¬ drive the example. At a gas inlet temperature of 500 ° C and an oxygen content of the drying gas of less ^¬ equal to 6 vol .-% can be carried out safely, without an ignitable coal-gas mixture is formed. The parameters can be chosen so that a sufficient ^{security ¬ is provided} against auto-ignition and explosions. Parameters suitable for safely carrying out the method according to the invention are inter alia also dependent on the millbase, ie the type of coal, and the freeness.

After the mill drying, the brown coal dust is conveyed out of the mill with the aid of a first conveying gas. Of the Brown coal dust has a temperature of well over 60 ° C at this time. 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. Is used as the first conveying gas to another gas as the drying gas, Tempe ^¬ temperature and oxygen content of this gas must be chosen so that the risk of dust explosion is avoided. The first conveyor gas or drying gas generally has a high water content as the derived in the mill from the brown coal ^¬, the water liberated is entrained in the first conveyor ^¬ gas or drying gas.

The conveyed to the first conveying gas from the mill ge ^¬-ground brown coal dust is then rinsed still poorer oxygen gas with a second conveyor Trocke ^¬ NEN, compared with 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 rinsing the brown coal dust, for example, can. A gas conveying channel is set to be ^¬, wherein the lignite dust is passed through a gas permeable bottom ^¬. The second conveying gas then emerges from the gas-permeable bottom and displaces the first conveying gas from the interstices of the lignite dust. Is it in the first conveying gas to trock ^¬ voltage gas are by the above flushing both the oxygen and the water content in lignite Clear dust-gas mixture significantly reduced, since it is han ^¬ poor in the second carrier gas, oxygen-poor, dry gas whose oxygen and water content is in principle ge ^¬ ringer than that of the drying gas. Accordingly, this also applies if the first conveying gas is not the drying gas. The second conveying gas therefore preferably has a ^lower 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. A self lignite dust in the silo to avoid ignition, there in the silo a low-oxygen atmosphere, a dry and re ^¬. By the brown coal dust with the aid of also tro ^¬ ckenen and oxygen-depleted second conveying gas is introduced into the silo, an appropriate atmosphere can be maintained even when the supply of pulverized lignite. 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 entspre ^¬ chender atmosphere, it is possible that the temperature of the brown coal dust at storage in the silo 70 to 110 ° C, preferably 80 to 100 ° C, preferably 90 ° C, without the risk of self-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 regularly suc ^¬ gene. By a corresponding flushing can be ensured that the atmosphere in the silo is constantly dry and low in oxygen, so that a spontaneous combustion of 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. To achieve the required or desired oxygen and / or water contents in the individual aforementioned gases, the inert gas may optionally be adjusted with humidifiers and dehumidifiers and by mixing with air to the desired together ^¬ mensetzung. 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. When mixed with air and / or the use of humidifiers and dehumidifiers any oxygen and adjust what ^¬ sera parts can also be in 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. He invention ^¬ proper installation comprises a mill for the comminution from 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 for purging the lignite dust with tro ^¬ ckenem , oxygen-poor second conveying gas is provided.

It is furthermore 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 preferable that the dust washer for rinsing the brown coal dust being formed as a gas-powered conveyor trough ^¬ is, in which the lignite dust flows along with a first carrier gas through a gas-permeable bottom. The second conveying gas flows through the air-permeable Bo ^¬ den and displaces the first conveying gas from the Zwischenräu ^¬ men of brown coal dust.

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

The term "silo" should be interpreted broadly in the context of this invention. but also, for example, tank wagons or corresponding lorries.

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 can be provided, which are activated in the event of a business interruption in order as far abzuküh ^¬ len in the mill accumulating pulverized lignite that there is no spontaneous combustion or a smoldering fire. The cooling elements are not activated during the ordnungsge ^¬ MAESSEN operation and thereby exercising any cooling effect. Furthermore, can be provided which can be deposits of brown coal dust during operation be ^¬ side in the mill devices, eg reamers. In the mill, an extinguishing device can be provided with the possibly occurring smoldering fires can be deleted.

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

1 shows a plant according to the invention for Mahltrock ^¬ tion and storage of brown coal

FIG. 2 shows a detailed view of the mill of the installation according to FIG. 1;

Figure 3a-c detailed representation of possible dust washing system for the system of Figure 1; Figure 4 is a detailed view of the silo of the system of Figure 1; and Figure 5 is a schematic representation of the with the

Plant carried out from Figure 1, the inventive method.

FIG. 1 shows an installation 1 according to the invention for the milling drying and storage of brown coal. In FIG. 5, the method 100 carried out with this plant 1 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 ^¬ system 30 and the silo 40 is shown in more detail in Figures 2 to 4. 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 be a hot gas generators ^¬ in particular.

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. When the mill 20 is, as Darge ^¬ represents in Figure 2, a ball ring mill, in which the brown coal is supplied through a material inlet 21 to a grinder 22nd The lignite is ground in the grinder 22 in a known manner and then exits laterally from the

Grinder 22 off. 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 μπι, sorted out and fed to the grinder 22 again. Sufficiently fine particles having a particle size of less than 500 μm form the desired brown coal dust and are conveyed through the material outlet 26 with the first conveying gas.

In 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 via port 27 with egg ^¬ ner temperature above the ignition temperature of the to be ground brown coal in the mill 20th 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 Venti ^¬ lator 2c. The composition of the drying gas results from the hot gases from the heating element 4, the vapor evaporated from the coal and possibly ^¬ occur the 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) in the Mate ^¬ rialauslass 26, if the desired particle size he ^{¬ was} enough, the brown coal is thus 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 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 conveyed in a filter 2b and there abgeschie ^¬ the. The separated lignite dust is further promoted to a dust washer 30 and rinsed there (step

103). Various embodiments of dust washing systems 30 are shown in more detail in FIGS. 3a-c. The dust washing system 30 can be realized as required by one of the systems shown in Figures 3a-c.

In the dust washer according to figure 3a reaches the Ge ^¬ mixture of drying gas and pulverized lignite through the input passage 31 in the dust washer 30, which as Belüftungskas- is executed. 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 with the Environment is connected. 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 ver ^¬ pushes namely the drying gas (or first conveying gas) from the interstices of 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. The result is the output of the

Staubwaschanlage 30 a mixture of brown coal dust and second conveying gas before. The dust washer 30 shown in FIG 3b is formed as a gas conveying channel ^¬ and works like the

Dust washing system 30 according to FIG. 3a. The mixture of Trock ^¬ voltage gas and lignite dust from entering via the inlet 31 into the dust washer 30. The dust washer 30 includes a flow channel 32 for the brown coal dust, which has a gas-permeable bottom 33rd Below the gas-permeable bottom 33 is a gas distribution chamber 35, which is connected to the gas source 3 (see FIG 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 in the flow channel 32nd 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 För ^¬ dergas at the output of the dust washing system 30. The dust washing system 30 in Figure 3c is designed as a pneumatic conveyor line. The mixture of drying gas and brown coal dust passes through a Einschleußorgan 31 ^λ 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. 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 brown coal dust-gas mixture, so that a promotion of

Brown coal dust is reached to the other end of the flow channel 32. By ^¬ be brought into the flow channel 32 gas, the drying gas (or first conveying gas) is diluted such that constitutes the second conveying gas. 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 compared with 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 brown coal dust has not changed by the conveying ^¬ tion and the purge substantially, so that the brown coal dust at a temperature of about 90 ° C upon entry into the silo 40th The brown coal dust is thus stored at a temperature of 90 ° C in the silo 40 (step 105).

The lignite dust arrives in the silo 40 together with the second delivery gas and is stored there. Since constantly second conveying gas together with the brown coal dust flows to the silo 40, it turns in the silo 40 with an atmosphere ei ^¬ nem oxygen content of less than or equal to 3 vol .-% and a water content less than or equal to 3 vol .-% a. In a corresponding atmosphere, the deposit of lignite dust at a temperature of up to 90 ° C is possible, in particular, no auto-ignition occurs. The lignite dust is deposited by gravity on the bottom 41 of the Siloinnenraums 42 and can be removed by a Publ ^¬ voltage 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 ^¬ see, with the gas can be discharged into the environment. The vent valve 44 is equipped with dust filters ^¬ tattet so that it is permeable only for 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 3 vol% has. Thus, a self ^¬ inflammation of the brown coal dust can be prevented in Siloinnenraum 42 permanently.

In Siloinnenraum 42 prevails over the environment, an overpressure. In this way 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.

For another coal is ^¬ Asked in Figures 1 to 5 system may need different operating parameters be ^¬ be exaggerated in order to ensure safe operation, Thus, the gas inlet temperature may, for example, at 500 ° C and the oxygen content in the first drying gas is less than ^or equal to 6% by volume.

Claims

claims

1. A process for the grinding drying and storage of lignite, comprising the steps of: a) grinding and drying (101) of brown coal to brown coal dust in a mill (20) with a low-oxygen drying gas and a Gaseintrittstem temperature above the ignition temperature of lignite b) promotion (102 ) of the ground and dried brown coal dust from the mill (20) with the help of egg ^¬ nes first feed 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) storing (105) the further transported lignite dust in a silo (40) at a temperature above 60 ° C and in an oxygen-poor, dry atmosphere.

2. The method according to claim 1, characterized in that the drying gas has an oxygen content of less than ^or equal to 12 vol .-%, preferably less than or equal to 6 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 or 500 ° C.

Method according to one of the preceding claims, characterized in that the temperature of the Braunkoh ^¬ lestaubes 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 brown coal dust has a mean product fineness of 40 to 100 μπι.

Method according to one of the preceding claims, characterized by that the first conveying gas Trock ^¬ drying gas.

9. The method according to any one of the preceding claims, character- ized in that when increasing the oxygen and / or water content in the silo (40), the silo (40) is rinsed with dry, oxygen-poor gas.

10. The method according to any one of the preceding claims, characterized in that the second conveying gas in ^¬ We sentlichen an inert gas, preferably nitrogen.

11. The method according to any one of the preceding claims, characterized in that in the silo (40) an overpressure relative to the environment is set.

12. 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) has a gas supply opening (27) for drying gas and having a material outlet (26) for Gemah ^¬ lenen and dried brown coal dust, and with the material outlet (26) of the mill (20) and the silo (40) connected to the dust washer (30) for SPC ^¬ development of the brown-coal dust with a dry, oxygen-depleted second conveying gas is provided.

13. Plant according to claim 12, characterized in that the silo (40) has a gas inlet opening (45) for dry and oxygen-poor gas and a ^{Regelsein ¬} direction is provided which the gas supply to the mill (20) and / or the silo ( 40) controls so that the operating parameters of at least one of claims 1 to 7 are met.

14. Plant according to claim 12 or 13, characterized marked, that the plant 1 is designed for carrying out the method according to one of claims 1 to 12.