DE19612187C2 - Process for crushing and drying brown coal - Google Patents

Description

The invention relates to a method for comminution and drying of brown coal, in which the brown coal has at least two Comminution steps are carried out and in an indirect way heated fluidized bed dryer is dried, at least one first comminution step takes place before the fluidized bed drying and from the fluidized bed drying vapors via a dust separator be subtracted as the carrier gas for the subsequent Crushing and sifting are used, and being the dried lignite in the second shredder is crushed and subsequently a sifting into a rough and Fine fraction takes place.

The so-called WTA drying process removes the dust Vapors compressed and for indirect heating of the Fluid bed dryer used.

In the so-called DWT process, the fluidized bed dryer heated with steam and the vapors condensed and the water removed Heat used for other purposes.

In both methods, there is no screening after the first Comminution step so that the entire regrind, i.e. H. that too Fine material, is subjected to a second comminution step, so that the downstream shredding device is unnecessarily large must be interpreted.

DD 224 648 A1 describes a method for drying and crushing known from lignite, the lignite in an indirect heated fluidized bed dryer is dried. The proposed Whirling process requires the coal to be comminuted ahead. Then the dried coal in a second Crushed the mill in such a way that a fuel dust is created, which one Furnace is fed. The coarser parts from this second The grinder is separated and again to the suction side of the second grinder fed, for this purpose vapors are fed via a line.  

If this second mill is designed as a fan mill, be those required to maintain the inert gas atmosphere Vapors inevitably fed into the grinding and classifying process.

An alternative promotion of the vapors is available according to DE-PS 830 375 through the use of a fan that drives the vapors the mill draws in through a classifier and a dust separator and in a closed cycle back to the mill.

It is the object of the present invention to provide a method for Crushing and drying lignite of the generic type to be specified at which the grinding effort is reduced.

The object is achieved in that the comminuted material subsequently by means of vapors of the fluidized bed drying above the Fluidized bed is supplied and that above the fluidized bed Sifting of the comminuted material is carried out.

Because the fluidized bed dryer with an atmosphere of light overheated steam works, the brothers can without Safety problems are used to sift the regrind. The through the sighting fines can Fluidized bed drying or the dust collector are fed, using the brothers themselves.

The only subclaim is for a preferred one Process management to improve the separation of coal dust.

The advantageous procedure of the method according to the invention will now be explained in more detail with reference to the single figure. The figure shows:

A procedure in which without a separate Sifter the fluid bed drying system itself as a sifter is used.

In addition to feeding raw lignite RK into a first shredding device 2 , the method according to the single figure shows a second shredding device 25 which is not followed by a sifter. The regrind discharged from the comminution device 25 by means of the vapor stream B supplied via line 26 is blown directly into the fluidized bed dryer via a line 32 . The ground material is preferably blown in above the fluidized bed which is established in the fluidized bed dryer, the upper side O of which is shown schematically in the single figure.

Here, a separation of the fine material is achieved, which is fed to the vapor electrostatic precipitator 14 via line 13 . The coarse material sinks into the fluidized bed and is again conveyed to the extraction device 12 as dried brown coal GK.

It may be expedient for a baffle plate 33 to be arranged in the free space above the fluidized bed, onto which the gas-solid mixture stream emerging from line 32 impinges. It would also be conceivable to arrange a turntable here.

However, the appropriate measures are only necessary if by introducing the recycle gas solids mixture stream into the forming in the dryer and on the trigger to Vapor electrostatic precipitators aligned with the main vapor flow HB Desired classifying effect cannot be achieved.

It should also be pointed out that each teat of the fluidized bed dryer 9 or the vapor electrostatic precipitator 14 must of course be assigned a withdrawal device.

Claims (2)

1. A process for comminuting and drying lignite, in which the lignite is subjected to at least two comminution steps in two comminution devices and is dried in an indirectly heated fluidized bed dryer, at least one first comminution step taking place before the fluidized bed drying and vapors being withdrawn from the fluidized bed drying via a dust separator , which are used as carrier gas for the subsequent comminution and classification, and wherein the dried lignite (GK) is comminuted in the second comminution device ( 25 ) and a classification into coarse and fine fractions is subsequently carried out, characterized in that the comminution material subsequently uses Vapor (B) is fed to the fluidized bed drying ( 9 ) above the fluidized bed and that the comminution material is sighted above the fluidized bed. 2. The method according to claim 1, characterized in that internals are provided above the fluidized bed in the inflow region of the mixture of the comminuted material for drying the fluidized bed and vapors (B) in the fluidized bed drying ( 9 ) to improve the coal dust separation.