DE3537049A1 - METHOD AND SYSTEM FOR THE PRODUCTION OF SS-HALBHYDRATE PLASTER - Google Patents

Description

The invention relates to a method accordingly the preamble of claim 1 and an was able to carry out this procedure.

To date, β- hemihydrate gypsum has generally been produced in two successive process stages. The raw material is crushed in the first process stage, while in the second process stage the ground raw material is burned by means of a hot gas stream.

The burning in the second stage of the process follows, for example, in a rotary kiln (CH-PS 4 45 359), in one of several behind interconnected cyclones existing Zyk lon-burner (DE-AS 19 40 007) or in one DC floating gas combustion plant (DE-AS 27 05 463).

For the production of stucco is also a Method known (DE-PS 6 38 800), in which the Raw material in one of was during grinding flushed through the drum mill to the highest level is heated to at least 180 ° C. After sighting the of the grist in the air stream the coarser parts in a shaft except for about Heated at 800 ° C and then regrind added to the raw material again.  

A major disadvantage of the above schil the most known method consists in the the two-step mode of operation required high positional effort.

The invention is therefore based on the object a method in the preamble of claim 1 assumed type so that there is a significantly lower plant engineering effort than the known methods required.

This object is inventively by the Drawing feature of claim 1 solved.

Appropriate configurations of the invention are Subject of the subclaims.

An autogenous mill is a short tube mill with large diameter; the length / diameter The ratio is expediently between 0.25 and 0.4.

The crushing of the ground material in one Autogenous mill is mainly done by the Impact of the ground material. To achieve a The autogenous mill at the large head Provided on the inside with lifting and longitudinal strips be that raise the regrind as high as possible.

In the context of the invention, the autogenous mill up to 6 vol .-% of the filling grinding media (at steel balls, for example) to contain the autogenous  Support crushing process.

So far, the autogenous mill has mainly been an auto grinding in ore processing and for Mill drying of cement raw material used. The oxyacetylene mill has always been used Drying the ground material, but not to one further heat treatment used.

In the extensive experiments on which the invention is based, it has now surprisingly been found that, due to the marked internal circulation of the millbase in the autogenous mill, the residence time of the millbase in the autogenous mill is sufficient for the chemical conversion of the raw material (dihydrate) to the β- hemihydrate gypsum .

It may be useful through suitable design measures (at for example by a smooth training of the Inside the end walls of the autogenous mill) Dwell time of the ground material in the mill prolong.

Since the Zer reduction and burning of the raw material takes place simultaneously in a single unit, results in comparison to known methods a significant reduction in plant technology African effort.  

The temperature of the autogenous mill Hot gas flow is between according to the invention 200 and 600 ° C.

The autogenous mill can process the raw material in one Grain size between 0 and 300 mm.

Whether and if so which grinding media additive selected depends mainly on the desired grain size of the finished product and / or of the desired one Throughput.

The sufficiently shredded and burned good is released from the autogen by the hot gas flow carried out and fed to a sifter, the coarse material accumulating in the classifier again fed to the autogenous mill while the Fines are separated in a separator.

At least a part of the leave the separator the hot gases after filtering and heating expediently fed back to the autogenous mill. In this way, the thermal engineering we efficiency of the process improved and the Ab gas volume significantly reduced.

It is of course also possible to have a part of the hot gases leaving the separator Filtering after heating up the car again to feed the mill. In this case it is on less technical effort for filtering,  but there is a blower in the unfiltered gas stream required that some wear under lies.

An embodiment of a plant for through implementation of the method according to the invention is in the drawing illustrates.

The system shown contains an autogenous mill 1 , an air flow classifier 2 , a separator 3 designed as a cyclone, a filter 4 , a burner 6 arranged at the upper end of a shaft 5 , a good feed device 7 , a chute 8 , a bucket elevator 9 and a Blower 10 .

The system parts mentioned are in the from Drawing evident way with lines connected to each other.

The system works as follows:

The raw material is fed via the feed device 7 and the chute 8 of the autogenous mill 1 , which is driven by an unillustrated Antriebsein direction.

In the provided with the burner 6 , designed as a combustion chamber Ver 5 hot gases are generated at a temperature of 200 to 600 ° C, which get together with the raw material via the chute 8 in the autogenous mill 1 .

In the autogenous mill 1 , the raw material is crushed to the desired fineness. The fineness of the finished product can be seen - from the structural design of the autogenous mill - by adding a certain amount of grinding media, by the speed of the hot gas flow passing through the autogenous mill and / or by the speed of the mill.

The chemical conversion of the dihydrate into β- hemihydrate takes place simultaneously with the comminution of the raw material. The heat energy required for this is supplied by the hot gas flow, which leads the sufficiently shredded and sufficiently fired finished goods to the air flow classifier 2 . The coarse material obtained here is fed again to the autogenous mill 1 via the bucket elevator 9 , while the fine material is separated in the separator 3 .

The hot gases leaving the separator 3 are dedusted in the filter 4 . Some of the filtered gases are fed back to the shaft 5 and heated again by the burner 6 . The unnecessary rest of the filtered gases are released into the atmosphere.

Claims (9)

1. A process for the production of β- hemihydrate gypsum, the raw material being crushed and burned by means of a hot gas stream, characterized in that the raw material is crushed while being circulated in an oxy-fuel mill ( 1 ) and is simultaneously burned by the hot gas stream passing through the mill . 2. The method according to claim 1, characterized in that the autogenous mill ( 1 ) contains up to 6% of the filling grinding media. 3. The method according to claim 1, characterized in that the temperature of the auto genmühle ( 1 ) supplied hot gas stream is between 200 and 600 ° C. 4. The method according to claim 1, characterized in that the autogenous mill ( 1 ) on a given raw material has a grain size between 0 and 300 mm. 5. The method according to claim 1, characterized in that the sufficiently comminuted and burned material is discharged from the oxy-fuel mill ( 1 ) by the hot gas stream and fed to a classifier ( 2 ), the coarse material accumulating in the classifier being fed back to the oxy-fuel mill ( 1 ) is while the fines are separated in a separator ( 3 ). 6. The method according to claim 5, characterized in that at least a part of the separator ( 3 ) leaving hot gases after filtering and heating back to the autogenous mill ( 1 ). 7. Plant for performing the method according to claim 1, characterized by an autogenous mill ( 1 ) which has a length / diameter ratio between 0.25 and 0.4. 8. Plant according to claim 7, characterized in that the end walls of the autogenous mill ( 1 ) are smooth on the inside. 9. Plant according to claim 7, characterized in that the end walls of the autogenous mill ( 1 ) are profiled on the inside.