DE1266618B - Process for the regulation of the fine grinding of regrind of different grindability with constant task amount - Google Patents

Description

Method for controlling the fine grinding of different grist Grindability with constant task amount The invention relates to a method for Regulation for the fine grinding of regrind of different grindability, whereby the Grist first a high-speed mill, z. B. a beater mill is supplied and then a tube mill happens while the discharges of both grinding units are one Sifter are fed, which delivers the grits directly to the tube mill.

A method has become known in which the grist in a Mill is crushed, e.g. B. in a drum mill with autogenous grinding. That Control of the degree of fineness of the ground product should depend on the physical properties of the grist, which is essentially constant Quantity and piece size is fed, in the sense that controlled in the case of coarser the speed of rotation is reduced as the grinding product becomes finer and the grinding product becomes finer is increased. The fineness of the ground product should be derived from the load on the drive motor a classifier downstream of the mill can be determined.

But it is well known that it is very difficult to measure the grinding performance of a To regulate a pipe or a drum mill, since such a regulation works too sluggishly, to prevent the mill from filling up in good time. Before the sifter If too much or too little fine grain is displayed, more grist can be added by adding more than the mill can normally process. According to what has become known The mill should operate at a reduced speed when it receives harder material work. The reduced speed, however, inevitably increases the grinding capacity reduced, and since the grist continues in the same amount and size is to be fed, so this can if the feed harder goods over a longer time unit happens, also lead to the grinder filling up.

According to another method, it is known to use mills with rotating To control impact tools so that the speed of the mill is dependent on the Type of the goods to be given, in the sense that when a good is given up, it is higher Breaking strength the speed is increased. However, this change in performance is due increased wear limits. In principle, however, it is possible with a High-speed mill Grist of very different properties on tube mill fineness to grind.

There are numerous developments in order to circumvent these difficulties known. One is with a hammer mill-tube mill combination the loading of the hammer mill depending on the grindability of the material to control, d. H. to give up less in the event of difficult-to-grind material, whereby the grindability is determined from measured values from the hammer mill. The discharge of the hammer mill is then equal to the respective optimal feed quantity of the tube mill. In general however, the aggregates of such mill combinations work independently of one another, whereby the hammer mill creates a supply and a bunker is interposed.

With another hammer mill-tube mill combination you have the grinding stages a viewing step downstream. This is the fine fraction released by the classifier less, the coarse grain fraction delivered to the tube mill increases. Tube mills but are known to not vary in performance during operation. By a If the speed of tube mills changes, the performance inevitably drops because tube mills on their optimal grinding performance by selecting the pipe diameter, the speed, the type and quantity of the ball filling, the formation of the armor, etc. are designed. It is only possible to change the performance by controlling the material supply reach.

The invention is based on the object of providing constant amounts of grist to be fed to the grinding system and the same quantities continuously as fine ground material Gain uniform grain, while largely protecting the beater mill and optimal utilization of the tube mill capacity.

According to the invention this object is achieved in that with constant Task amount the amount of fine material discharged from the classification stage to the Grinding capacity of the pre-grinding stage in the sense that acts when losing weight The grinding capacity increases with the amount of fines and decreases as the amount of fines increases will.

The finished product discharge of the classifier will always drop if shares material that is difficult to grind pass through the mill system. In parallel with the reduction of the discharge of the finished product there will be an increase in the proportion of grits that are fed to the tube mill. If one now increases the grinding capacity according to the invention the beater mill, e.g. B. by increasing the stroke rate per unit of time, so will the portion of the grit from the classifier will decrease and the fine portion will reach the target value approach. As soon as the beater mill receives easily grindable material from the loading, If the fine fraction will exceed the setpoint, the grinding capacity will then be reduced the beater mill decreased.

Due to the occasional heavy use of the beater mill, wear and tear can be kept within tolerable limits.

The beater mill is controlled depending on the amount of fines being discharged by control devices known per se, the volumetric or gravimetric Can take measured values into account. The control intervention itself can, as mentioned, through Increase in the impact sequence and possibly by adjusting the grinding grates.

The adaptation of the high-speed mill to the different grist takes place very quickly, as the material is in both the beater mill and the classifier happened very quickly.

The invention is explained on the basis of a schematic representation. It shows a beater mill 1 and a tube mill 2. The beater mill is supplied with the ground material from a bunker 3 via an allocation device 4 and flows in crushed form to a height conveyor, e.g. B. a bucket elevator 5, which passes the material on to a sifter 6, via which the finished material is discharged through the fine material discharge 7 "via a belt scale 10, while the coarse fraction is passed on via a feed 8 to the tube mill 2, which feeds its grist to the elevator 5. The weight of the fines discharge is reported to a controller 9, which controls the fine grinding capacity of the beater mill 1 accordingly.

Claims (2)

Claims: 1. A method for regulating a pre-grinding and Fine grinding existing grinding process, especially for different grist Grindability, in which the pre-grinding stage and the fine grinding stage are connected in series are that their outlets are fed to a common classification stage and the The semolina fraction precipitated here flows into the fine grinding stage, characterized in that; that if the feed quantity remains the same, the quantity discharged from the classifying stage Fine material serves as a control variable that affects the grinding capacity of the pre-grinding stage in the Sense has the effect that with decreasing amount of fines, the grinding capacity increases and with increasing amount of fines is reduced. 2. Plant for carrying out the control method according to claim 1, consisting of .einer beater mill and a downstream tube mill, the outlets of which are connected to a common classifier, the semolina outlet of which opens into the tube mill, characterized in that the fines outlet (7) of the classifier (6 ) is provided with a belt scale (10) which is connected to an adjusting device for the rotor speed of the beater mill (1) via a controller (9). Documents considered: German Patent No. 1 151719; German Auslegeschriften Nos. 1161111, 1088 327; German utility model No. 1746 304.