Method and apparatus for continuously ensuring sufficient quality of green pellets

Abstract

A method for controlling pellet quality in iron ore production includes the steps of mixing water, binder and iron ore particles in at least one mixer to form a mixture (step (i)) and pelletizing the mixture into green pellets (step (ii)). Between step (i) and step (ii), a part of the mixture is taken in a sampling operation, formed into a test specimen and subjected to a test.

Claims

1. A method for controlling pellet quality in iron ore production, comprising the steps of: (i) mixing water, binder and iron ore particles in at least one mixer to form a mixture, and (ii) pelletizing/balling the mixture into green pellets, wherein between step (i) and step (ii) a part of the mixture is taken in a sampling operation, formed by compressing the part of the mixture into a test specimen and subjected to a pressure test, wherein step (i) is adjusted based on the results of the pressure test by adjusting at least one of: (a) a quantity of the added binder; or (b) a quantity of the added water, wherein the results of the pressure test include a plasticity of the test specimen and the method further comprises: decreasing or increasing the quantity of the binder being added into step (i) based on whether the plasticity of the test specimen is respectively above or below a threshold plasticity; or increasing or decreasing the quantity of the water being added into step (i) based on whether the plasticity of the test specimen is respectively above or below the threshold plasticity.

2. The method according to claim 1, wherein at least one storage container is connected downstream of the sampling operation.

3. The method according to claim 1, wherein a predetermined matrix is used to adjust the quantity of the binder and/or water based on the results of the pressure test.

4. The method according to claim 1, wherein the test specimen is a circular cylinder or a prism.

5. The method according to claim 1, wherein the method is carried out continuously.

6. The method according to claim 1, wherein the green pellets are subsequently burnt.

Description

(1) It shows:

(2) FIG. 1 shows a schematic representation of a plant according to the invention.

(3) The iron ore is crushed in a grinding section with feed bins 12 and transported via an integrated continuous conveyor via line 11 into a grinding mill 12, via another continuous conveyor 13, line 14 and continuous conveyor 15 finally into a material sieving device 16. From there it is transported via line 17 to a collecting bin 20.

(4) From there it is conveyed via an integrated first continuous conveyor to a second continuous conveyor 22 and from there via line 23 to a mixer 24. Mixer 24 also transfers water and/or binder from storage device 21 in its integrated continuous conveyor to continuous conveyor 22 and this material is also fed into mixer 24 via line 23.

(5) In accordance with the invention, a sampling unit 30 is situated in line 25. A part of the material flow is taken by this sampling unit 30 and fed to a forming device 32 via line 31. The test specimens produced there finally reach a test device 34 via line 33. The aforementioned steps 30 to 34 can be situated in one housing/apparatus or realized as single units handing material over. The tested material gets spilled back on the conveyor belt 26 and follows the normal material flow.

(6) Via line 26 the mixture is fed onto a continuous conveyor 27 and then introduced into at least one storage tank 28, which is shown here as two parallel connected containers. The material then passes from at least one storage tank 28 to the pelletizing disc 40, which is equipped with successively connected continuous conveyors 41, 42, 43. These convey the material onto a roller screen 44, where undersized material can be sorted out and fed via line 45 into line 23 and thus to the mixer 24.

(7) From the roller screen 44, the material is then transported to a travelling grate 50 which is not described in detail.

EXAMPLE

(8) A test sample of 300 g of mixed material is taken right after the mixing process. In the lab this means a certain amount is taken from the mixing batch, in the industrial set-up the material can be collected from the transport conveyor right after the mixer by a sampling device.

(9) The collected material is loosely filled into a cylindrical female die of a certain diameter (between 20 and 100 mm) and afterwards compressed with a male die. Manual compression of the specimen in the lab is done by a ram apparatus with three consecutive ram strokes with a weight of 6 kg. The automated compression in case of the industrial monitoring system can be performed pneumatic piston with a certain compacting pressure, typically in the range of several bars.

(10) The test specimen then is moved out of the cylindrical die and transported to a pressure test device. The stamp then is moved down vertically with a constant feeder motion (0.002 to 5 mm/sec) on the pressing and the corresponding force and deformation gets measured.

(11) The plasticity (measured in [μm/daN]) of the pressing can be withdrawn from the recorded force-distance-relationship. The relevant part of the measured curve forms a linear relationship between 10 and 90% of the distance relative to the breakage force of the test specimen, which can be detected by a decreasing testing force.

(12) Besides plasticity, compressibility and compression strength can be extracted from the measured data. After the actual test procedure the material is spilled out by the automatic test sampler and a new testing process can be initiated.

REFERENCE NUMBERS

(13) 10 grinding plant 11 line 12 grinding mill 13 continuous conveyor 14 line 15 continuous conveyor 16 collecting device 17 line 20 collecting device 21 line 22 continuous conveyor 23 line 24 mixer 25 line 26 line 27 continuous conveyor 28 storage tank 31 line 32 forming device 33 line 34 test device 40 pelletizing plate 41 continuous conveyor 42 continuous conveyor 43 continuous conveyor 44 roller screen 50 travelling grate