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(11) | EP 1 393 872 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | METHOD FOR MILLING HARD ROCKS |
| (57) The method involves homogeneously mixing the sludges removed from the cutting machine
with water before reaching the hydrocyclone separating the minute grains. Said mixture
is carried out in an ejector (4) which receives the sludges through an inlet (7) and
pressurized water through the injector (5). In vertical position, it sends the mixture
jet into the interior of a body (1), wherein a partition wall (8) is placed inside
said body to support a bridge (9) defining an impact surface (10), which provokes
a first homogenization of the mixture together with subsequent impact of the fragmented
jet against the side wall of a body (1). The jet then goes through perimeter holes
(11) of the partition (8) into a lower chamber (13) in which the jets passing through
said holes impact a slanted plane (14) thereby generating a second homogenization
phase before reaching the outlet (15) defmed by the slanted plane (14) in the direction
of the tube (17) communicating the ejector-mixer with the hydrocyclone. |
OBJECT OF THE INVENTION
[0001] This invention refers to a method for milling hard rocks, in which the action of the cutting elements is facilitated by the incorporation to the cutting groove of minute grains functioning as an abradant, suspended in a sludge which acts not only as the support for the minute grains but also as a coolant in the cutting zone, whereas the aim of this procedure is to improve recovery of minute grains and particularly, to reduce the cost of such milling.
[0002] The invention also concerns an ejector - mixer device which is used to perform the aforementioned procedure.
BACKGROUND TO THE INVENTION
[0003] The process consists of eliminating continually or intermittently part of the water with residues or milling detritus and the lime with its derivatives where the case may be, without reaching the maximum concentration limit that allows to maintain the abradant in suspension, in other words, that the suspension of the abradant is largely due to the milling detritus. Therefore, the sludge processing method is the factor that most limits the possibility of advancement in milling, due to the high content of milling detritus in the sludge, and is the cause for the excessive consumption of energy, abradant and metal strips.
[0004] Patent no. ES 9300185/PCT 9400009, among others, described the possibility of milling with sludge containing low percentages of milling detritus where the supporting power is due to the presence of fine, soft powders that allow to reduce the total cost of the milling to a third and simultaneously treble the production, but this solution has not been applied yet due to the high investment needed for its application.
[0005] After that, as may be seen in Patent no. ES 9801558, there was a proposal for a method based on maintaining a high content of rock particles, pouring out part of the sludge containing the rock particles produced in the milling, whereas this latter operation may be performed on a continuous or frequent basis, as may the replacement of adequate amounts of water, lime and fine, soft materials that have been removed from the sludge circuit.
[0006] In this patent, the composition of the sludge entering the machine, excluding the minute grains, would be less than 66% for rock particles, over 28% for lime water and more than 6% for fine, soft materials; with the volume and according to the characteristics of the rock to be milled.
[0007] This patent described and claimed an installation to implement the aforementioned method, whereas the addition of the installation method allowed to improve the results in the cutting operations.
[0008] Nonetheless, the ratio between the volumes of water and fine, soft materials, in accordance with the aforementioned conditioning factors, should be approximately 3.5 to sustain the minute grains and allow the latter to flow through the grooves, so that the 21% of water corresponds to 6% of fine, soft materials, meaning that the maximum volume of milling detritus is limited to 73%, also in volume and excluding the minute grains.
[0009] Furthermore, the difficulty in recovering the minute grains from a sludge with the aforementioned proportions of fine, soft materials/ water, i.e. 3.5, in the hydrocyclones that are normally used in hard rock milling industries is so important that the loss of minute grains could be excessively increased.
DESCRIPTION OF THE INVENTION
[0010] In accordance with the procedure of this invention, the minute grains are recovered in the sludge that is continuously or intermittently separated from the circuit to recover the rock residues that are continuously produced in the milling process. More specifically, the invention provides for dilution of the sludge for evacuation and that it shall be re-mixed uniformly with water or lime water before passing through the hydrocyclone, whereas in this regard the amount of water used may go from one part water to three of sludge as far as more than ten parts water to one of sludge.
[0011] Moreover, the invention provides that the content of lime water in the sludge may oscillate between 21% and 28% and that the milling detritus content may also account for between 73% and 66%.
[0012] In order to achieve correct recovery of the minute grains, as explained before, the invention provides for a vertical ejector-mixer, with descending flow, in which the ejected jet impacts against a horizontal wall, either regular or irregular, made of wear-resistant material, such as virgin rubber or other such material, easily replaceable by fitting and sticking; a horizontal wall situated inside a chamber with a vertical axis, preferably cylindrical and also lined with wear-resistant material; whereas on the horizontal wall and outside the impact area, there are several holes through which jets of the product pass on their way to a lower chamber, in which they also impact on a tronco-conical or tronco-pyramidal surface with an inverted vertical axis, which is also wear-resistant and defines an outlet for the mixture, where there is a waterjet or pressurised drag system, which shall preferably function after the ejector-mixer stops, for several seconds, but which could also function simultaneously with the latter if necessary.
DESCRIPTION OF THE DRAWINGS
[0013] In order to complement the description and with the aim of allowing for a better understanding of the characteristics of this invention, according to an example of the preferred embodiment of same, a single map sheet is included, representing schematically in a single figure and in an illustrative and non-restrictive manner, a side elevation and diameter section of an ejector ― mixer according to the object of the present invention.
PREFERRED EMBODIMENT OF INVENTION
[0014] In the aforementioned figure, it may be observed that the ejector-mixer device that participates in the invention is formed by a cylindrical body (1), with a vertical axis, whose side and internal surface is covered by a layer (2) of wear-resistant material, for example, virgin rubber or other such material, whereas this body receives through its upper base (3) an ejector (4), also with a vertical axis, whereas a water injector (5) is placed coaxially opposite the latter, crossing a small chamber (6) also associated to the upper base (3) of the body (1) and to which the inlet (7) for sludge to be evacuated accesses radially.
[0015] Inside the body (1), there is a transversal partition (8) which constitutes the means of support and attachment for a bridge (9), also materialised in a piece of wear-resistant material, like the aforementioned, whereas such bridge defines a horizontal surface (10), which shall initially be flat, but in which there shall be irregularities due to the effect of the impact of the sludge on same, whereas this piece (9) shall preferably be fixed to the partition (8) with adhesive, allowing for replacement.
[0016] In the perimeter zone of the partition (8), outside the body (9), there is a circumferential line of holes (11) communicating the upper chamber (12) defined in the body (1) by the intermediate partition (8), with the lower chamber (13), the lower end of which is a tronco-conical surface (14), also with a vertical axis, defining the outlet hole (15) established in the lower base (16) of the body (1) and which establishes communication between the ejector-mixer itself and the outlet pipe (17) for the mixture.
[0017] A water injector (18) is situated on the closed end (19) of the tube (17), at the lower level, to drag the minute grains that might be deposited in the tube (17) and ensure their entry in the hydrocyclone in which the aforementioned tube enters (17), not represented in the figure.
[0019] The sludge enters same through the pipe (7), reaching the small input chamber (6) at an appropriate, properly regulated flow, from which it is displaced towards the ejector (4) on which the water jet generated by the injector (5) acts parallel and simultaneously, so that there is a jet that impacts at high speed on the surface (10) of the bridge (9) from which, by the effect of the slope in its route determined by the downwardly diverging configuration of the ejector (4), the mixture suffers a sudden change in its route and is directed at the lining (2) of the side wall of the body (1), thereby achieving a high degree of agitation inside the chamber (12), after which the mixture is passed to the lower chamber (13) through the holes (11), where it impacts on the slanted plane (14), producing a new agitation with the consequent increase in the homogeneity in said chamber (13), from where the mixture finally accesses, through the outlet (15), the evacuation pipe (17) towards the hydrocyclone.
1. A procedure for milling hard rocks with minute grains and supporting sludge, in which
said sludge is composed by more than 6% volume of fine, soft materials purified on
a continuous, frequent basis, whereas a flow of sludge is evacuated, from which only
the minute grains are recovered, characterised by the fact that the flow that is evacuated is homogeneously mixed with water or lime
water before passing through the hydrocyclone that separates the minute grains and
also characterised by the fact that the content of water or lime water in the sludge may be between 21
% and 28% of the volume and that the content of milling detritus may in turn account
for between 73% and 66% of the volume.
2. An ejector-mixer device to implement the procedure described in the 1st claim, characterised by the fact that it is formed by a body (1), preferably cylindrical in shape, with a
vertical axis, in whose upper base (3) there is an ejector (4), also with a vertical
axis, accessed by the sludge to be evacuated through a side inlet (7) and the pressurised
water through an axial injector (5), whereas inside the body (1) there is an intermediate
compartmented partition wall (8), defining a horizontal front (10) upon which the
sludge-water mixture should impact, outside which there is a circumferential line
of holes (11) to pass the mixture from the chamber (12) above said partition (8) to
a lower chamber (13), the lower end of which is a slanted plane (14), preferably inverted
and of a tronco-conical shape, defining the outlet (15), towards the pipe (17) communicating
with the hydrocyclone used to recover the minute grains.
3. An ejector-mixer device, according to the 2nd claim, characterised by the fact that the body (1) contains a side and internal lining (2) made of wear-resistant
material, such as virgin rubber or other such material, whereas the partition (8)
incorporates on its central area a piece (9), made of a material of similar characteristics,
defining the front (10) for impact of the mixture jet, whereas the upper chamber (12)
acted as the homogenisation chamber, where the jet of the mixture, after impacting
on the surface (10) and thanks to the downwardly divergent configuration of the lower
area of the ejector (4), forms an elbow in its route towards the lining (2) of the
side wall of the body (1), before finally reaching the holes (11) to pass through
to the lower chamber (13), where there is another homogenisation phase when the jets
of the mixture from the holes (11) impact on the slanted plane (14).
4. An ejector-mixer device, according to the 2nd and 3rd claims, characterised by the fact that the pipe (17) communicating the ejector-mixer with the hydrocyclone
has, on its closed end opposite the latter, a water injector, situated at the lower
level, to drag the minute grains that may be deposited on the lower part of said pipe
(17).
5. An ejector-mixer device, according to the 2nd, 3rd and 4th claims, characterised by the fact that the ejector-mixer is situated beside the inlet to the hydrocyclone
for recovery of the minute grains.