EP1028157A1 - Process for the treatment and conditioning of rolling oils - Google Patents

Abstract

Process for working up and conditioning rolling oil comprises removing dirt and abrasive particles by filtering and with a regulated addition of filter auxiliary aids, and adjusting the electrical conductivity in the purified oil. A flocculating agent is used as the auxiliary aid and is added depending on the residual dirt remaining in the filtrate. A small amount of conductivity caused by the remaining residual dirt remains in the filtrate.

Description

Procedures for the preparation and conditioning of in circulation driven rolling oil, in particular rolling oil for aluminum foil rolling mills, in which from the returned rolling oil by filtration and under controlled addition of filter aids removes dirt and abrasion particles and the electrostatic charge in the cleaned rolling oil preventing conductivity is set.

When rolling metal foils, rolling oil is used for cooling and lubrication, which normally consists of a sufficiently temperature-resistant Mineral oil fraction exists. It is to reduce rolling oil consumption It is customary to circulate the rolling oil and continuously in sufficient quantities Clean dimensions and condition for re-use. The rolling oil circulated essentially contains impurities metallic abrasion particles of the rolling stock and their oxidation products. Cleaning is usually done in precoat filters, e.g. B. in filter presses, in which the abrasion and dirt particles as far as possible from the rolling oil be removed.

To improve the filtering process and to ensure that the rolling oil is as pure as possible It is common to get the rolling oil as a filter aid diatomaceous earth before filtering or add bleaching earth, through which the degree of separation of the used Precoat filter is significantly improved. When using conventional Filter aids such. B. Diatomaceous earth and bleaching earth occur with every filter cycle in addition to a basic wash-up, a replenishment of the auxiliary materials. In the porous volume of the filter aids and in their spaces Dirt particles are stored and clogged in the course of a filter cycle gradually the free pores and channels. Since it is unusual during one loosening or backwashing the filter cake during the running cycle decreases the relative porosity of the filter cake, combined with the fact that with the volume flow kept constant, on the one hand, the differential pressure above the filter cake increases, while on the other hand the clarity increases, the filtrate consequently getting cleaner.

It is also known in the prior art to add a filter aid use, which contains 50% cellulose fibers and 50% citric acid. This Filter aid is quite effective, but its mode of action is difficult to find check. The filter aid is in the form of a filter cake on the Filter fleece washed ashore. Since primarily chemical Effects between the acid and the impurities are playing plays the dwell time of the components involved plays a major role. This is relative in short, the mechanism of action of oil cleaning is therefore relatively sluggish. Consequently For a high conversion rate, a lot of acid has to be introduced into the filter cake become (overdose).

For improved separation of very fine particles, it is also known that Add a flocculant to the rolling oil before filtration as a filter aid, through which the very fine particles are agglomerated into larger aggregates, so that they are better retained in the precoat filter.

A significant problem in the preparation and use of such Rolling oil results from the fact that the rolling oil in its initial state and has practically no electrical conductivity even in the cleaned state, i.e. is a good insulator so that there is a risk of electrostatic charging exists, the discharge sparks of fire, explosion or deflagration in the rolling mill and possibly also in the processing plants can.

In order to avoid electrostatic charging, it is known to in the rolling oil Add sufficient amounts of conductivity additives to the conductivity of the rolling oil so far that the above-mentioned electrical Can not develop charge potentials. These are conductivity additives however ecologically and health-wise, so that a flat rate preventive admixture of these agents high environmental pollution and caused difficulties in disposal.

It is therefore an object of the invention, the method of the aforementioned Kind in such a way that on the harmful conductivity additives can be dispensed with, without the electrical charge resulting dangers increase.

To achieve this object, the invention proposes that a filter aid Flocculant is used, the addition amounts depending on the residual contamination remaining in the filtrate should be regulated in such a way that Filtrate a given, through the remaining residual pollution caused minimum conductivity is maintained.

The invention is based on the consideration that one has sufficient conductivity of the rolling oil not only through the addition of conductivity additives can achieve, but also in that in the filtrate targeted a sufficient high residual pollution is maintained. The one in the process according to the invention after filtration in the rolling oil abrasion and Dirt particles can act just like a conductivity additive.

On the one hand, the residual pollution is set so high that the electrostatic Charging of the rolling oil is prevented, and on the other hand so low set that stains on the rolling stock are avoided.

Because in the method according to the invention not as a filter aid Diatomaceous earth or bleaching earth can be used, but is a flocculant it is possible to determine the dirt concentration in the filtrate if necessary - d. H. if the Regulation it requires - also to increase in a targeted manner, namely in that correspondingly less flocculant is added. In contrast, can one when using diatomaceous earth or bleaching earth as a filter aid Reduce dirt concentration in the filtrate only without changing the filter but do not increase again. The same could be said for the above Use of citric acid as a filter aid for the function required overdosing in the filter cake does not degrade quickly enough become. Only the use of flocculants as a filter aid enables that is, the targeted setting of the residual pollution aimed at according to the invention.

In addition to the increase in electrical conductivity explained above, the in the residual oil that remains in the target oil and has been set in a targeted manner with the fact that the handle between the rollers and the rolling stock in the rolling mill getting better. So not only the electrical, but also improved the mechanical properties of the rolling oil.

Finally, the total consumption is also in the method according to the invention of filter aids - here flocculants - significantly less than those of the after the state of the art usual methods, because consciously to a complete Purity of the filtrate is dispensed with.

The conductivity in the filtrate is expediently set to between κ 1 = 50 pS / m and κ 2nd = 5000 pS / m , but preferably between κ 3rd = 100 pS / m to κ 4th = 1000 pS / m set. It has been found that at these values, electrostatic charges on the rolling oil and fires, explosions or deflagrations caused thereby are reliably avoided. In this conductivity range, on the other hand, the residual contamination is so low that the rolling process is not disturbed by the residual contamination and the grip between the roller surfaces and the rolling stock is optimal.

A dicarboxylic acid with the general formula is preferred as the flocculant HOOC-A-COOH used, wherein A is a straight and branched chain of 5 to 15 carbon atoms or phenylene. With such a flocculant, the method according to the invention works optimally. Alternatively, other flocculants can of course also be used for the process according to the invention.

An embodiment of the invention is described below with reference to the drawing explained in the schematic of an aluminum foil rolling mill with connected Rolling oil preparation is shown.

In the drawing, the rolling mill is shown only schematically with the Reference number 1 denotes. The rolling mill 1 is circulated Rolled oil cooled and lubricated. The rolling oil circuit is indicated by arrows 2 designated.

The rolling oil flowing out of the rolling mill 1 and loaded with abrasion particles and dirt is fed via a pipeline 2 to a dirty oil chamber 3. On the way, a flocculant is added to the rolling oil via a metering pump 4 from a storage container 5. The rolling oil enriched with flocculant remains in the dirty oil chamber 3 for about 5 minutes and then passes through a filter system 6, usually a precoat filter. In this filter system 6 the coarser abrasion and dirt particles as well as the flakes formed by the flocculant are separated and removed with the filter cake (see arrow 7). The filtrate flowing out of the filter system 6 passes through a measuring chamber 8, in which the residual contamination and / or the electrical conductivity of the rolling oil proportional to it are measured. On the basis of the measurement data obtained in the measurement chamber 8, the metering pump 4 is controlled in such a way that the measured electrical conductivity in the filtrate is between values κ 1 = 50 pS / m and κ 2nd = 5000 pS / m , preferably between κ 3rd = 100 pS / m and κ 4th = 1000 pS / m settles. The rolling oil thus set to maintain residual contamination in a targeted manner is then returned to the rolling mill 1.

With the electrical conductivity indicated above, the formation of ignitable electrostatic potentials in the entire system reliably avoided. It is also proportional to these conductivity values Residual contamination low enough that the rolling process due to this contamination is not adversely affected. On the contrary, through the remaining one Residual contamination becomes the handle between the rollers of the rolling mill and the rolling stock improves, which increases the quality of the rolling process affects.

Claims (3)

Process for the preparation and conditioning of circulating rolling oil, in particular rolling oil from aluminum foil rolling mills, in which dirt and abrasion particles are removed from the returned rolling oil by filtration and with the controlled supply of filter aids, and in the cleaned rolling oil an electrical conductivity preventing electrostatic charging is set becomes,
characterized,
that a flocculant is used as the filter aid, the addition amounts of which are regulated in dependence on the residual contamination remaining in the filtrate in such a way that a predetermined minimum conductivity caused by the remaining residual contamination is retained in the filtrate. A method according to claim 1, characterized in that a conductivity range of κ 1 = 50 pS / m to κ 2nd = 5000 pS / m , preferably from κ 3rd = 100 pS / m to κ 4th = 1000 pS / m is set. Process according to claims 1 and 2, characterized in that a dicarboxylic acid with the general formula is used as flocculant HOOC-A-COOH is used, wherein A is a straight and branched chain with 5 to 15 carbon atoms or phenylene.

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