DE10337105A1 - Method for disinfecting water containing contaminated coolant and lubrication materials has them subjected to electromagnetic radiation - Google Patents

Abstract

The coolants used in the machine tool industry are recirculated and cleaned of particles (8) but may then contain germs which are removed by circulation from the reservoir (1) through a heat exchanger (2) and a microwave oven (3) by a pump (7) and returned to the system (4) for use.

Description

Technical application

The The invention relates to a method for treating contaminated, aqueous cooling and lubricants, in which the cooling and lubricant or a fraction derived therefrom forms a liquid medium, which is heated to reduce contained germs. The invention also relates to a device for carrying out the method.

Cold and Lubricants are used inter alia in machining (e.g. Turning, milling, grinding), the metal forming technique (e.g., forging), the metal forming technique (e.g., bending, pulling, rolling, stretching, pressing) or other areas used in industrial manufacturing processes where cooling and lubricating properties of auxiliaries are required. at this use is the cooling and lubricants during the use phase with solids or liquids, such as abrasion, cutting additives, abrasives or foreign oils, and contaminated with germs. Among aqueous coolants and lubricants are used in the present Description including water-soluble, water-miscible, water-mixed or other cooling and lubricant mixtures understood, the water in the range> 5% to nearly 100% include. The following is a collective term for such contaminated, water-containing substances the term "water-miscible Cooling lubricants "or short" KSS "used.

The water-miscible cooling lubricants most frequently used in industry are complex emulsions based on KSS concentrates, which are mixed and emulsified in water in the ratio of about 1:10 to 1:25. The following table shows an example of some specific substance classes which may be contained in water-miscible cooling lubricants and indicates the maximum concentration of the substance classes contained in the commercially available concentrates.

It It can be seen that KSS concentrates are complex. In addition to emulsifiers, the finely dispersed oil or water droplets in stabilize the emulsion, the formulations contain corrosion inhibitors, Cutting active additives like extreme pressure additives, solubilizers and, in the case of preconserved concentrates, also biocides.

coolants can next to the liquid Components also solid substances in the form of very fine particles, chips and abrasives contain. These particles are used in many applications machined material (e.g., metal, carbon) and the machining Material (e.g., silicon carbide cutting or abrasive particles, Diamond, carbide, etc.) dominates. In addition, foreign oils can be found in the coolant and change the properties of the KSS. Especially problematic However, it is that in the KSS germs due to microorganisms can come, v. a. by aerobic, anaerobic and / or sporulating Bacteria as well as yeasts and molds. By the contamination of KSS can their usage properties change massively. Furthermore, it may too health problems come to the employees of the farms who work with germinated KSS. The cooling lubricants are added excessive contamination, too much foreign oil content or too high contamination eliminated as hazardous waste.

• – Konzentrationsrückgang wichtiger KSS-Inhaltsstoffe;
• – Zunahme des Korrosionsrisikos;
• – Verlust von Kühl- und/oder Schmierwirkung des KSS;
• – Verstopfungen von Rohrleitungen durch Biomasse;
• – Mikrobiell bedingte Hautschäden und Infektionsrisiken für das Personal;
• – Bildung toxischer mikrobieller Stoffwechselprodukte;
• – Vermehrung pathogener Keime;
• – Erhöhtes Risiko der Bildung von kanzerogenen Nitrosaminen infolge mikrobieller Reduktion von Nitrat zu Nitrit;
• – allergenes Potential.

In metalworking processes, uncontrolled growth of microorganisms in KSS can cause the following problems:

• - Concentration decline of important KSS ingredients;
• - increase in the risk of corrosion;
• - Loss of cooling and / or lubricating effect of the KSS;
• - Blockage of pipelines by biomass;
• - microbial skin damage and infection risks to personnel;
• - formation of toxic microbial metabolites;
• - multiplication of pathogenic germs;
• - Increased risk of formation of carcinogenic nitrosamines due to microbial reduction of nitrate to nitrite;
• - allergenic potential.

These All problems have the consequence that the service life of the cooling lubricant is shortened and big Masses of KSS must be eliminated. This increases the cost of machining.

to Elimination of used KSS are from the hazardous waste disposal companies used chemical / physical processes. In these procedures there is a demulsification and a separation of oil and water. The oil becomes prevalent thermally recycled, the water fraction must be before the initiation be post-treated biologically in the sewage system. At high Held at biocides in the cooling lubricant It can cause disturbances come in the biological wastewater treatment plant.

In front The elimination of used KSS can be a decentralized concentration be made by ultrafiltration or evaporation. there becomes the oily one Phase concentrated, so as to eliminate a lower mass is. The separated water phase can either be internal be used again or will be the operational wastewater treatment fed.

The The main problem with the use of the described KSS is the susceptibility of the emulsions microbial infestation. The temperature of KSS in metal working machines lies i.a. between 20 and 50 ° C. In addition to these cheap Growth temperatures make them a good nutrient medium for many bacteria, fungi and Yeasts by the contained organic compounds. KSS included all for The growth of these microorganisms required elements such as Carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus as well as water.

For safe operation of the cutting production an increased germ load should be avoided. The maximum microbiological burden in KSS should not exceed a bacterial count of 10 ⁶ cfu / ml (CFU: colony-forming units as a measure of bacterial load). So far, this has been achieved in many areas of the industry by the addition of biocides. The use of these compounds is ecologically not without controversy, since health-damaging effects on the employees can not be completely ruled out. Another disadvantage of the use of biocides is that resistances to the biocides can develop, so that either the concentrations are greatly increased, the biocides must be changed frequently or complex biocide mixtures must be used. For these reasons, the current EU Biocidal Products Directive (Directive 98/8 / EC of 16.02.1998 on the placing on the market of biocidal products) aims to significantly reduce the use of biocides.

To extend the emulsion service life plants are known, which can be connected to the KSS cycle of processing machines and basie based on different process concepts Most of the treatment plants contain a mechanical separation of the solid and liquid contaminants from the cooling lubricant, as used in the DE 298 16 019 U1 or the DE 195 15 710 A1 are shown. For germ reduction, a UV irradiation is additionally performed in these documents. Also the procedure of DE 199 58 021 A1 uses the germicidal effect of UV radiation. UV radiation in the wavelength range of about 254 nm has an excellent germ-reducing effect in transparent media such as air or clear water by damaging the DNA of microorganisms. Essential for an effective UV treatment is that the layer thickness to be treated is as small as possible, since the penetration depth of this radiation in emulsions is extremely low. UV treatment is an established method of clearing water and packaging surfaces. However, the germ reduction is problematic if the liquid to be treated is cloudy and / or, as with KSS, a mixture or emulsion. The layer thicknesses in which the fluid can be sterilized become smaller and smaller with increasing contamination. As a result, in the case of existing irradiation devices, the volume flow to be sterilized is reduced further and further. The W treatment is therefore not suitable for turbid liquids such as emulsions. Especially with contaminated cooling lubricant, the penetration depth of the UV rays is too low.

From the DE 33 32 561 C2 a method is known in which bactericidal copper ions are electrolytically introduced into the KSS. The advantage of this method is the ease of use. However, the electrolytic treatment of KSS emulsions with copper anodes has the disadvantage that copper not only has good bactericidal properties but is also toxic to humans. This method thus has no advantage over the use of biocides for the preservation of KSS.

Out Water treatment are methods of chemical reduction of Germs by halogenation (addition of, e.g., chlorine, bromine, iodine), ozonation or addition of biocidal substances such as silver, copper and further commercial Biocides known (see, for example: http: // www.bayern.de/wwa-ab/technik/Wv/Waufbereit/aufbereit.htm#sonst). However, not all of the chemicals and processes described are useful for KSS used. Many chemical processes are disadvantageous as they occur the complex structure of the cooling lubricant can influence. An excess of halogens or ozone in the KSS would the various organic compounds found in the cooling lubricant contained, partially or completely oxidize.

Farther For example, a process is known in which water is split electrolytically (company info: Mall Neutra). The electrolytic cleavage of Water in oxygen and hydrogen is not without problems. It can not be ruled out that the emulsion can pass through the occurring reaction can be split. Moreover, the formation of Oxygen gas safety concern. A noticeable effect in terms of germ killing is for this procedure about it but not described.

at another method, such as, for example, the Fa. D.A. Stuart known is, the KSS is in a heat exchanger heated and thereby released from the germs. The disadvantage of heating of thermally labile emulsions in conventional heat exchangers However, that is to achieve the desired Medium end temperature always overtemperatures required at the heat exchanger surfaces are. The overtemperatures the heat exchanger surfaces relative to the The desired medium final temperature is usually between 10 and 50 K and cause a number of undesirable effects. On the one hand arise at the heat exchanger surfaces overheating, where certain salts such as carbonates can precipitate. such precipitations can lead to encrustations on the heat exchanger surfaces, the so-called scaling. The heat exchanger surfaces must be from cleaned these incrustations at regular intervals become what causes costs. In addition, you can the hot ones Heat exchanger surfaces too Fouling effects occur, whereby soft coverings arise. Soft coverings can be used for emulsions by deposits of free oils and by deposits of other substances of the KSS, such as e.g. from Emulsifiers or other additives are caused. The overtemperatures can also a thermal damage effect the used KSS. One of the causes of this is that the wall temperatures must be at least 10 Kelvin hotter than the required Disinfecting temperature. If e.g. a temperature of 75 ° C is needed reliable about the KSS To sterilize, the wall temperature of the heat exchanger should be at least 85 ° C. In practice, even higher overtemperatures realized with small heat exchangers get along. At temperatures of 85 ° C or higher but can be after a short time Treatment period significant product damage occur. The KSS can then after a few sterilizing and cleaning cycles, their performance characteristics to lose.

The object of the present invention is to provide an economical method and an associated device, with which the contamination of used and contaminated KSS can be efficiently reduced even without the use of biocides. The process should treat the cooling lubricant gently, largely avoid scaling and fouling and provide stable process properties.

presentation OF THE INVENTION The object is achieved with the method and the device according to claims 1 or 14 solved. Advantageous embodiments of the method and the device are the subject of the subclaims or can be understood from the following description and the embodiments remove.

at the present process is the coolant and lubricant or a fraction obtained therefrom by irradiation with electromagnetic Radiation heated, that of the liquid Medium absorbed and in heat is implemented. The heat is due to the absorption of the radiation directly in the liquid medium, i.e. the coolant and lubricant or the fraction obtained therefrom. Suitable, for example Microwave (MW), Infrared (IR) or high frequency (RF) heating. The skilled person is the for These technical applications needed wavelength and Frequency ranges known. The heating takes place except for the Germinating temperature, in the number of germs contained in the liquid medium is reduced.

Under liquid Of course, medium in the present patent application also viscous media, such as muddy substances containing a lot of solid particles can contain Understood.

One Advantage of the heating process used is that the heat through Energy conversion directly in the product to be heated - in this Trap directly in the KSS - generated becomes. About temperatures are on hot heat exchanger surfaces not required because the maximum temperature of the process is generated directly in the KSS. Problems with product damage, coverings and encrustations as in known thermal processes can thus reduced to a minimum become.

In a particularly advantageous embodiment of the method and The device is the energy through a microwave field in the KSS introduced, wherein the microwave field through or through several microwave magnetrons can be generated. The KSS can batchwise heated in a suitable vessel in the microwave field become. It is also possible the KSS in the microwave field in a flow system, eg. In an open Channel or in a suitable flow volume or flow container (e.g. Hose), to heat. Other benefits can be achieved if the geometries of the open flow channels, water heaters or the batch vessels to the Properties, energy densities and geometries of the microwave field specifically adapted become. Can be varied while the volume and the geometric shape of the vessel (e.g. Cuboid, sphere, torso, cylinder, cone, .... or combinations of different parts of such forms). Furthermore, the perfused Cross sections optimized and to the penetration depth of the microwave field customized become. More complex geometries to optimize the energy input are natural possible.

When has proven particularly advantageous to use a microwave system in connection with a preheating of the KSS through the heated KSS for heat recovery in a heat exchanger. It can all commercial heat exchanger types be used. The combination preheating / heat recovery with the final warming through a MW plant improves the energy yield and avoids it at the same time high overtemperatures a purely conventional warming. The maximum wall temperatures of the preheat heat exchanger are at this Procedure always lower than the maximum temperature of the KSS, which for the sterilization in the microwave field is generated directly in the KSS. Especially can be in this embodiment, their implementation part the present device is already MW systems of low power for the Sterilization big Use flow rates at KSS.

application finds the KSS-sparing penetrating heating of the KSS in the temperature range from 45 to 140 ° C, especially in the temperature range of 70 ° C -90 ° C.

In a further particularly advantageous embodiment of the invention, the finest particles of metal chips, carbon particles, cutting grain and other solid impurities, which are smaller than 1 mm in diameter, advantageously <200 .mu.m, particularly advantageously <100 .mu.m, not before the thermal treatment from the KSS separated. Surprisingly, it has been shown here that the microwave absorption in the microwave field in the case of contaminated KSS containing the mentioned particles is up to 20% higher than the microwave absorption in clean KSS. This circumstance is used in an embodiment of the method in which the foreign oils and the coarse solid impurities, eg. B. large chips> 1 mm in length, other waste such as cigarette butts, glass, metal, plastic, etc., before treatment from the contaminated KSS are separated by a mechanical separation process and the fine impurities with dimensions <1 mm, better <200 microns, preferably <100 microns, are selectively left in the KSS to optimize the microwave absorption in the MW field. Thus, depending on the processed material and the chip size obtained and depending on the used cutting material such as cutting / abrasive grain or hard metal, an optimum particle size and particle concentration can be set to optimize the microwave absorption and thus the per unit area transferable amount of energy. In one of the exemplary embodiments it is shown how different materials and material concentrations can affect the energy yield in a microwave field.

In a further advantageous embodiment of the method - as is from the technology of fluidized bed heat exchangers is known - form, Size and material of the particles that remain in the cooling lubricant after mechanical pre-cleaning be, to the flow conditions of the heat exchanger adapted, the for heat recovery is being used. It has been shown that solids-containing KSS in the heat exchanger an improvement of the heat transfer can effect. This can be achieved by targeted adjustment of particle size distribution, Material selection and particle concentration achieved before preheating become. To set the appropriate parameters (particle size, material, concentration, etc.), the expert uses procedural Separation techniques according to the prior art. So, there are many Solid-liquid separation process, targeted by particle sizes to enrich. Classification techniques, swim-sink procedures or e.g. magnetic separation methods can help separate different material fractions. Such process designs are known to the person skilled in the art.

In a further advantageous embodiment of the method Shape, size and material of the particles remaining in the cooling lubricant after mechanical pre-cleaning, first on the preheating optimized and then adapted to the microwave heating. So can eg first a mechanical pretreatment is performed, the v.a. particle left in the KSS, the particularly good properties in the microwave field and in the heat exchanger exhibit. After preheating are then separated the particles that are beneficial in the heat exchanger, and only the particles in the cooling lubricant are left for the optimization of the Microwave entry are required.

Some Microorganisms are able to form spores that are very heat resistant are. After the first heating can germinate the spores and germinate the KSS again. In one embodiment the process uses this effect. It is in a first Process step with the heating method used Activation of spores causes. Germs that can not form spores killed. After setting suitable conditions for germination of the spores (Temperature-time window), the KSS is re-used with the Heating process heated. Sprouted spores are in this second Killed off step.

Of the KSS can be direct or - through a second water cycle indirectly - also for cooling one or several water cooled Magnetrons are used while being preheated. It is also possible to enter or more air-cooled Magnetrons to use and the heated air to preheat the KSS to use. Similar options for preheating KSS also result from the use of waste heat sources with infrared or HF systems.

The inventive method can be used so that the KSS is heated and germ-reduced KSS in cooled State or still hot in a cleaned container is given. In this way is the risk of recontamination least.

Farther is possible, the KSS after heating still hot through the still contaminated piping of the machine and back into the collecting container. there can also sterilizes the piping, the machine and the KSS container become. It is also possible, the inventive method into a KSS cycle in a large machining operation too integrate. This can be over one Bypass operation can be realized, with always only a partial flow is sterilized. It makes sense, however, always the entire KSS power otherwise the effects of recontamination dominate.

A another particularly suitable embodiment of the method according to the invention plans to produce KSS concentrates or KSS targeted with substances to offset that to an increased Absorption of MW energy in the KSS lead. Possibly. can activated carbon, Metal chips, organic or inorganic salts, SiC particles or the like Particles, colloidal substances or soluble in KSS substances are added. Change salts the conductivity of the water and the dielectric properties of the concentrates and thus also the hydrous KSS.

The The present device comprises at least one heating device with an irradiation unit for heating the cooling and Lubricant by radiation absorption, a pumping device for the transport of the cooling and lubricant through the heating device, a temperature measuring device for measuring the temperature of the emerging from the heating device, heated cooling and lubricant, a temperature control device for regulation the temperature of the heated device emerging from the heating device Cold and Lubricant by controlling a pump power of the pumping device dependent on from the measured temperature, and a heat exchanger for preheating the Coolant and lubricant with the exiting from the heating device, heated cooling and Lubricant.

Especially advantageous is the combination of mechanical pretreatment for Fractionation and / or size / density separation the particle with subsequent preheating with conventional heat exchanger and subsequently MW warming. The microwave can be a commercial one MW instantaneous water heater or a microwave oven in which a hose, pipe or other geometric body, which flows through the used, contaminated KSS.

Short description of drawings

The present methods as well as the associated device are hereafter based on embodiments briefly described in connection with the drawings. in this connection demonstrate:

1 the change in microwave absorption or energy input of differently contaminated KSS compared to pure KSS; and

2 a schematic of an exemplary microbial reduction device based on MW heating.

Ways to execute the invention

In a first example, 12 liters of a germinated KSS with a total aerobic bacterial count of 10 ⁷ CFU / ml are conveyed by means of a peristaltic pump through a commercially available microwave oven (maximum power consumption 1,300 W) to demonstrate the germ reduction with the present method. The maximum temperature after the MW heating was 83.5 ° C, the average residence time at this temperature was 30 seconds. By means of a plate heat exchanger, a heat recovery could be achieved. Subsequently no germs were detectable in the treated KSS (<10 CFU / ml).

A second example shows the increase in microwave absorption by solid particles in the cooling lubricant. 9 sample batches were produced. Each sample batch consisted of 10 individual samples, each containing 100 ml of a freshly prepared water-miscible cooling lubricant. All samples of the first batch of samples were heated for 40 seconds at full power of the microwave oven (1300W) in a commercial microwave oven. The temperature increase of each sample was determined and the arithmetic mean of all samples was formed. This value was defined as a reference (100% energy input). The other sample lots were contaminated with particles of activated carbon (Ak), silicon carbide (SiC) and iron (Fe) between 0.2% and 10%. The particles had a size distribution of 5 μm to 200 μm. The heating of the contaminated sample batches was carried out analogously to the first batch. The achieved energy input in the contaminated KSS samples is in comparison to the energy input in pure KSS in the 1 shown.

It you notice that contamination of the KSS with higher concentrations of SiC, Ak and Fe improve the energy input or better MW absorption in the samples can be achieved by up to 20%. Even concentrations of only 0.2% already cause an increase of Energy input of up to 2%. It therefore seems particularly expedient, very fine particles, which are always included in used KSS, not completely before the microwave heating separated from the KSS, but rather the highest possible concentration to remain in the KSS. Only the larger particles, which lead to blockages can, should be before heating be separated.

2 shows schematically an example of the present device for microwave sterilization with upstream particle fractionation and heat recovery. The contaminated KSS is removed from the storage tank 1 first by a fractionator 8th for the mechanical fractionation of particulate Passed impurities, in which it is freed by mechanical fractionation of coarse impurities. The KSS then passes through a heat exchanger 2 for preheating / heat recovery through or from the already heated cooling lubricant. After the heat exchanger 2 The now preheated KSS enters the microwave field of a microwave oven 3 in which it is heated to disinfection temperature. The KSS lingers at this temperature for a certain amount of time and finally passes through the heat exchanger again 2 in the collecting container 4 for sterilized KSS. Alternatively, the KSS can also be returned to the storage tank 1 be transported back. The final temperature after MW heating is measured with a temperature measuring device 5 supervised. A temperature control 6 regulates this temperature by controlling the pump 7 about the flow rate of the KSS through the microwave oven 3 ,

LIST OF REFERENCE NUMBERS

Claims (17)

Process for the treatment of contaminated, water-containing coolants and lubricants, wherein the coolant and lubricant or a fraction obtained therefrom forms a liquid medium which is heated to reduce contained germs, characterized in that the heating is effected by irradiation with electromagnetic radiation which is absorbed by the liquid medium. Method according to claim 1, characterized in that that the heating takes place with microwave radiation. Method according to claim 1 or 2, characterized that the liquid Medium is heated in a heating volume, its geometry adapted to a radiation distribution of the electromagnetic radiation is to be a spatially uniform heat generation in the liquid To reach medium. Method according to one of claims 1 to 3, characterized that the liquid Medium before heating with already heated liquid medium preheated becomes. Method according to one of claims 1 to 4, characterized that the liquid Medium heated by heating to temperatures between 45 ° C and 140 ° C. becomes. Method according to one of claims 1 to 5, characterized that the cooling and lubricant before heating not or only in one way is pretreated, in which the liquid medium still Feinstpartikel with a size <1 mm as impurities contains. Method according to one of claims 1 to 5, characterized that the cooling and lubricant before heating not or only in one way is pretreated, in which the liquid medium still Feinstpartikel with a size <200 .mu.m, preferably <100 .mu.m. Method according to one of claims 1 to 5, characterized that from the liquid Medium before heating with a mechanical separation process solid particles separated by a size> 1 mm and / or> 200 microns and / or> 100 microns become. Method according to one of claims 1 to 8, characterized in that by a targeted Vorbe a distribution of particle sizes and / or a particle concentration and / or a material composition of the particles are obtained in the liquid medium, which contribute to the optimization of heat generation and / or heat transfer between the liquid medium before heating and the already heated liquid medium , Method according to claim 9, characterized in that that the pretreatment takes place in two stages, whereby in a first Stage before preheating of the liquid Medium with the already heated liquid medium an optimization with regard to the heat transfer between the liquid Medium before irradiation and already heated liquid medium carried out will and after preheating in a second stage an optimization with regard to the absorption the electromagnetic radiation takes place in the liquid medium. Method according to one of claims 1 to 10, characterized that several heating steps are carried out, wherein the liquid medium after a first heating step for a certain time in one Temperature range is maintained, the germination of heat-resistant spores favored. Method according to one of claims 1 to 11, characterized that the liquid Medium before heating with waste heat from components for the generation of electromagnetic radiation is preheated. Method according to one of claims 1 to 12, characterized that the liquid Medium before heating substances are added, which is the absorption increase the electromagnetic radiation. Apparatus for the treatment of contaminated, aqueous refrigerants and lubricants, comprising - a heating device ( 3 ) with an irradiation unit for heating the coolant and lubricant by radiation absorption, 7 ) for the transport of the coolant and lubricant through the heating device ( 3 ), - a temperature measuring device ( 5 ) for measuring the temperature of the heating device ( 3 ) exiting, heated coolant and lubricant, - a temperature control device ( 6 ) for regulating the temperature of the heating device ( 3 ) exiting, heated coolant and lubricant by controlling a pumping power of the pumping device ( 7 ) depending on the measured temperature, and - a heat exchanger ( 2 ) for preheating the coolant and lubricant with the from the heating device ( 3 ) exiting, heated coolant and lubricant. Apparatus according to claim 14, characterized in that the heating device ( 3 ) is a microwave flow heater or a microwave oven. Apparatus according to claim 14 or 15, characterized in that in front of the heating device ( 3 ) a fractionating device ( 8th ) is arranged for the mechanical fractionation of particulate impurities from a supplied coolant and lubricant. Device according to claim 16, characterized in that fractionating means ( 8th ) is designed so that it separates solid particles with a size> 1 mm and / or> 200 microns and / or> 100 microns with a mechanical separation process of the coolant and lubricant.