The service life of water-miscible metalworking fluids is limited

Water-miscible cooling lubricant in a machine tool is finite, even with good maintenance.
The composition of water-miscible cooling lubricant (wmCL) is complex and often contains 40 to 50 different chemical components. In addition to a main component of oil (mineral oils, synthetic oils and ester oils), the additives include extreme pressure additives (EP additives), anti-corrosion additives. Biocides (despite high pH value), foam suppressants and adhesion improvers, etc.
Cooling lubricant concentrates are diluted with water to achieve the desired application concentration - range 5 to 10%, in some cases slightly higher.
Metalworking relies on the use of cooling lubricants. Cooling lubricants prevent tools from overheating and flush abrasion from the machining zone. Even with good care, these operating fluids lose their performance properties over time. They then need to be replaced. A number of legal regulations must be observed when disposing of used cooling lubricants.

When maintaining water-miscible cooling lubricants, skimming and separation by gravity are common methods for removing tramp oils. The parameters that are analysed are: pH value, bacterial count, nitrite content, refractive index determination. An HPLC analysis is not carried out, but if the peaks were assigned with retention time, it would be an optimal control of which chemical components have decreased or changed.

There are no standardised change intervals for cooling lubricants, as the service life of a cooling lubricant depends to a large extent on careful monitoring and care by the user.
Oil skimming, coolant lubricant aeration, various types of filtration systems etc. are also available in automatic systems. The pH value and nitrite content of the water-mixed cooling lubricant must be checked weekly in accordance with the Technical Rules for Hazardous Substances. The pH value of water-mixed cooling lubricants is in the alkaline range between pH 8 and 9.5, depending on the manufacturer's specifications. If the pH value drops during use. this indicates a bacterial load, additive discharge or a change in additives that are becoming ineffective.

Disposal involves the recovery of process water and is carried out using physical-chemical emulsion separation, vacuum distillation or membrane filtration - often expensive and time-consuming If a company produces more than 1000 cubic metres of water-mixed cooling lubricant (wmCL) emulsion per year, it is worth investing in a technology. The disposal costs (140 to 200 € / m3 wmCL by external disposal companies or the in-house transport costs are reduced considerably.
Vacuum evaporator technology is expensive to invest in. There are a number of manufacturers worldwide such as INCRO SA, H20-GmbH, Veolia Water Technology, IWE, Condorchem Enviro Solutions and other companies. Here, the spent wmCL is used directly to obtain a purified water phase. However, the result is far from drinking water quality and usually still has COD values of 3000 to 5000 mg/litre. For this reason, subsequent purification steps must follow.

Membrane filtration requires pre-treatment. With ultrafiltration, which is often used here, the pure water yield is 75 to 85%, similar to nanofiltration. A loss of water is therefore always present. The membranes have a limited-service life. A retentate must be further treated. Handling against fouling is complex with backwashing.

Bioway has now developed a process for splitting wmCL by use of high cation charge with purification of the water phase as the main component, which outperforms process water and reduces the COD level to 30 mg/l (WHO specification as the limit value for drinking water is 10 mg/l).
The technology is characterised by the energy-free application of splitting at room temperature, which applies to around 80% of the wmCL products on the market at a cost of €10/m3 wmCL. An aqueous mixture (without demulsifying agents) is added here. For around 20% of the wmCL, splitting in an electrolysis device is selected, whereby the first aqueous mixture of wmCL is used directly in the apparatus without modification. The energy requirement here is also low! This process is therefore economical and environmentally friendly. The operating costs for water purification are only 10 € / m3 of water.

If you want to split all wmCL directly, it can also be transferred immediately to the electrolysis unit, where energy must be used, albeit at a low level.
The separated oil phase is transferred to the mineral oil industry for processing. The water phase obtained after splitting is still contaminated with a COD level of around 13000 mg/l. The water phase is purified using an electrolytic method - electro-oxidation (EO). This quality of water can be reused.
The advantage of EO is that no waste products are produced (precipitates etc.) as mineralisation takes place where hydroxyl-radicals are responsible. The process (EO) was realised on an industrial scale and in the laboratory. A small investment is required for the EO-system. The process can be categorised as 'zero-waste/zero-liquid-discharge' and is economical and environmentally friendly.

Why this technology?

- It is easy to handle - an aqueous mixture is added and left to stand (splitting of the wmCL emulsion) - no energy consumption.
- The energy consumption is acceptably low in comparison for all stages
- In principle, it works without the use of organic chemicals (without demulsifying agents)
- The yield of pure water is high - higher than with the technologies mentioned (vacuum evaporator, membrane filtration)
- The phases are separated mechanically, visually and almost completely
- Biological factors do not play a role here
- The systems for splitting and separating the two phases of oil and water are closed systems - there are no contact zones
- The oil is completely recycled - externally by an oil company.
- The purified water with a COD level of 30 mg/l is clear, colourless water of almost drinking water quality.

Bioway Consulting SL
C. / Tirant Lo Blanc 4 - office 19
ES-03750 Pedreguer / Alicante - Spain
Mr. Norbert Pautz - Managing Director
Bioway Consulting SL

Bioway Consulting SL is an engineering company in the consulting business, with activities in research and development of new technologies in the field of wastewater purification based on electrolysis technologies.
It was founded in 1989 in Germany as a sole proprietorship and later continued in Switzerland as Bioway GmbH. The main activity at that time was initially as a distributor for renowned companies from abroad (e.g. Charm Sciences / USA and Malthus Instruments Ltd / UK etc.). This was followed by own developments with production such as the IGDS (Intelligent Gravimetric Dilution System) and devices for water disinfection.
The focus on water disinfection / water and waste water purification was intensified. In addition, a system for the inactivation of airborne germs (viruses/bacteria) was developed and manufactured (Corona Wave).
Today, Bioway is active in the consulting business and co-operates with other European companies in the field of waste water purification and develops processes by testing customer waste water samples in its own laboratory.

This release was published on openPR.