Recycling of used, water-miscible cooling lubricants - a new technoloy

There are around 1000 manufacturers of cooling lubricants worldwide. Accordingly, the formulations of water-miscible cooling lubricants are numerous. The formulations are tailored to a specific metalworking process and type of metal. The cooling lubricant must be replaced after intensive use over a longer period of time and must be categorised as hazardous waste. Currently, companies in the metalworking industry with an average volume of coolant lubricant are expected to produce 200m³/year of coolant lubricant hazardous waste - that would be approx. 850 litres/day with 230 working days - which corresponds to around 100 litres/hour. At 850 litres per day, this corresponds to 24.65 kWh per day. The price of a kWh = 20 cents (industrial price for electricity € 0.20 kWh) corresponds to € 4.93.
In the past, about 10 to 15 years ago, the composition of cooling lubricants was not so complex. Progress in the optimisation of cutting fluids tailored to specific applications changed the composition, which today can contain up to 50 different substances. Whereas it used to be possible to split cutting fluids under flow conditions electrolytically without changing the alkaline pH value, this is largely no longer possible today. One of the reasons is that the difference in density is too small to allow phase separation - whereby 'creaming' can occur. Fatty acids are often responsible for this behaviour. In contrast to electrocoagulation (EC), no sacrificial anode is used for splitting, but rather a dimensionally stable electrode.
Cooling lubricant emulsions were freshly prepared in different concentrations and their splitting was analysed. Furthermore, used cooling lubricants of different products as well as contaminated, used, old cooling lubricant emulsions were analysed. It was found that these emulsions can be categorised differently. These were then further purified using electro-coagulation/oxidation and the COD values were measured.
It was shown that standardisation is necessary in order to split all the different cooling lubricants. An economical method for splitting cutting fluids is hardly used at this time, if at all. Known methods are too expensive and disadvantageous, as the water phase is not recovered in purified form. However, this is essential, as after separation of the two phases: Water and oil, the water is still heavily contaminated or polluted.
The aim of the process with the device is to achieve a good separation of the two phases oil and water in liquid form, whereby the aqueous phase is further purified by electrolytic methods. These methods are electrocoagulation and electro-oxidation. The cooling lubricant - abbreviated to MWF, metal working fluid - today has COD values of up to a good 160,000 mg/litre. Good separation in the form of coalescence should achieve a significant reduction in the COD level in the first step and is a prerequisite for reprocessing in the next steps.
A key factor in the application of the new technology is that it is economical and, compared to vacuum distillation, the price per cubic metre is still significantly lower, despite the number of 3-4 stages. The energy requirement is the theoretical heating of water, which should normally reach 45°C. This means that a ∆T of 25°C must be achieved from room temperature (20°C). This only applies to splitting.
Total costs / 850 litres per day:
1. Splitting of the emulsion (KSS) € 4.93 Electricity requirement: Costs for acidification: € 0.83 /kg acid
2. Electrocoagulation (1.5 - 2.0 kWh / m³) - 1.7 kWh = € 0.34
3. Activated carbon filtration (without electricity, only electricity for pumps) 1 kg for 850 litres = € 6.52
4. Electro-Oxidation at room temperature - Electricity costs: 1 kWh = € 0.20

The total costs are: 12.80 EUR / day x 230 days = 2'944 € / year. Costs for operating the system, which can be partially automated, are not included.
The investment costs are manageable and depend on the volume of water used. For 1m³ / day, it is a small system with a belt filter for the EC. Materials for the reactors are mainly plastic - glass can also be used for the fission reactor.

Bioway Consulting Ltd / Cyprus
Auxiliary Office
C./ Tirant Lo Blanc 4, 3rd floor, room 19
ES-03750 Pedreguer / Alicante
Spain
phone: 0034 965030786
mail: contact@biowayconsulting.com
https://www.biowayconsulting.com
Managing Director: Norbert Pautz

Bioway Consulting Ltd is an engineering company formerly Bioway GmbH / Switzerland. Bioway is active in the fields of waste water treatment to clean water with technology of electrolysis. Bioway is looking back on more than 30 years of experience in analytics in microbiology, disinfection of water and air to kill virus / bacteria. Disinfection of emulsions also have been applied. Now Bioway is active as a consultant but with an own laboratory to do r&d for e.g. cooling lubricants and waste water treatment by EC / EO. Bioway works with other European companies for sales business.

This release was published on openPR.