Patent Claims 1 A process for purification of mineral oil comprising the steps of prefiltrating the oil followed by passing the prefiltrated oil through a filtering unit in which the filtermedia comprises organic fibres and carbon particles, said organic fibres and carbon particles being adhered to each other by a binder 2 A process according to claim 1 in which the oil is prefiltrated by passing through one or more prefiltration units 3 A process according to claim 2 in which the oil is prefiltrated by passing it through more prefiltration units 4 A process according to claim 3 in which the prefiltration units remove particles with decreasing sizes in the direction of the flow 5 A process according to any of claims 3-4 in which the oil is prefiltrated by passing it through three prefiltration units 6 A process according to claim 5 in which the first prefiltration unit is trapping particles bigger than the order of magnitude of 12 pm, the second prefiltration unit trapping particles bigger than 6 pm and the third prefiltration unit trapping particles bigger than 1 pm 7 A process according to any of claims 1- 6 in which the prefiltration is performed by using a filtering media made of glass fibres 8 A process according to any of claims 1-7 in which the filtering media in the filtering unit contains 5-95% carbon based on the weight of carbon particles and fibres 9 A process according to any of claims 1-8 in which the fibres in the filtering unit are natural fibres 10 A process according to claim 9 in which the fibres are cellulosic fibres 11 A process according to any of claims 1-10 in which the binder is a positively charged resin 12 A process according to any of claims 1-11 in which the fibres, the carbon particles and the binder is in the form of a filtering plate 13 A process according to claim 12 in which the filtering plate is supported by a net 14 A process according to claim 13 in which the filtering plate is supported by a net of plastic 15 A process according to claim 13 in which the filtering plate is supported by a net of steel 16 A process according to any of claims 1-15 in which the oil after being passed through the prefiltration units and before being passed through the filtering unit is passed through one or more vacuum units
17 A process according to any of claims 1-16 in which the oil before being passed through the prefiltration units is heated to a temperature of 50-90 °C 18 A process according to any of claims 1-17 in which the oil is cooled immediately before passing through the filtering unit
19 A process according to claim 18 in which the oil is cooled to a temperature of 10-30 °C 20 A process according to any of claims 1-19 in which the oil after being passed through the filtering unit is passed through an additional filtration step 21 A process according to any of claims 1-20 in which the oil is forced through the treatment steps by the use of a pump 22 An apparatus for the purification of mineral oil comprising means for prefiltrating the oil and a filtering unit in which the filtering media comprises organic fibres and carbon particles said organic fibres and carbon particles being adhered to each other by a binder 23 An apparatus according to claim 22 in which the filtering media in the filtering unit contains 5-95% carbon based on the weight of carbon particles and fibres 24 An apparatus according to any of claims 22-23 in which the fibres in the filtering unit are natural fibres 25 An apparatus according to claim 24 in which the fibres are cellulosic fibres 26 An apparatus according to any of claims 22-25 in which the binder is a positively charged resin 27 An apparatus according to any of claims 22-26 in which the fibres, the carbon particles and the binder are in the form of a filtering plate 28 An apparatus according to claim 27 in which the filtering plate is supported by a net 29 An apparatus according to claim 28 in which the net is made of plastic 30 An apparatus according to claim 28 in which the net is made of steel 31 An apparatus according to any of claims 22-30 in which the prefiltration means comprise one or more prefiltration units 32 An apparatus according to claim 31 in which the prefiltration means comprise more prefiltration means 33 An apparatus according to claim 32 in which the prefiltration units remove particles with decreasing size in the direction of the flow 34 An apparatus according to any of claims 32-33 in which the prefiltration means comprise three prefiltration units 35 An apparatus according to claim 34 in which the first unit is trapping particles bigger than approximately 12 μΓη, the second prefiltration unit is trapping particles bigger than approximately 6 pm and the third prefiltration unit is trapping particles bigger than approximately 1 pm 36 An apparatus according to any of claims 22-35 in which the prefiltrating means comprise filters with a filtermedia made of glass fibres 37 An apparatus according to any of claims 22-36 said apparatus comprising one or more vacuum units said vacuum units being placed in the direction of the flow immediately after the prefiltrating means 38 An apparatus according to any of claims 22-37 in which a heater is placed in the direction of the flow immediately before the prefiltrating means 39 An apparatus according to any of claims 22-38 in which a cooler is placed in the direction of the flow immediately before the filtering unit 40 An apparatus according to any of claims 22-39 comprising an additional filter said filter being placed in the direction of flow after the filtering unit 41 An apparatus according to any of claims 22-40 comprising a pump