Method for purifying a coolant, such as for example quench fluid, contaminated with particles of a heated petroleum fraction, wherein - the contaminated coolant is subjected to a purification process in order to separate the coolant from the particles of the petroleum fraction, - the purification process is divided into a primary purification inside a primary separator and secondary purification in a secondary separator (10.1/10.2), wherein the secondary purification is carried out substantially without a filter, characterised in that - contaminated coolant can be diverted from the secondary separator (10. 1/10.2) by means of a discharge nozzle, in order to influence the viscosity and to release a filter which sits transverse to a longitudinal axis of a main body in the rotating hollow space of the secondary separator, from washed up particles, so that in particular sedimentation is maintained, and - additional purified coolant or other process-suitable fluid can be introduced into the secondary separator (10.1/10.2) by means of a feedback unit, wherein the feedback unit cooperates with the discharge nozzle in such a way that purified coolant or other process-suitable fluid is accepted into the rotation hollow space of the secondary separator (10.1/10.2), in order to liquefy the viscous contaminated coolant in such a way that sedimentation is guaranteed, wherein the filter is purified at the same time by returning the purified coolant or other process-suitable fluid into the rotating hollow space, and subsequently the discharge nozzle is opened for volume compensation, so that the coolant or other process-suitable fluid can be removed from the secondary separator (10.1/10.2), in order to influence the viscosity, so that in particular the sedimentation is maintained. - the contaminated coolant is subjected to a purification process in order to separate the coolant from the particles of the petroleum fraction, - the purification process is divided into a primary purification inside a primary separator and secondary purification in a secondary separator (10.1/10.2), wherein the secondary purification is carried out substantially without a filter, characterised in that - contaminated coolant can be diverted from the secondary separator (10. 1/10.2) by means of a discharge nozzle, in order to influence the viscosity and to release a filter which sits transverse to a longitudinal axis of a main body in the rotating hollow space of the secondary separator, from washed up particles, so that in particular sedimentation is maintained, and - additional purified coolant or other process-suitable fluid can be introduced into the secondary separator (10.1/10.2) by means of a feedback unit, wherein the feedback unit cooperates with the discharge nozzle in such a way that purified coolant or other process-suitable fluid is accepted into the rotation hollow space of the secondary separator (10.1/10.2), in order to liquefy the viscous contaminated coolant in such a way that sedimentation is guaranteed, wherein the filter is purified at the same time by returning the purified coolant or other process-suitable fluid into the rotating hollow space, and subsequently the discharge nozzle is opened for volume compensation, so that the coolant or other process-suitable fluid can be removed from the secondary separator (10.1/10.2), in order to influence the viscosity, so that in particular the sedimentation is maintained. - contaminated coolant can be diverted from the secondary separator (10. 1/10.2) by means of a discharge nozzle, in order to influence the viscosity and to release a filter which sits transverse to a longitudinal axis of a main body in the rotating hollow space of the secondary separator, from washed up particles, so that in particular sedimentation is maintained, and - additional purified coolant or other process-suitable fluid can be introduced into the secondary separator (10.1/10.2) by means of a feedback unit, wherein the feedback unit cooperates with the discharge nozzle in such a way that purified coolant or other process-suitable fluid is accepted into the rotation hollow space of the secondary separator (10.1/10.2), in order to liquefy the viscous contaminated coolant in such a way that sedimentation is guaranteed, wherein the filter is purified at the same time by returning the purified coolant or other process-suitable fluid into the rotating hollow space, and subsequently the discharge nozzle is opened for volume compensation, so that the coolant or other process-suitable fluid can be removed from the secondary separator (10.1/10.2), in order to influence the viscosity, so that in particular the sedimentation is maintained.