System and method for concentrating substance-containing fluids by means of multi-stage evaporation

A system for the concentration of substance-containing fluids by multi-stage evaporation, in particular of solutions such as N-methylmorpholine-N-oxide (NMMO), wherein the system is configured with at least a first evaporator and a second evaporator, wherein the first evaporator is connected to the second evaporator in a suitable manner such that fluid concentrated in the first evaporator can be conducted into the second evaporator in order to further concentrate concentrated fluid in the second evaporator, wherein a first mechanically acting compressor unit is provided, with which vapor formed in the first evaporator can be compressed downstream, and wherein the system comprises a first supply line for supplying vapor compressed with the first mechanically acting compressor unit to the first evaporator, wherein a second mechanically acting compressor unit is provided, with which vapor formed in the second evaporator can be compressed downstream, wherein vapor compressed by the second compressor unit can be supplied to the first compressor unit, wherein the first compressor unit comprises a plurality of compressors and the second compressor unit comprises a plurality of compressors, wherein vapor in the second compressor unit is compressed to a larger outlet temperature minus inlet temperature difference than in the first compressor unit.