Modular mass transfer and phase separation system

A modular mass transfer and phase separation system for a fluid comprising a mass transfer component and a second component from which the mass transfer component is separable by mass transfer. The system has a first stage and at least one later stage each stage comprising: co-current contacting means for co-currently contacting at least two fluid streams to effect mass transfer of the mass transfer component and phase separation means for separating phases from the co-currently contacted fluid streams. The stages are in fluid communication so that at least two fluid stream which has been separated by phase separation in the early stage is communicable for co-current contacting and for phase separation in a later stage. At least one fluid stream which has been separated by phase separation in a later stage is communicatable in a counter-current direction for co-current contacting and for phase separation in the early stage. The system may be modular. The invention also relates to a method of effecting mass transfer and phase separation utilised in the above system.