Method for recycling plastics implementing a size-exclusion simulated moving bed device

Device for extraction by size exclusion of dissolved polymers from a polymer solution, said device comprising:

• n fixed beds of a size exclusion solid, n being an integer greater than or equal to 4, preferably of between 4 and 30, said size exclusion solid having a volume-average pore diameter of preferably between 1 and 500 nm, preferably between 2 and 100 nm, preferentially between 2 nm and 50 nm, preferentially between 3 and 30 nm, and with preference being a silica gel, a grafted silica, a carbon molecular sieve or mixtures thereof,
• the n fixed beds of the size exclusion solid being distributed in one or more column(s), the n beds being connected in series and preferably in a closed loop,
• N systems for injection of the polymer solution, N systems for injection of an eluent, N systems for withdrawal of an extract and N systems for withdrawal of a raffinate, N being an integer preferably equal to n, said injection and withdrawal systems being located between two consecutive beds or optionally upstream of the first bed,
• wherein the systems for injection of the polymer solution and of the eluent and/or the systems for withdrawal of the extract and of the raffinate which are located at one and the same position are distinct or identical,
• each injection and withdrawal system comprising at least one valve suitable for allowing or not allowing the passage of a stream of polymer solution and/or of eluent and/or of extract and/or of raffinate, preferably a series of on-off valves which are controlled by an automatic sequence, or a single rotary valve, so as:
• to define, at an instant t, a point of injection of the polymer solution, a point of injection of the eluent, a point of withdrawal of the extract and a point of withdrawal of the raffinate, said points of injection and of withdrawal being distinct from one another and determining at least three, preferably four, successive main operating zones of the n fixed beds:
• a zone I of elution of the impurities, comprised between a point of injection of the eluent and a point of withdrawal of the extract;
• a zone II of elution of the targeted polymer, comprised between the point of withdrawal of the extract and a point of injection of the polymer solution;
• a zone III of retention of the impurities, comprised between the point of injection of the polymer solution and a point of withdrawal of the raffinate;
• and
• optionally a zone IV, comprised between the point of withdrawal of the raffinate and the point of injection of the eluent,
• and to make possible, over time, a shifting in the points of injection and of withdrawal, synchronously or non-synchronously, according to a frequency determined by a predetermined permutation period, by one bed of size exclusion solid per permutation period.