Mixing and distribution device with longitudinal opening

A device for mixing and distributing fluids for a downflow catalytic reactor, said device comprising:

• at least one collecting zone (A) comprising at least one collecting means (5);
• at least one substantially vertical collecting pipe (7) that is able to receive a reaction fluid collected by said collecting means (5) and at least one injection means (8) opening into said collecting pipe (7) in order to inject a quench fluid;
• at least one mixing zone (B), situated downstream of said collecting pipe (7) in the direction of flow of the fluids, said mixing zone (B) comprising at least one fluid mixing chamber (15) of length L1′, said mixing zone (15) comprising a first end in communication with said collecting pipe (7) and a second end in communication with a fluid exchange chamber (16) of length L2′, situated underneath and superposed with said mixing chamber (15);
• at least one distribution zone (C) situated at the same level as the mixing zone (B), downstream of said mixing zone (B) in the direction of flow of the fluids, said distribution zone (C) comprising a distribution plate (12) supporting a plurality of chimneys (13);
• wherein the length L2′ of said exchange chamber (16) is greater than the length L1′ of said mixing chamber (15) so as to create a ceiling (30) on said exchange chamber (16), said ceiling (30) comprising at least one longitudinal opening (31) suitable for the passage of the fluids from said exchange chamber (16) to said distribution zone (C).