NOVELTY - A mixing device comprises a first insert defining an excentric passage, a second insert having a central opening, a third insert positioned downstream the first and second inserts and having at least two openings evenly distributed along a concentric circle within the third insert, and a fourth insert positioned between the first and third inserts and having at least two radially extending first deflectors.    USE - The mixing device is used for the homogenization of temperatures and/or concentrations in a fluid flow, e.g. syngas comprising vaporized water. It can be incorporated in a power generator applied in electrically driven vehicles, e.g. cars.    ADVANTAGE - The combination of the first insert defining an excentric passage and the second insert having a central opening enables the construction of a relatively compact mixing device, as the fluid can be mixed by radial deflection between the inserts. Eddies may be generated along the periphery of the first insert and the periphery of the central opening in the second insert, which improves the mixing of the fluid flow passing the inserts.    DETAILED DESCRIPTION - A mixing device comprises a hollow element (9) containing a first insert positioned within the hollow element and defining an excentric passage (12), a second insert (13) positioned within the hollow element upstream the first insert and comprising a central opening (14), a third insert (16) positioned in the hollow element downstream the first and second inserts and comprising a least two openings (17) evenly distributed along a concentric circle within the third insert, and a fourth insert (19) positioned in the hollow element between the first and third inserts and comprising at least two radially extending first deflectors (20). INDEPENDENT CLAIMS are also included for:    (a) a module for the mixing device comprising four inserts and a framework, e.g. set of strips, where the inserts are fixed in the framework;    (b) apparatus for forming syngas, including a quench and the inventive mixing device connected to the quench; and    (c) power generator comprising at least a fuel cell and the apparatus for forming syngas.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of the mixing device.    Hollow element (9)    Excentric passage (12)    Second insert (13)    Central opening (14)    Radial passage (15)    Third insert (16)    Openings (17)    Deflectors (18)    Fourth insert (19)    First deflectors (20)    Second deflectors (22)    Plug-and-socket connections (24)    Perforated plate (25)