Reactor equipped with sieve-like bodies and methods for reactor operation

in which a gas or a liquid is chemically converted by means of a catalyst the reactor comprising a plurality of catalyst-coated material sieve-shaped bodies (2) and with a heat exchanger in the reactor, by means of which a heat exchange between a fuel gas mixture and a cooling or heating medium can be carried out, wherein the sieve-like body (2) one after the other within a channel (1) are arranged, within the duct (1) a plurality of through the sieve-like body (2) guided through small pipes (3) are arranged, which constitute the heat exchanger, characterized in that that the sieve-like body (2) are so arranged behind one another 1, that regularly a deflection of the fluid flow is ensured.