The invention relates to a device and method for treating a hot gas flow containing slag and to an entrained-bed gasifier system that comprises the device. The device comprises, in a housing, an inlet arranged at the top for the hot gas flow, an immersion pipe, which is arranged vertically and concentrically in the housing and into which the inlet opens, a coolant bath, into which a lower section of the immersion pipe is immersed, and at least one raw gas outlet opening for cooled raw gas that has been freed of slag. The lower section of the immersion pipe is designed as a radially expanded gas distributor bell in the coolant bath. Said gas distributor bell is formed by a substantially conical jacket surface having a cross-section that expands downward, wherein the jacket surface has a plurality of gas passage openings, which are distributed over the circumference of the gas distributor bell. The dimensions of the gas passage openings increase with the immersion depth in the coolant bath.