Abstract: A method of radiant cooling of a product gas mass stream discharged from a gasification reactor and loaded with particles in a cylindrical radiant cooler with a radiant cooling casing comprises the steps of subdividing the product gas mass stream into concentric cylindrical layer streams by cylindrical radiant cooling walls arranged at a distance from the radiant cooling casing, adjusting layer thickness of the cylindrical layer streams to provide a high radiant heat exchange, and cooling regions of the product gas mass stream which flow to the radiant cooling walls in a pre-cooling region to a temperature caking of the particles.