PURPOSE: To improve heat exchange performance by providing a housing with heat exchanging means which plunge into an aeration zone provided with aeration means and an outlet aperture further disposing an inlet conduit for solid particles plunging into an aeration zone.

CONSTITUTION: The housing 1 is provided with the aeration means 2, 3 having an inlet means 6 for aeration fluid and the outlet aperture 15 and the aeration zone is formed between the aeration means 2, 3 and the outlet aperture 15. The housing is provided with the heat exchange means 4, 5 which have the inlet means 8 and the outlet means 10 for the heat exchange medium and plunge into at least part of the aeration zone. Further, the inlet conduit 13 for solid parts plunging into the aeration zone is disposed. Consequently, the heat exchange performance may be improved without requiring costly stand pipes, valve joints or the like.