Acidic condensates, which are produced depending on the combustion process and mode of operation, are neutralized by a flow-through neutralization system containing lime-based granulate and then discharged into the sewage system. The function of the flow-through neutralization system is based on a height difference (natural gradient), so that the system can be operated without electrical connections and pumps. The internal structure of the system prevents overflow in the event of contamination or clogged granulate. Of course, the neutralization systems can also be supplied with feed pumps to overcome structural conditions.