Problems of operating heating boilers of increased environmental efficiency

Purpose. Ensuring reliable operation of heating heat-generating devices with recirculation and exhaust gas heat recovery. Methodology. The normative methods of thermal calculation for surface heat exchange devices and the software according to the requirements of regulatory methods for this type of equipment for processing the results of our own experimental studies on heat exchange during deep cooling of combustion products of gas-consuming boilers were used. Findings. Calculation studies on the thermal operation modes during the heating period under the conditions of recirculation and heat recovery of flue gases of gas-fired water-heating boiler plants not equipped with air heaters were carried out. The main characteristics were determined of the thermal and humidity operation state for the air-supply ducts of these installations under the conditions of recirculation of flue gases’ part into the blown air. Regularities of temperature and dew point changes in the mixture of admixed gases and air under the conditions of using traditional heat recovery technologies and without them in different boiler modes and with different parts of recirculated gases were established. Problems of ensuring the operability and reliability of such boiler plants are highlighted. It is shown that these problems are related to condensate formation on the internal surfaces of air ducts and their freezing in some operating modes during in the cold period of the heating season. It is also shown that an effective solution to existing problems can be the use of air heaters in heat recovery systems to preheat the blown air before its mixing with recirculation gases. Originality. For the first time, the thermal and humidity operation modes of the air-supply ducts of heating boiler plants with increased environmental efficiency, which is ensured by boiler exhaust gases recirculation into the blown air, have been investigated. Practical value. The obtained research results will be used in the design of systems of recirculation and heat recovery of heat-generating devices’ exhaust gases to improve their environmental and thermal efficiency.