Considering the imperative reduction in CO2 emissions, both from household heating and hot water producing facilities, one of the mainstream directions is to reduce hydrocarbons in combustibles by replacing them with hydrogen. The authors analyze condensing boilers operating when hydrogen is mixed with standard gaseous fuel (CH4). The hydrogen (H2) volumetric participation in the mixture is considered to vary in the range of 0 to 20%. The operation of the condensing boilers will be numerically modeled by computational programs and prior validated by experimental studies concluded in a European Certified Laboratory. The study concluded that an increase in the combustible flow with 16% will compensate the maximum H2 concentration situation with no other implications on the boiler’s thermal efficiency, together with a decrease in CO2 emissions by approximately 7%. By assuming 0.9 (to/year/boiler), the value of CO2 emissions reduction for the condensing boiler determined in the paper, and extrapolating it for the estimated number of boilers to be sold for the period 2019–2024, a 254,700-ton CO2/year reduction resulted.

Following the international trend of using hydrogen as combustible in many industry branches, this paper investigates the impact of mixing methane gas with 23% hydrogen (G222) on condensing boilers’ operation. After modeling and testing several boilers with heat exchange surface different designs, the authors gathered enough information to introduce a new concept, namely High-Performance Condensing Boiler (HPCB). All the boilers that fit into this approach have the same operational parameters at nominal heat load, including the CO2 concentrations in flue gases. After testing a flattened pipes condensing boiler, a CO2 emission reduction coefficient of 1.1 was determined when converting from methane gas to G222 as combustible. Thus, by inserting into the national grid a G222 mixture, an important reduction in greenhouse gases can be achieved. For a 28 kW condensing boiler, the annual reduction in CO2 emissions averages 1.26 tons, value which was experimentally obtained and is consistent with the theoretical evaluation.

Carbon dioxide footprint reduction can be reached by switching fossile combustible consumers to biogenic fuels. Using biogenic fuels, mainly cellulosic ones, requires burner replacement and most often a complete change of burning process by introducing pre-burning chambers. The boiler response is also to be studied because the changes in flue gases composition, debits and temperatures. The paper analyses the necessary burning installation retrofitting for the case of switching a local boiler from gaseous fuel functioning to cellulosic fuel functioning (sawdust or pellets). It is presented a calculation method for boiler functioning verification (determining the functioning parameters considering an existing boiler used in other than nominal conditions) with the aim of determining the parametrical and performances variations when using other fuels. The nominal functioning regime, for witch there are available experimental data, is used to validate the model and the computational program. Conclusions are drawn regarding the possibility and results for retrofitting regional heating boilers from gaseous to biogenic fuels.

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