Emission Characteristics During the Co-Firing of Fine Coal and Refuse-Derived Fuel from Municipal Waste

The co-firing of coal and refuse-derived fuel (RDF) from municipal solid waste recycling is gaining support in countries in which energy production is based on solid fuels. It is the result of the rising priority given to renewable energy sources, the circular economy, and effective waste management through sorting, recycling, and thermal conversion. Despite the increasing efficiency of recycling and the ever-lower quantities of waste delivered to waste dumps, the problem of the residual fraction remains unsolved. The portion of mixed municipal waste that cannot be recycled exhibits a high energy value. For this reason, it should be neither stored nor burnt in household boiler rooms, as doing so would constitute an environmental hazard. However, the waste can be used as an additive to fine coal in power boilers, provided that they are equipped with flue gas monitoring and purification systems. Tests involving proportionally prepared compositions of fine coal and refuse-derived fuel burnt in a laboratory boiler revealed a major variability in the flue gas parameters (physicochemical), depending on the applied proportions of the individual components. For instance, when burning a composition of 50% fine coal and 50% refuse-derived fuel, a reduction in CO2 emissions by about 12% was noted compared with that when burning fine coal exclusively. Furthermore, when burning refuse-derived fuel, an addition of 20% fine coal is enough to produce a 2.8% reduction in CO emission. Meanwhile, a composition of 80% fine coal and 20% refuse-derived fuel would reduce the emissions by 393 ppm. During the measurements, it was also noted that most of the measured parameters indicated a decrease in individual gas contents relative to the emissions obtained when burning fine coal or refuse-derived fuel exclusively. These relationships can be applied to prepare fuel compositions based on refuse-derived fuel and fine coal, depending on the power and flue gas purification capabilities of individual cogeneration systems.