Oxy-fuel combustion of Refuse Derived Fuels (RDF) under cement kiln conditions
The objective of the Oxyflame Project T1 is to transfer the oxy-fuel knowledge gained in the CRC/TRR Transregio 129 Oxyflame for power plants to the cement production process in cooperation with an industrial partner (thyssenkrupp Industrial Solutions). In modern cement plants, pulverized coal is more and more replaced by low-cost waste-based refuse-derived fuel (RDF). The size of the RDF particles is in the centimeter range, physical and chemical properties are very heterogeneous: In addition, oxygen concentrations in future oxy-fuel cement plants are significantly higher than in power plants. This requires an extension of the models and experimental database already generated by Oxyflame. This task will be tackled by the three project partners, WSA, LEAT and thyssenkrupp Industrial Solutions.
At the WSA, the modeling of the reaction kinetics, as well as the radiative heat transfer, will be addressed. The fluidized bed reactor developed in project A1 will be used to derive the data for kinetic models of pyrolysis, gasification and char burnout. For radiation, the models derived by project C4 will serve as a starting point. In order to account for the different sizes and compositions of RDF fractions compared to coal or biomass, the particle radiation will be studied with numerical simulations to expand the current model to the new fuel.
The LEAT uses a single-particle reactor to investigate the combustion behavior of RDF at different oxygen concentrations. The combustion process is recorded by two stereoscopic arranged cameras to determine the duration of different combustion regimes (e.g., volatile combustion and char burn-out). These time scales are measured for different oxygen concentrations. The results from these investigations are used to extend and calibrate the existing RDF combustion models for oxy-fuel combustion.
Subsequently, simulations of a generic kiln and burner set-up (developed by thyssenkrupp Industrial Solutions) are carried out with the new RDF oxy-fuel combustion models and the advanced radiations models provided by WSA. Burner operational settings and RDF properties will be varied. The terminal goal of the project is to provide a simulation tool to predict heat release, heat transfer, RDF particle trajectories, fuel burnout and cement clinker product quality in oxy-fuel rotary cement kilns.