RETRACTED: Modern design solutions in the design of boiler units, ovens and fireboxes burning solid fuel in a fluidified bedI.I. Feoktistov, D.S. Kovalev, M. Shaikh and D.A. ChechetkinBIO Web Conf., 84 (2024) 05011DOI: https://doi.org/10.1051/bioconf/20248405011