One of the ways to increase the efficiency of high temperature processes in pelletisation of metallurgical materials is to optimise the composition and height & width of the protective ‘hearth layer’, the use of which is intended to increase the service life of the grate bars of straight-grate induration machines. In the present paper the authors present the data of the research on the replacement of the bottom “hearth layer” with limestone and briquettes, which allows to reduce the amount of recycled product and to increase the useful utilisation of the working volume of an indurating machine. Replacing the hearth layer material with the fine fraction of limestone improves the protection of the grate bars from the effects of temperature and increases the production rate of a straight-grate induration machine. By using briquettes in pellet induration instead of a protective “hearth layer”, the potential increase in the production rate (output) of merchant grade products is up to 25%.