A combustion process wherein a fuel, a comburent and component A) are fed to a combustor, component A), comprising low-melting salts and/or oxides having a melting temperature 1,450 K, the ratio by moles A/(AA)0.01, being: A the sum by moles between the amount of metals, under the form of low-melting salts and/or low-melting oxides present in the component A) and the amount of metals under the form of the low-melting salts and/or low-melting oxides or their low-melting mixtures, contained in the fuel, A is the sum of the amount of all the metals contained in the fuel and of those contained in component A), in which the combustor is isothermal type and flameless.

A method of inhibiting vanadic corrosion of a hot part of a gas turbine system is provided. The method includes introducing, in the combustor, a first oxide comprising magnesium oxide (MgO) and at least one second oxide from among Al.sub.2O.sub.3, Fe.sub.2O.sub.3, TiO.sub.2 and SiO.sub.2. A ratio m of a number of moles of MgO to a number of moles of V.sub.2O.sub.5 and a ratio a of a total number of moles of the at least one second oxide to the number of moles of V.sub.2O.sub.5 satisfy two conditions based on a firing temperature of the expansion turbine, an average density of one or more double oxides formed by a reaction between MgO and the at least one second oxide, and an average Knoop hardness of the one or more double oxides formed by the reaction between MgO and the at least one second oxide.

A solid biomass fuel derived from one or more sources of biomass, wherein the one or more sources of biomass comprise: straw, palm-derived material, nut shells, hemp, bamboo, corn cob, rice husk, fruit shells, crop residues, seaweed, calliandra calothyrsus, acacia mangium, albizia chinensis, hevea brasiliensis, grass, or any combination thereof: wherein the solid biomass fuel further comprises one or more aluminosilicate-containing clays, one or more aluminosilicates, one or more pulverised fuel ashes, or a combination thereof.