NOVELTY - A feed material (M1) for a gasifier (12) comprises a hydrocarbon; and an additive (10), where the additive comprises a ferric oxide, a magnesium oxide, and/or a manganese oxide. The feed material is adapted to form liquid slag comprising at least 15 wt.% of ferric oxide, magnesium oxide, and/or manganese oxide.    USE - As feed material for a gasifier, where the feed material comprises coal, petroleum, coke, or biomass (claimed); and for furnaces, and other high-temperature vessels.    ADVANTAGE - The additives at least partially reduces the infiltration of slag into the refractory material and also reduces the penetration of liquid slag into the lining of the gasifier. When the additives enter the reaction area of a gasifier and are subjected to high temperatures, the mixture of slag and slag additives react with the outer layers of the refractory material to form surface reaction layers that prevent deeper slag penetration into the refractory material. Formation of the protective layer limits penetration of the liquid slag beneath the product layer and hence limits the depth of the zone in which degradation of the refractory brick by cracking and spallation, grain extraction, and/or dissolution, can occur. The rate of recession of the brick is reduced and its useful life increased by limiting the slag/brick reaction depth. An additional advantage provided by the additives is that the formation of the spinel layers or other protective layers can be continuous during the operation of the gasifier, as the additives can be continuously be fed into the reactor. Thus, the use of the feed material is cost effective, both in terms of the materials and labor involved and it does not create operating time lost.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) process for operating the gasifier involving: providing the feed material M1 in an input stream to the gasifier; and operating the gasifier at a temperature higher than the melting temperature of the slag such that the feed material forms the liquid slag;    (2) a structure comprising: a refractory material; and a protective layer formed on the refractory material comprising iron, magnesium, or manganese; and    (3) modifying the feed material for a gasifier involving: determining the concentration of iron, magnesium, and/or manganese, in a hydrocarbon; and providing the additive comprising ferric oxide, magnesium oxide, and/or manganese oxide, such that when the additive is mixed with the hydrocarbon and exposed to a temperature higher than the melting temperature of the additive, a liquid slag comprising at least 15 wt.% of ferric oxide, magnesium oxide, and/or manganese oxide, is formed.    DESCRIPTION OF DRAWING(S) - The figure shows a view of an exemplary coal gasifier.    Coal additives (10)    Coal gasifier (12)    Lining of refractory material (14)    Reaction space (15)    Coal line (16)