Abstract: In order to produce a carbon solid solution or carbide-containing surface layer on a substrate, the substrate is immersed into a cold bath of liquid active medium, and heated inside the liquid active medium by heating means immersed in the liquid active medium as well.

Abstract: For cooling food products in a container, an apparatus is provided which includes a supply structure for supplying liquid carbon dioxide into the interior of the container and discharging liquid carbon dioxide in the interior to form a carbon dioxide flow, and also has a withdrawing structure for withdrawing carbon dioxide vapors generated in the container and moving them in the vicinity of the supplying structure, so that cold of the carbon dioxide vapors is transferred to liquid carbon dioxide supplied by the supplying structure.

Abstract: A method of and an apparatus for heating, melting and production of gaseous fuel include supplying air, coal, steam into a melt. The melt contains elements readily oxidized by air. These elements produce oxides readily reduced by carbon. The overall results of the reactions of elements oxidation and reduction consist in the production of CO containing gas and evolving heat. The heat evolved is extracted from the melt by submergence of solid to be heated into the melt, by injection of heated gases into molten slag, by heat exchange between the wall confining the melt and gas, liquid or solid to be heated, or by conversion of steam into H.sub.2 and CO.