Abstract: In a process for improving coal wherein the raw coal is treated with a metal containing compound in order to enhance the magnetic susceptibility of certain impurity components contained in the raw coal permitting their removal by magnetic separation, the improvement comprising pretreating the coal by heating it to at least a temperature for at least a period of time sufficient to essentially meet or exceed a time and temperature relationship expressed as:D .gtoreq. K[50/T-90].sup.3wherein D is time in hours and T is temperature in degrees Celsius, and wherein K is preferably at least about 0.5, more preferably at least about 5, and most preferably at least about 25.

Abstract: In a process for improving coal containing elemental sulfur wherein the coal is treated with a metal containing compound in order to enhance the magnetic susceptibility of various impurities contained within the coal thereby permitting their removal by magnetic separation, the improvement comprising removing at least a portion of the elemental sulfur prior to performing the magnetic susceptibility enhancement treatment.

Abstract: The magnetic susceptibility of various impurities contained within coal is increased by simultaneously cotreating the coal with a metal containing compound and a gas selected from the group consisting of hydrogen and carbon monoxide.

Abstract: Coal particles are made resistant to spontaneous combustion by coating them with silicon dioxide by a vapor deposition process in which the particles in a coating chamber are contacted at a temperature that promotes the deposition on the particles of the reaction products between silicon tetrachloride vapor and water, the coating step followed by elevating the chamber temperature to drive off water vapor and hydrochloric acid.

Abstract: A process for improving coal wherein the raw coal is reacted with substantially undecomposed iron carbonyl which alters the apparent magnetic susceptibility of certain impurity components contained in the raw coal thereby permitting their removal by low intensity magnetic separators. The process is especially effective for removing pyrite from coal, while at the same time reducing ash and increasing the calorific value.