GB926213A - Improvements in and relating to the production of physically strong carbonaceous material from coal - Google Patents

Abstract

In a process for producing physically strong briquettes or the like from any rank of coal, finely divided coal particles are heated to a temperature below that at which the distillate vapours evolved condense as tar and above that at which moisture is evolved in an atmosphere which in the case of high oxygen-containing coals need not contain added oxygen, in the case of non-coking coals contains from 1 to 8% by volume of oxygen, and in the case of coking coals contains from 8 to 20% by volume of oxygen, for a time sufficient to produce catalysed coal particles conditioned so that in a subsequent healing stage the hydrocarbonaceous matter is reduced and wherein the catalysed coal particles are rapidly heated in a fluidised bed to a higher temperature at which they are maintained for a time sufficient to evolve vapours and produce a char having a volatile matter content substantially less than that of the parent coal, the char being then calcined until the content of volatile matter is reduced to not more than 3% by weight. The initial treatment may be carried out with the coal particles in a fluidized bed or a dispersed phase. When the coal is a non-coking coal the coal particles may be heated to between 250 DEG and 500 DEG F., for a period of at least 5 minutes and up to 180 minutes. In the case of a coking coal the temperature may be maintained at between 500 DEG and 800 DEG F. for a period of at least 5 minutes and up to 180 minutes. Alternatively higher temperatures and shorter periods of treatment may be employed for both coking and noncoking coals. Heat for the treatment may be supplied by indirect heat exchange, partial combustion or by heating the fluidising or carrier gas. The catalysed coal particles are heated to a temperature between 800 DEG -1200 DEG F. for coking coals and 500 DEG -1200 DEG F. for non-coking coals. for a period of between 10 and 60 minutes and the char is heated, preferably in a fluidized bed with a fluidized medium free from carbon di-oxide, steam and oxygen, to a temperature between 1400 DEG -1800 DEG F. for a period of at least 7 minutes but not exceeding 60 minutes. The calcined char may be mixed with a bituminous binder after first being cooled to a temperature of from 30 DEG to 60 DEG F. above the softening point of the binder and briquetted, the briquettes being cured in an atmosphere containing at least 2,5% and up to 21% by volume of oxygen for a period of 90 to 180 minutes and at a temperature between 450 DEG -500 DEG F. The curing of the briqettes may be enhanced by incorporating in the briquettes or effecting the curing in the presence of reagents such as boran trifluoride, aluminium chloride, hydrogen peroxide and phosphoric acid. The carbonaceous binder for the briquettes may be produced from the tar evolved during carbonization of the catalysed coal particles. The separated tar is dehydrated to contain not more than 0,5% by weight of water and blown with air or steam until 5% of the lighter fractions have been removed. Catalysts may be incorporated in the tar during the blowing and may be organic persades, e.g. benzoyl persade, or inorganic substances such as sulphuric acid, boron trifluoride or aluminium chloride. The amount of catalyst used may be between 0,1% and 2% by weight. A suitable mixture for briquetting may comprise 75%-90% calcined char and 25-10% binder.