The Demineralization of Coal Using Selective Agglomeration by the T-Process

Abstract

The demineralization of coal by selective agglomeration using pentane as an agglomerant which has been called the "T-process" involves two steps: first, the raw coal is reduced to some particle size smaller than 0.5mm. And secondly, the fine coal is recovered from a dilute raw coal water slurry by the dispersion of pentane in the slurry. The pentane envelopes the coal particles which allows the formation of liquid bridges between the coal particles that results in a water immiscible mass of coal and pentane. The latter is separated from the dispersed mineral matter in the water phase by some simple mechanical procedure. The coal recovery from very fine raw coals is normally in excess of 95%. The penrane is recovered by evaporation/condensation for reuse in the process leaving the demineralized coal for utilization either as a slurry or as dry pellets. Pilot operations using this process have produced over 125 tons of pyrite-free product coal with an average ash content in the range of 0.8 wt %.A detailed discussion of the extent of mineral release during comminution is coupled with examples of deashing of raw coals into the range below 0.3 wt % ash and over 95% pyrite extraction from typical steam coals. The salient points of the relationship between particle size distribution and mineral release are established.The broad applicability of selective agglomeration with pentane to the mineral separation from over 100 different seams of coal is illustrated. The stable gas content in a milled slurry was related to the agglomeration timedata for thirty different seams ofcoal. The relationship from those data suggested that the degree of hydrophobicity ofthe coal surkce of the particles was the common Factor.The processing costs are estimated to be in the range of $0.60 per million BTU.

Desulfurization and Deashing of Hazro Coal by Selective Oil Agglomeration in Various Water Mediums

“…5,6 One of the more promising methods for cleaning coal involves suspending finely ground coal in water and selectively agglomerating the more hydrophobic and oleophilic components with oil or low-molecular-weight hydrocarbons such as pentane or heptane as the suspension is agitated vigorously. [7][8][9] The organic macerals tend to be agglomerated in preference to the inorganic minerals. Dependent upon their relative size and density, the agglomerates can be recovered from the suspension by floating, skimming, or screening.…”

“…One of the more promising methods for cleaning coal involves suspending finely ground coal in water and selectively agglomerating the more hydrophobic and oleophilic components with oil or low-molecular-weight hydrocarbons such as pentane or heptane as the suspension is agitated vigorously. − …”

A Kinetic Study of a Modified Fine Coal Agglomeration Process

“…Agglomeration of fine coal presents many advantages over the other processing technologies available, and for this reason a number of coal preparation processes were developed which utilized this technique including: the Trent process [8], the Convertol process [9], the spherical agglomeration process [10] and the Otisca-T process [11]. However, effective as they were, none of the above technologies were successful in maintaining a long-term and viable application.…”

Ultrafine Coal Cleaning Using Selective Hydrophobic Coagulation

“…The coal particles flocculate due to the hydrophobic interactions between the polymeric chains and the coal surfaces [2,3]. Oil or other organic liquids such as pentane can also be utilized to selectively agglomerate ultrafine coal [4,5]. Research conducted on laboratory and pilot-scale processes indicate that clean coal products containing less than 2% ash can be achieved by oil agglomeration with high levels of energy recovery.…”