Peroxide-Acid for High SUlphur Coals

1 4 0 LOWERING THE SUL FUR A N D ASH CONTENTS O F HIGH-SULFUR COALS BY PEROX IDE-ACID TREATMENT E . B. Smith Energy Research and Development Administration Laramie Energy Researc h Center, Larami e, Wyoming 82071 I NTRODUCTIO N Considerable effort has been devoted in recent years to upgrading high-sulfur coal s by both phys ical and chemical met hods . Som e met hods are mild, sele ctiv ely removing minera l c m- ponents without significantly a lt ering th e organic matter. The more drastic met hods break down the coal structure, separating i t into an inorganic sludge and an organic product essentially not coal. As a recently publicized example, high-g radient magnetic separation has been propose d a s a techniqu e f or removing pyrite and other weakly paramagnetic minerals from slurried coal.' The Bu reau of Mines' froth flot at ion process2 remove s p yrite and other minerals by taking advantage of differences in densit y and w et tability of these undesirable substances and organi c material. A method known as Meyer's Process3 involves up to six leaches of pulverized coal with ferric salt solution at about looo converting pyrit e to sulfate and elemental sulfur. A more vigorous chemical met hod4 requires leach ing fi nely pulverized coal with aqueous al kali at about 225' C i n a closed sy st em under an inert atmosphere, followed by treatment with strong acid and leaching wi th water, The still more vigorous PAMCO process5 involves dissolution of coal i n solvent a t elevated temperature, hydrogen treatment, physic al separation of undi:solved mat ier , and vacu um disiiiiaiion of the dissolved products. Our laboratory i s investigating methods for upgrading shal e oi l and high-sulfur coal by m il d oxidation. Curr entl y, experiments are being conducted with two types of oxidation syst ems-- one using o xyge n, whi ch shows promise a s a method for upgrading shal e-oil distillates,6 and the other using mixtures of H202 and aci d, which may be useful for upgrading both shale oi l and coal. This report desc ribes results of treating several h igh-su lfur coals wi th solutions of H202 i n H2SO4, or with H2SO4 alone. Acid concentrations ranged from 0.1 E o 0 .5 ! H202 concentrations ranged from 7 to 17 percent, and tr eat ing periods ranged from 1 t o 7 2 hours. Most o f the tes ts were conducted at ambient temperature, but i n one test serie s, the solutions were warmed to spee d up the reaction. EXPERIMENTAL PROCEDURES Coals and Sample Preparation Five different high-sulfur, high-volatile bituminous coal s, representing a wide range of sulfur contents, sulfur types, an d ash c ontents , were obt ain ed fro m the Pittsburgh Ener gy Rese arch Cent er. These were (A) Pittsburgh Seam, St. Clairsville, Ohio; (B) Pit tsb urg h S e am, Pittsburgh, Pennsylvania; ( C ) Illinois No. 5 Bed; (D) Hastie , Io wa B e d ; a nd (E ) F t . Scott, Oklahoma Bed. Each co al as rec eived was first screened through a 32- mesh screen to separate fine and coarse mot eri al. Th e plus 32-mesh mat er ia l was crushed i n a ceramic mill jar with Burundum cylinders; that wh ich p as sed through the 32-mesh screen wa s combined wit h the ini ti a ll y separated fi ne material, and the plus 32-mesh material was returned to the mill iar for further crushing. This process was repeated until the entire sample was reduced to minus 32 mesh.

Peroxide-Acid for High SUlphur Coals

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