THE INORGANIC GEOCHEMISTRY OF COAL, PETROLEUM, AND THEIR GASIFICATIONCOMBUSTION PRODUCTS/

The inorganic makeup of coal and petroleum differ in several crucial w ays. The origins of these differences include the disparate geologic e nvironments of formation, the contrasting parent materials (plant vers us planktonic) and hence distinct organic species, and the physical st ate of the fuels (solid versus liquid). The inorganic chemistry of pet roleum is usually controlled by the type and abundance of its organic compounds (i.e., V, Ni, +/- Fe-bearing porphyrins and S-bearing thiols , sulfides, disulfides, thiophenic derivatives, resins, and asphaltene s), with significant, though often smaller contributions from entraine d mineral phases. This near balance of inorganic compositional control causes petroleum to form combustion/gasification (pyrochemical) slag and ash with a large number of elements (i.e., V, Ni, S, Fe, Ca, Na, K , Mg, Si, and Al) in significant relative concentrations. This balance provides also opportunities for large departures from any given ''nor m''. The inorganic chemistry of coal, on the other hand, is dominantly controlled by its contained detrital and authigenic mineral matter, w ith relatively small contributions from organically carried elements o ther than sulfur. Detrital minerals are those that survive the geologi cal processes of weathering and transport, and hence are a small group of physically resistant and chemically stable minerals including quar tz, clay minerals, and oxides of Fe and Ti. The most abundant authigen ic minerals in coal include clay minerals, pyrite/marcasite, carbonate s, Ca- and Fe-sulfates, and Fe-oxides and hydroxides. Pyrochemical sla g and ash from coal are therefore primarily enriched in Si, Al, Ca, Fe , and S. From a processing standpoint, the behavior of slag and fly as h is largely a function of the complexity of the fuel's inorganic chem istry (including the original mode of occurrence of the various elemen ts), and the observed oxygen fugacity. Pyrochemical environments vary from reducing to oxidizing as a result of proximity to the flame and o perational mode (combustion versus gasification). Consequently, multiv alent elements further contribute to the complexity of slag/ash behavi or by essentially behaving as separately unique elements when in their various valence states. In coal, the two abundant, multivalent inorga nic elements are Fe(O, + 2, and + 3) and S(- 2, 0, + 2, + 4, and + 6). In petroleum there are four abundant, multivalent inorganic elements: Ni (0 or + 2), Fe (0, + 2, and + 3), V (+ 2, + 3, + 4, and + 5), and S ( - 2, 0, + 2, + 4, and + 6). The larger number of abundant inorgani c elements in petroleum than coal, as well as the broader range of ass ociated valence states, leads to more diverse slag/ash species formed during petroleum combustion/gasification, and consequently less predic table slag/ash behavior. A phase characterization of slags produced by the gasification of petroleum coke (a petroleum refining byproduct) i llustrates their increased complexity with respect to typical coal sla gs.