This invention relates to a method of preparing a pitch-in-water slurry.
As a result of the decrease of high petroleum crude oils in recent years, a need was increased for converting heavy, poor quality hydrocarbon oils into light hydrocarbon oils. Thus, a variety of petroleum refining plants have been constructed for the conversion of heavy oils into light oils by a solvent deasphalting method, a thermal cracking method, a catalytic cracking method or the like method. These processes unavoidably yield, as a by-product, pitch formed of extremely heavy hydrocarbon components. Since pitch has generally a lower content of ash and a higher calorific value than coal, it is desirable to utilize pitch as a fuel for various combustion installations. However, unlike liquid petroleum fuel, pitch is a solid at room temperature and, therefore, requires relatively high costs such as for transportation and storage. Further, since pitch in the molten state fails to exhibit a desired fluidity, it is not possible to use it as a fuel for combustion in a furnace wherein the fuel is pumped through pipes and sprayed from a burner nozzle.
In this circumstance, an attempt has been made to use pitch in the form of a slurry. Unlike solid or molten pitch, slurried pitch is easy to handle and store and, moreover, is able to be sprayed from a burner nozzle for combustion. In order to prepare a pitch-in-water slurry, it is generally necessary to resort to a method which includes various steps such as cooling of molten pitch for solidification, comminuting solidified pitch into particles suitable for transportation, finely pulverizing pitch particles by wet grinding or by dry grinding and, if necessary, mixing the finely pulverized pitch particles with water. Such a method additionally requires various devices and installations such as belt conveyors and silos, for transportation and storage.