Comparative upgrading of arab light vacuum residuum via aquaprocessing and thermal cracking
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AbstractPetroleum residua upgrading via thermal processes is restricted to low conversions due to asphaltene stability limitations. The high cost of hydroprocessing that requires high hydrogen flow and pressure affects the economics of upgrading residual oils. New economic means for upgrading these heavy oils are thus becoming increasingly important. In this work, a novel method, referred to as Aquaprocessing, for upgrading Arabian Light vacuum residue under asphaltenes stability limits by steam catalytic cracking using unsupported Ultra-Dispersed (UD) alkali and a non-noble transition metal catalyst is proposed and investigated in a continuous open tubular reactor pilot plant. Aquaprocessing advantageously dissociates steam over the catalyst into oxygen and hydrogen radicals and promotes their addition to the simultaneously cracked residual oil radicals produced near visbreaking temperatures. The Aquaprocessing experiments are conducted with K/Ni UD catalyst under 260 psig at process temperatures of 430-445 °C and LHSV of 5-10.5 hr⁻¹. Experimental results showed a significant relative increase in the residual oil conversion of 13% by Aquaprocessing at the minimum asphaltenes stability limit when compared to conventional thermal cracking. Using 018 labeled water it is shown that the UD catalyst under high temperatures is capable of dissociating water molecules into hydrogen and oxygen radicals of which oxygen radicals are retrieved in the CO2 of the produced gases. Furthermore, a kinetic model for the upgrading of Arab Light vacuum residue (ALVR) by Aquaprocessing is proposed and investigated in this work. The proposed model is based on five cascaded lumps, which are 540 °C+ residue, VGO (455-540 °C), distillates (204-455 °C), naphtha (IBP-204 °C), and gases. The model fits the experimental values for all components with a mean absolute percentage error of less than 5.5%. Removal of asphaltenes by means of adsorption over low cost adsorbents is also considered an economic way to further upgrade residual oils processed via either thermal cracking or Aquaprocessing. In the final part of this thesis a study of adsorption kinetics and uptake of produced asphaltenes from thermal cracking and Aquaprocessing of Arabian Light vacuum residue (ALVR) over macroporous Ca-kaolin and Ba-Ca-kaolin is performed. Obtained results are compared with adsorption results reported for Athabasca vacuum residue (ATVR) and model molecules over the same modified kaolin. Results show faster adsorption from ALVR at increased conversion severities but lower uptake over C-kaolin. AL YR C7 asphaltenes shows highest adsorption kinetics and uptake when compared to model molecules and ATVR C7 asphaltenes. An upgrading integrated process that combines Aquaprocessing and adsorption is suggested for an improved residua upgrading and conversion based on the experimental findings from this research.
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