Bitumen heavy oil upgrading by cavitation processing: effect on asphaltene separation, rheology, and metal content

Abstract

Cavitation processing has been proposed as a greener alternative to solvent dilution or heat treatment of bitumen and other heavy oils to reduce viscosity and hence, improve transportability. The effect of acoustic cavitation under different conditions of sonication frequencies (lowto high-frequency range) and power inputs on asphaltene content, rheological changes, and metal content of bitumen was investigated in this study. Ultrasonic treatment resulted in a decrease in asphaltene content in bitumen that lead to lower viscosity and shear stress over a wide range of shear rates. Over the range of sonication frequencies investigated (20 kHz-1.1 MHz), the sonication frequency of 574 kHz with 50 % power input resulted in low asphaltene content and lower viscosity suitable for improved transportability. Further, comparison of different conditions of sonication frequencies and power inputs were carried out to investigate the effect of ultrasound on properties of asphaltene (elemental analysis and metal content). It was observed that the sonication treatment of bitumen under different conditions of frequencies and acoustic power decreased the H/C ratio. These results showed higher content of aromatic hydrogen and lower content of aliphatic hydrogen in bitumen treated under different conditions of sonication frequencies and intensity. Characterization of asphaltene performed using ICP-MS and TXRF, revealed lower metal content (Ni, Fe, and V) in the asphaltene phase of processed (sonicated) bitumen. The lowered metal content can be attributed to the reduced asphaltene formation as a result of sonication treatment of bitumen.

Effect of ultrasound irradiation on asphaltene aggregation and implications to rheological behavior of bitumen

“…5 a). Similar results were reported by Mohapatra and Kirpalani (2016), who argued that sonicating a Canadian Bitumen at a frequency as high as 378 kHz could lower the viscosity of the oil up to 15% from its original value [28] .…”

“…As per the same author, the primary challenge is the relatively limited range of ultrasonic radiation (up to 2 m) at the operational resonance frequency, which usually ranges from 20 to 40 kHz [26] . This is to say that this method still suffer from deeper understanding to make meaningful and consistent scientific elaborations despite the wealth of papers covering the topic [27] , [28] , [29] , [30] , [31] , [32] , [33] .…”

Towards the development of cavitation technology for upgrading bitumen: Viscosity change and chemical cavitation yield measurements

“…Chemical effects are recognised to be dominant at low frequency (Suslick et al 1999), while physical effects are dominant at high frequency as it requires very high energy input to generate cavitation at high frequencies. Change in viscosity occurs due to intense shear or tensile force within the fluid (Mohapatra and Kirpalani 2016). This shear is caused by physical effects such as microconvection, and microstreaming or microstirring.…”

Towards the development of cavitation technology for gas hydrate prevention

“…The sonication treatment of asphalt can decrease the H/C ratio under different power inputs and frequencies. Characterization of asphaltene revealed that reduced or retarded asphaltene formation can lower the metal content in bitumen [26]. Flannigan & Suslick [31] discovered the sonoluminescence of a single bubble in sulfuric acid, and plasma was detected during the cavitating process.…”

“…On the contrary, when the frequency is relatively high, the physical effects surpass the chemical impacts, and tiny emulsion droplets are visible between an immiscible interface that lowers or eliminates the resistance of mass transfer [25]. The tensile force or shear effect caused by physical effects can reduce the fluid viscosity [26,27]. AC has a relatively wide application among industries, with the disadvantage of a high power requirement.…”