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Biocracking of Heavy Fuel Oil (Mazut) By Native Microorganisms

Chackoshian Khorasani, Alireza | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43032 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical & Petroleum Engineering
  6. Advisor(s): Yaghmaei, Soheila; Mashreghi, Mansour
  7. Abstract:
  8. Biocracking mazut by native capable microorganisms and practically modeling it is one of the new perfect fields of biotechnology in petroleum manufacture. Sampling soil and water sources polluted by petroleum compounds, has caused a new bacterial strain of Enterobacter cloacae (BBRC 10061) has been identified and isolated from soil in Mashhad contaminated by petroleum wastewater and mixture to biodegrade mazut. Using mixed culture isolated from the sources instead of BBRC 10061 makes same results. In aerobic condition, 13% of mazut in mineral medium has degraded for 10 days however amount of degraded mazut varies with process conditions. Study of fixing and floating mazut, application of gradual adding mazut and use of fixed and moving bed show floating mazut and inhibiting from sticking of mazut into bioreactor's wall causes increase in process yield. Gradual addition of mazut adapts microorganism to condition and occasions processing with most of possible microorganisms and finally mazut degradation occurs 10% more. Using fixed and moving bed don't make different result although probably cracking of mazut increases in moving bed condition because of raising homogenization and dissolved oxygen in this condition. Increasing mazut concentration causes increase in degraded mazut however percentage of degradation decreases. Decrease of percentage of degradation isn't linear indeed it progressively decreases by increasing concentration; so that in very high concentrations change of concentration doesn't effect on degraded mazut. Measuring changes of pH and electric potential during process show ordinarily degradation of mazut occasions decrease in pH and increase in electric potential. To optimization of mazut degradation by Taguchi method, 7 variables of amount of microbial inoculation, initial pH, surfactant, glucose, phosphor source, nitrogen source and sea salt each them with 4 levels and variable of microorganism type with 2 levels were chosen. Multi-stage experiments were run during 10 days that one stage was 2 days and results showed time turned optimized conditions so that can't expect equal yields at different times from a process is optimized in certain time.
    To select proper kinetic model for mazut biodegradation, various models were assessed but none of them were capable to predict and model process under whole given experimental conditions. Ratio of specific mazut degradation rate to specific microbial growth rate is defined as Dimensionless number of Ch that is as reaction of environment and secondary agents to direct system into cracking mazut. Process of biodegradation of mazut under whole given experimental conditions in this study was modeled based on this number. Ch number based on time can properly predict biocracking of mazut, changes of pH and electric potential in whole conditions by 4 order power function. Expect that this model can satisfyingly predict all phenomena limited by time
  9. Keywords:
  10. Indigenous Microorganism ; Optimization ; Modeling ; Taguchi Method ; Mazut

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