Oil Separation from Contaminated Condensates WithFuel in Power Plant by Flotation &Solvent Sublation

Hosseinzadeh, Hossein | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42496 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): shaygan, Jalaloddin; Jalali, Morteza
  7. Abstract:
  8. Some of the thermal power plants use heavy fuel oil as an auxiliary fuel instead of the fuel gas, especially in the cold seasons. In these plants, in order to reduce fuel viscosity, heavy fuel oil is heated in several stages including fuel storage tank, connection lines and oil supply to burner by heat exchange with returned steam from the turbine, which can lead to fuel leakage into the condensates. This contamination is in addition to the contamination that has resulted from leaking seals on steam driven equipments, such as pumps and turbines. Reusing these contaminated condensates as boiler feed water can lead to coking of hydrocarbons and deposition of a hard scale on boiler tube walls. Consequently, reduction of heat transfer caused by scales will lead to higher fuel costs and rupturing of the tubes at excessively high metal temperatures. Due to the high cost of producing deionized water by ion exchange and reverse osmosis, the reuse of these condensates after oil removal is required.
    In this research, at first all conventional methods for separating oil from water were studied, technically and economically. Then, due to the advantages of the dissolved air flotation units in treatment of oily wastewaters and in order to investigate its performance for the treatment of contaminated condensates, a bench scale dissolved air flotation column was constructed. Water solubility of heavy fuel oil in water is low, but this low amount is more than the feed water limits for industrial water tube boilers. The conventional dissolved air flotation systems will not be able to reduce the concentration of oily matters below the permitted limits. Therefore, in order to enhance system performance to removal of soluble and tiny emulsion oils, effects of the process of solvent sublation and also adding of different doses of coconut and walnut shell based powdered activated carbons were investigated. According to the results of these experiments, we can expect by using a dissolved air flotation unit, the oil and grease concentration after 10 and 120 minutes, can be reduced from about 15 mg/lit to about 5 and 1 mg/lit, respectively.
  9. Keywords:
  10. Power Plants ; Activated Carbon ; Fuel Oil ; Dissolved Air Flotation ; Solvent Sublation System ; Powder Activated Carbon

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