In the present work studies were performed to provide understanding for further model development of the two-phase phenomena, film formation from o/w emulsions and slag foaming. The drying of o/w emulsions of different oil viscosities on hydrophobic and hydrophilic substrates was studied. The hydrophobic substrate was found to destabilise the oil droplets and to result in a different mechanism for forming continuous oil film. Studies of adsorption behaviour of a series of non-ionic diblock copolymers at relevant interfaces showed that the adsorption behaviour at hydrophobic and hydrophilic solid surfaces differed at high polymer concentration. Emulsion droplets were found to interact with the hydrophobic interface. Adsorption at silicone oil-water interface resembled adsorption at solid hydrophobic surfaces. Gas was generated through chemical reaction at the interface between two immiscible liquids and the bubbles formation from the generated was studied optically. The gas bubble size was seen to be uninfluenced by the reaction rate. However, bubble formation was seen to take place in one of the phases, held up at the interface before detaching from the interface with a surrounding aqueous film. It was argued that this may affect the final bubble sizes. Slag foaming at high temperatures was studied in laboratory scale with X-ray imaging under dynamic conditions. The foam displayed a fluctuating behaviour, which the presently available models are not able to take into account. The concept of foaming index was found to be unsatisfactory in describing the foaming behaviour under dynamic conditions, thus emphasizing the need for alternative theories. The rate of fluctuations was seen to be related to the difference between rate of gas generation and rate of gas escape from the system (Ug-Ue) as well as the bubble sizes. Thus, it seems like model development of dynamic foaming phenomenon has to take the effective chemical reaction rate as well as the bubble sizes into consideration

No description available.

Electrochemical frequency modulation (EFM), which has been widely used in the research field of semiconductors, was used to study CO2 corrosion on carbon steel under film forming and non-film forming conditions. In the EFM technique two sinusoidal voltage signals of different frequencies are applied to the system and the response current is measured at zero, harmonic and intermodulation frequencies from which the corrosion rate is calculated. The corrosion rate calculation depends upon whether the system is under activation, diffusion or passivation control. In this research rotating cylindrical electrodes made of AISI carbon steel 1018 were immersed in 3% (w/w) NaCl solution saturated with carbon dioxide. The experiment was done at 5 rpm, 24 rpm and 100 rpm simulating laminar, transient and turbulent flow regions respectively. The exposure time was varied from 1 hour to 24 hours and the results were compared with other electrochemical methods such as linear polarization (LP) and electrochemical impedance spectroscopy (EIS). It was found that it was crucial to select the correct EFM model to ensure accurate corrosion rate measurement. A very good agreement in the polarization resistance was obtained between EIS and EFM indicating that EFM can be used as an effective tool in corrosion studies providing that the corrosion mechanism is known.

Electrochemical frequency modulation (EFM), which has been widely used in the research field of semiconductors, was used to study CO2 corrosion on carbon steel under film forming and non-film forming conditions. In the EFM technique two sinusoidal voltage signals of different frequencies are applied to the system and the response current is measured at zero, harmonic and intermodulation frequencies from which the corrosion rate is calculated. The corrosion rate calculation depends upon whether the system is under activation, diffusion or passivation control. In this research rotating cylindrical electrodes made of AISI carbon steel 1018 were immersed in 3% (w/w) NaCl solution saturated with carbon dioxide. The experiment was done at 5 rpm, 24 rpm and 100 rpm simulating laminar, transient and turbulent flow regions respectively. The exposure time was varied from 1 hour to 24 hours and the results were compared with other electrochemical methods such as linear polarization (LP) and electrochemical impedance spectroscopy (EIS). It was found that it was crucial to select the correct EFM model to ensure accurate corrosion rate measurement. A very good agreement in the polarization resistance was obtained between EIS and EFM indicating that EFM can be used as an effective tool in corrosion studies providing that the corrosion mechanism is known.

<p>In the present work studies were performed to provide understanding for further model development of the two-phase phenomena, film formation from o/w emulsions and slag foaming.</p><p>The drying of o/w emulsions of different oil viscosities on hydrophobic and hydrophilic substrates was studied. The hydrophobic substrate was found to destabilise the oil droplets and to result in a different mechanism for forming continuous oil film. Studies of adsorption behaviour of a series of non-ionic diblock copolymers at relevant interfaces showed that the adsorption behaviour at hydrophobic and hydrophilic solid surfaces differed at high polymer concentration. Emulsion droplets were found to interact with the hydrophobic interface. Adsorption at silicone oil-water interface resembled adsorption at solid hydrophobic surfaces.</p><p>Gas was generated through chemical reaction at the interface between two immiscible liquids and the bubbles formation from the generated was studied optically. The gas bubble size was seen to be uninfluenced by the reaction rate. However, bubble formation was seen to take place in one of the phases, held up at the interface before detaching from the interface with a surrounding aqueous film. It was argued that this may affect the final bubble sizes.</p><p>Slag foaming at high temperatures was studied in laboratory scale with X-ray imaging under dynamic conditions. The foam displayed a fluctuating behaviour, which the presently available models are not able to take into account. The concept of foaming index was found to be unsatisfactory in describing the foaming behaviour under dynamic conditions, thus emphasizing the need for alternative theories. The rate of fluctuations was seen to be related to the difference between rate of gas generation and rate of gas escape from the system (U_g-U_e) as well as the bubble sizes. Thus, it seems like model development of dynamic foaming phenomenon has to take the effective chemical reaction rate as well as the bubble sizes into consideration</p>

Hydrate film growth has been examined at the hydrocarbon/water interface for cyclopentane and methane hydrate. Video microscopy was used to measure hydrate film thickness, propagation rate across the hydrocarbon/water interface and gas consumption measurements characterized the hydrate formation mechanism. Cyclopentane and methane hydrate film formation were measured over the temperature range of 260–279K and pressure range of atmospheric to 8.3MPa. Hydrate formation was initiated by the propagation of a thin, porous film across the hydrocarbon/water interface. The propagation rate and thickening of the hydrate film was strongly dependent on the hydrate former solubility in the aqueous phase, in the absence and presence of hydrate. Cyclopentane hydrate film thickness began at ~12 μm and grew to a final thickness (15–40 μm) which increased with subcooling. Methane hydrate film thickness began at ~ 5 μm and grew to a final thickness (20–100 μm) which also increased with subcooling. The hydrate film grew into the water phase. Gas consumption measurements indicated that the aqueous phase supplied hydrate former during the initial hydrate growth, and the free gas supplied the hydrate former for film thickening and development. Hydrate film formation at the hydrocarbon/water interface was proposed to consist of three consecutive stages: propagation, development and bulk conversion.

No description available.

No description available.

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No description available.