Date of Award
Master of Engineering (ME)
D. R. Woods
A 2 inch diameter, conical-shaped glass hydrocyclone, operating without an air core, was used in this study. The geometric dimensions of the cyclone followed closely with the optimum design conditions determined for solid/liquid systems by Rietema (R-1) and used by Burrill and Woods (B-3) for liquid/liquid systems. Distilled water was used as the continuous phase. Dispersed oil phases studied include: butanol, methyl isobutyl ketone (MIBK) , toluene and kerosene.
For each of the liquid/liquid systems, the efficiency of separation was determined as a function of volume split, oil/water phase ratio and feed flowrate. Differentiation of the liquid/liquid systems, in terms of physical properties, was based primarily on interfacial tension. Density difference and viscosity of the dispersed phase, were comparable from one system to another. Mixing energy used to disperse the oil phase in the water phase, geometric dimensions and temperature were constant throughout the work. The range of the operating variables were as follows:
i) oil/water phase ratio 0.160 to 1.00
ii) feed flowrate 100 to 365 mL/s
iii) interfacial tension 2.0 to 30.0 mN/m
iv) volume split 0.17 to 3.90
For each system studied, photographs were taken at the inlet and outlets leading to and from the cyclone, respectively, to determine the drop size of the dispersed phase.
The second part of the present work considered the influence that the mixing energy had on the effects of oil/water ratio and feed flowrate as studied in the first part.
The efficiency of separation (Es ) is defined as follows:
where Y and Q represent volume fraction of light phase and flowrate, respectively, while the subscripts denote specific orifice location on the hydrocyclone.
From the first part the efficiency of separation in the cyclone was a very important function of volume split. The effect of the feed flowrate on separation in the cyclone was dependent on the interfacial tension. The effect of oil/water ratio was dependent on the rate of coalescence. Based on the photographic work, coalescence occurred in the cyclone for several of the systems studied.
The majority of past work has varied the mixing energy with a change in the feed flowrate. As a result, drop size varied. Present work revealed that this reversed the effect that feed flowrate had on the separation in the cyclone with mixing energy constant.
It was not possible to obtain two pure phases from the hydrocyclone for any of the systems studied. One pure phase, however, was achieved for three of the four systems studied. A relatively pure water phase (≥ 99%) was obtained at the underflow for the MIBK/water, toluene/water and kerosene/ water systems. The highest values of the optimum Es were 67, 57 and 62%, respectively, for each of these systems. For toluene/water and kerosene/water systems, the interfacial tension was sufficiently high to prevent significant drop breakup when the feed flowrate was increased. Under similar circumstances, drop breakup predominated for MIBK/water and butanol/water systems due to the lower values of interfacial tension. With butanol/water, a significant amount of light phase was found in the underflow. The optimum Es for this system was only 26%.
It was noted that the efficiency of separation, Es, increased sharply at first and then decreased gradually with increasing volume split. The optimum volume split occurred at a value greater than the feed phase ratio for all systems studied. The optimum volume split occurred at a value ranged from 100 to 500% greater than the feed phase ratio. Since complete coalescence does not occur inside the cyclone, it is not possible to have the optimum split equivalent to the feed phase ratio. Continuous phase trapped in the interstides results in the optimum split equivalent to a value greater than the feed phase ratio. A simple mass balance model was used to describe the effects of volume split. From this model the interstitial volume could be inferred for all conditions. Combining this information with models for breakup, coalescence and hindered setting yielded a semi-quantitative explanation of all the trends observed.
The feasibility of using the hydrocyclone to separate emulsions is based on achieving at least one pure phase. If this achievement is accomplished, then it is possible to reduce the volume requirement of a gravity settler. The role of the hydrocyclone is basically one of a preliminary stage in the physical separation process. If, on the other hand, it is not possible to have one pure phase, no useful purpose is served by the cyclone. Consequently, the butanol/water system can not be considered a feasible system to be separated by a hydrocyclone.
Scott, Walter Malcolm, "THE EFFECT OF CERTAIN PARAMETERS ON THE SEPARATION OF VARIOUS LIQUID/LIQUID SYSTEMS BY A HYDROCYCLONE" (1980). Open Access Dissertations and Theses. Paper 3639.