Study of axial mixing, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column using radiotracer technique.
Axial mixing, holdup and slip velocity of dispersed phase which are parameters of fundamental importance in the design and operation of liquid-liquid extraction pulsed sieve plate columns have been investigated. Experiments for residence time distribution (RTD) analysis have been carried out for a range of pulsation frequency and amplitude in a liquid-liquid extraction pulsed sieve plate column with water as dispersed and kerosene as continuous phase using radiotracer technique. The column was operated in emulsion region and (99m)Tc in the form of sodium pertechnetate eluted from a (99)Mo/(99m)Tc generator was used to trace the dispersed phase. Axial dispersed plug flow model with open-open boundary condition and two points measurement method was used to simulate the hydrodynamics of dispersed phase. It has been observed that the axial mixing and holdup of dispersed phase increases with increase in pulsation frequency and amplitude until a maximum value is achieved while slip velocity decreases with increase in pulsation frequency and amplitude until it approaches a minimum value. Short lived and low energy radiotracer (99m)Tc in the form of sodium pertechnetate was found to be a good water tracer to study the hydrodynamics of a liquid-liquid extraction pulsed sieve plate column operating with two immiscible liquids, water and kerosene. Axial dispersed plug flow model with open-open boundary condition was found to be a suitable model to describe the hydrodynamics of dispersed phase in the pulsed sieve plate extraction column.
OPTIMIZED VALUES FOR A SIEVE PLATE PULSED COLUMN FOR ACETIC ACID, WATER AND KEROSENE SYSTEM
An experimental study was conducted using sieve plate pulsed column. Correlations were developed among different variables with the help of data obtained from operation of the pulsed column in polynomial form. These correlations could be utilized to get an optimum value for acetic acid, water, kerosene system. Flow rate of solvent, concentration of aqueous solution of acetic acid and pulsation frequency were taken as independent parameters; whereas concentration of acid in extract phase (CE2) and in raffinate phase (CR1), percentage equilibrium and height of transfer units (HTU) were treated as dependent parameters. A significant effect of pulsation frequency and flow rates of both the streams have been observed on the concentration of extract, raffinate, percentage equilibrium and height of transfer units. Pulsation frequency of 56 (cycles/min) was found critical beyond which a gradual change in all the profiles were observed.
Silica in Soils1
Publisher Summary Silica in free and combined forms is a dominant component of the solid material of many soils, and dissolved silica is commonly a major solute of soil solutions. Breakdown of primary silicates, translocation of silica in solution, and deposition of secondary silica-containing substances are involved in the development of soils. Ions essential for the growth of plants are released to the soil solution as silicates weather, and these ions may be held against leaching at exchange sites on other silicates. Silica is absorbed in appreciable quantities by some plants and is returned to the surface of the soil as the plants decay. The nature and transformations of silica and silicates in soil are, thus, fundamental to an understanding of many aspects of soil and plant sciences.