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.
Radiotracer investigations in aniline production reactors.
Radiotracer investigations were carried out to measure the residence time distribution (RTD) of the heat transfer medium (HTM) in two identical aniline production reactors. One was operating abnormally while the other functioned normally. Investigations were carried out to identify the cause(s) of inadequate heat transfer from the tube-side to the shell-side of the abnormally operating reactor. For measuring the RTD of the HTM in the shell-side of the reactor. 82Br as paradibromobenzene was used as a tracer. The analysis of the measured RTD data revealed that about 60% of the shell-side volume of the abnormally operating reactor was fouled/dead, this being the root cause of the inadequate heat transfer. The modelling of RTD data indicated undesired parallel flow streams in the shell-side of the abnormal reactor. Shutdown of the abnormally operating reactor was instituted to allow remediation, fouling subsequently being visibly confirmed. The planned shutdown resulted in reduction in downtime, with substantial economic benefit to the industry.
Optical rotatory dispersion and absolute configuration—III
Abstract Optical rotatory dispersion measurements on pyrrolidine, piperidine, and tetrahydro-isoquinoline alkaloids indicate that the absolute configuration of the α-asymmetric center may be assigned directly from the dispersion curve, provided either that the nitrogen atom is not protonated, or that the compound contains a chromophore absorbing above 200 mμ.