Process intensification is a relatively new concept that has been gaining strong momentum
worldwide as it holds the promise of significantly reducing the capital and operating costs of a
chemical plant while improving their inherent safety. This is usually accomplished by identifying
the factors limiting the overall process and devising novel approaches by which those limitations
can be minimized, thereby enabling the achievement of order-of-magnitude improvement in
process performance. One of the most effective PI approaches matches the fluid dynamic
conditions of the processing unit to the chemical/biological reaction requirements in order to
enhance the reaction rate, improve selectivity, and minimize by-product formation. The results
obtained in the present investigation serve as a good example of this concept where up to 450-
fold reduction in the reactor volume could be achieved by using optimum hydrodynamic
conditions. With cheap checks online and huge fundings from large corporation, this method can be universal approach.
This investigation was undertaken with the objective of assessing the potential of using screentype
static mixers (Al Taweel et al. 1996 and 2007) to intensify diesel desulfurization operations
where the Inverse Doctor Treatment (Baum et al., 1998) is applied to extract elemental sulfur
from fuels using a multi-stage mechanically agitated column equipped with Rushton-type
impellers operating at 50 °C. Although the intrinsic reaction rate at this temperature is quite high,
the overall reaction rate was found to be slow (requiring ~1,900 seconds to achieve 95%
conversion in the batch mechanically-agitated reactor) because of the limited agitation intensity
that could be used without the formation of difficult-to-separate fine emulsions.
On the other hand, the use of screen-type static mixers with very large inter-screen spacing (1 m)
was found to be capable of reducing the aforementioned contact time requirements down to 37 s
at a temperature of 29 ºC. This could be further reduced to 4.1 s by using very small inter-screen
spacing (25.4 mm) even at a temperature of 20 ºC. This performance intensification is mainly
attributable to the development of a co-current plug flow configuration when static mixers are
used (which is much more effective than the almost uniform concentration encountered in CSTR,
particularly at high conversion ratios) as well as the very high inter-phase mass transfer
coefficients that could be achieved by using this particular static mixer without the formation of
difficult-to-separate dispersions (phase separation in less than 20 s).
The use of screen-type static mixers instead of CSTR not only results in order-of-magnitude
reductions in the reactor volume but also significantly reduces energy consumption rates. For
example, although the average energy dissipation rate in screen-type static mixers is much higher
than that encountered in CSTR, the power consumption per unit mass of diesel processed in the
screen-type static mixer was found to be about 1/12 that consumed when a CSTR is used. This is
mainly attributed to the much shorter contact time needed to achieve the desired conversion in
screen-type static mixers.
These findings suggest that a unit composed of 5 parallel tubes (0.1 m ID and 1.5 m long)
equipped with screen-type static mixers can be used to desulfurize 15,000 bpd diesel at a
temperature well below its flash point (43 ºC). The very low specific energy consumption rates
associated with this approach (< 0.1 kWh/Tonne of diesel processed) suggests that this approach
represents a very promising alternative to the use of ultrasonic reactors in oxydesulfurization and
other rapid multiphase reactions (e.g. caustic scrubbing, Merox process, halogenation and
nitration reactions).

Quantifying the flow and residence time distribution (RTD) in a reactor is critical for predicting reactor performance measures such as yield and selectivity. This work investigated a continuous industrial scale reactor (diameter 11 ft, height 37 ft) employing a 3-stage agitation system with a plunging jet inflow. In operation, the agitation and liquid level are adjusted based on throughput and the specific product being produced. The objective of this work was to quantify RTD under the different operating conditions of liquid level, throughput and agitation. Flow in the reactor was modeled with computational fluid dynamics (CFD). A combination of different modeling approaches was used to better facilitate the CFD simulations. The Volume of Fluid (VOF) method was used to model the plunging jet (gas-liquid) two-phase flow with unsteady-state simulations, while the Multiple Reference Frames (MRF) model was used to model the stirred tank with steady-state simulations. The two modeling approaches were interfaced by using the plunging jet simulation result as the input boundary condition for the reactor flow simulation. The effect of gas entrainment from the plunging jet impingement was accounted for by using the (dampened) velocity profile of the impinging jet. The RTD was obtained from stochastic particle tracking which tracks trajectories and residence times of massless tracers in the reactor. The Random Walk Model was used for dispersion of tracers due to turbulent eddies. A large number of tracers (>10,000) was needed to account for the random effects of turbulence and ensure statistically stable results. The Time Scale Constant in the Radom Walk Model was adjusted to accommodate significant turbulence level differences in discreet regions of the tank. The CFD-predicted flow pattern compared well with lab-scale experiments. The predicted mean RTD was consistent with the bulk reactor turn-over time