Strategies For Multiphase Reactor Selection – Essay Example

Weaknesses and strengths: Strengths: The experiment employs standard strategies for choosing the reactor configurations. Krishna and Sie (1994) have suggested three levels of strategies for the reactor configuration that focus on the catalyst design, reactant and energy dispersion strategy and the choice of hydrodynamic flow regime. Also, the experiment chooses to use a packed-bed reactor configuration over trickle-bed reactor design although the experimenters use two different designs of the packed-bed: single-channel and multiple channel reactor for comparison.
Weaknesses:
There is no clear choice of dispersion strategies employed in the experiment, either the single or multiple channel reactor configuration. Flow pattern chosen is cocurrent with no discussion of the disadvantages of the other two: counter-current and cross-current contacting of phases or the reasons for choosing cocurrent contacting of phases. The paper lacks explanation of the loss due to undesirable side reactions due to hydrogenation and the effects of energy dissipation. The efficiency range of 5-15 -1s for overall mass transfer coefficients can result in varying levels of energy dissipation which needs to be discussed minutely for higher efficiencies as mass transfer effects help gauge the efficiency (Losey et al, 1999). Pressure drop is difficult to predict in multi-phase flows as the relative liquid and gas volumes cannot be known.
Suggestions:
The reactor operated in steady cocurrent flow but performance can be improved with pulsed flow, although it complicates the interpretation of mass transfer and kinetic data.
The paper needs to discuss steps taken to control the drying out of the catalyst when gas flow rate increases resulting in oscillation at the gas-liquid interface at the distributor.
Choose smaller particle size for catalyst for higher performance.
Paper also needs to discuss how efficiency can be increased with cyclohexane catalyst as compared to traditional multi-phased packed bed reactors as the present experiment achieves the same efficiency as the earlier ones. This can help improve the mass transfer rates further with the added benefit of achieving pulsed flow.
Minimum cost of overall experimental setup to be discussed along with ease of scaling up.
Ensure a suitable mechanism for maintaining a constant cocurrent at the interface of the distributor to avoid catalyst dry out to increase efficiency.
Use CFD (Computational Fluid Dynamics) modelling to evaluate performance against another multi-phase model.
To describe in detail the relationship between process, feedback and catalyst parameters
Explicitly describe the reactor design configuration based on the three design strategies.
References:
Krishna, R and Sie, T.S. 1994. STRATEGIES FOR MULTIPHASE REACTOR SELECTION. Chemical Engineering Science. Vol. 49, No. 24A. Elsevier Science Ltd.
Losey, W.M, Schmidt, A.M and Jensen, K.M. 1999. A Micro Packed-Bed Reactor for Chemical Synthesis. 3rd International Conference on Microreaction Technology. Heidelberg.