16.1.3 Technical questions

1. Provide an insight into the liquid phase guided gas phase reaction ?
Ans: The liquid phase acts as a resistance phase for the movement of various gases.  The recirculator enables greater turbulence of the liquid phase stream.  Thereby, using these mechanisms, the gases are allowed to react with one another and produce ethylene dichloride which gets dissolved in the liquid.

2. Why a water condenser followed by refrigeration is used when the single refrigeration can serve the purpose of cooling ?
Ans: This is an important question.  Allowing only refrigeration enhances process costs drastically. Therefore, water is used to carry out partial condensation and then refrigeration, even though in principle, water condensation can be bypassed and reactor operation and stream contacting can be further optimized.

3. Why do we need a settling tank after the acid wash unit associated to the crude ethylene dichloride ?
Ans: Typically, we observe HCL removal from vapour streams.  In such case, the unit used is a scrubber or absorber.  The gas/vapour is fed to the absorption column and is obtained as a gas. When a liquid is allowed for scrubbing, it is possible to obtain emulsions of the organic phase in the aqueous phase. Therefore, provide gravity settling mechanism should exist so as to separate the crude ethylene dichloride from the mixture emanating from the acid wash tank.