High-flow cascade impaction

Other chemical companies have also designed their own continuous process to produce high-impact polystyrene (HIPS), such as the Dow process, which consists of three elongated reactors in series (US Patent 2727 884, 1955) the BASF process, which consists of a prepolymerization CSTR followed by cascade of three CSTRs (US Patent 3 658 946, 1972) the Shell process, which consists of three CSTRs followed by a plug flow reactor (US Patent 4011 284, 1977) and the Monsanto process, which consists of a CSTR followed by a horizontal plug flow reactor (US Patent 3 903 202, 1975). 

Care has to be taken in joining source term and dispersion calculations in this way. High vapour velocities 0(5 m/s) are typically induced by the cascade at the foot of the tank. Even though the flow is denser than air, such a flow will entrain air as it flows out across the floor of the bund. This entrainment process occurs whether the flow impacts on a bund wall (as in Figure 17) or not. Any entrainment of fresh air after the bulk of the liquid has rained out will result in a reduction in vapour concentration. Contact between the vapour and liquid pool on the floor of the bund may on the other hand increase the concentrations, although this may be limited since the vapour close to the floor of the bund may be close to being saturated already. 

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