(429d) Tubular Multi-Tube Cooled Reactor As a Fractional Heat Exchanger – Modeling Reactive Heat Transfer

Many industrially important vapor phase reactions are equilibrium controlled and highly exothermal in nature which leads to high reactor exit temperature. Very often product gas requires cooling in a tubular heat exchanger before it is sent to the next unit operation. Residual reaction could occur under reduced temperature within the heat exchanger and end product profiles and final gas conditions are determined by the relative rates of heat transfer and reaction in such a unit. If the gas final cooled product compositions and conditions are important to the next unit operation, proper prediction, monitoring and control of the unit through rigorous process modeling is critical.

If the inlet gas to heat exchanger temperature is extremely high, then heat transfer by radiation should be considered since the effect of this heat transfer mode cannot be neglected when inlet gas temperature is very high. Exchanger outlet gas temperature can be controlled by properly design the residence time of gas inside the exchanger. Any reactions after the cooling require certain gas compositions and temperature which should be properly handled together with the gas cooler. Optimization of the combined unit operations will result in potentially reduced capital investment and operational costs, along with obtaining more desired final product compositions and conditions.

If the purpose of the cooling is purification of the gas stream, reactions occurring in either vapor or condensed liquid phase should be evaluated carefully to identify the extent of reaction and its impact on the separation performance. When a phase change exists, both phase and chemical equilibrium should be considered and mass transfer across the interface should be included along with heat transfer. Optionally chemical reaction kinetics and fluid flow of the condensed liquid should be considered.

This talk will present rigorous modeling of reactive heat transfer which may be useful to process intensifications.