Multi-tubular Fixed Bed Reactor Research Articles

The fischer-tropsch process - commercial aspects

This review is an update of previous reviews dealing with the Sasol process, the catalysts used, the control of selectivity, the kinetics and the mechanism of the F-T reaction. The emphasis is on the practical aspects. With regard to reactor developments two new types have now been put into commercial production, namely a 45 bar multi-tubular fixed bed reactor for wax production and an alternative type of fluidised bed reactor for light oil production. The latter reactor costs much less to construct and to operate than the older circulating fluidised bed reactors. The slurry phase reactor concept is now entering the demonstration size stage of development. Improved olefin oligomerisation catalysts have resulted in a better quality diesel fuel being made in downstream upgrading. The best way of producing maximum and high quality diesel is to maximise wax production and then to selectivity hydrocrack it. A comparison is made between the two existing Sasol processes and the proposed Shell Middle Distillate process.

Dynamic Behaviour of Fixed Bed Catalytic Reactors

Characterizing dynamic behaviour depends on identifying all the significant factors which must be included in models which are used to describe the system. As operation at higher performance is demanded the level of approximation assumes greater importance. At the same time there is a need to examine the way in which reduced models can be developed for use in control. This paper examines these issues with reference to the multitubular fixed bed reactor and in particular looks at how the coolant temperature profiles influence the dynamics. It specifically examines how the temperature profiles affect the inverse response both in terms of the extent and location in the reactor and the way in which disturbances are propagated. Consideration is also given to the effect of changes in reactant flow rate and the way in which it affects the inverse response.

Operation of coaxially cooled fixed-bed catalytic reactors: conditions of existence of the pseudoadiabatic regime

The Pseudoadiabatic Operation (PO) of multitubular fixed-bed catalytic reactors allows to control the hot-spots for highly exothermic reaction systems, locating them at the outlet of the unit. This regime can be applied succesfully to the methanol-to-gasoline conversion process (MTG). A theoretical demonstration is presented, for first-order or pseudo-first-order reactions, proving that the fully countercurrent mode does not admit PO regimes. The study is completed with the development of an “ a priori” criterion for the prediction of operating conditions admitting the PO when the inlet coolant temperature is different from that of the reactant stream.