It is a well known fact that a hotspot formation is inevitable in a fixed-bed tubular catalytic reactor when the reaction is exothermic, and heat generation is excessive ; and this is a serious threat to the safety of the commercial operation of such reactors.
Various suggested methods to avoid the reactor hotspot are categorically discussed, and intensive investigation is made toward the heat carrier gas injection method to moderate the hotspot. Large scale experimental verification is conducted at temperatures higher than 420 ℃.
The system under consideration is the patented p-xylene gas phase ammoxidation reaction to produce terephthalonitrile. The experimental unit consists of 12 ft, 1^〃OD salt-jacketted reactor, very similar to the commercial scale unit and does not require extra scale-up study. The inert heat carrier gases studied were CH₄, CO₂, & C₂H₄, and percent dilution was determined, to demonstrate the commercial feasibility of the hotspot moderation technique.