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Design of outlet system for a methanol reactor

Design of outlet system for a methanol reactor

Background

Topsoe designs catalytic reactors used for the production of methanol from synthesis gas. The synthesis gas contains mainly hydrogen, carbon monoxide and carbon dioxide and will be produced from e.g. natural gas, oil or coal.

The reactor is a vertical tubular reactor. The catalyst is contained inside the tubes (typically 2000 to 4000 tubes, 7 m long) and on the outside of the tubes; boiling water is used to remove the heat from the exothermic reaction-taking place inside the tubes.

The catalyst in the tubes is loaded tube by tube through the top of the reactor. The bottom of the reactor is filled with ceramic balls acting as support for the catalyst inside the tubes. The catalyst must be replaced on a regular basis, say every 5 years, and with the present design unloading is carried out through a number of openings at the bottom of the reactor, whereby the ceramic balls and the catalyst will be dumped into a container placed below the reactor.
 

The challenge

The ceramic balls are rather costly and as they can be reused, they are separated from the catalyst in a screening process after being dumped. Then the ceramic balls are reloaded through an opening at the bottom of the reactor before loading of fresh catalyst.

As the operation during catalyst replacement is rather tiresome, the project goal was to construct a new design for support of the catalyst omitting the ceramic balls.
 

The solution

In this case, the catalyst support is provided by a grid arrangement located just below the catalyst tubes. The grid is divided into a number of sections and hinged in a manner that allows the grid sections to be released from the normal position and subsequently opening up for the catalyst to drop out of the reactor. The grid release can be carried out from the outside of the reactor. After the reactor has been unloaded, the grids can be swung back in their normal position and fresh catalyst can be loaded.
 

The project work

  • Function analysis of the existing solution
  • Function analysis of a number of alternative solutions
  • Detailed design of one solution comprising material selection, stress calculations, welding specifications, detailed drawings and cost estimate
     

Students

Dennis Daugård Hansen and Lars Lundberg Kristensen, Ingeniørhøjskolen i København (IHK), Machinery Engineering Department
Bachelor thesis in the Technology Division, Mechanical Engineering Department