Figure 5. Methanol and oxygen mole fraction contour plots in the thermally coupled reactor for conducting simultaneous endothermic and exothermic reactions.
The chemical enthalpy and sensible enthalpy contour plots are illustrated in Figure 6 in the thermally coupled reactor for conducting simultaneous endothermic and exothermic reactions. A thin layer of a slurry containing the ceramic precursor is applied on the surface by means of spraying, painting, or dipping. After applying for the coat, the slurry is dried and calcined at a temperature usually in the region of 350-1000 °C. Finally, the ceramic layer is impregnated with the catalytic active material. Alternatively, the catalytic active material is applied for simultaneously with the ceramic precursor. Unfortunately, a number of disadvantages of the catalyzed hardware reactors compared to fixed bed reactors exists. The catalyst layer cannot be replaced if it loses its activity either by ageing or by poisoning. The catalytic layer can only be applied to certain materials. The reactor tubes have to be made of this type of material which may be more expensive than a conventional tube material. The steam reforming reactions occurs under pressurized conditions and the tube thickness is large, hence the cost of materials influences the price significantly. Furthermore, production of long catalyzed hardware reactor tubes can be difficult. The reactor tube can have a length of 50 mm or more. It will be difficult to obtain an even thickness of the reforming catalyst layer throughout such a length, and means to obtain an even layer, which can be used for small scale application such as centrifuging the tube, is more difficult to apply for this size of tubes. Additionally, appropriate heat treatment of a tube of this size can be difficult. These drawbacks can be overcome by producing the catalyzed hardware separately from the reactor. A metal support is cut into an appropriate size. The sheet is wash-coated. After the wash-coating, the sheet is formed into the appropriate shape. Alternatively, the sheet is formed into the final shape prior to the wash-coating. The metallic support is formed substantially to have the same shape as the reactor wall and is arranged in a direct heat conduction relationship with the reactor wall. It will be possible to change the catalytic layer if it no longer has sufficient catalytic activity. The expensive steel used to obtain adhesion of the catalyst to the metal surface will only comprise a small fraction of the total metal consumption. The catalyzed hardware can be produced in smaller sections, which will be easier to manufacture and handle. Pressure drop in the catalyzed reformer tube is much lower than in the conventional case for the same tube diameter. This enables the use of reactor tubes with a smaller diameter and still maintaining an acceptable pressure drop. Smaller tube diameter results in an increased tube lifetime, tolerates higher temperatures and reduces the tube material consumption.