Figure 3. Effect of temperature on the methanol mole fraction along the fluid centerline of the process microchannel of the microchannel methanol steam reformer reactor.
The effect of temperature on the methanol mole fraction on the catalyst surface is illustrated in Figure 4 along the length of the process microchannel of the microchannel methanol steam reformer reactor. Steam reforming reactions are typically performed at temperatures in the range of 200 °C and 300 °C, and at pressures in the range of 50 psi and 800 psi. Therefore, a steam reformer typically includes, or is in thermal communication with, a heating assembly. The heating assembly may be located within the steam reformer, external the steam reformer, or both. The heating assembly may utilize any suitable heating mechanism or device to heat the steam reformer to a selected operating temperature. For example, the heating assembly may include a resistance heater, a burner or other oxidation unit that produces a heated exhaust stream, and heat exchange with a heated fluid stream. The heating assembly includes a fuel stream, which will tend to vary in composition and type depending upon the mechanisms used to produce heat. For example, when the heating assembly is a burner or otherwise creates heat by oxidation, the stream will include a stream of a combustible fuel, such as an alcohol or hydrocarbon, and a combustible gas, such as hydrogen gas. When the heating assembly includes an electric resistance heater, then the stream will include an electrical connection to an electrical power source. In some cases, the feed stream may be delivered to the steam reformer at an elevated temperature, and accordingly may provide at least a portion of the required heat. When a burner or other oxidation chamber is used, a fuel stream is consumed and a heated exhaust stream is produced. The feed stream is vaporized prior to undergoing the reforming reaction, and the heating assembly may be adapted to heat and vaporize any liquid components of the feed stream.