Carbon monoxide integral heats

This system includes several mixing and heat exchange units. A concept for an integrated, microtechnology-based fuel processor was proposed by PNNF [8]. As examples for unit operations which may be included in future integrated systems the same publication mentions reactors for steam reforming and/or partial oxidation, water-gas shift reactors and preferential oxidation reactors for carbon monoxide conversions, heat exchangers, membranes or other separation components. 

Preferential Carbon Monoxide Oxidation 3 [PrOx 3] Integrated Micro Structure Heat Exchanger for PrOx Applied in a 20 kW Fuel Processor... 

Preferential Carbon Monoxide Oxidation 5 [PrOx 5] Integrated Heat Exchanger/Reactor for PrOx... 

Figure 2.60 Integrated reactor/heat exchanger for the preferential oxidation of carbon monoxide developed by Eindhoven University and IMM [89] (source IMM).

For reformate flow rates up to 400 Ndm3 min-1, the CO output was determined as < 12 ppm for simulated methanol. The reactors were operated at full load (20 kW equivalent power output) for -100 h without deactivation. In connection with the 20 kW methanol reformer, the CO output of the two final reactors was < 10 ppm for more than 2 h at a feed concentration of 1.6% carbon monoxide. Because the reformer was realized as a combination of steam reformer and catalytic burner in the plate and fin design as well, this may be regarded as an impressive demonstration of the capabilities of the integrated heat exchanger design for fuel processors in the kilowatt range. 

One of the high priorities for hydrogen production for use in fuel cells is the purity of gas. In a conventional process this can be difficult to achieve at a high level, due to relatively low conversion of CH4, as well as the presence of carbon monoxide and carbon dioxide. The integrated heat exchanger reactor overcomes this with the use of membranes. These allow the purity of the gas to reach 100% (Buxbaum, 1997). 

Giroux et al. performed a comparison of an adiabatic water-gas shift reactor, which had a temperature rise from 300 to 360 °C, isothermal operation at 350 °C achieved by integrated heat-exchange and a reactor with a declining temperature profile from 550 to 300 °C [57]. In each case the same degree of carbon monoxide conversion was achieved in the reactors, but the space velocity increased from 35 000 h for the adiabatic reactor to 50 000 h for the isothermal reactor and even up to 70 000 h for the reactor with the declining temperature profile, which means that the last reactor would require only half the size of the adiabatic counterpart. 

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