Reforming stack heat integrated

Competition, on similar lines, arises from Global Thermoelectric, Calgary, Canada (see web site), licensee of Forschungs Zentrum Julich (FZJ). Global Thermoelectric produces flat square cell SOFC stacks, in which the MEAs have 6 xm electrolyte. The stacks are integrated with a concentric module, which incorporates preheat of natural gas, water/steam and air, reform, exhaust combustion and heat utilisation, in the twin preheaters. These cells are widely used by other manufacturers for their stacks. 

Because a reformer consumes heat and water, and a fuel cell stack produces heat and water, integration of the stack and the reformer could be expected to improve system efficiency and simpUly system construction. This possibility... 

Ersoza et al. (2005) studied a 100 kW net electrical power PEM fuel cell system consisting of an autothermal reformer, high and low temperature shift reactors, a preferential oxidation reactor, a PEM fuel cell, a combustor and an expander. Intensive heat integration within the PEM fuel cell system was necessary to achieve acceptable net electrical efficiency levels. The fuel cell stack efficiency has been calculated as a function of the number of cells (500-1250 cells). The obtained net electrical efficiency levels are between 30% (500 cells) and 37% (1250 cells) and they are comparable with the conventional gasoline based internal combustion engine systems, in terms of the mechanical power efficiency. 

Like M( F(7s, S()F(7s can integrate fuel reforming within the fuel cell stack, A prereformer converts a substantial amount of the natural gas using waste heat from the fuel cell, (iornpoiinds containing sulfur (e,g, thiophene, which is cornrnonlv added to natural gas as an odorant) must be removed before the reformer. Typically, a hvdrodesiilfii-rizer combined with a zinc oxide absorber is used. 

Figure 105. Modern integrated single-train ammonia plant based on steam reforming of natural gas (Clide process) a) Sulfur removal b) Primary reformer c) Steam superheater d) Secondary reformer e) Waste heat boiler f) Convection section g) Forced draft fan h) Induced draft fan i) Stack k) TIT and LT shift converters ...

In general, a reformer is designed to minimize gas-phase reactions, avoid heat loss, and reduce thermal mass to facilitate rapid startup. The integration of an external reformer and a stack requires definition of appropriate procedures and conditions to achieve stable and efficient operation of the system (to avoid carbon deposition and to ensure the ability of the system to accommodate transients in... 

SOFC systems can be designed to include a heat recovery component such as an adsorption chiller heater for CHP applications [72-76]. An example is a small (1-lOkW) methane-fueled residential CHP SOFC system that integrates CGR, AGR, and internal reforming [73]. The system consists of a fuel-cell stack, steam prereformer, various fluid delivery devices (blowers, ejectors, compressor, and water pump), heat exchangers, and catalytic combustor and power conditioning device along with a heat recovery component. Based on certain system parameters (50active area, nominal cell temperature of 800 °G, current density of 0.57 A cm , power density of0.40-0.43 Wcm , S/G ratio of 2.0, SOFC... 

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