Hydrogen plant efficiency

The hydrogen plant efficiency is defined as the total energy produced by the hydrogen plant divided by the total energy consumed by the plant, determined by the following formula [11] ... 

Use of a low temperature shift converter in a PSA hydrogen plant is not needed it does, however, reduce the feed and fuel requirements for the same amount of hydrogen production. For large plants, the inclusion of a low temperature shift converter should be considered, as it increases the thermal efficiency by approximately 1% and reduces the unit cost of hydrogen production by approximately 0.70/1000 (20/1000 ft ) (140,141). 

The thermochemical cycles (S-I > 850°C) or hybrid cycles (S-electrolysis > 850°C) still feature many uncertainties in terms of feasibility and performances. Uncertainties still exist in parts of the flow sheet and technologies needed to provide high temperature heat whether from solar or nuclear nature. Potential assets of thermochemical cycles lie in a theoretical potential for a global efficiency above 35% and a scaling law of the hydrogen plant after the volume of reactants instead of the total surface of electrolytic cells. In return, their practical feasibility and economic viability have to be entirely demonstrated. Especially, a global efficiency above 30% is to be demonstrated to compete with alkaline electrolysis. Moreover, the safety of co-located nuclear and chemical plants has to be demonstrated. 

The coupled nuclear-hydrogen plant investigated in this paper was studied in earlier work (Vilim, 2007). There the full power condition and the combined plant efficiency were estimated. The plant appears in Figures 1 through 3 as three modules - the primary system, the power conversion system and the high-temperature electrolysis plant. The interface between the nuclear side and the chemical plant appears in these figures in the form of the flow paths that connect these three modules. 

Fleshman, J.D., Cost Efficient Revamps in Hydrogen Plants , Proceedings of NPRA Annual Meeting, New Orleans, USA, March 2001. 

This study case is designed as a free-standing hydrogen plant. Economies of operation could undoubtedly be obtained if this plant can be integrated with the utility system of an existing complex e.g. the 150,000 lb/hr of steam produced from the auxiliary boiler could be more efficiently included in the capacity of a larger boiler. 

Application The Linde ammonia concept (LAC) produces ammonia from light hydrocarbons. The process is a simplified route to ammonia, consisting of a modern hydrogen plant, standard nitrogen unit and a high-efficiency ammonia synthesis loop. 

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