Liquid hydrogen production capacity

Commercial success of sulfur-iodine hydrogen production depends largely on the capacity to identify materials of construction that can handle the corrosive environments and on the ability to manufacture process components with these materials economically. This chapter has reviewed a cross-section of materials data generated by testing in the various process settings within the cycle. Ta alloys and SiC have been shown to have good corrosion characteristics in all the liquid environments, but individual candidates have also been suggested for use in particular conditions. Both of these materials have unique mechanical properties, and much effort is needed in order to use them for component fabrication. 

Ignoring the cryogenic liquid market (e.g., rocket fuel) that accounts for 7% of the merchant market, in 2003 the total U.S. merchant hydrogen gas capacity was about 1 500 M Standard Cubic Feet (SCF)/day. Most of this merchant production capacity (92%) was located in three slates Texas with 560 M SCF/day, Louisiana with 440 M SCF/day, and California with 380 M SCF/day [5,6]. Also, the Chemical Market Reporter [5] writes, Another 3 billion SCF per day of captive hydrogen capacity exists at 145 locations in the US. Therefore, in 2003 the U.S. had a total capacity of about 4 500 M SCF/cUy, or about 127 M mVday. 

Due to its high vapor pressure at the operating temperature of the electrolysis, mercury, whose circulating tonnage represents 700 to 2400 kg/t per day of chlorine production capacity, pollutes the different gaseous streams produced (chlorine, hydrogen). Similarly, it contaminates the different liquids produced by the operation (spent brine, caustic soda, etc.). This results in substantial losses, which must be limited for economic as well as environmental reasons. Whereas small. amounts of mercury in the chlorine (0.1 to 0.2 g/t) are not detrimental to its subsequent uses, the same cannot be said of caustic soda, especially for food applications, in which it is removed by filtration (up to 15 ppb), for hydrogen, from which it is removed (up to 3 to 5 ppb) by absorption in sodium hypochlorite, adsorption on activated charcoal etc, and aqueous wastes, from which it is removed (up to 5 to 10 ppb) by precipitation, adsorption, reduction or extraction. The spent brine, which normally contains 1 to 10 ppm mercury and occasionally 1000 ppm, is usually recycled and therefore does not require treatment... 

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