Sodium hydrogen generation system

Figure 9.58 1-kWei sodium borohydride hydrogen generation system [101],... 

Zhang, J., Zheng, Y, Gore, J.P. and Fisher, T.S. (2007) IkWe sodium borohydride hydrogen generation system. Part I Experimental study. J. Power Sources, 165, 844-853. 

The solvated electron was observed to be an intermediate in the reaction of sodium with solid alcohols at 77° K by optical and ESR techniques [114]. It is now known to be generated in the sodium—liquid alcohol system [115]. The formation of the solvated electron was demonstrated by using dinitrogen monoxide as the electron scavenger, when nitrogen was formed. The hydrogen is evolved via an intermediate (eroiv)2 as might be the case in water. 

Aubry, J. M. and S. Bouttemy, S. 1997. Preparative oxidation of organic compounds in microemulsions with singlet oxygen generated chemically by the sodium molybdate/ hydrogen peroxide system. J Am Chem Soc, 119, 5286-5294. 

The wastewater from a hydrogen plant typically consists of only the blowdovm from the boiler system. The boiler feedwater that feeds the steam generation system has small amounts of impurities such as sodium, chlorides, silica, and organic carbons. These impurities will accumulate within the boiler system and create sludge, scaling of the boiler tubes, and possible carryover of solids into the process steam. Blowdown of the boiler water is performed to prevent these issues from affecting the operation of the steam system. The blowdown is typically sent to the sewer or the on-site waste treatment plant for treatment and disposal. 

On-site generation is necessary because the compressed liquid is explosive at room temperature. It is an unstable gas and therefore is not stored or shipped in bulk. Chlorine dioxide is most commonly produced by reacting chlorine gas with sodium chlorite. These generation systems are described in chapter 3, and they use various combinations of sodium chlorite, sodium chlorate, hydrogen peroxide, sulfuric acid, hydrochloric acid, and sodium hypochlorite solution. 

Anhydrous sodiummetaboratereactsexothermically with water, rehydrating toNa[B(OH)4]xH20, where x is 0 or 2, depending on temperature. Since sodium borohydride-water systems for practical hydrogen generation do not involve conditions where anhydrous sodium metaborate can form, the hydrogen release reaction is more accurately represented by Equation 16.1. 

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