On-site production

Uses. The dominant use of sulfur dioxide is as a captive intermediate for production of sulfuric acid. There is also substantial captive production in the pulp and paper industry for sulfite pulping, and it is used as an intermediate for on-site production of bleaches, eg, chlorine dioxide or sodium hydrosulfite (see Bleaching agents). There is a substantial merchant market for sulfur dioxide in the paper and pulp industry. Sulfur dioxide is used for the production of chlorine dioxide at the paper (qv) mill site by reduction of sodium chlorate in sulfuric acid solution and also for production of sodium dithionite by the reaction of sodium borohydride with sulfur dioxide (315). This last appHcation was growing rapidly in North America as of the late 1990s. 

Sodium dithionite solution can be produced on-site utilizing a mixed sodium borohydride—sodium hydroxide solution to reduce sodium bisulfite. This process has developed, in part, because of the availabiHty of low cost sulfur dioxide or bisulfite at some paper mills. Improved yields, above 90% dithionite based on borohydride, can be obtained by the use of a specific mixing sequence and an optimized pH profile (360,361). Electrochemical technology is also being offered for on-site production of sodium hydrosulfite solution (362). 

ElectrolyticaHy generated hypochlorite may be used for the oxidative destmction of cyanides (qv) or the sterilization of domestic wastes. Several on-site systems for swimming pool sterilization and municipal waste treatment works have been developed. One of these systems is described in Reference 124. On-site production and immediate use of chlorine is considered safer than the transportation of chlorine. 

Off-shore gas liquefaction of natural gas on oil platforms is often mentioned as an example of on-site production [5]. Natural gas today is flared as its transportation is not economic. Conversion on-site by conventional reactors suffers from the large weight of the equipment. Gavriilidis et al. state that 5 kg of support are needed to support 1 kg of equipment on an oil platform ]5]. light-weight micro reactors have the potential to use the precious area of the platforms better (Figure 1.26). 

Finally, the topic of standardization ( plug-and-play ) has gained interest. WiU there be modular flexible plants in the future, for multi-purpose and on-site production Concerning the latter, the chemical manufacture of hazardous and explosive substances has attracted readership over many years. 

Fig. 20. Chlor-o-Safe On-site production of sodium hypochlorite, Model S, ElectroCell Systems AB. Sweden [99]...

Alkaline electrolysers are at an industrial stage, especially commercialized for on-site production of ultrapure hydrogen for industrial applications. In general, this hydrogen is needed at low to moderate pressure, and the cost demand is set in comparison to the alternative, which is in general the supply by tube trailers. High purity water is fed to the electrolyzer. State-of-the-art commercial alkaline electrolysers typically operate at HHV systems efficiency of 60-75% [44], Current... 

This process is a lower-cost method of providing bromine chemistry to large cooling systems, where conventional BCDMH or similar chemistry is cost-prohibitive (see Section 6.2.7 on bromine chemistry). In addition, bleach is often used as a raw material, with sodium chlorite, for the on-site production of chlorine dioxide (see Section 6.2.6). 

I Y 159 13.2 h on-site production, limited commercial availability SPECT... 

Industrial Gases Atmospheric Process Gases Coatings Powders On-Site Production Plants Distribution... 

On-site production is one such opportunity. It has been a strong driver of growth for several years and will continue to be so in the near future. On-site production is a clear departure from the classic business model of a gases player. Instead of merely supplying gas, the gases company supplies a solution it not only develops an optimum supply concept for an industrial customer, but also builds, installs, operates, and maintains the on-site gas supply systems. 

Keywords US military, hydrogen, transportation, alternative energy, transit system, on-site production, commuter service, refueling station, public perception, nondestructive evaluation, codes, standards, permitting, safety, first responders, reliability, maintainability, hydrogen highway... 

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