Seaboard process

SEABOARD PROCESS. Method of removing hydrogen sulfide from a gas by adsorption in sodium carbonate solution. Sodium bicarbonate and sodium hydrosulfide are formed. Blowing air through the solution, hydrogen sulfide is released and carried off, and the sodium carbonate is regenerated. 

A flow sheet of a typical Seaboard-process installation is presented in Figure 5-36. The circulating solution normally contains 3.0 to 3.5 wt % sodium carbonate. This is used to wash the gas in a countercurrent absorber column and is regenerated in a separate actifier column by a countercurrent flow of low-pressure air. The principal chemical reaction in the process is as follows ... 

Although it has been reported that the spent Seaboard process solutions have some value because of their NaSCN content, in most cases their disposal is a serious problem from the water pollution standpoint. 

Design and Operation. The absorber used in Ferrox installations has a lower section, or saturator, and an upper section, the absorber proper, llie saturator contains a continuous liquid phase, several feet high, through which the raw gas is bubbled before it enters the upper section. The function of the saturator is to provide sufficient contact time to complete the reaction between sodium hydrosulfide and ferric oxide before regeneration of the solution. If essentially complete reaction is achieved, thiosulfate formation in the regenerator is kept at a minimum. The upper part of the absorber contains sprays and wooden hurdles similar to those used in the Seaboard process and usually has a total height of 60 ft (Sperr, 1926). 

The accumulation of sediments in estuaries appears to be so effective that Meade (1981) has estimated that, "Probably less than 5 percent of all river sediment discharged into the tidal waters of the Atlantic seaboard is deposited on the floor of the continental shelf or the deep sea". These sediments contain an often dramatic imprint of human activity and impact on the estuary and its watershed. But it is an imprint which results not only from the input of materials, but also from the interaction of a great variety of physical, chemical and biological processes in the estuary. We are only beginning to learn to read that record, but the early results suggest that we may learn more about what flows between rivers and the sea from the humble muds on the estuary floor than we can from the water above. 

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