Sodium carbonate, ordinary washing soda, melts to a most powerful reagent. It dissolves all minerals, even silica — indeed, glass is made by dissolving silica and other minerals in molten sodium carbonate. Furthermore, it attacks organic matter ferociously. One process for disposing of halocarbon plastics, old tyres, leather scraps, and so on, submerges them in a sodium carbonate melt and blows in a trickle of air. The organics react to a useful fuel gas containing carbon monoxide and hydrogen. Their halogens and sulphur stay in the melt as halides and sulphide. Sadly, the contaminated carbonate is troublesome to recycle. It has to be dissolved in water, chemically purified, then re-evaporated and remelted.
To simplify this elegant process, Daedalus is extending it to fuel minerals as well. He points out the vast amount of fuel locked up in awkward and uncooperative geological forms — tar sands, low-grade shales, alluvial carbides, and so on. So DREADCO chemical engineers are now equipping a molten-carbonate rubbish-reducer with a second, fuel-processing stage. After digesting its charge of organic rubbish, the melt flows into another under-aerated vessel, where tar sand or shale is added. Its organic content burns incompletely to fuel gas, as before; its mineral content, silica or silicates, dissolves in the carbonate. The silica displaces the halides and sulphide, and the carbonate of the soda, as gases which can be scrubbed out of the fuel-gas downstream. The transformed melt consists of mixed silicates of sodium, calcium and the other metals in the fuel mineral. In fact it is simply molten glass, a useful product in its own right.
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