Unit operations, liquid systems carbon

Molten carbonate fuel cells (MCFCs) are high-temperature systems that use an immobilised liquid molten carbonate salt as the electrolyte. Salts commonly used include lithium carbonate, potassium carbonate and sodium carbonate. Typically MCFC units have an operating temperature of around 650°C and an efficiency of around 60%. (This can rise to as much as 80% if the waste heat is used for cogeneration.)... 

Generally speaking, whenever a substance is distributed between two insoluble phases, a dynamic equilibrium of this type can be established. The various equilibria are peculiar to the particular system considered. For example, replacement of the water in the example considered above with another liquid such as benzene or with a solid adsorbent such as activated carbon or replacement of the ammonia with another solute such as sulfur dioxide will each result in new curves not at all related to the first. The equilibrium resulting for a two-liquid-phase system bears no relation to that for a liquid-solid system. A discussion of the characteristic shapes of the equilibrium curves for the various situations and the influence of conditions such as temperature and pressure must be left for the studies of the individual unit operations. Nevertheless the following principles are common to all systems involving the distribution of substances between two insoluble phases ... 

According to the vendor, the capital costs for the treatment system include a 200-actual cubic-feet-per-minute (ACFM) vacuum pump, two transfer pumps, a carbon steel knockout pot, and associated instrumentation and piping. Operation and maintenance costs for the system include estimates for additional granular activated carbon (GAC) units, liquid- and vapor-phase analysis, weekly monitoring, electricity, and routine maintenance. These costs vary, depending on the monitoring requirements, contaminant concentrations, and other variables (D13124Y, p. 492). 

The correlation for distillation is based on limited data for systems of hydrocarbons and chlorinated hydrocarbons, that for absorption on the performance of hydrocarbon absorbers and the scrubbing of ammonia and carbon dioxide with water, p/ is in units of centipoises, H in imits of mole-fraction ratios, and p L is the molar density of the liquid solvent in lb mol/ft. Note that gas absorbers generally have much lower plate efficiencies than distillation coliunns due primarily to their lower operating temperatures. 

At the Ford Motor Company s spark plug plant in Fostoria, Ohio, trichloroethylene vapor in the air from degreaser units is recovered by adsorption on activated carbon. Two 72-in.-diameter adsorbers are used, each containing 1,300 lb of carbon pellets. The system is reported to be capable of recovering 400 to 450 gal. of liquid trichloroethylene per day with a collection efficiency of over 90%. Operating costs were only about 3% of the value of the recovered solvent (Anon.. 1969). 

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