Vacuum systems stream jets

The caustic feed (Stream 1), entering the second effect from the left, contains 35% NaOH and is at 90°C. A vacuum system, here in the form of a steam jet, maintains a low operating pressure. The condenser, not shown, normally is a barometric unit. With heat supplied by vapor from the first effect, the second effect produces 42% NaOH, which then goes to the steam-heated first effect. The first-effect product liquor (Stream 4) is 50% NaOH at 136 = C. 

In a thermospray interface, a jet of vapour and small droplets is formed by heating the column effluent of an LC column or any other continuous liquid stream in a heated vaporizer tube. Nebulization takes place as a result of the disruption of the liquid by the expanding vapour that is formed upon evaporation of part of the liquid in the tube. A considerable amount of heat is transferred to the solvent prior to the onset of the partial inside-tube evaporation. This assists in the desolvation of the droplets in the lower pressure region. By applying efficient pumping directly at the ion source, up to 2 mL min i of aqueous solvents can be introduced into the MS vacuum system. The ionization of the analytes takes place by mixed mechanisms based on gas-phase ion-molecule... 

Most of the generated vapour is condensed in spray condensers which are equipped with circulation pumps and an EG cooler. The vapour that is still uncondensed is withdrawn from the gas phase with the help of a vapour jet which is located down-stream behind the spray condenser and generates the necessary vacuum in the reaction zone. The most critical part of the spray condenser system is the end of the pipe leading the vapour from the prepolycondensation reactors and the finishers into the spray condenser. The transition from a hot to a cold environment causes deposition of solid material onto the cold walls which has to be removed manually or by means of a mechanical scraper. 

Barometric condenser systems can be a major source of contamination in plant effluents and can cause a particularly difficult problem by producing a high-volume, dilute waste stream [8]. Water reduction can be achieved by replacing barometric condensers with surface condensers. Vacuum pumps can replace steam jet eductors. Reboilers can be used instead of live steam reactor and floor washwater, surface runoff, scrubber effluents, and vacuum seal water can be reused. 

Brine Dechlorination. In the mercury and membrane processes, the depleted brine leaving the cells must be dechlorinated before resaturation. Further acidification with hydrochloric acid to pH 2-2.5 reduces the solubility of chlorine by shifting the equilibrium point of hydrolysis and inhibits the formation of hypochlorite and chlorate. Chlorine discharged in the anolyte tank prior to dechlorination may be fed into the chlorine system. The dissolved chlorine of the brine then is still 400 -1000 mg/L, depending on pH and temperature. The brine is passed down a packed column or sprayed into a vacuum of 50 - 60 kPa, which reduces the chlorine concentration in the brine to 10-30 mg/L. The vacuum is produced by steam jet or liquid-ring vacuum pump. The pure chlorine gas obtained is fed into the chlorine stream. 

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