collection efficiency over a wide range of inlet gas flow rates. The throat of the venturi can be automatically adjusted by moving a slide gate with a fast-response stepping motor. A recycled stream of quench brine from the scrubber bottoms quenches the gas in the venturi. A solution of 18 weight percent sodium hydroxide is added to the venturi quench brine to maintain the condensate stream at a pH of approximately 9.0 (8.0 to 9.5) to ensure that the acid gases in the vapor feed are neutralized and to reduce corrosion.
Separated liquid leaving the venturi drains by gravity to the scrubber bottom where a sump provides storage and surge capacity for the recirculation pump. Condensate from the scrubber section above the venturi inlet to the tower is added to the sump through the scrubber recirculation pump discharge line to make up for the flash evaporation that occurs in the venturi quencher. Process water can be added as additional makeup. Excess scrubber bottoms are sent to the energetics hydrolysate storage tanks or to the spent decontamination-solution storage tank.
The scrubber tower is based on commercial designs and includes a chimney tray, a packed bed, and a mist eliminator pad. The recirculated scrubber solution is cooled to maintain the scrubber exit gas temperature at 100ºF or less. A crinkled Hastelloy C® (or equivalent) wire mesh mist eliminator pad is provided above the scrubber liquid distributors for the packed bed to remove large mist droplets in the gas leaving the scrubber tower. The gases exiting the scrubber are heated in an air reheater to 95°F to prevent condensed liquids from entering the blower and to reduce the relative humidity of the blower discharge as it is fed via the ducting to the MDB HVAC carbon filters.
The scrubber gas discharge blower provides an induced draft for proper operation of the OTM and in turn for removing gases from the MPT main chamber and air locks. The blower has a variable frequency drive to accommodate variable off-gas flows during MPT operations. Key components in the OTM, particularly the pumps and blower, will be provided with installed spares to give added assurance of high reliability.
Finding. Except for the first-of-a-kind bulk oxidizer units, the off-gas treatment for the MPT uses design concepts found in commercial, high-reliability, off-gas cleanup systems. The venturi scrubber design is a mature technology.