Flue Gas Treatment - The Beco "Alka/Sorb" Process
The Beco "Alka/Sorb" process is a Dry/Wet scrubbing sequence originally developed in 1985 for the treatment of toxic incinerator flue gases. Beginning in 1989, the process was applied to medical and hazardous waste incinerators. The "Dry/Wet" process has since been designated as MACT by the USEPA for medical waste incinerators. Typical stack test emissions data for the Alka/Sorb gas-cleaning system are shown in Table 1.
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Alka/Sorb Process
A complete Alka/Sorb Dry/Wet system is shown in Figure 1A-1B. The. system comprises a basic dry scrubber module, in series with an efficient tail-gas wet scrubber. The combination of dry and wet scrubbing yields a fail-safe flue gas treatment system with total operating flexibility and consistent emission levels.
Dry-Scrubber Section
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Figure 1A-1B
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The Dry Scrubber process module, Figure 1A, is the basic component of the dry-wet system, and comprises the following stages:
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- Gas Cooling
- Diox-BlokŪ Sorbent Injection
- Alkaline Reagent Injection
- Fabric Filtration
Wet Scrubber Section
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Table 1
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The wet scrubber section of the Beco Alka/Sorb Process is the patented source of the unique capabilities of the Dry/Wet system. The wet section is comprised of an acid recycle quench, a mist eliminator/separator and a tail-gas wet scrubber, all operating under "zero-liquid-discharge" (ZLD) conditions.
"Zero Liquid Discharge" (ZLD)
- Quench: In ZLD, the hot gases leaving the baghouse ares quenched with a recycle stream of dilute HCl generated by absorption of the residual HCl in the gas. HCl quenching provides for chemical removal of any residual mercury in the gas, and remaining dioxins.
- Blowdown to Incinerator: In the ZLD operation, the trickle acid blowdown stream from the quench stage is sprayed into the incinerator. Because the upstream dry stage removes 95-99% of the HCl, only 1 to 5% of the initial acid load arrives at the ZLD wet end.
- Tail-Gas Scrubber: The ZLD tail-gas scrubber polishes the HCl to final emission specifications. A zero water balance is achieved in the ZLD by using makeup water as the sole water supply to the tail-gas scrubber. This not only closes the loop on the water balance, but also provides for use of the maximum equilibrium absorption range of the water-HCl system.
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To learn more about Flue Gas Treatment please contact us at becoengco@aol.com
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