Scrubber solution

Prescriibbing (vessel containing scrubber solution between vacuum source and batch vessel). High concentration of off-gases resulting in overpowering abatement equipment. 

O If gas scrubbing is practiced, what is done with the spent scrubber solution Could it be convened to a useful product ... 

The checkers used a gas-inlet tube without a fritted-glass tip and aqueous 30% sodium hydroxide as scrubber solution. 

Quench elbow and primary scrubber. Here, the gases are scrubbed in a packed tower scrubber for particulates and acid gases, using a scrubber solution with a pH of 7.0 to 8.5. The recirculating scrubber liquor is cooled and, in turn, cools the hot gas from 1,000°F to approximately 60°F. 

Another gas of environmental interest is SO2. Collection of ambient air containing SO2 in a dilute H2O2 scrubber quantitatively converts SO2 to S04 2. The scrubber solution can then be injected directly into an IC and SO2 is determined as S04 2 (9). This method has the advantage over other methods (e.g. West-Gaeke) in that the collection solution is temperature stable. 

Mercury or cadmium in the contaminated material may be volatilized during treatment and therefore would have to be captured by the off-gas treatment system. If mercury or cadmium is present in the off-gas waste, it will be captured in a scrubber solution that would then require drying and stabilization prior to disposal at a landfill licensed under Resource Conservation and Recovery Act (RCRA) criteria. 

Figure 4. Diffusion scrubber device for H202 removal from air, consisting of the following A, Teflon tubing adaptor By Teflon Swagelok union C, 6-mm o.d. glass tube D, air outlet E, porous Teflon tube (2 mm i.d. x 30 cm, 70% porosity) F, 8-mm i.d. glass tube G, scrubber solution with concentric Teflon displacement rod H, air inlet and /, Teflon tube connection to porous Teflon tube. Cross section inset a, 8-mm o.d. (6-mm i.d.) glass tube b, air stream c, porous Teflon tube d, H20 scrubber solution and e, Teflon displacement rod. (Reproduced from reference 53. Copyright 1986 American Chemical Society.)...

Partridge, J. A Bosuego, G. P. Waste Management of Mercuric Nitrate Off-Gas Scrubber Solution. A Laboratory Study. HEDL-TME 79-11, Hanford Engineering Development Laboratory, Richland, Washington, 1979. 

To avoid buildup of phosphates, sulfates, and chlorides in the scrubber solution, a portion of the scrubber stream is removed from the system and evaporated to dryness. The resultant dry salts are then placed in drums for storage. The evaporation step requires large amounts of energy. The use of dual alkali scrubbing technology could avoid the need to evaporate large amounts of water to produce a solid waste. 

Nitric acid and water are condensed in the off-gas scrubbing system to dissolve the entrained calcine. The off-gas scrubber solution is recycled... 

Calcium Sulfite Deposition. Calcium sulfite (CaS03 %H20) is formed in the scrubber under those conditions that favor sulfite formation. These conditions are apparent when one considers the sulfite-bisulfite equilibrium and compares the relative solubilities of the corresponding calcium salts. As seen in Figure 2, extremely soluble bisulfite in solution changes to relatively insoluble sulfite when the solution pH shifts from 4 to 10. When SO2 is absorbed, the scrubber solution is usually between pH 4 and 6 and, therefore, the predominant species is... 

Further analysis of the data in Table II reveals apparent irregularities in performance of the process. For example, at an elapsed time of 61 hr, scrubber solution was being regenerated at a rate of 2.1 liters/hr to supply ammonia for the vapor-phase reaction. Removal eflBciency was only 77%. Six hours later, while SO2 content of the inlet gas was higher (1000 vs, 910 ppm), scrubber solution flow rate to the regenerator was zero, but the SO2 content of the purifled gas was only 10 ppm removal... 

If all SOo is not converted to a solid salt, part or all of the remainder is absorbed during the scrubbing operation. The degree to which this action occurs appears to be directly proportional to the pH of the scrubbing solution and the rate at which scrubber solution is recycled to the distribution plate. 

At any given flow rate of scrubber solution to the regenerator, the volume of ammonia regenerated appears to vary directly with solution pH, salt concentration, and regenerator temperature (up to about 220°F). 

Excess sodium hydroxide solution (metal oxide) must be available at all times in the regenerator for reaction with the scrubber solution. 

Fig. 8-21. Analysis of inorganic anions in the scrubber solution of a flue gas desulfurization plant. - Chromatographic conditions see Fig. 8-16 injection 50 pL sample (1 100 diluted).

Fig. 8-22. Analysis of chromium(VI) in a scrubber solution from the flue gas desulfurization. — Separator column IonPac CS5 eluent 0.002 mol/L pyridine-2,6-dicarboxylic acid + 0.002 mol/L Na2HP04 + 0.01 mol/L Nal + 0.05 mol/L NH4OAC + 0.0028 mol/L LiOH flow rate 1 mL/min detection photometry at 520 nm after reaction with 1,5-diphenylcarbazide injection 50 pL sample (1 10 diluted).

Fig. 8-23. Analysis of ammonium in a scrubber solution from flue gas desulfurization. - Separator column IonPac CS2 eluent 0.03 mol/L HC1 flow rate 1 mL/min detection fluorescence after reaction with OPA injection 50 pL sample (1 5 diluted).

Formic acid, added to some scrubber solutions for pH control, can be separated from inorganic anions and thus be determined with the aid of ion-exclusion chromatography. A corresponding chromatogram is depicted in Fig. 8-25. 

Fig. 8-26. Analysis of nitrite in a scrubber solution from flue gas denitrification. - Separator column IonPac AS3 eluent 0.0028 mol/L NaHC03 + 0.0022 mol/L Na2C03 flow rate 2.3 mL/min detection suppressed conductivity injection 50 pL sample...

Scrubber solutions heavy metals, and inorganic anions... 

---