Scrubber foaming

Most large amine spills are a consequence of scrubber foaming. The amine solution froths up on the trays and is carried overhead with the sweet gas. This leads to the following scenario, beginning at the refinery s fuel gas scrubber ... 

The discharge of copious quantities of chemicals directly to the atmosphere can give rise to secondary hazards, especially if the materials are toxic and can form a flammable atmosphere (e.g., vapor or mist) in air. In such cases, the provision of a knockout device (scrubber, dump tank) of adequate size to contain the aerated/foaming fluid is required. 

Foam scrubber A cleaning device that uses foam as a collecting medium for particulate matter in a gas stream. 

Operating instructions specified that 50% sodium hydroxide solution, sodium hypochlorite solution and sodium EDTA solution were to be added separately by pumping into an off-gas scrubber unit, when the exotherms would be dissipated slowly in the solution tank. An attempt to simplify the operation by premixing the 3 solutions in a drum before pumping the mixture, led to vigorous foaming decomposition. Mixing the cone, alkali with the bleach caused the oxidant to become heated by the heat of dilution of the former, and oxidation of the EDTA component then proceeded exothermically with decomposition (and evolution of carbon dioxide). 

Overall, horizontal vessels arc more economical for normal oil and gas separation, particularly where there may be problems with emulsions, foam or high gas-oil ratios. Vertical vessels work more effectively in either low or very high GOR applications, such as scrubbers. 

The foam also contains decon solution.. . . Then the secondary tent is placed over the primary and is hooked up to the Air Pollution Control (APC) equipment. The scrubber, the first piece of the APC, will contain a NaOH solution. After use, the waste liquid will be disposed of and will consist of the NaOH, some Oil of Wintergreen Residue [Methyl salicylate, an agent simulant used in testing], some explosive residue, and decon agents in the foam. 

TCA Scrubber. Head ( ) reported SO2 removal efficiencies of a limestone TCA operated at a feed slurry pH of 5.8 and three levels each of gas velocity and slurry recirculation rate. Those data are plotted in Figure 1 as a function of the net work input, calculated according to Equations (1) and (2). The partially closed symbols denote tests with three beds of nitrile foam spheres, each bed... 

For aqueous systems such as acid gas scrubbers and caustic scrubbers (where mercaptans are removed from gasoline), hydrophobic silicas or polyglycols are used. The specific chemistries and applications for both aqueous and nonaqueous foaming situations will be discussed. 

Caustic Scrubbers and Sour-Water Strippers. Caustic scrubbers and sour-water strippers are used to remove sulfur from a variety of products, gases, and waste streams. Foaming is a fairly common occurrence in these systems because of contaminants found in the streams. 

The wet mechanical scrubbers include simple shower, vortex, foam, inertial, stream and rotational separators. 

Wet foam scrubbers. In wet foam scrubbers, the gas streams through a gridded or perforated plate, on which the water is poured. At a certain stage in the operating regime, foam is formed and particles from the gas to be purified are retained on the surface of bubbles. The velocity of the gas stream through the perforated plate ranges from 0.5 to 2 m s . The separation limit is between 2 and 3 fim. The specific water consumption is... 

The wet foam scrubbers can be used advantageously for retaining dust as well as gaseous pollutants. For this reason their wide use in the future is to be expected. For a more detailed description of their function see references [5, 6]. 

Where there is direct evidence that surface-active foaming behaviour does not occur, it is possible to take advantage of any disengagement which may occur in the vessel. This is unlikely to have much effect on the required vent area, but it can considerably reduce the complexity and cost of downstream equipment such as dump tanks and scrubbers. 

Dissolved air flotation or induced air flotation are commonly used techniques in the oil refining industry for the removal of both oils and suspended solids. The coal industiy has been investigating foam flotation technology as well. One use would include cleaning the wet scrubber mr pollution control devices used in coal-buming power plants. ... 

Textile uses are a relatively stable area and consist of the lamination of polyester foams to textile products, usually by flame lamination or electronic heat sealing techniques. Flexible or semirigid foams are used in engineered packaging in the form of special slab material. Flexible foams are also used to make filters (reticulated foam), sponges, scrubbers, fabric softener carriers, squeegees, paint applicators, and directly applied foam carpet backing. 

The absorption efficiency of the scrubber is dramatically reduced by the presence of any active detergent. The theory is that the active forms a boundary layer between the gas-phase and the caustic, preventing or at least limiting contact. Also, foam formation will hamper normal operation of the scrubber. Hence for the efficient operation of the scrubber system, the ESP s primary function is to prevent the active contamination of the scrubber liquor, i.e. all organic acid mist and droplets should be trapped in the ESP. 

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