Scrubber units

Increasing either the gas velocity or the liquid droplet velocity in a scrubber will increase the efficiency because of the greater number of collisions per unit time. The ultimate scrubber in this respect is the venturi scrubber, which operates at extremely high gas and liquid velocities with a very high pressure drop across the venturi throat. Figure 29-8 illustrates a commercial venturi scrubber unit... 

Air Flow Typical gas flow rates for a single-throat venmri scrubber unit are 0.2 to... 

Air Flow Typical gas flow rates for an orifice scrubber unit are 0.47 to 24 standard cubic meters per second (sm /sec) (1,000 to 50,000 standard cubic feet per minute (scfm)). 

If your facilrty has several pieces of equipment performing a similar service, you may combine the reporting for such equipment on a single line. It is not necessary to enter four lines of data to cover four scrubber units, for example, if all four are treating wastes of similar character (e.g., sulfuric acid mist emissions), have similar influent concentrations, and have similar removal efficiencies. If, however, any of these parameters differ from one unit to the next, each scrubber must be listed separately. 

Moisture in a gas stream might be water vapor from the air or a water scrubber unit, or it could be some other condensable vapor being carried in the gas stream. It is important in compressor volume calculations to know the moisture (or condensable vapor) condition of the gas. 

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). 

Typical gas flow rates for a single-throat Venturi scrubber unit are 0.2 to 28 sm3/sec (500 to 60,000 scfm). Flows higher than this range use either multiple Venturi scrubbers in parallel or a multiple throated Venturi. 

TRW Systems, Inc., conducted a laboratory-scale incineration study for the U.S. Army from 1973 to 1975 (9). Eleven individual pesticide formulations and three mixed pesticide formulations containing six different active ingredients (chlordane, 2,4-D, DDT, dieldrin, lindane, and 2,4,5-T) were incinerated in a liquid injection incinerator. The experimental apparatus consisted of a fuel atomizer, combustion chamber, afterburner, quench chamber, and scrubber unit. Destruction efficiencies exceeded 99.99% for a minimum 0.4-s residence time at temperatures above 1000°C with 45 to 60% excess air. 

The whole unit is accommodated in a fume cupboard fitted with a scrubber unit to remove the acidic fumes before emission to the atmosphere. The constructional materials of the fume cupboard should be able to withstand the heat radiated from the hotplate and heating blocks. A digestion tube containing a 350°C thermometer with the bulb embedded in a 2-cm layer of sand occupies one hole in each block. The hotplate can be connected to the power source via a time-switch, which can be set to come on approximately 1 hour before commencement of work this saves valuable time lost waiting for it to warm up. 

The charcoal in the scrubber unit was replaced more frequently to minimize nitroglycerine accumulation. 

For PCDD/F removal, overall removal efficiency across the scrubber unit was determined, masking any catalytic effect of trapped flyash. Flowever, the tests did identify an increase in PCDD/F concentration in the flue gas with an increase in gas temperature, in the region 100-200°C. 

Equipment List for the Proposed Wet Scrubber Units-Odor Control System for Collier County South Water Treatment Plant, Naples, FL (15)... 

Lay out your system configuration, attach the pipe hangers to the back-board and then insert the electrolyzer, and scrubber units into the pipe hangers. Adjust for tightness so that the units are held securely. Attach the rest of the components to the backboard however you wish. 

Aqueous solution processes and the properties of aqueous species are of prime interest in wet 1ime-limestone and other liquid phase scrubber units. Accordingly, thermodynamics properties of interest include, but are not limited to AH°, y, < ,... 

Oxidation and Sulfate Precipitation. As anticipated, most of the oxidation took place in the absorber/scrubber unit. The levels of oxidation in this unit ranged from an equivalent of 5 mole % of the SO2 removed, at O2 concentrations of 5.5 vol. % in the inlet flue gas, to 25 mole % at O2 concentrations of 8%. Oxidation throughout the remainder of the system amounted to an additional 1 to 5% of the SO2 removed. 

The sulfur dioxide in kraft recovery furnace gases can be readily scrubbed with sodium carbonate to produce sodium sulfite or sulfate as makeup for cooking liquor preparation. The absorbent liquor can be used in the scrubber units that collect part of the sodium carbonate and sulfate particulates that escape collection by the electrostatic precipitator. Particularly in Sweden, such afterscrubbers are sometimes used also to recover low level heat (110), and they could be extended to recover sulfur dioxide as well (111). The use of afterscrubbers to collect sulfur dioxide from kraft recovery furnace gases appear to be fairly common in Japan (27). 

Scrubber units are typically configured vertically and are located next to the fume hood as shown in Figure 8.7. They are also produced in a top mount version, in which the packing, spray manifold, and mist eliminator sections are located on top of the hood and the sump and liquid handling portion are underneath the hood for a compact arrangement taking up no more floor area than the hood itself. 

In the retention of volatile radioiodine species in a Venturi scrubber unit, two different stages have to be distinguished. The first one is the transfer from the venting flow to the liquid phase, the second one the prevention of revolatilization from the liquid phase even in the case of a continuing and long-lasting (up to 36 hours) venting flow. 

Carbon monoxide and methanol from the scrubber unit are fed to the reactor containing the catalyst and the solvent. The liquid product stream is depressurized in a flash vessel and divided in a gas and liquid phase. In this step the rhodium catalyst is separated from the crude acetic acid and is recycled to the reactor. It is critical for the process economics to avoid any rhodium metal loss in this step that could occur by precipitation and vaporization. The gas stream is scrubbed with methanol to recover the toxic and volatile methyl iodide and the off-gas of the scrubber system is flared. The liquid phase is sent to the light ends column (separation of light compounds, e.g., methyl iodide and methyl acetate). The bottom of this column (catalyst, water, and acetic acid) is recycled to the reactor. Wet acetic acid is sent to the drying column and dried acetic acid is obtained as bottom product. The overhead (mixture of acetic acid and water) is recycled back to the reactor. In the product column heavy by-products (major liquid by-product propionic acid) are removed from the dried acetic acid. The overhead is sent to the finishing column, where ultrapure acetic acid is obtained as a side-stream. 

Jet scrubber units are not very efficient as gas compressors or as gas absorbers, but they are simple to operate and almost maintenance ftee. They are particularly applicable to relatively small volumes of gas containing corrosive impurities. If necessary, two or more can be... 

In this installation, the jet scrubber units are constructed of fiber reinforced plastic (FRP) with PVC spinners in the spray nozzles. The tail-gas scrubber towers, tank, and ductwork are also constructed of FRP with polypropylene packing and mist eliminators. 

---