Configurations, scrubber

Figure 5.12 Variable cyclindrical Venturi scrubber configuration.

Figures 5.15 through 5.18 show examples of different scrubber configurations and operating modes.

FGD is used to control S02 emissions from coal and oil combustion from electric utilities and industrial sources. Impingement scrubbers are one wet scrubber configuration used to bring exhaust gases into contact with a sorbent designed to remove the S02. On occasion, wet scrubbers have been applied to S02 emissions from processes in the primary non-ferrous metals industries (e.g., copper, lead, and aluminum), but sulfuric acid or elemental sulfur plants are more popular control devices for controlling the high S02 concentrations associated with these processes. 

A third method is CO2 removal by physical absorption in a (sea)water scrubber (configuration 3). Because of the low costs of (sea)water, large quantities can be used and a stripping section is not necessary because the water is discarded. 

Factorial Test Results. Full or partial factorial tests have been conducted at Shawnee, primarily to investigate the effects of adipic acid concentration and pH on SO2 removal. These tests usually lasted 12 hours or longer, including at least 5 to 7 hours of steady-state operation. Scrubber configurations used were venturi alone, spray tower alone, combined venturi and spray tower, and TCA. Limestone was used in all scrubber configurations. Lime was used only with the venturi alone. Only the typical results from the TCA and spray tower tests are presented below to show the degree of effect of pH and adipic acid concentration on SO2 removal. 

Spray Tower. Figure 2 shows the SO2 removals reported by Head ( ) and by Burbank and Wang(10) for a limestone spray tower, plotted as a function of the net work input. The feed liquor pH was again 5.8 (stoichiometric ratio = 1.4 to 1.5). Gas velocities and slurry recirculation rates were systematically varied from 5.4 to 9.4 ft/sec, and 15 to 30 gpm/sq ft, respectively. The data include scrubber configurations with and without a venturi preceding the spray tower. All data are for single-loop mode of operation i.e., the venturi and spray tower were fed from a single EHT. 

Countercurrent spray scrubber FIGURE 45.4 Wet scrubber configurations. 

Scrubber Ttfpes and Performance The diversity of particulate scrubber designs is so great as to defy any detailed and selhconsistent system of classification based on configuration or principle of operation. However, it is convenient to cliaracterize scrubbers loosely according to prominent constructional features, even though the modes of operation of different devices in a group may vary widely. 

Configuring a control device that optimizes control of more than one pollutant often does not achieve the highest control possible for any of the pollutants controlled alone. For this reason, waste gas flows that contain multiple pollutants (e.g., PM and S02, or PM and inorganic gases) are generally controlled with multiple control devices, occasionally more than one type of wet scrubber. 

A pair of scrubbers operated alternately. In the normal configuration the scrubbers are operated in series. As the caustic in the upstream scrubber becomes depleted it is taken off line and the remaining scrubber becomes the prime tower. The off-line scrubber has the hypochlorite-laden inventory discharged to be replaced with fresh caustic, and is then brought back online as the downstream tower. This will be referred to as batch operation. The minimum changeover frequency in normal operation is probably less than a day. 

Dynamic simulations of a batch-operated scrubber with pump-around will be presented showing the effect of process configuration on destruction demands, where the method of hypochlorite destruction is a fixed-bed catalytic reactor. 

This chapter has therefore shown that cost minimisation of the treatment of hypochlorite effluent streams is achieved only through consideration of a wide range of process alternatives. The optimal solution for a given plant is dependent on a number of aspects, which include not only the rate and concentration of the stream as well as its required exit concentration, but also the configuration and operational mode of the caustic scrubber and any existing treatment system. 

Both concentrated and dilute waste were sent to a pair of John Zink thermal oxidizers equipped with adjustable venturi scrubbers for removal of particulates prior to stack discharge. Water process waste originating primarily from fermentation sectors was sent to the Carver-Greenfield evaporation system. The evaporator utilized a multistep oil dehydration process and was equipped with a centrifuge, waste heat boiler, and a venturi scrubber. The Clinton Laboratory reported an overall BOD and COD reduction of 90 and 99%, respectively, depending upon the configuration used. 

As stated earlier in this paper, FGD wet scrubbers can produce either calcium sulfite (the typical product) or calciiun sulfate. The DDO crystallizer is advantageous for either product. The following industrial case history describes the production of calcium sulfate dihydrate (or gypsum) product fi om an industrial in-plant weak sulfuric acid liquor using a DDO crystallizer configuration. 

Most CMP tools now feature integrated post-CMP cleaners. However, of these the vast majority are double-sided brush scrubbers. An example is the OnTrak cleaner shown in Fig. 14 and two brush types are shown in Fig. 15. Brush configurations consist of either a series of rollers [58] or opposing pancake serubbers. Typically, there are two brush stations, each of which... 

Separators are sometimes called gas scrubbers when the ratio of gas rate to liquid rate is very high. Some operators use the term traps to designate separators that handle flow directly from wells. In any case, they all have the same configuration and are sized in accordance with the same procedures. 

Figure 9. Configuration of the DS-IC system A, clean air input B, mass-flow controller C, permeation device chamber D and H, vents E, needle valve-rotameter F, needle valve G, mass-flow meter I, diffusion scrubber Jy scrubber liquid reservoir K, needle valve-rotameter L, suction pump M, injection valve Ny peristaltic pump O, eluent flow F, downstream chromatographic components and Q, sample loop. (Reproduced from reference 96.

Rorosity, 0.02 /im mean pore size, Hoechst-Celanese Corporation, Charlotte, fC) filled with a 300 /im dia. nylon monofilament (F) and connected to end-flared 300 pm i.d. in/out PTFE tubes (TT) through which the scrubber liquid (in the present case, water) is pumped. The membrane tube is suspended concentrically within a PTFE jacket tube TJ (5 mm i.d. and maintained in a linear configuration by an external rigid tube, not shown). Air is sampled through the tee-ports PT and end-seals are provided by a series of nested plastic tubes (NP). Greater details of construction are available elsewhere (12). This D.S. was used for the H2C>2 translation system (hereinafter called system 1) with an active membrane length of 40 cm. 

The configuration chosen for the plant produces salable by-products, rather than waste products. The flyash from the plant is sold to a zinc smelter. The gypsum produced by the scrubber has been labeled by the state of California as appropriate for agricultural uses. It is sold as a soil conditioner. The steel slag from the plant is sold to a cement kiln for use in cement production. 

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