SO2 scrubber

If the gas to be measured contains sulfur dioxide, it has to be scrubbed from the gas before oxidation of the reduced compounds can occur. The gas is scrubbed using an SO2 scrubber. This may contain citrate buffer solution (potassium citrate or sodium citrate). The collection efficiency of the sulfur diox ide may be as high as 99%. 

Rare earth containing catalysts are useful in stationary pollution control devices as for example lanthanum titanate catalysis in the reduction of sulphur dioxide with carbon monoxide to yield carbon dioxide and elemental sulphur. The disposal of elemental sulphur is far less hazardous than that of effluent from an SO2 scrubber. 

Construct a flowchart of the process and completely label the streams. Show the details of only one train in the SO2 scrubber operation. 

In the past, specifically prior to the required installation of SO2 scrubbers, most chimneys were subjected to hot, dry, seldom acidic conditions. Typical flue gas temperatures exceeded 400°F and were therefore above the acid dew point during normal plant operation. Furthermore, the plant itself experienced fewer shutdowns due to the intermittent operational difficulties inherent within the scrubbed gas systems themselves. Thus, chimney linings were not exposed to severe acidic conditions other than at infrequent start-ups and shutdowns, For this reason, wet acid corrosion was not a major design factor, and chimneys were relatively simple to design, construct and maintain. There were a few relatively common designs, which will be briefly described. 

Estimate the water requirement of a spray dryer (dry SO2 scrubber) at a coal-fired incineration facility that treats 150,000 Ib/h of a flue gas at 2180°F. Assume an approach temperature to the adiabatic saturation temperature (AST) of 40°E The AST can be assumed to be 180°R... 

SO2 scrubbers (double alkali, Catox, Tyco) power usage 30 to 40 kW/m /s. 

The bulk of the limestone dissolution in most SO2 scrubbers occurs in the 5-6 pH range. Thus, both solution mass transfer properties and the nature of the limestone must be considered at typical operating conditions. Therefore, the pH, solution composition, solution buffer capacity, and the nature of the limestone are important considerations when designing for maximum limestone utilization. This paper deals primarily with the measurement of the influence of limestone properties on the overall dissolution rate. 

Two diesel fuels have been used. The first one was a certified fuel, Haltermaim CEC RF-03-A84, containing 0.14 wt % sulfur. The second fuel was a low sulfur fuel, obtained fi-om van Gelder Aardolie B.V., with less than 0.001 wt % sulfur. In the case that certified fuel was used, the MIPAN ammonia analyser was equipped with an SO2 scrubber. 

Environmental concerns have prompted major developmental trends in epoxy coating systems. Thus epoxy coating systems have been developed to meet the high-temperature and hot-add environments to which SO2 scrubbers and related equipment are subjected. Ambient curable epoxy systems have been developed to provide resistance to concentrated inorganic adds. 

Boiler size and SO2 scrubber are reduced The technology is not yet considered mature Polymeric air separation membranes can be used for the separation of oxygen from nitrogen (commercialized, for example, by DuPont, Air Liquid, etc.). 

High chemical resistance and fire resistance. Used in SO2 scrubber service. 

Mansfeld, F., The Effects of SO2 Scrubber Chemistty on Corrosion, Report CS-4847, Electric Power Research Institute, Palo Alto, CA Pal Dike, E. R. and Shim, W. Histoiy of Electrochemical Protection of Flue Gas Desulfurization Reaction Tanks, Paper No. 0580, Corrosion/2000, NACE International, Houston, TX, 2000. 

Washing water should be directed into the SO2 scrubber water pit ... 

The exhaust gas leaving the ESP, virtually free from any organic acid and sulphuric acid mist, enters the SO2 scrubber made of acid-proof construction material. The caustic scrubber equipment consists of ... 

The liquid effluent leaving the SO2 scrubber consists of a solution of caustic soda, sodium sulphite, sodium sulphate and traces of active matter. At 98% SO2 SO3 conversion (steady-state running conditions) about 80 kg/h of a 10% sodium sulphite solution will leave the scrubber system, based on a 10(X) kg/hr sulphonation plant (see table 19). The alkaline solution is collected in an acid/caustic-resistant pit. It is common practice to dilute this liquid stream with other effluent streams (ex slurry-making and powder manufacture) and to re-use it in the detergent powder manufacturing plant as dilution water. 

Due to the excess of caustic soda in the solution leaving the SO2 scrubber (pH 9-12), this liquid can also be used to neutralise liquid acid effluents that cannot be disposed of in an SO3 absorber and oleum/sulphuric acid ex the SO3 cooler system. To avoid SO2 formation due to decomposition of sodium sulphite (Na2S03), the pH should never be lower than 8. 

The oleum collection vessel should be fitted with a means of determining the level (sight glass) and a high-level alarm to warn the operator of the need to empty the vessel and to give an indication, from records, of excessive oleum production. The discharge of oleum from the vessel is normally a manual operation, although in the case where oleum is pumped to the SO2 scrubber, hard-wired interlocks must be used to prevent the transfer of oleum when the scrubber is not in operation. 

In order to ensure that the pH in the SO2 scrubber does not fall excessively, leading to gas emission, it is essential to control the addition of sodium hydroxide to the unit. Cascade control systems can be used, where the pH transducer is used to define a set point for a flow control loop. However, variable-speed metering pumps are more commonly used, the speed of the pump being controlled directly by pH. 

Crevice-Corrosion Tests in Simulated SO2 Scrubber Environment ... 

FGD in Europe began as local authorities in some Gennan states required the retrofit of SO2 scrubbers to handle a portion of the flue gas from certain boilers that were particularly Koblematic. By 1983, some 14 units had been installed. The environmental movement built rapidly in Germany, and a law known as GFAVO passed in June 1983. It established the federal limits shown in Table 7 2, and required compliance by June 1988. In spite of the feverish activity this schedule required, the industry responded and nearly all of the some 150 affected units complied on schedule. However, the cost and disruption it caused probably influenced the framers of the flexible, two-phase acid rain law enacted in the U.S. in November 1990. 

McGraw-Hill, 1991, EPRI Official Few Utilities Willing to Try New SO2 Scrubber Technologies, Utility Environment Report, Dec. 13, p. 7. 

Radian Corp., 1976, Experimental and Theoretical Studies of Solid Solution Formation in Lime and Limestone SO2 Scrubbers—Vol. J, Final Report, EPA-600/2-76-273a, October. 

Samanta, S. C., 1977, Physical and Chemical Characteristics of Stabilized SO2 Scrubber Sludges, paper presented at the Sixth Environmental Engineering and Science Conference, University of Louisville, Louisville, KY, Feb. 28. 

The wet solvent from the centrifuge is combined with the overflow stream from the surge tank and is pumped to a solvent stripper, where the water (3.5 wt%) is stripped from the solvent to maintain the water balance in the system. The water-vapor flow in the stripper removes unreacted H2S and most of the other gases, such as CO2, co-absotbed in the solvent. Most of the lean solvent exiting the bottom of the solvent stripper is used in the SO2 scrubber to absorb the SO2 from >he combustion gas leaving the furnace. The overhead vapor is condensed in a partial condenser. Approximately 65% of the condensate is fed to a sour-water... 

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