Waste gases, scrubbing

Succinic acid has a diverse range of applications in the synthesis of specialty chemicals used in agriculture, foods, medicine, textiles, plating, and waste-gas scrubbing (Winstrom, 1978). Currently, succinic acid is produced via the hydrogenation of maleic anhydride to succinic anhydride and hydration to succinic acid (Winstrom, 1978 Zeikus et al., 1995). The thermophylic anaerobic bacteria Clostridium thermosuccinogenes can convert inulin to succinate and acetate as major... 

Metallurgical and inorganic chemical industries waste gas scrubbing Reduction of iron ore Reduction of gold roasting Biomass pyrolysis... 

The organic chemical industry uses NaOH for saponification reactions, production of anionic intermediates, etherification and esterification, basic catalysis, for waste gas scrubbing and for waste water neutralisation. 

Decomposition by Caustic Scrubbing. The waste gas stream is led through packed towers where a sodium hydroxide solution is introduced at the top of the towers. Venturi scmbbers can also be used. Makeup sodium hydroxide is added under pH control (32). 

A venturi scrubber aeeelerates the waste gas stream to atomize the scrubbing liquid and to improve gas-liquid contact. In a venturi scrubber, a "throat" section is built into the duet that forces the gas stream to accelerate as the duct narrows and then expands (refer to Figure 14). As the gas enters the venturi throat, both gas velocity and turbulence increase. 

Orifice scrubbers generally do not require precleaning, unless the waste gas contains large pieces of debris. Precooling may be necessary for high temperature waste gas flows which increase the evaporation of the scrubbing liquid. 

Limestone scrubbing A process using a ground limestone and water mix to neutralize sulfur dioxide in waste gas products. 

The waste gas and scrubbing liquid can be put into contact according to the counterflow or cross-flow principle. A counter-flow scrubber, as indicated in Fig. 3, is a... 

Sommar, J., Lindqvist, 0.. and Stromberg, D. Distribution equilibrium of mercury (11) chloridebetween water and air applied to flue gas scrubbing. J. Air Waste Manage. Assoc., 50(9) 1663-1666, 2000. 

Units stabilize their own off-gas scrubbing and filtration waste, thus preventing the creation of secondary waste streams. 

Waste Gas Problems. The gases produced in the calcination kiln are cooled in a heat exchanger, and entrained pigment is removed, washed, and recycled to the process. The S02 and SOa formed during calcination are then scrubbed from the gases to form dilute sulfuric acid which is recycled. 

Chemical scrubbing systems for SO/ absorption fall into two broad categories (a) Disposable systems and (b) regenerative systems. Typical of systems in use for a number of years are those that use an aqueous slurry of an insoluble caldum compound, which can be discarded after use. Disposable 02-removal systems use aqueous slurries of finely ground materials, such as lime, limestone or dolomite, to produce a mixture of insoluble sulfites and sulfates. On passing through the scrubber, S02 from the waste gas dissolves to form sulfurous acid S02 ... 

Korischem and Werner [49, 50] simulated the procedures of flue-gas scrubbing of an industrial waste combustion plant. Their model considered the mass and heat transfer process between gas and liquid phase by neglecting the solids present in the suspension. 

Aurousseau et al. [109] electrochemically scrubbed S02-containing waste gas. The sulfur dioxide (0.7%) was dissolved in 0.5 M sulfuric acid, transported to the electrode, and finally oxidized at the graphite anode. The oxidation was limited by the transport of sulfur dioxide to the electrode as well as by poor reaction kinetics at the electrode. The use of three-dimensional electrodes was suggested to alleviate these problems. 

A waste gas containing SO2 (a precursor of acid rain) and several other species (collectively designated as A) is fed to a scrubbing tower where it contacts a solvent (B) that absorbs S02- The solvent feed rate to the tower is 1000 L/min. The specific gravity of the solvent is 1.30. Absorption of A and evaporation of B in the scrubber may be neglected. 

The SO2 scrubbing tower described in Problem 4.26 is to be used to reduce the SO2 mole fraction in the waste gas to a level that meets air quality control regulations. The solvent feed rate must be large enough to keep the SO2 mass fraction in the exit liquid below a specified maximum value. 

Capture of the C02 produced by combustion of natural gas as the reformer fuel is not addressed in the above-described scenarios. The possible approaches to sequester C02 from the reformer furnace would be (i) oxycombustion or (ii) flue gas cleanup. For oxycombustion, natural gas would be burned in pure 02, producing a waste gas containing only C02 and H20. The water can be removed by compression and cooling to produce a pure C02 stream at pressure for sequestration. Removal of C02 from the flue gas would involve either scrubbing of the waste gas with aqueous or nonaqueous solvents or the use of another adsorption-based C02 removal process. 

However, chemical oxidants impose higher reagent costs. Flue gas scrubbing of the waste water for sulfide removal may only be used when it is acceptable to vent hydrogen sulfide with the spent flue gases at the site of operations. 

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