Treatment of Gaseous Effluents

Gaseous effluents containing chlorine arise from various sources and must be treated in such a way as to obtain a tolerable concentration of chlorine when they are released into the air. The vent gas may contain other substances, such as hydrogen, organic compounds, CO, etc., which must be considered in design and operation of an effluent treatment installation [248], [249]. 

To avoid any formation of solid salts, the recommended concentration of caustic soda is 22 wt%. The operating temperature should not exceed 55 °C under normal conditions a temperature of ca. 45 C is usual. A cooling system may be necessary. In large chlorine absorption units, the sodium hypochlorite solution that is produced can be used in other processes. Where this is not possible, several methods can be used to decompose the hypochlorite controlled thermal decomposition, catalytic decomposition [250], acidification, for example, with suliiiric acid 

The choice of material [251] depends on the design and operating conditions and must take into account all circumstances. A chlorine manufacturer should be consulted to confirm the suitability of a material. Any use of silicone materials in chlorine equipment should be avoided. 

Dry Chlorine Gas (water 40 ppm by weight). Carbon steel is the material most used for dry chlorine gas. It is protected by a thin layer of ferric chloride. For practical purposes the recommended temperature of these materials is 120 C. High-surface areas, such as steel wool, or the presence of rust and organic substances increase the 

The resistance of stainless steels to chlorine at high temperature increases with the content of nickel. For stainless steels containing less than 10wt% nickel, the upper temperature limit is 150 C. High-nickel alloys, such as Monel, Inconel, or Hasteloy C, are suitable up to 350-500 °C. Poor mechanical strength limits the use of nickel. Copper is used for flexible connections and coils, but it becomes brittle when stressed frequently. 

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Processing and Treatment of Gaseous Effluent Streams, 43 Effluent Management, 44... 

Since bacteria are able to retain their dehalogenase activity after dehydration, this new process could allow direct continuous treatment of gaseous effluents. The two main points are that there is no need to transfer the pollutant in an aqueous phase and there is also no longer limitation by solubility, and secondly that microorganisms are no longer growing. If we consider that transfers in the gas phase are much more efficient than those in the liquid phase, this also means that the rate of degradation should be far less limited by transfer and diffusion rate of the... 

Treatment of gaseous effluents—Polymeric as well as low-molecular-... 

FIGURE 25.16 Schematic representation of the coupled separation and chemisorption of H2S in the treatment of gaseous effluent using a microporous membrane containing ZnO nanoparticles. 

Paviet-Hartmann, P, W. Kerlin, and S. Bakhtiar. 2010. Treatment of gaseous effluents from recycling A review of the current practices and prospective improvements. Proceedings of the NEA/ OECD Workshop on Actinide and Fission Product Partitioning and Transmutation Exchange Meeting, November 1-5, San Francisco, CA. 

Euro Chlor Techn. Publ. 76/52, Equipment for the Treatment of Gaseous Effluents Containing Chorine , 9th ed., October 1986. 

Membrane technology may become essential if zero-discharge mills become a requirement or legislation on water use becomes very restrictive. The type of membrane fractionation required varies according to the use that is to be made of the treated water. This issue is addressed in Chapter 35, which describes the apphcation of membrane processes in the pulp and paper industry for treatment of the effluent generated. Chapter 36 focuses on the apphcation of membrane bioreactors in wastewater treatment. Chapter 37 describes the apphcations of hollow fiber contactors in membrane-assisted solvent extraction for the recovery of metallic pollutants. The apphcations of membrane contactors in the treatment of gaseous waste streams are presented in Chapter 38. Chapter 39 deals with an important development in the strip dispersion technique for actinide recovery/metal separation. Chapter 40 focuses on electrically enhanced membrane separation and catalysis. Chapter 41 contains important case studies on the treatment of effluent in the leather industry. The case studies cover the work carried out at pilot plant level with membrane bioreactors and reverse osmosis. Development in nanofiltration and a case study on the recovery of impurity-free sodium thiocyanate in the acrylic industry are described in Chapter 42. 

First, the treatment produced hazardous by-products from TNT. Second, the technology had high capital costs. Third, lagoon slurries had to be diluted prior to treatment. Fourth, gaseous effluents from the oxidation process, such as carbon monoxide (CO), C02, and NO, needed to be treated by another technology. Finally, the laboratory-scale system was found to have a 5 to 10% down time, because clays blocked the pump system and heat exchange lines, and solids built up in some of the... 

Inspection of the facilities for treatment of liquid effluents and gaseous emissions and disposal plants (with air pollution control) for solid wastes is carried out by State Pollution Control Authorities before granting consent to operate. 

The performance of SCWO for waste treatment has been demonstrated (15,16). In these studies, a broad number of refractory materials such as chlorinated solvents, polychlorinated biphenyls (PCBs), and pesticides were studied as a function of process parameters (17). The success of these early studies led to pilot studies which showed that chlorinated hydrocarbons, including 1,1,1-trichloroethane /7/-T5-6y,(9-chlorotoluene [95-49-8] and hexachlorocyclohexane, could be destroyed to greater than 99.99997, 99.998, and 99.9993%, respectively. In addition, no traces of organic material could be detected in the gaseous phase, which consisted of carbon dioxide and unreacted oxygen. The pilot unit had a capacity of 3 L/min of Hquid effluent and was operated for a maximum of 24 h. 

An evaluation of the CST (including its effluent gas treatment system) for treatment of wood dunnage and DPE suit material indicates successful treatment of both materials. Also, the test report noted that additional design and development for the solid materials handling and gaseous effluent systems were under way as this report was being prepared. 

The need to remove suspended dust and mist from a gas arises not only in the treatment of effluent gas from a plant before it is discharged into the atmosphere, but also in processes where solids or liquids are carried over in the vapour or gas stream. For example, in an evaporator it is frequently necessary to eliminate droplets which become entrained in the vapour, and in a plant involving a fluidised solid the removal of fine particles is necessary, first to prevent loss of material, and secondly to prevent contamination of the gaseous product. Further, in all pneumatic conveying plants, some form of separator must be provided at the downstream end. 

The usual gaseous effluent of SCWO treatment of waste containing carbon, hydrogen, oxygen, and nitrogen consists of the oxidation products... 

Liquid acidic wastes from the process were neutralised to form solid gypsum that was then sold to the building, paper and farming industries. The gaseous effluent, carbon dioxide, was sold to the beer and beverage industries. Finally, the iron salts were isolated and sold to the water treatment industry. In 1994 some 580000 tonnes of these products were sold to these industries. 

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