Off-gas emissions

When it is determined that an air-stripper gas effluent will require treatment, a conventional method for the reduction of air emissions is the use of GAC (granular activated carhon). GAC will usually provide suitable adsorption of airborne VOCs (16). 

Even where off-gas treatment adds significant costs to the treatment process, air stripping may still be clearly indicated as a primary treatment technology. GAC and other treatment methods are not capable of sufficient removal of some species of volatile organic compounds, and are often used in conjunction with gas stripping. 

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Off-gas emissions from the modified baseline process MPF will pass through a separately fired afterburner maintained at a temperature of 2,000°F. The committee was told that the afterburner design is patterned after the successful afterburner operations at JACADS and TOCDF (Webster, 2000). The key design parameter for the afterburner is to have a one-second residence time at 2,000°F (CR E, 2000). Off-gas emissions then pass through the PAS, which includes high-efficiency particulate air (HEPA) and carbon filtration. Metal parts emerging from the MPF will be disposed of as scrap metal. 

How can the off-gas emission from a culture in a bioreactor provide any useful information about culture state Under favorable conditions, an experienced practitioner can identify the type and stage as well as detect contamination with... 

Because of a number of negative points, e.g. NH,j not eliminated, costly incineration of residual air, new standards on off-gas emissions and risks of explosion, this technique which used to be very widespread in Europe is now being phased out. 

The hydrosulfide oxidation reaction produces water, which accumulates in the Stretford liquor. Other major sources of water ate the sulfur wash water and the dilution water associated with the fresh chemicals makeup solution. Water vapor in the oxidizer vent gas and other evaporation losses are normally insufficient to water balance the luocess, and a small evaporator is commonly used to remove additional water from the system. This evaporator takes a side sueam from the circulating liquor loop and evaporates any excess water with air. The evapma-tor is rather small and evaporator off-gas emission contributions are usually negligible. 

A bleed from the scmbbing system is sent to a sour slurry stripper. The water is then clarified and can be recycled to minimize the volume of effluent to be biotreated and discharged or evaporated. The acid gas from the acid gas removal system and from the sour slurry stripper is fed to a Claus plant, where salable elemental sulfur (qv) is produced. For maximum sulfur recovery and minimal sulfur emissions, the Shell Claus off-gas treating process (SCOT) is used. 

Phthalic anhydride (most emissions from off-gas from switch condensers)... 

We shall now provide a second example to illustrate step-by-step calculations. In this example a flare stack is estimated to be 80% efficient in combusting HjS off-gas. The total off-gas through the stack is 400,000 kg/hr, of which 7.0 weight percent is H2S. The physieal stack height is 250 m, the stack diameter is 5.5 m, and the stack emission velocity is 18 m/s. The stack emission temperature is 15°C. The meteorological conditions may be described as a bright sunny day with a mean wind speed of 3 m/s. 

Step 1 Determine primary emission heat content. This step should be taken early in the design stage to determine if the enclosure will capture both primary and secondary emissions. The heat content of furnace emissions and the temperature limitation on the fume collector are considered for this task. The off-gas heat content is calculated for furnace reactions during melting and refining periods. The maximum heat content should be used for design. Assuming a fabric... 

Protocol. In 1997, prior to President Clinton s acceptance of the Kyoto Protocol, U.S. Senate Resolution 98, the Byrd-Hcgcl resolution, which was passed by a vote of ninety-five to zero, imposes specific requirements that must be met before the Kyoto Protocol can be ratified. The resolution calls for a specific timeline and commitments by developing countries to reduce greenhouse gas emissions, and evidence that adoption of the Kyoto Protocol would not result in serious harm to the U.S. economy. In addition, the Fifth Conference of the Parties (1999) failed to resolve numerous outstanding issues held over from the previous conference, and put off critical decision making until the Sixth Conference of the Parties in The Ffague, Netherlands, in November 2000. 

The byproduct is a stoichiometric amount of 60 wt % H2S04, which is used in the chemical industry. The wastewater (0.3 m3/100 kg active matter), which contains paraffin, oxidation products of the paraffin, alkanesulfonate, and sulfur dioxide, has a chemical oxygen demand (COD) of 1800 mg/L and is readily biodegradable (>95% after 7 days). The sulfur dioxide emission after repeated washing of the off-gas amounts to 0.5 g/100 kg active matter [6]. 

Sulfur dioxide is generated in large quantities during the primary zinc refining process and sulfur fixation is carried out concurrently with the primary production process in order to meet CAA emission standards. Concentrations of sulfur dioxide in the off-gas vary with the type of roaster operation. Typical concentrations for multiple-hearth, suspension, and fluidized-bed roasters are 4.5 to 6.5%, 10 to 13%, and 7 to 12%, respectively. This sulfur dioxide is then converted into sulfuric acid. 

It was found that the concentration of total oxidants measured in the off-gas from the hypo unit varied with process conditions. Precise analysis of the off-gas showed that under certain conditions chlorine dioxide is formed in the reaction step where the hypochlorite concentration is approximately 160-180 g l-1. In the sections below formation of chlorine dioxide in the hypochlorite unit is discussed with regard to process conditions and peak load of the feed stream. In essence, the emission of chlorine dioxide can be reduced to nearly zero by using a scrubber in which the chlorine dioxide reacts with hydrogen peroxide. 

Sulfur is removed from a number of refinery process off-gas streams (sour gas) to meet the sulfur oxide emissions limits of the Clean Air Act and to recover salable elemental sulfur. Process off-gas streams, or sour gas, from the coker, catalytic cracking unit, hydrotreating units, and hydroprocessing units can contain high concentrations of hydrogen sulfide mixed with light refinery fuel gases. 

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