Stack gases moisture content

Small amounts of sulfuric acid mist or aerosol are always formed in sulfuric acid plants whenever gas streams are cooled, or SO and H2O react, below the sulfuric acid dew point. The dew point varies with gas composition and pressure but typically is 80—170°C. Higher and lower dew point temperatures are possible depending on the SO concentration and moisture content of the gas. Such mists are objectionable because of both corrosion in the process and stack emissions. 

Moisture Content EPA Method 4 is the reference method for determining the moisture content of the stack gas. A value for moisture content is needed in some of the calculations for determining pollution-emission rates. 

A samphng probe is placed at any location in the stack, and a grab sample is collected in an evacuated flask. This flask contains a solution of siilfiiric acid and hydrogen peroxide, which reacts with the NO. The volume and moisture content of the exhaust-gas stream must be determined for calculation of the total mass-emission rate. The sample is sent to a laboratoiy, where the concentration of nitrogen oxides, except nitrons oxide, is determined colorimetrically. 

FIGURE 6.1 Boiler efficiency and losses due to bagasse moisture content. (Stack gas temperature = 450 K.)... 

Gas analysis for the determination of emission rate correction factor or excess air Determination of carbon dioxide, methane, nitrogen, and oxygen from stationary sources Determination of moisture content in stack gases Determination of particulate matter emissions from stationary sources... 

Fission product noble gases entering the water-steam circuit in the event of a tube leak are completely volatilized and transported with the steam to the main condenser where they are extracted and released via the off-gas stack. This release is monitored by a continuously operating detector device located in the condenser off-gas line. Non-volatile fission and activation products which are transported over the leak to the water-steam circuit remain completely in the water phase of the steam generator by the action of the blowdown purification system their activity concentration is kept at a level which is controlled by the injection rate on the one hand and by the purification rate on the other. Because of the very low vapor pressures of these elements and their chemical compounds (dissolved ions or insoluble oxides/hydroxides), their transport to the steam under the prevailing conditions (270 °C, 7 MPa) is only possible by droplet entrainment. This means that partitioning between liquid and steam phases is proportional to the steam moisture content, which is usually well below 0.1%. 

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