Waste water evaporator units

The materials listed in Table 21 were investigated by simulating laboratory tests under operating conditions and exposure tests in waste water evaporator units of flue gas desulphurisation plants and waste incineration plants [64]. It was confirmed that only an approximate resistance can be estimated for the metallic materials in these plant sections. Precise material resistance data can only be determined for actual plants. The mass losses determined for alloy C-276 and alloy 59 after an exposure time of 9 months was only 0.053 mm/a (2.09 mpy) and 0.045 mm/a (1.77 mpy), respectively, with respect to the term of exposure. Therefore, they do not have technical significance. This results in the following proposal for materials for pipelines and tanks of waste water evaporator units of flue gas desulphurisation plants... 

NiCrMo alloys with high molybdenum contents can be used in waste water evaporator units of FGD plants. Their resistance decreases in the following order 59 (NiCr23Mol6Al, 2.4605), alloy C-22 (NiCr21Mol4W, 2.4602), and alloy C-276 (NiMol6Crl5W, 2.4819). 

Actions shifting hazardous waste from one environmental medium to another. Many of the waste management, treatment and control practices used to date have simply collected pollutants and moved them from one environmental medium to another, as follows (a) collection of pollutants from air and water via pollution control devices, which are then legally disposed of in land disposal sites, and (b) transfer of volatile pollutants from surface impoundments, landfills, water treatment units, groundwater air stripping operations, to the air through evaporation. 

The question of purity of the circulating water is not at all critical. For example, the boron tolerance for a loss in k of 0.0001 is roughly 10 parts per million. This is easily attained by distillation, and if it were not for the possibility of oil contamination, power boiler condensate would be entirely satisfactory. However, it probably will prove desirable to have a water evaporation imit available for concentrating radioactive wastes anyhow, and this same unit may well be used for producing distilled water for the pile circulating system. 

Alloy 400 (NiCu30Fe, 2.4360) was used in three stages of the evaporator/crystallisa-tion unit for waste water from the absorption fluid of a flue gas desulphurisation plant at 364 K (91 °C) and a pH value of 8-10. A corrosion rate of 0.04 mm/a (1.57 mpy) was measured after an operating time of 4 years. The alloy was used because the previously fitted rubber-coated steel components required frequent repairs [74]. 

The ratio Si02/Al203 affects the mother liquid. High aluminium content is forbidden due to strong environmental restrictions (less than 1 ppm in EC waste waters). High silicate (to suppress Al) content is undesirable due to silicalization of energy units (evaporator). 

In steam jet refrigeration, water is the refrigerant being evaporated at low pressures created by the steam jets. These units have a barometric direct contact condenser. Figure 1T1, or a surface condenser as in Figure 11-2. The former system wastes or loses the steam in the water whereas the latter allows the steam to be condensed and reused. 

If an evaporator, fed with steam at 399 K with a total heat of 2714 kJ/kg, is evaporating water at 373 K, then each kilogram of water vapour produced will have a total heat content of 2675 kJ. If this heat is allowed to go to waste, by condensing it in a tubular condenser or by direct contact in a jet condenser for example, such a system makes very poor use of steam. The vapour produced is, however, suitable for passing to the calandria of a similar unit, provided the boiling temperature in the second unit is reduced so that an adequate temperature difference is maintained. This, as discussed in Section 14.2.4, can be effected by applying a vacuum to the second effect in order to reduce the boiling point of the liquor. This is the principle reached in the multiple effect systems which were introduced by Rillieux in about 1830. 

The COLEX units operated between 1955 and 1963. Approximately 24 million pounds of mercury were employed and, unfortunately, a good deal was lost through waste, accidental spills, and evaporation. In fact, about 2 million pounds have not been accounted for. The process discharged approximately a quarter million pounds into the surface waters in the vicinity of the plant, and much of this remains in the bottom sediments of the watershed. 

Hexanone, also known as methyl n-butyl ketone or MBK, is a clear, colorless liquid with a somewhat sharp odor. The liquid form can easily evaporate into the air as a vapor. It is a waste product of wood pulping, coal gasification, and oil shale operations. 2-Hexanone was formerly used in paint and paint thinner and in various chemical substances. However, since it was found to have harmful health effects, it is no longer made in the United States, and its uses have been restricted. There are no known major natural sources of 2-hexanone in the environment. When 2-hexanone is released to rivers or lakes, it dissolves very easily, and it may evaporate into the air in a few days. We do not know if 2-hexanone binds to soil. When 2-hexanone is released to the water, air, or soil, it is probably broken down into smaller products, possibly within a few days. 

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