Heavy Sludge Deposits

Some atmospheric storage tanks and process vessels in heavy hydrocarbon service (e.g., crude storage tanks, coker fractionators, crude and vacuum towers) may contain heavy sludge and coke-like deposits. Demister pads and coalescers may also contain similar deposits. These heavy materials can be difficult to remove. 

The following options for removing these materials should be considered  

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Hot water or boiler feedwater is sometimes more effective than steam at removing heavy sludge deposits. The hot water tends to wash out waxy solids. If used for cleaning a distillation column or tower, the water can be circulated through the reflux piping. 

When cleaning equipment that contains heavy hydrocarbon deposits and sludges, contingency plans must be developed to safely cope with the potential release of additional hydrocarbons or toxics into the atmosphere of the confined space when the sludge is disturbed. 

The term varnish is used to describe the hard, amber-colored coating of fuel oxidation products adhering to engine components. The term sludge is used to describe the heavy, dark-colored deposits which settle from solution out of the fuel. Sludge can accumulate in areas of low turbulence and act as a prime site for initiating corrosion. 

Metal contamination of soils is primarily due to the application of sewage sludge, manure, phosphate fertilizers, atmospheric deposition, and traffic emissions. The most common heavy metal ions found in soils are Zn, Cu, Ni, Pb, Cr, and Cd. As mentioned earlier (see Section 6.3.1.4), sequential extraction techniques can differentiate among the metal forms in a soil, typically the acid soluble fraction (e.g., carbonates), the reducible fraction (e.g., iron/manganese oxides), and the ox-idizable fraction (i.e., metals in low oxidation states). 

Tropospheric Ozone The Environmental Chemistry of Organotin Compounds Determination of Heavy Metals in Sewage Sludge Inorganic Deposits in Invertebrate Tissues. 

Heavy vapours can spread for long distances in ditches, pipe tracks and drainage pipes and can accumulate in bunded areas, particularly if the bund walls are high. The manual clearing of sludges and deposits in the bottoms of storage tanks which have contained low-flash point solvents is particularly hazardous if low-level ventilation is not provided. 

The environmental concern about this element has arisen quite recently, since over half the cadmium ever produced has been refined in the last few decades (Nriagu, 1979). The main sources of Cd contamination in soils are metalliferous mining and smelting, heavy applications of sewage sludge, P-fertilizer and input from atmospheric deposition. 

The water from the flue gas wash flows through a wastewater treatment plant in which heavy metals and dioxins are precipitated and filtered out. In this process, about 1001 of sludge arise per year. The sludge is then drained in a filter press. One percent of the remaining sludge still contains heavy metals and must be disposed of in an underground deposit. 

Heavy Metals - Metallic elements that are located in the transitional series of the periodic chart of elements, These metals are not required in plant nutrition and usually are found in relatively small amounts in nature. Toxicity to plants could result with high concentrations of some heavy metals in soil, and problems in animal and human health may result if heavy metal concentrations in the diet are above certain critical levels. Examples are cadmium (Cd), chromium (Cr),-lead-(Pb),-nickel (Ni), and vanadium (V). Levels of heavy metals may be a problem in some phosphate rock deposits, sewage sludge, animal manures, and some industrial byproducts used as a source of fertilizer. 

Sludge removal Sludge should not be allowed to accumulate in the fuel storage basin but should be removed periodically by vacuuming or other methods. This material can contain chlorides, heavy metals, etc., and deposit on fuel assemblies, initiating pitting of the aluminium cladding. 

Heavy-duty (HD) additives keep solid combustion and oxidation products in suspension, thus avoiding deposits on metal surfaces, sludge formation and corrosive wear by neutralizing acidic decomposition products. Detergents, some of them RR-based, have sulfonate, hydroxy and/or carboxyl groups and usually contain metal ions or amine functions. More modem HD additives are based on methacrylates of fatty alcohols (Cn-ig), copolymerized with diethylaminoethyl methacrylate (9 1), vinylpyrollidone, N-vinylpyridine and hy-droxyethyl methacrylate. These ash-free dispersants may act also as VI improvers. Extreme-pressure (EP) additives ... 

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