Sediment, and Water

Considerable importance is attached to the presence of water or sediment in petroleum because they lead to difficulties in the refinery, for example, corrosion of equipment, uneven running on the distillation unit, blockages in heat exchangers, and adverse effects on product quality. 

The sediment consists of finely divided solids that may be drilling mud or sand or scale picked up during the transport of the oil or may consist of chlorides derived from evaporation of brine droplets in the oil. The solids may be dispersed in the oil or carried in water droplets. Sediment in petroleum can lead to serious plugging of equipment, corrosion due to chloride decomposition, and a lowering of residual fuel quality. 

Water may be found in the crude either in an emulsified form or in large droplets and can cause flooding of distillation units and excessive accumulation of sludge in tanks. Refiners generally limit the quantity, and although steps are normally taken at the oil field to reduce the water content as much 

Before the assay it is sometimes necessary to separate the water from a petroleum sample. Certain types of petroleum, notably heavy oil, often form persistent emulsions that are difficult to separate. On the other hand, in testing wax-bearing petroleum for sediment and water care must be taken to ensure that wax suspended in the sample is brought into solution before the test otherwise it 1 be recorded as sediment. 

The Karl Fischer test method (ASTM D-1364, ASTM D-6304) covers the direct determination of water in petroleum. In the test, the sample injection in the titration vessel can be performed on a volumetric or gravimetric basis. Viscous samples can be analyzed with a water vaporizer accessory that heats the sample in the evaporation chamber, and the vaporized water is carried into the Karl Fischer titration cell by a dry, inert carrier gas. 

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The high C/H ratio for heavy fuels and their high levels of contaminants such as sulfur, water, and sediment, tend to reduce their NHV which can reach as low as 40,000 kJ/kg by comparison to the 42,500 kJ/kg for a conventional home-heating oil. This characteristic is not found in the specifications, but it is a main factor in price negotiations for fuels in terms of cost per ton. Therefore it is subject to frequent verification. 

The water and sediment contents of crude oils is measured according to the standard methods NF M 07-020, ASTM D 96 and D 1796, which determine the volume of water and sediments separated from the crude by centrifuging in the presence of a solvent (toluene) and of a demulsifylng agent Table 8.13 gives the bottom sediment and water content of a few crude oils. 

Crude oil name Water and sediment contents (BS W) In volume %... 

Water and sediments NF M 07-020 ISO 3734 ASTM D 1796 Mix with toluene and centrifugation... 

Conclusions. The impact of plasticizers on the environment is very low and is diminishing as evidenced by analytical data showiag that the levels of phthalates ia surface waters and sediments are decreasiag. This is despite the fact that their usage has continued to iacrease aimuaHy and is most likely due to improved emission controls and wastewater treatment. 

The amount of water hy distihatiou hy Test Method D 95 plus the sediment hy extraction hy Test Method D 473 shall not exceed the value shown in the table. For Grade No. 6 fuel oil, the amount of sediment hy extraction shall not exceed 0.5 mass % and a deduction in quantity shall he made for all water and sediment in excess of 1.0 mass %. 

Heat of combustion can be estimated within 1 percent from the relative density of the fuel by using Fig. 27-3. Corrections for water and sediment must be apphed for residual fuels, but they are insignificant for clean distillates. 

The failure took place in a large water-tube boiler used for generating steam in a chemical plant. The layout of the boiler is shown in Fig. 13.1. At the bottom of the boiler is a cylindrical pressure vessel - the mud drum - which contains water and sediments. At the top of the boiler is the steam drum, which contains water and steam. The two drums are connected by 200 tubes through which the water circulates. The tubes are heated from the outside by the flue gases from a coal-fired furnace. The water in the "hot" tubes moves upwards from the mud drum to the steam drum, and the water in the "cool" tubes moves downwards from the steam drum to the mud drum. A convection circuit is therefore set up where water circulates around the boiler and picks up heat in the process. The water tubes are 10 m long, have an outside diameter of 100 mm and are 5 mm thick in the wall. They are made from a steel of composition Fe-0.18% C, 0.45% Mn, 0.20% Si. The boiler operates with a working pressure of 50 bar and a water temperature of 264°C. 

Cleanliness is a measure of the water and sediment and the partieulate eontent. Water and sediment are found primarily in liquid fuels, while partieulates are found in gaseous fuels. Partieulates and sediments eause elogging of fuel filters. Water leads to oxidation in the fuel system and poor eombustion. A fuel ean be eleaned by filtration. 

Table 12-4 is a summary of liquid fuel speeifieations set by manufaeturers for effieient maehine operations. The water and sediment limit is set at 1% by maximum volume to prevent fouling of the fuel system and obstruetion of the fuel filters. Viseosity is limited to 20 eentistokes at the fuel nozzles to prevent elogging of the fuel lines. Also, it is advisable that the pour point be 20 °F (11 °C) below the minimum ambient temperature. Failure to meet this speeifieation ean be eorreeted by heating the fuel lines. Carbon residue should be less than 1% by weight based on 100% of the sample. The hydrogen eontent is related to the smoking tendeney of a fuel. Lower... 

The pour point is an indication of the lowest temperature at which a fuel oil can be stored and still be capable of flowing under gravitational forces. Fuels with higher pour points are permissible where the piping has been heated. Water and sediment in the fuel lead to fouling of the fuel system and obstruction in fuel filters. 

Fuel system fouling is related to the amount of water and sediment in the fuel. A by-product of fuel washing is the desludging of the fuel. Washing rids the fuel of those undesirable constituents that cause clogging, deposition, and corrosion in the fuel system. The last part of treatment is filtration just prior to entering the turbine. Washed fuel should have less than. 025% bottom sediment and water. 

Sample and Analyze Surface Waters and Sediments or Point Source Discharges... 

Winogradsky column Glass column with an anaerobic lower zone and an aerobic upper zone, which allows growth of microorganisms under conditions simitar to those found in nutrient-rich water and sediment. 

Environmental chemists funded by the Department of Energy have studied these sources to learn as much as they can about the chemistry of plutonium dispersed in freshwater and marine ecosystems. Much of the early work determined the concentrations in various water bodies and the distribution between water and sediment. Table I shows results of various freshwater and marine surveys(10). 

Lerman, A. (1979). "Geochemical Processes Water and Sediment Environments." Wiley, New York. 

Watersheds, also known as drainage basins, define a natural context for the study of relationships among soils, geology, terrestrial ecosystems, and the hydrologic system because water and sediment travel downslope under the influence of gravity. This material is a continuation of some of what was presented in Chapter 6. 

The highest levels of monobutyltin and dibutyltin in water and sediment are thought to relate mainly to degradation of tributyltin from its use on boats as an antifouling paint. 

Methyl parathion has been released to the environment mainly as a result of its use as an insecticide on crops. It is applied to agricultural crops by aerial or ground spraying equipment. Methyl parathion has been detected in surface waters and sediments, rainwater, aquatic organisms, and food. There are no known natural sources of the compound. Methyl parathion has been identified in at least 16 of the 1,585 hazardous waste sites on the NPL (HazDat 2001). 

Pritchard PH, Gripe CR, Walker WW, et al. 1987. Biotic and abiotic dehydration rates of methyl parathion in freshwater and estuarine water and sediment samples. Chemosphere 16 1509-1520. 

A procedure has been developed for the analysis of a- and (3-endosulfan and endosulfan sulfate in fish, water, and sediments (Chau and Terry 1972 Musial et al. 1976). This procedure involves the acetylation of endosulfan residues into their diacetates and subsequent quantification by GC/ECD. Detection limits of low-ppb levels of endosulfan were reported. This approach is rapid and simple, and minimum sample preparation is required (Chau and Terry 1972 Musial et al. 1976). 

Walker WW, Cripe CR, Pritchard PH, et al. 1988. Biological and abiotic degradation of xenobiotic compounds in in vitro estuarine water and sediment/water systems. Chemosphere 17 2255-2270. 

Particularly polar contaminants may associate with polymeric humic components of soil, water, and sediment. Their biodegradation then depends on the degree to which these processes are reversible and the contaminants become accessible to microorganisms (bioavailable). This is especially significant after weathering (aging), even for nonpolar compounds. 

Munthe J, Hultberg H, Lee Y-H, Parkman H, I verfeldt A, Renberg I. 1995a. Trends of mercury and methylmercury in deposition, run-off water and sediments in relation to experimental manipulations and acidification. Water Air Soil PoUut 85(2) 743-748. 

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