Low-temperature flow

Some additives have the ability to lower the pour point without lowering the cloud point. A number of laboratory scale flow tests have been developed to provide a better prediction of cold temperature operability. They include the cold filter plugging point (CFPP), used primarily in Europe, and the low temperature flow test (LTFT), used primarily in the United States. Both tests measure flow through filter materials under controlled conditions of temperature, pressure, etc, and are better predictors of cold temperature performance than either cloud or pour point for addithed fuels. 

Polyalphaolefin hydraulic fluids have many advantages over the mineral oil counterparts including low temperature flow characteristics, lower volatility, and oxidative stability (Chrisope and Landry 1993 Shubkin 1993). Certain polyalphaolefins maintain good operational characteristics and have been proposed for use in hydraulic systems in U.S. military aircraft (Kinkead et al. 1992b). 

This wax can accumulate on fuel filter media and can lead to plugging of small orifices and lines. This plugging temperature can be measured and is commonly referred to as the filter plugging temperature. Testing methods utilized to predict the filter plugging temperature and the low-temperature flow properties of distillate fuel are listed in TABLE 4-5. 

As a general rule, low-molecular-weight aromatic compounds help to improve the low-temperature flow properties of fuels and oils. 

Another possible solution to the problem of high temperature stability is the use of additives. Not exactly a stranger to petroleum people (as evidenced by use in gasoline and lubricants) they generally fall into two classes metallic and non-metallic. The former, for the most part are metal salts of sulfonates or naphthenates, whereas the latter are either amines or amine derivatives (later other organics may prove more effective) Use of additives in jet fuels, however, must of necessity be approached with caution. As surface active materials, many have a variety of uses and properties. Hence, they must not introduce new problems such as foaming at high altitudes, emulsification, or interference with low temperature flow. These could easily be severe limitations, but additives are under serious consideration thruout the industry... 

This advantage is due to molecular structure and the lack of crystalline wax particles, present in some refined petroleum oils. Fully synthetic engine oil lubricants offer excellent low temperature flow and viscosity properties.(Demmin etal., 1992 Lakes, 1999). 

PM2 5 PM10 PMA PMC PNA Pour point Particulate matter less than 2.5 ptm and 10 jam in diameter. Polymetacrylate viscosity index improver or viscosity modifier. Pensky-Martin closed cup-flash point test. Polynuclear aromatic. Measure of lubricant low-temperature flow which is 3°C above the temperature at which a normally liquid petroleum product maintains fluidity. Oil forms a honeycomb or crystals at low... 

CP = cloud point PP = pour point CFPP = cold filter plugging point LIFT = low-temperature flow test. 

Auschra, C., Vetter, J., Bohmke, U., and Neusius, M. 1999. Methacrylate Copolymers as Low-Temperature Flow Improvers for Biodiesel Fuels and Biologically-Derived Fuel Oils. PCTInt. Patent Appl. WO 9927037 (Jun. 3). 

Dunn, R. O., Shockley, M. W., and Bagby, M. O. 1996. Improving the Low-Temperature Flow Properties of Alterative Diesel Fuels Vegetable Oil-Derived Methyl Esters. J. Am. Oil Chem. Soc., 73,1719-1728. 

Lubricants Mineral-based lubricants lead the lubricant market. However, with the advancement of the need for biodegradable products, vegetable oils have become popular, because of they are also better lubricants. The fatty acid composition of vegetable oils, however, is one major disadvantage. Oils rich in saturated fatty acids have poor low-temperature flow properties, and those rich in polyunsaturated fatty acids are of low oxidative resistance. Vegetable oils rich in monoun-samrated fatty acids have optimum oxidative stability and low-temperature properties (125). 

Fatty acid methyl esters and other esters of fatty acids and a lower alcohol can be added at a low ratio to most diesel fuels without substantially changing fuel characteristics. It has been reported that in blends containing 30 percent biodiesel, low-temperature flow properties are not greatly affected (12), but at higher blend levels, the properties of the methyl ester may affect the properties of the fuel. With few exceptions, pure biodiesel does not meet minimum low-temperature requirements and may exceed manufacturers maximum viscosity for diesel fuels. 

In temperate climates, diesel fuel must remain fluid at temperatures below the minimum expected temperature for the season. Through much of North America, winter diesel fuels have low temperature flow points below —30°C. Diesel fuels with low pour points have lower viscosity and often lack lubricity (110). These fuels typically provide little lubricity. For example, Noureddini (111) reports that biodiesel fuels that are simple esters of various vegetable oils have poor flow characteristics below a temperature of —2°C. To overcome this difficulty, a solvent consisting of mixed ethers of glycerol is added to the biodiesel. The resultant fluid has a low temperature cloud point below —32°F (—36°C). The pour point of this fluid is still above that necessary to effectively add to many winter diesels, as it may be necessary to pour the fuel component at temperatures as low as —45°C. 

Alternatively, low-temperature flow test (ASTM D-4539) results are indicative of the low-temperature flow performance of fuel in some diesel vehicles. This test method is especially useful for the evaluation of fuels containing flow improver additives. In this test method, the temperature of a series of test specimens of fuel is lowered at a prescribed cooling rate. At the commencing temperature and at each 1°C interval thereafter, a separate specimen from the series is Altered through a 17-mm screen until a minimum low-temperature flow test pass temperature is obtained. The minimum low-temperature flow test pass temperature is the lowest temperature, expressed as a multiple of 1°C, at which a test specimen can be Altered in 60 s or less. 

In the majority of cases, chemical additives are used to enhance the properties of base oils to improve such characteristics as oxidation resistance (ASTM D-2893, ASTM D-4742,ASTM D-5846) change in viscosity (ASTM D-445, IP 71) with temperature, low-temperature flow properties as derived from the pour point (ASTM D-97, ASTM D-5853, ASTM D-5949, ASTM D-5950, ASTM D-5985, IP 15) and fluidity measurements (ASTM D-6351), emulsifying ability (ASTM D-2711), extreme pressure (ASTM D-2782, ASTM D-2783, ASTM D-3233, IP 240), antiwear and frictional properties (ASTM D-5183, ASTM D-6425), and corrosion resistance (ASTM D-4636). The selection of components for lubricating oil formulation requires knowledge of the most suitable crude sources for the base oils, the type of refining required, the types of additive necessary, and the possible effects of the interactions of these components on the properties of the finished lubricating oil. 

Stambaugh, R.L. and O Mara, J.H. (1982) Low temperature flow properties of engine oils. SAE Trans. 91 Paper 820509. 

F ow P/LOpcAtlei Under this heading come the viscosity of the fluid and the effect of temperature on viscosity. The latter might be a theoretically derived function, or an arbitrary function such as the viscosity index, or even a grossly empirical evaluation of the viscosity at two or more selected temperatures. Low temperature flow properties are frequently evaluated by the ASTM pour point determination [5], but the inadequacies of this method of evaluation have led to the use of pumpability tests which have a better empirical relation to service conditions. 

Uses. A marked improvement in the low temperature flow property of a fuel oil having a bp 120-150°C by adding a novel compound prepared by reacting pri-, sec- or tert-aliphatic amine containing alkyl group of 1-30 C-atoms with 9,10-dihydroanthracene-9,10-endo-aP-succinic anhydride (or acid) there of together with a polymer having ethylene structure present relates compound temperature fluidity middle distillate composition petroleum fuel. 

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