Fuel cold flow properties

However, one of the limitations of using biodiesel fuel for diesel engines is higher cold flow properties compared with petroleum diesel fuel (4). Cold properties consist of cloud point, pour point, and cold filter plugging point. The cloud point is a temperature at which the fuel starts to thicken and cloud, the pour point is a temperature at which the fuel thickens and no longer pours, and the cold filter plugging point is the lowest temperature at which fuel still flows through a specific filter. These... 

Despite its many advantages as a renewable alternative fuel, biodiesel presents a number of problems that must be resolved for it to be attractive for more widespread applications. These problems include improving relatively poor cold flow properties, monitoring and maintaining fuel quality... 

Waynick, J. A. 1997. Evaluation of the Stability, Lubricity, and Cold Flow Properties of Biodiesel Fuel. In Proc., 6th International Conference on Stability and Handling of Liquid Fuels. Atlanta GA IASH. 

Low temperature operability additives lower a diesel fuel s pour point and improve its cold flow properties. Most of these additives are polymers that interact with the wax crystals that form in diesel fuel when it is cooled below the pour point. The added polymers mitigate the adverse effect of wax crystal formation on fuel flow by modifying their size, shape, and degree of agglomeration. The polymer-wax interactions are fairly specific. As such, a particular additive generally will not perform equally well in all fuels. Unfortunately, the best additive for a particular fuel cannot be predicted it must be determined experimentally. 

Dr Adam Harvey at Newcastle University (Harvey, 2006) is examining the use of oscillatory baffle reactors as components to intensify the production of biodiesel fuels. The research at Newcastle University uses rapeseed oil as the feedstock, the atfiaction being generally that it is a renewable energy source, it reduces CO2 emissions and pollution and it attracts tax relief in the UK at present. The range of PI projects in this area include a portable plant, solid catalysts (which allow a reduced number of process steps compared to liquid catalysts), the development of a reactive extraction process direct from the oilseeds, examination of cold flow properties and the production of biodiesel from algae. 

Esters of levulinic acid produced from either methanol or ethanol are under active development as blend components in diesel formulations. These esters are similar to the biodiesel fatty acid methyl esters (FAME) now used in European low emission diesel formulations. FAME has certain disadvantages as automotive fuel components in diesel due to cold flow properties (24) and gum... 

Fatty acid stmcture (composition and imsaturation degree) of vegetable oils used as feedstocks considerably affect the physical properties of biodiesel such as viscosity, cold flow properties, oxidation stability and exhaust emission profile (Knothe 2008). Even, there are many successful attempts to predict the biodiesel properties from the fatty acid composition of the plant oils. Fatty acid distribution of some common vegetable oils is given in Table 2. Higher saturated fatty acid based biodiesel has higher viscosity, cold flow temperatures, oxidation stability and calorific value while higher imsaturated fatty acid based biodiesel shows a combination of improved fuel properties as a whole (Knothe 2005 Ramos 2009 Kumar 2013). 

Palm oil methyl ester presents an onset of crystallization above 0 °C (i.e. 6 °C) and a steep crystallization slope (Fig. 13.3a). Thus, its cold flow properties will be poorer than those of the rapeseed methyl ester. The crystallized fractions (CFs) determined at -15 °C for MEl, ME2 and DF are 2.3,1.5 and 25.9%, respectively. These percentages were calculated using the enthalpy of crystallization of DF (210 J/g) obtained elsewhere [9]. The same linear relation obtained for diesel fuels has been used for biodiesel and biodiesel blends ... 

The cold flow properties of diesel fuel and biodiesel blends are given in Table 13.4. As can be seen from these results, there is almost no influence when ME2 is blended with DF. This situation changes when MEl is blended with DF, where the quantity of precipitated crystals and the cold flow parameters are higher than those of neat DF and increase when MEl is increased from 10 to 30%. As was expected after the analyses of the pure compounds, blends of MEl with DF have lower cold flow parameters compared with blends of ME2 with DF. 

Although biodiesel is an excellent source of fuel, it has some disadvantages which include relatively poor cold flow properties and dilficulty in maintaining fuel quality during long-term storage. The latter is a matter of oxidation stability and will be discussed in this part. 

The different chemical compounds used as wax crystal modifiers do not all provide ideal performance under every circumstance. Various tests have been designed to help differentiate the performance of one wax crystal modifier over another. For example, a modifier may be quite effective at controlling wax crystal formation to enable a fuel to flow by gravity from a storage tank to a pump. However, once past the pump, the modifier may not effectively reduce the wax crystal size and shape to allow cold fuel to flow effectively through a line filter. The result is wax accumulation on the filter media, plugging of the fuel filter, and halting of fuel flow. A different wax crystal modifier or a product with wax dispersant properties may be required to permit effective fuel filtration. 

However, a method to improve the flow properties of such fuel oils of animal or vegetable origin, has been developed (26). This consists in adding a EVA copolymer or a comb polymer based on methyl acrylate and a-olefins. In addition, terpolymers of ethylene, vinyl acetate and isobutylene have been found to be useful as cold flow improvers (29). 

Gonz lez G6mez, M. E., Howard-Hildige, R., Leahy, J. J., and Rice, B. 2002. Winterization of Waste Cooking Oil Methyl Ester to Improve Cold Flow Temperature Fuel Properties. Fuel, 81,33-39. 

The low-density products manufactured in the SMDS process are predominantly paraffinic and free from impurities such as nitrogen and sulphur. Both the kerosine and gas oil have excellent combustion properties (smoke point and cetane number), and their cold-flow characteristics meet all relevant specifications - even the stringent freezing point requirements of aviation turbine kerosine. They also make excellent blending components for upgrading low-quality stock that would otherwise have to be used in fuel oil. The excellent quality of the products was proved in extensive engine tests. 

Cracking all or part of the straight-chain paraffins improves cold-flow characteristics of the hydrocarbon cut processed, but on the other hand, it has the disadvantage of reducing its yield and of slightly deteriorating some important properties of the cut—the jet fuel smoke point, gas oil cetane number, and lube oil viscosity index. The dewaxing operation should therefore offer the best possible compromise between the desired cold-flow characteristics. the yield requirements, and the combustion or viscosity characteristics. 

Abstract Thermal analytical methods such as differential scanning calorimetry (DSC) have been successfully applied to neat petrodiesel and engine oils in the last 25 years. This chapter shows how DSC and P-DSC (pressurized DSC) techniques can be used to compare, characterize, and predict some properties of alternative non-petroleum fuels, such as cold flow behavior and oxidative stability. These two properties are extremely important with respect to the operability, transport, and long-term storage of biodiesel fuel. It is shown that the quantity of unsaturated fatty acids in the fuel composition has an important impact on both properties. In addition, it is shown that the impact of fuel additives on the oxidative stability or the cold flow behavior of biodiesel can be studied by means of DSC and P-DSC techniques. Thermomicroscopy can also be used to study the cold flow behavior of biodiesel, giving information on the size and the morphology of crystals formed at low temperature. 

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