Diesel Blending

Owing to its properties, methanol is not recommended for aircraft or marine fuel uses. Methanol caimot be used in conventional diesel-powered vehicles without modifications to the fuel system and engine. Simple methanol—diesel blends are not possible because of insolubiUty. Heavy-duty diesel engines have been adapted to use neat methanol by many U.S. manufacturers, and several are being used in field demonstrations (82) (see Alcohol fuels). 

Biodiesel is diesel fuel produced from vegetable oils and other renewable resources. Many different types of oils can he used, including animal fats, used cooking oils, and soybean oil. Biodiesel is miscible with petroleum diesels and can he used in biodiesel-diesel blends. Most often blends are 20 percent biodiesel and 80 percent traditional diesel. Soy diesel can be used neat (100%), hut many other types of biodiesel are too viscous, especially in winter, and must be used in blends to remain fluid. The properties of the fuel will vaiy depending on the raw material used. Typical values for biodiesel are shown in Table 1. 

Biodiesel does not present any special safety concerns. Pure biodiesel or biodiesel and petroleum diesel blends have a higher flash point than conventional diesel, making them safer to store and handle. Problems can occur with biodiesels in cold weather due to their high viscosity. Biodiesel has a higher degree of unsaturation in the fuel, which can make it vulnerable to oxidation during storage. 

Light cycle oil (LCO)—used as a pumparound stream, sometimes as absorption oil in the gas plant, and stripped as a product for diesel blending and... 

There has been a recent revival in interest in the use of ethanol-diesel fuel blends (E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions [27]. E-diesel blends containing 10-15% ethanol could be prepared via the use of additives. However, several fuel properties that are essential to the proper operation of a diesel engine are affected by the addition of ethanol to diesel fuel - in particular, blend stability, viscosity and lubricity, energy content and cetane number (increasing concentrations of ethanol in diesel lower the cetane number proportionately) [28]. Materials compatibility and corrosiveness are also important factors that need to be considered. 

The quality of the ethanol has a strong influence on its corrosive effects. Three categories of problems have been identified general corrosion (caused by ionic impurities, mainly chloride ions and acetic acid), dry corrosion due to ethanol polarity, and wet corrosion caused by azeotropic water. Corrosion inhibitors should thus be incorporated in ethanol-diesel blends. 

A critical safety issue of using diesel-ethanol blends relates to flashpoint and flammability. E-diesel blends containing 10-15% ethanol have the vapor pressure and flammability limits of ethanol. This means that ethanol concentrations in enclosed spaces such as fuel storage and vehicle fuel tanks are flammable over the temperature range 13-42 °C. Thus, there are higher risks of fire and explosion than with diesel fuel, or even gasoline. Other vehicle performance-related concerns are (a) a decreased maximum power (b) an increased incidence of fuel pump vapor lock and (c) a reduced fuel pump and fuel injector life due to the decreased lubricity of ethanol. 

An extensive review has been conducted to identify potential oxygenates for blending into diesel fuels [55]. Over 70 molecules were identified and tested, taking into account numerous physical properties such as oxygen content, flash point, viscosity, cetane number, corrosivity, toxicity, and miscibility with diesel blends. Five key aspects were considered critical to develop commercially valuable diesel additives ... 

L.R. Waterland, S. Venkatesh, S. Unnasch, Safety and Performance Assessment of Ethanol/ Diesel Blends (E- Diesel), NREL Report SR-540-34817 Sept,... 

A.C. Hansen, P.W.L. Lyne, Q. Zhang, Ethanol-diesel blends a step towards a bio-based fuel for diesel engines, 2001 ASAE Annual International Meeting, Sacramento, CA, July 2001, Paper 01-6048 (http //www.ag-bioeng.uiuc.edu/ faculty/ach/ediesel/Publications/ infopub.pdf). 

Among the classes of feedstock processed in the hydrocracker the most highly aromatics feed are light cycle oils produced in the FCC unit Once formed by cyclization and the hydrogen transfer mechanism discussed above, they accumulate in the product due to the absence of a metal function in the FCC catalyst and adequate hydrogen in the process environment. They are typically sold as low-value fuel oil, or hydrotreated to reduce sulfur content and improve their quality as diesel blend stocks. Another approach to upgrade their value even further... 

Moreover, European regulations in 2005 restricted the sulfur content in diesel fuel to SOmgkg. Sulfur organic compounds are known to provide diesel fuel with a lubricity that will disappear as the regulations take effect. Addition of biodiesel at a level of 1-2% to diesel blends has the effect of restoring lubricity through an antiwear action on engine injection systems, which is specific for polar molecules. 

Diesel-ethanol formulations are being marketed that contain other blended components to enhance fuel performance. These recently developed diesel blends contain ethanol at volumes ranging from 7.5% to as high as 30%. Additive concentrations in these blends average 5% or more. This fuel technology is in the early stages of field application. 

Clark, Nigel, Mridul Gautam, Donald Lyons, Chris Atchinson, Wenwei Xie, Paul Norton, Keith Vertin, Stephen Goguen, and James Eberhardt. 1999. On Road Use of Fischer-Tropsch Diesel Blends. Report No. 1999-01-2251. Warrendale, Pa. Society of Automotive Engineers. 

J.A. Kinast and K.S. Tyson, in Production of biodiesel from multiple feedstocks and properties of biodiesel and biodieselj diesel blends. Final report , NREL, Golden, CO, 2003, Volume, p. 57. 

Kalligeros, S., Zannikos, F., Stoumas, S., Lois, E., Anastopoulos, G., Teas, C., and Sakellaropoulos, F. 2003. Using Biodicscl/Marinc Diesel Blends on the Performance of a Stationary Diesel Engine. Biomass Bioenergy, 24,141-149. 

The column bottoms (referred to as slurry decant oil) pass to heavy oil processing units or are blended into heavy fuel oil. The heavy gas oil fraction (sometimes called heavy cycle oil) is recycled or used as blend-stock for heavy diesel or industrial fuel oil. The light gas oil (sometimes called light cycle oil) is used for diesel blend-stock. The most important product is the gasoline component which goes to gasoline blending. The... 

Vegetable oils have also been considered in applications as fuels and attempts to maintain solutions of triacylglycerol oils at low temperatures have also been attempted. Blends of vegetable oil and lower alcohols have suitable viscosity for use in fuels, but they separate into two phases as temperature is lowered (62). Higher molecular weight alcohols can be used to lower the temperature of phase separation. In a soy oil number 2 diesel blend with ethanol, phase separation was deferred to 16°C whereas the cold filter plugging point was lowered to 24°C. 

The test results show that n-paraffin (1) linearly raises the cetane of unadditized diesel without a top-end limit (2) can linearly raise the cetane of nonresponsive diesel blends (3) is synergistic with traditional cetane improvers (4) has a low sulfur content and (5) increases endproduct volume added (4, 5). When n-alkanes and cetane enhancers were added to a diesel fuel with a cetane number of 32 to raise the cetane number to 43, a 10% reduction in carbon dioxide emissions was achieved. 

With the above-mentioned uncertainties and limitations concerning the accuracy of commercial simulators, results obtained with Aspen, which can be used to at least directionally, illustrate the merits of using methane/diesel blends for a particular set of conditions with a diesel fuel at room temperature (70°F), are illustrated in Table 6. 

DME is superior to methanol as a fuel in terms of environmental friendliness and chemical toxicity (7d). It is considered to be an additive to diesel or LPG and not a replacement. Firing DME-diesel blends creates challenges for the engine manufacturer. The fuel must be injected at a high enough pressure to keep the dimethyl ether in liquid form. The specific wear characteristics of engines operating with this fuel remains to be studied (77). 

Engine test runs were carried out on diesel engine with various diesel/jatropha diesel blends and the following results were obtained. The extent to which carbon had been deposited on the injector jets, piston and valves was noted after the engine had been run for 100 hours. The results are shown in Figures 4, 5 and 6, below. It was concluded that there was no significant carbon deposits on the injectors, pistons and valves, which shows that there was complete combustion of the fuel. 

The basic precautions for handling alcohol fuels and alcohol-gasoline or alcohol-diesel blends are ... 

Chen G, Shen Y, Zhang Q, Yao M, Zheng Z, Liu H (2013) Experimental study on combustion and emission characteristics of a diesel engine fueled with 2,5-dimethylfuran-diesel, n-butanol-diesel and gasoline-diesel blends. Energy 54 333-342... 

Christensen E, Williams A, Paul S, Burton S, McCormick RL (2011) Proptaties and ptafor-mance of levulinate esters as diesel blend components. Energy Fuels 25 5422-5428... 

Mehta RN, Chakraborty M, Mahanta P, Paiikh PA. (2010). Evaluation of fuel properties of butanol-biodiesel-diesel blends and their impact on engine performance and emissions. Ind... 

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