Cetane number fuel density

Identify the base fuel cetane number and density on the approipriate axes and draw a line joining these two points. 

H. Yang, Z. Ring, Y. Briker, N. McLean, W. Friesen and C. Fairbridge, Neural Network prediction of cetane number and density of fuel from its chemical composition determined by FC and GC-MS, Fuel 81, 65-74 (2002). 

The products could be classified as a function of various criteria physical properties (in particular, volatility), the way they are created (primary distillation or conversion). Nevertheless, the classification most relevant to this discussion is linked to the end product use LPG, premium gasoline, kerosene and diesel oil, medium and heavy fuels, specialty products like solvents, lubricants, and asphalts. Indeed, the product specifications are generally related to the end use. Traditionally, they have to do with specific properties octane number for premium gasoline, cetane number for diesel oil as well as overall physical properties such as density, distillation curves and viscosity. 

It is impractical to determine the cetane number of residual fuels in the ASTM D-613 cetane engine. Because of this, the Calculated Carbon Aromaticity Index and the Calculated Ignition Index were respectively developed by Shell and BR These values can be determined from the following equations where d = Density in kg/m3 59°F (15°C) and v = Viscosity in cSt 122°F (50°C). 

Liquid products contain sulfur and nitrogen and must be hydroprocessed to improve quality. Separate hydroprocessing units for upgrading the naphtha, kerosene, and gas oil fractions can be used to optimize the overall process. Refined gas oil or diesel fuel is aromatic in character and contains more cycloparaffins than conventional crude oil. The resulting fuel is low in cetane number, high in density, and typically has very good low-temperature handling properties. 

Diesel index an approximation of the cetane number (q.v.) of diesel fuel (q.v.) calculated from the density. v.) and aniline point (< .v.). 

Rapeseed methyl ester (RME) is another alternative biofuel that can be used in diesel engines. RME has the advantages that it is renewable compared to diesel, non-toxic and less flammable compared with many other fuels, like ethanol. RME has the same cetane number, viscosity and density as diesel, contains no aromatic compounds and is biologically degradable with minor contamination in soil. RME can be produced from vegetable oils, but is mostly produced from rapeseed oil by pressing of the seeds or by extraction. Up to 3 tons of rapeseed can be produced from one hectare. The fatty acids in rapeseed oil are mostly oleic acid, linoleic acid and linolenic acid. The oil is pressed from the plant and after some purification allowed to react with methanol in the presence of potassium hydroxide as a catalyst, to produce a methyl ester, see Figure 6.6. 

The quality of the product is of primary importance in developing a recycling technology converting plastics into fuels by pyrolysis. Today the characterization of a liquid fuel from any sources is obviously based on the qualification methods and standards of fuels from mineral oil. The properties of the pyrolysis-derived fuels from plastics are expected to be similar to conventional fuels (energy content, viscosity, density, octane and cetane number, flash-point, etc.). However, in addition to the familiar ranking values it is necessary to know more about the chemical composition of the plastic pyrolysis oil, because of the peculiarities as follows ... 

Some fuel properties have long been known to be interrelated with chemical composition density and aromatic content, viscosity and distillation range, cetane number and aromatic content. Correlation studies applying various statistical computational methods revealed the contribution of chemical structural units of organic compounds to the various physical properties of hydrocarbon fluids, such as octane and cetane number, flash point, cloud point, etc. 

It can be seen that compared with petroleum diesel fuel, methyl esters (1) have higher density, (2) fall into the lower range of viscosity, (3) have the same or higher cetane numbers, and (4) have lower heating value. Canola methyl esters are in the middle range of properties among the three oils, with low viscosity, good cetane... 

Cetane index is an estimation of the cetane number, which measures the anti-knoclc properties of the fuel. This index is more used than the cetane number because it can be calculated by a four-variable equation (density, BP 10%, BP 50% and BP 90%) according to ASTM D4737 standard method, instead of the test engine needed to measure cetane number. In our case, the relatively low amount of product obtained in these initial experiments does not allow determination of the cetane number, so we have used the cetane index to evaluate and compare our products, an approximation perfectly valid at this initial stage of investigation. 

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. 

Study. This cycle was chosen to give a first indication of the long term stability of the catalyst. The aging cycle includes low temperature conditions as well as high temperature phases. The diesel fuel used contained 0.15 wt.-% sulfiir, the lubricating oil had 0.1 wt.-% phosphorous. The cetane number, density and all other specifications correspond to the German standard DIN 51601 for automotive diesel fuel [22]. 

One method of sulfur removal from refinery streams is by hydrodesulfurization (HDS) in the refineries. This step also directly impacts the characteristics of low sulfur diesel fuels, such as density, aromatics content, cetane number, and cloud point. The magnitude of these changes will depend upon the type and setup of refinery HDS units. However, in the end some refractory compounds in fuel, e.g., 4,6-diraethyl dibenzothiophene, are very resistant to desulfurization, owing to the inaccessibility of the organically bound sulfur atom. Lower pressure HDS units which can work satisfactorily at 350 rag/kg sulfur levels, may have difficulty achieving reduction to 50 or 10 rag/kg sulfur level. 

The high energy density, the liquid character and the structural analogy to hexadecane cetane, the high-quality standard of the ignition quality of a diesel fuel, i.e. cetane number = 100) make lipids likewise suitable as an alternative diesel fuel source." ... 

Since DME characteristics are similar to those of liquefied petrol gas (LPG), it can be used in typical LPG applications, e.g. power generation, propellants, domestic cooking fuels or automotive fuels. If DME is employed as admixture, LPG properties are not significantly affected up to a DME content of around 20%. Compared to LPG, the cetane number is much higher (55-60 in contrast to 5 and 10 for propane and butane) and DME is, in principle, a suitable fuel for diesel engines. However, DME can not be blended with fossil diesel and its energy density is much lower, so that engines have to be adapted. 

Beyond the chemical composition and the octane and cetane numbers of a given fuel, many other physico-chemical characteristics are measured distillation intervals for given fractions, density, volatility, viscosity, heat of vaporization, etc... Of special interest is the amount of energy released by the combustion of the fuel and due to the exothermiticity of the reaction. This quantity is often tabulated as the Net Heating Value or NHV, i.e. the heat of reaction of a liquid fuel and air giving gaseous combustion products (CO2 and H2O) at 25°C. 

Fig. 4.2 General relationship between cetane number (CN) and density of the fuel...

Cetane index, as defined by ASTM D976, is not a measurement, but the result of a calculation based on density and mid-boiling point. It is nearly the same the as cetane number for diesel fuels comprised mostly of straight-run gas oils blended with lesser amounts of cracked stocks. Diesel index is a ... 

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