Fuels carbon residue

Carbon residue, pour point, and viseosity are important properties in relation to deposition and fouling. Carbon residue is found by burning a fuel sample and weighing the amount of earbon left. The earbon residue property shows the tendeney of a fuel to deposit earbon on the fuel nozzles and eombustion liner. Pour point is the lowest temperature at whieh a fuel ean be poured by gravitational aetion. Viseosity is related to the pressure loss in pipe flow. Both pour point and viseosity measure the tendeney of a fuel to foul the fuel system. Sometimes, heating of the fuel system and piping is neeessary to assure a proper flow. 

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 carbon residue is a measure of the carbon compounds left in a fuel after the volatile components have vaporized. Two different carbon residue tests are used, one for light distillates, and one for heavier fuels. For the light fuels, 90% of the fuel is vaporized, and the carbon residue is found in the remaining 10%. For heavier fuels, since the carbon residue is large, 100% of the sample can be used. These tests give a rough approximation of the tendency to form carbon deposits in the combustion system. The metallic compounds present in the ash are related to the corrosion properties of the fuel. 

Carbon residue is expressed as a percentage by weight of the original sample of the fuel, with the amount determined by burning a given quantity in a scaled container until all that remains is carbon residue. The amount of carbon residue left within the combustion chamber of the engine has a direct bearing upon the internal deposits and affects the cleanliness of combustion, particularly the smoke emissions at the exhaust stack. 

Other properties of interest are carbon residue, sediment, and acidity or neutralization number. These measure respectively the tendency of a fuel to foul combustors with soot deposits, to foul filters with dirt and rust, and to corrode metal equipment. Cetane number measures the ability of a fuel to ignite spontaneously under high temperature and pressure, and it only applies to fuel used in Diesel engines. Typical properties ol fuels in the kerosene boiling range are given in Table 1. 

The above TGA and elemental analysis studies are consistent with Van Krevelen s two step model for polymer charring (2) in which a polymer first rapidly decomposes at 500°C to fuel gases and a primary char residue characterized by modestly high hydrogen content. On further heating above 550°C, this primary char is slowly converted in a second step to a nearly pure carbon residue by the loss of this hydrogen. 

Carbon residue, in diesel fuel, 22 424 Carbon selenides, 22 87 Carbon sources, for fermentation, 22 25 Carbon steels, 23 291-297 cold working, 23 295-296 heat treatment of, 23 296 hot working, 23 294-295 microstructure and grain size of, 23 293-294 properties of, 23 292—293 residual elements in, 23 296-297 wrought, 23 296... 

When overheated, hydrocarbons tend to breakdown, leaving carbon residues (coke). This coke builds up on the inside of the heater tubes, slowing the transfer of heat from the tube walls to the product by restricting the flow of product and acting as an insulator. As the control system attempts to maintain the process outlet temperature at the setpoint, the fuel valves will open and the tubes subjected to an increased heat load. With the diminished ability of this heat to be transferred to the process fluid, the temperature of the tubing will increase. 

Some of the more critical properties related to marine fuels include ash content, carbon residue, calculated carbon aromaticity index (CCAI), density, sulfur, total sediment, and viscosity. A description of these properties and the primary reason for their implementation are provided below ... 

The pour point of residual fuel is not the best measure of the low-temperature handling properties of the fuel. Viscosity measurements are considered more reliable. Nevertheless, residual fuels are classed as high pour and low pour fuels. Low-pour-point fuels have a maximum pour point of 60°F (15.5°C). There is no maximum pour point specified for high-pour-point residual fuels. A residual oil paraffin carbon number analysis is provided in FIGURE 3-1. 

The amount of carbon present in fuel components can be correlated with a tendency to form deposits in fuel systems. Although the use of various detergent and dispersant additives helps to minimize deposit formation, the carbon residue value is still quite useful. 

A high carbon value for gasoline, jet fuel or 2 fuel oil is a good indication that the fuel has been contaminated with residual fuel oil. Heavy streams such as VGO, coker gas oil, and 6 fuel oil can contaminate gasoline, jet fuel and diesel fuel. These streams tend to form carbon residue when pyrolyzed and can be identified as fuel contaminants through carbon residue testing. 

High-carbon-residue values for marine diesel fuel, marine gas oil, and heavy marine bunker fuel can contribute significantly to exhaust system deposit problems. Deposit formation on exhaust ports and exhaust turbines have been linked directly to high carbon residue in fuel. 

Conradson Carbon Number ASTM D-189 Determination of the weight of nonvolatile residue formed after evaporation and atmospheric pyrolysis of fuel or oil. This test method provides some information about the relative coke-forming or deposit-forming tendency of a fuel or oil. Products having a high ash value will have an erroneously high carbon residue value. 

Under the 1948 commercial standard CS 12-48, fuel oil No. 1 is defined as intended for vaporizing pot-type burners and other burners requiring this grade, whereas No. 2 is defined as for general purpose domestic heating for use in burners not requiring No. 1. The No. 1 fuel is therefore specified to have a low 10% point in the ASTM distillation to ensure quick starting, and a low end point and low carbon residue to ensure clean vaporization. 

The total yield of diesel fuels was 51.6 volume-percent of the in situ crude. The properties of these fuels fell within the limits (Table V) of those of corresponding petroleum diesel fuels currently marketed in the United States (8) except for the carbon residue of the S-M shale-oil diesel fuel this residue was slightly higher than those of the petroleum diesel fuels but was probably acceptable. The value of 0.36 weight-percent for the carbon residue on the 10-percent bottoms of the S-M fuel was only a... 

The carbon residue (ASTM D-189 and ASTM D-524) of a crude oil is a property that can be correlated with several other properties (Figure 2-14). The carbon residue presents indications of the volatility or gasoline-forming propensity of the feedstock and, for the most part in this text, the coke-forming propensity of a feedstock. Tests for carbon residue are sometimes used to evaluate the carbonaceous depositing characteristics of fuels used in certain types of oil-burning equipment and internal combustion engines. 

Because of the extremely small values of carbon residue obtained by the Conradson and Ramsbottom methods when applied to the lighter distillate fuel oils, it is customary to distill such products to 10% residual oil and determine the carbon residue thereof. Such values may be used directly in comparing fuel oils, as long as it is kept in mind that the values are carbon residues on 10% residual oil and are not to be compared with straight carbon residues. 

Gulfining a catalytic hydrogen treating process for cracked and straight-run distillates and fuel oils, to reduce sulfur content improve carbon residue, color, and general stability and effect a slight increase in gravity. 

Table IV gives the properties of the SRC-II fuel oil compared to a low-sulfur residual oil utilized in a recent combustion test. The SRC-II fuel oil is a distillate product with a nominal boiling range of 350-900°F, a viscosity of 40 Saybolt seconds at 100°F and a pour point below -20°F. Thus, it is readily pumpable at all temperatures normally encountered in transportation of the fuel oil. The fuel oil has a very low content of ash and sediment as well as a low Conradson carbon residue. These characteristics are favorable from the standpoint of particulate emissions during combustion. Tests of compatibility with typical petroleum fuel oils and on stability of the coal distillates over time have not revealed any unusual characteristics that would preclude utilization of these coal-derived fuels in conventional boiler applications.

Carbon residue may be present in the diesel fuel in suspended form. The carbon residue can be removed by ultracentrifuging. In the Smuda process some of the light layered clays can be carried out of the pyrolysis vessel with the hot pyrolytic gases and can be entrained in the condensed fuel. 

Conversion performance of reclaimed oil and hydrocarbon gases reaches 70% or higher. Two kinds of carbon residues are formed in the dehydrochlorination and thermal cracking processes. They can also used as solid fuel for industries. Their compositions are shown in Table 26.20. 

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