Fuel oils carbon residues

Furnace Black One of the three principal processes used for making carbon black the others being the Thermal Black and the Channel Black processes. In the Furnace Black process, aromatic fuel oils and residues are injected into a high velocity stream of combustion gases from the complete burning of an auxiliary fuel with an excess of air. Some of the feedstock is burned, but most of it is cracked to yield carbon black and hydrogen. The products are quenched with water. 

Residual Fuel. The residual fuel produced by both the pilot and refinery meets all government specifications for low sulfur, high pour point 6 fuel oil. The residual fuels are in fact very "clean" as shown in Table VIII by the high hydrogen and low sulfur, metals, carbon and asphaltenes content. This stock is better utilized as cat cracker feed than residual fuel, since higher value gasoline and kerosene fuel can be easily produced via catalytic processing. 

Vacuum distillation of the atmospheric residue complements primary distillation, enabli r.ecoyery of heavy distillate cuts from atmospheric residue that will un r o further conversion or will serve as lube oil bases. The vacuum residue containing most of the crude contaminants (metals, salts, sediments, sulfur, nitrogen, asphaltenes, Conradson carbon, etc.) is used in asphalt manufacture, for heavy fuel-oil, or for feed for others conversion processes. 

The pricing of carbon black feedstocks depends on their alternate market as residual fuel oil, especially that of high sulfur No. 6 fuel oil. The actual price is deterrnined by the supply/demand relationships for these two markets. Feedstock cost contributes about 60% of the total manufacturing cost. The market price of carbon black is strongly dependent on the feedstock cost as shown in Figure 8. 

The numerous process heaters used in refineries to heat process streams or to generate steam (boilers) for heating or steam stripping can be potential sources of sulfur oxides (SO2, and SO3), nitrogen oxides (NO and NO2), carbon monoxide (CO), particulates, and hydrocarbons emissions. When operating properly and when burning cleaner fuels such as refinery fuel gas, fuel oil, or natural gas, these emissions are relatively low. If, however, combustion is not complete, or heaters are fired with refinery fuel pitch or residuals, emissions can be significant. 

Detailed analysis of residual products, such as residual fuel oil, is more complex than the analysis of lower-molecular-weight liquid products. As with other products, there are a variety of physical property measurements that are required to determine that residnal fnel oil meets specifications. But the range of molecular types present in petrolenm prodncts increases significantly with an increase in the molecular weight (i.e., an increase in the number of carbon atoms per molecule). Therefore, characterization measurements or studies cannot, and do not, focus on the identification of specific molecular structures. The focus tends to be on molecular classes (paraffins, naphthenes, aromatics, polycyclic compounds, and polar compounds). 

Elemental analysis of fuel oil often plays a more major role that it may appear to do in lower-boiling products. Aromaticity (through the atomic hydrogen/carbon ratio), sulfur content, nitrogen content, oxygen content, and metals content are all important features that can influence the use of residual fuel oil. 

In combustion of solids such as coal, wood, and charcoal the reaction of O2 occurs with solid carbon, sometimes leaving a solid ash residue. Fuel oil drops react with O2 in a similar process in boilers and in diesel engines. Since the exothermicity of these processes creates very large temperature differences, we will describe them in the next chapter. 

A wax can be defined as a linear, branched, or cyclic hydrocarbon typically containing from 17 to 60 carbon atoms. Low-carbon-number waxes are found in middle distillate fuels and typically constitute a low percentage of the paraffins found in distillate fuel. Higher-carbon-number waxes can be found in residual fuels and lubricating oil. The percentage of wax in residual fuel oils can vary widely depending upon the refining processes utilized. 

The term microcrystalline wax is commonly used to describe wax which is either mal-shaped or needlelike. This wax typically contains molecules >30 carbons in length. This wax can be present in various high-boiling-point fractions such as residual fuel oil and lubricant fractions. 

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 third way of coal pipelining intensification supposes using the carrier liquid different than water. Oil products (crude oil, residual fuel oil, kerosene, fuel or Diesel oil and various mineral oils) or hydrocarbons (methanol, ethanol, carbonic acid, and other liquid organic compositions) can be used as a carrier liquid. 

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. 

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