Document 3g2LmqEZ8q9bwYjV8xDvjb8n

472 CHAPTER 33 1959 Guide Grads of Fuel OS'* Toble A .... Detailed Requirements for Fuel Oils* Flash Point F Wafer Carton Poor Point F end Sed- feddue Ad) imont on 10% %br %by Redd- Wf. Vol. HM % DirfiUafion Tem perature* F 10% 90% End Point Point Point Soybofl Viscosity Universal Farol at 100 F at 122F Kinematic Viscosity Genfidoker at 100 F at 122 F Min. Max. Max. Max. Max. Max. Max. Max. Max. MM. Max. Min. Max. Min. Max. MM 1. A distillate oil intended for va 100 0 Trace 0.15 420 625 porising pot-type burners and or other burners requiring this Legal grade** API gravity 35 (min.) 2.2 1.4 2. A distillate oil for general pur. pose domestic heating for use in burners not requiring No. 1 API gravity 26 (min.) 100 or Legal 20* 0.10 0.35 675 40 (4.3) 4. An oil for burner installations 130 20 0.50 not equipped with preheating or facilities Legal 5. A residual type oil for burner 130 installations equipped with pre or heating facilities Legal 1.00 0.10 0.10 125 45 (26.4) 5.8 150 40 32.1 (81) 6. An oil for use 'in burners equipped with preheaters per mitting a high viscosity fuel 150 or Legal PS 300 . 150 or Legal 2.00* 1.0 300 45 40 25 (638) (92) PS 400 150 2.0* 60 * tUramirint tbe aecenity (or Icnr aalftir fuel oils used ia connection with heet-tieetment. nan-ferrous metal, cfaus sad eerssuo furusees sad other wpodnl oaea, s sulfur requirement may be specified sa 0.5% for No: 1, 1.9% for No. 3, sad ao limit for Nos. 4, fi sad 6. Other sulfur limits mxy be specified cal; by mutual ssreemeut between tbe buyer sad seller. b It la the intent of these risaaifrrations that failure to meet say requirement of s (iven trade does not aotamaUeally place an oil in the next lower grade unless la {act it meets all requirements of the lower grade. * Lower or hither poor points may he specified o p any airHidnn rqtiird hywwUtirtwwf .t^g*** th.n t>..n ~t p--jnfr- . point lower * No. 1 <xl shall pass teat for eccrceiuo made in accordance with paragraph IS ASTM Specification! Jar PuM Oilt, D 396 - 4S. * The 10 Percent point may be specified at WO F mrnimun for use ia other than stomiziat burners. f The amount of water by distillation, plus tbe sediment by extraction, shall not exceed 2.00 percent. The amount of sediment by extraction, shall not exceed &50 percent, A cWWrtWm in quantity shall ha mxfa far all wtr anH --rfiramt ir. rrrmmaa <41(1 prwwt P8100 sad PS 400are Padfio Specification numbers. Balance of table from Comnsrctoi Standard C812-42 and ASTU Material* Specification for Pv*l OH* D 290 - tS. P8 200 ia a residual cal fee use without prebeating in furnaces aad burners requiring a low viscosity fuel, sail commonly described as light fuel oil. domestic fuel aO, or tow viscosity fuel oil. PS 400 is a residual ml far use in furnaces and burners equipped with preheaters permitting a high viscosity fuel, and iwr.mjmiy described as industrial fuel oil, heavy fuel oil, or high viscosity fuel oil. coast area. These oils correspond approximately to ASTM designations No. 5 and No. 6 respectively. Oils are classified by their viscosities. Other characteristics of fuel oils which determine their grade classification in the Commercial Standard, and their suitability for given uses are the flash point, pour point, water and sediment content, carbon residue, ash, and distillation characteristics. The flash point of an oil is important with regard to safety in handling and in storage. The distillation charac teristics determine whether or not tbe oil can be com pletely evaporated in some types of burners, and whether cracking will be likely to occur prior to combustion. A low pour point and low water content are necessary for handling and outdoor storage in cold climates. Sediment should be low to prevent clogging of strainers. Carbon residue is related to the rate of accumulation of unbumed material in some types of burners. A low viscosity allows the fuel oil to flow through supply lines readily and to be broken up into small droplets in atomizing type burners. The sulfur content is of importance because undesirable compounds of sulfur may be formed in certain industrial processes. Some of these characteristics of a fuel oil are required to lie within certain limits for each of the grades of fuel oil listed in Commercial Standard CS12-48. Some fuel oils do not fall into any of the grade classifications of the Commercial Standard because failure to comply with all of the require puels and Combustion Table 5 .... Approximate Gravity and Calorific Value of Standard Grades of Fuel Oil Comwerriof Standard No. Approxiroato Gravity API Weight lb per gation Calorific Vaium 8tv Per Gallon 1 38-45 6.951-6.675 137,000-132,900 2 30-40 7.296-6.870 141,800-135,800 4 12-32 8.212-7.206 153,300-140,600 5 8-20 8.448-7.778 155,900-148,100 6 6-18 8.571-7.882 157,300-149,400 ments of one grade does not automatically place the fuel oil in the next lower grade, unless it meets all of the require ments of the lower grade. By ultimate analysis the No. i and No. 2 fuel oils con tain 84 to 86 percent carbon, up to 1.0 percent sulfur, and the remainder predominantly hydrogen. The heavier grades of fuel oil, Nos. 4, 5 and 6, may contain as much as 88 percent carbon, as low as 11 per cent hydrogen, and con siderably more sulfur than is permissible in the domestic grades. Due to variation in the constituents of different fuel oils and the different refining methods used, the API gravities and calorific values of the different grades of fuel oil cover a range in each grade with some overlapping between do mestic grades and between commercial and industrial grades. API gravity, generally used when referring to specific gravity of oil, is obtained by the following formula in which the term specific gravity at 60/60 F indicates the ratio of the weight of a given volume of oil at 60 F to' Hie weight of the same volume of water at 60 F: Degrees API -- -- 131.5 specific gravity at 60/60 F The API gravity of water at 60 F is 10.0. The relation be tween the API gravity of fuel oils and their calorific value is shown in Table 5. Grades No. 1 and No. 2, which are distillates, are used predominantly in domestic heating equip ment whereas grades 5 and 6 are used in commericol and industrial burners. Grade 6 requires preheating to increase its fluidity and to permit atomization, whereas grade 5 may be used in some burners without preheating. Grade 4 fuel oil does not require preheating' and can even be burned satisfactorily in a limited number of domestic burners. Sources and Properties of Residual Fuel Oils Fuel oils Nos. 5 and 6 always contain residues remaining from the refining of crude oils. No. 4 oil will sometimes con sist entirely of heavy distillates but generally contains re sidual stocks. The residues may be classified, in accordance with their previous processing, as straight-run, vacuum-flashed, or cracked residues. Straight-run residues are the materials in crude oil that cannot be distilled at atmospheric pressure without appreciable decomposition and hence are removed as bottom fractions from crude topping units. These ma terials, often referred to as topped or reduced crude, are sometimes blended into fuel oil, but more frequently are processed, either by vacuum distillation or by thermal crack ing, to produce additional distillates. Residues from vacuum distillation processes are widely used as residual fuel blend ing stocks. Vacuum-flashed residues from some crudes must be subjected to a mild thermal cracking, known as viscosity 473 breaking, before they can profitably be blended- into fuel oils. Residues produced by thermal cracking of straightrun or vacuum-flashed residues or by thermal reforming of heavy naphthas, also are used in residual fuel oils. In processing reduced crudes and other stocks that yield residual fuel-blending stocks, the refiner evaluates the severity of treatment against, among other factors, the effect on certain properties of the residues. Perhaps the most sig nificant of these properties is viscosity. Maintenance of fuel viscosity within a certain range by preheating of the oil is necessary to obtain satisfactory combustion efficiency with most burners for heavy oil. In most instances there is a maximum temperature to which the oil should be pre heated. Consequently a maximum viscosity is usually placed on the finished product. The second property of oil that is markedly sensitive to refining procedures is specific gravity. Residues may have gravities on either side of API 10, i.e., they may be either lighter or heavier than water. Since residual fuels in many instances are stored and used in the presence of water the densities of the fuel oils must differ sufficiently from water to assure their separation into distinct layers. The Unfits imposed by viscosity and specific gravity speci fications are met in part by refining practices and in part by hifrnHing residues with distillates. These distillates may be straight-run gas oils and distillates produced by thermal or catalytic cracking. Blending of residues and distillates generally entails down-grading of the latter. Consequently efforts are made to reduce to a minimum the quantities of cutter stock (the refinery term for distillates used for this purpose) necessary to meet manufacturing specifications. Heavy catalytically- or thermally-cracked distillates are generaUy used as cutter stock, not only because they are of less value for further processing than straight-run gas oils, but also because they have greater solvency for asphaltic ma terials in cracked residues. This discussion of residual fuel oils has been concerned principally with No. 6 fuel oil, the heaviest grade of residual fuel. Two other grades of residual fuels, Nos. 4 and 5, are pro duced and marketed. These fuels have lower viscosities and higher gravities than No. 6 fuel oil. Generally these specifi cations are met by increasing the ratio of cutter stock to residue, but occasionally these lighter fuels are made by blending No. 6 and No. 2 fuel oils. Sometimes No. 4 oil will consist entirely of heavy distillates but generally this grade of fuel contains residual stocks. Due to their higher distillate content both No. 4 and No. 5 grades bring higher prices than No. 6 fuel oil, and fre quently they are priced on a different basis, i.e., in centsper-gallon rather than doliars-per-barrel. Oil Burning Indexes A number of indexes have been used, or proposed, as an indication of the burning qualities of distillate fuel oils based on one or more physical measurements made on the oil. These may be summarized as follows: A. Indexes based on a single physical test: (l) API gravity,* (2) Aniline point* (3) Institute of Petroleum smoke test, (4) Carbon-Hydrogen ratio baaed on flue gas analysis or ultimate analysis, and (5) Percent aromatics determined by sulfuric acid absorption tests.' B. Indexes based on two or more physical tests: (l) Diesel index' based on API gravity and aniline point, (2) Institute of Petroleum cetane number* based on the API gravity and 50 percent distillation point, (3) Universal Oil Products char acterisation factor* based on specific gravity and average