4. Carbon Residue Test 1. OBJECTIVES: 1) To be able to determine the carbon residue of a liquid fuel. 2) To be able to know the definition of a carbon residue test. 3) To be able to have knowledge about car bon residue of a liquid fuel. 2. THEORY AND HYPOTHESIS: Carbon residue for a fossil fuel can be defined as the tendency of that fuel to form carbon deposits at high temperature in an inert atmosphere. Carbon residue for a fuel is measured in weight percentage (wt %) or parts per million by weight (ppm wt). High carbon residue value is undesirable for a fuel. When oil is heated to a high temperature in the absence of sufficient air a portion of the oil will distill, thus leaving a carbon residue. The amount of this residue is an index to the extent the oil is likely to decompose in service. Under engine-operating conditions, the amount and type of the carbon formed has an important effect upon the performance of the engine. While no maximum residue specifications for lubricating oils are commonly given, a relatively smaller amount in one oil compared with another should be favorable. Apparatus known as the Conradson carbon-residue tester is widely used in this country. It consist of a porcelain crucible with a Skidmore iron crucible resting upon a layer of sand in a second larger iron crucible, all of which are supported upon a wire triangle on a metal stand of specified dimensions. The assembled tester is shown in the figure. The crucibles are surrounded by an asbestos block and covered by a sheet-iron hood and chimney. Heat is applied by a Meker burner. An analytical balance is used to weigh the sample of oil and the residue.
A clean porcelain crucible is weighed to the nearest 5mg, then filled with a 10g sample of oil and weighed to the same accuracy. The crucible is then placed in a Skidmore crucible. The sand in the large iron crucible is leveled, and the Skidmore crucibles are covered, and the assembly of crucibles is centered on a wire triangle with the asbestos insulation on a suitable ring stand. The whole is covered with the sheet-iron hood, and heat is applied with a strong flame from the Meker burner so that the pre ignition period will be from 8.5 to 11.5 min. When smoke appears from the chimney, the burner is moved or tilted so that the flame passes up one side of the crucible and ignites the oil vapor. The burner is momentarily removed and the gas flame adjusted so that the vapors burn
uniformly with the high flame above the chimney but not above the bridge on top of the chimney. The burning period should be from 12 to 14 min. When the burning and smoking have ceased, the burner is adjusted so that the bottom of the iron crucible is heated to a cherry red for exactly 7 min. The total period of heating should be 28 to 32 min. The burner is then removed and the apparatus is allowed to cool for about 15 min. The porcelain crucible and contents are reweighed, and the percentage of carbon residue is calculated on the basis of the original sample weight. The Conradson Test for the amount of carbon in oil is accurate if test is properly performed. Also through the experiment it was found out that Carbon residue is very small compared to the amount of other components in oil. Carbon residue test determine the percentage of carbon that remains in a sample after the volatile vapors had bee n driven off by heat. 3. LIST OF APPARATUS: 1) Meker Bunsen Burner
http://dictionary.reference.com/browse/meker%20burner
2) Hood Porcelain Crucible
3) Tripod
http://en.wikipedia.org/wiki/Tripod 4) Wire Mesh
5) Chimney
4. SET – UP OF APPARATUS: 5. PROCEDURES: 1) Place the two glass bends provided which are about 1” in diameter in the porcelain crucible and include their weight in the net weight of the crucible. Then, add 10 grams of the oil to be tested accurately weighed and free from impurities. 2) Place the crucible in the center of the Skidmore crucible. Level the sand in the sheet-iron crucible and set the Skidmore crucible as it is in the exact center of the iron crucible. 3) Apply the covers to both the Skidmore and the iron crucible, the one to the later fitting loosely to allow exit of vapors that are formed. 4) Place the bare nichrome wire triangle on the metal tripod on the asbestos block as hollow sheet metal box. Center the short iron crucible into the block with its bottom resting on top of the triangle and cover the whole with the sheet iron hood in order to distribute the heat during the process. 5) Apply heat with a highly strong flame from a Meker type gas burner so that the pre ignition period will be 10 and 1 1/2 minutes. When some smoke appear above the c himney, immediately move or tilt the burner so that the gas flame plays on the sides of the crucible for the purpose of igniting the vapors. Then, remove the heat temporarily and before replacing adjust the gas flame so that the ignited vapors burn uniformly with the flame above the chimney, but not above the wire bridge. Heat may be increased if necessary, when the flame does not show above the chimney. The period of burning the vapors shall be 13 and 1 minutes. 6) When the vapors cease to burn and no further blue smoke can be seen, readjust the burner to hold the heat as in the beginning so as to make the bottom, and the cover part of the sheet-iron crucible, red and maintain for exactly 7 minutes. The total period of heating should be 2 to 30 minutes, which constitute an additional limitation on the tolerances for the preignition and burning periods. 7) There should be no difficulty in carrying out the test exactly or directed with the gas burner provided, using city gas with the top of the burner about 2” below the bottom of the crucible. The time periods should be observed with whatever burner or gas used.
8) Remove the burner and allow the apparatus to cool until no smoke appears, then remove the cover of the Skidmore crucible. Remove the porcelain crucible with heated tongs, place in the dessicator, cool and weigh. 9) The total weight of the crucible plus beads and 10 grams of oil at start minus the weight of the crucible plus beads and carbon residue at finish equals loss of oil on grams. The 10 grams of oil minus loss in weight of oil equals carbon residue in grams, divided by 10 grams equals % of carbon residue. weight of carbon residue % of carbon residue 100% weight of oil wt . of residue wt . of crucible and carbon residue wt . of crucible % carbon
residue
wt . of crucible & residue wt . of crucible wt . of crucible & oil wt . of crucible
6. DATA & RESULTS: Weight of crucible = ______________________ Weight of oil = __________________________ % of carbon residue = _____________________ Weight of carbon residue = _________________ 7. SAMPLE COMPUTATIONS: (By Students) 8. QUESTIONS : 9. 10. 11. 12.
ANSWERS: (By Students) DISCUSSION: (By Students) CONCLUSION / RECOMMENDATION: (By Students) REFERENCES: (By Students) -
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