Ultimate Analysis of Coal
- 1. Ultimate Analysis – Constituents of coal Fossil Fuel Engineering – ERG 252 (1+1) S.Vignesh – BTG-12-037
- 2. Introduction A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, then bituminous coal, and lastly anthracite. This involves biological and geological processes that take place over a long period of time. Heat and pressure acts on it to finally convert into coal.
- 3. Ultimate Analysis • Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulphur, oxygen, nitrogen. • Ultimate analysis is also known as elemental analysis, it is the method to determine the Carbon,Hydrogen,Nitrogen,Sulphur and Oxygen content present in solid fuel.
- 4. Need For Analysis • It is essential to understand the properties of biomass materials to evaluate their utility • As chemical feedstock's and also design suitable gasifies systems. The analysis is carried out to find the oxygen required for combustion for efficient production of energy. • Two types-proximate and ultimate analysis • Proximate-it determines moisture content, volatile matter, ash and fixed carbon content of a fuel. It is reported as dry weight.
- 5. Determination of carbon & hydrogen • About 0.2g of accurately weighed coal is burnt in oxygen in apparatus shown above. • CCO2 & HH2O • KOH & CaCl2 absorb CO2 & H2O respectively. • Increase in weights of the tubes are noted.
- 6. % of C: increase in weight of KOH tube*12*100 weight of the coal sample taken*44 % of H: Increase in weight of CaCl2 tube*2*100 weight of coal sample taken*18
- 7. Determination of Nitrogen • 1g of accurately weighed powdered coal is heated with conc.H2SO4 in kjeldahl flask. • It is treated with excess KOH.
- 8. • Liberated ammonia is distilled over and absorbed in a known volume of standard solution of acid. • Unused acid is determined by back titration with standard NaOH. % of N is volume of acid used*normality*1.4 weight of coal sample taken
- 9. Determination of sulphur • Sulphur is converted into sulphate. • The washings are treated with BaCl. • BaSO4 is precipitated. • Precipitate is filtered, washed and heated to constant weight. • % of S = weight of BaSO4 obtained*32*100 233*weight of coal sample taken
- 10. Determination of ash and oxygen • Coal sample of accurate weight in a crucible is heated in muffle furnace at 700+50 degree Celsius for ½ an hour. Crucible is taken out and cooled first in air and then in desiccators and weighed. • % of ash = weight of ash left*100 weight of coal taken • % of oxygen is 100-percentage of (O+H+S+N+Ash)
- 11. carbon hydrogen oxygen nitrogen Sulphur 55-60 6-6.5 30-35 1.5-2 0.6-1 Peat
- 12. Carbon hydrogen Oxygen nitrogen Sulphur 70-73 4.6-5.5 22-26 0.6-1.0 0.6-1.5 Lignite
- 13. Carbon Hydrogen Oxygen 80 6 15 Bituminous
- 14. Carbon Hydrogen Oxygen 93 4 3 Anthracite
- 15. Total carbon • Fixed carbon+carbon present in volatile matter • High total carbon represents high calorific value of the fuel.
- 16. Hydrogen • It increases calorific value-H2 remains as coke oven gas • Associated with volatile matter of coal • Peat to bituminous contains 4.5-6% H2 • Anthracite contains only 1-2%
- 17. Nitrogen • Present up to 1-3% • Comes from protein us matter in vegetable matter. • Inert nitrogen decreases calorific value. • As coal matures, extractable nitrogen decreases. • Its proportion does not depend on rank. • It varies from 1-2% in all.
- 18. Sulphur • It increases calorific value but is undesirable. • Its oxidization product in presence of moisture cause corrosion of equipment and pollution. • When used in steel making it badly affects properties of iron and steel. • Sulphur exists in 3 forms-pyritic, organic & sulphate • World coal contains 1 to 3% sulphur.
- 19. Oxygen • Less the oxygen-better is the coal. • Decreases from lignite to anthracite. • As oxygen content increases, moisture holding capacity increases and caking power decreases.
- 20. Phosphorus • Undesirable in metallurgical as it badly affects properties of metals. • Indian coking coals have less than 0.15% phosphorus.
- 21. Fuels % C % H % O % N % S % Ash Peat 23 10 59 1.5 0.5 6 Lignite 42 7 43 1 1 6 Bituminous 77 5 5 1.5 0.5 11 Sub- Bituminous 59 6 29.5 1 0.5 4 Semi- Anthracite 80 3.5 4.5 1.5 0.5 10 Anthracite 86.5 2.5 3 0.5 0.5 7 Ultimate Analysis – Constituents of Coal
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