Fuel

1. FUELS AND COMBUSTION&PHASE RULE AND ALLOYSPREPARED BY Dr.M.VADIVEL,ASSISTANT PROFESSOR,DEPARTMENT OF CHEMISTRY,MOHAMED SATHAK ENGINEERING COLLEGE

2. Fuel Any combustible substance which burns in air producing heat is called fuel.Fuels contains carbon and hydrogen which burning produce heat energy as the process is exothermic. C+O2CO2+94.K. Cal.s Classification : 1)Primary fuel(natural fuel): 2)Secondary fuel(primary fuel):

3. Characteristics of good fuels • Higher calorific value • Burn with non smoky flame • Should not produce any desirable and polluting products. • Greater flexibility. • Complete combustion.

4. Primary & secondary fuel • Advantages: • High calorific value. • Do not produce smoke • Easily transported • Complete combustion • Disadvantages: • Highly inflammable • Produce fire hazards

5. Calorific value Higher calorific value The amount of heat liberated when one unit quantity of a fuel is completely burn in air and the products are cooled down to the room temperature The amount of heat liberated by the complete combution of a unit mass of a solid or liquid fuel or unit volume of a gaseous fuel. It is expressed in cal/gm or K.gm Lower calorific value The amount of heat evoived when one unit of quntity of a fuel is completely burnt in air and the products produced are allowed to escape

6. Coal It is a fossile fuel which is formed by the decomposition of dead plants and animal in earth crust under high temp & pressure Classification Classification based on their rank which is assessed by the extent by the maturation and carbon content. They are ranked as (i) low grade (ii)High grade

7. Analysis Two types • Proximate(fixed carbon content) • Ultimate(total carbon content) Determination of moisture content % of moisture content = loss of wt after heating  100 Wt of coal before heating Estimation of volatile matter % Of volatile matter= loss of weight  100 Weight of air-dry coal

8. Ash content % Ash content= Wt of ash 100 Weight of air-dry coal Fixed carbon It is the pure non volatile carbon content in the coal . % of fixed carbon=100-(% of moisture+ %of volatile matter +% of ash)

9. Ultimate analysis Determination of total carbon content,H2,N2,O2,and ashcontents in a sample of coal. It is also called elemental analysis.this analysis is useful to the designer of coal burning equipments and also useful to calculate theoritical value of coal using Dulong ;formula

10. Estimation of carbon and hydrogen A known weight of a sample of coal is heated in a current of air in a combustion apparatus.all carbon present are converted into CO2 and all H2 into H2O.this mixture is passed thgrough previously weighed KOH and anhydrous Cacl2 tubes is turn.CO2 is absorbed by KOH and weight its increases.let the increase in KOH tube be X gm. On combustion: C+O2 CO2 On absorption:2kOH + CO2 K2CO3 + H2O Similarly :H2 + 1/2 O2 H2O Cacl2 Cacl2.7H2O The %of carbon in coal sample = Increase in KOH tube x12x100 Wt of coal sample x44 Significance: • Higher % of C & H2 are desirable properties of a coal; • They give higher calorific value • Combustion chamber is based on the % of carbon.

11. Carbonisation Types • The conversion of coal into coke is known as carbonisation. • Low temperature carbonisation(LTC) • High temperature carbonisation(HTC) PETROLIUM It is the natural oil present at the depth of earth crust. It is a mixture of parrafin ,olefin, and aromatic hydrocarbons with sall quantities of organic compounds.

12. Otto Hoffman’s method Recovery of by –products The gas coming out from ovens during carbonisation is passed through various scrubbers and condensers. Recovery of tar: The gas is passed through a tower into which liquir NH3 is sprayed. Tar settles down. Then NH3 recovered by heating.

13. Instrumentation

14. Recovery of NH3: The oven gas is then passed through another tower in which water is sprayed. NH3is collected at the bottom as NH4OH. Recovery of naphthalene: It is collected in another tower into which cold water is sprayed. Naphthalene settles at the bottom.

15. Benzenes and other hydrocarbon. They are collected in the next tower into which petroleum (or)creosote is collected. removal of sulphur compounds. the gas is passed through a tower packed withFe2o3.here h2s and other hard, strong ,porous mass called metallurgical coke.

16. Characteristics of Petroleum • High purity • Porosity • Calorific value • Combustibility • Strength • Reactivity

17. Advantages: • Heating is done more efficiently and economically as it done by regenerators. • Valuable by products are recovered. • Carbonisation takes place in a short oeriod producing 70% transformation. Classification Paraffin base oil:(Saturated hydrocarbons or paraffins) Naphthenic or asphaltic oil:(naphthenes+paraffins+aromatics)

19. Cracking • High mol.wt and high boiling hydrocarbons are broken into low mol.wt low boiling fraction. • Thermal Cracking • Cracking is carried out not at high temp and pressure in the absence of catalyst. • Catalytic cracking • It is carried out in the presence of catalyst at low temp and pressure

20. Knocking • Some time the mixture petrol vapour and air undergoes spontaneous combustion even before sparking as the result of compression. • Chemical structure @knocking • Knocking tendency of a petrol mostly depends upon the chemical structure of constituents present in it. • Eg;pentane>n-hexane>n-heptane.

21. Octane number or Cetane number • As the % of iso-octane in a binary mixture of iso-octane and n –heptane which has the same knocking characteristics as the petrol sample. • Cetane number • It expresses the knockings characteristics of diesel. The%ofcetane in a mixture of cetane and 2-methylnaphthalenewhich has the same ignition delay as the sample dieselwhen tested in a standard engine.

22. Bergius process

23. Requisites of an liquid fuel • High calorific value • High octane number • Should not contain undisirable substances. • Leave little carbon. Disadvatages Advantages High calorific value Easily trasportation No ash & residue Easily controllable Highly inflammable Effective burning engines costlier

24. Gaseous fuels • High calorific value • Do not produce more smoke • Complete combution • Easily transported

25. Compressed Natural Gas • It is a primary gaseous fuel, obtained along with petroluem. It is also called “marsh gas” • The average composition is CH4 =88.5%; • C2H4=5.5%;C3H8=3.7%;C4H10=1.8% Uses: • Domestic @industrial fuels • Synthesis of methanol and HCHO • Production of electricity Advantages High octane number Noise level is lower Safe fuel Low cost

26. Liquified petroleum gas Properties: • Toxic & colourless • Calorific value is 27,000k.cals/m3 • Non corrosive • USES: • Domestic & industrial fuel • Internal combution engine • Soldering & welding

27. Combustion Combustion is the process of rapid oxidation in which a fuel burns with the evolution of heat and light.The elements C,H,S@O present in the fuel do not undergo combution. Theoretical calculations: • C+O2 CO2 • 12+32 44

28. Flue gas analysis Signifigance: • Idea about the combution of the fuel • Higher composition of o2 indicates excess supply of air which may be regulated properly. • If both co&o2 are found together in flue gas ,it • Shows irregular and non uniform combution.

29. Orsat’ Method

30. Phase rule and Alloys • Phase rule: Defined as any homogeneous ,physically distinct part of a hetrogeneous system which can be separated from other part s since it is having a separate boundaries. Example: two phases system. Water and Oil It is a immiscible liquid.

31. Component: Defined as the minimum number of chemical species required to define the composition of each and every phase present in the system either directly or in the form of chemical equation. Example;Water system Ice (s) water vapour(g) water(l)

32. Degrees of freedom Defined as the minimum number of independent variables like temp,pressure,and concentration which should be specified to define the system completely. Example;For a pure gas,F =2 A pure gas obeys the gas equation is PV=RT. For water,F=1

33. Application of phase rule to one component system

34. Effect of change in temperature at constant pressure Consider effect of temperature at constant pressure.the point p in the system is liquid area.when it is heated at constant pressure,the increase of temperature shifts the system along py. At y evaporation takes place and the liquid is in equilibrium with its vapour.thebivarient reduces to monovarient. Further heating the liquid is converted to vapour.the system becomes bivarient.

35. Effect of change in pressure at constant temperature Consider the point x in the liquid water area.by decreasing the pressure, the state y is reached where the liquid can be converted to vapour.at point y the liquid is in equilibrium with vapour. The bivarient system is reduced to monovarient.further reduction in pressure at constant temp leads to the complete conversion of liquid into vapour.the system becomes bivarient.

36. Charecteristics of eutectic system • It have low melting point. • It is an invarient system. • In pb –Ag system the solution phase disappear. • Applications: • Safety devices & safety fuses. • Preparation of low melting alloys.

37. Simple eutectic system

38. Uses of phase rule • Applicable to macroscopic systems. • Equilibrium between various Phases are classified into components and degrees of freedom. • Limitations: • Applied only for system in equilibrium. • All phases of the system must be present under the same conditions.

39. alloys • Defined as any homogenious mixture of two or more metals or metal or non metals when fused together at a certain temperature and forms a new material on solidifications. • Ex:woods metal-it is an alloy of bismuth, cadmium and tin ,which has the m.pt of 700C

40. Importance and purpose of making alloys • Increasing the hardness of metal • Lowering the melting point of metal • Improving the corrosion resistance of metal • Modifying colour of the metal • Improving casting ability of metals • Modifying chemical activity of the metal

41. Preparation of alloys Fusion method the metal with high m.pt is melted.to this molten metal ,the other components are added with thorough stirring using graphite rod. Electrodeposition method Different metal salts solution is electrolytically reduced by passing direct current through electrodes. Reduction method Generally oxide of one metal is reduced in presence of other metal at high temperaturein an electric furnace with stirring.

42. Classiffication alloys (i)Ferrous (ii) non ferrous alloys Ferrous alloys (Major component present in this alloys is iron) Example: steel & stainless steel,etc. It is classified into three types: (i)Stainless steel (ii)Nichrome (iii)Aluminium-Nickel-Cobalt steel Non ferrous alloys (The alloys which do not have iron as one of the constituent are called non ferrous alloys. Example:brass contains cu & zn. It is classified into two types: • Brasses • Bronzes

43. Stainless steelHeat treatable stainless steelNon Heat treatable stainless steel(i) Magnetic stainless steel (ii) )Non- Magnetic stainless steel Heat treatable stainless steel It contains about 1.2%,c and less than 18% cr. These magnetic, tough and can be worked in cold condition and up to temperature 8000c Uses: • Making surgical instruments,scissors,blades,cultry,etc. • Non-Heat treatable stainless steel: Heat treating furnace at 1,800 °F (980 °C)

44. Nichrome It is a type steel alloyed with 60%NI,12%Cr,2%mn,and 26%Fe.it is an ex of heat resisting alloy and can be used up to1100oc Uses: Making boiler parts, gas turbines, steam lines,

45. Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching. It is noteworthy that while the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.

46. Non ferrous alloy Brasses and bronzes are the examples of non ferrous alloy.these alloys do not contain iron. Brasses: These alloys contain 60 to 90%of copper and 40 to10% of zinc.they possess greater strengh,durability and machinability than copper .they are having low m.pts than cu and zn.these are corrosion resistants and water resistants. Bronzes: These are alloys contain copper and tin as constituents.besidescu&sn other metals are also added to produce various types of bronzes. Uses: These are soft & durabilitymakingvalves,cins, statues.