-Ms. Neha Patni DEFINITION: Any combustible substance which is - PowerPoint PPT Presentation

-Ms. Neha Patni

 DEFINITION: Any combustible substance which is obtainable in bulk, which may be burnt in atmospheric air in such a manner that the het evolved is capable of being economically used for domestic and industrial purposes for heating and generation of power.  FUEL + O2 Products + Heat

Th The co compositio sition n of co coal l vari ries s acc ccord rdin ing g to the degree of coali lifi ficati ation. In order to co compar are e the coals ls for the consum umer er, , pri rize fix ixation tion and many y other er factors rs ,the analysi lysis s of co coal l is is carrie ied out Coal l analy lysis sis are of two ty types es : Pro roxim imat ate e analysis lysis 1. 1. Ul Ultim imat ate e analy lysis is 2. 2.

1.SUITABILITY: For instance , coke made out of bituminous coal is most suitable for blast furnace , inspite of the fact that charcoal or anthracite may also be used. 2.COST: The fuel should have a low cost and on prolong storage it should not change its properties significantly. 3.CALORIFIC VALUE: The fuel must possess high calorific value (heat per unit mass or volumes)and produces no hazardous gases which might pollute the atmosphere. 4.IGNITION TEMPERATURE OR KINDLING TEMPERATURE: The minimum temperature at which the substance ignites and burns without further addition of heat from outside . Fuel should possess a moderate ignition temperature . Too high ignition temperature causes difficulty in kindling while too low ignition temperature may create safety problems during storage , transport and use of the fuel . The presence of moisture and foreign material in the fuel always decreases the ignition temperature. 5.Flame temperature: The highest temperature at which an substance can be heated by flame is called flame temperature . The flame temperature generally increases with the increases in the number of combustibles.

 6.MOISTURE: It should be very low. High moisture content lowers the effective calorific value of the fuel.  7.NON COMBUSTIBLE MATTER CONTENT: The non combustible matter forms clinkers after combustion and it reduces the heating value and involves the cost of disposal after the combustion.  8.VELOCITY OF COMBUSTION: Velocity of combustion should be moderate. Too high velocities of combustion are not required whereas too low velocities causes loss of heat due to radiation.  9.Control of the process: The fuel should be such that its combustion can easily be controlled i.e. It can be easily started or stopped.  10.Ash: It should produce minimum quantity of ash upon combustion . The Higher proportion of ash may have lower calorific values.  11.Sulphur and Oxygen: The fuel should have minimum quantity of sulphur and oxygen because higher sulphur contents may create corrosion , while oxygen decrease ignition temperature .  12.Safety: It should be safe while transporting and storage.  13.Production of side products: It should not produce any undesirable products(i.e. Noxious gas and pollutants) upon combustion which are harmful to the atmosphere.

Characteristics of a good fuel (REVISION)

Ca Calo lorific val rific value ue

 G.C.V. (Gross calorific value) or H.C.V. (High calorific value)  Definition : “Total amount of heat liberated when unit mass bond and products are cool down. They are not allow to escaped.”  G.C.V = N.C.V + LATENT HEAT.  N.C.V (Net Calorific value ) or L.C.V (Low calorific value)  Definition : “ Total amount of heat liberated when unit mass of fuel bond and products are allowed to escaped.”

GCV = 1\100 (8080C + 34500(H – O\8)+2240S) NCV=[GCV – 0.09 H * latent heat of condensation] Where , C= percentage of carbon H=percentage of hydrogen O=percentage of oxygen S=percentage of sulphur

- Most useful compound to human kind

 Peat  Lignite  Sub-bituminous  Bituminous  Anthracite

Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions. In its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water

Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation

Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam- electric power generation. Important source of light for the chemical synthesis industry.

Bituminous coal, dense sedimentary rock, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke

Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil , as from the deposits in Pennsylvania

Proxim imat ate e analysi lysis s is is a em empiri irical al rather er than n true analys ysis. is. It in inclu ludes des the determina mination ion of the foll llowi wing: ng: Mois isture ure content ent 1. 1. Vola Vo latil ile matter er 2. 2. Ash Ash 3. 3. Fix ixed ed carbon 4. 4.

 Moistu sture re content ent : Moisture sture content ent should ould be low. w. Reason son: For eve very ry perc rcen ent of moisture ture presen esent 1% of 1. 1. heat t is lost. Increa creases ses transport nsport cost. 2. 2. Ho Howe wever ver about ut 5-10% moistur ure e is desi sirab rable e as it prod oduc uces es a uniform form fuel bed and less s of fly ash. h.

Moisture sture co content tent is determined rmined by Heati ting ng a k known wn quantit tity y of air-drie dried d co coal l to 1. 1. 105 105-11 110 0 C C for an an hour. r. It is co cooled led and then n weighe hed. d. 2. 2. Loss ss in weight ht of co coal l is reported rted as moisture sture 3. 3. co conten tent t on per erce centa ntage ge bas asis Percentage centage moisture sture= = (W-w) w) x 100 /W Wher ere, e, W=wei eight ght of sam ampl ple e bef efore ore hea eating ing w= weight ht of samp mple le after r heati ting ng

 VOLAT ATILE ILE MATTER ER : Volati tile e ma matter er consi sists sts of a mi mixture ure of ga gaseo eous us and liquid id prod oducts ucts resu sulting ting from the e thermal rmal decomp mposi ositi tion on of coal.Eg Eg : H 2 ,CO, O,CH 4 It does es not include ude mo moisture ture of coal. Volati tile e matter er must t be low. w. Reason: son: A hi high h per ercentage centage of vola latile tile mat atte ter r indicates icates that at 1. 1. a l large e part fuel is burnt nt as a g gas which ch may y esca cape pe unburnt urnt. Higher her volati atile le matter ter means ns more e smoke oke and 2. 2. more e polluti lution on.

 %C= (12/44)*( )*(x/w x/w)*10 )*100  %H= H=(2/1 2/18)*(y/w)*10 8)*(y/w)*100 (where, x=weight of CO2 absorbed y=weight of H20 absorbed w=weight of original sample)

It is determine ned d by: Heating ng a known wn weight t of mo f moistu ture re fr free coal at 1. 1. around nd 950 C fo for 7 minutes. s. It is then cooled. d. 2. 2. Loss in we weight t is reporte ted d as volatile ile ma matter. r. 3. 3. Percenta tage ge volatil ile e matter =(x-y) ) X 100 / w where re x=weight ght of t f the sample befo fore heating ng y=w =weight ht of f samp mple aft fter heating ng

 ASH SH CO CONTEN ENT : Ash h usual ually ly consists sists of sili lica, a, alumina, ina, iron n oxide e and small l quanti antiti ties es of lime, magnes nesium ium etc. Ash h content ent shoul ould d be low. w. Reason: son: It red educes uces calori rifi fic c va value. e. 1. 1. In furnac rnace e gr grate, te, the ash h may restric strict t the 2. 2. passage ssage of air and d lowe wer the rate e of comb mbus ustion ion.

It is determined ermined by : He Heating ing a known wn we weigh ght t of coal sampl ple e at 1. 1. 75 750 C fo 0 C for about ut 1 h 1 hour. ur. The remaining maining mass ss is then n cooled d and d 2. 2. we weigh ghed ed. The remaini aining ng mass s in terms rms of perc rcen entage age 3. 3. is repo ported rted and ash h content. ent. Pe Percentage centage ash= h= z X 100/ W Where re z=wei weight ght of resid sidue ue left W= W=we weight ight of coal sampl mple. e.

 FIXE XED D CA CARBON : Fixed d carbo bon n content ent must t be high gh. Reason son : Hi High gher er fixed ed carbon bon content ent me means ns gr great eater er 1. 1. calori rifi fic va value. e. Pe Perce centage ntage of fixed ed carbon bon = 100 100 – [% moisture ture + %vo volatil atile e matter er + %ash] sh]