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  • Combustion and Heat production equipmentJean-Marie SEYNHAEVE PART 1 : Theoretical background

    1.1 Combustion = Chemical reaction1.2 Heating values of fuels

    PART 2 : Heat production : equipment

    2.1 Energy balance and equipment efficiency2.2 Combustion control2.3 Illustration of burners2.4 Practical problems

    Production de la chaleur - Chaudire

  • Part 1 : Theoretical background - Table of contentsI - COMBUSTION : CHEMICAL REACTION1.1 Examples of Chemical Reaction of Combustion, Fundamental Laws1.2 Air Required for Combustion - Flue Gases contents1.2.1 Solid or Liquid Fuel1.2.2 Gas Fuel 1.2.3 Practical ProblemsII - HEATING VALUES OF FUELS2.1 Heat of Reaction - Some Examples2.2 Definition of the Heating Value of a Fuel2.3 How to evaluate the Heating Value of Fuels2.3.1 Solid or Liquid Fuel2.3.2 Gas Fuel2.4 Practical Examples of Evaluation

    Production de la chaleur - Chaudire

  • Combustible Elements in Fuels :C S H2 CO CH4 C2H4 C2H6 C3H8 ......Alcans : CnH2n+2Alcens : CnH2nAromatics ... I. Combustion Chemical reaction : Fundamental laws Combustion : C + O2 CO2S + O2 SO2H2 + O2 H2OCO + O2 CO2CH4 + 2 O2 CO2 + 2 H2OC2 H4 + 3 O2 2 CO2 + 2 H2O........CnH2n+2 + ( 3n + 1 ) O2 n CO2 + ( n + 1 ) H2O Chemical Reaction of Oxidation + HEAT

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  • Chemical BALANCED reactions in terms of number of MOLES CnH2n+2 + ( 3n + 1 ) O2 n CO2 + ( n + 1 ) H2O n C n C + n O2 ( n + 1 ) H2 ( n + 1 ) H2 + ( n + 1 ) O2 ( 3n + 1) O2 ( 3n + 1 ) O2Molecular weight of molecules :Example : C2H6 : 2x12 kg/kmole + 3x2 kg/kmole = 30 kg/kmole

    Production de la chaleur - Chaudire

  • Some important laws :AVOGADROAt same pressure and temperature, 1 kmole of every gas occupies the same volume.For Normal Conditions ( t= 0 C, p = 760 mm Hg) :LAVOISIERThe total MASS in reaction remains constantApplication to air composition (combustive) :O2 N2 ( Ar Ne Xe ) Molar Fractions = Volume Fractions for air ( Avogadro Law ) :

    [O2] = 0.210 (kmole of O2 / kmole of Air or m3 of O2 / m3 of Air)[N2] = 0.790 " N2 " " N2 "- For Air : 1 kmole of O2 + 0.79/0.21 ( 3.76 ) kmole of N2[i]- Mass fraction for air : (i)0.210 kmole of O2 = 6.72 kg of O20.790 kmole of N2 = 22.12 kg of N2 1 kmole of Air = 28.84 kg of Air

    Production de la chaleur - Chaudire

  • Air required for Combustion Production of flue gases Pouvoir comburivore Pouvoir fumigneFuel composition For solid and liquid fuel : elementary mass composition

    Combustible Elements : C (H) (S) ... Oxygen in Fuel : (O) Humidity : (H2O) Inert Elements : (N) (Ash)

    For gas fuel : molar (volume) composition

    Combustible components : [H2 ] [CO ] [CH4 ] [C2H4 ] [C2H6] ... (Oxygen in Fuel : [O2 ]) Humidity : [H2O ] Inert Elements : [N2 ] [CO2 ]

    Definition : Excess of air

    Production de la chaleur - Chaudire

  • SOLID and LIQUID FUEL - Combustion accounting

    Production de la chaleur - Chaudire

    Feuil1

    Elements before combustionElements after combustion - Flue gases

    1 kg of fuelkmole of fuel

    (C)(C)/12 of C(C)/12(C)/12----

    (H)(H)/4--(H)/2--

    (S)(S)/32 of S(S)/32-(S)/32---

    (O)-----

    (N)----(N)/28-

    ---(H2O)/18--

    (Ash)-------

    .

    Stoechiometry(C)/12(S)/32(H)/2+(H2O)/18-

    Excess of Air

    TOTAL(C)/12(S)/32(H)/2+(H2O)/18

    22.414 [(C)/12+(S)/32+(H)/2+(H2O)/18+(N)/28+3.76l S(O2)+(l-1) SO2]

    Feuil2

    Feuil3

    Feuil1

    Elements before combustionElements after combustion - Flue gases

    1 kg of fuelkmole of fuel

    (C)(C)/12 of C(C)/12(C)/12----

    (H)(H)/4--(H)/2--

    (S)(S)/32 of S(S)/32-(S)/32---

    (O)-----

    (N)----(N)/28-

    ---(H2O)/18--

    (Ash)-------

    .

    Stoechiometry(C)/12(S)/32(H)/2+(H2O)/18-

    Excess of Air

    TOTAL(C)/12(S)/32(H)/2+(H2O)/18

    22.414 [(C)/12+(S)/32+(H)/2+(H2O)/18+(N)/28+3.76l S(O2)+(l-1) SO2]

    Feuil2

    Feuil3

  • SOLID and LIQUID FUEL Flue gases compositionThe flue gases composition is usually given for a DRY SAMPLEPossible measurements Dry sample

    Production de la chaleur - Chaudire

  • GAS FUEL - Combustion accounting

    Production de la chaleur - Chaudire

    Solid+liquid

    Elements before combustionElements after combustion - Flue gases

    1 kg of fuelkmole of fuel

    (C)(C)/12 of C(C)/12(C)/12----

    (H)(H)/4--(H)/2--

    (S)(S)/32 of S(S)/32-(S)/32---

    (O)-----

    (N)----(N)/28-

    -----

    (Ash)-------

    .

    Stoechiometry(C)/12(S)/32-

    Excess of Air

    TOTAL(C)/12(S)/32

    gas

    Elements before combustionElements after combustion - Flue gases

    ---

    [CO]1/2 [CO]1/2 [CO]---

    2 [CH4]--

    --

    --

    ----

    ----

    --

    Stoechiometry-

    Excess of Air

    TOTAL

    Feuil3

  • GAS FUEL Flue gases compositionThe flue gases composition is usually given for a DRY SAMPLEPossible measurements Dry sample!

    Production de la chaleur - Chaudire

  • Objectives of those accounting tablesPractical point of viewTheoretical point of viewStackFlue Gases Analysis DevicePurgingVolume fraction onDry Flue Gases Excess of air evaluation Combustion control Heat production equipment efficiency

    Production de la chaleur - Chaudire

  • II. Heating values of fuels (Pouvoir calorifique)Combustible Elements in Fuels :C S H2 CO CH4 C2H4 C2H6 C3H8 ......Alcans : CnH2n+2Alcens : CnH2nAromatics ... Combustion :

    Production de la chaleur - Chaudire

  • Principle of Energy balance : Heating (calorific) value Pouvoir calorifique : Definition Calorimeter of MALHERFuel + AirPatm , t = 25 CAdiabatic combustion Hot flue gas CoolingCold flue gas

    At t = 25CHeat which is extracted = Heating valueCalorimeter of YOUNGERExperiment at constant VOLUMEExperiment at constant PRESSURE

    Production de la chaleur - Chaudire

  • Type of Heating value4 types 1st distinction : Constant Volume or Constant Pressure ?

    In practice CVv never used 2nd distinction :

    Flue gas at 25 CH2O Vapour Lower (Net, infrieur) CVH2O Liquid Higher (Gross, suprieur) CVIn practice:HCV USA, UK, Natural Gas LCV G,F,I,H,B, Conclusion :HCVv LCVv HCVp LCVp

    Production de la chaleur - Chaudire

  • Evaluation of Heating Values of fuelsHeating Values of Solid or Liquid Fuels Fuel composition : reference 1 kg of fuel

    Elementary composition : (C) (H) (S) (O) (H2O) (N) Heating for solid or liquid fuel :

    Production de la chaleur - Chaudire

  • Heating for gas fuel :

    Heating Values of Gas Fuels Composition of gas fuel : reference 1 m3N

    Combustible componentsInert components

    Production de la chaleur - Chaudire

  • Combustibles solidesCombustibles liquides PCI = 44000 42000 kJ/kg fractions lgres lourdesCHARBON

    BOISPCIBRUT = [1 - (cen) - (H2O)] PCIPUR & SEC - 2501 (H2O)PCIPUR & SEC = 35000 35500 kJ/kg

    PCIPUR & SEC 18500 kJ/kgsi (H2O) = 0.20PCIBRUT 14300 kJ/kg

    Production de la chaleur - ChaudireLa valeur du PCI (dit brut) dun combustible solide doit tenir compte de la chaleur dvaporation de leau (absorbe ou adsorbe) quil contient.Le bois feuillu sur pied contient environ 50% deau. Un taux dhumidit de 20% en permet la combustion dans des conditions favorables.Le pouvoir calorifique infrieur du bois est environ moiti moindre que celui du charbon.

  • Combustibles gazeux PCI = 802 400 kJ/kmole = 50 150 kJ/kg1 kmole CH4 22.414 m3N PCI = 35 800 kJ/m3N 1 kmole CH4 2 kmole H2O = 36 kg H2O PCS - PCI = 36 x 2501 = 90 036 kJ/kg PCS = 892 436 kJ/kmole = 39 816 kJ/m3N CH4

    Production de la chaleur - Chaudire

  • Examples of Evaluation 1. Liquid fuel (fuel-oil, gas-oil, gasoline, kerosene ) :Where a is the number of atoms of hydrogen per atom of carbon

    Calculate the HCV and the LCV

    Production de la chaleur - Chaudire

  • Production de la chaleur - Chaudire

  • Part 2 : Heat Production EquipmentI - ENERGY BALANCE AND EQUIPMENT EFFICIENCY1.1 Scheme of heat production equipment 1.2 Input and output of energy1.3 Efficiency and Description of LossesII - COMBUSTION CONTROL III - ILLUSTRATION3.1 Gas Burners, Oil Burners, Coal-Fired Stokers3.2 Pulverised Fuel System3.3 Multiple Fuel Burners2.4 Boilers (fire tubes, water tubes)IV - PRACTICAL PROBLEM

    Production de la chaleur - Chaudire

  • I. Energy balance and efficiency 1. Scheme of heat production equipment

    Production de la chaleur - Chaudire

  • Production de la chaleur - Chaudire

  • 2. Input and Output of Energy

    Production de la chaleur - Chaudire

  • 3. Efficiency of heat production equipment Input of Energy Output of EnergyDefinition of EfficiencyAfter calculation

    Production de la chaleur - Chaudire

  • II. Combustion control 1. Optimisation of combustion - Criteria

    Production de la chaleur - Chaudire

  • Combustion control -Diagram

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  • Combustion control -Diagram

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  • 2. Parameters controlling the combustion

    Production de la chaleur - Chaudire

  • Corrosion acideGasoil ; gaz naturelFraction molaire dans gaz brls [H2O] = 0.12 ; 0.19 = 1 [H2O] = 0.114 ; 0.181

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