MSW (Municipal Solid Waste Incinerator) Definition :

MSW (Municipal Solid Waste Incinerator) • Definition : • Combustion - a process of burning, resulting from the rapid oxidation of substances • Used for municipal solid wastes, industrial (hazardous) waste, sludges, fossil fuel • Typically operated with excess air (oxygen supply > combustion stoichiometry) • Advantages : • Volume and weight reduced (approx. 90% volume and 75% weight reduction). • Waste reduction is immediate, no long term residency required. • Destruction in seconds. • Incineration can be done at generation site (ex. medical waste incinerators). • Air discharges can be controlled (low health risk). • Small disposal area required. • Cost can be offset by heat recovery/ sale of energy. • Disadvantages : • High capital cost. • Skilled operators are required (particularly for boiler operations). • Not all material are incinerable (noncombustable solids). • Some material require supplemental fue.l • Public disapproval. • Risk imposed rather than voluntary. • Incineration will decrease property value. • Distrust of government/industry ability to regulate.

Energy Consumption

Gasoline • Petroleum (crude oil) • Thousands of organic compounds, mostly alkanes • Tb / oC • CnH2n + 2 methane CH4 -164 • ethane C2H6 H3C-CH3 -89 • propane C3H8 H3C-CH2-CH3 -42 • butane C4H10 H3C-(CH2)2-CH3 -0.5 • pentane C5H12 H3C-(CH2)3-CH3 36 • hexane C6H14 H3C-(CH2)4-CH3 69 • heptane C7H16 H3C-(CH2)5-CH3 98 • Octane C8H18 H3C-(CH2)6-CH3 126

Other compounds in petroleum (and gasoline) Cyclic hydrocarbons (cycloalkanes) Cyclohexane (C6H12) Aromatic hydrocarbons Benzene Toluene p-Xylene BTX (or BTEX)

Total moles of products = 1+2+7.52 moles = 10.52 moles Mole % of CO2 = 1/10.52x100(%) = 9.5%-vol CO2 =9.5x104 ppm CO2 Mole % of H2O = 2/10.52x100(%) = 19%-vol H2O Mole % of N2 = 7.52/10.52x100(%) = 71.5%-vol N2

Air-Fuel Ratio (공연비) • Composition of air-fuel mixture may also be expressed in terms of % excess air, % theoretical air,γand equivalence ratio, φ. • Air-Fuel Ratio (AF) = mair/mfuel • Theoretical or stoichiometric AF ratio : [mair/mfuel]stoich • % theoretical air = Air-Fuel Ratio (AF)/ stoichiometric AF ratiox100 (%) • 공기비(과잉공기계수)= Air-Fuel Ratio (AF)/ stoichiometric AF ratio • % excess air = % theoretical air -100% • % theoretical air,γ=1/φ • mfuel/mair • Equivalence ratio, φ = --------------- • [mfuel/mair]stoich • φ<1 indicates that excess air is present. : Fuel-lean combustion • φ>1 indicates that too little air is present for complete combustion. : Fuel-rich combustion • φ=1 indicates that the stoichiometric amount of air is present. : stoichiometric combustion

Balancing the stoichiometric equation, Air-fuel ratio : example • C8H18 + 20(O2 + 3.76N2) → aCO2+bH2O+cO2+dN2 • Determine the AF ratio, the %theoretical air, the %excess air, and equivalence ratio. • AF= [(20*4.76 kmol Air)(28.97 kg/kmol Air)] /[(1 kmol C8H18)(114.24 kg/kmol C8H18)] = 24.1

C8H18 + 12.5(O2 + 3.76N2) → 8CO2+9H2O+cO2+94N2 • stoichiometric AF= [(12.5*4.76 kmol Air)(28.97 kg/kmol Air)] /[(1 kmol C8H18)(114.24 kg/kmol C8H18)] = 15.1 • % theoretical air = 24.1/15.1x100=160% • % excess air = 160-100=60% • Equivalence ratio = (1/24.1)/(1/15.1)=0.63 (Fuel-lean condition)

Example: 2-5(p. 34) Excess air=30%, (70%의 상대습도, air)에서 75kg/hr의 waste를 소각하고 Waste 성분 분석은 다음과 같다. Waste 성분 분석(Ultimate Analysis:원소분석) : (100kg 기준시) C : 71%  71kg  5.912kgmoles H : 9.2%  9.2kg  9.2kgmoles O : 2.1%  2.1kg  0.132kgmoles S : 3.4%  3.4kg  0.106kgmoles N : 0.6%  0.6kg  0.042kgmoles H2O : 12.2%  12.2kg Ash : 1.5%  1.5kg 그러므로 waste의 분자식은 C5.912H9.2O0.132S0.106N0.042 이론적 공기량을x(O2+3.78N2) 라 두면, C5.912H9.2O0.132S0.106N0.042+(1+ 0.3)x(O2+3.78N2)  5.912CO2+4.6H2O+0.106SO2+0.3xO2+[0.021+(1.3x)3.78]N2 O2를 기준 : + 1.3x=5.912+2.3+0.106+0.3x  x=8.234 C5.912H9.2O0.132S0.106N0.042+(1+0.3)(8.234)(O2+3.78N2)  5.912CO2+4.6H2O+0.106SO2+2.47O2+40.483N2

(9) Moles nitrogen in stoichiometric air 8.234  3.78 = 30.975 (10) Moles nitrogen in excess air = (0.3)(8.234x3.78)=(0.3)(30.975) = 9.293 (11) Moles oxygen in excess air = (0.3)(8.234) = 2.470 (12) Moles moistures in combustion air (psychrometric chart를 이용) 70%의 상대습도  0.008kg H2O/kg of dry air  (10.704  32 + 10.704  3.78 28)kg air = 0.653kgmoles (13) Total moles : CO2 = 5.912, H2O = 4.6 + 0.653 = 5.894, SO2 = 0.106 O2 = 2.47, N2 = 40.483, Total = 54.671 1.3x8.234

Example 2-6 : Orsat Analysis CO2 : 12.3%  12.3 kgmoles 100 kgmoles 기준 O2 : 5.1%  5.1 kgmoles N2 = 100 – (12.3+5.1) = 82.6% C12.3Hy+(x+5.1)(O2+3.76N2) 12.3CO2+5.1O2+82.6N2+ H2O for N2 : 3.76x+(5.1)(3.76) = 82.6 x = 16.9 for O2 : (16.9 + 5.1) = 12.3 + 5.1 + y = 18.4 fuel(waste)의 화학식 : C12.3H18.4 Weight ratio of H to C = = 0.125 Weight % of H = = 11.1% Weight % of C = = 88.9%

Air requirement; = (16.9 + 5.1)(32+3.78  28) = 3020.2 kg air/100kgmoles of fuel or = (18.2/100)kg air/kg of fuel Excess air:  100 = 30.2% Exhaust Gas: Total moles = 12.3 + 5.1 + 82.6 + = 109.2kgmoles/100kgmoles of fuel

(기체 연료의 이론 공기량) 기체연료 1Sm3중에 H2, CO, CH4, C2H4, C3H8, C4H10,‥‥, CxHy, O2, CO2가 각각 %(volume비)씩 들어 있는 경우 이론공기량, Ao는 단위: Sm3/Sm3 (ex) 분자식 CmHn인 탄화수소가스 1Sm3의 연소시 필요한 이론 공기량은? Sm3/Sm3 Sm3/Sm3

여기서 C, H, O, S는 중량비(wt%)임. or, (액체 및 고체연료의 경우) 이론 공기량: Sm3/kg or Kg/kg 단위는 Sm3/kg 이다. or, 단위는 kg/kg 이다.

(ex) 탄소 85%, 수소13%, 황2%의 조성을 가진 중유의 이론 공기량은? (ex) 탄소, 수소, 산소, 황의 중량%가 86.6%, 4%, 8%, 1.4%인 중유의 연소에 필요한 이론산소량(Sm3/kg)과 이론 공기량(Sm3/kg)을 계산하라. 이론 산소량 이론 공기량

(ex) 메탄올(CH3OH) 1kg이 연소하는데 필요한 이론 공기량을 Sm3/kg과 kg/kg으로 구하라.

*CH3OH(메탄올) 1kg연소시의 이론 공기량은? 이론 공기량

(ex) 탄소 85%, 수소13%, 황2%의 조성을 가진 중유의 이론 공기량은? 이론 공기량 (Sm3/kg)

*이론 산소량 or, 이론 공기량 (kg/kg)

연소가스의 조성비가 N2, O2, CO로 구성 여기서, N2=100-{(CO2)+(O2)+(CO)} Excess Air(과잉공기) m=공기비(과잉공기계수)=A/Ao=실제공기량/이론공기량=m•(Ao) 과잉공기비율=(A-Ao)/Ao=m-1 과잉공기량=(m-1)Ao (ex)탄소, 수소의 중량 조성이 각각 86%, 14%인 액체 연료를 매시 100kg 연소한 경우 배기가스의 분석치는 다음과 같다. CO2:12.5%, O2:3.5%, N2:84% 이 경우에 매시 필요한 공기량(Sm3/h)은? 이론 공기량, Ao 공기비(과잉공기계수), 실제 공기량=(1.19)(11.38Sm3/kg=13.54Sm3/kg 100kg 연소시 실제 공기량=13.54100=1354Sm3/h

100 Kg Kgmole C 86 Kg 86/12 = 7.167 H 14 Kg 14/1 = 14 → C7.167H14 * 100 Kg/h 의 연료성분 C = 86%, H = 14%

MSW (Municipal Solid Waste Incinerator) Definition :