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IT3/HWC Baton Rouge, LA 2016 Introduction to Oxidation and Mass & Energy Balances Michael Mannuzza OBG
IT3/HWC
Baltimore2014
IT3/HWC
Baton Rouge, LA
2016
Introduction to Oxidation and
Mass & Energy BalancesMichael Mannuzza
OBG
IT3/HWC
Baltimore2014
IT3/HWC
Baton Rouge, LA
2016
Combustion
• Combustion is an oxidation reaction: Fuel + O2 ---> Products of Combustion + Heat Energy
• In addition to traditional burner fuels, incinerator fuel can include solid, gaseous and liquid waste.
• The Products of Combustion (POC) are the primary concern from an Air Pollution Control (APC) perspective.
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Air Pollutants and Regulatory Drivers
• Dioxin/Furans• Mercury (Hg)• Semi-Volatile Metals (Cd, Pb)• Low-Volatility Metals (As, Be, Cr)• SOx
• NOx• Particulate Matter• VOCs & Total Hydrocarbons• Carbon Monoxide• HCl & Cl2• Others
• The type of APC system required for an incinerator will be decided based on the system’s POCs and the regulatory limits mandated for specific pollutants.
• Emissions of the following pollutants are typically regulated for most incinerator applications:
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Identifying APC RequirementsThree Steps:1. Quantify anticipated POCs2. Identify Regulatory Emission
Constraints (establish abatement requirements)
3. Quantify the discharge flow rate of the system.
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Waste Feed PropertiesI. Begin by identifying the properties of the waste feed and
quantifying the constituency of the waste:1. Material Take-Offs2. Proximate, Ultimate, and Ash Analysis3. Sample & Analyze for Specific Compounds4. Employ Other Empirical Methods
PROXIMATE ANALYSISCategory wt %
Moisture 3.3
Ash 22.1
Volatile Matter 27.3
Fixed Carbon 47.3
Gross Calorific Value 24.73
ASH ANALYSISCategory wt %
Silicon Dioxide (SiO2) 74.1
Aluminum Oxide (Al2O3) 20.0
Iron Oxide (Fe2O3) 3.25
Calcium Oxide (CaO) 0.68
Magnesium Oxide (MgO) 0.48
Other 1.49*Ash Fusion Point = 1104 ⁰C
ULTIMATE ANALYSISCategory wt %
Carbon (C) 61.1
Hydrogen (H) 3.0
Nitrogen (N) 1.35
Sulfur (S) 0.4
Oxygen (O) 8.8
Other 25.25
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Waste Feed Properties
GASEOUS WASTE STREAMSCOMPOUND NAME % VOLUME
Methane 56.33 - 66.40Ethane 1.27 - 3.8
Propane 0.75 -1.2Butane 0.05 -1.0Octane 0.02 -.08Pentane 0.13 – 1.1Hexane 0.11 – 1.0
Carbon Monoxide 17.40 -21.0Benzene 0.00 -0.21Toluene 0.00 – 0.46
Methylene Chloride 0.01 – 0.8Water (g) 2.95-23.93
LIQUID WASTE STREAMSCOMPOUND NAME Wt. %
Toluene 8.4 -11.0Xylene 1.2 – 3.1
Propanol 1.9 -17.1Isopropylbenzene 0.08 – 9.3
Acetic Acid 0.5 – 0.91,2 Dichloroethane 1.1 – 13.1
Methanol 0.9 – 5.0Methyl Bromide 0.9 -1.5Formaldehyde 1.1 -6.7
Sodium Fluoride 1.0 – 1.5Hydrogen Chloride 4.5 – 9.5
Water (L) 21.3 – 78.42
•If possible, identifying specific compounds in the waste is the best approach.
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2016
Waste Feed PropertiesI. Waste feed rates and constituencies are rarely constant. It is
important to establish a realistic waste feed design basis. The waste feed design basis must address the following:
I. Worst case feed rateII. Highest heating value condition (kJ/kg of waste)III. Lowest heating value condition (kJ/kg of waste)IV. Worst case sulfur condition, chlorine condition, NOx condition, metals
condition, particulate condition, etc.V. Any other critical regulatory or production related criteria associated
with the waste.
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Stoichiometry of CombustionI. As a starting point, it is necessary to make some Initial
assumptions. If adequate Oxygen will be made available for complete combustion, assume the following:
I. All Carbon converts toCO2
II. All halogens convert to acids (e.g., Cl HCl, Br HBr)III. All alkali metals convert to hydroxides (e.g., Na NaOH)IV. All remaining hydrogen converts to H2OV. All non-alkali metals convert to metal oxides in their most common
oxidation state (e.g., MgO, Fe2O3)VI. Bound Nitrogen in the waste converts to NO2VII. All Sulfur converts to SO2
VIII. Non-combustible constituents pass through unchanged or thermally decompose to known compounds
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Stoichiometry of CombustionI. In reality, it is possible that additional products or congeners can
be formed.I. SO3II. Diatomic Halogens (Cl2, Br2 )III. N2, NO, N2OIV. COV. Dioxin/FuransVI. Others
II. Formation of these tertiary compounds can be a function of:I. TemperatureII. Contaminant ConcentrationsIII. O2 and H2O ConcentrationsIV. CatalystsV. Other factors
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Stoichiometry of CombustionI. The initial assumptions outlined usually provide a reasonable
estimate of the products of combustion that are generated.I. Allows the elemental contaminants to be quantified.II. Provides a mechanism for identifying combustion air requirements and
exhaust flow rates
II. The resulting POCs can then be refined if necessary by applying:I. Empirical DataII. Advanced Methods
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Stoichiometry of Combustion• Example: Dichlorobenzene, C6H4Cl2
C6H4Cl2 + ?O2 ?CO2 + ?H2O + ?HCl
C6H4Cl2 + 6.5O2 6CO2 + 1H2O + 2HCl
1. Balance Carbon atoms first2. Balance halogens, metals, Nitrogen & Sulfur next.3. Balance Hydrogen atoms4. Balance Oxygen atoms last
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Stoichiometry of Combustion
1. Balance Carbon & CO2 first:C6H4Cl2 + ?O2 ?CO2 + ?H2O + ?HCl
How many moles of CO2?Answer: 6
C6H4Cl2 + ?O2 6CO2 + ?H2O + ?HCl
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Stoichiometry of Combustion
2. Balance halogens, metals, Nitrogen & Sulfur next:C6H4Cl2 + ?O2 6CO2 + ?H2O + ?HCl
How many moles of HCl?Answer: 2
C6H4Cl2 + ?O2 6CO2 + ?H2O + 2HCl
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Stoichiometry of Combustion
3. Balance Hydrogen atoms:C6H4Cl2 + ?O2 6CO2 + ?H2O + 2HCl
How many moles of H2O?Answer: 1
C6H4Cl2 + ?O2 6CO2 + 1H2O + 2HCl
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Stoichiometry of Combustion
4. Balance Oxygen atoms last:C6H4Cl2 + ?O2 6CO2 + 1H2O + 2HCl
How many moles of O2?Answer: 6.5
C6H4Cl2 + 6.5O2 6CO2 + 1H2O + 2HCl
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Stoichiometry of Combustion – Mass Balance
Compound: C6H4Cl2 O2 CO2 H2O HClMolecular Wt. (g/mol): 147.004 32.00 44.011 18.0158 36.461
No. of Moles: 1 6.5 6 1 21Total Wt. (g): 147.004 208.00 264.066 18.0158 72.9218
2Normalized Ratio: 1 1.415 1.796 0.123 0.496
C6H4Cl2 + 6.5O2 6CO2 + 1H2O + 2HCl
1Total Wt. = (Molecular Wt.) * (No. of Moles)2Normalized Ratio = Total Wt. divided by the molecular wt of C6H4Cl2 (147.004 g/mol).
Thus: 1kg C6H4Cl2 + 1.415kg O2 1.796kg CO2 + 0.123kg H2O + 0.496 kg HClSame applies for grams, pounds or any unit other unit of mass.
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Stoichiometry CalculationsThis approach can be applied to each constituent identified in a waste stream: STEP 1: Balance the moles
STEP 2: Balance the mass
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Stoichiometry Calculations• Each constituent can be factored by its mass ratio and then summed to
generate a representative compound that reflects the properties of the overall waste stream.
• Similarly, a weighted calculation can be performed to determine the net heat of combustion of the waste stream.
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Heat of CombustionDefinitions:• Heat of Combustion: The heat released by combustion of a unit
quantity of fuel with its stoichiometrically correct amount of combustion air, measured either in calories or Btu.
• Gross Heating Value: The heat released by combustion of a unit quantity of fuel with both the combustion air and fuel at a known reference temperature prior to combustion (e.g. 60 ⁰F) after the products of combustion are allowed to cool to the initial temperature. Also known as Higher Heating Value (HHV).
• Net Heating Value: The heat release measured prior to the products of combustion being allowed to cool. Also known as Lower Heating Value (LHV).
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Heat of Combustion• For most incinerator applications, we are concerned only with the
LHV of the fuel/waste.• Numerous data sources are available (reference books, internet,
etc.).• Can be estimated or obtained through testing.
• Heat of formation• Dulong’s Approximation (Btu/lb = 14,544C+62,028(H2-0.125O2)+4,050S)
• Empirical formula based on coal.• Can be applied to other carbonaceous waste, but accuracy is questionable.
• 410 Btu (103.3 kcal) per Mole of O2 Consumed• Good approximation for hydrocarbons.• Accuracy diminishes if Oxygen, Nitrogen, Halogens and other elements are present.
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Mass & Energy BalanceMass in = Mass outEnergy in = Energy out
• Mass of waste stream constituents (solid, liquid, gas)
• Heat content of constituents• Net heat of combustion of
combustibles
• Mass of burner fuel and combustion air
• Heat content of constituents• Net heat of combustion of
burner fuel
• Mass of exhaust stream constituents (solid, gas)
• Heat content of constituents
Thermal losses
Control volume
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Mass & Energy BalanceConservation of Mass & Energymstream1 + mstream2 + mstream3 =mstream4Qstream1+Qstream2+Qstream3 =Qstream4 + Thermal Losses
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Mass & Energy Balance –Key PointsI. Mass in must equal mass out (m in – mout = 0).II. Energy in must equal energy out (Q in – Qout = 0).III. Combustion air volume will generally be a direct function of the
fuel input, however, additional air may be needed to maintain O2 levels or control temperature.
IV. Adjust the mass of the fuel input until the system energy is balanced.
I. Cannot solve directly - must be an iteration.II. The Goalseek function in Excel is useful for this approach (modulate
fuel input until Qin – Qout = 0III. Determine energy of waste gas streams by applying specific
heats.
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Mass & Energy BalanceConservation of Mass & Energymstream1 + mstream2 + mstream3 =mstream4Qstream1+Qstream2+Qstream3 =Qstream4 + Thermal Losses
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Applying Specific Heats• Q=m* Cp*DT
• Q = Heat flow (Btu/hr, MJ/hr, Watts, etc.) • m = mass flow (lb/hr, kg/hr, etc.)• Cp = Constant pressure specific heat (Btu/lb-⁰F, J/kg-⁰K, etc.)• DT = Temperature difference between actual temperature and reference
temperature (T-Tref) (⁰F, ⁰C, etc.)• Specific heat varies based on temperature and is tabulated for
commonly encountered gases in many reference books. It is also frequently presented as a polynomial function of temperature.
• Cp = a + bT +cT2
• A very accurate mean Cp can be obtained by integrating this polynomial across the temperature range.
Cpmean = ∫[a + bT +cT2]/(T-Tref) [a(T-Tref)+(1/2)b(T2-Tref2)+(1/3)c(T3-Tref
3)]/(T-Tref)
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Radiation LossesShell losses are a function of numerous variables:• Shell temperature• Wind velocity• Shell color• Shell area• Emissivity
Furnace Radiation Losses1
Furnace Rate (MBtu/hr) Radiation Losses (%)
<10 3
15 2.75
20 2.5
25 2
30 1.75
>35 1.5
1Handbook of Incineration Systems, Brunner, C. R., 1991 McGraw-Hill
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Mass & Energy BalanceConservation of Mass & Energymstream1 + mstream2 + mstream3 =mstream4Qstream1+Qstream2+Qstream3 =Qstream4 + Thermal Losses
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Converting Mass to Volume• When calculating process emissions, we routinely need to convert
between mass & volume.• Avogadro’s Law: Equal volumes of all gases under the same
conditions of temperature and pressure contain the same number of molecules.
• Definitions & Conversions:• lb-mol = mass (lbs) ÷ MW• 1 lb-mol = 386.728 ft3 @ 70 ⁰F and 14.6959 psi
• g-mol = mass (grams) ÷ MW• 1 g-mol = 22.414 L @ 0 ⁰C and 760 mm Hg
• ppmv = 106 * Volume of Component ÷ Overall Volume
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Converting Mass to Volume• Volume is temperature & pressure dependent. It is common to
normalize volume to a standard temperature, to facilitate mass/volume conversions
• Nm3/hr & m3/hr• m3/hr = Nm3/hr * (273 + T)/(273 +Tref)• T = Process Temp. (⁰C)• Tref = Reference Temp. (⁰C) usually 0 ⁰C
• SCFM & ACFM• ACFM = SCFM *(460+ T)/(460 +Tref)• T = Process Temp. (⁰F)• Tref = Reference Temp. (⁰F)
• Be aware, different reference temps are used for SCFM• 60 ⁰F, 68 ⁰F, 70⁰F
• Nm3/hr * 0.6341 = SCFM (@ 70 ⁰F)
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Converting Mass to VolumeI. Volume is also effected by pressure, including pressure
due to elevation changes:I. SCFM is referenced to standard atmospheric pressure at sea -
level = 14.6959 psi (406.8 inches H2O)II. Nm3/hr is referenced to 760 mm Hg.III. When pressure effects must be accounted for:
I. ACFM =SCFM *(406.8/ Pactual)*(460+T)/530II. m3/hr = Nm3/hr * (760/Pactual)*(273+T)/273
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Combustion AirComposition of Dry Atmospheric AirGas VolumeNitrogen 78.084%Oxygen 20.946%Argon 0.9340%Carbon Dioxide 0.0397%Neon 0.001818%Helium 0.000524%Methane 0.000179%
Typical C.A. Constituency (Assumed) % Weight % Volume
Nitrogen 76.85 79.1Oxygen 23.15 20.9
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Excess Air• Excess Air: The air remaining after a fuel has been completely
burned or that air supplied in addition to the amount required for stoichiometric combustion.
• Increased O2 content can enhance combustion, or it can lead to the formation of problematic compounds (i.e., SO3, CO2, NO2)
• Excess air may be required to control exothermic temperature rise or flammability levels.
• Regulatory emission limits are typically referenced to a specific O2level and a correction factor must frequently be applied to actual data.
ppmvcorrected = ppmvtest * [21-%O2base]/[21-O2test]
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Particulate Matter• Particulate Matter (PM) can be solid, or liquid aerosol.
• Can include condensables• Particle Size Distribution (PSD) is important.
• Will drive APC Technology Selection• Determined by source testing.
• Units for PM• Micrograms per dry cubic meter (μg/m3)• Grains per standard cubic ft ( gr/scf).
• 7,000 gr = 1 lb• Measurements are dry basis
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QUESTIONS?
