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 Mobile ViewHEATING SYSTEMS AFUE DEFINITION, RATINGS AGE of AIR CONDITIONERS & HEAT PUMPS AGE of HEATERS, BOILERS, FURNACES AIR CONDITIONING & HEAT PUMP SYSTEMS AIR FILTERS for HVAC SYSTEMS AIR HANDLER / BLOWER UNITS AIRBOUND HEAT SYSTEM REPAIRS ANODES & DIP TUBES on WATER HEATERS ANTI SCALD VALVES APPLIANCE EFFICIENCY RATINGS ASBESTOS IDENTIFICATION IN buildings BACKDRAFTING HEATING EQUIPMENT BACKFLOW PREVENTER VALVE, HEATING SYS BACKFLOW PREVENTER, HEATER WATER FEEDER BACKUP HEAT for HEAT PUMPS BAROMETRIC DAMPERS BASEBOARD HEAT BIOGAS PRODUCTION & USE BLEVE EXPLOSIONS BLOWER DOORS & AIR INFILTRATION BLOWER FAN CONTINUOUS OPERATION BLOWER FAN OPERATION & TESTING BLUE vs YELLOW COMBUSTION FLAMES BLUERAY Recall BOILERS, HEATING BOILER LEAKS CORROSION STAINS BOILER LEAKS, HOW TO LOCATE BOILER NOISE SMOKE ODORS BOILER OPERATING PROBLEMS BOILER OPERATION DETAILS BOILER PRESSURE & TEMPERATURE SETTINGS BOOKSTORE - InspectAPedia BUILDING SAFETY HAZARDS GUIDE CAPACITORS for HARD STARTING MOTORS CARBON DIOXIDE - CO2 CARBON MONOXIDE - CO CHIMNEY INSPECTION DIAGNOSIS REPAIR CHIMNEYS & Flues - Asbestos Transite Pipe CHINESE DRYWALL HAZARDS CIRCULATOR PUMPS & RELAYS COOL OFF HEAT, Thermostat Switch COMBUSTION AIR COMBUSTION PRODUCTS & IAQ COMPLETE COMBUSTION, Stoichiometric CREOSOTE FIRE HAZARDS CONDENSING BOILERS/FURNACES CONDENSING BOILERS/FURNACES DAMAGE CONVECTOR HEATERS - HYDRONIC COILS DEFINITION of Heating & Cooling Terms DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP DIAGNOSE & FIX HEATING PROBLEMS-BOILER DIAGNOSE & FIX HEATING PROBLEMS-FURNACE DIRECT VENTS / SIDE WALL VENTS DIRECTORY of OIL TANK EXPERTS DRAFT HOODS - gas fired DRAFT MEASUREMENT, CHIMNEYS & FLUES DRAFT REGULATORS, DAMPERS, BOOSTERS DUCT INSULATION, Asbestos Paper DUCT SYSTEM & DUCT DEFECTS DUCTS, Asbestos Transite Pipe DUST CONTAMINATION FROM HVAC? 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Here, courtesy of aerospace engineer Herman Vogel, we provide a definition of Stoichiometric Combustion and we explain and give formulas for Theoretical Fuel to Air Ratios for Complete Combustion (Stoichiometric Combustion). Stoichiometric Combustion discusses theoretical fuel to air ratios for hydrocarbon fuels (kerosene, jet fuel, heating oil, LP gas, etc) in which a fuel is burned completely, producing only carbon dioxide and water, with no other byproducts. Our sketch (page top) shows how an oil burner gun atomizes and sprays heating oil into the combustion chamber - Audel Oil Burner Guide InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Theoretical Fuel to Air Ratios for Complete Combustion (Stoichiometric Combustion)This website answers most questions about central heating and water heating systems to aid in troubleshooting, inspection, diagnosis, and repairs. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. Herman Vogel, Aerospace Engineer In brief: Stoichiometric combustion is by thermodynamic definition the theoretical combustion of every drop of fuel when mixed with the correct amount of air (oxygen) to yield exhaust products of only CO2 and H2O. Stoichiometric combustion is by thermodynamic definition the theoretical combustion of every drop of fuel when mixed with the correct amount of air (a basic mixture of oxygen and nitrogen gases) to yield exhaust products of only CO2 and H2O. However, such combustion is ideal and in reality doesn't occur since the burning in furnaces, automobiles and jet-engines is always incomplete and less than 100% due to engineering design limitations. Therefore while our two ideal exhaust products are relatively benign, non-stoichiometric combustion rules in the real world. This results in burning rich, as no matter how much extra air we cleverly add, it is never able to chemically react with all the fuel. Hence the resultant unburned fuel gets exposed to the high combustion temperatures and chemically reacts to form additional exhaust products of CO (Carbon Monoxide) and NO (Nitric Oxide), which can be dangerous exhaust products to both people and the environment. Stoichiometric combustion has a chemical reaction equation attached to it: C12H26(l) + 37/2 O2(g) + 2(37) N2(g) → 12 CO2(g) + 13 H2(g) + 2(37) N2(g) For the above chemical reaction to be complete, both sides of the equation (about the arrow) must have its chemical elements matched. So, if the left-side has 12 Carbon molecules, then the right-side must also have 12. Note that we are using air which contains a weighted ratio of N2/O2 = 2x37 / (37/2) = 4 (100% air = 80% N2 + 20% O2), or four times as much Nitrogen exists in a given volume of air as does Oxygen. Also, the above chemical reaction equation represents kerosene fuel which is considered a Dodecanese (liquid) hydrocarbon having the chemical formula C12H26. That means it contains a molecular composition of 12-carbon atoms and 26-hydrogen atoms and is a liquid at room temperature. Kerosene is the main constituent of Jet Propulsion (JP) fuels, where other additives include various blends of differently distilled crude oils. The fuel to air ratio by chemical weight of the above relationship is:FAR = [mf_C12H26 / ma_O2+N2] = (12*12.011+26*1.008)/(37/2*32+2*37*28.014) = 0.064 or 6.4% This says that for complete combustion of typical hydrocarbon fuels, and in particular kerosene, we need 6.4 lbs. of fuel for every 100 lbs. of air that we burn. Clearly, on a relative basis, we need a lot of air to completely burn our small amount of fuel. The beauty of the above chemical equation is that not only does it define the required fuel-to-air ratio, but it also provides us with:
Technical Note: The temperature above is in units of R (Rankin) not (F). If it were F (farenheit) we have 4,310R - 460R = 3,850F. What Does Complete Combustion (Stoichiometric Combustion) Mean to the Heating System Designer?The above three pieces of information helps the furnace designer to properly size combustion chambers and their air-fans, and to burn the correct amount of fuel to keep a home comfortable. It also helps the designer to choose the appropriate materials to avoid furnace melt-down. Note that the theoretical adiabatic flame temperature is very high. While some of this temperature is reduced due to furnace heat losses, flame temperatures are generally controlled by intentionally burning lean. This dramatically reduces the theoretical flame temperature based on the lean chemistry of combustion, plus additional temperature reductions are realized by diluting high temperatures using the extra cold air entering the combustion chamber. So, the furnace designer has a whole arsenal of possibilities to work with in designing today's reliable fuel oil furnaces. Questions & Answers regarding this articleQuestions & answers about heating oil or gas fuel combustion - perfect or stoichiometric combustion. . Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. Readers should also see these non-technical oil burner articles: and see these safety articles COMPLETE COMBUSTION, Stoichiometric
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