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Questions and Answers
What was the total delay of oil production due to Hurricane Ida?
In the Climate Change Opinion Map, what percentage of people believed global warming is happening in 2021?
What is combustion?
Conversion of chemical energy to thermal energy.
What does the emissions index measure?
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The adiabatic flame temperature is the highest temperature that can be achieved by a given mixture of ______ taken to equilibrium under adiabatic conditions.
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What is defined as the higher heating value (HHV)?
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In the example of iso-octane combustion, what is the main greenhouse gas emitted?
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Thermal NOx is created at low temperatures.
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What is the significance of the equivalence ratio in combustion?
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Match the following types of NOx with their characteristics:
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Study Notes
Hurricane Ida’s Impact on Oil and Gas Production
- Hurricane Ida caused a significant reduction in oil and gas production in the Gulf of Mexico.
- Before the storm, production was at 1.8 million barrels of oil and 2.2 billion cubic feet of gas per day.
- After the storm, oil production dropped to 300,000 barrels per day, representing a total delay of 20 million barrels of oil.
- An underwater pipeline was also reported to be leaking.
Public Opinion on Climate Change
- In 2018 and 2021, a majority of Americans (70% and 72%, respectively) believed that global warming is happening.
- Fewer Americans (41% and 47%) believed that climate change would personally impact them.
- Around 35% of Americans regularly discuss climate change.
- A majority of Americans (68% and 70%) believe that corporations should do more to address climate change.
Introduction to Combustion
- Combustion is a primary source of power globally, accounting for over 80% of energy production.
- Combustion processes utilize various fuels, including coal, natural gas, and oil.
- Fuels can be in liquid, solid, or gaseous states.
- Mixing of fuel and oxidizer can be premixed or non-premixed (diffusion flames).
- The ratio of fuel to oxidizer is crucial, and key terms include stoichiometry, equivalence ratio, and percent theoretical air.
Combustion Chemistry
- Combustion is the conversion of chemical energy to thermal energy.
- Chemical models are essential to represent the process.
- Combustion chemistry is modeled through global reactions or detailed/elementary reactions.
Global Reactions
- Global reactions simplify the process, representing it as a single step.
- Global reactions provide a basic understanding of the products of combustion but do not provide information on intermediate species.
Complete Combustion
- Complete combustion assumes no excess oxygen, resulting in all hydrogen being converted to water, all carbon to carbon dioxide, and nitrogen remaining as nitrogen.
- Complete combustion corresponds to 0% excess air, 100% theoretical air, stoichiometric conditions, and an equivalence ratio of 1.0.
Working with Mixtures
- Mole and mass fractions are used to define the composition of mixtures.
- Molecular weights are used to convert between mass and mole fractions.
Equivalence Ratio
- The equivalence ratio compares the fuel-to-air ratio of a combustion process to the stoichiometric combustion process.
- Different calculations are required for lean and rich conditions.
Emissions Index
- The emissions index measures emissions intensity relative to the fuel burned.
- It can be used to determine the amount of carbon dioxide emitted from carbon-based fuels.
Enthalpy of Combustion
- Enthalpy of combustion represents the energy released during combustion, also known as heat of combustion, heating value, or ∆hc.
- Enthalpy of combustion can be calculated theoretically or measured experimentally using a calorimeter.
- Higher heating value (HHV) accounts for the heat of vaporization of water, while the lower heating value (LHV) assumes water vapor in the products.
Adiabatic Flame Temperature
- The adiabatic flame temperature (Tad) refers to the highest temperature attainable by a mixture under adiabatic conditions (no heat loss) in equilibrium.
- Tad depends on the equivalence ratio, with dilution by nitrogen lowering Tad for lean mixtures and incomplete combustion lowering it for rich mixtures.
- Tad increases with pressure due to radical recombination reactions.
Effects of Equivalence Ratio on Combustion Products
- Major combustion products include oxygen, nitrogen, water, and carbon dioxide for fuel-lean conditions.
- For fuel-rich conditions, major products include nitrogen, water, carbon dioxide, carbon monoxide, and hydrogen.
- At an equivalence ratio of 1.0, some CO, O2, and H2 are still produced due to the balance of Tad, specific heat, and dissociation.
Effects of Equivalence Ratio on Minor Products
- Hydroxyl radical (OH) indicates the hottest region in the combustion chamber and peaks near maximum Tad.
- Nitric oxide (NO) peaks at an equivalence ratio of 0.8.
- NO levels are high (thousands of ppm) compared to regulatory limits (around 10 ppm).
- Trade-offs exist between CO and NO, and between soot and NOx.
NOx Emissions
- Three primary NOx formation mechanisms exist: thermal NOx, prompt NOx, and fuel NOx.
- Thermal NOx is formed at high temperatures and is the primary cause of combustion-generated NOx.
- Prompt NOx is associated with fuel-rich conditions and is less temperature-dependent than thermal NOx.
- Fuel NOx arises from nitrogen chemically bound within the fuel structure, primarily a concern for coal and propellants.
Thermal NOx Mechanism
- Thermal NO formation is governed by the Zeldovich mechanism, which involves a series of reactions with nitrogen, oxygen, and oxygen atoms.
- Reaction rates are highly sensitive to temperature, with the rate-limiting step involving a high activation energy.
Prompt NOx Formation
- Prompt NOx arises from super-equilibrium concentrations of O and OH, cyanogen kinetics (HCN), and nitrous oxide (N2O) formation.
Fuel NOx Formation
- Fuel NOx is formed when fuels contain nitrogen, primarily a concern for coal and propellants.
- Coal contains a significant amount of nitrogen, while some crude oils and propellants also contain nitrogen.
Adiabatic Flame Temperature (Tad)
- Tad represents the highest temperature attainable under adiabatic conditions.
- Preheat temperature linearly increases Tad.
Thermal NOx Formation: The Zeldovich Mechanism
- The Zeldovich mechanism involves three reactions: N2 + O → NO + N, N + O2 → NO + O, and N + OH ↔ NO + H.
- The first reaction, N2 + O → NO + N, has a high activation energy and is rate-limiting.
- Oxygen atoms originate from chain-branching reactions during combustion.
Thermal NOx Reaction Rate
- The rate of NO production is highly temperature-sensitive due to the rate coefficient of the first Zeldovich reaction, kN1.
- Equilibrium models tend to underestimate NO production due to neglecting super-equilibrium oxygen in combustion gases.
Prompt NOx Sources
- Prompt NOx has three main sources: super-equilibrium O and OH, cyanogen kinetics (HCN), and nitrous oxide (N2O) kinetics.
- Prompt NOx is linked to fuel-rich conditions and is less temperature-dependent than thermal NOx.
Fuel NOx: Fuel-Bound Nitrogen
- Fuel NOx arises from nitrogen chemically bound within the fuel structure.
- This mechanism is especially relevant for fuels like coal and propellants.
- Coal contains a significant amount of nitrogen, while some crude oils and propellants also contain trace impurities of nitrogen.
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Description
Explore the significant impacts of Hurricane Ida on oil and gas production, as well as public opinions on climate change in the U.S. This quiz covers the effects of the storm on energy resources and the perception of climate issues across different years. Test your knowledge on these critical environmental topics!
