Combustion Reactions and Fuel Characteristics

Energy Sources

• Air Required for Combustion: The net volume of air required for various constituents (CO, CH4, C2H4, C2H6, H) is calculated based on the stoichiometric ratio. The net air per cubic foot is 8.13.

• Stoichiometric Combustion: This is the theoretical combustion of fuel with the exact amount of oxygen to produce only CO2 and H2O as exhaust products.

• Air Composition: Air is primarily composed of oxygen (20.9%) and nitrogen (79.1%). Other trace gases are also present.

• Hydrocarbon Fuel Combustion: Complete combustion of a hydrocarbon (CnHm) produces n moles of CO2 and (m/2) moles of H2O. This reaction is critical for combustion calculations.

• Excess Air: Air is often supplied in excess of the theoretical amount needed for complete combustion.

• Combustion Reactions: Combustion is the rapid reaction of a fuel with oxygen. Significant energy is released when common fuels such as hydrocarbons or carbon react with oxygen to form carbon dioxide and water. Partial combustion occurs when CO is formed from a hydrocarbon.

• Types of Fuels: Common fuels used in combustion furnaces include coal, fuel oil, gaseous fuels (such as natural gas, methane), or liquefied petroleum gas (propane and butane).

• Combustion Products: Combustion reactions will produce CO2, H2O, and potential CO and SO2.

• Combustion in Reactors: Chemical engineers are frequently involved in the analysis of combustion reactors and their by-products, in addition to the production of heat management and control systems.

• Examples of Combustion Reactions: The document provides examples of the complete combustion of carbon, propane, and carbon disulfide, noting that partial combustion of propane results in the formation of carbon monoxide rather than carbon dioxide.

Manufactured Solid Fuels

• Charcoal: Derived from destructive distillation of wood, it burns rapidly with a clear flame and produces little to no smoke. It's used for cooking.

• Coke: A solid residue from destructive distillation of coal. Two types, soft and hard coke, differ in temperature ranges during their production. Soft coke is used as domestic fuel and burns cleanly, whereas hard coke, produced at higher temperatures, gives off smoke and is used for metallurgical processes.

• Briquettes: Made from waste material such as lignite, peat, coal, or coke dust. Good briquettes are solid, resistant to crumbling, and weather proof for storage and use.

• Bagasse: Sugarcane residue from sugar processing, serving as a quick-burning fuel. It consists of fiber, sucrose, and water, with a significant amount of moisture. Improvements are being made to reduce the percent moisture content for increased efficiency.

Hydrogen Energy

• Hydrogen Energy Generation: Major methods for producing hydrogen include use of natural gas, oil and coal, and electrolysis, with natural gas being the primary commercial method.

• Steam Reforming: Steam Reforming is a method of producing hydrogen from natural gas using steam and a Nickel catalyst at temperatures between 700-1100°C.

• Plasma Reforming: A hydrogen production method using a plasma arc to produce hydrogen from various fuel sources, including natural gas or liquified hydrocarbons. This method is designed to produce hydrogen and carbon black from fossil fuels. CO2 is not a byproduct.

• Coal Gasification: Coal gasification involves a chemical reaction of coal with oxygen and steam to produce synthesis gas, a mixture rich in carbon monoxide and hydrogen.

• Hydrogen Production from Water: Electrolysis uses an electrical current to split water into its components, hydrogen and oxygen, often using renewable energy.

Hydrogen Storage

• Physical Storage: Hydrogen can be stored as a gas under high pressure or as a liquid at cryogenic temperatures.

• Chemical Storage: Hydrogen can be chemically bonded to materials like metals (hydride storage) or stored in liquid organic carriers.

• Surface Storage: Storage of hydrogen using materials with large surface areas, including MOFs, zeolites, and carbon nanotubes, where hydrogen adsorbs onto the surface.

Biomass Energy

• Biomass: Organic materials from living organisms, including plants, animal waste, and agricultural residues (e.g., crop residues).

• Biogas Production: A renewable energy source created through the anaerobic digestion of organic matter, producing primarily methane and carbon dioxide. Plant and animal waste are typically used as feedstock.

• Biogas Uses: used for cooking fuel, electricity generation, and other purposes

Biodiesel

• Biodiesel Production: Biodiesel is made biochemically from vegetable oil or animal fat via a transesterification process, leaving glycerin as a byproduct. The methyl esters, the biodiesel product, are used in diesel engines.

• Biodiesel Sources: Various biological sources including recycled cooking oil, soybean oil, and animal fats are used to create biodiesel.

• Biodiesel Applications: Biodiesel is compatible with existing diesel engines and is considered a renewable and environmentally friendly alternative to traditional diesel fuels.