🔬 Unit 4 – Part B (13-Mark Q&A)

1. i) How fuels are classified. Give examples for each of them. ii) What is meant by proximate analysis of coal? What are the quantities estimated in this analysis and their significance.

i) Classification of Fuels

Fuels are substances that release energy, usually heat, upon controlled chemical reaction (like combustion). They are primarily classified based on their physical state and occurrence.

1. Based on Physical State:
   • Solid Fuels: Fuels existing in the solid state at room temperature.
     • Examples: Wood, Coal (Peat, Lignite, Bituminous, Anthracite), Coke, Charcoal, Agricultural waste (biomass).
   • Liquid Fuels: Fuels existing in the liquid state at room temperature.
     • Examples: Petroleum (Crude Oil) and its fractions (Gasoline/Petrol, Kerosene, Diesel, Fuel Oil), Alcohols (Ethanol, Methanol), Biodiesel.
   • Gaseous Fuels: Fuels existing in the gaseous state at room temperature.
     • Examples: Natural Gas (mainly methane), Liquefied Petroleum Gas (LPG - propane, butane), Coal Gas, Producer Gas, Biogas, Hydrogen.
2. Based on Occurrence:
   • Primary (Natural) Fuels: Found directly in nature.
     • Examples: Wood, Coal, Petroleum, Natural Gas.
   • Secondary (Artificial/Derived) Fuels: Processed or derived from primary fuels.
     • Examples: Coke (from coal), Charcoal (from wood), Gasoline, Diesel (from petroleum), Coal Gas, Producer Gas (from coal/coke), Ethanol (from biomass fermentation).

ii) Proximate Analysis of Coal

Proximate analysis is an empirical method used to determine the percentage composition of coal in terms of four key components. It provides a quick assessment of coal quality and suitability for various applications.

Quantities Estimated:

1. Moisture Content:
   • Procedure: A known weight of powdered, air-dried coal sample is heated in an oven at 105-110°C for about an hour. The loss in weight is reported as the percentage of moisture.
   • Significance: High moisture content reduces the calorific value (as heat is wasted in evaporating water), increases transportation costs, and can cause issues in handling and storage.
2. Volatile Matter (VM):
   • Procedure: The moisture-free coal sample is heated in a covered crucible at 925 ± 20°C for exactly 7 minutes. The loss in weight (after accounting for moisture) is reported as the percentage of volatile matter.
   • Significance: VM consists of combustible gases (like H₂, CH₄, CO) and non-combustible gases (like CO₂, N₂) driven off during heating. High VM coals ignite easily, burn with a long, smoky flame, and have lower calorific values. Low VM coals burn with shorter flames and are preferred for making metallurgical coke.
3. Ash Content:
   • Procedure: The residual coal sample (after moisture and VM determination) is heated uncovered in a muffle furnace at 700-750°C until constant weight is achieved. The weight of the residue is reported as the percentage of ash.
   • Significance: Ash is the non-combustible inorganic residue left after complete combustion. High ash content reduces calorific value, increases handling/disposal costs, causes clinker formation, and reduces boiler efficiency.
4. Fixed Carbon (FC):
   • Procedure: It is not determined directly but calculated by difference:
     % Fixed Carbon = 100 - (% Moisture + % Volatile Matter + % Ash)
   • Significance: Fixed carbon represents the main combustible part of the coal that burns in the solid state on the furnace grate. Higher fixed carbon generally indicates higher rank and higher calorific value.

2. i) Give a detailed procedure of determination of various elements present in coal. (ultimate analysis).

Ultimate Analysis of Coal

Ultimate analysis determines the elemental composition of coal, typically reporting the percentages of Carbon (C), Hydrogen (H), Nitrogen (N), Sulfur (S), Ash, and Oxygen (O - usually calculated by difference). It provides a more fundamental understanding of coal composition than proximate analysis and is essential for combustion calculations.

Procedure for Determination:

1. Carbon (C) and Hydrogen (H):
   • Method: A known weight of coal sample is burnt completely in a current of pure oxygen in a combustion apparatus.
   • Reactions:
     C + O₂ → CO₂
     H₂ + ½ O₂ → H₂O
   • Absorption: The gaseous products (CO₂ and H₂O vapor) are passed through pre-weighed absorption tubes. H₂O is absorbed by anhydrous Calcium Chloride (CaCl₂) or Magnesium Perchlorate (Mg(ClO₄)₂), and CO₂ is absorbed by Potassium Hydroxide (KOH) solution.
   • Calculation: The increase in weight of the CaCl₂ tube gives the weight of H₂O formed, and the increase in weight of the KOH tube gives the weight of CO₂ formed.
     % H = (Increase in wt. of CaCl₂ tube / Wt. of coal sample) × (2/18) × 100
     % C = (Increase in wt. of KOH tube / Wt. of coal sample) × (12/44) × 100
   • Correction: Hydrogen percentage must be corrected if the coal contains mineral moisture that wasn't removed.
2. Nitrogen (N):
   • Method: Kjeldahl's method is commonly used. A known weight of coal is heated with concentrated sulfuric acid (H₂SO₄) in the presence of catalysts (like K₂SO₄ and CuSO₄).
   • Conversion: Nitrogen in the coal is converted into Ammonium Sulfate ((NH₄)₂SO₄).
   • Liberation & Titration: The resulting solution is treated with excess Sodium Hydroxide (NaOH) solution to liberate Ammonia (NH₃) gas, which is absorbed in a known volume of standard acid (like H₂SO₄). The unreacted acid is then back-titrated with standard alkali (like NaOH).
   • Calculation: From the volume of acid consumed by ammonia, the percentage of nitrogen is calculated.
3. Sulfur (S):
   • Method: A known weight of coal is burnt completely (often in a bomb calorimeter during calorific value determination or using Eschka mixture).
   • Conversion: Sulfur is converted into sulfate ions (SO₄^2-), usually by treating the combustion residue/washings with oxidizing agents and then acidifying.
   • Precipitation: Barium Chloride (BaCl₂) solution is added to precipitate sulfur as Barium Sulfate (BaSO₄).
   • Calculation: The BaSO₄ precipitate is filtered, washed, dried, and weighed. From the weight of BaSO₄, the percentage of sulfur is calculated.
     % S = (Wt. of BaSO₄ obtained / Wt. of coal sample) × (32/233) × 100
4. Ash:
   • Method: Determined as described in the proximate analysis (heating the coal sample in a muffle furnace at 700-750°C until constant weight).
   • Calculation: % Ash = (Weight of residue / Weight of coal sample) × 100
5. Oxygen (O):
   • Method: Calculated by difference, assuming the coal only contains C, H, N, S, Ash, and O.
   • Calculation:
     % Oxygen = 100 - (%C + %H + %N + %S + %Ash)
   • Note: This method includes experimental errors from all other determinations. Direct determination methods exist but are more complex.

3. (i) How power alcohol can be helpful in fuel crisis. (ii) Write a short note about biodiesel and its synthesis.

i) Power Alcohol and Fuel Crisis

Power alcohol refers primarily to ethyl alcohol (ethanol, C₂H₅OH) used as a fuel, particularly as an additive or replacement for gasoline (petrol).

Helpfulness in Fuel Crisis:

• Renewable Source: Ethanol is produced by fermenting biomass rich in sugars or starches (e.g., sugarcane, corn, molasses, cellulosic materials). Unlike fossil fuels (petrol, diesel) which are finite, biomass is renewable, reducing reliance on depleting resources.
• Energy Security: Domestic production of ethanol can reduce a country's dependence on imported crude oil, enhancing energy security and reducing vulnerability to global oil price fluctuations and supply disruptions.
• Reduced Emissions: Ethanol is an oxygenated fuel, meaning it contains oxygen. Blending it with gasoline promotes more complete combustion, potentially reducing carbon monoxide (CO) and unburnt hydrocarbon emissions. While CO₂ is produced, the biomass source absorbs CO₂ during growth, making it closer to carbon-neutral in its lifecycle (though land use changes and production energy must be considered).
• Octane Booster: Ethanol has a high octane rating, which helps prevent engine knocking. Blending it with gasoline can increase the overall octane number of the fuel.
• Agricultural Support: Production of ethanol from crops can provide an additional market for agricultural products, supporting rural economies.

Limitations: Lower energy density than gasoline (requires more volume for the same energy), potential competition with food crops for land, energy-intensive production process, and compatibility issues with older engines/fuel systems.

ii) Biodiesel and its Synthesis

Biodiesel is a renewable, biodegradable fuel chemically similar to petroleum diesel. It consists of fatty acid methyl or ethyl esters (FAMEs or FAEEs).

Sources: It is typically derived from vegetable oils (soybean, rapeseed/canola, palm, sunflower), animal fats, or used cooking oil.

Synthesis (Transesterification):

• Process: The primary method for producing biodiesel is transesterification. This involves reacting the triglycerides (the main component of oils and fats) with a short-chain alcohol (usually methanol, sometimes ethanol) in the presence of a catalyst (typically a strong base like NaOH or KOH, or sometimes an acid or enzyme).
• Reaction: The triglyceride molecule is broken down, and its three fatty acid chains react with three molecules of alcohol to form three molecules of fatty acid alkyl esters (biodiesel) and one molecule of glycerol (glycerin) as a byproduct.
  Triglyceride + 3 Methanol \( \xrightarrow{\text{Catalyst}} \) 3 Methyl Esters (Biodiesel) + Glycerol
  
• Separation: After the reaction, the heavier glycerol settles at the bottom and is separated from the lighter biodiesel layer.
• Purification: The raw biodiesel is then purified by washing (to remove catalyst, soap, excess alcohol) and drying.

Properties & Use: Biodiesel has properties similar to petroleum diesel and can be used in most diesel engines, either in pure form (B100) or blended with petroleum diesel (e.g., B5, B20 - indicating 5% or 20% biodiesel). It generally has better lubricity but slightly lower energy content and potentially poorer cold-weather performance than petroleum diesel. It significantly reduces particulate matter, hydrocarbon, and carbon monoxide emissions but can slightly increase NOx emissions.

4. i) Describe the synthesis of Gasoline by Bergius process. ii) Define HCV and LCV. Calculate the Net and Gross calorific value of coal having the following composition. C=85%, H=8% , S=1%, N=2% and rest being ash. Latent heat of steam=587 Cal/g.

i) Synthesis of Gasoline by Bergius Process

The Bergius process is a method for producing synthetic liquid hydrocarbons (including gasoline) by the direct hydrogenation of coal at high temperature and pressure.

Process Steps:

1. Coal Preparation: Low-rank coal (like lignite or bituminous) is finely ground and mixed with heavy oil (recycled from the process) to form a paste. A catalyst (typically based on iron or tin compounds) is added.
2. Hydrogenation: The coal paste is pumped into a high-pressure reactor along with hydrogen gas (H₂). The reaction occurs at high temperatures (around 400-500°C) and very high pressures (around 200-700 atmospheres or 20-70 MPa).
3. Reaction: Under these conditions, the complex structure of coal is broken down, and hydrogen atoms are added (hydrogenation). This converts the solid coal into a mixture of liquid hydrocarbons (synthetic crude oil or "syncrude"), gases, and unreacted solids/ash.
   nC + (n+1)H₂ → C_nH_2n+2 (Simplified representation)
4. Separation: The products leaving the reactor are cooled and separated. Unreacted hydrogen and light hydrocarbon gases are typically recycled. The heavy liquid fraction containing unreacted coal and ash is separated (often using centrifuges or filters), and some of this heavy oil is recycled to make the initial coal paste.
5. Upgrading/Refining: The primary liquid product (syncrude) is then further processed using conventional refinery techniques like distillation and hydrocracking to produce various fractions, including synthetic gasoline, diesel, and other liquid fuels.

Significance: Historically important, especially in countries lacking petroleum reserves but having abundant coal (e.g., Germany during WWII). It allows the conversion of solid coal into valuable liquid fuels. However, it is an energy-intensive process with significant environmental impacts (high CO₂ emissions).

ii) HCV, LCV, and Calculation

Definitions:

• Higher Calorific Value (HCV) / Gross Calorific Value (GCV): The total heat released when a unit mass/volume of fuel is completely burnt, and the products of combustion are cooled to the initial temperature (usually room temperature). This includes the latent heat recovered from the condensation of water vapor formed during combustion (mainly from hydrogen in the fuel).
• Lower Calorific Value (LCV) / Net Calorific Value (NCV): The heat released when a unit mass/volume of fuel is completely burnt, and the products of combustion are allowed to escape without being cooled sufficiently to condense the water vapor. This value excludes the latent heat of vaporization of water. In practical applications like boilers, the flue gases usually escape at high temperatures, so LCV is often more relevant.

Relationship: HCV = LCV + Latent heat of water vapor formed

Calculation:

Given composition: C = 85%, H = 8%, S = 1%, N = 2%. Rest is Ash.

Ash = 100 - (85 + 8 + 1 + 2) = 100 - 96 = 4%.

Oxygen is assumed to be 0% as it's not given and elements sum to 96% before Ash.

We use Dulong's Formula to estimate the HCV (in Cal/g or kcal/kg):

(Assuming Oxygen %O = 0)

Now, calculate the LCV. The heat lost due to water vapor is primarily from the hydrogen content. Combustion of H forms H₂O. (Molecular weights: H₂=2, O=16, H₂O=18)

1 part by mass of H gives 9 parts by mass of H₂O (since 2g H yields 18g H₂O).

Mass of water formed from 1g of coal = (9 × %H / 100) = (9 × 8 / 100) = 0.72 g.

Latent heat of steam = 587 Cal/g.

Heat lost as latent heat per gram of coal = Mass of water × Latent heat = 0.72 × 587 = 422.64 Cal/g.

(A common simplified formula incorporates this directly):

Final Answer:
Gross Calorific Value (HCV) ≈ 9650.4 Cal/g
Net Calorific Value (LCV) ≈ 9227.76 Cal/g

5. Explain the following (i) Ignition temperature (ii) spontaneous ignition temperature, (iii) Explosive range

i) Ignition Temperature

The ignition temperature is the minimum temperature to which a fuel must be heated in the presence of an oxidant (usually air or oxygen) to initiate combustion that continues even after the external heat source is removed. It represents the point where the rate of heat generation by the oxidation reaction exceeds the rate of heat loss to the surroundings, leading to a self-sustaining flame or glow.

• It depends on factors like fuel type, pressure, presence of catalysts, and surface area (for solids).
• For combustion to start, the fuel needs to reach this temperature AND have an ignition source (like a spark or flame), unless it reaches the *spontaneous* ignition temperature.

ii) Spontaneous Ignition Temperature (Autoignition Temperature)

The spontaneous ignition temperature (or autoignition temperature) is the lowest temperature at which a substance will ignite and burn in a normal atmosphere *without* an external ignition source (like a spark or flame). The heat required is supplied solely by the surrounding environment.

• At this temperature, the rate of slow oxidation reactions within the fuel-air mixture becomes rapid enough to generate sufficient heat to initiate combustion spontaneously.
• This property is particularly important for safety considerations when handling flammable materials and is crucial for the operation of diesel engines (where fuel ignites due to the heat of compression).
• It is generally higher than the flash point and fire point of a liquid fuel.

iii) Explosive Range (Flammability Limits)

The explosive range (or flammability limits) defines the concentration range of a flammable gas or vapor in air (or another oxidant) within which an explosion or fire can occur if an ignition source is present. It is expressed as a percentage by volume and has two limits:

• Lower Explosive Limit (LEL) / Lower Flammability Limit (LFL): The minimum concentration of fuel in the air below which the mixture is too "lean" (not enough fuel) to ignite or propagate a flame.
• Upper Explosive Limit (UEL) / Upper Flammability Limit (UFL): The maximum concentration of fuel in the air above which the mixture is too "rich" (not enough oxygen) to ignite or propagate a flame.

A mixture will only ignite if its concentration falls between the LEL and UEL. Mixtures outside this range are considered non-flammable under normal conditions. This range varies significantly for different substances (e.g., hydrogen has a very wide explosive range: 4% to 75% in air).

6. What is meant by knocking and describe octane number and cetane number.

Knocking

Knocking is an undesirable phenomenon occurring in internal combustion engines, characterized by sharp metallic pinging or knocking sounds. The cause differs between engine types:

• In Spark-Ignition (Petrol/Gasoline) Engines: Knocking (or detonation) occurs when a portion of the unburnt air-fuel mixture (the "end gas") ahead of the normal spark-initiated flame front auto-ignites spontaneously due to excessive heat and pressure. This rapid, uncontrolled combustion creates pressure shock waves that strike cylinder walls, causing the sound and potentially damaging the engine (pistons, valves). It reduces engine efficiency and power.
• In Compression-Ignition (Diesel) Engines: Knocking (or diesel knock) occurs due to a relatively *long* ignition delay. When the injected fuel finally auto-ignites after accumulating in the cylinder, the combustion is very rapid and uncontrolled, causing a sudden pressure rise and the characteristic diesel knocking sound, especially noticeable at idle or low speeds. A shorter ignition delay leads to smoother combustion.

Octane Number

• Purpose: Measures the resistance of gasoline (petrol) to knocking or auto-ignition in spark-ignition engines.
• Scale: Based on a reference scale where:
  • Iso-octane (2,2,4-trimethylpentane), which is highly resistant to knocking, is assigned an octane number of 100.
  • n-Heptane, which knocks very easily, is assigned an octane number of 0.
  
• Definition: The octane number of a gasoline sample is the percentage by volume of iso-octane in a blend with n-heptane that exhibits the same anti-knocking characteristics as the sample when tested under standard engine conditions.
• Significance: A higher octane number indicates greater resistance to knocking, allowing engines to operate at higher compression ratios for better efficiency and performance without experiencing detonation. Additives (like ethanol or previously tetraethyl lead) are used to increase the octane number.

Cetane Number

• Purpose: Measures the ignition quality (ease and speed of auto-ignition) of diesel fuel in compression-ignition engines.
• Scale: Based on a reference scale where:
  • Cetane (n-hexadecane, C₁₆H₃₄), which ignites very readily with a short delay, is assigned a cetane number of 100.
  • Alpha-methylnaphthalene (or sometimes Heptamethylnonane), which has a long ignition delay, is assigned a cetane number of 0.
  
• Definition: The cetane number of a diesel fuel sample is the percentage by volume of cetane in a blend with alpha-methylnaphthalene that exhibits the same ignition delay characteristics as the sample when tested under standard engine conditions.
• Significance: A higher cetane number indicates a shorter ignition delay period, leading to quicker, smoother, and more complete combustion in a diesel engine, reducing diesel knock, improving cold starting, and lowering emissions.

7. Explain Orsat’s Apparatus method for Flue gas analysis.

The Orsat apparatus is a piece of laboratory equipment used for analyzing the volumetric composition of flue gases (combustion products), typically determining the percentages of Carbon Dioxide (CO₂), Oxygen (O₂), and Carbon Monoxide (CO) on a dry basis.

Apparatus Components:

• Measuring Burette: A graduated glass tube (usually 100 ml), surrounded by a water jacket to maintain constant temperature, used to measure the volume of the gas sample accurately. It's connected to a leveling bottle containing water or mercury, used to adjust the gas volume and pressure.
• Absorption Pipettes: Several (usually three) specialized glass pipettes connected to the burette via a manifold with stopcocks. Each pipette contains a specific chemical absorbent:
  • Pipette 1: Contains Potassium Hydroxide solution (KOH) to absorb CO₂.
  • Pipette 2: Contains Alkaline Pyrogallol solution (pyrogallic acid in KOH) to absorb O₂.
  • Pipette 3: Contains Ammoniacal Cuprous Chloride solution (Cu₂Cl₂ in ammonia) to absorb CO.
  These pipettes often contain glass tubes or beads to increase the contact surface area between the gas and the absorbent.
• Leveling Bottle: A reservoir connected to the bottom of the burette by a flexible tube, used to move the gas sample into and out of the absorption pipettes and to equalize pressure.
• Manifold and Stopcocks: Connect the burette to the absorption pipettes and the gas inlet, allowing selective passage of the gas.

Procedure:

1. Preparation: The apparatus is filled with the respective absorbents in the pipettes. The measuring burette and connecting tubes are filled with water by raising the leveling bottle, purging any air.
2. Sampling: A known volume (typically 100 ml) of flue gas is drawn into the measuring burette by lowering the leveling bottle while opening the inlet stopcock. The volume is precisely measured at atmospheric pressure.
3. CO₂ Absorption: The gas sample is passed back and forth (by raising and lowering the leveling bottle) into the first pipette containing KOH solution. KOH absorbs CO₂.
   2KOH + CO₂ → K₂CO₃ + H₂O
   The remaining gas is returned to the burette, and its volume is measured. The decrease in volume represents the volume of CO₂ absorbed.
4. O₂ Absorption: The remaining gas is then passed similarly into the second pipette containing alkaline pyrogallol, which absorbs O₂. The gas is returned to the burette, and the volume is measured again. The further decrease in volume represents the volume of O₂ absorbed.
5. CO Absorption: The remaining gas is then passed into the third pipette containing ammoniacal cuprous chloride, which absorbs CO.
   Cu₂Cl₂ + 2CO + 2H₂O → Cu₂Cl₂.2CO.2H₂O
   The gas is returned to the burette, and the volume is measured. The final decrease in volume represents the volume of CO absorbed.
6. Nitrogen Determination: The residual gas remaining after all absorptions is assumed to be primarily Nitrogen (N₂) (along with other inert gases like Argon). Its volume is determined by subtracting the final volume reading from the previous one, or it's simply the final volume left in the burette.
7. Calculation: The percentage of each gas is calculated based on the volume absorbed divided by the initial volume of the sample (usually 100 ml).

Significance: Flue gas analysis helps determine the efficiency of combustion. Excess O₂ indicates too much air was supplied, leading to heat loss. Presence of CO indicates incomplete combustion, wasting fuel and producing a pollutant. The analysis allows for adjustments to the air-fuel ratio for optimal combustion.

8. i) What is metallurgical coke? How it is superior than coal? ii) Describe the Otto Hoffmann method for the manufacturing of metallurgical coke.

i) Metallurgical Coke and its Superiority over Coal

Metallurgical Coke is a hard, porous, high-carbon material produced by heating specific types of bituminous coal (coking coals) to high temperatures (typically >1000°C) in the absence of air. This process, called carbonization or coking, drives off volatile matter (gases, tar) leaving behind a solid residue that is mostly carbon (fixed carbon) and ash.

Superiority over Coal (especially for metallurgical uses like blast furnaces):

• Higher Strength and Hardness: Coke is physically much stronger than raw coal. This allows it to support the heavy burden (charge) of iron ore and limestone in a blast furnace without crushing, maintaining permeability for gas flow.
• Higher Porosity: The porous structure provides a large surface area, allowing for better contact with air (blast) and promoting efficient combustion and heat transfer.
• Higher Fixed Carbon Content: Coke typically has a much higher percentage of fixed carbon (85-95%) compared to coal, leading to a higher calorific value per unit mass and providing the necessary carbon for reducing iron ore (Fe₂O₃ + 3C → 2Fe + 3CO).
• Lower Volatile Matter: Most volatile components are removed during coking. This prevents excessive smoke and uncontrolled burning, providing a more consistent and high-temperature heat source.
• Lower Impurities (Sulfur, Phosphorus): The coking process can reduce the content of harmful impurities like sulfur and phosphorus present in the original coal, which are detrimental to the quality of steel produced.

ii) Otto Hoffmann By-product Oven Method for Coke Manufacturing

The Otto Hoffmann method is a regenerative process for producing metallurgical coke while recovering valuable by-products from the volatile matter driven off the coal.

Construction:

• Oven Battery: Consists of a series of narrow, tall, rectangular chambers (ovens) made of refractory bricks (silica bricks), built side-by-side.
• Heating Flues: Vertical heating flues run within the walls separating adjacent ovens. Combustion of fuel gas occurs in these flues to heat the ovens indirectly.
• Regenerators: Chambers filled with checker brickwork located beneath the ovens. They work in pairs to preheat the air (and sometimes the fuel gas) used for combustion, increasing thermal efficiency. Hot flue gases from combustion pass through one set of regenerators, heating the bricks. After a set period (e.Lg., 20-30 minutes), the flow reverses: incoming air passes through the heated bricks, gets preheated, and then enters the heating flues for combustion, while the flue gases now heat the other set of regenerators.
• Charging and Discharging: Coal is charged into the top of the ovens through charging holes via a charging car. Coke is pushed out horizontally from one end of the oven by a mechanical pusher ram into a quenching car at the other end. Doors seal both ends of the oven during coking.
• By-product Recovery System: Volatile gases driven off the coal are collected from the top of the ovens through ascension pipes and sent to a complex chemical plant for cooling, cleaning, and separation into various by-products.

Process:

1. Charging: Finely crushed coking coal is charged into the hot ovens.
2. Heating (Carbonization): The ovens are heated externally and indirectly through the flue walls to about 1000-1200°C in the absence of air. The heating is controlled carefully over a period of 11 to 24 hours, depending on the oven width and desired coke properties.
3. Volatile Matter Evolution: As the coal heats up, moisture and volatile matter (coal gas, tar, ammonia, benzene, etc.) are driven off. These raw gases are collected and sent to the by-product plant.
4. Coke Formation: The remaining coal mass fuses, swells, and then solidifies into hard, porous coke.
5. Discharging and Quenching: Once carbonization is complete, the oven doors are opened, and the incandescent coke is pushed out into a quenching car. It is quickly cooled (quenched) with water or sometimes using dry methods (inert gas) to prevent combustion.
6. By-product Recovery: The collected raw gas is cooled (condensing tar and ammoniacal liquor), scrubbed (to remove ammonia, naphthalene), and processed to separate components like coal tar, ammonia (used for fertilizers), benzene, toluene, xylene (BTX), and purified coal gas (used as fuel for heating the ovens or elsewhere).

This method is highly efficient as it recovers valuable chemicals and uses the generated coal gas as fuel, significantly improving the economics of coke production compared to older beehive ovens which burned off the volatile matter.

9. Discuss the term carbon emission. Explain carbon foot print and list out the ways to reduce carbon foot print.

Carbon Emission

Carbon emission generally refers to the release of carbon gases into the atmosphere. While often used interchangeably with greenhouse gas emissions, it specifically focuses on carbon-containing gases, primarily:

• Carbon Dioxide (CO₂): The most significant greenhouse gas released by human activities, primarily from burning fossil fuels (coal, oil, natural gas) for energy, industrial processes (like cement production), deforestation, and land-use changes.
• Methane (CH₄): Another potent greenhouse gas, released from sources like agriculture (livestock digestion, rice paddies), natural gas leaks, landfills, and coal mining.
• Other carbon-containing compounds (like carbon monoxide, CO, although its direct greenhouse effect is less significant than its indirect effects).

These emissions trap heat in the Earth's atmosphere, contributing to global warming and climate change.

Carbon Footprint

A carbon footprint is the total amount of greenhouse gases (GHGs)—primarily carbon dioxide and methane—generated directly and indirectly by an individual, organization, event, product, or activity, usually expressed in equivalent tons of CO₂ (CO₂e).

• Direct Emissions (Scope 1): Emissions from sources owned or controlled by the entity, e.g., burning fuel in a car or furnace, emissions from industrial processes.
• Indirect Emissions (Scope 2): Emissions from the generation of purchased energy (electricity, heat, steam).
• Indirect Emissions (Scope 3): All other indirect emissions occurring in the value chain, e.g., emissions from producing purchased materials, business travel, waste disposal, transportation of goods, use of sold products.

It provides a measure of the impact on climate change associated with a particular entity or action.

Ways to Reduce Carbon Footprint

Reducing one's carbon footprint involves minimizing GHG emissions across various aspects of life and operations. Key strategies include:

1. Energy Conservation & Efficiency:
   • Reduce overall energy consumption at home and work (turn off lights/appliances, better insulation).
   • Use energy-efficient appliances, lighting (LEDs), and equipment.
   • Optimize industrial processes for energy efficiency.
2. Switch to Renewable Energy:
   • Source electricity from renewable providers (solar, wind, hydro).
   • Install solar panels for homes or businesses.
3. Sustainable Transportation:
   • Reduce reliance on private cars: use public transport, walk, cycle.
   • Choose fuel-efficient vehicles or switch to electric vehicles (EVs) or hybrids (especially if charged with renewable energy).
   • Minimize air travel, especially long-haul flights.
   • Optimize logistics and shipping routes.
4. Dietary Changes:
   • Reduce consumption of meat and dairy products, particularly beef and lamb, which have high associated emissions (methane from livestock, land use).
   • Eat locally sourced and seasonal food to reduce transportation emissions.
   • Minimize food waste.
5. Reduce, Reuse, Recycle:
   • Consume less overall (buy fewer new products).
   • Choose products with minimal packaging.
   • Reuse items whenever possible.
   • Recycle paper, plastic, glass, and metal properly.
   • Compost organic waste.
6. Water Conservation:
   • Reducing water use saves the energy required for water treatment and pumping.
7. Sustainable Practices in Business/Industry:
   • Implement green building standards.
   • Optimize supply chains for lower emissions.
   • Invest in carbon capture technologies (where applicable).
   • Shift to sustainable raw materials.
8. Offsetting (as a complementary measure):
   • Invest in projects that reduce or remove GHG emissions elsewhere (e.g., reforestation, renewable energy projects) to compensate for unavoidable emissions.

Reducing carbon footprints requires a combination of individual actions, technological innovation, corporate responsibility, and supportive government policies.