Module 4 Lesson 3 Liquid Fuels

Summary

This lesson covers the vital role of liquid fuels, particularly petroleum, in industrial and domestic sectors. It explores the composition, extraction, and refining of petroleum, emphasizing key processes like distillation and cracking that convert crude oil into usable products such as gasoline, kerosene, and diesel. The lesson also delves into the workings of internal combustion engines, highlighting the importance of compression ratios and the issue of knocking, which affects engine performance. Finally, it examines the advancements in refining technologies, including catalytic cracking, to enhance fuel quality and efficiency.

Takeaways

• 😀 Liquid fuels are widely used in both industrial and domestic applications, particularly in internal combustion engines.
• 😀 Petroleum is the largest source of liquid fuels, with a calorific value of about 40,000 KJ/kg.
• 😀 The average composition of petroleum includes 70-80% carbon, 11-15% hydrogen, and trace amounts of sulfur, oxygen, and nitrogen.
• 😀 Crude oil is derived from organic matter found in marine sediments, undergoing microbial and chemical processes to form petroleum.
• 😀 There are three main types of petroleum: paraffin-based, asphalt-based, and mixed-based, with the latter being the most common.
• 😀 Petroleum is refined in distillation towers, where different products like gasoline, kerosene, and diesel are separated based on boiling points.
• 😀 Cracking processes, such as thermal and catalytic cracking, are used to break down heavier hydrocarbons into lighter, valuable products like gasoline.
• 😀 Thermal cracking uses high heat and pressure to break down hydrocarbons, producing gasoline with lower stability and octane rating.
• 😀 Catalytic cracking uses a catalyst to enhance gasoline production, yielding higher-quality fuel with improved anti-knock properties and better stability.
• 😀 In internal combustion engines, fuel combustion results in power strokes, while factors like compression ratio and knocking impact engine performance and efficiency.

Q & A

What is the primary source of liquid fuels, and what is its calorific value?

The primary source of liquid fuels is petroleum, which has a calorific value of about 40,000 KJ per kilogram.

What is the average composition of petroleum based on ultimate analysis?

The average composition of petroleum is about 80-70% carbon, 11.1-15% hydrogen, 0.1-3.5% sulfur, 0.1-0.9% oxygen, and 0.4-0.9% nitrogen.

How is crude oil derived, and what is the process involved in its formation?

Crude oil is derived from organic matter originally present in marine sediments. Dead organic matter settles at the bottom of seas and lagoons, where anaerobic bacteria break it down into unsaturated fatty oils and fatty acids, leading to petroleum formation.

What are the three main types of petroleum based on chemical nature?

The three main types of petroleum are: 1) Paraffin-based crude, which contains saturated hydrocarbons; 2) Asphalt-based crude, which includes naphthenes and cycloparaffins; 3) Mixed-based crude, which contains both types and is rich in waxes.

What is the process of petroleum distillation, and what are the key products?

In petroleum distillation, crude oil is heated to about 400°C and subjected to fractional distillation, where different boiling point fractions are separated. Key products include gasoline, naphtha, kerosene, gas oil, and residual oils like lubricating oils and paraffin wax.

What are the differences between thermal cracking and catalytic cracking?

Thermal cracking uses heat and pressure to break down heavy oils into smaller molecules, resulting in gasoline and cracking gases. Catalytic cracking, on the other hand, uses a catalyst to crack oils at lower temperatures and pressures, producing higher yields of gasoline with better anti-knock properties and fewer undesirable byproducts.

Why is catalytic cracking considered more efficient than thermal cracking?

Catalytic cracking is more efficient because it requires lower temperatures and pressures, uses a catalyst that accelerates reactions, and produces a higher percentage of gasoline with improved quality, including lower sulfur content and better anti-knock properties.

What is the significance of the compression ratio in internal combustion engines?

The compression ratio is the ratio of the cylinder's volume at the end of the suction stroke to its volume at the end of the compression stroke. A higher compression ratio increases engine efficiency, but if it exceeds a certain limit, it can cause pre-ignition or knocking, which may damage the engine.

What causes knocking in internal combustion engines?

Knocking occurs when the fuel-air mixture in the engine's cylinder ignites prematurely or irregularly, causing a violent explosion that generates a metallic sound. This happens due to a high compression ratio, which causes the fuel to self-ignite before the spark plug fires.

What role does sulfur removal play in petroleum refining?

Sulfur compounds are removed during petroleum refining because they have undesirable pollution properties. The sulfur is typically removed before distillation through processes like copper oxide treatment, ensuring that the refined petroleum products are cleaner and less polluting.