Unit 2: Industrial Metallurgy and Environment
Course Code: CHM-DSC-353
Paper Name: Industrial Chemistry
1. Thermodynamics of Metallurgy
The extraction of metals from their ores is governed by thermodynamic principles, primarily the relationship between Gibbs free energy and temperature.
Ellingham Diagram
An Ellingham diagram is a plot of ΔG° versus temperature for the formation of metal oxides. It helps in selecting the right reducing agent for a particular metal oxide.
[Image of Ellingham diagram for metal oxides]
- Principle: A metal can reduce the oxide of any other metal that appears above it in the diagram (where the ΔG° is less negative).
- Carbon as a Reducing Agent: Carbon (C) is a popular reducing agent because the line for C → CO slope downwards, intersecting most metal oxide lines at high temperatures.
2. Steel Manufacturing and Surface Treatment
Steel is an alloy of iron and carbon, often with other elements to enhance properties.
- Production: Major industrial processes include the Basic Oxygen Furnace (BOF) and Electric Arc Furnace (EAF).
- Surface Treatments: Metals are treated to prevent corrosion and improve wear resistance.
- Anodizing: An electrolytic process that increases the thickness of the natural oxide layer on metals like Aluminum.
- Galvanizing: Coating steel or iron with a layer of Zinc to prevent rusting.
3. Air Pollution: Sources and Control
Industrial processes contribute significantly to atmospheric pollution. Key pollutants include SOx, NOx, and particulate matter.
Control Methods
- Electrostatic Precipitators (ESP): Used to remove fine particulate matter from flue gases using an electric charge.
- Scrubbers: Devices that use a liquid spray to remove gases (like SO2) or particles from a gas stream.
- Catalytic Converters: Used in vehicles to convert toxic gases (CO, NOx) into less harmful substances (CO2, N2).
4. Water Pollution and Effluent Treatment
Industrial wastewater (effluent) contains heavy metals, organic toxins, and suspended solids that must be treated before discharge.
Effluent Treatment Plant (ETP) Stages
- Primary Treatment: Physical processes like screening, sedimentation, and grit removal.
- Secondary Treatment: Biological processes using microorganisms to break down organic matter (e.g., Activated Sludge Process).
- Tertiary Treatment: Advanced chemical or physical treatments like chlorination, UV radiation, or Reverse Osmosis (RO) to remove remaining contaminants.
5. Exam Focus: Tips and FAQs
Exam Tips
- Ellingham Interpretation: Be prepared to explain why Magnesium can reduce Alumina at low temperatures, but the reverse happens at very high temperatures.
- Pollution Standards: Mention parameters like BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) when discussing water quality.
- Corrosion: Explain how galvanizing provides "sacrificial protection" to the base metal.
Frequently Asked Questions
Q: What is the significance of the "kink" in an Ellingham diagram line?
A: A kink indicates a phase change (melting or boiling) of the metal or its oxide, which results in a change in entropy (ΔS).
Q: How does a wet scrubber work for SO2 removal?
A: Flue gas is passed through a slurry of limestone (CaCO3). The SO2 reacts with the limestone to form Calcium Sulphite/Sulphate, which is then removed as a solid.
Q: Define "Sacrificial Anode".
A: It is a more reactive metal (like Zinc or Magnesium) attached to a less reactive metal structure (like a ship hull) to corrode in its place, protecting the structure.