The equipment installed in power plants to reduce air pollution due to smoke is

Question

Examoogle · Accepted Answer

Electrostatic precipitators

Explanation: Electrostatic Precipitators (ESP) are industrial devices used in thermal power plants to remove fine particulate matter, such as fly ash and dust, from flue gases before they are released into the atmosphere. They effectively capture dust particles through electrostatic force, ensuring compliance with environmental emission standards.

Working Principle: The flue gas passes through a series of electrodes. A high-voltage DC supply creates a corona discharge, ionizing the gas molecules and giving the dust particles a negative charge. These negatively charged particles are then attracted to positively charged collection plates (grounded), where they settle and are periodically knocked off by mechanical rappers into collection hoppers.

Key Formulas: $F_e = qE$ — electrostatic force on a particle with charge $q$ in an electric field $E$; $\eta = 1 - e^{-(\frac{A}{Q})w}$ — Deutsch-Anderson equation for collection efficiency, where $A$ is collection area, $Q$ is gas flow rate, and $w$ is drift velocity

Key Points: ESPs operate with very high efficiency, often exceeding 99%.; They are effective for both large and sub-micron sized particles.; The process relies on the resistivity of the fly ash; if resistivity is too high, performance drops.

Advantages: Very high collection efficiency for fine particles.; Low pressure drop across the device compared to bag filters.; Capable of handling large volumes of gas at high temperatures.

Disadvantages: High initial capital and installation cost.; Performance is highly sensitive to the electrical resistivity of the dust.; Requires significant high-voltage power supply equipment.

Applications: Thermal Power Plants (Coal-fired).; Cement Industry for kiln gas cleaning.; Steel and Paper manufacturing plants.

Additional Info: Induced draft fans (Option A) provide mechanical pressure to move flue gas, not for pollution control.. De-super heaters (Option B) are used to regulate steam temperature.. Re-heaters (Option D) are heat exchangers used to increase the efficiency of the Rankine cycle.

Answer: C is correct — Electrostatic precipitators use electrostatic forces to separate dust particles from flue gases in power plant stacks.

Exam Tip: In competitive exams, remember that ESPs are synonymous with high-efficiency particulate removal; if the question asks for gaseous pollutants (like $SO_2$), look for 'Scrubbers' instead.

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