How Does a Coal Fired Power Station Work?

Coal fired power stations have been a cornerstone of electricity generation for over a century. Despite the rise of renewable energy sources, coal remains a significant contributor to the global energy mix. Understanding how a coal fired power station works is essential for grasping the fundamentals of traditional power generation. This article provides a detailed overview of the process, breaking it down into key steps to explain how coal is transformed into electricity.

Coal Supply and Preparation

The process begins with the supply of coal, which is typically delivered to the power station by train, truck, or conveyor belt. Once at the plant, the coal undergoes preparation, which includes crushing and pulverizing it into a fine powder. This increases the surface area of the coal, allowing it to burn more efficiently and completely in the boiler.

Combustion in the Boiler

The pulverized coal is blown into the boiler’s combustion chamber, where it is ignited at high temperatures. The intense heat generated from burning coal converts water in the boiler tubes into high-pressure steam. The boiler is designed to maximize heat transfer and ensure the complete combustion of coal, minimizing waste and emissions.

Steam Generation

As the water turns into steam, it reaches extremely high temperatures and pressures. This steam is then directed through a series of pipes to the turbine. The quality and pressure of the steam are critical to the efficiency of the power station, with modern plants operating at supercritical or ultra-supercritical pressures to improve performance.

Turbine Operation

The high-pressure steam enters the turbine, where it expands and cools as it passes over the turbine blades. This expansion causes the turbine blades to spin rapidly. The turbine is connected to a generator shaft, so as the turbine spins, it drives the generator to produce electricity.

Electricity Generation

Inside the generator, the mechanical energy from the turbine is converted into electrical energy. This is achieved through electromagnetic induction, where the rotating turbine shaft turns a rotor inside a magnetic field, inducing an electric current in the stator windings. The generated electricity is then sent to transformers to increase its voltage for transmission over power lines.

Steam Condensation and Recycling

After passing through the turbine, the steam enters a condenser where it is cooled and condensed back into water. This process uses cooling water from nearby sources such as rivers, lakes, or cooling towers. The condensed water is then pumped back into the boiler to be reheated, making the system a closed loop.

Emission Control Systems

Coal combustion produces pollutants such as sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter, and carbon dioxide (CO2). Modern coal fired power stations are equipped with various emission control technologies including electrostatic precipitators, scrubbers, and selective catalytic reduction systems to reduce harmful emissions and comply with environmental regulations.

Ash Handling

Burning coal produces ash as a byproduct. This ash is collected from the boiler and the flue gas cleaning systems. It is then transported to ash disposal sites or sometimes used in construction materials like cement and concrete, reducing waste and environmental impact.

Transmission and Distribution

The electricity generated at the power station is transmitted over high-voltage power lines to substations. From there, it is stepped down to lower voltages and distributed to homes, businesses, and industries. The entire transmission and distribution system ensures that electricity reaches end-users reliably and efficiently.

In summary, a coal fired power station works by converting the chemical energy stored in coal into electrical energy through a series of well-coordinated steps. The process involves coal preparation, combustion, steam generation, turbine operation, electricity generation, steam condensation, emission control, ash handling, and finally, transmission of electricity to consumers. While coal fired power stations have been vital for electricity production, ongoing advancements aim to improve their efficiency and reduce environmental impact. Understanding these core processes provides insight into how traditional power plants function and the challenges they face in the evolving energy landscape.