Question

Describe the process by which electricity is generated through the combustion of coal.

Short answer

The process of electricity generation through coal combustion involves the following steps: 1. Burning coal in a furnace at high temperatures to release heat energy and produce a gas mixture. 2. Converting the heat energy into high-pressure steam by heating water in a boiler. 3. Using the high-pressure steam to rotate a turbine, which is connected to a generator to convert the mechanical energy into electrical energy. 4. Transmitting the generated electricity through transformers and power lines to the end-users.

Step-by-step solution

Coal Combustion

In the first step of electricity generation through coal combustion, we need to burn the coal. The coal is ground into powder-like consistency and burnt in a furnace at very high temperatures, around 1500-1700°C. This process results in releasing a lot of heat energy and generating a gas mixture primarily of carbon dioxide (CO2), water vapor (H2O), nitrogen (N2), and other pollutants including sulfur dioxide (SO2), and nitrogen oxides (NOx).

Heat Conversion

The next step is to convert the heat energy generated during coal combustion into a usable form. The thermal energy obtained from the furnace is used to heat water in a boiler and produce high-pressure steam. The steam, at a high temperature and pressure, is then sent to a turbine.

Turbine and Generator

The high-pressure steam produced in the boiler is used to power a turbine. A turbine is a large mechanical device with several blades (similar to a fan) that are attached to a shaft. The steam coming from the boiler is directed onto the turbine blades, which cause the turbine to rotate. This rotation converts thermal energy from the steam into mechanical energy. The turbine shaft is connected to a generator, which is responsible for converting the mechanical energy from the turbine into electrical energy. The generator is made up of a stationary part called the stator and a rotating part called the rotor. Inside the generator, there are coils made of conductive materials like copper. As the rotor rotates, it induces a flow of electrons in the conductive coils, generating electricity.

Electricity Transmission

After electricity is generated in the generator, it is sent to transformers to increase its voltage. High voltages help in transmitting electricity over long distances with minimal loss. The electricity is then transmitted through power lines to homes, businesses, or other areas where it is needed. In summary, the process of electricity generation through coal combustion involves burning coal to obtain thermal energy, converting the energy to high-pressure steam, using the steam to power a turbine and generator, and finally transmitting the electricity to the end-users.

Key concepts

Electricity Generation

Electricity generation is the fundamental process of producing electrical power. In coal combustion, this begins with the burning of coal in a furnace. This step is crucial as it releases a significant amount of heat energy. The coal is first crushed into a fine powder for efficient combustion. This powdered coal is burned at very high temperatures, around 1500-1700°C.

The main objective here is to convert the chemical energy stored in coal into thermal energy. This process releases a mixture of hot gases, including carbon dioxide ( CO_2 ), water vapor ( H_2O ), and various pollutants. Each of these by-products needs to be managed, but the focus of this step is harnessing the heat generated to proceed to the next stages of electricity generation.

Thermal Energy Conversion

Thermal energy conversion involves utilizing the heat generated from the burning coal to produce steam. This step is crucial for moving to the mechanical phase of electricity generation.

In the furnace, the intense heat produced warms the water in nearby boilers. As this water heats, it turns into steam. This steam is not just any steam; it reaches high pressures and temperatures, making it a powerful energy carrier.

• The steam reaches temperatures over several hundred degrees Celsius.
• It is created under high pressure to maximize energy transfer efficiency.

Once formed, this energetic steam is ready to travel to the steam turbine, where it will play a major role in mechanical conversion.

Steam Turbine

The steam turbine is at the core of mechanical energy conversion. Here, high-pressure steam pushes against turbine blades, causing them to spin.

This process efficiently converts thermal energy from the steam into mechanical energy. The moving blades are connected to a shaft that also rotates, transferring this energy into the generator. A clear example of how heat energy is translated into motion!

Turbines are engineered for maximum efficiency in energy conversion. The continuous rotation of the shaft driven by the steam's force is vital for the generator to function and produce electricity. The turbine is thus integral in bridging the gap between thermal energy and electrical energy production.

Electricity Transmission

Once the generator transforms mechanical energy into electrical energy, it's time to get that electricity to the consumers. This involves increasing the voltage of electricity for effective long-distance travel.

High voltages are crucial because they reduce energy losses during transmission. Think of electricity like water flowing through a pipe: high pressure means less is lost along the way. This conversion is achieved using transformers.

After stepping up the voltage, the electricity travels through a vast network of transmission lines. These lines are like highways carrying electricity to homes, industries, and businesses efficiently. Only after reaching the destination are voltages decreased using local transformers for safety and usability.