Types of Coal Feeders: A Detailed Overview and Comparison

Types of Coal Feeders: A Detailed Overview and Comparison

Coal feeders play a crucial role in the coal handling and preparation plant (CHPP) process. They are essential for conveying and metering of raw coal to the pulverizers, where it is efficiently ground and converted into a fine coal powder for combustion in the boiler. Coal feeders come in different types to suit various plant requirements and are designed to assist in achieving optimal coal flow and distribution.

1. Gravimetric Feeders: Gravimetric coal feeders are commonly used feeders for handling coal in power plants. They use the principle of weighing coal on a weighing platform using load cells. The load cells ensure accurate and reliable coal weighing, resulting in the precise control of coal flow to the pulverizer. Gravimetric feeders offer excellent control over fuel flow rate, leading to better combustion control and reduced emission of pollutants.

2. Volumetric Feeders: Volumetric coal feeders are another commonly used type of feeder in coal handling plants. They operate based on the volume or mass flow rate of coal. Volumetric feeders use a variable speed drive to adjust the coal flow by controlling the speed of a belt or screw conveyor. While volumetric feeders are simpler and more cost-effective, they offer less accuracy compared to gravimetric feeders.

3. Belt Feeders: Belt feeders are widely used in coal handling plants as they provide a continuous flow of coal. They consist of a belt conveyor that carries the coal from the storage unit to the discharge point. Belt feeders offer flexibility in terms of rate, speed, and capacity adjustments to suit the requirements of the CHPP. They can be designed with various features like weigh scale integrators, belt tensioners, and material flow control gates.

4. Screw Feeders: Screw feeders are another type of coal feeders that are commonly used in the CHPP process. They consist of a rotating auger inside a casing, which transports the coal from the hopper to the discharge point. Screw feeders offer accurate coal flow rate control by adjusting the screw speed and pitch. They are known for their simple design, low maintenance, and high reliability.

5. Rotary Feeders: Rotary feeders, also known as rotary airlocks, are widely used in coal handling plants for feeding coal into pneumatic conveying systems or to maintain a consistent coal flow into the pulverizers. They consist of a rotating valve with vanes that seal against the coal flow, preventing air leakage. Rotary feeders offer excellent sealing properties and can handle high-pressure differentials. They are crucial for maintaining proper pressure balance and preventing air ingress into the pulverizing system.

In conclusion, coal feeders are vital components of coal handling and preparation plants. The choice of the type of feeder depends on several factors, including accuracy requirements, plant size, and budget. Gravimetric feeders provide excellent precision and control, while volumetric feeders offer simplicity and cost-effectiveness. Belt feeders, screw feeders, and rotary feeders each have their specific advantages in terms of continuous coal flow and control. Selecting the appropriate coal feeder is essential for efficient and smooth operation of the CHPP process.

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