Coal Handling System In Thermal Power Plant
Introduction
In thermal power plants, coal is the primary fuel for electricity generation. The Coal Handling Plant (CHP) plays a pivotal role in managing coal from its arrival at the plant to its final combustion in the boiler. This system ensures a continuous, efficient, and safe coal supply while addressing challenges like size reduction, moisture control, and dust suppression. The CHP comprises sequential processes—unloading, feeding, screening, crushing, stacking, reclaiming, and bunkering—supported by specialized equipment tailored for each stage. Let’s explore how these processes and components work together to maintain seamless power generation.
Type Of Coal Received In Coal Handling Plant
Generally, E and F-grade coal is received in thermal power stations. Grades of coal and their respective calorific value are listed below. coal grade
| GRADE | CAROFILIC VALUE ( K AL/Kg. ) | % ( Ash + Moisture) |
| A | More than 6200 | 19.5 |
| B | 5600 – 6200 | 19.6 – 23.8 |
| C | 4940 -5600 | 23.9 – 28.6 |
| D | 4200 – 4940 | 28.7 – 34.0 |
| E | 3360 – 4200 | 34.1 – 40.0 |
| F | 2400 – 3360 | 40.1 – 47.0 |
Basic Coal Flow Diagram of Coal Handling Plant In Thermal Power Plant
Processes and Equipment in a CHP
1. Unloading Process
Coal arrives via BOBR (Bogie Open Bottom Discharge) or box-type wagons. BOBR wagons discharge coal directly into track hoppers, which are 210-meter-long reinforced concrete structures with steel gratings. Box-type wagons, however, require a wagon tippler to tilt them at 135°, emptying coal into hoppers. A side arm charger accelerates this process by swiftly positioning wagons on the tippler. Hydraulic truck unloaders handle coal delivery from trucks in plants without rail infrastructure.
2. Feeding Process
Feeders regulate coal flow to match boiler demand. Paddle feeders handle sticky or frozen coal, while apron feeders manage heavy loads. Belt or reversible belt feeders adjust flow rates, and vibrating feeders ensure uniform discharge onto conveyor belts.
3. Screening and Crushing
First, vibrating or roller screens segregate coal into fine (<20 mm), coarse, and wet grades. After the screening, oversized coal moves to ring granulator crushers, which crush it into optimal boiler-compatible sizes. These crushers use impact forces to ensure efficient size reduction, preparing the coal for smooth combustion in the boiler.
4. Stacking & Reclaiming
Excess coal is stacked into storage yards using a stacker cum reclaimer, a dual-purpose machine with a radial conveyor for stacking, and a bucket wheel for reclaiming. Stacking occurs when bunkers are complete while reclaiming resumes when bunker levels drop, ensuring uninterrupted fuel supply.
5. Bunkering
The traveling tripper trolley distributes coal from conveyors into boiler bunkers. Flap gates and rack-and-pinion gates direct or block coal flow as needed.
6. Auxiliary Systems
- Dust Control: Dust extraction (DE) systems filter airborne particles, while dry fog dust suppression (DFDS) sprays fine fog to settle dust at conveyor transfer points.
- Quality Checks: A coal sampling unit (CSU) collects samples for analysis, and belt weigh scales monitor coal flow rates.
- Safety: Suspended magnets and inline magnetic separators (ILMS) remove tramp metal to protect downstream equipment.
Coal Specifications and Maintenance
Thermal plants typically use E and F-grade coal (calorific value: 2,200–3,500 kcal/kg). To ensure CHP reliability, maintenance strategies include:
1. Preventive Maintenance
Preventive maintenance involves proactive, scheduled inspections and equipment servicing to detect and resolve potential issues before they escalate into failures. Activities are planned based on time intervals (e.g., monthly, annually) or usage metrics (e.g., operating hours, coal throughput). Adhering to a structured schedule minimizes unexpected downtime, extends equipment lifespan, and ensures operational reliability. Examples include lubrication of conveyor bearings, belt alignment checks, and crusher component replacements.
2. Breakdown Maintenance
Breakdown maintenance refers to reactive repairs conducted after equipment fails and becomes non-operational. This “run-to-failure” strategy is typically employed for non-critical machinery where sudden stoppages do not severely disrupt plant operations. While cost-effective in the short term, frequent breakdowns can lead to prolonged downtime, safety risks, and higher long-term repair costs.
3. Corrective Maintenance
Corrective maintenance focuses on identifying, isolating, and repairing specific faults in equipment to restore it to its original working condition. Unlike breakdown maintenance, it addresses issues detected before complete failure occurs—such as abnormal vibrations in a crusher or leaks in hydraulic systems. This approach combines troubleshooting and targeted repairs to prevent minor defects from escalating.
4. Predictive Maintenance (Condition Monitoring)
Predictive maintenance uses real-time data and condition-monitoring tools to assess equipment health and predict failures. Key parameters like temperature, vibration, power consumption, and sound patterns are analyzed to forecast wear and tear. Advanced techniques such as thermal imaging, vibration sensors, and oil analysis enable maintenance teams to schedule interventions only when needed, optimizing resource use and reducing unnecessary downtime.
Conclusion
The Coal Handling Plant is the backbone of a thermal power plant, efficiently transporting, processing, and storing coal while reducing operational risks such as dust explosions or equipment damage. Additionally, advanced unloading systems like wagon tipplers and eco-friendly dust suppression technologies are critical in enhancing fuel quality and plant performance. Moreover, engineers meticulously design each component to ensure reliability and efficiency, making the CHP a cornerstone of seamless power generation. By adhering to structured maintenance practices and leveraging robust equipment, CHPs enhance energy output and align with sustainability goals. Understanding this system’s intricacies is key to improving thermal power generation’s efficiency and reliability in the long term.
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