coal crusher plant pdf

An Overview of Coal Crusher Plant Design and Operation

A coal crusher plant is a critical facility within the material handling system of coal-fired power stations, coke plants, and other coal processing industries. Its primary function is to reduce the size of mined or stockpiled coal to a specific top size suitable for transportation, washing, or direct combustion. The design and selection of crushers are paramount for ensuring plant efficiency, reliability, and meeting product specifications. This article outlines the key components, crusher types, selection criteria, and operational considerations for a modern coal crusher plant. It will explore common configurations through a comparative analysis and present a real-world application case study.

Core Components and Crusher Types
A typical stationary coal crushing plant consists of several key elements: a feed hopper with a vibrating grizzly feeder to regulate material flow and remove fines, the primary crusher itself, conveyor systems for material transfer between stages (if needed), and sometimes secondary crushers or screens for further size reduction and classification. Dust suppression systems are integral to maintaining environmental and safety standards.

The choice of crusher depends on the coal characteristics (hardness, moisture content, abrasiveness) and the required product size. The two most prevalent types in coal applications are:

• Ring Granulators: A type of impact crusher ideal for crushing coal to a cubical product shape. They are highly efficient for reducing run-of-mine (ROM) coal to a stoker or utility grade size.
• Roll Crushers: Employ compression to break material. They are suitable for friable materials and can produce a uniform product with minimal fines generation. Double roll crushers are common for secondary crushing or for crushing middlings in washery circuits.

The following table contrasts their typical applications:

Feature	Ring Granulator Crusher	Double Roll Crusher
Primary Mechanism	Impact	Compression
Best For	Primary crushing of ROM coal; high capacity requirements.	Secondary/tertiary crushing; where minimal fines are desired.
Product Shape	Cubical	Slabby or flaky (can be more cubical with corrugated rolls).
Moisture Tolerance	Moderate - high moisture can lead to clogging.	Handles sticky materials better due to scraping mechanisms.
Typical Reduction Ratio	Up to 40:1	4:1 to 7:1

Other equipment like hammer mills or rotary breakers may be used in specific contexts, such as handling very wet or clay-bound coals.

Design Considerations and Real-World Case Study
Effective plant design revolves around capacity matching the upstream mining and downstream process requirements. Key factors include feed size analysis, desired product gradation (e.g., -50mm for power plants), hourly throughput (TPH), available space, and maintenance access.

A notable real-world example is the retrofit project at the Neyveli Lignite Corporation (NLC) in Tamil Nadu, India. Facing challenges with existing equipment's capacity and maintenance downtime for their lignite-fired power stations, NLC implemented new ring granulator-based crushing stations. The design prioritized high availability and ease of maintenance. The new plants were engineered to handle the specific properties of lignite—softer but with higher moisture content—incorporating robust feeders and chute designs to prevent bridging. This upgrade resulted in documented improvements in plant availability by over 15% and reduced specific energy consumption per ton of crushed lignite, ensuring a more reliable fuel supply to the boiler bunkers.

Operational Best Practices
Regular inspection and preventive maintenance are crucial for sustained operation. Key focus areas include monitoring hammer/roll wear liners, checking rotor balance (for impact crushers), ensuring proper belt tension on drives, and maintaining effective dust suppression nozzles. Operators must avoid metal contaminants ("tramp iron") entering the crusher chamber, which is typically mitigated by metal detectors and magnetic separators installed upstream.

---

Frequently Asked Questions (FAQs)

Q1: What is the main difference between primary and secondary crushing in a coal plant?
Primary crushing handles the raw, run-of-mine (ROM) coal directly from the mine at its largest size (which can be several feet across), reducing it to a manageable size (typically 6-8 inches). Secondary crushing takes this output and reduces it further to meet final product specifications (e.g., under 2 inches). Some plants may use a single-stage primary crusher if product requirements allow.

Q2: How is dust control managed in a coal crusher plant?
Dust suppression is achieved through integrated systems that include water spray nozzles at strategic transfer points like feeder exits, crusher inlets/outlets, and conveyor head/tail pulleys. Enclosures around crushers coupled with baghouse filtration systems (dust collectors) are also employed where water use is undesirable or insufficient.

Q3: What factors most influence the choice between a ring granulator and a roll crusher?
The decision hinges on three core factors: 1) Feed Size & Capacity: Ring granulators handle larger feed sizes at higher capacities.
2) Product Gradation: If producing minimal fines is critical (e.g., for coke oven feed), roll crushers may be preferred.
3) Material Properties: For harder coals or those with abrasive impurities like shale/sandstone contained within it , ring granulators' design often offers better wear management capabilities compared against smooth surfaced rolls which would wear quickly under abrasive conditions .

Q4: How often does major maintenance on a primary coal crusher typically occur?
Major overhaul intervals depend heavily on abrasiveness of material processed but generally range from 12 months up-to even beyond every few years based upon operational hours . Key wear parts like hammers , rings ,or roll shells however might need replacement/reversal much more frequently – sometimes as often as every few weeks under severe abrasive conditions – making easy access design vital during initial engineering phase itself .

Q5: Can mobile or semi-mobile crushers be used instead of fixed plants?
Yes,mobile & semi-mobile crushing units have become increasingly popular especially within mining operations due their flexibility allowing them move alongside advancing mine faces thereby reducing truck haulage distances significantly leading towards lower operational costs overall while maintaining consistent throughput rates required by downstream processes effectively too .