How Do You Ensure Each Coal Blend Meets Customer Specifications?

Why Analyze Coal? A single coal mine can produce different types of coal of varying composition and quality because of the disparate concentrations of sulfur, ash, and moisture throughout the mine area. These distinctions can influence the way coal burns and the emissions it gives off. Coal with too much moisture, ash, or sulfur won’t meet boiler specifications and cause process inefficiencies and poor output. Online elemental coal analyzers, which measure sulfur, ash, moisture, calorific value, and all major ash constituents, help to ensure that each coal blend meets customer specifications. Online analysis can be accomplished with a sample stream analyzer or a full flow analyzer. Criteria for choosing a sample stream analyzer include:

• Stringent accuracy requirements.
• Highly variable belt loading with top sizes greater than 4 inches.
• Conveyor belt conditions such as steel corded belts or belt sizes of 72 inches and greater.
• Installation conditions such as
  • Two parallel belt conveyors, which might be able to share—in a multiplexed manner—a single sample stream analyzer;
  • Existing sampling system with which a sample stream analyzer can be easily integrated.

Why Use A Sample Stream Analyzer? Coal producers, as well as utilities, use online coal analyzers because they improve accuracy and therefore profitability. The more you can move the target quality set point closer to the upper limit, the more you can keep ash levels on target to meet contract specifications. Even slight improvements in accuracy can lead to huge profit differences. Sample stream coal analyzers ensure better accuracy through:

• Better initial calibration.
• Detecting problems or changes in the analysis environment such as different coal types, different belt loading conditions (rate of variability, bed depth, top size, surcharge angle, new conveyor), and changes in bound moisture.
• Real time monitoring of the blended product ash level and periodic adjustment in the fraction of raw coal that bypasses the plant to minimize deviation from the target ash levels.

Of these examples, calibration may be the most important. Analyzer owners who exercise diligence in their calibration maintenance reap the most economic rewards. Factory calibration is important but factory testing doesn’t fully capture the lack of homogeneity in the coal, the varying belt loading, the profile on the belt, and the belt composition. On-site calibration is the “acid test.” Coal producers and utilities each reap unique benefits by using online coal analyzers. Coal producers:

• Fewer penalties by consistently meeting contract specifications (blending).
• Better prep plant efficiency, less over-cleaning.
• More consistent coal quality leads to better price and/or market share.
• Increasing mine life by maximizing use of all various quality coals.

Utilities:

• Reduced fuel cost by maximizing the blending process.
• Increased boiler efficiency, hence reduction of amount of coal being burned, resulting in less CO₂ emissions.
• Fuel flexibility.

An online coal analyzer, combined with coal blending software, offers the most effective way to minimize variations in coal quality, ensure contract compliance, and improve efficiency. The Importance of Sampling for Optimal Coal Analyzer Performance provides details, including savings calculations, on the benefits of these systems. Are you a coal producer or utility using an online coal analyzer? Tell us about your experiences.