Did you know that every person in the United States uses approximately 3.7 tons of coal each year? In fact, coal is the most affordable source of fuel to date, currently accounting for 32-percent of the total energy production in the United States and 23-percent of the total energy consumption.
But the cost of coal can vary drastically. Sampling coal is integral to determine how much it should be sold or traded for. Not all coal is equal. The quantity and chemical properties of coal can only be determined through analysis in a laboratory.
While there are different coal sampling methods and types of equipment used, you’ll better understand how coal sampling generally works in these eight steps:
1. Sample collection
The first step in coal sampling, of course, is collecting the sample. Coal is shoveled into a bag directly at the coal mining site. The coal is sifted to separate tiny debris from the bigger chunks of coal. The larger pieces of coal are typically weighed.
If the analysis will be done off-site, the coal is bagged and often sent to a lab in a cubic, tightly-packed 30-centimeter edge box.
2. Grinding and routing labeling
Once the bigger pieces of coal are separated and weighed, they are often labeled with special grinding and routing instructions. These instructions might vary from coal to coal.
3. Air drying
Some pieces of coal will need to be air-dried if they are wet. Once these are identified, they are placed on an aluminum or plastic pan and will be left to dry for approximately a week. Some pieces might need to be air-dried longer depending on much moist they are.
4. Container cleaning and labeling
Containers that will be used for sample splits will be cleaned via a stream of air. Before crushing takes place, the containers will also be labeled.
5. Crushing and grinding
Once coal is brought to the crushing laboratory, each piece will be crushed one at a time. Extra coal samples will be stored outside of the laboratory to reduce the chances of cross-contamination.
6. Homogenization and splinting
Once crushed, the sample will be rolled onto wax paper for homogenization. The homogenized sample will then be splinted twice. The second splint will be splinted once again, leaving a total of four splints. Some portions will be utilized for ashing, and thus, for the coal analysis itself. Any remaining homogenized coal will be resealed and sent back to the sender.
In an electric kiln, pulverized coal samples will be ashed. After the process, they will be cooled to room temperature, jarred, put into a mixer-mill for agitation, and then be sent to a chemical laboratory for analysis.
8. Equipment cleaning
Once the prepared coal is sent off to another laboratory for analysis, the equipment used must be properly cleaned. The jaw crusher, vertical grinder, and work head and hood all need to be wiped down, soaked, and/or vacuumed to remove debris.
While there are different ways to sample coal prior to its analysis, it is typically done in eight steps: sample collection, grinding and route labeling, air drying, container cleaning and labeling, crushing and grinding, homogenization and splinting, ashing, and equipment cleaning. Knowing these steps, it makes it easier to know what the coal sampling process generally consists of.