Raw coal is processed in four steps: hand-pick the obvious rock at the face, screen the rest by size, wash only coal with too much stone, and store it dry, covered and in small piles. Each step trades labour against heat delivered per kilogram, and the last one decides whether the stockpile keeps or catches fire.
Part of Coal Surface Mining
The route coal takes from the face to the stove: sorting, grading, washing and weather-protected storage, with the reason for each step.
Each Step Removes A Specific Loss
- Picking removes stone you would otherwise haul, store and shovel out as ash.
- Screening by size puts lump coal in the stove and fines in the forge or briquettes, because the two burn differently (see Sorting & Grading).
- Washing separates coal from fine rock and clay that picking cannot reach (Washing), and is worth its labour only when the ash is high.
- Storage keeps the coal dry and cool (Storage & Weather Protection).
When To Skip A Step
A clean coal needs no washing. A small household supply needs no screening plant: a hand-picking and a rough grate do. The point is to match effort to the ash you measure, not to process out of habit. Use the ash-weighing test in Coal Types & Quality to decide.
Worked Example: The Cost Of Rock You Do Not Pick
Inputs: the parent’s household need of 4-8 t of bituminous coal a year; rock content 10% by weight of what is hauled; rock left in the load.
- Rock hauled = 4 × 0.10 = 0.4 t to 8 × 0.10 = 0.8 t a year.
- That is 0.4-0.8 t you carry, store, load into the stove and carry out again as ash, with no heat from it.
Picking at the face is the cheapest place to remove it, because you are already handling each lump once.
Common Mistakes
- Washing everything. It is wasteful on clean coal, and the wet coal must then be dried.
- Piling unsorted coal. Fines and dust in a pile reduce air flow, trap heat and promote heating.
- Storing wet. Wet coal is harder to light and smokier, as the parent notes.
Safety
Handling makes dust, and stored coal can ignite
Sorting and screening throw fine dust: work wet, upwind, and with a respirator. Stored coal can heat itself and burn without any outside flame; build small piles and check them.
What’s Next
- Learn next: Sorting & Grading — the first processing step
- Combine with: Burning Coal Effectively — where the processed coal goes