pillar
pillar
The most easily oxidized coal is (). A: lignite coal B: bituminous coal C: lean coal D: anthracite coal
The most easily oxidized coal is (). A: lignite coal B: bituminous coal C: lean coal D: anthracite coal
It is a pillar ,or more corrctly a column.
It is a pillar ,or more corrctly a column.
Which of the following is not a common way for coal caving? ( ) A: Top caving coal in group sequence B: Top caving coal in single cycle sequence C: Top caving coal in multiple cycles in sequence D: Top caving coal in intervals of single cycle
Which of the following is not a common way for coal caving? ( ) A: Top caving coal in group sequence B: Top caving coal in single cycle sequence C: Top caving coal in multiple cycles in sequence D: Top caving coal in intervals of single cycle
The pillar shape that gives the greatest strength for the least weight is the（）.
The pillar shape that gives the greatest strength for the least weight is the（）.
The coal industry is running down as coal is gradually replaced by oil.( industry )
The coal industry is running down as coal is gradually replaced by oil.( industry )
The dry ash free volatile content of a coal is 7%, which is most likely to belong to (). A: Bituminous coal B: Anthracite C: Lignite D: Lean coal
The dry ash free volatile content of a coal is 7%, which is most likely to belong to (). A: Bituminous coal B: Anthracite C: Lignite D: Lean coal
The dry ash free volatile content of a coal is 47%, which is most likely to belong to (). A: Lignite B: Lean coal C: Anthracite D: Bituminous coal
The dry ash free volatile content of a coal is 47%, which is most likely to belong to (). A: Lignite B: Lean coal C: Anthracite D: Bituminous coal
( ) is not a real coal, but only a precursor. A: Anthracite B: Bituminous coal C: Lignite D: Peat
( ) is not a real coal, but only a precursor. A: Anthracite B: Bituminous coal C: Lignite D: Peat
Inthiscountry,coal electricity.
Inthiscountry,coal electricity.