7种煤煤质
coal quality of seven coal samples
传统条形煤场
conventional oblong coal yard
方形全封闭煤场
totally enclosed quadrate coal yard
封闭式圆形煤场
the enclosed circular coal yard
锅炉房煤场
coal yard of boiler house
井筒与工业广场煤柱
Shaft and Industry Square Pillar
垃圾场煤气发动机简图
landfill engine schematic