아역청탄의 NPV값은 석유코크스와의 혼합이 20% 이상이 되어야 역청탄과 경쟁할 수 있을 것으로 평가되었다.
The NPV value of sub-bituminous coal was evaluated to be able to compete with bituminous coal when it was mixed with petroleum coke by 20% or more.