石墨矿开采后的选矿工艺一直是选矿行业的难题。
Graphite ore mining of mineral processing technology is always after processing industry of difficult problems.
矿井水资源化是在解决煤炭产区严重缺水和矿井水污染环境这两个困扰煤炭行业的难题的基础上提出的。
The utilization of mine water is put forward based upon the solution to serious lack of water in mining areas & mine water polluting environment, two difficult problems that trouble coal mining.
这是一个难题，因为这些问题不应该被限制在某个特定的行业。
This is a problem, because these concerns shouldn't be tied to a particular industry.
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