鲁尔煤田1957年共有123个烟煤洗选厂,其平均生产能力为315吨/时。1967年减至71个选煤厂,而其平均生产能力增至535吨/时。到1972年,据估计将进一步减至56个选煤厂,但其平均生产能力在15年内却要增加一倍多。这就很容易看出一 There were a total of 123 bituminous coal washing plants in Ruhr Coalfield in 1957 with an average capacity of 315 tons / hour. It was reduced to 71 coal preparation plants in 1967 and its average production capacity increased to 535 tons / hour. By 1972, it is estimated to be further reduced to 56 coal preparation plants, but its average production capacity more than doubled in 15 years. It is easy to see one