与无预选的浮选工艺比较，预选工艺可大大提高资源净价值，产值利税率可从9.77%提高到19.86%。
Through preconcentration , there is an great increase of the net value of the resources over the flotation process with no preconcentration , and the ratio of profit to output value increases from 9.77 % to 19.86 % .
产值利税率