The changes of ash fusion point of coal blending are not the relationship of simple additivity of ash fusion point for two blended coals but that of non-linearity.

配煤灰熔点的变化不是两种单煤灰熔点简单的加和关系，而是非线性的关系，配煤灰熔点与煤灰组成之间也有很大的关系。

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Hydropower is clean, from the point of view of greenhouse-gas emissions, but most of the easy alternatives, notably coal, are dirty.

从温室气体排放量的角度来看，水力发出的电力是属于环保型的，但是许多容易被选择的资源却具有污染性，特别是煤。

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Cleaning coal of its greenhouse gas byproduct is a widely discussed idea but at this point unavailable at a commercial scale.

清除煤燃烧时释放的温室气体早就成为人们谈论的话题，但是直到目前为止还无法达到商业规模。

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That is the point of the National Coal Mining Museum in Overton, about 13 miles south-west of Knottingley, on the site of the former Capstone colliery.

ECONOMIST: Coal

Advocates of federal regulation point to the case of coal mining, which Congress regulates based on its national importance.

WSJ: Should Fracking Be Regulated by the Feds or the States?

With respect to clean coal technology, it is not possible at this point to completely eliminate coal from the menu of our energy options.

WHITEHOUSE: Your Interview with the President