Complex sentence: However, the coke is of wildly varying strength and ash content and is generally considered unsaleable except in some cases as a thermal product--as it has lost its volatile matter it has lost the ability to be coked again.
Split into simpler sentences: However, the coke is of wildly varying strength and ash content and is generally considered unsaleable except in some cases as a thermal product. As it has lost its volatile matter, it has lost the ability to be coked again.