Complex sentence: In 1906, the "Commonwealth Oil Corporation" started construction of a shale oil plant at Newnes, which also utilized Pumpherston retorts, commissioned in 1911 but closed after few months due to technical problems.
Split into simpler sentences: In 1906, the "Commonwealth Oil Corporation" started construction of a shale oil plant at Newnes. The new plant also utilized Pumpherston retorts, commissioned in 1911, but closed after few months due to technical problems.