Principal District and Sessions Judge C V Karthikeyan awarded the sentence to Purchase Manager T R Gopalrathnam and Fusaram Raj Purohit.
The court also imposed a fine of Rs 8 lakh on Gopalarathnam and Rs 7 lakhs on Purohit.
The case was that the had entered into a conspiracy and supplied sub standard coal to the mill for its use in the boilers in 1996.
Cases were registered against them under different sections of IPC and also under Prevention of Corruption Act.