Clinker generally is much denser than coke, and, unlike coke, generally contains too little carbon to be of any value as fuel. It is also applied to the byproduct of combustion and heating by those who use anthracite or lignite coal-fired boilers.
Clinker tends to be more compact than coke and lacks sufficient carbon content to serve as a viable fuel source. Additionally, it is also utilized as a byproduct of burning and heating in systems that utilize anthracite or lignite coal-fired boilers.