What Is Thermal Substitution Rate (TSR)?

Thermal substitution rate (TSR) is the percentage of a cement kiln's total thermal energy that is supplied by alternative fuels rather than by conventional fossil fuels such as coal and petroleum coke. It is measured on an energy (heat) basis, not a mass basis: a plant burning a mix where alternative fuels deliver 30% of the total heat input has a TSR of 30%, regardless of how many tonnes of each fuel it feeds [1][2]. TSR is the headline metric the cement industry uses to track its shift away from fossil fuel, and it is reported alongside the kiln's specific fuel consumption and emissions.

One disambiguation worth making early: in a cement context TSR always means thermal substitution rate, not total shareholder return (finance) or transfer success rate (telecoms). This piece covers the cement-kiln definition only.

If you are pushing thermal substitution rate up and finding that draft and combustion stability are harder to hold, the kiln seals at the inlet and outlet are often the limiting factor. Our engineering team works through false-air sources case by case, mapping each to a sealing and monitoring fix against your kiln's fuel mix and process profile. Contact us to walk through your configuration.