Exploiting the value of waste heat

The utilisation of excess heat sources exhibits significant potential for the ongoing energy transition and is ultimately a lever to optimise operational expenses.

In many cement plants, large amounts of unused thermal power are still discharged into the atmosphere. The main sources for said unused thermal power are the hot gases exhausted from the PH/calciner kilns and the unrecovered vent air from the grate clinker coolers. The hot gases from the kiln are still mainly cooled via water quenching in gas conditioning towers for the proper operation of raw mill and filters. As a result, the temperature level of the available thermal power goes down, making it unavailable for efficient usage. One example of this could be electric power production via an organic Rankine cycle (ORC) turbine.

Regarding the waste heat generated in the aforementioned clinker cooler, either hot operated electrostatic precipitators (ESPs) or bag filters are used for emissions reduction. In case of an ESP, the hot gas usually goes directly to the stack at a minimum 300°C without heat recovery. In the case of a bag filter installation, air-gas coolers are a widely used solution that dissipate the thermal energy into the atmosphere.

There are several ways to avoid this wastage and utilise the thermal power in the different gas streams in a cement plant. This article will highlight one possibility.

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Read the article online at: https://www.worldcement.com/special-reports/08112023/exploiting-the-value-of-waste-heat/