The air to airheat exchanger is technically the simpliest as a recovery energy module bot the most flexible in energy recovery possibility as well, infact it use the hot air coming from the RTO (before it is released into atmosphere) to heat some new air useful for plant's services or for the plant itself.
Some example of use are the indoor ambient heating or the hot air re-entering for the process air pre-heating in the production cycle, depending on the factory needs.
Your pollutant is a resource
This solution allows to convert the heat from purification process into energy, at zero-cost. Reduction of energy consumption brings instant economics advantages and reduce environmental pressure too, as required by legislations.