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This degree project investigates the techno-economic feasibility of installing an additional water toair heat-exchanger before the existing humidifier at block 7 at Mälarenergi, which is a wood wastefired CHP plant producing 150 MW of thermal power. The aim of this project is to evaluate ifthe low grade heat from the scrubber water can be both recovered and used to preheat combustionair, which will reduce the dependency on auxiliary steam. A comparative modeling approachusing Ebsilon®Professional was used to compare both the current system at Mälarenergi and amodified design. The modified design incorporates an additional heat-exchanger with three differentefficiencies of 70%, 80%, and 90%. Operational data was provided at one-minute resolution andwas processed into ten-minute averages. The ten-minute averages was then simulated for both thereplicated system and the modified design, and run three separate times with different humiditylevels 30%, 50%, and 70% to reflect seasonal variations in the mixed indoor-outdoor combustionair. Economic performance was assessed using annual energy recovery and payback period wascalculated using estimated investment cost and auxiliary steam price provide by Mälarenergi. Thesimulation results of this study show that the additional heat-exchanger can on average increase theoutlet temperature by 1.4-1.8 ℃ depending on humidity and efficiency. While the annual recoveredheat is between 359-423 MWh depending on the humidity and efficiency. The higher humidity yieldsslightly higher heat recovery though the main contributing factor is the heat-exchangers efficiency,around 32% extra heat recovered between 70% efficiency and 90% efficiency. The economic analysisyields long payback periods, between 56-75 depending on how favorable the costs/revenues andtechnical efficiencies are. This study concludes that the proposed heat-exchanger improves thethermal performance of the plant, the low grade heat and nature of the current energy marketmakes the investment of the new system unfeasible.