Reduce furnace CO2 emissions with a heat exchanger

Applied by


Installing a Heat Recovery Tower recovers generated heat and reduces HFO (heavy fuel oil) consumption, reducing costs and with no impact on production 


Unilever’s Unisola Plant, located in El Salvador, is the detergent powder sourcing unit for all its Central America & Caribbean markets. One of the main pieces of equipment in the detergent process is the Spray Drying Tower, in which hot air is generated by means of a heavy fuel oil (HFO) fueled furnace. Some 29.7% of the heat was previously lost in exhaust gases, after slurry moisture content (27 – 30%) was reduced to 3%. This final temperature of the exhaust gases was 82°C. The company therefore sought a more efficient solution to reduce waste and HFO consumption. 

Additionally, Unilever plans to replace costly HFO with biodiesel to transition to 100% renewable heat at the factory (local HFO costs are dependent on international crude oil prices).  


In 2020, by installing a plate-to-plate heat exchanger, Unilever was able to recover the waste heat and return it to the Spray Drying Tower, ensuring it does not go to waste. This also reduces the amount of HFO consumed. The company used two turbines for clean air and two heat exchangers. With civil reinforcement, the total weight for the heat exchangers was 5 tonnes. 

Image 1: Heat recovery tower


Climate impact

Targeted emissions sources 

Scope 1 emissions

Decarbonization impact 

GHG emissions and energy reduction due to reduced use of HFO 

  • Impact on GHG emissions: -550 tonnes CO2/year 

  • Annual energy saving: -9,000 GJ/year 

Business impact


Annual financial savings: €125,000/year 

No impact on production 


Investment required: €385,000


Stakeholders involved

Solution provider: Heat exchanger supplier, Gupex

Company functions: Manufacturing, Procurement, Engineering, Global Sustainability Team 

Key parameters to consider

Technical considerations 
  • Heat exchanger type 

  • Building structural analysis for additional weight 

  • Chemical and physical characterization of exhaust gases 

  • CIP (clean in place) for heat exchangers, water reuse in the detergent process 

  • Internal pressure of the heat exchanger 

  • Dew point at the heat exchanger exhaust

Main challenges   
  • Dust accumulation inside the heat exchanger and the cleaning process

  • Lightest possible heat exchanger was needed and suitable chemical properties of the construction material to prevent early deterioration