Aluminum Industry WHR

Aluminum production is one of the high energy consumption industries in the world in addition to its high impact on the carbon footprint. One ton of aluminum production needs four tons of bauxite and about two tons of carbon, leaving behind a five tons of solid and gas waste. However, waste heat and solid utilization to produce power would increase this industry sustainability. The waste heat recovery (WHR) technologies involved indirect heat to power (electricity) conversion using organic Rankine cycle (ORC) technology and direct heat transfer using heat exchanger technologies. The direct heat exchange can be used for preheating the metal scrap before melting or to homogenize the aluminum billets temperature as a process required to remove the billets internal stresses. It does not need high capital cost and plant modifications, it just needs a heat exchange compartment and hot metal handling tools.

The indirect conversion for utilizing WHR to produce power needs higher capital cost; however, it produces electricity the can be used for many applications in the plant with minimal operation cost because it does not need fuel supply. Instead the waste heat will be utilized as a heat source. Due to the nature of flue gas fluctuation in temperature and flow rates, a thermal storage is needed for smooth ORC operation.

Dr. Mohamed Ibrahim Hassan Ali has done a comprehensive WHR projects in aluminum and steel industries to recover heat from the cast hose furnaces and the smelter potline. The following figures illustrate some results from his team work for the WHR for indirect and direct conversion. Figure 1 shows the estimated power production form one furnace WHR, Figure 2 shows the metal scrap preheating utilizing the WHR from 2 furnaces, and Figure 3 shows a novel system schematic for producing electricity from the smelter potline flue gas and potshell waste heat recovery.

Figure 1. Waste heat recovery utilization for Power generation from cast house furnaces.


Figure 2. Waste heat recovery utilization for metal scrap preheating


Figure 3. Waste heat recovery utilization for Power generation from the smelter potline.




Steel Industry WHR

Waste heat recovery in steel manufacturing involves various high-temperature processes, such as smelting, refining, remelting, and casting, which release a significant amount of heat into the surrounding environment. This waste heat can be harnessed and used to generate power, heat, or power/heat cogeneration, improving the overall efficiency of the steel making operations and minimizing energy consumption and carbon footprint. Waste heat recovery systems in steel industries typically involve the use of heat exchangers or boilers to capture and transfer the waste heat to a medium, such as water or steam. This recovered heat can then be utilized for various purposes in the steel plant, including electricity generation, preheating of combustion air for the fossil fuel combustion based furnaces, or providing heat for other industrial processes like steam generation for heating and reforming processes. By implementing waste heat recovery technologies, steel industries can reduce their energy costs, lower greenhouse gas emissions, and improve overall sustainability. Some common methods used for waste heat recovery in steel industries include:

  • Steam Rankine Cycle: This system involves passing the waste heat through a heat exchanger to generate steam, which is then used to power a turbine and produce electricity.
  • Organic Rankine Cycle (ORC): In this process, an organic working fluid with lower boiling point than water is used to capture the waste heat. The fluid evaporates at the low temperature waste heat, driving a turbine and producing electricity.
  • Heat Recovery Steam Generators (HRSG): These systems recover waste heat from exhaust gases produced by steel furnaces and use it to generate high-pressure steam, which can be used for power generation or other industrial processes.
  • Air preheating remunerators for preheating combustion air.

Research projects in steel WHR at KU leaded by Dr. Mohamed Ibrahim Hassan Ali covered the electric arc furnace (EAF) and direct iron reduction furnace (DRI). Figure 4,5,6 show a schematic diagram for the DRI/EAF with WHR, temperature and flow fluctuation of the EAF flue gases, and the estimated power generation using ORC.


Figure 3. Waste heat recovery scheme in DRI/EAF integrated system.


Figure 5. EAF furnace temperature and flow fluctuations that needs thermal storage.


Figure 6. Estimated power production utilizing Arc furnace waste heat in ORC.