Evaluating Heat Transfer Conditions in a Plasma-Heated Rotary Kiln for Cement Production

Area of Science:

• Materials Science
• Chemical Engineering
• Plasma Physics

Background:

• Cement production requires high temperatures (1450 °C), traditionally met by fuel combustion with radiation-dominated heat transfer.
• Replacing flame with thermal plasma presents heat transfer challenges due to the absence of radiating fuel particles.

Purpose of the Study:

• To evaluate the feasibility of using electrically generated thermal plasma as a heat source in a rotary kiln for cement production.
• To model and analyze heat transfer conditions in a plasma-heated rotary kiln.

Main Methods:

• Modeling heat transfer in a demonstration-scale rotary kiln heated by an 8-MW_el thermal plasma.
• Estimating plasma temperature profiles using measurements from a 50 kW_el carbon dioxide plasma torch.
• Examining the effects of operational and dimensional parameters on heat transfer.

Main Results:

• Plasma heating significantly alters heat transfer dynamics compared to conventional combustion.
• Tilting the plasma towards the bed enhances convective heat transfer.
• Particle injection into the plasma-heated gas improves radiative heat transfer.

Conclusions:

• A combination of tilting the plasma and injecting particles into the plasma-heated gas is the most effective strategy.
• This combined approach shows promise for increasing heat transfer to the cement bed material in plasma-heated kilns.