Increase Float Glass Furnace Output Without Enlarging Melting Area

Introduction

In today’s competitive float glass industry, increasing furnace productivity without expanding the physical footprint has become a key challenge. A recent simulation study by Burçin Gül Arslanoğlu from Şişecam, a leading Turkish glass manufacturer, explores an innovative approach: optimizing glass melt depth and the immersion depth of deep throat barriers to improve the melting capacity of large float glass furnaces—without significantly altering the melting area.

This case study provides valuable guidance for glass producers looking to enhance performance, energy efficiency, and glass quality, all while moving toward decarbonized operations.

1. Glass Melt Depth 

Why Glass Depth Matters

Glass melt depth is a critical parameter in float glass furnace design. It directly impacts:

• Heat transfer and convection behavior

• Product quality

• Furnace melting capacity

• Energy efficiency

Traditionally, increasing the melting surface area or operating the furnace at lower pull rates are ways to ensure quality. However, adjusting the glass depth offers better performance-to-investment ratios and is more energy-efficient.

Key Findings from CFD Modeling

Using a combined glass bath and combustion space CFD model, the study explored three furnace variants:

• Variant 1: Flat bottom with standard glass depth

• Variant 2: Flat bottom with 25 cm deeper melt

• Variant 3: Stepped bottom in the clarifying zone to reduce local depth

Benefits of Deeper Glass Melt

• Enhanced convection improves heat transfer

• Longer residence time in the front loop promotes early-stage melting

• Improved melt homogenization and quality

• Greater time available for the clarifying process

Interestingly, a 25 cm increase in glass depth raised the bottom temperature by ~10°C under the same fuel load. This is due to stronger convection transferring more energy from the combustion space to the melt.

The Limits of Depth: Avoiding Diminishing Returns

If depth increases excessively:

• Radiation heat transfer reduces

• Bottom temperatures may decline

• Stagnation zones form, decreasing quality

Hence, glass depth must be carefully balanced to avoid glass flow issues or non-uniformity.

Quantified Impacts on Glass Quality

• Glass velocity decreased by 14% with stepped-bottom design

• Critical particle ratio dropped by ~0.5%, improving uniformity

• Particle exit time increased by 2 hours, aiding in better refining

These insights demonstrate how glass depth optimization can directly lead to higher pull rates and improved product quality.

2. Deep Throat Water-Cooled Barriers

Function of the Throat Barrier

Deep water-cooled barriers (also called throat coolers or blockers) serve as physical flow controllers. By strategically adjusting the immersion depth, they:

• Delay glass flow from the melting end to the working end

• Increase residence time

• Promote better melt homogenization

• Reduce energy losses

Simulation-Based Insights

With deeper throat barrier immersion:

• Glass flow into the working end decreased, lowering outlet temperatures by up to 35°C

• The hot spot moved forward by 2.4 meters, concentrating heat in the melting area

• Pull rate increased by 10% with just 12 cm deeper immersion

Considerations for Furnace Operators

• Adjust cooling air supply as the outlet temperature drops

• Evaluate temperature and velocity profiles together

• Increase stirrer blade depth accordingly to maintain melt uniformity

Positive Impact on Residence Time

Deeper immersion extends the glass particle residence time, particularly in the clarifying and homogenization zones, contributing to superior optical and structural quality in the final glass product.

3. Conclusion

This simulation study demonstrates how optimizing glass melt depth and throat barrier immersion can significantly boost a 1200 TPD float glass furnace’s melting capacity—without increasing the physical size of the melting zone.

Key Takeaways

• Model-based furnace optimization supports higher pull rates and better glass quality

• Deep glass melt and throat barriers strengthen convection and thermal control

• Extended residence time leads to better clarification and fewer defects

Looking Ahead: Balancing Productivity and Decarbonization

As the global glass industry moves toward carbon neutrality by 2050, increasing productivity must align with sustainable practices. CFD modeling offers:

• Deep insights into heat transfer and flow behavior

• Scenario planning for design and operation

• Risk identification before physical upgrades

At Firebird Refractories, we believe that smart furnace design, guided by modeling and innovation, will lead the way in achieving both higher efficiency and lower environmental impact.

Need High-Performance Refractories for Float Glass Furnaces?

Explore our range of insulating firebricks, nano insulation boards, and advanced refractory solutions tailored for float glass applications.
👉 Visit us at: www.firebirdref.com
📩 Contact us for technical consultation and quotes.