Glass furnaces are vital thermal equipment in glass plants. A single furnace can account for over 50% of the total fixed asset investment of an entire glass production line.
Since the invention of AZS electric furnace bricks, almost all furnace pool wall bricks have been manufactured from AZS refractories. In recent years, global shortages of raw materials, fuels, oils, electricity and more have led to surging AZS brick prices.
Now, AZS bricks make up over 50% of the total refractory materials used in a typical furnace. Furthermore, the working lifespan of AZS bricks directly determines the total operating cycle length of the furnace as a whole.
Therefore, it is critical to utilize AZS pool wall bricks effectively and maximize their working lifespans in order to optimize costs. Proper installation, maintenance and operation protocols are key to prolonging the service life of AZS refractories.
This article provides a comprehensive guide to best practices for maximizing AZS brick lifespans in glass melting furnaces.
Ways to Minimize Pool Wall Brick Deterioration
Lowering the operating temperature is one of the primary methods for extending the lifespan of pool wall bricks.
It is well known that decreasing the temperature helps mitigate erosion and enhances the durability of refractory bricks. However, different areas of the wall see varied conditions over time.
Thus, tailored cooling approaches are needed to achieve optimal effects for specific zones. A one-size-fits-all cooling technique will not maximize brick lifespans across the furnace.
Reasonable Forced Air Cooling Approach (Broad Scope Systematic Cooling)
The uppermost section of the pool wall (the top 270mm) sees the most erosion due to intense bubbling and convection in the superheated glass melt surface.
Rational forced air cooling is critical for this vulnerable zone. Strategically placed air ducts and fans must supply optimized air flow rates to match localized conditions.
Cooling air should be activated when the furnace reaches 250-300°C during firing and slowly ramped up as temperatures increase.
The outdated practice of delaying cooling until visible erosion occurs must be avoided. Cooling is most effective when started early and gradually increased to minimize thermal stresses from temperature differentials that can damage bricks.
With judicious cooling design and proactive operation, the lifespan of upper pool wall bricks can be significantly prolonged through the mitigation of excessive erosion.
Targeted Forced Air Cooling Procedure
AZS bricks typically last 3-5 years. In the later stages of furnace operation, after 2+ years, variations like internal voids, large firing gaps, or imperfect sealing can cause glass phase seepage in isolated spots. Targeted forced air cooling is an effective solution for these emerging issues.
In one furnace after 2 years and 3 months, seepage occurred at a corner expansion joint. At 2 years and 6 months, a large brick gap began seeping. By implementing focused, intense cooling points at the defects, the melt viscosity increased and brick temperature decreased, stopping the leaks. This localized cooling was maintained until the end of the campaign with no further issues.
Proactively applying concentrated cooling at weak points identified through monitoring can significantly extend brick lifespans. This real-time mitigation limits damage, avoiding premature teardowns.
Cooling Approach Combining Air and Water Spray
High erosion zones like the throat can be difficult to access and repair. Despite mitigation efforts like angled settling walls, intense mechanical and gas erosion still rapidly degrade exposed bricks. In one furnace, the throat cover bricks were unusable after just 2.5 years despite forced air cooling.
After relining, the throat was semi-insulated by encasing AZS bricks in a high alumina brick layer, avoiding direct water contact. A combined air and water mist approach was initiated, blending forced air with a controlled atomized fog.
This simple, stable cooling method significantly lowered brick temperatures without damage from water quenching. Ongoing monitoring ensured optimal water usage for maximum erosion mitigation. The partially insulated throat now lasts over 4 years – a major lifespan increase.
Targeted cooling innovations like air/water mist can drastically improve durability in vulnerable high-wear areas like the throat through close control of operating conditions.
Bath Cooling Technique
Immersion cooling is best suited to middle and upper pool wall sections in the late stages of a campaign after some insulation is added. With the exterior protected by backup bricks and steel plates, erosion progresses slower initially, requiring no cooling.
However, after the 3rd year post-relining, seepage began occurring at the top of the insulation-brick interface as the AZS refractories degraded. The direct water contact of immersion cooling is risky when insulation is present. Removing backup bricks is laborious and unsafe.
Instead, a bath of atomized water mist was directed precisely at the leaks. This was achieved by:
- Modifying a fuel oil spray nozzle into a wide 45° water atomizer using simple pressure and viscosity principles, optimizing it for water’s cooling properties.
- Mounting the atomizer 200-300mm above the wall at an upward angle, aligning the spray cone with the leak location for maximum impact.
Through pressurization and modulation, the water fog cooled the wall without dripping, avoiding unstable runoff. This compact, adaptable technique lowered brick temperatures with minimal water consumption and risk. The affected areas remained serviceable until the end of the campaign.
Immersive mist cooling is an innovative solution for targeted cooling of degraded zones when insulation limits other methods. Precise application controls brick erosion safely and effectively.
Using Support Brick
Installing auxiliary refractory bricks is a proven technique used by many plants to extend furnace lifespan. As campaigns progress, backup bricks are often added to high-wear areas like spout corners and tops.
Proper prep is critical – bricks, especially AZS, must be preheated before installation to prevent thermal shock cracks.
Ongoing monitoring and control is also key:
- 24/7 oversight ensures cooling systems function optimally.
- Strict regulation of furnace pressure and melt level.
- Careful control of cooling air volumes and water flow rates for maximum effect.
- Daily temperature measurements at fixed spots on the wall trace erosion over time.
- Gradual restarting of cooling after interruptions like power outages prevents spikes and damage.
Through vigilant tracking of conditions plus proactive auxiliary lining at susceptible spots, furnace run time can be safely prolonged past the expected refractory lifespan.