Glass Conditioning Technology
Introduction
Zedtec Ltd., part of the TECO Group of companies, has been at the forefront of glass conditioning since 1983. Our forehearth technology had been developed over a number of years by former sister companies Hotwork and Zedmark Refractories with Zedtec being formed specifically to provide forehearth and glass conditioning solutions.
The Zedtec technologies discussed in this article below all contribute to achieving what customers appreciate most from our working ends and forehearths:
- Forehearth, Refiner and Mathematical Emulator (FRAME) mathematical sizing calculations
- Higher pull for a given forehearth length
- Reduced length of forehearth for a given pull
- Ability to delay cooling to minimise head loss
- Good glass conditioning
- Excellent thermal homogeneity at the spout or rolling machine lip stone
- Greater production flexibility
- Quick job changes and less production downtime
- Good temperature control
- Reliability
- Minimal operator maintenance required
- Reduced defects and production issues
Rapid Cool Technology
Zedtec’s rapid cool technology is the most effective cooling technology available on the market today. This technology is normally incorporated in one or two forehearth cooling zones where cooling air is introduced up to 700 m3/hr using a unique arch block design for efficient center line cooling. The basic physical operation of cooling is to introduce cooling air down the central flue channel and allow this to enter the combustion chamber, to cool the central area of the glass stream. This cooling air now removes heat from the superstructure and central glass stream and thus heats and expands. This heated air then flows through the side flue channels and exits through the dampers, now acting as vents as seen in Figures 2 & 3.
This technology allows for increased pulls for a given forehearth length (as when increasing pull requirements at rebuild), greater production flexibility and quicker job changes.
Figure 2: CFD model of flows
Air Damper Units
Air dampers control the combustion chamber pressure on the superstructure of forehearths and working ends. Zedtec utilizes a series of internal concentric air jets to create a pressurised air curtain. This unique design allows for no moving mechanical components on the superstructure of the forehearth (as opposed to cumbersome mechanical levers and linkages), minimising maintenance requirements.
Low Forward Velocity (LFV) Burners
LFV burners are incorporated in the conditioning zone and ensure the energy release is local to the outside of the glass stream to help achieve excellent thermal efficiency as the glass enters the spout or lip stone. These burners produce a short radiant flame throughout their turndown range to focus the heat down the sidewall channel block to compensate for the heat losses through the side refractory, while not supplying a significant heat delivery to the bulk of the glass on the centreline. Note: LFV burners use the same 114mm centres as traditional burners.
Hot Spot Burners
Zedtec’s hot spot burner technology provides a means of either heating or cooling the glass. The burners are roof mounted and produce a luminous ball of heat that provides direct radiation on to the surface of the glass and secondary radiation onto the glass via the arch and sidewall blocks. This same burner can also be used for cooling by stopping the gas flow to it and utilizing only the combustion air.
In cooling mode, air is passed through the burner that generates a spiraling effect to the air flow prior to entering the combustion chamber. This cold dense air then removes heat from the surface area of the arch and sidewall blocks which then removes heat from the glass via radiation as they become a black body receiver.
Figure 5: Example of hot spot burner incorporated into a crown
Some specifications and advantages are:
- Raise the glass temperature by up to 50 deg. C per zone
- Cool the glass temperature by 100 deg C per zone
- No moving mechanical parts on the superstructure
- Very low maintenance
- Use in frit feed sections, working ends and alcoves
- No re-boil on any color of glass
Duplex Governor Combustion System
Zedtec is the industry pioneers for the development of high-pressure combustion systems. Our combustion skid mounted duplex governor combustion system allows greater turn down ratio from high to low fire and consequently an improved and more economical control of energy released into the glass. The system prevents the risk of flashbacks and eliminates carbon build up on the burner nozzles meaning regular burner cleaning is not necessary.
Summary
The technical innovations shown and described in this article have resulted in forehearths and working ends that are at the forefront of the glass industry. For over 30 years, these innovations have put Zedtec at the forefront of the glass furnace front end with thousands installed worldwide. The proof is in the many satisfied repeat customers - just ask one!
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