Ladles are used to carry molten steel from the melting furnace to the ladle refining station or to the casting operation. These ladles must be preheated to minimize thermal shock and damage to the refractory lining and to reduce temperature drop in the ladle.
A covered ladle heating system consists of the following components: Ladle Lid, Sealing System and combustion control system. In some systems the lid is lowered onto the vertical ladle, in others the ladle is tilted horizontally and brought up against the fixed face of the ladle heater. The sealing system can be either a ceramic fiber seal or an air curtain that eliminates cold air induction at the ladle mouth. High Temperature Burner and Recuperators can be used to deliver the combustion to the ladle. The burner is designed to accept high temperature combustion air provided by a recuperator. The burner control incorporates a flame safety, temperature control and a gas train which delivers fuel to the burner. A temperature control system senses the ladle temperature and provides for turn-down of the burner for holding the temperature of the ladle. In some cases, the control also incorporates fuel air ratio control which prevents the burner from firing too rich or lean.
Ladle preheating systems use a gas burner with a high turn down ratio. Excess air sensors maintain fuel mix control. Variable geometry flame can be provided for different ladle shapes to provide even heating. Recuperators can provide up to 1000° preheat to the burner. Typical temperatures of these ladles are controlled at 1800 Deg F.
Most of these combustion systems used on these ladle preheaters are very old and lack safety equipment which adhere to the latest NFPA standards and codes. In addition to safety many customers struggle with these additional problem areas of these heaters:
Unable to light burner
Unable to shut down or start up the burner in a safe manner
Burner firing to rich or lean
Lack of Ladle temperature uniformity
Over-heating ladle refractory
Unable to ramp up temperature at a controlled rate for refractory curing
Lack of burner or system diagnostics
Loy Instrument has built and implemented a ladle preheater system at several Steel Mills consisting of Honeywell components which delivered the following results:
Reliable lighting and shutting down the burner in a safe manner
Optimizing the burner performance using a fuel-air ratio control system
Reduce energy bills and assuring ladle uniformity by firing the burner with the correct amount of air and gas mixture
Reduction in downtime due to operator and maintenance advanced diagnostic screen.
Advanced process controller enabling slow ramp up and tight control of temperature assuring correct curing of new refractory and prolonged ladle life.
Minimizing the risk of sending a ladle which is not up to temperature resulting in bad batches.
This solution incorporated Honeywell’s HC900 Hybrid Controller, RM7800 Series Flame Safety, Maxon Gas Train Components and Eclipse Thermjet Burner. With these components combined with Loy Instrument’s programming and combustion knowledge we were able to reduce our customers gas consumption of approximately $28,000.00 per month on each system. This system further resulted in $1,000,000.00 per year in gas savings for all five systems. Our customer now can enjoy less downtime, a more user-friendly system and a piece of mind that the system in safe!
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