Conventional Process
• In small Re-rolling mills the reheating furnace's are mostly fired by pulverised coal.
• The coal is transported upto burner using a centrifugal blower and passing through venture mixer.
• The system does not have any separate control on air hence, air / fuel ratio is not maintained.
• The excess air causes cooling effect in the furnace & excessive scaling due to oxidation.
• Most furnaces are found to have 85 – 90 % excess air.
• This can easily be measured using O2 analyzer.
Improvement
• The Recuperator is provided in flue duct between furnace & chimney.
• The blower air shall pass through Recuperator & will be pre heated upto 150-200 °C.
• This air shall now be used for carrying pulverised coal to burners.
• Mineral wool insulation on pipeline is a must to reduce heat loss from pipe surface.
• The isolation damper installed before Recuperator will hold heat in the furnace during shift change.
Reasons for not using Recuperator in Coal Fired Furnaces
• Blockage of Recuperator due to Coal dust which is very frequent.
• Back Pressure in furnace due to blockage of flue gas passage.
• Need Furnace shutdown for Recuperator cleaning.
• More time required for Recuperator Cleaning.
Advantages of therm process make improved designed Recuperator for Coal fired furnace
• Provision of periodic cleaning in position, no
need of removal.
• Operator friendly easy cleaning process.
• Less time required – ½ Hour for Recuperator cleaning.
• Any unskilled labour can perform cleaning.
• Better performance comparative to conventional
General advantages of Recuperator
• Coal consumption reduced by 8 – 10 %
• Faster furnace temperature.
• Reduced heating time.
• Reduced Scale loss due to controlled combustion Air.
• Normal Recuperator life is 4-6 years.
• About 50 % Coal dust is entrapped at Recuperator, Hence less pollution.
• Less hot Flue gas is released through chimney, hence environment friendly.
• Chimney life is increased.
