Recovery boiler

SantaFeRecoveryBoiler

Svartlut 76

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EarlyTomlinsonRB

Black liquor nozzle

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NetheatingvalueBlackLiquor

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DrySolidsvsYear

Industrial boiler used in the pulp and paper industry

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A recovery boiler is a type of industrial boiler used in the pulp and paper industry. Its primary function is to burn black liquor, a byproduct of the kraft process, to generate steam and recover valuable chemicals used in the pulping process. The recovery boiler plays a crucial role in the chemical recovery cycle of the kraft process, making it an essential component in the production of paper and pulp.

History

The recovery boiler was invented by G.H. Tomlinson in 1934. Before its invention, the recovery of chemicals from black liquor was inefficient and hazardous. The introduction of the recovery boiler significantly improved the efficiency and safety of the chemical recovery process, leading to widespread adoption in the pulp and paper industry.

Operation

The recovery boiler operates by burning black liquor, which contains organic materials and inorganic chemicals. The combustion process generates heat, which is used to produce steam. This steam can be used for various purposes, including powering turbines to generate electricity and providing process heat for the mill.

The inorganic chemicals in the black liquor, primarily sodium compounds, are recovered in the form of a molten smelt. This smelt is then dissolved in water to form green liquor, which is further processed to regenerate the chemicals used in the kraft process.

Components

A typical recovery boiler consists of several key components:

• Furnace: The main combustion chamber where black liquor is burned.
• Superheater: A set of heat exchangers that increase the temperature of the steam produced in the boiler.
• Economizer: A heat exchanger that preheats the feedwater entering the boiler, improving overall efficiency.
• Air system: Supplies the necessary air for combustion.
• Smelt spouts: Channels through which the molten smelt is discharged from the furnace.

Advantages

The recovery boiler offers several advantages:

• Efficient recovery of chemicals, reducing the need for fresh chemical inputs.
• Generation of steam and electricity, contributing to the energy needs of the mill.
• Reduction of environmental impact by minimizing waste and emissions.

Challenges

Despite its advantages, the recovery boiler also presents some challenges:

• High capital and maintenance costs.
• Potential for severe corrosion and fouling due to the harsh conditions inside the boiler.
• Safety risks associated with handling and processing molten smelt.

See also

• Kraft process
• Black liquor
• Pulp and paper industry
• Chemical recovery
• Boiler

Related pages

• Kraft process
• Black liquor
• Pulp and paper industry
• Chemical recovery
• Boiler