Recovery boiler: Difference between revisions

Latest revision as of 00:47, 10 December 2024

A recovery boiler is a crucial component in the pulp and paper industry, used primarily to recover chemicals and energy from black liquor, a byproduct of the kraft process. The recovery boiler plays a vital role in the chemical recovery cycle, enabling the recycling of chemicals and the generation of steam and electricity.

History[edit]

The development of the recovery boiler was a significant advancement in the kraft process, allowing for more efficient chemical recovery and energy production. The first recovery boilers were developed in the early 20th century, with significant improvements in design and efficiency occurring over the decades.

Function[edit]

The primary function of a recovery boiler is to combust black liquor, which contains organic material and inorganic chemicals. The combustion process recovers the inorganic chemicals as a smelt, which is then processed to regenerate the cooking chemicals used in the kraft process.

Combustion Process[edit]

Black liquor is sprayed into the recovery boiler through specialized nozzles, such as the one shown in

. The liquor is burned in the furnace, releasing heat that is used to produce steam. This steam can be used to generate electricity or provide process heat for the mill.

Chemical Recovery[edit]

During combustion, the inorganic chemicals in the black liquor are reduced to a molten smelt, which is collected at the bottom of the boiler. This smelt is then dissolved in water to form green liquor, which is further processed to regenerate white liquor, the active cooking chemical in the kraft process.

Energy Production[edit]

The recovery boiler is a significant source of energy for a pulp mill. The heat generated from burning black liquor is used to produce high-pressure steam, which can drive turbines to generate electricity. This process is illustrated in the

File:NetheatingvalueBlackLiquor.jpg

Net heating value of black liquor

.

Environmental Impact[edit]

Recovery boilers help reduce the environmental impact of the kraft process by recycling chemicals and reducing the need for fresh chemical inputs. They also reduce emissions by efficiently burning organic material in black liquor.

Challenges and Innovations[edit]

Recovery boilers face challenges such as corrosion, fouling, and the need for efficient combustion. Innovations in materials, design, and control systems continue to improve the efficiency and longevity of recovery boilers.

Also see[edit]

References[edit]

Smook, G. A. (1992). Handbook for Pulp & Paper Technologists. Angus Wilde Publications.
Adams, T. N., & Frederick, W. J. (1988). Kraft Recovery Boiler Physical and Chemical Processes. American Paper Institute.

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@@ Line 1: / Line 1: @@
-[[File:SantaFeRecoveryBoiler.JPG|thumb]] [[File:Svartlut 76.jpg|thumb]] [[File:EarlyTomlinsonRB.gif|thumb]] [[File:Black liquor nozzle.JPG|thumb]] Recovery Boiler
+{{Infobox industrial equipment
+| name = Recovery Boiler
+| image = [[File:SantaFeRecoveryBoiler.JPG|thumb|A recovery boiler in operation]]
+| caption = A recovery boiler in operation
+| uses = Recovery of chemicals and energy from black liquor
+| industry = Pulp and paper industry
+}}
-A recovery boiler is a crucial component in the chemical recovery process of a kraft pulp mill. It is designed to burn black liquor, a byproduct of the pulping process, to generate steam and recover chemicals for reuse in the pulping process. This article provides an in-depth look at the design, operation, and significance of recovery boilers in the pulp and paper industry.
+A '''recovery boiler''' is a crucial component in the [[pulp and paper industry]], used primarily to recover chemicals and energy from [[black liquor]], a byproduct of the [[kraft process]]. The recovery boiler plays a vital role in the chemical recovery cycle, enabling the recycling of chemicals and the generation of steam and electricity.
-== Design and Components ==
+==History==
+The development of the recovery boiler was a significant advancement in the kraft process, allowing for more efficient chemical recovery and energy production. The first recovery boilers were developed in the early 20th century, with significant improvements in design and efficiency occurring over the decades.
-A recovery boiler consists of several key components that work together to achieve its dual purpose of energy generation and chemical recovery:
+==Function==
+The primary function of a recovery boiler is to combust black liquor, which contains organic material and inorganic chemicals. The combustion process recovers the inorganic chemicals as a smelt, which is then processed to regenerate the cooking chemicals used in the kraft process.
-=== Furnace ===
+===Combustion Process===
-The furnace is the primary chamber where black liquor is combusted. It is lined with water-cooled tubes that absorb heat from the combustion process to generate steam. The furnace operates at high temperatures to ensure complete combustion of the organic material in the black liquor.
+Black liquor is sprayed into the recovery boiler through specialized nozzles, such as the one shown in [[File:Black_liquor_nozzle.JPG|thumb|A black liquor nozzle]]. The liquor is burned in the furnace, releasing heat that is used to produce steam. This steam can be used to generate electricity or provide process heat for the mill.
-=== Superheater ===
+===Chemical Recovery===
-The superheater is a set of tubes located in the upper part of the boiler. It heats the steam produced in the furnace to a higher temperature, increasing its energy content and efficiency for use in turbines.
+During combustion, the inorganic chemicals in the black liquor are reduced to a molten smelt, which is collected at the bottom of the boiler. This smelt is then dissolved in water to form green liquor, which is further processed to regenerate white liquor, the active cooking chemical in the kraft process.
-=== Economizer ===
+==Energy Production==
-The economizer is a heat exchanger that preheats the feedwater entering the boiler using the flue gases exiting the furnace. This process improves the overall efficiency of the boiler by reducing the energy required to convert water into steam.
+The recovery boiler is a significant source of energy for a pulp mill. The heat generated from burning black liquor is used to produce high-pressure steam, which can drive turbines to generate electricity. This process is illustrated in the [[File:NetheatingvalueBlackLiquor.jpg|thumb|Net heating value of black liquor]].
-=== Air System ===
+==Environmental Impact==
-The air system supplies the necessary oxygen for combustion. It typically includes primary, secondary, and tertiary air supplies to ensure complete combustion and control of emissions.
+Recovery boilers help reduce the environmental impact of the kraft process by recycling chemicals and reducing the need for fresh chemical inputs. They also reduce emissions by efficiently burning organic material in black liquor.
-=== Smelt Spouts and Dissolving Tank ===
+==Challenges and Innovations==
-The smelt spouts are located at the bottom of the furnace and direct the molten smelt into a dissolving tank. The smelt contains inorganic chemicals that are recovered and recycled back into the pulping process.
+Recovery boilers face challenges such as corrosion, fouling, and the need for efficient combustion. Innovations in materials, design, and control systems continue to improve the efficiency and longevity of recovery boilers.
-== Operation ==
-The operation of a recovery boiler involves several critical steps:
-. '''Black Liquor Combustion:''' Black liquor is sprayed into the furnace, where it is combusted. The heat generated is used to produce steam.
-. '''Steam Generation:''' Water in the boiler tubes absorbs heat from the combustion process, converting it into steam.
-. '''Chemical Recovery:''' The inorganic chemicals in the black liquor are recovered as smelt, which is dissolved in water to form green liquor. This is further processed to regenerate white liquor for the pulping process.
-. '''Emission Control:''' Modern recovery boilers are equipped with systems to control emissions of particulates, sulfur compounds, and nitrogen oxides.
-== Importance in the Pulp and Paper Industry ==
-Recovery boilers are vital for the economic and environmental sustainability of kraft pulp mills. They allow for the efficient recovery and reuse of chemicals, reducing the need for fresh chemical inputs. Additionally, the energy generated from burning black liquor contributes significantly to the energy needs of the mill, often making it energy self-sufficient.
-== Challenges and Innovations ==
-Recovery boilers face challenges such as corrosion, fouling, and emissions control. Innovations in materials, design, and control systems continue to improve their efficiency and longevity. Advanced monitoring and control technologies are being developed to optimize combustion and reduce emissions.
-== Also see ==
+==Also see==
 * [[Kraft process]]
 * [[Black liquor]]
 * [[Pulp mill]]
 * [[Chemical recovery]]
-* [[Steam turbine]]
-{{Pulp and Paper Industry}}
+==References==
-{{Boiler Technology}}
+* Smook, G. A. (1992). ''Handbook for Pulp & Paper Technologists''. Angus Wilde Publications.
+* Adams, T. N., & Frederick, W. J. (1988). ''Kraft Recovery Boiler Physical and Chemical Processes''. American Paper Institute.
+{{Pulp and paper industry}}
+{{Industrial equipment}}
-[[Category:Pulp and Paper Industry]]
+[[Category:Pulp and paper industry]]
-[[Category:Boilers]]
+[[Category:Industrial equipment]]