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 Sodium Bicarbonate Desulfurization

                            


Introduction

Dry sodium bicarbonate (NaHCO) desulfurization is an efficient flue gas desulfurization process, especially suitable for small and medium-sized boilers, waste incineration, glass kilns and other occasions. The core of the project is the reaction between the active sodium-based substances (NaCOand NaO) produced by the thermal decomposition of sodium bicarbonate and SOin the flue gas to achieve the removal of sulfur. Here's a detailed description of the process:


Process principle


Thermal decomposition reaction:


Sodium bicarbonate decomposes at 150-250°C into more active sodium carbonate (NaCO), water, and CO:

2NaHCO₃→NaCO+HO+CO
2NaHCO₃→NaCO+HO+CO

 


When further heated, NaCOis converted to sodium oxide (NaO).

Desulfurization reaction:


The NaCO/NaO reacts with SOand Oand HO in flue gas to form sodium sulfate (NaSO) and sodium sulfite (NaSO):

NaCO+SO+½O₂→NaSO+CO
NaCO+SO+½O₂→NaSO+CO

 


Process flow

Raw material pretreatment:

NaHCOneeds to be ground to a fine powder (usually 10-20 μm) to increase the specific surface area to improve the reaction efficiency.

If baking soda (commercial NaHCO) is used, it may need to be dried to avoid agglomeration.


Injection system:

The powder is sprayed into the flue by pneumatic conveying (usually in the flue section in front of the dust collector, temperature range 200-300°C).

The injection point needs to be optimized to ensure adequate mixing with the flue gas.

 
Reaction Section:


The flue gas is in full contact with the NaHCO
powder in the flue, SOis absorbed, and the reaction time is 1 second.

Reaction efficiency can be improved by flue design, such as increased turbulence.

By-product collection:


The reaction products (Na
SO, NaSOand unreacted NaCO) are captured with flue gas entering the dust collector (such as bag dust collector).

By-products can be used as industrial raw materials (such as glass manufacturing) or safely landfilled.

 


Key process parameters

Reaction temperature: The optimal range is 140-250
°C, too high will lead to sodium salt sintering and inactivation.

Stichiometric ratio: Typically the Na/S molar ratio is 1.5-2.0, ensuring efficient SOremoval (up to 95% or more).

Stay time: 1 second to ensure adequate response.

Flue gas humidity: An appropriate amount of moisture (5-10%) can promote the reaction, but too high can easily lead to equipment corrosion.


Advantage:

 
Simple equipment, no need for complex slurry systems, low investment.


It is suitable for renovation projects and occupies a small footprint.


Fast start-stop and suitable for intermittent operation conditions.


No wastewater is generated, and the by-products are dry and easy to treat.

 

Application scenarios

Industrial field: waste-to-energy incineration, glass kilns, ceramic kilns, biomass boilers, etc.


Applicable conditions: projects with medium and low sulfur coal flue gas, small flue gas volume or limited space.

 

Compare with other dry desulfurization

Comparison with limestone (CaCO
) dry method:


NaHCO
₃ is more reactive and has better desulfurization efficiency, but it is more costly.

Limestone requires higher temperatures (>800°C) and is suitable for circulating fluidized bed boilers.


Comparison with activated carbon adsorption:


Activated carbon can synergistically remove dioxins and heavy metals, but the regeneration is complex. The NaHCO
₃ process is simpler.

Dry sodium bicarbonate desulfurization has become the preferred technology in specific scenarios due to its flexibility and efficiency, especially suitable for the treatment of small and medium-sized pollution sources in areas with strict restrictions on wastewater discharge.



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