sodium bicarbonate

Dry sodium bicarbonate (NaHCO₃) 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 (Na₂CO₃ and Na₂O) produced by the thermal decomposition of sodium bicarbonate and SO₂ in the flue gas to achieve the removal of sulfur. Here's a detailed description of the process:

Process principle

l Thermal decomposition reaction:

Sodium bicarbonate decomposes at 150-250°C into more active sodium carbonate (Na₂CO₃), water, and CO₂:

2NaHCO₃→Na₂CO₃+H₂O+CO₂

2NaHCO₃→Na₂CO₃+H₂O+CO₂

When further heated, Na₂CO₃ is converted to sodium oxide (Na₂O).

l Desulfurization reaction:

The Na₂CO₃/Na₂O reacts with SO₂ and O₂ and H₂O in flue gas to form sodium sulfate (Na₂SO₄) and sodium sulfite (Na₂SO₃):

Na₂CO₃+SO₂+½O₂→Na₂SO₄+CO₂

Na₂CO₃+SO₂+½O₂→Na₂SO₄+CO₂

Process flow

l Raw material pretreatment:

n NaHCO₃ needs to be ground to a fine powder (usually 10-20 μm) to increase the specific surface area to improve the reaction efficiency.

n If baking soda (commercial NaHCO₃) is used, it may need to be dried to avoid agglomeration.

l Injection system:

n 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).

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

l Reaction Section:

n The flue gas is in full contact with the NaHCO₃ powder in the flue, SO₂ is absorbed, and the reaction time is ≥ 1 second.

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

l By-product collection:

n The reaction products (Na₂SO₄, Na₂SO₃ and unreacted Na₂CO₃) are captured with flue gas entering the dust collector (such as bag dust collector).

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

Key process parameters

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

l Stichiometric ratio: Typically the Na/S molar ratio is 1.5-2.0, ensuring efficient SO₂ removal (up to 95% or more).

l Stay time: ≥ 1 second to ensure adequate response.

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