Ammonia Desulfurization (DeSOx)

Introduction

Ammonia desulfurization is a highly efficient wet flue gas desulfurization technology that uses ammonia (NH₃) or ammonia water as an absorbent to remove sulfur dioxide (SO₂) from flue gas through a chemical reaction. Its process principle and characteristics are as follows:

Process principle

Absorption reaction

SO₂ in flue gas reacts with ammonia or ammonia gas in the absorption tower to form ammonium sulfite ((NH₄)₂SO₃) or ammonium bisulfite (NH₄HSO₃):

SO₂+2NH₃+H₂O→(NH₄)₂SO₃
SO₂+2NH₃+H₂O→(NH₄)₂SO₃
SO₂+NH₃+H₂O→NH₄HSO₃
SO₂+NH₃+H₂O→NH₄HSO₃

Oxidation reaction

Under forced oxidation (air) conditions, sulfites are oxidized to ammonium sulfate ((NH₄)₂SO₄), which can be used as a fertilizer by-product:

(NH₄)₂SO₃+½O₂→(NH₄)₂SO₄

(NH₄)₂SO₃+½O₂→(NH₄)₂SO₄

Crystallization recovery

Ammonium sulfate solution is obtained through evaporation and concentration, crystallization, centrifugation and separation to obtain solid ammonium sulfate fertilizer.

Key process parameters

Absorption tower pH: usually controlled at 5.0~6.0 (too high increases ammonia escape, too low reduces desulfurization efficiency).

Liquid-gas ratio (L/G): about 3~5 L/m³.

Oxidation air volume: It is necessary to ensure that the ammonium sulfite is fully oxidized to ammonium sulfate.

Technical advantages

High desulfurization efficiency: up to 95%~99%, suitable for high-sulfur coal flue gas treatment.

Resource utilization: The by-product ammonium sulfate (fertilizer) has economic value and no secondary pollution.

Strong adaptability: Good adaptability to flue gas load and SO₂ concentration fluctuations.

No wastewater discharge: The system operates in a closed loop, and the wastewater can be reused in the process.

Lower energy consumption: Compared with the limestone-gypsum method, the energy consumption is reduced by about 20%~30%.

Applicable scenarios

It is suitable for power plants, steel, chemical industries and other industries, especially for enterprises with nearby ammonia sources (such as fertilizer plants) or need by-product fertilizers.

It is more suitable for flue gas treatment of medium and high sulfur coal (SO₂ concentration > 2000 mg/Nm³).

Summary

Ammonia desulfurization is a green and resource-based desulfurization technology, especially suitable for scenarios where the by-product ammonium sulfate has a consumption channel. Its core advantage is to convert contaminants into valuable products, but it also addresses ammonia escape and equipment corrosion. With the advancement of ammonia recovery technology, the process is becoming more competitive in terms of environmental protection and economy.