Ammonia-Based Desulfurization Is Gaining Ground in the Petrochemical Industry

1. Desulfurization Challenges in Petrochemical Plants

Petrochemical complexes operate under some of the most demanding flue gas conditions in the industrial sector. Unlike conventional power plants, petrochemical facilities consist of multiple emission sources, including heaters, furnaces, boilers, sulfur recovery units (SRU), hydrogen production units, and various off-gas systems. Each unit generates flue gas with different temperatures, sulfur concentrations, moisture levels, and impurity profiles.

Typical challenges faced by petrochemical operators include:

• Fluctuating SO₂ concentrations due to variable feedstock quality

• High moisture and corrosive components in flue gas

• Limited space for retrofit projects

• Strict emission limits driven by environmental regulations and ESG commitments

• High expectations for long-term operational stability

Traditional desulfurization technologies, such as limestone-gypsum wet FGD or sodium-based systems, can technically meet emission standards but often struggle with high operating costs, scaling issues, and waste byproduct management when applied in complex petrochemical environments.

As a result, petrochemical companies are increasingly evaluating ammonia-based flue gas desulfurization (Ammonia FGD) as a more adaptable and economically sustainable solution.

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2. Why Petrochemical Flue Gas Requires a Different Desulfurization Approach

Petrochemical flue gas differs fundamentally from coal-fired power plant flue gas in several aspects:

1. Lower but highly variable sulfur content

2. Higher process integration requirements

3. Greater sensitivity to pressure drop and system downtime

Many petrochemical units operate continuously, and even short shutdowns can lead to significant production losses. Therefore, any desulfurization system must offer:

• Fast response to load changes

• Stable performance under fluctuating operating conditions

• Minimal interference with existing process units

Ammonia-based desulfurization meets these requirements through liquid-phase reactions with high mass transfer efficiency, enabling rapid sulfur absorption even under variable gas conditions.

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3. How Ammonia-Based Desulfurization Works in Petrochemical Applications

In an ammonia-based desulfurization system, SO₂ in flue gas reacts with ammonia solution to form ammonium sulfite and ammonium sulfate. With proper oxidation control, the final product is high-purity ammonium sulfate, a widely used nitrogen fertilizer.

Key reaction advantages include:

• Fast chemical reaction rate

• High sulfur removal efficiency even at low SO₂ concentrations

• Stable performance across wide temperature ranges

For petrochemical plants, ammonia is often readily available as part of existing processes or logistics systems, making integration relatively straightforward.

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4. Key Advantages of Ammonia FGD for Petrochemical Plants

4.1 High Desulfurization Efficiency with Ultra-Low Emissions

Modern ammonia-based systems can achieve SO₂ removal efficiencies above 98%, enabling outlet concentrations well below international emission limits. This makes ammonia FGD suitable not only for compliance today but also for future tightening of environmental regulations.

4.2 No Solid Waste Disposal Burden

Unlike limestone-based systems that generate large volumes of gypsum requiring disposal or off-site sales, ammonia FGD produces marketable ammonium sulfate. This transforms desulfurization from a cost center into a resource recovery process.

For petrochemical operators focused on circular economy principles, this advantage is particularly attractive.

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4.3 Lower Operating Costs Over the Project Lifecycle

Although ammonia-based systems may require careful design and control, their overall lifecycle cost is often lower than conventional alternatives due to:

• Reduced reagent consumption

• Minimal scaling and fouling

• Lower maintenance frequency

• Revenue from byproduct sales

In large petrochemical complexes, these savings become increasingly significant over long-term operation.

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4.4 Strong Adaptability to Complex Flue Gas Conditions

Petrochemical flue gas may contain:

• Trace hydrocarbons

• Acidic components

• Fine particulates

Advanced ammonia-based systems incorporate multi-stage gas-liquid separation and purification, ensuring stable operation without secondary pollution such as aerosol formation or visible plume issues.

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5. Addressing Traditional Concerns About Ammonia Desulfurization

Historically, some petrochemical companies hesitated to adopt ammonia-based desulfurization due to concerns about:

• Ammonia slip

• Aerosol formation

• Corrosion risks

However, modern engineering solutions have largely resolved these issues.

Advanced systems use:

• Precise ammonia injection control

• Multi-stage mist eliminators

• Optimized oxidation and pH management

As a result, ammonia slip can be controlled at below 1 mg/Nm³, while aerosol formation is effectively suppressed.

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6. Integration with Existing Petrochemical Infrastructure

One of the strongest advantages of ammonia FGD is its compatibility with existing petrochemical systems.

It can be integrated with:

• Waste heat recovery units

• Tail gas treatment systems

• Centralized flue gas treatment facilities

The relatively low pressure drop of ammonia-based absorbers ensures minimal impact on upstream process units, a critical factor in continuous petrochemical production.

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7. Environmental and ESG Benefits

From an ESG perspective, ammonia-based desulfurization supports multiple sustainability objectives:

• Significant reduction of sulfur emissions

• Conversion of pollutants into valuable products

• Reduced solid waste generation

• Improved overall resource efficiency

These benefits help petrochemical companies strengthen their environmental credentials while maintaining operational competitiveness.

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8. A Long-Term Solution for the Petrochemical Industry

As petrochemical plants face increasing pressure to reduce emissions without sacrificing productivity, ammonia-based desulfurization offers a balanced solution combining environmental performance, economic viability, and operational reliability.

With continuous technological improvements, ammonia FGD is no longer an experimental option—it is a mature and proven technology suitable for large-scale petrochemical applications worldwide.