Addressing industrial NOx challenges with ozone oxidation

As environmental regulations tighten globally, industries are under growing pressure to reduce nitrogen oxide (NOx) emissions from their production processes. NOx contributes to the formation of ground-level ozone and fine particulate matter—both harmful to human health and the environment. The need for more efficient, compact, and cost-effective treatment methods is more urgent than ever, especially in sectors like semiconductor manufacturing, chemical processing, and other high-tech industries where NOx is generated through high-temperature combustion or chemical reactions.

In South Korea, for example, the government enforces stricter emissions control under the Air Pollutant Total Emission Management System (대기오염물질 총량관리제), which sets annual NOx emission limits for industries in designated zones. This regulation affects sectors like semiconductors and chemical manufacturing, pushing them to adopt cleaner, more space-efficient technologies to meet reduction targets and avoid penalties.

Limitations of traditional NOx control technologies

Traditionally, industries have relied on Selective Catalytic Reduction (SCR) or Selective Non-Catalytic Reduction Systems (SNCR) to reduce NOx emissions. Both SCR and SNCR reduces nitrogen oxides (NOx) into nitrogen and water vapour using a reducing agent (typically ammonia or urea solution), with SCR additionally requiring a catalyst for the process. While effective under specific conditions, SCR and SNCR have several challenges:

• High operating temperature and high energy consumption:  The operating temperature range for SCR (250-427°C) ¹ and SNCR (870-1,150°C) ² is high, often requiring additional heating systems. This requirement also makes it difficult for the systems to be added to existing infrastructure
• Large footprint & high installation cost: SCR is expensive and time consuming to install, and requires a large installation space. The equipment is bulky and challenging to integrate into existing facilities.
• High maintenance: The catalyst used in SCR will have to be replaced or cleaned regularly as deposits will form on it over time.

In general, SCR is used in facilities which require greater NOx control, or for larger setups, while SNCR is a more affordable solution for smaller setups or where moderate NOx reduction is acceptable.

Ozone oxidation: a high efficiency approach to NOx reduction

Ozone oxidation is gaining attention as an effective alternative to SCR and SNCR, or as a complementary step to SNCR (urea solution) for industrial NOx control. Instead of relying on high temperatures and chemical reagents, this method introduces ozone (O₃) into the exhaust stream, where it reacts with nitrogen oxides (NO and NO₂) to form nitrogen pentoxide (N₂O₅), which is soluble and can be safely removed via wet scrubbing or similar processes.

This makes ozone oxidation particularly suitable for low-temperature flue gas or retrofit applications due to its smaller footprint and lower operating temperature compared with SCR and SNCR.

Ozone-based systems offer several practical advantages over SCR and SNCR technologies:

• High efficiency at lower temperatures: Ozone systems are more effective at removing NOx as compared to SCR and SNCR, enabling facilities to reliably meet NOx limits. They are capable of reducing NOx at an efficiency rate of over 95% in an operating temperature range of up to 150°C. This makes them suitable for retrofits and systems where temperature cannot be controlled easily.
• Easy and flexible installation: Compact, modular systems can be mounted on rooftops or in tight spaces—especially valuable for urban plants or retrofit projects with space constraints.
• Easier to maintain: With no catalyst required, systems require less servicing compared to SCR setups and reduces cost and maintenance complexity.
• Scalability: Easily adapted to varying capacity requirements and integrated into existing infrastructure as a retrofit unit. However, ozone systems may not be the best fit for facilities with huge NOx emissions.

By combining regulatory compliance, operational ease, and spatial efficiency, ozone oxidation provides manufacturers with a sustainable approach to NOx reduction.

Proven performance for emission compliance: WEDECO ozone systems

WEDECO ozone systems are reliable, high-performance solutions for consistent NOx reduction in demanding industrial environments. It offers flexible control and efficient ozone generation tailored to your process needs. Key features include:

• EFFIZON®³ electrode technology, designed to enhance ozone generation efficiency and ensure stable high-concentration ozone output, even under fluctuating operating conditions.
• Robust design: Corrosion-resistant construction ensures stable operation, even with high hydrocarbon concentrations in the oxygen feed gas—typical in liquid oxygen systems used in South Korea.
• Flexible control: Ozone output is automatically adjustable within seconds from 5% to 100% based on process needs.
• Fully integrated instrumentation: Built-in sensors and controls support automated and safe operation.
• Compact footprint: Simplified layout enables rooftop installation, freeing up valuable plant floor space.
• Low maintenance: Long-lasting components enable decades of reliable operation, backed by a 10-year guarantee on discharge tubes—reducing total cost of ownership.

Advancing industrial NOx reduction with ozone technology

As governments continue to tighten NOx emission limits, ozone oxidation is emerging as a practical and efficient alternative or an additional step to conventional NOx control systems in meeting stricter emission standards. For industries seeking to reduce their environmental impact, this technology is a viable option to consider.

Backed by Xylem’s decades of experience in advanced oxidation and on-site integration, WEDECO ozone systems provide a proven path to compliance.

<sup>1. EPA AIR POLLUTION CONTROL COST MANUAL, Section 4.2, Chapter 2, 2.2.2 (P2-9)
2. Air Pollution Control Technology Fact Sheet
3. EFFIZON is a registered trademark of Xylem or its affiliates in some countries.</sup>