Resource Center
Mechanisms, Hazards, and Prevention Strategies for Alkali Metal Poisoning in SCR DeNOx Catalysts
Release time:
Apr 24,2026
Selective Catalytic Reduction (SCR) is the mainstream technology for controlling nitrogen oxides in coal-fired power plants, biomass boilers, and industrial furnaces. Alkali metal (Na, K) poisoning is one of the key factors leading to irreversible catalyst deactivation and a significant reduction in catalyst lifespan.
Water-soluble sodium and potassium salts in flue gas can penetrate deep into the catalyst’s pores, destroying acidic active sites through a dual mechanism of chemical poisoning and physical blockage. This significantly reduces DeNOx efficiency and increases operational and maintenance costs as well as environmental emission risks. This paper systematically discusses the sources of alkali metals, their mechanisms of action, their impact on performance, and end-to-end prevention and control technologies, providing a technical reference for the stable operation of catalysts under high-alkali-metal conditions.
I. Sources, Migration, and Transformation of Alkali Metals
Coal and biomass fuels commonly contain alkali metal elements such as sodium (Na), potassium (K), and arsenic (As), which, after combustion, enter the SCR system with flue gas in the form of gaseous oxides, chlorides, sulfates, and other compounds.
● In coal, alkali metals are primarily found in minerals such as feldspar and mica, and are released as water-soluble components at high temperatures;
● Flue gas from biomass fuels and waste incineration contains higher levels of water-soluble K⁺ and Na⁺, resulting in a significantly higher risk of catalyst poisoning compared to pure coal combustion;
● Alkali metal salts have small particle sizes and are highly mobile; they can enter the catalyst bed with the flue gas and, upon condensation with water vapor, accelerate their penetration into the internal pores.
II. Mechanisms of Alkali Metal Poisoning in DeNOx Catalysts
1. Chemical Poisoning (Irreversible Deactivation of the Core)
Alkali metals (represented by K₂O and Na₂O) are strongly basic and preferentially undergo neutralization reactions with Brønsted acid sites (V–OH) on the catalyst surface, forming inactive salts such as V–OK and V–ONa.
● Directly occupy acidic sites, blocking NH₃ adsorption and activation, and inhibiting the formation of the active NH₄⁺ intermediate;
● Disrupt the electronic structure of V₂O₅–WO₃(MoO₃)/TiO₂, reducing redox capacity and catalytic cycle efficiency;
● Studies indicate that when the K₂O loading exceeds 1%, the catalyst can be completely deactivated, and full recovery through conventional regeneration is difficult.
2. Physical Blockage and Coating
Alkali metal salts deposit and agglomerate at pore entrances and within pores, forming a dense coating layer:
● Reducing specific surface area, pore volume, and porosity, thereby hindering NO and NH₃ diffusion and mass transfer;
● Agglomerating with fly ash and ammonium sulfate salts, increasing reactor resistance, and exacerbating localized ash blockage and gas flow deviation.
3. Structural Degradation
Alkali metal intrusion weakens the crystalline stability of the TiO₂ support, leading to the following issues during long-term operation:
● Agglomeration of support particles and sintering of micropores;
● Decreased mechanical strength, increasing the risk of wear, collapse, and fracture, and shortening the replacement cycle.
III. The Adverse Effects of Alkali Metal Poisoning on Catalyst Performance
● Rapid decline in DeNOx efficiency: Even the continuous accumulation of trace amounts of alkali metals can lead to a decline in activity; under high-alkali conditions, efficiency drops significantly within a few months;
● Drastically shortened active life: Lifespan is reduced by 30%–60% compared to normal operating conditions, with biomass boilers being particularly affected;
● Significant increase in ammonia slip: Excessive ammonia injection to maintain efficiency leads to air preheater blockages, corrosion, and increased fan energy consumption;
● Soaring operating costs: Shorter replacement cycles and increased regeneration difficulty result in a substantial rise in O&M expenses;
● Increased risk of emission non-compliance: Difficulty in consistently meeting ultra-low NOₓ emission requirements creates a risk of environmental penalties.
IV. Methods for Diagnosing and Characterizing Alkali Metal Poisoning
1. Elemental Analysis
Determine Na and K content via XRF and ICP–MS; a K₂O + Na₂O content exceeding 1% is considered indicative of significant poisoning.
2. Structural Analysis
● BET: Significant deterioration in specific surface area, pore volume, and pore size distribution;
● XRD: Detection of inert phases such as potassium/sodium vanadate salts; changes in the carrier crystal phase.
3. Activity Evaluation
NH₃–TPD and H₂–TPR analyses show a simultaneous decrease in surface acidity and reducing capacity, with restricted reaction kinetics.
4. On-Site Operational Characterization
Decreased DeNOx efficiency, increased ammonia slip, abnormal rise in reactor pressure differential, and sustained increase in ammonia injection rate.
V. Alkali Metal Poisoning Prevention, Control, and Treatment Technologies
1. Source Control of Alkali Metals (Most Economical and Effective)
● Fuel Management: Select coal types with low alkali metal content and blend biomass with coal in appropriate proportions to reduce the alkali content entering the furnace;
2. Upstream Flue Gas Dealkalization
Install an alkali metal treatment unit upstream of the SCR system and use a high-temperature dust removal device to remove alkali metal salts, thereby achieving upstream removal and protecting the downstream catalyst.
3. Alkali-Resistant Catalyst Design
● Structural Optimization: Select carriers with large pore diameters, high porosity, and thick walls to enhance resistance to clogging and permeation;
● Formulation Modification: Increase the proportion of WO₃ and MoO₃ additives to prioritize binding with alkali metals and protect V–OH active sites;
● Surface Modification: Introduce acidic coatings to inhibit the adsorption, migration, and diffusion of alkali metals.
4. Operational Optimization and Regeneration
● Strict Temperature Control: Maintain the optimal reaction range of 300–380°C to prevent low-temperature water vapor condensation and the dissolution and migration of alkali metal salts;
● Enhanced Soot Blowing: Reasonably increase the frequency and pressure of soot blowing to reduce deposits at orifices and prevent caking;
● Tiered Replacement: Since the upper layer of catalyst is prone to poisoning first, conduct periodic sampling and replacement to reduce overall operational and maintenance costs;
● Regeneration Strategy: For mild poisoning, acid washing can remove alkali and restore activity; for severe poisoning, where chemical bonds are strong, regeneration effectiveness is limited, so direct replacement is recommended.
VI. Conclusion
Alkali metal poisoning is an irreversible deactivation caused primarily by chemical poisoning and secondarily by physical blockage; it is the primary failure mode of SCR systems under coal/biomass co-firing and high-alkali fuel operating conditions.
Prevention and control must adhere to a comprehensive four-pronged approach: source-level alkali control, upstream alkali removal, alkali-resistant catalyst selection, and optimized operation. By precisely monitoring alkali metal content and employing alkali-resistant catalysts and upstream alkali removal technologies, it is possible to effectively slow the poisoning process, extend catalyst lifespan, and ensure long-term, stable compliance with emission standards for the DeNOx system.
See You at IFAT 2026 in Munich
2026-04-24
Learn about clean flue gas solutions?
With over 15 years of industry experience, we provide customized solutions. Please feel free to contact us for a free consultation.
Want to Become Our Distributor?
Flexible Partnerships: We offer three collaboration models—supply, OEM, and system integration.
Interested in custom services?
Submit your requirements, and we’ll create a customized solution for your project
Page Links
Contact
Add:
Xianchuang Zone, Huantai County, Zibo City, Shandong Province, China
Message
Fill out the form below and we will be in touch as soon as possible.
Copyright © 2026 Shandong AIREP Environmental Technology Co., Ltd. | SEO | AI Search
国际站建设：中企动力 淄博 外贸Google推广
Hi
Contact us for more preferential prices !
Privacy Policy & Terms
Last Updated: March 27, 2026
Part 1: Privacy Policy
1. Introduction
AIR Environmental Protection (hereinafter referred to as "we," "our company," or "AIR Environmental Protection") respects and protects your privacy. This Privacy Policy explains how we collect, use, store, protect, and share your personal information when you visit our website (hereinafter referred to as "this website") or use our services.
Please carefully read and fully understand this Privacy Policy before using this website or providing us with your personal information. If you do not agree with this policy, please do not use this website or provide your personal information.
2. Information We Collect
2.1 Information You Voluntarily Provide
When you interact with this website, we may collect the following information you voluntarily provide:
Contact Information: Name, company name, email address, phone number, country/region
Inquiry Information: Product requirements, project details, message content provided during product inquiries or when contacting us
Account Information: If you register an account, we collect your username, password, and other registration details
Subscription Information: If you subscribe to our newsletter or marketing communications
Technical Inquiries: Technical questions you raise via email, online customer service, or social media
2.2 Information Automatically Collected
When you visit this website, we may automatically collect the following information:
Device Information: IP address, browser type, operating system, device type, screen resolution
Access Information: Access time, pages viewed, click behavior, referral source, time spent on site, download history
Location Information: Approximate geographic location based on IP address (country/city level)
Performance Information: Page load speed, error reports, and other website performance data
2.3 Cookies and Similar Technologies
We use cookies and similar technologies to enhance your browsing experience. For details, please refer to the Cookie section of this policy.
3. How We Use Your Information
We may use the information collected for the following purposes:
Provide and Optimize Services: Respond to your inquiries, process orders, provide technical support, arrange sample delivery
Communication and Feedback: Reply to your queries, send order confirmations, shipping notifications, delivery tracking information, etc.
Personalized Experience: Recommend relevant products and services based on your interests and preferences
Marketing and Promotion: Send product updates, industry news, promotional activities (you may unsubscribe at any time)
Website Analytics: Analyze website visit data to optimize website content and user experience
Legal Compliance: Comply with applicable laws and regulations, respond to legitimate requests from law enforcement agencies
Security Assurance: Detect and prevent fraud, abuse, and other malicious activities
4. Information Sharing and Disclosure
We are committed to not selling your personal information. We may share your information with third parties in the following circumstances:
4.1 Service Providers
We may partner with trusted third-party service providers to assist in operating our website, processing payments, sending emails, providing technical support, analyzing data, etc. These service providers may access your information only to the extent necessary to perform their functions and are obligated to maintain confidentiality.
Website Hosting: Cloud service providers
Data Analytics: Google Analytics, Baidu Analytics, etc.
Email Services: Email marketing platforms
Online Customer Service: Customer service system providers
4.2 Business Transfer
In the event of a merger, acquisition, asset sale, bankruptcy liquidation, or similar transaction, your information may be transferred as a business asset. We will notify you of such changes via notice or announcement.
4.3 Legal Requirements
We may disclose your information under the following circumstances:
To comply with applicable laws and regulations
To respond to court orders, subpoenas, or other legal processes
To protect the rights, property, or safety of us and our affiliates
To investigate or address fraud or security incidents
5. Data Security
We implement reasonable technical and organizational measures to protect your personal information from unauthorized access, use, disclosure, modification, or destruction:
SSL Encryption: This website uses SSL/TLS encryption technology to ensure secure data transmission
Access Control: Internal access rights are strictly restricted; only authorized personnel may access personal information
Periodic Review: Data collection, storage, and processing practices are reviewed periodically
Security Training: Employees undergo data security and privacy protection training
Please note: While we take reasonable measures to protect your information, no data transmission or storage system can be 100% secure. If you discover any security vulnerability, please contact us immediately using the information provided.
6. Data Retention
We will retain your personal information for the period necessary to fulfill the purposes described in this policy, unless a longer retention period is required or permitted by law.
Inquiry Information: 5 years after transaction completion
Account Information: Duration of account existence plus 3 years after account closure
Subscription Information: Until you unsubscribe
Website Access Logs: 12 months
7. Your Rights
Under applicable data protection laws (such as the GDPR), you have the following rights concerning your personal information:
Right of Access: Request a copy of your personal information from us
Right to Rectification: Request correction of inaccurate or incomplete personal information
Right to Erasure: Request deletion of your personal information under specific circumstances
Right to Restriction of Processing: Request restriction of processing your personal information under specific circumstances
Right to Data Portability: Request transfer of your personal information to a third party in a structured format
Right to Object: Object to processing of your personal information based on legitimate interests
Right to Withdraw Consent: Withdraw previously granted consent at any time (without affecting the lawfulness of processing based on consent before withdrawal)
If you wish to exercise any of these rights, please contact us using the information provided at the end of this policy. We will respond to your request within 30 days.
8. Cookie Policy
8.1 What are Cookies?
Cookies are small text files stored on your device by a website to record your preferences, login status, and browsing behavior.
8.2 Types of Cookies We Use
Necessary Cookies: Enable basic website functions (e.g., page navigation, language selection) – Required: Yes
Performance Cookies: Collect website usage information to help improve website performance – Required: No
Functional Cookies: Remember your preferences to provide a personalized experience – Required: No
Marketing Cookies: Used to deliver relevant advertisements and analyze marketing effectiveness – Required: No
8.3 Managing Cookies
You can manage or delete cookies through your browser settings. Please note that disabling necessary cookies may affect the normal functionality of the website.
9. Third-Party Links
This website may contain links to third-party websites. These sites have independent privacy policies, and we assume no responsibility for the content or practices of such sites. Please carefully read their privacy policies before submitting information to third-party websites.
10. International Data Transfers
AIR Environmental Protection is located in China, and our services may be offered to customers globally. If you are located outside China, your information may be transferred to China or other countries/regions. We will take appropriate security measures to ensure your information is adequately protected.
11. Children's Privacy
This website is not intended for minors under 18 years of age. We do not knowingly collect personal information from minors. If we discover that such information has been inadvertently collected, we will delete it immediately.
12. Updates to This Privacy Policy
We may update this Privacy Policy from time to time. Material changes will be communicated to you through one of the following methods:
Posting the updated version on this website
Notifying you via email (if you are subscribed) or a website announcement before the change takes effect
We recommend that you periodically review this Privacy Policy to stay informed of the latest updates.