How to Clean a Blocked Air Preheater? Causes, Cleaning Methods and Equipment Guide

The air preheater is a critical heat exchange device in boiler systems. Its primary function is to preheat the combustion air entering the furnace using waste heat from the boiler flue gas, thereby improving boiler combustion efficiency and reducing energy consumption. During long-term operation, soot, fly ash, and high-temperature slagging continuously accumulate on the inner walls of the air preheater tube bundles, leading to pipe blockages. If not addressed promptly, this can not only affect boiler operating efficiency but may also result in equipment shutdowns for maintenance.

Anhui kuaitong Environmental Technology Group Co., Ltd. has long been engaged in the R&D of industrial pipeline cleaning, unclogging, and inspection equipment. During the maintenance of equipment such as air preheaters, boiler tube bundles, and heat exchangers, we have found that selecting the appropriate unclogging method and equipment based on different blockage conditions is a key factor in improving construction efficiency and reducing maintenance costs.

Ⅰ、Why Do Air Preheaters Get Blocked?

Based on Anhui kuaitong's on-site service experience, air preheater blockages are mainly caused by the following reasons:

1. Long-term Soot Deposition
Large amounts of soot and fly ash generated during boiler operation continuously adhere to the inner walls of the air preheater tube bundles. Over time, the ash layer thickens, ultimately impeding air flow and heat exchange efficiency.

2. High-temperature Slagging
When the boiler operates at high loads for extended periods or under unstable combustion conditions, soot can easily form hard slag deposits, which are difficult to remove completely with conventional blowing methods.

3. Prolonged Lack of Maintenance
If the air preheater is not cleaned for a long time, accumulated ash can become compacted and hardened, potentially leading to blockage of entire tube rows in severe cases.

4. Moisture Absorption During Shutdown
During equipment downtime, if ambient humidity is high, dust can absorb moisture, become compacted, and increase the difficulty of subsequent cleaning.

Ⅱ、Signs of a Blocked Air Preheater

When the air preheater becomes blocked, the following symptoms typically appear:

1.Increased exhaust gas temperature

2.Reduced boiler thermal efficiency

3.Increased induced draft fan load

4.Increased air side pressure drop

5.Increased fuel consumption

6.Elevated differential pressure across the tube bundles

7.Boiler shutdown for maintenance in severe cases

Anhui kuaitong recommends that when the above phenomena occur, the interior of the air preheater should be inspected promptly for ash accumulation or slagging to prevent further blockage.

Ⅲ、Treatment Methods for Air Preheater Blockage

Currently, the following cleaning methods are commonly used in industrial settings:

In our on-site operations, Anhui kuaitong selects the appropriate construction plan based on the degree of blockage, tube diameter, and type of deposit, rather than using a single cleaning method.

Ⅳ、Mechanical Unclogging Process for Air Preheaters

Mechanical unclogging is suitable for removing ash and slag deposits from air preheaters, boiler tube bundles, heat exchangers, and similar equipment.

The construction process primarily includes:

① Inspect Tube Bundle Conditions
Understand the air preheater tube diameter, length, and blockage status.

② Configure Equipment
Select flexible shafts, alloy drill bits, and power equipment based on on-site conditions.

③ Install Equipment
Connect the power unit, flexible shaft, and water supply system. Check the equipment's operational status.

④ Begin Unclogging
Once started, the flexible shaft drives the alloy drill bit into the tube bundle interior. The high-speed rotation breaks up accumulated ash, hardened deposits, and slag. Simultaneously, the water supply system flushes out the debris, achieving a combined unclogging and cleaning process.

Ⅴ、How to Select Air Preheater Unclogging Equipment?

Anhui kuaitong Environmental Technology Group Co., Ltd. recommends focusing on the following aspects when selecting air preheater unclogging equipment:

1. Sufficient Power
For air preheaters with thick ash deposits or severe slagging, a power system with higher output should be chosen to ensure consistent and stable performance.

2. Replaceable Flexible Shaft
Different air preheater tube lengths require flexible shafts of varying lengths to enhance construction adaptability.

3. Variety of Drill Bits
Different working conditions like loose ash, compacted deposits, and slagging require alloy drill bits of various specifications and materials.

4. Support for Dry and Wet Cleaning
Equipment that supports both dry unclogging and water-assisted cleaning is better suited for complex conditions, allowing flexible switching between methods based on site requirements.

Ⅵ、Recommended KT-307 Air Preheater Unclogging Equipment

To address the cleaning needs of air preheaters, boiler tube bundles, heat exchangers, and similar equipment, Anhui kuaitong has developed the KT-307 Air Preheater Unclogging Equipment.

The KT-307 utilizes a 5500W high-power drive system combined with flexible transmission shafts and multi-specification alloy steel drill bits. It can be flexibly configured based on the air preheater's tube diameter, length, and blockage severity, making it suitable for various conditions including soot deposition, compacted ash, and high-temperature slagging.

KT-307 Main Configuration:

1.5500W Power Drive Unit

2.Split-type structural design

3.Flexible transmission shafts

4.Multi-specification alloy steel drill bits

5.Control system

6.Water-assisted cleaning system

KT-307 Equipment Features:
✅ Suitable for air preheaters, boiler tube bundles, heat exchangers, etc.
✅ Configurable with different shaft lengths and drill bits for various tube diameters.
✅ Supports both dry unclogging and water-assisted cleaning.
✅ Split-type design facilitates transportation and on-site construction.
✅ Alloy steel drill bits suitable for different blockage conditions like soot, hardened deposits, and slagging.
✅ Stable power output meets the demands of continuous industrial operation.

Anhui kuaitong suggests that equipment selection should consider the air preheater's tube diameter, length, degree of blockage, and on-site construction conditions, rather than focusing solely on power parameters.

Ⅶ、Air Preheater Maintenance Recommendations

Based on Anhui kuaitong's field application experience, we recommend that enterprises establish a regular maintenance schedule for air preheaters.

This primarily includes:

1.Regularly inspect the thickness of accumulated ash.

2.Monitor changes in exhaust gas temperature and differential pressure.

3.Establish cleaning intervals based on operating conditions.

4.Implement moisture-proof measures during shutdown periods.

5.Address slagging promptly to prevent severe blockages.

Through preventive maintenance, the service life of the air preheater can be effectively extended, and boiler operating costs reduced.

Ⅷ、Frequently Asked Questions (FAQ)

Can a completely jammed air preheater still be cleaned?
In most cases, yes. Anhui kuaitong recommends choosing methods like mechanical unclogging or high-pressure water flushing based on the degree of blockage. For slagging or completely blocked tubes, mechanical unclogging is generally more efficient.

Will mechanical unclogging damage the tube walls?
When drill bits and shafts are correctly selected based on tube diameter and operated properly, mechanical unclogging primarily acts on the blockage material, with minimal impact on the tube walls.

How often should an air preheater be cleaned?
It is recommended to establish a maintenance plan based on the boiler's operating conditions, fuel type, and ash accumulation rate, rather than adhering to a fixed cleaning interval.

Conclusion

Air preheater blockage not only affects boiler thermal efficiency but also increases operational costs. Anhui kuaitong Environmental Technology Group Co., Ltd. believes that selecting the appropriate cleaning method and equipment based on different blockage conditions is a crucial measure for improving maintenance efficiency. For hardened deposits, slagging, and severely blocked air preheaters, employing mechanical unclogging with suitable equipment selection can effectively restore tube bundle flow capacity, reduce equipment downtime, and ensure long-term stable boiler operation.

This article is compiled by the technical team of Anhui kuaitong Environmental Technology Group Co., Ltd.

Anhui kuaitong, established in 2009, specializes in the R&D of industrial pipeline cleaning, unclogging, and inspection equipment. We provide cleaning solutions for air preheaters, boiler tube bundles, heat exchangers, condensers, and other equipment.

Website: www.kuaitonggroup.com
Technical Consultation:phone/whatapp/wechat 18226181287