Paper Mill Boiler Soot Blowing Retrofit: 40 Semi-Retractable Soot Blowers for Severe Ash Fouling

A reliable soot blowing system for a paper mill boiler must be designed around more than the soot blower itself.

Fuel characteristics, combustion conditions, flue-gas temperature, heating-surface arrangement, blowing-medium quality, equipment configuration and control strategy all influence the actual cleaning performance.

In this retrofit project, SHEENWAY provided a comprehensive EPC solution for the steam soot blowing systems of two industrial boilers at a large paper manufacturing base in eastern China.

The boilers operated with papermaking sludge together with coal. Following modifications to the combustion system for low-NOx operation, significant ash accumulation had become an important operational concern.

Rather than simply replacing the existing soot blowers, the project was approached as a complete soot blowing system modernization covering equipment selection, temperature-specific material design, steam pressure reduction and drainage, piping, DCS control, installation, commissioning and performance verification.

Project Overview

The project involved the retrofit of two industrial boilers.

Each boiler was equipped with 20 SW-SHRS Semi-Retractable Soot Blowers, giving a total of:

40 SW-SHRS Semi-Retractable Soot Blowers

The soot blowers were distributed across several heating-surface zones on each boiler:

• 8 units for superheater sections
• 6 units for the economizer
• 6 units for the air preheater

The retrofit utilized the existing soot blower installation positions wherever practical, reducing unnecessary structural modifications while maintaining the required cleaning coverage.

The overall EPC scope included:

• Soot blower engineering and design
• Equipment manufacturing and supply
• Soot blowing steam piping
• Pressure-reducing system
• Steam drainage system
• Valves and instrumentation
• DCS integration
• Power and control cabinets
• Electrical and instrumentation work
• Civil and structural modifications
• Installation
• Cold and hot commissioning
• Trial operation
• Performance verification
• Operator training
• Spare parts and technical documentation

The objective was not simply to replace aging equipment, but to establish a more reliable and maintainable soot blowing system suitable for the boilers' actual fuel and operating conditions.

The Operating Challenge: Papermaking Sludge and Heavy Ash Deposition

One of the defining characteristics of this project was the boiler fuel.

The boilers operated with papermaking sludge and coal, and the project fuel analysis showed that the sludge contained particularly high levels of moisture and ash.

The specified papermaking sludge had approximately:

• 49.8% as-received moisture
• 57.74% as-received ash

For comparison, the specified coal had approximately:

• 11.8% as-received moisture
• 20.46% as-received ash

This fuel combination presents a distinctly different soot blowing challenge from a conventional coal-fired boiler.

Large quantities of inorganic material entering the furnace can contribute to ash loading on downstream heating surfaces, while the high moisture content of sludge also influences combustion and flue-gas conditions.

The project technical requirements identified serious ash accumulation associated with papermaking sludge combustion and the operating conditions following the low-NOx retrofit.

This made effective and repeatable online cleaning particularly important.

A Wide Range of Flue-Gas Temperatures

Another important engineering challenge was the significant temperature difference between the various soot blower installation zones.

The specified flue-gas temperatures were approximately:

• 840°C at the highest-temperature superheater section
• 760°C at the second superheater section
• 500°C at the economizer
• 220°C at the air preheater

Using exactly the same lance material throughout these zones would not provide an optimized engineering solution.

The project therefore required material selection according to the actual thermal environment at each installation position.

This temperature-based material strategy became one of the key design features of the retrofit.

Why SW-SHRS Semi-Retractable Soot Blowers Were Selected

The project utilized SW-SHRS Semi-Retractable Soot Blowers.

The SW-SHRS design combines retractable movement with a lance arrangement in which part of the soot blowing barrel remains inside the boiler.

Multiple nozzle groups positioned along the lance can clean different areas during the travel cycle, allowing the effective cleaning area to extend beyond the physical stroke of the mechanism. This type of semi-retractable arrangement is particularly suitable for economizers, tubular air preheaters, convection tube banks and other lower-temperature heating-surface zones where installation space is limited.

This configuration offers practical advantages in retrofit applications where:

• Existing boiler openings need to be retained
• Maintenance platform space is limited
• Multiple heating-surface zones require directed cleaning
• Broad cleaning coverage is required within a relatively compact installation footprint

For this project, the soot blowers were configured around the existing boiler arrangement while maintaining the required 360° blowing coverage.

Each project-specific unit incorporated five nozzles, with an effective cleaning radius of approximately 1.5–2.0 meters.

Temperature-Specific Lance Material Design

The soot blower configuration was not identical across all 20 installation positions on each boiler.

Because the highest-temperature superheater section operated at approximately 840°C, the four soot blowers in this zone used 2520 high-temperature-resistant lance material.

For the remaining 16 soot blowers on each boiler, the lance material was specified as 06Cr18Ni11Ti, corresponding to their respective temperature conditions.

Across the two boilers, this resulted in:

• 8 high-temperature lance configurations for the hottest superheater zones
• 32 stainless-steel lance configurations for the remaining heating-surface zones

The inner pipes were specified in 304 stainless steel, while the valves used WCB material.

This differentiated material selection illustrates an important principle of soot blower engineering:

The equipment model alone does not determine the final configuration.

Flue-gas temperature, fuel characteristics, ash properties, installation position, cleaning radius, blowing-medium conditions and long-term thermal exposure must all be considered when determining the final lance and nozzle design.

Steam Pressure Reduction and Blowing-Medium Management

Effective soot blowing depends heavily on the quality and stability of the blowing medium.

The available steam source for the project was specified at approximately:

• 10.28 MPa
• 450°C

The soot blowing system therefore required pressure reduction before steam entered the soot blower network.

After pressure reduction, the specified steam conditions were approximately:

• 2.8 MPa
• 353°C

The EPC design included a complete soot blowing steam piping system rather than simply connecting the new soot blowers to the existing steam source.

The system incorporated components such as:

• Isolation valves
• Pressure-reducing equipment
• Safety valves
• Drain valves
• Pressure instruments
• Temperature measurement
• Expansion compensation
• Pipe supports
• Flow-control devices
• Associated piping and fittings

Each soot blower was provided with a flow-regulation arrangement so that the blowing conditions could be matched to the requirements of its particular heating-surface zone.

The piping design also considered thermal expansion, condensate drainage, pressure loss, accessibility and maintenance.

This system-level approach helps ensure that the steam reaching each soot blower has the conditions required to produce a stable and consistent cleaning jet.

Drainage and System Safety

Condensate management is particularly important in steam soot blowing systems.

If water remains in the steam piping before a blowing cycle, unstable steam conditions can reduce cleaning consistency and impose unnecessary mechanical and thermal stress on the equipment.

For this reason, the retrofit incorporated a dedicated drainage arrangement together with the pressure-reducing and steam-distribution system.

Drainage, safety protection, pressure control and instrumentation were therefore treated as integral parts of the soot blowing system rather than secondary accessories.

Boiler Interface and Retrofit Compatibility

Because the project was performed on existing boilers, dimensional compatibility was a major part of the engineering work.

The new soot blowers had to match:

• Existing soot blower openings
• Boiler wall interfaces
• Existing operating platforms
• Surrounding heating-surface geometry
• Available maintenance space

The interface between the soot blower and boiler wall also required reliable sealing to prevent flue-gas leakage.

The equipment layout was therefore engineered around the actual boiler structure rather than simply applying a standard catalogue configuration.

This is particularly important in retrofit projects, where even relatively small differences in mounting dimensions, lance length, interface position or maintenance clearance can significantly affect installation and future operation.

DCS-Integrated Control System

The project also included a complete soot blowing control system integrated with the plant DCS.

Each soot blower could be controlled locally, while the overall system was designed for centralized monitoring and operation.

Control functions included:

• Forward movement
• Reverse movement
• Travel limit monitoring
• Equipment status feedback
• Start and stop commands
• Local manual control
• Centralized DCS operation
• Alarm and signal feedback

The system design included dedicated control cabinets, operator stations, an engineering station and the required I/O interfaces.

This allowed the soot blowing system to become part of the plant's wider operating and monitoring architecture rather than functioning as an isolated mechanical system.

Regional Operating Environment

The project was located at a large industrial manufacturing base in eastern China.

The region is characterized by warm and humid conditions, pronounced seasonal rainfall and significant changes in temperature and humidity throughout the year.

For equipment installed outside the boiler casing, these conditions increase the importance of appropriate enclosure protection, sealing, electrical installation quality, corrosion resistance and long-term maintainability.

The soot blowing system was therefore considered not only in terms of the high-temperature environment inside the boiler, but also in terms of the industrial conditions surrounding the drive mechanisms, electrical components, instruments and control equipment.

EPC Delivery and Boiler-by-Boiler Commissioning

The project covered substantially more than equipment manufacturing.

SHEENWAY's EPC responsibilities included:

• Engineering
• Manufacturing
• Supply
• Transportation
• Civil and structural work
• Installation
• Electrical and instrumentation work
• Control-system integration
• Commissioning
• Trial operation
• Performance assessment
• Operator training
• Technical documentation

The two boilers were handled in stages.

The first boiler was supplied, installed, commissioned and placed into operating condition before the second boiler retrofit proceeded according to the agreed project sequence.

This staged approach reduced project risk and allowed operating experience from the first system to be incorporated into the execution of the second.

SHEENWAY engineers also provided on-site technical guidance during installation and hot commissioning.

Quality Assurance and Long-Term Reliability

The project established clear requirements for the mechanical and operational reliability of the soot blowing equipment.

The soot blowers were required to:

• Achieve the specified cleaning performance
• Extend and retract reliably
• Avoid sticking during hot operation
• Maintain reliable boiler-wall sealing
• Operate with stable steam conditions
• Provide reliable position feedback
• Integrate correctly with the control system
• Allow convenient inspection and maintenance

A 12-month product quality warranty period was specified after the units entered formal operation.

For failures attributable to design or manufacturing quality during the warranty period, corresponding technical support and corrective action were included within the project requirements.

Why This Project Matters

This project involved one primary soot blower type, but the engineering challenge was far from simple.

Forty semi-retractable soot blowers had to operate across heating-surface zones ranging from approximately 220°C to 840°C, while cleaning ash generated by boilers firing a combination of coal and high-moisture, high-ash papermaking sludge.

At the same time, the retrofit had to preserve existing boiler interfaces, work within existing platform limitations, integrate with the steam and DCS systems, and provide materials suited to different temperature zones.

The project therefore demonstrates several core capabilities of SHEENWAY:

• Soot blower retrofit engineering
• Paper-industry boiler experience
• Mixed-fuel and high-ash operating-condition analysis
• Temperature-specific material selection
• Steam piping and pressure-reduction engineering
• DCS control integration
• Existing-equipment replacement and dimensional matching
• EPC installation and commissioning support

A successful retrofit does not begin by asking only:

“Which soot blower model fits this opening?”

The more important questions are:

What fuel is the boiler burning? Where is ash accumulating? What is the flue-gas temperature at each cleaning position? What steam conditions are available? What material should the lance use? How should the new equipment integrate with the existing boiler and control system?

Answering these questions is what turns equipment replacement into an engineered soot blowing solution.

SHEENWAY Soot Blower Solutions for the Paper Industry

SHEENWAY provides soot blowing equipment, replacement systems, spare parts and engineering services for industrial boilers used in pulp and paper production and other demanding process industries.

Our engineering capabilities include:

• Semi-retractable soot blowers
• Long retractable soot blowers
• Furnace soot blowers
• Fixed rotary soot blowers
• Air preheater soot blowers
• Steam piping and pressure-reducing systems
• Soot blowing control systems
• Replacement spare parts
• Retrofit dimensional engineering
• Installation and commissioning support

For existing boiler retrofit projects, SHEENWAY can evaluate the original equipment, boiler geometry, fuel and ash characteristics, flue-gas temperature, available blowing medium, control architecture and site constraints to develop a solution suited to actual operating conditions.

Planning a soot blower retrofit for a paper mill or industrial boiler? Contact SHEENWAY to discuss your boiler configuration, fuel conditions and existing soot blowing system.