Fan Retrofit Project at a Power Plant: Eight centrifugal fans for the boiler forced draft and flue gas systems

Project Overview

SIMO Blower supplied eight industrial centrifugal fans for a biomass power generation project that involved boiler system modifications and specific fan configuration requirements.

The project encompassed four fan application scenarios: primary air, secondary air, induced draft, and flue gas recirculation. Each application had distinct requirements regarding airflow and pressure parameters; furthermore, the induced draft and flue gas recirculation fans were designed to operate at higher temperatures than the combustion air supply fans.

Rather than employing a uniform fan configuration across the entire boiler system, SIMO supplied four different types of fans tailored to the project's technical specifications.

Project at a glance

Application: Biomass power generation
Equipment Type: Industrial centrifugal boiler fans
Total Quantity: 8 units
Fan Functions: Primary air, secondary air, induced draft, and flue gas recirculation
Design Temperature Range: 25–160°C
Key Engineering Considerations: Airflow, pressure, temperature, system resistance, fan layout, and installation requirements

Industry Background: Fan Requirements in Biomass Power Generation

Biomass power plants utilize boiler systems to convert the energy within biomass fuel into thermal energy for electricity generation. Reliable air supply and flue gas handling are critical to the operation of the combustion and exhaust systems.
Fans serving different functions perform specific tasks:
Primary air fans supply air to the designated primary air system.
Secondary air fans supply air to the secondary combustion air system.
Induced draft (ID) fans transport flue gas through the exhaust system and maintain the required negative pressure within the furnace.
Flue gas recirculation fans return a portion of the flue gas to the designated process circuit, in accordance with boiler design specifications.
The operational requirements for these functions vary. Therefore, equipment selection must comprehensively consider parameters such as airflow volume, pressure, temperature, gas characteristics, and the resistance of the connected systems.
For retrofit projects, one should not simply assume that the original fan ratings are suitable for the new operating conditions; the required operating points and installation layout specifications must be re-verified based on the current system design.

Project Requirements and Engineering Considerations

This project requires four types of centrifugal fans for various sections of the biomass boiler system.
Varying Airflow and Pressure Requirements
The primary air, secondary air, induced draft (ID), and flue gas recirculation systems each operate at distinct duty points. Each fan must meet its specific airflow and pressure requirements.

Varying Operating Temperatures
The design temperature for primary and secondary air fans is 25°C, whereas the design temperature for induced draft and flue gas recirculation fans is 160°C. These temperature differences must be taken into account when evaluating fan construction, drive arrangements, bearing protection, and operating conditions.

Compatibility with the Retrofitted Boiler System
In boiler retrofit projects, changes in combustion requirements, airflow, ductwork, or downstream equipment resistance can affect the required operating duty points of the fans. Therefore, fan selection should be based on established project parameters rather than simply relying on original model specifications.

Installation and Maintenance Requirements
Factors such as fan rotation direction, discharge orientation, foundation dimensions, duct connections, motor specifications, and the provision of access for maintenance and inspection must all be coordinated with the site layout.

The considerations outlined above provide a practical basis for evaluating the technical specifications of fans for biomass boiler retrofit projects.

SIMO Blower Solutions

SIMO provides a total of eight centrifugal fans covering four application categories, with two fans configured for each category.

Primary Air Fan
The design parameters for the primary air fan are: standard airflow of 20,712 Nm³/h (corresponding to an order airflow of 22,700 m³/h), pressure of 3,500 Pa, and temperature of 25°C.
The fan selection and configuration are determined based on the aforementioned airflow, pressure, and installation requirements.

Secondary Air Fan
The design parameters for the secondary air fan are: standard airflow of 8,877 Nm³/h (corresponding to an order airflow of 9,700 m³/h), pressure of 5,500 Pa, and temperature of 25°C.
Compared to the primary air fan, this fan features a higher pressure rating, reflecting specific operating requirements; this should not be interpreted simply as a direct comparison of fan efficiency.

Induced Draft Fan
The design parameters for the induced draft fan are: standard airflow of 48,542 Nm³/h (corresponding to an order airflow of 77,000 m³/h), pressure of 7,200 Pa, and temperature of 160°C.
For the induced draft fan, the required pressure must account for the resistance of the connected boiler flue gas system, including ductwork and applicable downstream flue gas treatment equipment.

Flue Gas Recirculation Fan
The flue gas recirculation system requires two additional fans, designed for an operating temperature of 160°C.
The final airflow values ​​for the recirculation fans should be confirmed against the approved technical specifications prior to release. Selection should be based on actual recirculation operating requirements and the resistance characteristics of the connecting circuit.

Key Considerations for Biomass Boiler Fan Upgrades and Retrofits

In biomass boiler retrofit projects, fan selection should be evaluated comprehensively as an integral part of the overall air and flue gas system.

● Determine actual operating conditions. Required airflow and pressure should be based on the boiler's actual load demands and system resistance, rather than solely on its rated capacity.

● Consider temperature and gas conditions. Before determining fan materials and construction, it is essential to assess operating temperatures, gas characteristics, dust loading, and potential risks of abrasion or corrosion.

● Conduct a thorough review of the flue gas path. Ductwork, dampers, dust collectors, and other downstream equipment significantly influence the pressure requirements for the induced draft (ID) fan.

● Verify compatibility with existing equipment. When replacing a fan, referencing information such as the original fan's nameplate, installation drawings, motor specifications, rotation direction, discharge orientation, and foundation dimensions helps determine whether the new configuration fits the existing installation environment.

Validate performance against established operating points. The finally selected fan must meet the airflow and pressure requirements for the specific operating conditions.

These verification steps are particularly critical when boiler retrofits alter original operating requirements; they help engineers avoid the pitfall of selecting replacement equipment based solely on the original fan model.

Why choose SIMO Blower for your biomass boiler fan project?
SIMO Blower offers a wide range of industrial centrifugal fans suitable for applications such as boiler forced draft, induced draft, flue gas treatment, and other industrial processes.
For projects involving diverse operating requirements, SIMO conducts a detailed assessment of operational parameters and configuration needs, covering:
● Airflow volume and pressure
● Operating temperature and gas conditions
● Fan model and impeller configuration
● Rotation direction and discharge orientation
● Motor power and electrical specifications
● Installation dimensions and maintenance clearance
For retrofit projects, existing fan data and system drawings are utilized to support the technical assessment. If operating conditions have changed, the revised operating point must be confirmed before finalizing the replacement fan selection.

Inquire About Biomass Boiler Fan Solutions

Are you planning a biomass power generation project, retrofitting a boiler, or looking to replace existing boiler fans?

SIMO Blower can evaluate the requirements for primary air fans, secondary air fans, induced draft fans, and flue gas recirculation fans for your project.

To facilitate a technical assessment, please provide the following information: boiler type, fuel type, required airflow, pressure, operating temperature, system resistance, existing fan model, motor specifications, and installation drawings (if available).

Please contact SIMO Blower to discuss your biomass boiler fan requirements and obtain a tailored technical solution for your project.