(5a) Methods of Fan Controls

AIChE PAPER NUMBER:

METHOD OF FAN CONTROLS

Brad Smith

Senior Sales Manager

Twin City Clarage, LLP

Mike Lowe

Senior Sales Application Engineer

Twin City Clarage, LLP

Prepared for Presentation at the 2022 Spring Meeting

San Antonio, Texas, April 14-14, 2022

AIChE and the EPC shall not be responsible for statements or opinions contained papers or printed in its publications.

METHODS OF FAN CONTROLS

Brad Smith, P.Eng.

Senior Sales Manager

Twin City Clarage, LLP

Mike Lowe

Senior Sales Application Engineer

Twin City Clarage, LLP

Abstract:

With the increase in environmental emission regulations, the designs of the Ethylene plant auxiliary equipment (such as fired heaters, furnaces, and fired boilers) has put more strain on the turn down requirements of the centrifugal fans. The low NOx emission regulations sometimes require low turn to start up the auxiliary equipment. This paper will explain the various methods to control the centrifugal fan; including pre-spin and resistance dampers, speed control, and airflow recirculation:

• Inlet louver damper (ILD)
• Variable inlet vane damper (VIV)
• Outlet louver damper (OLD)
• Variable speed drive (VFD)
• By-pass recirculation duct and FGR dampers

Along with providing a complete description of each method of control, this paper will also use of a combination of two methods, such as:

• Inlet louver damper (ILD) or variable inlet vane damper (VIV) and variable speed drive (VFD)
• Inlet louver damper (ILD) and by-pass recirculation duct
• Inlet louver damper (ILD) or variable inlet vane damper (VIV) and outlet louver damper (OLD)

Finally, we will present a case study where combustion air (FD) fan on an industrial boiler is designed with using an ILD, OLD, and by-pass recirculation duct installed to reach low-fire startup condition.