Bachmann® 4-Port Diverter System:
A complete damper system for SCR applications
SCR service subjects damper equipment to very demanding operating conditions. With this in mind, Bachmann Industries uses technology previously developed for use on Gas Turbine Exhaust Systems and applied for use in today’s SCR applications. This technology – the use of large single flap blade dampers to isolate and modulate flow – is at the heart of the Bachmann® 4-Port Diverter System. The first large single blade Gas Flow Diverter (GFD) was conceptualized and designed by Bachmann Industries, Inc. in 1982. Since then, we have supplied more than 250 Single Blade Diverter Systems.
There are several correlations that can be made between Gas Turbine Exhaust Systems and SCR Systems. Gas turbine systems operate up to 1200°F whereas SCR systems can operate up to 1100°F they generally operate at 600°F to 800°F. Both systems must have 100% guaranteed system isolation during operation. A need to modulate the system flow when switching between normal system operation and by-pass operation is common to both systems. Gas turbines have very high flow velocities that affect the blade sealing system; the SCR system has to deal with entrained fly ash that also affects the sealing system. The Bachmann® 4-Port Diverter System is designed to deal with these problems.
While the Gas Turbine Diverter is a 3-Port system, (Turbine outlet, HRSG inlet and By-pass to stack) the Bachmann® SCR 4-Port Diverter System comprises
- a self-contained housing with an inlet port from the boiler,
- an SCR takeoff port,
- an SCR return port and
- an exit port to the air heater.
The diverter system provides SCR online or bypass functions. In normal operation, the boiler exhaust gas goes straight through to the air pre-heater and then out through the balance of plant equipment. At this time both the SCR inlet and outlet ports are 100% isolated from the flue gas flow, thus protecting the catalyst from low temperature flue gas.
In the bypass mode the boiler exhaust gas goes to the SCR Reactor and then to the air pre-heater, and then out through the balance of plant equipment. In this mode, the SCR bypass duct is isolated from the gas flow and both the SCR inlet and outlet ports are open.
The 4-Port Diverter contains only two single blade flap dampers. The flap blade rotates out of the medium flow inside the duct. This reduces pressure drop and abrasion. The system is more space efficient and substantially more reliable than conventional louver and guillotine damper systems.
There are many different ways to configure ducting to handle the gas flow for SCR systems.
Due to the major reduction of ducting, the Bachmann® 4-Port Diverter System offers significant efficiencies resulting in not only initial cost savings but in the long term overall system operation and maintenance.