Selective Catalytic Reduction Systems - Elements of Design

摘要

Selective Catalytic Reduction (SCR) systems have demonstrated their effectiveness in removing up to 93% of NOx found in the flue gas formed from the combustion of coal, fuel oil, orimulsion, gas, and bio fuel blends. ALSTOM has designed and installed SCR systems in over eighty applications worldwide including:rn1. Power Boilers (130 to 1300 MWe in size; 27000 MWe in total generating capacity) 2. Waste to Energy Incineratorsrn3. Process Heaters 4. Glass Furnaces 5. Gas Fired TurbinernAn SCR system consists of inlet/out ducting, an Ammonia Injection Grid (AIG), a reactor containing the SCR catalyst layers, and an ID Fan to offset system pressure losses. Achieving the guaranteed performance level for a particular application requires a design that homogeneously distributes flue gas NOx and injected ammonia across the catalyst bed interface at a controlled temperature. The key design elements of an SCR System that ensure complete NOx conversion to nitrogen and water with a minimum of unreacted ammonia include:rn1. Computational Fluid Dynamic (CFD) Modeling 2. System Aerodynamic Designrn3. Ammonia Injection Grid Design 4. Reactor Design and Catalyst Selection 5. Project ExecutionrnTo achieve overall process objectives, a successful SCR Project depends on a thorough understanding of the relationship between each design element and proper characterization of flue gas flow. The combination of experience with gas treatment methodology and capability with fluid dynamic design tools enables ALSTOM to deliver SCR systems that meet the performance objectives for NOx control while achieving low pressure drop, optimal gas distribution, minimal erosion, and low dust accumulation. This paper will discuss how ALSTOM's design experience can be marshaled in Asia to support programs that are underway to install SCR technology on coal-fired boilers in Korea and Taiwan as well as the demonstration SCR projects currently under development in China.