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Computational Fluid Dynamics From the Laptop to the Smokestack: How Computational Fluid Dynamics Boost Environmental Performance

Author / Editor: Steward Bible / Dominik Stephan

The impact of CFD in the development of Fuel Tech’s innovative NOx Reduction technology – Fuel Tech is a world leader in providing advanced engineering solutions for Air Pollution Control in power plant utilities. Their NOx reduction technologies are now installed worldwide on over 800 units, providing customers with the most cost effective and environmentally sustainable methods to produce energy and processed materials. The recently patented GSG technology, which has been developed with extensive CFD modeling, is capable of dramatically improving upon typical SCR unit performance by optimizing flue gas velocity profiles, reagent consumptions, and catalyst lifetimes while minimizing system pressure losses

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Advanced engineering solutions for Air Pollution Control in power plant utilities.
Advanced engineering solutions for Air Pollution Control in power plant utilities.
(Source: depositphotos.com)

In one of the first Graduated Straightening Grid (GSG) retrofit applications at Kansas City Power & Light Company’s La Cygne Station Unit 1, the installation of the new technology has resulted in operational cost savings of more than $5 million associated with reduced system pressure drops, reduced build–up of particulate on catalyst layers, less catalyst erosion and longer catalyst lifetime. But the most impressive is how Fuel Tech has developed this technology and attained its current industry standing. In this article, the reader will be walked through the development of the GSG which is now part of the all new Fuel Tech Selective Catalytic Reduction (SCR) applications.

Optimising Pollution Control

With the urge to reduce emissions to meet directives in Europe, as well as new rules proposed by the US Environmental Protection Agency (EPA), many fuel resources, including coal, are faced with being expelled from the market due to environmental control costs. However, environmental rules typically trigger the development of new cost–effective technologies for emission reduction.

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As a result, one of the foremost applications of Computational Fluid Dynamics (CFD) and Experimental Fluid Dynamics (EFD) modeling over the past ten years has been in the area of optimizing Air Pollution Control (APC) systems that are used to reduce emissions from fossil fuel fired stationary sources such as power plants and steel mills. The most common of these are depicted graphically as a general arrangement of equipment on a power generation unit in Figure 1.

Figure 1: General arrangement of common APC equipment in solid fuel fired power generating combustion unit.
Figure 1: General arrangement of common APC equipment in solid fuel fired power generating combustion unit.
(Source: Fuel Tech)

The SCR technology was developed in the 1980s in Japan to effectively reduce NOx concentrations in flue gas by the injection of ammonia (NH3) reagent and the reaction via a catalyst substrate. This development was critical in helping coal remain in the market as the most cost–effective fuel source.

Despite the relatively developed nature of this technology, there still exist challenges for owners and operators of coal–fired power plants with SCR units such as:

Minimization of the system pressure losses with the aim to reduce fan power consumption and power plant operating costs:

  • Achieve optimally distributed concentrations of velocity, NOx, NH3 reagent and temperature profiles entering the SCR reactor, nabling better reduction efficiencies and lower ammonia usage
  • Ensuring uniform gas velocity vectors at the catalyst in order to reduce the risk of catalyst erosion and consequently extend catalyst life by lessening catalyst wear and deactivation
  • Avoid particulate dropout and ash accumulation in SCR units which increase system pressure losses, unit downtime for cleaning purposes, and reduce catalyst lifetimes

With the significant progress in computing hardware capabilities, engineers at Fuel Tech Inc, now take advantage of the CFD in order to develop flow distribution devices that successfully address these SCR-operation related issues.

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