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CataStak SCR Systems for Boilers

With emission limits continuing on a downward trend, the Nationwide CataStak™ SCR System is the choice for ultra low NOx emissions compliance.

After years of field testing on numerous rental projects, selective catalytic reduction was recognized as the one solution that met all of Nationwide Environmental Solutions objectives: It is economical, reliable, easy-to-operate, efficient and reduces emissions to single digit NOx levels.

The enormous success of the company's development of modular SCR systems on Nationwide Boiler's rental fleet suggested to company management that a market existed for a field-retrofit system for package boilers. Thus the CataStak™ SCR System was born.

Today, Nationwide Boiler leads the nation with the most low NOx solutions for less than 5 pm NOx, and the CataStak™ has become the standard for compliance assurance, reliability and product quality. An ammonia-free SCR option is also available for plant owners and operators who desire an ammonia-free alternative.

System Overview

The CataStak™ SCR system can be installed either vertically or horizontally and has been installed in boiler applications ranging from 800 HP to over 200,000 PPH. It consists of a single-reactor housing with NOx or CO reducing catalyst and a standard ammonia delivery system (pure anhydrous ammonia, aqueous ammonia or urea). Nationwide Boiler's NOx reduction control system for the precise control flow of ammonia and an ammonia injection grid is also included. Ammonia can also be supplied by a vaporizer unit.

Catalyst Features

Nationwide Boiler offers either honeycomb or pelletized catalyst, based on the specific application and equipment type. The unique design of the catalyst provides high NOx or CO removal activity, low pressure drop, low SO2 oxidation rate and excellent durability. The catalyst features are key to:

  • High NOx or CO removal level with minimum ammonia slip
  • Low activity towards SO2 oxidation, minimizing the risk of fouling downstream equipment
  • High poison resistance ensuring a long and stable service life

Ammonia Delivery System

Nationwide's standard ammonia delivery system consists of the anhydrous ammonia storage, Nationwide Boiler's NOx reduction control system with a mass ammonia control valve and the ammonia injection grid.Anhydrous ammonia is typically stored in standard 150 lb. gas cylinders that connect to a manifold which accommodates up to three cylinders, allowing each cylinder to be isolated and  switched over on-line.  Anhydrous ammonia  gas cylinders are the most cost-effective and practical storage method for most systems, however alternate delivery systems can also be supplied.

Ammonia Control Flow Unit

Ammonia flow control components are skid mounted in a compact space-saving  arrangement where all operating devices are within close proximity of each other and within easy access for the operator.  The NOx reduction control system includes a vapor ammonia header with a pressure regulator, and  a “smart” flow control valve.  A dilution  air blower is also provided. The flow rate of the ammonia is controlled based on the fuel flow measurements and pre-determined NOx emissions.

Ammonia Injection Grid

The Ammonia Injection Grid (AIG) consists of a header feeding a group of injection lances distributed across the flue gas duct.  The AIG provides uniform injection of the ammonia/air mixture over the duct cross section.

The CataStak™ SCR System is designed as a cost-effective answer to reducing stack emissions and has been proven in many types of demanding applications, easily meeting or exceeded NOx emission guarantees. It is designed for stand-alone operation with minimum operator intervention. benefits include:

  • Lower GHG - dramatic reduction in stack emissions
  • Easy field retrofit - no burner or fan changes required
  • Simple controls - minimum operator intervention
  • Low operating costs with stand-alone operation