NOx Reduction
CRI Selective Catalytic (SCR) NOx Reduction Technology

Since its commercial introduction in the 1970's, Selective Catalytic Reduction (SCR) of nitrogen oxides (NOx) has gained wide acceptance worldwide as the most effective and technologically proven method for high-percentage NOx removal from flue gases.

CRI's technology, known as the Shell DeNOx System (SDS), operates on the SCR principal. It uses ammonia (NH 3) as the reductant and a catalyst to promote the reaction of NH 3 with NOx, forming nitrogen and water.

An efficient retrofit

The CRI SCR catalyst can operate at lower temperatures and with lower pressure drop than conventional SCR catalysts. Consequently, the CRI SCR system can be installed immediately before or in the stack, thereby avoiding any modifications to combustion or heat-recovery equipment or negative effects on other upstream plant operations. This makes the CRI technology very cost-effective for retrofit SCR applications.

Typical Application Conditions and Performance of the CRI Low-Temperature SCR Technology:
Operating Temperature
	Typical Application	325-450° F /160-230° C
	Range	300-700° F/ 150-375° C
Pressure Drop
	Typical Application	2-3 in. H2O/ 5-7.5 mbar
	Range	As low as 1 in. H2O/2.5 mbar
Performance
	NOx Conversion	>90%
	NH3 Slip	5-10 ppm or lower

Unique catalyst and module technology

The CRI technology differs from conventional SCR systems in two important aspects: the catalyst and the catalyst reactor module. The catalyst is in the form of pellets and can be produced in a range of sizes and shapes to meet specific performance requirements. Due to the high activity of the catalyst, high NOx removal efficiencies with simultaneous control of NH 3 slip can be obtained at relatively low temperatures.

The catalyst reactor module is based on the Lateral Flow Reactor (LFR) principal. The LFR is a packed-bed type reactor which offers the advantage of low pressure drop even at high space velocities. Furthermore, the LFR design makes possible the most efficient utilization of the SCR catalyst, which minimizes the amount of catalyst required and facilitates fast loading and unloading of catalyst from the reactor.

Development of the LFR technology has resulted in a modular construction system, providing a high degree of flexibility in the design of SCR systems for specific applications, particularly retrofit.

A broad range of applications

The CRI SCR technology has been successfully applied to combustion and chemical process operations including gas turbines, refinery heaters, boilers, ethylene cracker furnaces, nitric acid plants and waste incineration facilities.

Resulting from the high catalyst activity and flexibility of the LFR module design, the optimal and most cost-effective combination of NOx removal, NH 3 slip, temperature, pressure drop and available plot or duct space can be developed for virtually any application.