SCR efficiency problems cost ammonia plants millions of dollars annually.
Poor NOx Removal, High Pressure Drops, and Poor Ammonia Mixing
This study highlights an application at a Steam Methane Reformer on the West Coast of the United States, where the facility suffered from SCR efficiency problems. This was primarily due to fibrous material, mostly refractory fibers that have broken free from degradation over time, plugging the face of the catalyst, causing poor NOx removal, high pressure drops, and poor ammonia mixing.
This resulted in system derates and forced outages to clean the catalyst face. Every day the facility was in outage cost the company approximately $1M in lost production. In addition, the costs of shortened catalyst life, lost production during derates, and excessive ammonia usage contributed to an estimated $3M + annual cost due to this buildup.
Comprehensive Approach to SCR Efficiency
Integrated Global Services (IGS) was contracted to provide a comprehensive system to eliminate the cost and efficiency impact of this fibrous material by:
Not only is a comprehensive approach more effective than any one individual solution, but it also allows for robust guarantees and eliminates “finger-pointing” between companies.
Lower SCR Buildup with Refractory Encapsulation
IGS utilizes a ceramic coating to encapsulate refractory in areas with the most severe refractory degradation. This coating effectively reduces the volume of fibrous material in the gas stream.
Due to the size of these units, it is often cost-prohibitive to encapsulate 100% of the refractory area, which still allows fibers to reach the catalyst. The reduced volume slows the accumulation of the buildup, but over time still produces enough catalyst buildup to impact production significantly.
Extend Catalyst Life with Particle Filtration Screens
The IGS patent-pending dual-stage filtration screen and online cleaning system capture the fibrous material in the gas stream prior to it reaching the catalyst face. The screen online cleaning system pushes the captured material out of the primary gas stream and into a collection area where it can later be removed. Preventing buildup on the catalyst ensures proper flow distribution, minimizes pressure drop and extends catalyst life.
Mixing Plate System
The IGS patent-pending flow mixing system is designed to maximize ammonia mixing prior to the catalyst to reduce ammonia usage and ensure an even ammonia concentration distribution through the catalyst, which improves DeNOx and preserves the catalyst reactivity. This can be installed in conjunction with the filtration screen or even as a standalone improvement.
In this case, third-party CFD analysis shows the filtration screen and mixing system produced a reduction in RMS values from greater than 16% to less than 1%, a dramatic improvement.
Online SCR Cleaning
Although the comprehensive solution above has been shown to be very effective in maximizing production and eliminating forced outages, it is worth having a plan B for upset conditions with millions of dollars on the line. For this reason, we include access ports to allow IGS Hot-tek patented online vacuuming of the catalyst and screen face. IGS includes vacuuming services as part of the cleanliness guarantee with this solution package.
SCR Efficiency Improved
Since coming online in Spring 2021, the plant has not experienced any increase in pressure drop across the Reformer Screen, nor have they seen an increase of dP across the SCR catalyst modules. Online inspections have shown no material accumulation on the catalyst face. The plant has not been production-limited due to the SCR, has their ID fan running per design, and has optimal NOx reduction of the process gas with reduced ammonia consumption.
Return on Investment in Two Months
The IGS installation of refractory coating, particulate filtration screens, and ammonia mixing system has eliminated the effects of fibrous material on the SCR, in turn saving millions of dollars annually. Given the turnkey cost of the system, the ROI was recognized in just two months of operation.