Design – Ammonia delivery mod improves safety, produces savings

Effingham County Power

Owned by ArcLight Capital Operated by Consolidated Asset Management Services

525-MW, gas-fired, 2 × 1 combined cycle located in Rincon, Ga

Plant manager: Eric Garrett Key

Project participants: James Goins, production manager Nick Bohl, production manager Ken Earl, maintenance manager Mark Hopkins, maintenance team leader

Challenge.

Since commissioning, the plant had ammonia delivered in 300-gal chemical totes for HRSG boiler water treatment. The cost of this product is very high, $1.70/lb, in large part because of the shipping and handling involved. In 2009, the plant used 15,375 lb of ammonia for boiler water treatment at a total cost of $26,138.

In addition to the expense, there also are risks associated with the storage and chemical transfer associated with totes. Plant personnel explored the options available to reduce the costs and the safety hazards associated with handling ammonia.

Solution.

The facility uses ammonia for both the ammonia supply to the boiler water and for NOx control in the HRSG SCR systems. SCR ammonia, delivered by truck at a cost of 13cents/lb, is stored in two 17,000-gal tanks. From those tanks it is pumped to each HRSG’s ammonia skid and then to the ammonia injection grids. Following verification by independent laboratories that the bulk ammonia was a satisfactory replacement for the product delivered by tote, the plant initiated an engineering effort to modify the bulk ammonia forwarding system to also provide ammonia supply to the HRSG boiler water ammonia holding tank. Only minimal piping modifications were required to implement the design change.

Results.

After performing the modification, the plant began to see the immediate advantages to this setup.One significant benefit of the new system was that the ammonia is delivered by truck, significantly reducing the chances of a spill by eliminating the need for plant personnel to handle the chemical totes. Additionally, the financial advantage from buying the chemical in bulk is equally impressive. The cost of bulk ammonia is $0.13/lb versus $1.70/lb for the ammonia delivered in totes. For an annual ammonia usage of 15,375 lb, the amount used in 2009, the plant will save $24,139 per year. With a project cost of less than $20,000, the payback is less than one year and the annual savings will continue through the life of the facility.