HOT TOPIC HOUR

Catalysts were a Major Focus at the August 6 McIlvaine Hot Topic Hour Discussion of GT Exhaust Systems

The Thursday 70 minute discussion of gas turbine (GT) emission control and exhaust system options followed the new format.  A slide deck with 100 power points was the road map for the discussion with stops along the way to cover new options. The road map displayed many options from noise suppression to ammonia injection.

The stopping points were concentrated on catalysts, testing, and ammonia injection.  The meeting started with David Couling of E.ON.  His group of 1,000 engineers in the UK supports the power operations in many countries. Presently many of the E.ON power plants are facing prospects of EU regulations on combustion turbines with limits as low as 5 ppm. The problem with meeting these regulations at the 15,000 to 20,000 MW of combustion turbine systems which E.ON operates in the region is the tight space. So David was interested in what the various suppliers would recommend to make the installations more compact.

A number of catalyst, components and testing experts provided details on the newest technology and how it may influence which option to take.

• Should you use high temperature catalyst or tempering air with a simple cycle arrangement?

• What catalyst configuration is best?

• How different are the formulations between one catalyst supplier and another?

• How do you deal with increased sulfur and other contaminants?

• Can you combine CO and NOx conversion in one catalyst?

• What is the best reagent choice? Anhydrous, aqueous or urea conversion to ammonia?

• How important is CFD modeling ahead of final engineering?

A number of people weighed in on these issues.

Mitsubishi has installed more than 600 SCR systems for gas turbines.

Catalyst

Johnson Matthey uses a compact honeyocmb catalyst which will be attractive to those European GT owners who must retrofit catalytic units into existing systems. Their oxidation catalyst efficiency ranges from 90 to 95 percent depending on the the gas temperature.

Clariant makes the raw material and the catalyst. Their high temperature catalyst is durable and efficient at temperatures in excess of 600°C.

Ceram can customize module size. This is an important feature for retrofit applications in Europe where space is premium.

Cormetech is a major supplier of gas turbine catalysts in the U.S., China and Europe. Emerachem also has many installations.

Haldor Topsoe has a combination NO_x and CO catalyst.

• GT series SCR catalyst impregnated with active precious metal.

• Controlled concentration and placement of active metal reduces undesirable side reactions.

• Truly “Dual Function Catalyst” DeNOx and oxidation of CO and VOCs.

• Catalyst is not poisoned by SO2.

• Extremely low SO2 oxidation, 5 to 10 times less than traditional Pt-based catalyst, less fouling.

• Very low oxidation of ammonia, conversion mostly to nitrogen and water under 800°F.

• Dual function solution provides lowest possible pressure drop. Generally one-half of traditional solution.

• With placement of catalyst downstream of ammonia injection, liquid ammonia injection can be used.

• Up to 95 percent DeNOx and 95 percent CO oxidation with very low ammonia slip.

• Ammonia consumption increases on applications above 650°F.

• References stand at 34 units sold, 4 are operational including two MHI 501G CCGT in Texas.

Mitsubishi is a major supplier of SCR systems for gas turbines with more than 600 installations. The company has combined with Hitachi and is now Mitsubishi Hitachi Power Systems (MHPS). The former Hitachi is a major supplier of catalysts. So the new merged entity is supplying both catalyst and systems.

Modeling and Testing

Modeling has lots of benefits. Air Flow Sciences is providing both the modeling and subsequent testing services for clients in Europe and Asia as well as the U.S.

Breen has developed an accurate way to determine SO₃ at the HRSG.  Even though the levels are quite low the constant cycling creates deposits on tubes. The net effect is to raise the flue gas concentration near the tubes and therefore the acid dewpoint. The potential corrosion is of concern and has sparked interest in the Breen analyzer.

Ammonia Injection

Wahlco has been successful with their Ammonia on Demand or AOD process which provides ways to convert urea to ammonia on site. There are two approaches, one for smaller installations and one for larger ones.  The safety and availability of urea make it an attractive choice.

This route map and summary is being posted in the gas turbine emission control and exhaust system decision guide Gas Turbine Emission Control. This is a protected site which is linked from the main website which is described in 59D Gas Turbine and Combined Cycle Decisions.

The Decision system is organized to provide four knowledge needs: Alerts, Answers, Analysis, and Advancement.

This summary appears in the Gas Turbine Updates along with other new developments to which users need to be alerted. Some of the more complete power point presentations and papers submitted by the participants are being posted in the database intelligence system to provide quick answers with the easy to use tier system including subsidiary websites. The recording provides extensive analysis. Future webinars will build on this one to provide additional analysis. The fact that all the webinars are recorded makes it possible to work out very comprehensive training (Advancement) programs.