SCOPE for LANCASTER GAS TURBINE BASALT (GTB®) MATERIALS in HRSG BOILERS and ASSOCIATED DUCTS

With 15 years field experience, Lancaster GTB® thermal/acoustic fibrous basalt materials are the benchmark choice for highly dynamic hot gas silencing applications. Possessing the reputation of being "fit for purpose" in large gas turbine silencers, the high fibre diameter of these materials ensures low flow resistivity, promoting freedom of silencer design and providing exoneration from classification under the European Directive on categorisation of MMVF's, based on their potential for carcinogenicity.

More recently, Lancaster GTB® materials have quickly established themselves as a preferable alternative to the use of refractory ceramic fibres, soluble ceramic substitutes, and combination make-ups (ceramic substitutes plus bonded mineral fibre batts) within internally lined HRSG boilers and associated ductwork.

Scope for the success of Lancaster Gas Turbine Basalt materials in boiler and duct lining applications can be explained by reference to three key drivers, as described below.

1. ENVIRONMENTAL
EU Directive 97/69EC (67/548/EEC Amendment) classifies refractory ceramic fibre as a Category 2 Carcinogen. In contrast, Lancaster GTB® materials are unclassified under the Directive (by the nature of fibre size).

2. TECHNICAL
Proven capability within gas turbine silencer baffles, internally lined diffusers, transition ducts and silencer casings has visibly demonstrated the capability of Lancaster GTB® materials. Deployment into HRSG applications allows for a comfortable safety margin, as indicated by the comparison of conditions given below.

Hot Gas Silencing Environment

• High gas velocity, significant impingement
• Very severe flow dynamics
• Perforated s/steel sheet, low thermal mass
• Rapid heat-up, especially if close to the turbine
• Direct impingement from turbine washing solutions

Boiler Lining Environment

• Low gas velocity, no direct impingement
• Mild flow dynamics
• Solid s/steel sheet, higher thermal mass
• Slow heat-up of structure and insulation.
• Little direct impingement from turbine solutions washing solutions.

Lancaster GTB® materials can reliably sustain working temperatures of 750'C and cope with transient conditions to 800'C.

3. COMMERCIAL

GTB® materials in roll form can offer significant commercial advantage when compared with ceramic fibre materials. When supplied in pillow form, which on installation requires no cutting and generates no loose fibres nor waste, there is still an important cost saving compared with using ceramic fibre. Such materials significantly reduce installation time and hence reduce post-supply costs, providing a net saving on contract costs.

4. FIELD EXPERIENCE

The project list (right) serves to illustrate the progressive use of Lancaster Gas Turbine basalt materials into this area of the power generation market:

5. SUMMARY

Lancaster Gas Turbine Basalt materials offer environmental, technical and commercial advantages when compared with ceramic materials or ceramic substitutes. GTBÆ materials have a proven track record within the most arduous regions of the gas turbine exhaust path (including being exposed to washing fluids), making these materials exceptionally well suited to replace ceramic fibres in CCGT hot duct & HRSG boiler applications.

In respect of future development, the acoustic absorption capabilities of these materials presents considerable scope for improved boiler lining design, enabling useful acoustic attenuation capabilities to be incorporated into the duct and boiler casings.

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