Heat recovery steam generator (HRSG) cleaning is an effective way to restore lost performance because it reduces the back-pressure on the gas turbine, thereby increasing the net power output or reducing cost of fuel per megawatt generation. Every additional half inch (water column) of pressure drop through a typical F-class HRSG reduces the bottom line by about $100,000 per annum, depending on the price of fuel. An effective cleaning on a fouled HRSG could be expected to regain at least 3-6 inches of pressure drop.
Dirty HRSG tubes penalize plant performance in several ways. Fouling of the gas-side HRSG tubes increases a plant's heat rate by reducing the heat transfer and increasing the back-pressure of the gas turbine. Reduced heat transfer efficiency also reduces the output of the steam turbine, and excessively fouled HRSGs can exceed their designated back-pressure limit, triggering an expensive and automatic "turbine trip" or curtail otherwise available generation capacity.
It is important to evaluate what cleaning methods have typically been available and what limitations and risks come with them. Common off-line cleaning methods such as dry ice blasting require scaffolding or Sky Climbers that are expensive, time-consuming, and may be only marginally effective due to factors like below-360-degree coverage, limited penetration of multiple harps and an incomplete cleaning of the densely contaminated finned tube bundles. Another is a pressure-wave cleaning method that utilizes repeated insertion and exploding of bags containing combustible gas that are dangled at various elevations and detonated in open voids between bundles. This can be expensive; time-consuming; and repeatedly cause indiscriminate, superfluous impact to surfaces, expansion joints, instrumentation, equipment and structural components.
A new solution based on 14 years of proven technology, EPIC⢠off-line HRSG cleaning safely provides highly beneficial results to combined-cycle plants without extraneous explosive effects. The off-line application of this substantiated pulse-detonation cleaning technology, utilized routinely on-line for 24/7/365 performance for well over a decade, has demonstrated dramatic improvements in severely fouled, tightly packed finned harps in HRSGs when compared to existing methods.
EPIC's off-line pulse-detonation, or "shockwave," cleaning technology provides several advantages over other cleaning methods:
- Effective, safe and targeted cleaning energy: Over the past 14 years, shockwave cleaning has proven to provide penetrating, all-encompassing cleaning energy that can extend far into the tube bank and effectively dislodge deep and impacted deposits from heat-transfer surfaces.
- Frequently reduced cleaning time, shorter outages: The technology employs an automated cleaning rig that can navigate quickly across the heat-transfer surface without the need for scaffolding or man-baskets, significantly reducing overall cleaning time compared to other methods.
- Extremely safe for personnel and the entire surrounding structure: The shockwave cleaning energy is remotely activated and concentrated safely within the specially engineered and patented 2-inch combustion tube. It's then exhausted directly and focused only at the heat-transfer surface so the surrounding structure is not exposed to indiscriminate and potentially harmful explosions.
Fouling on the gas side of HRSG tubes compromises plant performance. But you can restore lost performance through innovative HRSG cleaning that reduces back-pressure on the gas turbine, increasing net power output. Through this method, combined-cycle facilities are regaining 3-6 inches of pressure drop and increasing their bottom line by $600,000 or more annually through reduced fuel costs. This exceptionally safe and effective cleaning technology provides penetrating, all-encompassing cleaning energy that dislodges deeply impacted and tenacious deposits from heat-transfer surfaces far into the tube bank. When it comes to safety considerations of various HRSG cleaning techniques, EPIC's off-line pulse-detonation cleaning technology reduces hazard exposure, cleaning time and outage duration.
For more information, visit www.ThompsonIndustrialServices.com/EPIC or call (800) 849-8040.
