If you’ve been in the power-generation business for a couple of decades—and made your bones at baseload, coal-fired, water-cooled plants, in particular—you may believe you know all there is to know about Rankine-cycle steam/water chemistry. Perhaps that’s true, for that type of facility.
But with coal-fired plants being shuttered in increasing numbers you may find yourself transitioning to a combined-cycle facility starting one or more times daily and equipped with air-cooled condensers and designed for zero liquid discharge. This is a new ballgame with respect to chemistry. You can almost forget what you know; in any event, positively embrace re-education.
Neutralizing amines and filming products are relatively new to many in the industry because their potential for reducing corrosion in heat-recovery steam generators (HRSGs), condensers, and steam turbines was not of great importance to personnel at traditional steam plants operating baseload with tight control of chemistry.
In these days of must-take renewables they warrant consideration. If you attended either of the first two meetings of the HRSG Forum with Bob Anderson you likely are aware of how amines and filming products have benefitted some users. EPRI’s Steve Shulder provided a backgrounder on how these products work at the first conference. It’s a good primer on the topic and will answer some of your basic questions.
Next, access online at no cost, the IAPWS (International Association for the Properties of Water and Steam) Technical Guidance Document (TGD) “Application of Film-Forming amines in Fossil, Combined Cycle, and Biomass Power Plants” (TGD 8-16). This is said to be the first public guidance document published for the industry on the subject. It was developed under the leadership of Dr Barry Dooley of Structural Integrity Associates Inc, who serves as the executive secretary of IAPWS.
Dooley’s presentation at the first HRSG Forum included information that he would share at the First International Conference on Film Forming Amines and Products in Lucerne, Switzerland, two months later. The well-respected chemist and metallurgist chaired both the Lucerne and second (Prague, Czech Republic, Mar 20-22, 2018) topical meetings. The 2019 meeting will be held in Athens, Greece, next March.
It’s probably fair to say that the chemistry of amines and filming products is somewhere in the middle stage of development: Some things are known, but there’s a lot more to learn despite the use of some products for three decades. In fact, even the generic name associated with these chemicals has changed recently. Dooley told the editors that feedback from the 2017 Lucerne meeting indicated much confusion regarding the various terms used for film-forming substances—for example, film-forming amines (FFA), film-forming amine products (FFAP), film-forming products (FFP), and others.
So IAPWS used its leadership position in the international scientific community to adopt the term “film-forming substances (FFS)” shortly before the Second International Conference on Film Forming Amines and Products and then changed the name of the meeting to the Second FFS International Conference. It attracted some 70 participants from 30 countries, illustrating the increasing interest worldwide in understanding and applying FFS.
Under the FFS umbrella are two subsets of the technology: amine-based substances (FFA and FFP), and non-amine-based FFPs.
The second international meeting provided a highly interactive forum for the presentation of new information and technology related to FFS, case studies of plant applications, and open discussion among users, equipment and chemical suppliers, university researchers, and industry consultants. The key messages from that conference:
- If everything is working well at your plant then consider really hard whether using an FFS will make any improvements. If not, consider that the application could cause problems.
- One clear case for application: If the shutdown frequency of the plant is going to increase, FFS can (perhaps) greatly improve offline protection.
- If you are considering use of an FFS for any application, be sure to read Section 8, “Operational Guidance for the Continuous Addition of an FFS,” of the IAPWS technical guidance document referenced above. It will help you avoid mistakes and potential problems.
- Before applying an FFS to your plant, be sure its chemistry is well understood. Do not hesitate to hire one or more experts for advice before making a decision. Perhaps the biggest challenge facing users in FFS selection is the proprietary nature of these formulations. Suppliers typically are unwilling to disclose “what’s inside.” Don’t inject anything into the steam/water circuit that you are not completely comfortable with.
- Get a thorough work-up on system chemistry before adding an FFS, this to develop a baseline condition for comparison purposes later.
FFS 2018 allowed plant owner/operators to get answers to many of their questions relating to the use of FFS from the assembled community of international experts. A panel session focusing on key questions and uncertainties about FFS got “two thumbs up” from several attendees.
Other conference highlights included the following:
- Updates were presented on recent experiences at fossil, nuclear, and industrial plants worldwide. The experience at nuclear plants has been with octadecylamine (ODA), whereas a wide range of FFS is being applied to fossil and industrial plants. The experience of FFP on condensate polishing and methods of determining FFA on surfaces were discussed.
- Attendees shared ongoing research activities at different international organizations concerning decomposition products of FFA, distribution of FFA, measuring/quantifying the concentration of FFS in cycle water, adsorption kinetics of film formation, and the effects of FFS on flow-accelerated corrosion (FAC).
- Extensive discussions reviewed the possible benefits of using FFS. They also identified many problems still occurring worldwide in plants using FFS without the detailed knowledge suggested by Section 8 of the IAPWS TGD. However, there wasn’t much open discussion on these problems. One of Dooley’s goals for the next meeting is to dig deeper into specific experience issues.
- Two main conclusions from the conference: (1) Hydrophobicity does not always equate to protection, and (2) FFS cannot be quoted as “reducing” FAC simply by indicating a reduction in monitored iron levels. Regarding the second point, there should be before/after data for any application, with supporting photos if possible.
- The need for adapting sampling and monitoring concepts to the specific FFS chemistry applied was recommended.
- Gaps in knowledge and topics for further research were identified. For example, fundamental work remains to better understand the mechanisms at play with FFS. This includes film formation kinetics, equilibrium and stability, film structure (that is, thickness or number of layers), how absorption is affected by other amines, and the correspondence to the reduction in corrosion rate.
- Work is required to understand the mechanism of the interaction between FFS and surface oxides. This was discussed as “interfacial science” and should involve the interaction of the FFS film with existing surface to include, initially, Fe3O4, Fe2O3, FeOOH, CuO, and CuO2. Also needed is work on the interactions that occur under feedwater conditions up to about 575F, where magnetite is soluble.