Experience with the Application of a Film Forming Amine in

136

Experience with the Application of a Film Forming Amine in the Connah's Quay Power Plant

PowerPlant Chemistry 2018, 20(3)

PPCHEM

© 2018 by Waesseri GmbH. All rights reserved.

Experience with the Application of a Film Forming Aminein the Connah's Quay Triple Stage Combined Cycle GasTurbine Power Plant Operating in Cycling Mode

ABSTRACT

Due to the changing conditions of the energy market, many power plants have various periods of non-operation, ranging from a few days to months. Unprotected unit shutdown represents a serious corrosion risk and thus a risk forthe integrity of key plant parts, such as the boiler or steam turbine. However, the established conservation methods ofthe water-steam cycle are not always applicable under the constraints of the modern power market, with unpredictableshutdown periods, while at the same time the plants have to remain available and may be required to run at shortnotice. Film forming amines (FFAs) offer excellent potential for the required flexible conservation process. The Unipercombined cycle gas turbine power plant located at Connah's Quay, UK, has assessed the applicability of FFAs forboiler and steam turbine protection.

Besides a product based on a combination of FFAs with alkalising amines, a newly developed product containingsolely the FFA was applied. Some key benefits could be demonstrated. The protection of the boiler and steam turbinecould be achieved for a period of at least one month. The technology was able to protect all components of the water-steam cycle, including the areas of predominantly dry steam. Compared to dehumidification or nitrogen capping, minimal manpower was required for conservation. By the application of the newly developed product, the drawback ofincreased cationic conductivity levels was overcome, which remained close to the normal operation values. Due to theencouraging results, FFAs are now applied in all 4 units of the Connah's Quay power plant.

Wolfgang Hater, Bill Smith, Paul McCann, and André de Bache

INTRODUCTION

Organic cycle chemistries based on film forming amines(FFAs) are increasingly being used as an alternative toconventional treatment programs for steam generators.Successful applications have been reported for bothplants which are continuously operated [1–7] and plantsunder wet or dry lay-up [5,8,9]. The FFA molecule, oftenalso referred to as polyamine or as fatty amine, adsorbsonto metal/metal oxide surfaces to form a hydrophobicfilm or barrier, which prevents corrosion by stopping waterand other corrosive agents from contacting the metal/metal oxide surface. Furthermore, the thin film fosters theformation of a smooth and compact iron oxide layer [10],which also plays an important role in preventing corrosion.

Once formed, the protective film remains intact in bothwet and dry conditions, even after dosing has stopped.This offers significant potential benefits for the preser -vation of both drained and (partially) filled plants duringshutdown, especially for plants under a cycling mode ofoperation.

The technology of FFAs is now included in internationallyaccepted guidelines: The International Association for theProperties of Water and Steam (IAPWS) has published aTechnical Guidance Document on the three main FFA molecules that have been the subject of intensiveresearch and where significant application experience isavailable [11], which includes oleylpropylenediamine.

Uniper UK's Connah's Quay combined cycle gas turbine(CCGT) power station has successfully trialled the use offilm forming technology based on oleylpropylenediamine(OLDA) from Kurita (Cetamine®) for water-steam cyclepreservation [12]. Over a three-year evaluation period, acomprehensive monitoring and site assessment pro-gramme was carried out. This paper reports on the experi-ences and results obtained.

During inspections at Connah's Quay power plant, theinternal surfaces of the heat recovery steam generator(HRSG) drums and low-pressure steam turbines were

Auth

or's

Cop

y

137


PowerPlant Chemistry 2018, 20(3)

PPCHEM

investigated in situ for the presence of OLDA with a newlydeveloped method [13]. Additionally, boiler tube sampleswere taken from the high-pressure evaporator andreheater stages from two different units of the power plantfor destructive examination and laboratory analysis for thepresence of OLDA.

Connah's Quay Power Plant

Connah's Quay Power Station (Figure 1) consists of four355 MW single-shaft combined cycle units (Units 1 to 4).The HRSGs are vertical gas path drum-type boilers withthree pressure stages (0.6, 3.6 and 12 MPa) and reheat.The final steam temperature is 540 °C. The low-pressuresuperheater temperature is ca. 270 °C. Make-up water isprepared by ion exchange and thermally and mechanicallydegassed in two steps in the deaerator. The station has awet recirculating hybrid cooling system. Figure 2 shows aschematic of the water-steam cycle.

The cycle chemistry is based on ammonia dosing to thefeedwater to pH 9.4–9.6 and sodium hydroxide dosing tothe drums to achieve a pH between 9.2 and 9.4 in the

high-pressure (HP) drum and between 9.5 and 9.8 in theintermediate-pressure (IP) and low-pressure (LP) drums.

The station operating regime varies considerably, withbetween one and four units running on a daily start-up andshutdown basis. FFA technology was identified as a potential flexible preservation option for the plant due to difficulties establishing conventional preservation methods.

Starting in December 2013, Cetamine V219 was dosedinto the Unit 4 feedwater with reduced ammonia dosageand, starting in August 2015, Cetamine G850 was dosedinto the Unit 1 feedwater in addition to ammonia.

Both Cetamine products contain the same FFA molecule(OLDA). Cetamine G850 contains only OLDA, whereasCetamine V219 additionally contains cyclohexylamine.After dosing was started, the targeted residual FFA con-centration in the return condensate could be measured inUnit 4 after 420 hours of operation and in Unit 1 after 380hours of operation. Residual FFA measurement was donephotometrically with the bengalrose method [14].

Figure 1:

The Uniper CCGT power plant in Connah's Quay, United Kingdom.

Auth

or's

Cop

y

138 PowerPlant Chemistry 2018, 20(3)

PPCHEM

RESULTS

General Water Chemistry

The changeover from ammonia/NaOH treatment did notshow a significant influence on pH and direct conductivity.

Steam Purity

Conductivity after cation exchange (CACE) as well asdegassed CACE (DCACE) in Unit 4 treated with OLDA andcyclohexylamine did not meet the quality requirement ofsteam purity to the steam turbines (Figure 3), whereas in

Unit 1 (treated only with OLDA), the steam DCACE wasgenerally below the required 0.2 µS · cm–1 limit (Figure 4).However, CACE and DCACE were slightly increased incomparison to the previous treatment. In Figures 3 and 4,the cycling operation mode is reflected by intense sharpspikes in the conductivity readings at unit start-ups.

The formation of acetate and formate was determined byion chromatography. In Unit 4 dosed with OLDA andcyclohexylamine, the cause of the increased CACE wasfound to be carbon dioxide and also acetate and formate.The presence of acetate and formate was also reflected in

CO PH

DA EV

LP EV

IP EV

IP/LP EC 1

IP EC 2

SH

RH

NaOH

LP drum

NaOH

IP drum

HP IP LPG

GGas turbine

NaOH

HP drum

HP EC 3

HP EV

SH

SH

HP EC 1

HP EC 2

Exhaust

Degasser

Feedwater tank

Ammonia

Cetamine®

V219/-G850

Condenser

Steam turbines

Figure 2:

Flow scheme of the water-steam cycle of the Connah's Quay power plant. The areas of different pressure are marked by colour.

DA deaeratorEC economiserPH preheaterEV evaporatorSH superheaterRH reheaterG generator


Auth

or's

Cop

y

139PowerPlant Chemistry 2018, 20(3)

PPCHEM

the DCACE measurement. This result is in accordancewith other studies [15,4]. In contrast, the small elevation inCACE in the Unit 1 steam was almost all due to carbondioxide. Figure 5 shows the average concentrations ofacetate and formate for both units. The increased CACE inUnit 4 apparently results mainly from decomposition of thecyclohexylamine. This finding is confirmed by thermolysisstudies under superheater conditions [16]. Figure 6compares the individual contributions to the CACE in bothunits. In contrast to Unit 4, the contribution of low molec -ular acids is very low in Unit 1. There, the steam purity ismaintained within the quality requirements for turbines.

Plant Inspections

During the trial period, plant inspections were carried outand various water-steam cycle surfaces tested for thepresence of OLDA. Besides visual inspection and metal-lurgical studies, three methods of analysis were applied todetermine OLDA on the system surfaces: the droplet test(test for hydrophobicity), the Kurita wipe test and alsophotoelectron spectroscopy (XPS). The droplet test is asimple and non-specific method to illustrate the wettabilityof a surface. The wipe test removes the FFA from the surface by wiping it with a solvent-soaked filter paper. It is

then transferred from the filter paper into an aqueous solu-tion, and its presence in this solution is determined by thebengalrose photometric method. A visible pink colour or asignificant absorbance from the bengalrose method is aclear proof of OLDA on the surface. The test itself andexamples of its use in power plants are described in [17].

XPS provides the elemental composition of the upper surface layer as well as information on the bonding stateof the elements. The information depth is ca. 10 nm. Incontrast to the two other methods (droplet and wipetests), XPS is generally destructive and cannot be carriedout in situ. These methods are described in detail in [13].In the following, the findings for selected parts of thewater-steam cycle will be discussed.

Drums All drums were very clean and completely freefrom organic deposits, such as gunk-balls. No active corrosion was observed. Loose iron deposits were signifi-cantly reduced; this was more pronounced in Unit 4,which can be attributed to the longer period of treatmentwith OLDA (Unit 4: 12 months; Unit 1: 3 months) at thetime of this inspection. Figure 7 shows the appearance ofthe HP drum of Unit 4 and the LP drum of Unit 1.

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Conductivity

after

Cation

Exchange

[µS

cm

]·

–1

10/01/13 01/09/14 04/19/14 07/28/14 11/05/14 02/13/15 05/24/15 09/01/15 12/10/15

Date [m/d/y]

Start of Cetamine V219dosing

®

Degassed CACE CACE

Figure 3:

Conductivity after cation exchange (CACE) and degassed CACE (DCACE) in the reheat steam of Unit 4 treated with Cetamine V219(OLDA and cyclohexylamine). The spikes mark unit start-ups.


Auth

or's

Cop

y


PPCHEM

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Conductivity

after

Cation

Exchange

[µS

cm

]·

–1

07/15/15 07/25/15 08/04/15 08/14/15 08/24/15 09/03/15 09/13/15

Date [m/d/y]

Start of Cetamine G850dosing

®

Figure 4:

CACE in the superheated steam of Unit 1 treated with Cetamine G850 (OLDA). The spikes mark unit start-ups.

Concentr

ation

[µg

L]

·–

1

25

20

15

10

5

0

G850 – Average

V219 – Average

Acetate Formate Acetate Formate Acetate Formate

HP Steam LP Steam IP Steam

Figure 5:

Average acetate and formate concentrations measured by ionchromatography in steam samples from Unit 4 (Cetamine V219)and Unit 1 (Cetamine G850).

0.6

0.5

0.4

0.3

0.2

0.1

0G850C

onductivity

after

Cation

Exchange

[µS

cm

]·

–1

V219

Unit 1 Unit 4

CO2 Acetate Formate

Ionisation of pure water

Figure 6:

Average contributions to HP/IP steam CACE for Unit 4(Cetamine V219) and Unit 1 (Cetamine G850).


Auth

or's

Cop

y


PPCHEM

HP Evaporators Tube samples were taken from theUnit 4 HP evaporator for metallurgical analysis. The tube sample taken in 2015 after 2 years of treatment with OLDAshowed only minor loose deposits. No active corrosionwas seen. In comparison, the internal surfaces of a Unit 4HP evaporator tube sample taken in 2012 beforeCetamine dosing was started exhibited an outer layer ofporous magnetite of ca. 100 µm thickness (Figure 8). Thiscomparison showed that loose iron oxide had been grad-ually removed by the FFA. However, it did not remove theunderlying dense protective magnetite layer.

The surfaces of the tube samples were further studied byXPS. Nitrogen bonded to aliphatic organic carbon couldbe detected on all surfaces exposed to OLDA-basedtreatments, for both Unit 4 (Cetamine V219) and Unit 1

(Cetamine G850) in a concentration between 0.4 and 2.3atom %, indicating the presence of OLDA on the tube surfaces. The tubes of Unit 4 showed a higher nitrogenconcentration than Unit 1, again reflecting the longer treatment period with OLDA. Furthermore, a tube fromUnit 4 from 2012 was analysed which had never beenexposed to an OLDA-based treatment and no nitrogenwas detected.

Reheater Tube samples were taken from both units, anda typical internal appearance was found with no notice-able change following OLDA treatment (Figure 9). XPSdetected nitrogen bonded to aliphatic carbon between 1.2and 1.8 atom %, a strong indication of film formation alsounder dry steam conditions.

Figure 7:

Unit 4 HP drum after 12 months of treatment (left) and Unit 1 LP drum after 3 months of treatment (right) with film forming amines (OLDA).

Figure 8:

Removal of loose iron oxide from Unit 4 HP evaporator waterside surfaces – before (left) and after (right) 2 years of treatment with FFAs.


Auth

or's

Cop

y


PPCHEM

LP Turbine Figure 10 shows pictures from the final stage(Stage 5) of the LP turbine of both units. Surfaces werevery clean and showed clear hydrophobicity. No corrosionwas observed. During a planned shutdown of Unit 1, allstages of the turbines could be assessed. All surfaceswere clean and free from corrosion. Stages 1–3 had lightmagnetite deposits. Hydrophobicity was detected onStages 4 and 5 only.

During both inspections, a thorough evaluation of theaccessible turbine stages using the Kurita wipe test was

carried out. OLDA could clearly be measured on the LP turbine surfaces of both units. It was detected on allfive stages of the Unit 1 LP turbine (only Stage 5 of Unit 4could be accessed). Table 1 shows selected absorb ancereadings corrected for the Blank. For comparison, theabsorbance of the front side of a turbine blade that hadnot been exposed to an OLDA treatment is also shown.

Hydrophobicity is apparently not an unambiguous indica-tion of the presence of OLDA.

Figure 9:

Reheater tubes from Unit 4 (left) and Unit 1 (right) after treatment with OLDA. No noticeable differences following the change oftreatment.

Figure 10:

Appearance of Stage 5 (final stage) of the LP turbines of Unit 4 (left) and Unit 1 (right) after 12 and 3 months, respectively, of treatmentwith FFAs.


Auth

or's

Cop

y


PPCHEM

CHANGING THE TREATMENT CONCEPT TOOLDA-BASED CHEMISTRY

The results of the trials with OLDA-based treatment programmes showed an excellent preservation of theinspected plants for both units. Management and controlof preservation with OLDA-based chemistry is simple. Thetreatment concept using Cetamine G850 containing onlyOLDA has the benefit of keeping the quality requirementsof steam purity.

Due to the overall positive findings, it was decided toadopt the supplementary treatment with Cetamine G850in addition to conventional ammonia and NaOH condi -tioning for all four units at the Connah's Quay PowerStation as of March 2016. The positive results have beenconfirmed by several plant inspections. The cleaningeffect of OLDA observed in the HP evaporator of Unit 4has also been seen in a second unit. Since 2017,Cetamine G850 has also been dosed into the auxiliaryboilers (five Benson-type boilers with an overall 40 t perhour steam capacity), which are operated mainly duringstart-up and shutdown of the units.

CONCLUSIONS

The Uniper power station at Connah's Quay evaluatedFFAs as a new treatment concept for meeting the preser-vation challenges of today's energy market, i.e. frequent

start/stops of units, with unpredictable shutdown periods,while at the same time the plants have to remain availableand may be required to run at short notice. Two productswere applied: Cetamine V219, a combination of OLDA andcyclohexylamine, and Cetamine G850, containing onlyOLDA. The key findings can be summarised as follows:

• OLDA could be determined on both water and steamtouched surfaces, including HP evaporators, reheatersand LP steam turbine cylinders.

• There was an evident internal cleaning effect in twounits in the HP evaporator: loose iron oxides wereremoved, but not the magnetite layer.

• The reliability and maintenance effort of on-line chemi-cal monitoring sensors were not affected by the filmforming amine.

• Alkalising amines led to increased CACE caused byorganic acids and carbon dioxide; treatment with thenew Cetamine G850 provides steam in accordancewith steam quality requirements.

• Components throughout the water-steam cycle wereprotected, including areas that could not be preservedby previous nitrogen capping or dehumidified air circu-lation.

• The preservation with film forming amine requires mini-mal manpower compared to preservation with nitrogencapping or dehumidification.

• There was no impact on unit availability or start-uptimes.

• The concept of FFA dosage for preservation andammonia and sodium hydroxide for pH control has nowbeen applied successfully for more than two years in allfour units at Connah's Quay.

REFERENCES

[1] Allard, B., Chakraborti, S., Svensk Papperstidning1983, 86(18), R 186.

[2] Hater, W., Rudschützky, N., Olivet, D., PowerPlantChemistry 2009, 11(2), 90.

[3] Van Lier, R., Gerards, M., Savelkoul, J., VGBPowerTech 2012, 92(8), 84.

[4] Kolander, B., de Bache, A., Hater, W., VGBPowerTech 2012, 92(8), 69.

[5] Hater, W., Digiaro, C., Frayne, C., Proc., InternationalWater Conference, 2012 (San Antonio, TX, U.S.A.).Engineers' Society of Western Pennsylvania,Pittsburgh, PA, U.S.A., Paper IWC-12-20.

[6] Hoock, B., Hater, W., de Bache, A., PowerPlantChemistry 2015, 17(5), 283.

Sample Absorbance

Untreated blade 0.05

Unit 4, Stage 5

Front side 0.25

Trailing edge 0.21

Disk and roots 0.28

Unit 1

Stage 5

Trailing surface 1.16

Inner front 0.33

Stage 3

Front face 0.29

Stage 1

Trailing face 0.23

Table 1:

Presence of OLDA as determined by the Kurita wipe test onturbine surfaces treated with OLDA. For comparison, the valueof an untreated blade is shown.


Auth

or's

Cop

y


PPCHEM

[7] Sylwestrzak, E., Moszczynski, W., Hater, W.,Dembowski, T., de Bache, A., VGB PowerTech 2016,96(8), 69.

[8] Hater, W., de Bache, A., Petrick, T., PowerPlantChemistry 2014, 16(5), 284.

[9] Wagner, R., Czempik, E., VGB PowerTech 2014,94(3), 48.

[10] Topp, H., Hater, W., de Bache, A., zum Kolk, C.,PowerPlant Chemistry 2012, 14(1), 38.

[11] Technical Guidance Document: Application of FilmForming Amines in Fossil, Combined Cycle, andBiomass Power Plants, 2016. International Associa -tion for the Properties of Water and Steam, IAPWSTGD8-16, available from http://www.iapws.org.

[12] Smith, B., McCann, P., Hater, W., de Bache, A.,Proc., VGB Conference "Chemistry in Power Plants",2016 (Karlsruhe, Germany). VGB PowerTech, Essen,Germany, Paper #V07.

[13] Smith, B., McCann, P., Mori, S., Uchida, K., Hater,W., Jasper, J., PowerPlant Chemistry 2017, 19(3),129.

[14] Stiller, K., Wittig, T., Urschey, M., PowerPlantChemistry 2011, 13(10), 602.

[15] Soellner, A., Glueck, W., Hoellger, K., Hater, W., deBache, A., VGB PowerTech 2013, 93(3), 61.

[16] Moed, D. H., Verliefde, A. R. D., Rietveld, L. C.,Industrial and Engineering Chemistry Research 2015, 54(10), 2606.

[17] Hater, W., Jasper, J., Disci-Zayed, D., Paper pre-sented at the 2nd International Conference on FilmForming Substances, 2018 (Prague, CzechRepublic). International Association for theProperties of Water and Steam.

THE AUTHORS

Wolfgang Hater (Ph.D., Physical Chemistry, WestphalianWilhelms-University, Münster, Germany) started his professional career in 1989 at Henkel, where he workedfor the industrial cleaner business. From 1993 until 2015he worked in different technical positions in the watertreatment divisions of Henkel and BK Giulini. Currently heis the technical director at Kurita Europe. He is the co-chairman of the working group Corrosion and ScaleInhibition of the European Federation of Corrosion and amember of the Power Cycle Chemistry working group ofthe International Association for the Properties of Waterand Steam (IAPWS).

Bill Smith, station chemist at Uniper's Connah's QuayPower Station, commenced working in electricity genera-tion in the UK at Peterhead Power Station in 1984, followed by 10 years at a nuclear power plant at Heysham2 Power Station. He has been a site chemist at Connah'sQuay since 1997.

Paul McCann (M.S., Chemistry, University of Nottingham,UK) is a specialist in power plant water-steam cycle chem-istry, corrosion, and water treatment at the UniperTechnologies Ltd. global consulting unit in the UK. He hashad 18 years of experience in the power industry sincejoining in 1999. Paul is vice-chair of the Power CycleChemistry working group of the International Associationfor the Properties of Water and Steam (IAPWS). He wasalso chair of the British and Irish Association for theProperties of Water and Steam (BIAPWS) from 2012 to2016.

André de Bache started his career at the Max PlanckInstitute for Bio-Inorganic Chemistry in Mülheim. In 1998he joined Henkel, where he worked for the department ofhygiene and microbiology. In 2004 he started working forBYK-Chemie in the application technology division ofadditives for plastics. In 2006 he joined Henkel WaterTreatment, and started working in 2008 for ICL WaterSolutions in product development for water conditioning,specializing in boiler water treatment. In 2012 he becamethe technical manager for boiler water additives, includingtraditional treatment products as well as products basedon film forming amines. In 2014 he became the productmanager for boiler water additives, filling this positionsince February 2015 for Kurita.

CONTACT

Wolfgang HaterKurita Europe GmbHNiederheider Strasse 2240589 DüsseldorfGermany

E-mail: [email protected]


Auth

or's

Cop

y

Documents

Experience with the Application of a Film Forming Amine in