Abstracts of publications in ppc whilst affiliated with sask power

Abstracts of Power Plant Chemistry Journal Publications whilst affiliated with
SaskPower
1. Chloride Contamination of the Water/Steam Cycle in Power Plants: Part VI. Confirmation
of Chlorinated Vapor Ingress Hypothesis by Regression Model Prediction of Boiler
Chloride to Sodium Ratios
Emmanuel K. Quagraine
This paper builds on earlier hypotheses that chlorinated compounds with significant vapor pressures
can ingress in gaseous/vapor forms into the condenser shell through weak seals and/or porous de-
alloyed brass tubesheet at tube-to-tubesheet joints. The issue was addressed by tubesheet hole
repairs with titanium epoxy and plastic epoxy application on all tubesheet faces.
The paper consists of two parts: 1) a cursory review of the literature on oxidative degradation of
polymers and how it can initiate leak paths for gas, vapor, and liquid permeation; and 2) derivations
and validations of predictive models to account for variations in boiler chloride to sodium ratios
(BCSRs) at various stages of operation after the epoxy resin repairs and condenser re-tubing. The
models (developed using multiple regression analysis) explained the variations well and confirmed
the hypotheses of chlorinated compound vapor ingress alongside water seepage into the condenser
shell from the cooling water (CW).
Earlier (the first 1½ years) in operation, vapor diffusion flux of chloramines, being favored by
temperature increase, was implicated as the dominant process of chlorine contaminant transfer from
the CW into the water/steam cycle, resulting in higher BCSRs. However, this mode of transport was
sporadic in these early stages. At later stages of operation, after an episode that seemed to have
caused damage to the titanium epoxy and tube-to-tubesheet joints, the chloride cycling became
more persistent. The derived model at this stage however showed (by p-statistics) a weak influence
of temperature. It also suggested: a) a blend of both diffusive and convective flows of chloramines as
transfer processes promoting higher BCSRs, and b) convective flux of liquid (aqueous CW)
contributing relatively higher sodium (than chloride), thereby lowering BCSRs. Through all stages,
CW free chlorine was found as the main influencing factor on
the convective flux of aqueous CW into the water/steam cycle.
PowerPlant Chemistry 2018, 20(2), 94–112
2. Chloride Contamination of the Water/Steam Cycle in Power Plants: Part V. Evidence for
Chlorinated Compound Vapor Ingress Even after Condenser Re -tubing and Tubesheet
Coating
This paper builds on earlier hypotheses that at the power plant under discussion chlorinated
compounds with significant vapor pressures can ingress in gaseous form into the condenser
shell through weak seals and/or porous de-alloyed brass tubesheet at tube-to-tubesheet joints

and are converted into chloride in the water/steam circuit. Aqueous seepage from the cooling
water (CW) is also implicated, but is minor. Dezincification is the main corrosion mechanism.
The issue was addressed by tubesheet hole repairs with titanium epoxy and plastic epoxy
application on all tubesheet faces. Yet failures linked with chlorine species attacks became
obvious soon after such repairs, showing variations in the boiler chloride to sodium ratio. More
sustained chloride cycling in the boiler to levels before the condenser repairs was observed only
after an episode which led to spikes in the condensate extraction pump (CEP) dissolved oxygen
(DO), CEP sodium, CEP conductivity after cation exchange (CACE), and steam sodium, and to
increasing of the differential oxidation reduction potential at the CEP and deaerator outlets.
Merely ~ 4.3 % of the chloride ingress from the CW system was estimated to be due to water
leakage; the remainder was attributed to vapor ingress of chlorinated compounds. Inspection of
the condenser waterboxes and the shell confirmed deterioration of epoxy cladding and tube-to-
tubesheet joints.
The current paper provides further evidence from the period in which breaches may have
occurred to the epoxy coating to support the concept that it is gaseous chlorine compounds and
not necessarily water from the recirculating CW which is responsible for the chloride
contamination of the water/steam cycle.
3. Insights and Lessons Learnt from a Scaling Event in a Cooling Tower Part II: Results and
Discussion on the Efficacies of Scale Predictive Indices, Scale Inhibitor(s), and On-Line
Cleaning Method(s)
This is the second half of a two-part article on a scaling incident that occurred at the Shand
Power Station, SaskPower. The paper describes a simple scale predictive index based on the
ratios of conductivity to calcium and magnesium concentrations for the early detection of
supersaturation and a high tendency towards scale deposition on heat exchanger surfaces
within recirculating cooling waters treated with scale inhibitors. With this predictive index, the
effectiveness of the scale inhibitor is evaluated based on the dosage concentrations vis -à-vis
the water chemistry during the scaling incident. Using empirical data, the dependability and
limitations of currently reported Ca2+ and SO42– ionic product guidelines in preventing calcium
sulfate scale deposition are also assessed. A distinction is made between the operational
adverse impacts of CaCO3 and CaSO4 scale deposition and their remedies. Details of on-line
acid cleans to restore the generation unit back to normal load are also described. The paper
concludes with remarks listing various lessons learnt from the scaling episode.
4. Insights and Lessons Learnt from a Scaling Event in a Cooling Tower Part I: Statement of
the Problem and Introduction to the Methodology of the Investigation

This is the first half of a two-part article on a scaling incident that occurred at the Shand Power
Station, SaskPower. The event exemplifies scaling as a costly operational problem associated
with the reuse of secondary treated municipal effluent when logistical challenges compel
operations outside designed limits. The plant, which was commissioned in 1992 and operates
on a zero liquid discharge program, has since 1994 been using treated sewage effluent as a
significant but variable portion of its cooling tower make-up water. As far as scaling is
concerned, apart from the early adjustment periods, the operation had been largely successful,
especially in the previous twelve years. Over the summer of 2014, however, due to restricted
outlets to manage the blending of the treated sewage effluent with fresh surface water, the plant
by its contractual obligation had to take untypically disproportionate amounts of the treated
effluent whilst also faced with a series of cooling water treatment equipment breakdowns. This
forced cooling tower operations to the water chemistry fringes, where the scaling potential was
high; ultimately, fouling of the condenser occurred, resulting in significant electricity generation
unit derates. The paper describes the event, the operating conditions, and an assessment of
the chemical treatment effectiveness, as well as the mitigation efforts made, including an on-line
acid clean to restore the generation unit back to normal load. Several lessons to be learnt from
the event are outlined.
5. BAC & GAC in Tandem for Removing Organics in Boiler Makeup Water: Performance
Evaluation from a ZLD Facility
Emmanuel K. Quagraine, Shawn Hood, Trever McNabb, Taneal Weiss, and Brenna
Janzen
The results of a case study evaluating organic removal options for a zero liquid discharge
power plant have been presented previously [1,2]. At this site, a granular activated carbon
(GAC) filter was best suited and it was later shown that the mechanism of organic removal was
mainly via adsorption at the early stages of operation, but was dominated by biodegradation of
organics as the GAC bed(s) aged [3]. It was hence proposed that by operating an aged and
biologically active carbon (BAC) bed (i.e. BAC filter) in series with a freshly replaced GAC filter
bed, an advantage can be gained for organic removal via biological degradation with the
upstream bed and adsorption by the downstream bed. And with such a process, it is possible to
reduce excessive microbial growth on the downstream bed, to extend the life of the
downstream bed to enable organic removal principally by adsorption, and to minimize carryover
of organic and biofouling potential to downstream demineralizing beds. The current paper
evaluates the performance of a BAC filter (aged ~4 years) in series with a freshly replaced
downstream bed (i.e. a BAC-GAC process) for organic removal from distillate from a brine
concentrator with a tendency towards biofouling in a boiler make-up treatment train. Changes in
the concentration of various physico-chemical and biological parameters (including total organic
carbon (TOC), pH, conductivity, turbidity, dissolved oxygen (DO), total inorganic carbon (TIC),
silica, and heterotrophic plate counts) across each of the two beds were monitored. An overall
average of 81 % TOC removal was observed across the two beds in series: 43.7 % by the BAC
bed and an additional 37.2 % by the GAC bed (i.e. 66.2 % removal from upstream bed
effluent). Correlation studies during the 8th and 9th weeks of operation showed a consistent
increase in TIC, and a decrease in DO and pH concentrations across each of the filters, and
each correlated significantly with TOC (or % TOC removed). ~25–29 % and ~3–7 % of TOC
removed by the BAC and GAC beds, respectively, was related to changes in all three
parameters. These portions of removed TOC were therefore attributed to organic bio-

mineralization into CO2. Changes in concentrations of silica and other inorganic species
concentrations across the beds were more complex: consistent increases for most parameters
across the GAC bed occurred in the early stages of operation, but more erratic changes (i.e.
removal and/or releases) occurred on the BAC bed and on the GAC bed later in operation
when bioactivity was a factor. Magnesium and calcium, however, were exceptional: these ions
were generally removed by the BAC filter throughout the study period and by the GAC bed from
the 18th day of operation. Isolated cases of silica removal seem to relate to influent TOC:
particularly with the downstream bed, when bioactivity was a factor, low influent TOC
concentration seemed to favour silica removal, but more work is required to confirm this.
PowerPlant Chemistry 2013, 15 (5), 366-389
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6. Chloride Contamination of the Water/Steam Cycle in Power Plants Part IV: Association
with Tubesheet Dealloying as Evident during a Condenser Re-tubing
PPChem (Power Plant Chemistry) 2013_15(1), 41-61
This paper is a continuation of a series of publications on investigations performed at the
Shand Power Station (SaskPower) to determine a hitherto unfamiliar source(s) of chloride
contamination to the water/steam circuit. The first showed that current popularly known
causative factors were not individually or cumulatively responsible root causes of the
chloride ingress. The second provided evidence from overhaul inspections and sample test
results that the chloride ingress emanates from a cooling water source, but through two
different (gaseous and water-borne) pathways, each of which is distinctly different from the
common condenser tube water leaks. The gaseous ingress pathway was identified as the
likely main source of the contamination. In the third paper, computational analysis and plant
operational data were used in support of this idea. The working hypothesis was that
chlorinated compounds with significant vapor pressures (e.g. free chlorine species HOCl
and Cl2, chloramines NH2Cl, NHCl2 and NCl3, trihalomethanes (THMs), haloacetic acids,
HCl, etc.) ingress in gaseous forms into the condenser hotwell through weak seals of
tubeto-tubesheet joints. Apart from some THMs (i.e. CHCl3 and CBrCl2), which are likely to
be lost significantly through air ejection and deaeration processes, NH2Cl, HOCl and NHCl2
were noted to be potential significant contributors of chlorides to the water/steam cycle from
the re-circulating cooling water. Dezincification was implicated as the corrosion mechanism
occurring from the attack of these oxidizing chlorinated compounds on weak naval brass
tubeto-tubesheet joints, thus creating a pathway for the vapor of these relatively volatile
inorganic solutions to enter the shell side of the condenser. This fourth paper first provides a
brief literature background and follows up with pictorial evidence of the dezincification
process and results of more detailed laboratory analyses of samples collected during the
condenser tube removal and re-tubing periods in support of the above hypotheses.
PowerPlant Chemistry 2013, 15 (1)
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7. Chloride Contamination of the Water/Steam Cycle in Power Plants
Part III. Computational Analysis and Plant Operational Evidence in Support of Cooling
Water Source Gaseous Ingress Hypothesis
Emmanuel K. Quagraine and Jonathan P. Ruffini

PPChem (Power Plant Chemistry) 2012, 14(4), 214-231
This is the third and final paper in the series of publications on investigations performed at
the Shand Power Sation of SaskPower to determine a hitherto unfamiliar source(s) of
chloride contamination to the water/steam circuit. The first paper showed that current
popularly known causative factors were not individually or cumulatively responsible as root
causes of the chloride ingress. The second paper provided evidence that the chloride
ingress emanates from the cooling water, but through two different (gaseous and water-
borne) pathways, each of which is distinctly different from the common condenser water
leaks. The gaseous ingress pathway was identified as the likely main source of the
contamination. In this final paper, computational analysis and plant operational data are
used in support of this idea. The working hypothesis is that chlorinated compounds with
significant vapour pressures (e.g. free chlorine species HOCl and Cl2, chloramines NH2Cl,
NHCl2 and NCl3, trihalomethanes (THMs), haloacetic acids, HCl, etc.) ingress in gaseous
forms into the condenser hotwell through weak seals of tube-to-tubesheet joints. Henry's
constants and other equilibrium expressions have been used to estimate gaseous ingress
from these species (expressed as chloride) at different pH values of the re-circulation water.
Under typical operation conditions in this plant, an estimated cumulative chloride
concentration of up to 4.5 µg · L–1 (ppb) in the boiler feedwater is possible. Although the
actual ingress experienced from these sources varies, it is estimated to be between 2 to
10 % of that from the expected cumulative sources. Under normal operating conditions, the
three expected most dominant contributors of chloride are CHCl3, followed by NH2Cl and
CBrCl2. Two other chlorinated species of modest but significant chloride contribution are
HOCl and NHCl2, and their contributions are expected to be relatively higher under low
cooling water pH excursion conditions.
PowerPlant Chemistry 2012, 14 (04
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8. Chloride Contamination of the Water/Steam Cycle in Power Plants
Part II. Evidence for Two Previously Unknown Routes from Condenser Cooling Sources
PPChem (Power Plant Chemistry) 2012, 14(3), 174-185
This is the second paper in a series of publications on findings from investigations
performed at the Shand Power Station of SaskPower to identify the root cause(s) of chloride
contamination of the water/steam cycle experienced in the plant, which appeared quite
elusive initially. In the first paper, we showed a case where the chloride ingress could not be
explained by the current literature reported routes of chloride ingress. In this current paper,
photographic evidence and sample test analyses – both qualitative and quantitative by
methods such as N, N-diethyl-p-phenylenediamine (DPD) reagent spectrometric
determination for residual chlorine, scanning electron microscopy–energy dispersive
spectroscopy, inductively coupled plasma mass spectrometry, and combustion ion
chromatography (AQF-IC) determination of anions – are presented to support a hypothesis
that chloride ingress was emanating from the re-circulating condenser cooling water, but by
a pathway(or pathways) completely different from the traditionally known condenser tube
water leaks. Evidence is provided that residual chlorine compounds and/or chlorides were
ingressing in both gaseous forms and aqueous forms into the condenser hotwell through
weak seals of tube-to-tubesheet joints. The latter route, via a water-borne pathway, was
shown to be distinctly different from that of the well-known condenser tube leaks by means
of condensate contamination; it appears to follow a mechanism based on solubility
differences to selectively contribute more chloride than sulphate from cooling water sources
into the hotwell water. It was however determined to be only a minor contributor. The former

route, however, was implicated as the dominant route. By this pathway, chlorinated species
of relatively high vapour pressures (some of which are strong oxidizing agents) would
ingress into the condensate portion of the condenser via tube-to-tubesheet joints.
Dezincification of the brass tubesheet was found to be likely to occur by this means, causing
deposition of ZnO at the point of contact on the condensate side of the condenser as
observed.
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9. Chloride Contamination of the Water/Steam Cycle in Power Plants Part I: Evidence from a
Case Which Could Not Be Explained in Terms of Currently Familiar Sources
PPChem (Power Plant Chemistry) 2012, 14(2), 98-111.
This is the first of a three-part publication series on the findings from investigations performed at
the Shand Power Station of SaskPower to determine a hitherto unfamiliar source(s) of chloride
contamination to the water/steam circuit. For this plant, which is usually on automatic grid control,
unit ramping is common and there is some reason to associate this with the initiation of the
chloride ingress. The present paper presents a systematic approach to examining the various
familiar sources currently known to plant operators, chemists and the like as potential culprits and
provides the bases for eliminating these as responsible agents in this case. Based on routine plant
operating data and purposeful intermittent grab sample analyses as well as numerical analysis of
chloride cycling in the boiler, these well-known potential causative factors, which include
condenser tube water leaks, make-up chloride, halo-organics from the water treatment plant, and
contaminated ammonia feed sources, could not be found to individually or cumulatively account
for the magnitude of chloride contamination observed in this plant. The extent of the chloride
cycling required too frequent blowdowns from the boiler, and a cost analysis of the implications
from such frequent blowdowns is also presented as one of the incentives that drove the search for
the root cause of such a level of contamination. There were some indications that surplus
condensate from the hotwell to the boiler make-up storage tanks was a significant chloride origin,
but this could not account for the level of contamination, and the source seems to be distinctly
different from the traditionally known condenser tube water leaks. Furthermore, there were some
indications that ammonia injection was associated with the chloride crises, although there was
ample evidence to eliminate this as the source. These associations formed the basis for further
investigations, the findings of which will be reported as Part II and Part III of this series.
PowerPlant Chemistry 2012, 14 (02)
10. Evaluation of Organics Removal Options: A Case Study from a Zero Liquid Discharge
Power Plant
Emmanuel K. Quagraine, Keith Dean Hill, and Fredrick Omorogbe
Although the role of organics in power plant cycle chemistry still appears to be controversial, their
adverse effects in the course of makeup water treatment are very familiar and include fouling of
ion exchange resins. This paper describes the organic/bio-fouling experience in a boiler makeup
water treatment train for a zero liquid discharge plant, which draws on treated sewage water and

surface water for cooling and utilizes the cooling tower blowdown to make distillate water from an
evaporator prior to final treatment with a mixed bed demineralizer. In a case study, which is the
focus of this paper, the performance of the pilot plants of two recommended organic removal
techniques (i.e. reverse osmosis and organic trap resin) were compared to the existing activated
carbon bed for organic removal prior to the mixed beds. Parameters evaluated for these three
techniques (before and after each unit) include bacteria plate counts, organic carbons, inorganic
nutrients (e.g. NH3-N, [NO3– + NO2–]-N, P, Mn, and Fe), known parameters that could significantly
impact on the performance of the mixed beds (i.e. SiO2, Cl–, SO42–, Na+), and various others like
pH, conductivity, turbidity, HCO3– etc. The effects of oxidizing (i.e. bleach) and non-oxidizing
(glutaraldehyde) biocides on the performance of the activated carbon filter were also evaluated.

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