Scale buildup on water-side heat transfer surfaces poses a potential operating challenge for steam-assisted gravity drainage (SAGD) boilers used in the production of bitumen since produced water, which has a high dissolved solid content, is recycled. Scale from deposition of dissolved solids on boiler tubes acts as a thermal insulating layer, decreasing heat transfer and lowering boiler efficiency. Understanding scale deposit composition on heat transfer surfaces is beneficial in the determination of adequate boiler maintenance practices and operating parameters. This research determined the effect of feedwater pH (7.5, 9.0, and 10.0) on scale composition resulting from deposition of dissolved solids under commercially relevant boiler operating conditions at 8.96 MPa (1300 psig) and 37.86 kW/m2 (12,000 Btu/h ft2). Scale deposits were analytically investigated using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS), powder X-ray diffraction (XRD), and Raman spectroscopy. At feedwater pH values of 7.5 and 9.0, anhydrite (CaSO4), xonotlite (Ca6Si6O17(OH)2), and pectolite (NaCa2Si3O8(OH)) were detected. At the pH of 10.0, xonotlite and pectolite were identified in the absence of anhydrite. Furthermore, the magnesium silicate phase, serpentine (Mg3Si2O5(OH)4), was also postulated to be present.

References

References
1.
Government of Alberta
,
2010
, “
Water Use
,” Government of Alberta, Edmonton, AB, Canada, accessed Aug. 10, 2010, http://www.oilsands.alberta.ca/water.html
2.
Goodman.
,
W. H.
,
Godfrey
,
M. R.
, and
Miller
,
T. M.
,
2010
, “
Scale and Deposit Formation in Steam Assisted Gravity Drainage (SAGD) Facilities
,”
71st International Water Conference
, San Antonio, TX, Oct. 24–28, p.
2
.
3.
Demadis
,
K. D.
,
2010
, “
Recent Developments in Controlling Silica and Magnesium Silicates in Industrial
,”
The Science and Technology of Industrial Water Treatment
, Vol.
3
,
IWA Publishing/CRC Press
,
Boca Raton, FL
, pp.
180
183
.
4.
Hauksson
,
T.
,
Pórhallsson
,
S.
,
Gunnlaugsson
,
E.
, and
Albertsson
,
A.
,
1995
, “
Control of Magnesium Silicate Scaling in District Heating Systems
,”
World Geothermal Congress
, Florence, Italy, May 18–31.
5.
Coto
,
B.
,
Martos
,
C.
,
Peña
,
J. L.
,
Rodríguez
,
R.
, and
Pastor
,
G.
,
2012
, “
Effects in the Solubility of CaCO3: Experimental Study and Model Description
,”
Fluid Phase Equilib.
,
324
, pp.
1
7
.
6.
Chermak
,
J. A.
, and
Rimstidt
,
J. D.
,
1989
, “
Estimating the Thermodynamic Properties (ΔGf° and ΔHf°) of Silicate Minerals at 298 K From the Sum of Polyhedral Contributions
,”
Am. Mineral.
,
74
(
9
), pp.
1023
1031
.
7.
Ehrlich
,
H. L.
,
Newman
,
D. K.
, and
Kappler
,
A.
,
2015
,
Ehrlich's Geomicrobiology
,
CRC Press
,
Boca Raton, FL
, p.
212
.
8.
Hamer
,
P.
,
Jackson
,
J.
, and
Thurston
,
E.
,
1961
,
Industrial Water Treatment Practice
,
Butterworths
,
London
, p.
117
.
9.
GE Power & Water
,
2007
, “
Chapter 12—Boiler Deposits: Occurrence and Control
,” GE Power & Water, Atlanta, GA, accessed Aug. 28, 2014, http://www.gewater.com/handbook/boiler_water_systems/ch_12_boilerdeposits.jsp
10.
Utilitiesman
,
1999
, “
Manual for Electric, Plumbing, Water and Other Utilities
,” Integrated Publishing, Port Richey, FL, accessed Sept. 28, 2015, http://constructionmanuals.tpub.com/14259/css/14259_244.htm
You do not currently have access to this content.