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Scale Formation (scale + formation)

Distribution by Scientific Domains
Chemistry23%

Selected Abstracts

A Study of Gypsum Scale Formation using Quartz Crystal Microbalance

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006
T. A. Hoang
The quartz crystal microbalance (QCM) has been used extensively as a mass sensor due to its extremely high sensitivity to small mass loadings. Conventional measurement of the amount of scale deposited on a surface is restricted by the sensitivity limit of analytical balances. Thefirst attempt to investigate the deposition of gypsum scale on a surface using a rotating electrochemical QCMsystem was carried out to investigate the eflects of many factors at the early stages of scale formation. Results indicated there was almost no induction time for this system, and the long induction time observed in the conventional system was due to the limited sensitivity of the analytical balance. A slow increase in scale amount was observed at the beginning of the scaling process as shown by the plot offrequency or mass change against time. After this period the curve rises steeply and becomes almost linear. The supersaturation level of the solutions and the rotating speed have significant effects on the gypsum scaling. A QCM flow-cell system has also been developed to investigate the scaling of gypsum on the pipe wall. This system is similar to a conventional pipe flow system except that its size is much smaller and the deposition of scales can be monitored with the QCM electrode throughout the scaling process. The mass change is plotted against time and results are compared for the rotating QCM system and the conventional system. It is noticed that the formation of gypsum on the QCM electrode is greatly dependent on both the supersaturation of the solution and the flow rate of the fluid passing through the flow cell. [source]

Effect of phosphonate additive on crystallization of gypsum in phosphoric and sulfuric acid medium

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2002
H. El-Shall
Abstract Understanding the mechanisms of growth and inhibition during crystallization of calcium sulfate is of primary importance for many industrial applications. For instance, inhibition of the crystallization process may be required to prevent scale formation in pipes, boilers, heat exchangers, reactors, reverse osmosis membrane surfaces, cooling water systems, secondary oil recovery utilizing water flooding techniques and desalination evaporators, etc. On the other hand, control growth and morphology of gypsum crystals is desired in achieving higher filtration rate and higher productivity of phosphoric acid from phosphate rocks. In this regard, this basic study is carried out to understand effect of Aminotris (methylenephosphonic acid (ATMP) on calcium sulfate dihydrate (gypsum) crystallization. The time elapsed between the achievement of supersaturation and the appearance of a solid phase (termed as induction time) is measured under different supersaturation ratios ranging from 1.018 to 1.979. The data are used to calculate the surface energy, critical nucleus size, and crystal growth rates of gypsum under different conditions. The results show that, the induction time decreases exponentially with increasing the supersaturation ratio. In addition, the surface energy decreases with ATMP compared to the baseline (without ATMP). Interestingly, with addition of the ATMP, the crystals mean and median diameters are found to decrease. The inhibition efficiency ranges from 16% to 59% depending on supersaturation ratio. [source]

A structure/function study of polyaminoamide dendrimers as silica scale growth inhibitors

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2005
Konstantinos D Demadis
Abstract Dendrimers have attracted immense attention during the last decade due to their interesting properties both from a basic and an applied research viewpoint. Encapsulation of metal nanoparticles for catalysis, drug delivery and light harvesting are only some applications of dendrimers that are breaking new ground. A novel application of dendrimer technology is described in the present paper that relates to industrial water treatment. Industrial water systems often suffer from undesirable inorganic deposits. These can form either in the bulk or on metallic surfaces, such as heat exchangers or pipelines. Silica (SiO2) scale formation and deposition is a major problem in high-silica-containing cooling waters. Scale prevention rather than removal is highly desired. In this paper, benchtop screening tests on various silica inhibition chemistries are reported, with emphasis on materials with a dendrimeric structure. Specifically, the inhibition properties of commercially available STARBURST® polyaminoamide (PAMAM) dendrimers generations 0.5, 1, 1.5, 2, and 2.5 are investigated in detail together with other commonly-used scale inhibitors. Experimental results show that inhibition efficiency largely depends on structural features of PAMAM dendrimers such as generation number and nature of the end groups. PAMAM dendrimers are effective inhibitors of silica scale growth at 40 ppm dosage levels. PAMAM dendrimers also act as silica nucleators, forming SiO2,PAMAM composites. This occurs because the SiO2 formed by incomplete inhibition interacts with cationic PAMAM-1 and -2. The general scope of silica formation and inhibition in industrial waters is also discussed. Copyright © 2005 Society of Chemical Industry [source]

Materials and Corrosion 6/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2010
Article first published online: 22 JUN 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof- Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 5/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 5 2010
Article first published online: 14 MAY 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof- Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 4/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2010
Article first published online: 12 APR 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 3/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2010
Article first published online: 18 MAR 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 2/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2010
Article first published online: 9 FEB 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 1/2010

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2010
Article first published online: 8 JAN 2010
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 12/2009

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2009
Article first published online: 17 DEC 200
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof- Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 11/2009

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2009
Article first published online: 24 NOV 200
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof- Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 10/2009

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2009
Article first published online: 19 OCT 200
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 9/2009

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2009
Article first published online: 10 SEP 200
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof-Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Materials and Corrosion 8/2009

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2009
Article first published online: 21 AUG 200
Cover: Surface-near zone of a creep rupture specimen of a centrifigally cast Fe-Ni-Cr alloy after exposure at 1050°C with strong oxidation in beginning creep cracks and with carbide free subsurface area due to chromium consumption by oxide scale formation. The specimen was prepared for metallographic investigation by coating with a thin ZnSe interference layer for colour contrast. More details about the microstructures of these materials are given in E. Berghof- Hasselbächer, P. Gawenda, M. Schorr, M. Schütze, J. J. Hoffmann, Atlas of Microstructures, MTI St. Louis 2008, ISBN 978-1-57698-046-0. [source]

Service conditions and their influence on oxide scale formation on metallic high temperature alloys for application in innovative combustion processes

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2006
G. Teneva-Kosseva
Abstract The present paper focuses on two aspects: the service conditions of a flame tube in a low-NOx recirculation burner (maximum temperature experienced by the material: 1000 °C) and the interrelationship between service conditions and both the structure and growth of the oxide scale. The flame tube is exposed to extreme thermal and atmospheric conditions during service. Due to the short burner operation time followed by a pause, rapid changes of the temperature and gaseous environment occur. Three Ni-based alloys (alloy 602 CA, alloy 603 XL and alloy 693) were investigated in cyclic oxidation tests under typical conditions for the combustion of fuel oil. Flame tube temperature measurements in both the axial and the tangential directions are presented together with results concerning the influence of the fuel quality, duration of the air ventilation after burner shut down and temperature on the thickness and composition of the oxide scale. [source]

A Study of Gypsum Scale Formation using Quartz Crystal Microbalance

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006
T. A. Hoang
The quartz crystal microbalance (QCM) has been used extensively as a mass sensor due to its extremely high sensitivity to small mass loadings. Conventional measurement of the amount of scale deposited on a surface is restricted by the sensitivity limit of analytical balances. Thefirst attempt to investigate the deposition of gypsum scale on a surface using a rotating electrochemical QCMsystem was carried out to investigate the eflects of many factors at the early stages of scale formation. Results indicated there was almost no induction time for this system, and the long induction time observed in the conventional system was due to the limited sensitivity of the analytical balance. A slow increase in scale amount was observed at the beginning of the scaling process as shown by the plot offrequency or mass change against time. After this period the curve rises steeply and becomes almost linear. The supersaturation level of the solutions and the rotating speed have significant effects on the gypsum scaling. A QCM flow-cell system has also been developed to investigate the scaling of gypsum on the pipe wall. This system is similar to a conventional pipe flow system except that its size is much smaller and the deposition of scales can be monitored with the QCM electrode throughout the scaling process. The mass change is plotted against time and results are compared for the rotating QCM system and the conventional system. It is noticed that the formation of gypsum on the QCM electrode is greatly dependent on both the supersaturation of the solution and the flow rate of the fluid passing through the flow cell. [source]

The Fouling Behaviour of Sodium Aluminosilicate Polytypes in High Ionic Strength Caustic Media Heat Exchangers

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006
J. Addai-Mensah
Sodium aluminosilicate (SAS) scale formation, simulating high ionic strength caustic media process heat exchanger fouling, has been investigated for a temperature range of 30,240°C. Findings from several studies performed with a variety of liquor, substrate-type and agitation conditions show that SAS polytypes; i.e. amorphous, zeolite A, sodalite and cancrinite phases, differing in thermodynamic stability and kinetic behaviour may deposit. The polytypes formed and subsequent transformations to more thermodynamically stable phases are strongly dependent on liquor composition, temperature and time. The scale deposition process is substrate- mediated heterogeneous nucleation and particle growth (precipitation foulin&, which may be accompanied by bulk liquor-nucleated solids adsorption (particulate fouling) at suficiently high supersaturations. Liquor seeding with stable SAS solid phases is found to be efective in mitigating fouling. The precipitation fouling behaviour is principally determined by the clystallo-chemical nature of the SAS polytype and the solution conditions. The substrate (mild steel, 316 stainless steel, nickel and tef2on) surface physico-chemical structure has a signlficant impact on the scale particle morphology and layer structure, particularly at high temperatures. [source]