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Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions
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Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions N.K. Amin a , M.H. Abdel-Aziz a,b,∗ , E-S.Z. El-Ashtoukhy a a
Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt Chemical and Materials Engineering Department, Faculty of Engineering, King Abdulaziz University, Rabigh 21911, Saudi Arabia
b
a b s t r a c t The present study aimed to investigate the corrosion behavior of a pipeline carrying dilute pulp fiber suspensions (0.1–0.3% consistency). To examine the role played by pulp fibers on the rate of diffusion controlled corrosion of metals an accelerated test which involved the diffusion controlled dissolution of copper in acidified dichromate was used under turbulent flow conditions. Different concentrations of pulp fibers at different solution velocities were studied. The rate of mass transfer controlled corrosion of copper was found to increase by increasing solution velocity and decrease by increasing pulp consistency. The data in the presence and absence of the pulp slurry were correlated by dimensionless equations. The importance of the present results in estimating the rate of corrosion in equipment used in the pulp and paper industry especially pipelines and heat exchangers were highlighted. The decrease in the rate of diffusion controlled corrosion in the presence of the pulp was explained in terms of the drag reducing ability of pulp slurry. © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Corrosion; Corrosion inhibition; Diffusion; Mass transfer; Pipe flow; Pulp and paper
1.
or :
Introduction
Corrosion of metals is a big problem in chemical, pulp and petroleum industry as it gives rise to enormous financial losses. The cost of corrosion for the pulp industry was only estimated at approximately $808.5 million per year as corrosion affects production as follows: (i) corrosion products polluting the paper, (ii) corrosion of rolls scarring the sheets of paper, (iii) corrosion of components may also result in fractures. Corrosion of metals takes place through the formation of a galvanic cell which consists of an anode and cathode, where the following reactions take place: Anode reaction : M → M++ + 2e (1)
Cathode reaction :
(1/2)O2 + H2 O + 2e → 2OH−
(pH 4–10) (2)
2H+ + 2e → H2
(pH < 4)
(3)
Each of the above reactions is a heterogeneous reaction which involves two steps namely, (i) a diffusion step where the reactant (O2 or H+ ) has to diffuse to the metal surface from solution bulk, (ii) charge transfer step (chemical step) where a chemical reaction takes place at a metal surface. The overall rate of corrosion is determined by the slowest step of anodic and cathodic reactions, it was found that in the pH range 4–10 the rate determining step is the diffusion of O2 from the solution bulk to the metal surface such as copper and steel which are the most widely used materials of construction in the industry. Under these conditions corrosion is described as diffusion controlled corrosion (Fontana, 1987; Zaki et al., 1997; Sedahmed et al., 2004; Cornet et al., 1980; Abdel-Aziz, 2013; Fouad et al., 2013). The aim of the present work is to shed some light on the diffusion controlled corrosion of pipelines used in the pulp and paper industry, where the flow of dilute water fiber
∗
Corresponding author at: Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt. Tel.: +20 3 5745962; fax: +20 3 59211853. E-mail address: [email protected] (M.H. Abdel-Aziz). Received 27 September 2013; Received in revised form 28 December 2013; Accepted 18 January 2014 0263-8762/$ – see front matter © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cherd.2014.01.023 Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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Nomenclature A a C C0 Cb Ci D d N k Q R t V ı ˛, ˇ Re Sc Sh
pipe inside surface area (cm2 ) constant concentration at time t (mol/cm3 ) initial concentration (mol/cm3 ) bulk concentration, (mol/cm3 ) concentration at the interface (mol/cm3 ) diffusion coefficient (cm2 /s) pipe inside diameter (cm) mole flux (mol/cm2 s) mass transfer coefficient (cm/s) solution volume (cm3 ) rate of corrosion (mm/year) time (s) solution velocity (cm/s) solution viscosity (g cm−1 s−1 ) solution density (g cm−3 ) diffusion layer thickness (cm) constants Reynolds number, Vd/ Schmidt number, /D Sherwood number, kd/D
suspensions (consistency < 1%) in a pipe line which is similar to the flow in a paper machine head-box, and the flow conditions there determine the quality of produced paper. Flow of dilute water-fiber suspensions over a backward facing step is present in many unit processes in paper production, especially in the wet end of paper machine, and is an important mixing element for fiber suspension flows, because it is very effective turbulence generator (Huhtanen and Karvinen, 2005). To this end, an accelerated test was used namely, the diffusion controlled dissolution of copper in acidified dichromate which simulates natural diffusion controlled corrosion of metals in the pH range 4–10. The system has been used widely to study diffusion controlled corrosion of metals under different hydrodynamic conditions (Cornet et al., 1980; Abdel-Aziz, 2013; Sedahmed et al., 1998; Abdel-Aziz et al., 2010; Madden and Nelson, 1964; Patil and Sharma, 1983). Pipes are used in the pulp and paper industry to transfer the slurry between different units and in fabricating heat exchangers used to handle pulp slurry. Accordingly study of the corrosion behavior of pipes carrying pulp slurry is important for estimating the rate of corrosion and hence the corrosion allowance needed in the design stage of these pipelines and heat exchangers. Studies of the flow behavior of pulp slurries (Newazkazi et al., 1999; Higgins and Wahern, 1982) have revealed that under turbulent flow conditions pulp slurries exhibit drag reducing properties, i.e. the pressure drop across the pipeline carrying pulp slurry is less than that carrying water. The decrease in friction between the turbulently flowing pulp suspension and the wall of the pipeline is explained by the ability of pulp fibers to damp the small scale high frequency energy dissipating eddies which exist in the hydrodynamic boundary layer on the pipe wall (Sedahmed, 2005; Cussler, 1988; Sellin et al., 1982; Hoyt, 1972; Little et al., 1975). Since small scale high frequency eddies enhance the rate of depolarizer (dissolved O2 or K2 Cr2 O7 ) diffusion to the wall of the pipeline, it is expected that the presence of paper pulp which damps these eddies would decrease the rate of depolarizer diffusion and the rate of pipeline corrosion. The main aim of the present work is
Fig. 1 – Apparatus. (1) Plexiglas tank, (2) liquid level, (3) plastic centrifugal pump, (4) control valves, (5) rotameter and (6) copper tube. to find out the extent to which the presence of pulp slurry inhibits the diffusion controlled corrosion. Although the use of drag reducing polymers as corrosion inhibitors has been studied (Sedahmed, 2005; Sedahmed et al., 1998; Zahran and Sedahmed, 1998; Zakin et al., 1998; Schmitt, 1996), no work has been reported in the literature on the inhibiting effect of pulp slurry on the rate of diffusion controlled corrosion despite its industrial importance for the pulp and paper industry.
2.
Experimental part
2.1.
Materials
Three different concentrations of acidified potassium dichromate solution were used namely; 0.003 M K2 Cr2 O7 + 0.5 M H2 SO4 , 0.003 M K2 Cr2 O7 + 1 M H2 SO4 , 0.003 M K2 Cr2 O7 + 1.5 M H2 SO4 . All solutions were prepared from AR chemicals and distilled water. The pulp slurry used in the present study was taken from Rakta s Pulp and Paper Company, located in Alexandria, Egypt. Rakta s Pulp and Paper Company produces writing and printing paper from soda pulping of rice straw, and hypochlorite bleaching of the produced pulp. The test metal section was a copper pipe of 2 cm inside diameter and 100 cm length. Based on previous studies (Abdel-Aziz et al., 2010; Madden and Nelson, 1964; Patil and Sharma, 1983) dissolution of copper in acidified dichromate is diffusion controlled.
2.2.
Experimental technique
Fig. 1 shows the experimental setup used in the present study. It consists of 15 L Plexiglas storage tank, a 0.25 hp plastic centrifugal pump, and a vertical copper pipe of 2 cm inside
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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diameter and 100 cm length. The acidified K2 Cr2 O7 solution was circulated through the system between the pipe and the storage tank by means of plastic pump. Eight liters of fresh acidified dichromate solution were used in each experiment. The solution flow rate was controlled by a bypass and was measured by a rotameter. For each concentration of acidified K2 Cr2 O7 solution three different pulp slurry consistencies (Pulp consistency = (weigh of pulp/(weight of pulp + weight of water)) × 100) were used namely; 0.1, 0.2, and 0.3% pulp consistency. The duration of each experiment was 30 min. The rate of copper dissolution in acidified dichromate solution was followed by withdrawing 5 cm3 samples at 3 min intervals for dichromate analysis. Dichromate was analyzed by using a UV spectrophotometer (Shimadzu Model: UV 1601) with diphenylcarbazide indicator at 540 nm (Vogel, 1985). Experiments were conducted at a temperature ranging from 22 to 25 ◦ C. The physical properties of solution needed for data correlation (solution density and viscosity) were measured by a density bottle and an Ostwald viscometer, respectively (Findlay and Kitchener, 1965). The diffusivity of dichromate was obtained from the literature (Madden and Nelson, 1964; Gregory and Riddiford, 1960).
3.
Results and discussion
The mass transfer coefficient of the diffusion controlled corrosion of copper pipe in acidified dichromate containing pulp slurry was obtained under different conditions from the dichromate concentration-time data. Fig. 2 shows that the data for the present batch recirculating reactor fit the equation (Pickett, 1977; Walsh, 1993): −Q
dC = kAC dt
(4)
which upon integration yields: ln
C0 kA = t C Q
Fig. 3 – Effect of solution velocity on mass transfer coefficient at different pulp consistency (0.0003 M K2 Cr2 O7 + 0.5 M H2 SO4 , temp = 22 ◦ C). Pulp consistency: × – 0% (blank), – 0.1%, – 0.2% and – 0.3%. volume of the solution in the tank. The mass transfer coefficient was calculated from the slope of ln(C0 /C) vs. t line (Fig. 2). The rate of dissolution of copper is expressed in terms of mass transfer coefficient, which was determined for different pulp consistencies at different solution velocities.
3.1. Effect of pulp consistency on rate of diffusion controlled corrosion of the pipe wall Fig. 3 shows the effect of solution velocity on the mass transfer coefficient at different percentages of pulp consistency. The rate of dissolution of copper increases with the increase in solution velocity, thus confirming the diffusion controlled nature of the corrosion process (Sedahmed et al., 1999; Shehata et al., 2002; Abdel-Aziz, 2011). The data fit the equation:
(5)
where C0 , C are initial and final dichromate concentration respectively; k is the mass transfer coefficient; A is the inside surface area of the copper pipe; t is the time and Q is the
Fig. 2 – ln(C0 /C) vs time at different solution velocities (0.0003 M K2 Cr2 O7 + 0.5 M H2 SO4 , pulp consistency = 0.2%, temp = 22 ◦ C). Solution velocity (cm/s.): – 63.6, – 53.07, × – 39.8, – 16.67, 䊉 – 13.26 and + – 9.95.
k ∝ V 0.51
(6)
The exponent in Eq. (6) is consistent with the prediction of the hydrodynamic boundary layer theory according to which k increases with V as a result of the decrease in the diffusion layer thickness (Incropera and Dewitt, 2005). Fig. 3 also shows that for a given solution velocity, the mass transfer coefficient decreases with increasing the pulp consistency. The decrease of mass transfer coefficient with the increase in pulp consistency is attributed to the fact that, (i) the physical nature of the pulp fibers as it forms flocs and coherent networks which interlock at low/moderate concentration to form three-dimensional structures or networks which in liquid suspension alter the physical and transport properties of the suspension (Reese et al., 1996), so by increasing the pulp concentration the diffusion coefficient of dichromate ions in solution decrease as the viscosity of solution increases, also the diffusivity of the depolarizer decreases due to the obstruction effect of the pulp suspension (Cussler, 1988), (ii) by virtue of the drag reducing ability of the pulp (Newazkazi et al., 1999; Higgins and Wahern, 1982) the small scale high frequency eddies existing in the hydrodynamic boundary layer are damped, as a consequence the diffusion layer across which the depolarizer diffuses to the pipe wall increases in thickness with a subsequent decrease in the rate corrosion. The mass transfer is related to the diffusion coefficient and the boundary
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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Table 1 – Effect of pulp slurry concentration on the % reduction in mass transfer coefficient. Solution velocity, cm/s
% reduction in k for different pulp consistency 0.1%
9.95 13.26 16.76 39.8 53.07 63.69
Fig. 4 – Effect of Re on Sh at different pulp consistency (pulp consistency: × – 0.1%, – 0.2% and – 0.3%).
layer thickness by the relation (k = D/ı) (Welty et al., 2008; Abdel-Aziz et al., 2013a,b)
3.6 5 6.8 10 11.3 11.7
0.2% 5.1 6.5 7.9 11.8 12.4 12.7
0.3% 6.2 7.2 9.6 14.8 15.9 16.1
An overall mass transfer correlation was envisaged using the dimensionless groups Sh, Sc and Re. Fig. 5 shows that the data for the conditions: 1133 < Re < 7311 and 1649 < Sc < 6559, fit the equation: Sh = 0.35Sc0.33 Re0.51
(10)
with an average deviation of ±8.4%.
3.2.
Data correlation
To correlate the present mass transfer data, the method of dimensional analysis was used (Welty et al., 2008). Dimensional analysis leads to the dimensionless equation:
Comparison of the rate of pipe corrosion in the 3.3. pulp slurry with the blank data
where a, ˛ and ˇ are constants. Following previous theoretical and experimental mass transfer studies, a Schmidt number exponent of 0.33 was used for correlating the present data (Pickett, 1977; Abdel-Aziz et al., 2012). Fig. 4 shows the effect of Re on Sh at different values of pulp consistency. The increase in the degree of turbulence with the increasing Re, increases Sh according to the equation:
Fig. 3 and Table 1 show that the addition of low amount of pulp consistency (0.1–0.3%) to the solution reduces the rate of mass transfer coefficient by an amount ranging from 3.6 to 16.1% depending on pulp consistency and solution velocity. The percentage reduction in mass transfer coefficient was found to increase with the increase in pulp concentration and solution velocity, but at high solution velocity the % reduction increases slightly. The slight increase in % reduction in mass transfer coefficient at high solution velocity may be attributed to the ability of pulp fibers to damp the small scale high frequency eddies existing at the pipe wall. Also, it would be of interest to compare the present mass transfer correlation obtained in the presence of pulp slurry, with the mass transfer correlation obtained in the absence of pulp slurry. Fig. 6 shows that the overall mass transfer correlation for the present study at a different dichromate concentration (absence of pulp) fit the equation:
Sh ∝ Re0.51
Sh = 0.26Sc0.33 Re0.59
kd =a D D
˛ Vd ˇ
(7)
i.e. Sh = aSc˛ Reˇ
(8)
(9)
(11)
Fig. 5 – Overall mass transfer correlation for corrosion of copper in acidified dichromate at different pulp consistency (Sc: × – 1649, – 2985 and – 6559). Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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metal corrosion. From Eqs. (1) and (2) the following equation can be concluded: NM = 2NO2
(12)
The dissolved oxygen flux (NO2 ) is given by Fick’s first law of diffusion: NO2 = −D
dC dx
(13)
Integration of Eq. (13) across the diffusion layer yields: NO2 = k(Cb − Ci )
Fig. 6 – Overall mass transfer correlation for corrosion of copper in acidified dichromate in the absence of pulp slurry (Sc: × – 850, – 1023 and – 1141).
(14)
Assuming that Ci = 0, where oxygen reduction occurs instantaneously at the surface. Eq. (14) reduces to: NO2 = kCb
(15)
and the rate of corrosion is given by: For the conditions: 2189 < Re < 14,011 and 850 < Sc < 1141, with an average deviation of ±7.6%. The power of Re (0.59) is consistent with the finding of Sedahmed et al. (1999), who studied the diffusion controlled corrosion of copper pipeline under turbulent axial flow where the power of Re was 0.58. Fig. 7 shows a comparison between the mass transfer data in the absence and in the presence of pulp. The data show that the presence of pulp in the solution decreases the rate of mass transfer and the effect becomes more significant as Re increases which confirms the drag reducing ability of the pulp (Newazkazi et al., 1999; Higgins and Wahern, 1982). The low Re exponent (0.51) obtained for the diffusion controlled corrosion of copper pipe in the presence of pulp slurry compared to that obtained in the absence of pulp (Re exponent is 0.59) confirms the role played by the pulp slurry in decreasing the rate of mass transfer and rate of metal corrosion. There may be a question which arises on how the present data can be used in estimating the rate of diffusion controlled corrosion. Knowledge of the rate of diffusion of dissolved oxygen to the metal surface can be used to determine the rate of
R = 2kCb
(16)
The present study will make it possible to determine the value of k [Eqs. (10) and (11)] and to estimate the rate of corrosion at the inner surface of the pipe [Eq. (16)].
4.
Conclusions
(1) The presence of pulp slurry in corrosive media was found to play an important role on the rate of diffusioncontrolled corrosion of metallic pipelines. Pulp fibers decrease the rate of diffusion controlled corrosion via (i) damping wall turbulence and, therefore, increase the diffusion layer thickness across which the depolarizer diffuses to the pipe wall, (ii) decreasing the depolarizer diffusivity by the obstruction effect of the pulp slurry. Although the % decrease in the rate of corrosion in pulp slurry is modest (3.6–16%) its economic impact is considerable in the long run. (2) The dimensionless equations obtained in the present study can be used to predict the corrosion rate and hence the corrosion allowance needed to design the pipelines. In case of heat exchangers the advantage of corrosion inhibition by pulp slurry should be weighed against the decrease in the rate of heat transfer, by virtue of the analogy between heat and mass transfer (Kayser, 1953; Abdel-Aziz et al., 2013b). It is hoped that the beneficial effect would outweigh the harmful effect. (3) The use of pulp slurry as corrosion inhibitors is the way forward in the search for safer and environmentally secure protection against metal corrosion.
References
Fig. 7 – Comparison of the mass transfer data in the absence and in the presence of pulp in the solution.
Abdel-Aziz, M.H., 2013. Solid–liquid mass transfer in relation to diffusion controlled corrosion at the outer surface of helical coils immersed in agitated vessels. Chem. Eng. Res. Des. 91, 43–50. Abdel-Aziz, M.H., Amin, N.K., El-Ashtoukhy, E-S.Z., 2013a. Removal of heavy metals from aqueous solutions by liquid cation exchanger in a jet loop contactor. Hydrometallurgy 137, 126–132. Abdel-Aziz, M.H., Mansour, I.A.S., Sedahmed, G.H., 2010. Study of the rate of liquid–solid mass transfer controlled processes in
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
CHERD-1482; No. of Pages 6
6
ARTICLE IN PRESS chemical engineering research and design x x x ( 2 0 1 4 ) xxx–xxx
helical tubes under turbulent flow conditions. Chem. Eng. Process. 49, 643–648. Abdel-Aziz, M.H., Nirdosh, I., Sedahmed, G.H., 2012. Mass transfer at a vertical oscillating screen stack in relation to catalytic and electrochemical reactor design. Ind. Eng. Chem. Res. 51, 11636–11642. Abdel-Aziz, M.H., Nirdosh, I., Sedahmed, G.H., 2013b. Liquid–solid mass and heat transfer behavior of a concentric tube airlift reactor. Int. J. Heat Mass Transfer 58, 735–739. Abdel-Aziz, M.H., 2011. Mass transfer behavior at horizontal cylinder under different flow conditions. Int. Commun. Heat Mass Transfer 38, 493–498. Cornet, I., Greif, R., Teng, J.T., Roehler, F., 1980. Mass transfer to rotating rods and plates. Int. J. Heat Mass Transfer 23, 805–811. Cussler, E.L., 1988. Diffusion Mass Transfer in Fluid Systems. Cambridge University Press, Cambridge. Findlay, A., Kitchener, J.A., 1965. Practical Physical Chemistry, 8th ed. Longmans, London. Fontana, M.G., 1987. Corrosion Engineering. McGraw-Hill, New York. Fouad, Y.O., Malash, G.F., Zatout, A.A., Sedahmed, G.H., 2013. Mass and heat transfer at an array of vertical tubes in a square stirred tank reactor. Chem. Eng. Res. Des. 91, 234–243. Gregory, D.P., Riddiford, A.C., 1960. Dissolution of copper in sulphuric acid. J. Electrochem. Soc. 107, 950–956. Higgins, B.G., Wahern, D., 1982. Optimum consistency for pumping pulp. TAPPI J. 65, 131–133. Hoyt, J.W., 1972. Effect of additives on fluid friction. Trans. ASME J. Basic Eng. 94, 258–285. Huhtanen, J.T., Karvinen, R.J., 2005. Interaction of non-Newtonian fluid dynamics and turbulence on the behavior of pulp suspension flows. Ann. Trans. Nordic Rheol. Soc., 13. Incropera, F.P., Dewitt, D.P., 2005. Fundamentals of Heat and Mass Transfer, 6th ed. John Wiley & Sons, New York. Kayser, R.F., 1953. Analogy among heat, mass, and momentum transfer. Ind. Eng. Chem. 45, 2634–2636. Little, R.C., Hansen, R.J., Hunston, D.L., Kim, O.K., Patterson, R.L., Ting, R.V., 1975. The drag reduction phenomenon, observed characteristics, improved agents proposed mechanisms. Ind. Eng. Chem. 14, 283–296. Madden, J., Nelson, D.G., 1964. A novel technique for determining mass transfer coefficients in agitated solid–liquid system. AIChE J. 10, 415–430. Newazkazi, M.S., Duffy, G.G., Dong Chen, X., 1999. Heat transfer in the drag reducing regime of wood pulp fiber suspensions. Chem. Eng. J. 73, 247–253. Patil, V.K., Sharma, M.M., 1983. Hydrodynamics and mass transfer characteristics of co-current down flow packed tube column. Can. J. Chem. Eng. 61, 509–516.
Pickett, D.J., 1977. Electrochemical Reactor Design. Elsevier, New York. Reese, J., Jiang, P., Fan, L.S., 1996. Bubble characteristics in three-phase systems used for pulp and paper processing. Chem. Eng. Sci. 51, 2501–2510. Schmitt, G., 1996. Drag reduction – an important contribution to the protective action of corrosion inhibitors and surfactants in corrosive flow system. In: Fourth International Workshop on Electrochemical Flow Measurements, Fundamentals and Applications, Lahnstein, Germany. Sedahmed, G.H., 2005. The use of drag reducing polymers to combat diffusion controlled corrosion and erosion-corrosion in equipments operating under turbulent flow – a review. Trends Chem. Eng. 9, 65–72. Sedahmed, G.H., Abdo, M.S.E., Amer, M.A., Abd El-Latif, G., 1999. Effect of drag reducing polymers on the rate of mass transfer controlled corrosion in pipelines under developing turbulent flow. Int. Commun. Heat Mass Transfer 26, 531–538. Sedahmed, G.H., Farag, H.A., Kayar, A.M., El-Nashar, I.M., 1998. Mass transfer at the impellers of agitated vessels in relation to their flow induced corrosion. Chem. Eng. J. 71, 57–65. Sedahmed, G.H., Khatab, M.A., Mahgob, F.M., Al-Azzony, M.R., 2004. Solid liquid mass transfer at the base of a rectangular agitated vessel. Chem. Eng. Commun. 191, 168–181. Sellin, R.H., Hoyt, J.W., Scrivener, O., 1982. The effect of drag-reducing additives on fluid flows and their industrial applications. Part 1: Basic aspects. J. Hydraul. Res. 20, 29–68. Shehata, A.S., Nosier, S.A., Sedahmed, G.H., 2002. The role of mass transfer in the flow-induced corrosion of equipments employing decaying swirl flow. Chem. Eng. Process. 41, 659–666. Vogel, I., 1985. A Text Book of Quantitative Inorganic Analysis. Longmans, London. Walsh, F., 1993. A First Course in Electrochemical Engineering. The Electrochemical Consultancy, Romsey, UK. Welty, J.R., Wicks, C.E., Wilson, R.E., Rorrer, G., 2008. Fundamentals of Momentum Heat and Mass Transfer, 4th ed. John Wiley & Sons, USA. Zahran, R.R., Sedahmed, G.H., 1998. Effect of drag reducing polymers on the rate of flow induced corrosion of metals. Mater. Lett. 35, 207–213. Zaki, M.M., Nirdosh, I., Sedahemd, G.H., 1997. Forced convection mass transfer inside large hemispherical cavities under laminar flow conditions. Chem. Eng. Commun. 159, 161–171. Zakin, J.L., Lu, B., Bewersdorff, H.W., 1998. Surfactant drag reduction. Rev. Chem. Eng. J. 14, 253–262.
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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Contents lists available at ScienceDirect
Chemical Engineering Research and Design journal homepage: www.elsevier.com/locate/cherd
Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions N.K. Amin a , M.H. Abdel-Aziz a,b,∗ , E-S.Z. El-Ashtoukhy a a
Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt Chemical and Materials Engineering Department, Faculty of Engineering, King Abdulaziz University, Rabigh 21911, Saudi Arabia
b
a b s t r a c t The present study aimed to investigate the corrosion behavior of a pipeline carrying dilute pulp fiber suspensions (0.1–0.3% consistency). To examine the role played by pulp fibers on the rate of diffusion controlled corrosion of metals an accelerated test which involved the diffusion controlled dissolution of copper in acidified dichromate was used under turbulent flow conditions. Different concentrations of pulp fibers at different solution velocities were studied. The rate of mass transfer controlled corrosion of copper was found to increase by increasing solution velocity and decrease by increasing pulp consistency. The data in the presence and absence of the pulp slurry were correlated by dimensionless equations. The importance of the present results in estimating the rate of corrosion in equipment used in the pulp and paper industry especially pipelines and heat exchangers were highlighted. The decrease in the rate of diffusion controlled corrosion in the presence of the pulp was explained in terms of the drag reducing ability of pulp slurry. © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. Keywords: Corrosion; Corrosion inhibition; Diffusion; Mass transfer; Pipe flow; Pulp and paper
1.
or :
Introduction
Corrosion of metals is a big problem in chemical, pulp and petroleum industry as it gives rise to enormous financial losses. The cost of corrosion for the pulp industry was only estimated at approximately $808.5 million per year as corrosion affects production as follows: (i) corrosion products polluting the paper, (ii) corrosion of rolls scarring the sheets of paper, (iii) corrosion of components may also result in fractures. Corrosion of metals takes place through the formation of a galvanic cell which consists of an anode and cathode, where the following reactions take place: Anode reaction : M → M++ + 2e (1)
Cathode reaction :
(1/2)O2 + H2 O + 2e → 2OH−
(pH 4–10) (2)
2H+ + 2e → H2
(pH < 4)
(3)
Each of the above reactions is a heterogeneous reaction which involves two steps namely, (i) a diffusion step where the reactant (O2 or H+ ) has to diffuse to the metal surface from solution bulk, (ii) charge transfer step (chemical step) where a chemical reaction takes place at a metal surface. The overall rate of corrosion is determined by the slowest step of anodic and cathodic reactions, it was found that in the pH range 4–10 the rate determining step is the diffusion of O2 from the solution bulk to the metal surface such as copper and steel which are the most widely used materials of construction in the industry. Under these conditions corrosion is described as diffusion controlled corrosion (Fontana, 1987; Zaki et al., 1997; Sedahmed et al., 2004; Cornet et al., 1980; Abdel-Aziz, 2013; Fouad et al., 2013). The aim of the present work is to shed some light on the diffusion controlled corrosion of pipelines used in the pulp and paper industry, where the flow of dilute water fiber
∗
Corresponding author at: Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt. Tel.: +20 3 5745962; fax: +20 3 59211853. E-mail address: [email protected] (M.H. Abdel-Aziz). Received 27 September 2013; Received in revised form 28 December 2013; Accepted 18 January 2014 0263-8762/$ – see front matter © 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cherd.2014.01.023 Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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Nomenclature A a C C0 Cb Ci D d N k Q R t V ı ˛, ˇ Re Sc Sh
pipe inside surface area (cm2 ) constant concentration at time t (mol/cm3 ) initial concentration (mol/cm3 ) bulk concentration, (mol/cm3 ) concentration at the interface (mol/cm3 ) diffusion coefficient (cm2 /s) pipe inside diameter (cm) mole flux (mol/cm2 s) mass transfer coefficient (cm/s) solution volume (cm3 ) rate of corrosion (mm/year) time (s) solution velocity (cm/s) solution viscosity (g cm−1 s−1 ) solution density (g cm−3 ) diffusion layer thickness (cm) constants Reynolds number, Vd/ Schmidt number, /D Sherwood number, kd/D
suspensions (consistency < 1%) in a pipe line which is similar to the flow in a paper machine head-box, and the flow conditions there determine the quality of produced paper. Flow of dilute water-fiber suspensions over a backward facing step is present in many unit processes in paper production, especially in the wet end of paper machine, and is an important mixing element for fiber suspension flows, because it is very effective turbulence generator (Huhtanen and Karvinen, 2005). To this end, an accelerated test was used namely, the diffusion controlled dissolution of copper in acidified dichromate which simulates natural diffusion controlled corrosion of metals in the pH range 4–10. The system has been used widely to study diffusion controlled corrosion of metals under different hydrodynamic conditions (Cornet et al., 1980; Abdel-Aziz, 2013; Sedahmed et al., 1998; Abdel-Aziz et al., 2010; Madden and Nelson, 1964; Patil and Sharma, 1983). Pipes are used in the pulp and paper industry to transfer the slurry between different units and in fabricating heat exchangers used to handle pulp slurry. Accordingly study of the corrosion behavior of pipes carrying pulp slurry is important for estimating the rate of corrosion and hence the corrosion allowance needed in the design stage of these pipelines and heat exchangers. Studies of the flow behavior of pulp slurries (Newazkazi et al., 1999; Higgins and Wahern, 1982) have revealed that under turbulent flow conditions pulp slurries exhibit drag reducing properties, i.e. the pressure drop across the pipeline carrying pulp slurry is less than that carrying water. The decrease in friction between the turbulently flowing pulp suspension and the wall of the pipeline is explained by the ability of pulp fibers to damp the small scale high frequency energy dissipating eddies which exist in the hydrodynamic boundary layer on the pipe wall (Sedahmed, 2005; Cussler, 1988; Sellin et al., 1982; Hoyt, 1972; Little et al., 1975). Since small scale high frequency eddies enhance the rate of depolarizer (dissolved O2 or K2 Cr2 O7 ) diffusion to the wall of the pipeline, it is expected that the presence of paper pulp which damps these eddies would decrease the rate of depolarizer diffusion and the rate of pipeline corrosion. The main aim of the present work is
Fig. 1 – Apparatus. (1) Plexiglas tank, (2) liquid level, (3) plastic centrifugal pump, (4) control valves, (5) rotameter and (6) copper tube. to find out the extent to which the presence of pulp slurry inhibits the diffusion controlled corrosion. Although the use of drag reducing polymers as corrosion inhibitors has been studied (Sedahmed, 2005; Sedahmed et al., 1998; Zahran and Sedahmed, 1998; Zakin et al., 1998; Schmitt, 1996), no work has been reported in the literature on the inhibiting effect of pulp slurry on the rate of diffusion controlled corrosion despite its industrial importance for the pulp and paper industry.
2.
Experimental part
2.1.
Materials
Three different concentrations of acidified potassium dichromate solution were used namely; 0.003 M K2 Cr2 O7 + 0.5 M H2 SO4 , 0.003 M K2 Cr2 O7 + 1 M H2 SO4 , 0.003 M K2 Cr2 O7 + 1.5 M H2 SO4 . All solutions were prepared from AR chemicals and distilled water. The pulp slurry used in the present study was taken from Rakta s Pulp and Paper Company, located in Alexandria, Egypt. Rakta s Pulp and Paper Company produces writing and printing paper from soda pulping of rice straw, and hypochlorite bleaching of the produced pulp. The test metal section was a copper pipe of 2 cm inside diameter and 100 cm length. Based on previous studies (Abdel-Aziz et al., 2010; Madden and Nelson, 1964; Patil and Sharma, 1983) dissolution of copper in acidified dichromate is diffusion controlled.
2.2.
Experimental technique
Fig. 1 shows the experimental setup used in the present study. It consists of 15 L Plexiglas storage tank, a 0.25 hp plastic centrifugal pump, and a vertical copper pipe of 2 cm inside
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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diameter and 100 cm length. The acidified K2 Cr2 O7 solution was circulated through the system between the pipe and the storage tank by means of plastic pump. Eight liters of fresh acidified dichromate solution were used in each experiment. The solution flow rate was controlled by a bypass and was measured by a rotameter. For each concentration of acidified K2 Cr2 O7 solution three different pulp slurry consistencies (Pulp consistency = (weigh of pulp/(weight of pulp + weight of water)) × 100) were used namely; 0.1, 0.2, and 0.3% pulp consistency. The duration of each experiment was 30 min. The rate of copper dissolution in acidified dichromate solution was followed by withdrawing 5 cm3 samples at 3 min intervals for dichromate analysis. Dichromate was analyzed by using a UV spectrophotometer (Shimadzu Model: UV 1601) with diphenylcarbazide indicator at 540 nm (Vogel, 1985). Experiments were conducted at a temperature ranging from 22 to 25 ◦ C. The physical properties of solution needed for data correlation (solution density and viscosity) were measured by a density bottle and an Ostwald viscometer, respectively (Findlay and Kitchener, 1965). The diffusivity of dichromate was obtained from the literature (Madden and Nelson, 1964; Gregory and Riddiford, 1960).
3.
Results and discussion
The mass transfer coefficient of the diffusion controlled corrosion of copper pipe in acidified dichromate containing pulp slurry was obtained under different conditions from the dichromate concentration-time data. Fig. 2 shows that the data for the present batch recirculating reactor fit the equation (Pickett, 1977; Walsh, 1993): −Q
dC = kAC dt
(4)
which upon integration yields: ln
C0 kA = t C Q
Fig. 3 – Effect of solution velocity on mass transfer coefficient at different pulp consistency (0.0003 M K2 Cr2 O7 + 0.5 M H2 SO4 , temp = 22 ◦ C). Pulp consistency: × – 0% (blank), – 0.1%, – 0.2% and – 0.3%. volume of the solution in the tank. The mass transfer coefficient was calculated from the slope of ln(C0 /C) vs. t line (Fig. 2). The rate of dissolution of copper is expressed in terms of mass transfer coefficient, which was determined for different pulp consistencies at different solution velocities.
3.1. Effect of pulp consistency on rate of diffusion controlled corrosion of the pipe wall Fig. 3 shows the effect of solution velocity on the mass transfer coefficient at different percentages of pulp consistency. The rate of dissolution of copper increases with the increase in solution velocity, thus confirming the diffusion controlled nature of the corrosion process (Sedahmed et al., 1999; Shehata et al., 2002; Abdel-Aziz, 2011). The data fit the equation:
(5)
where C0 , C are initial and final dichromate concentration respectively; k is the mass transfer coefficient; A is the inside surface area of the copper pipe; t is the time and Q is the
Fig. 2 – ln(C0 /C) vs time at different solution velocities (0.0003 M K2 Cr2 O7 + 0.5 M H2 SO4 , pulp consistency = 0.2%, temp = 22 ◦ C). Solution velocity (cm/s.): – 63.6, – 53.07, × – 39.8, – 16.67, 䊉 – 13.26 and + – 9.95.
k ∝ V 0.51
(6)
The exponent in Eq. (6) is consistent with the prediction of the hydrodynamic boundary layer theory according to which k increases with V as a result of the decrease in the diffusion layer thickness (Incropera and Dewitt, 2005). Fig. 3 also shows that for a given solution velocity, the mass transfer coefficient decreases with increasing the pulp consistency. The decrease of mass transfer coefficient with the increase in pulp consistency is attributed to the fact that, (i) the physical nature of the pulp fibers as it forms flocs and coherent networks which interlock at low/moderate concentration to form three-dimensional structures or networks which in liquid suspension alter the physical and transport properties of the suspension (Reese et al., 1996), so by increasing the pulp concentration the diffusion coefficient of dichromate ions in solution decrease as the viscosity of solution increases, also the diffusivity of the depolarizer decreases due to the obstruction effect of the pulp suspension (Cussler, 1988), (ii) by virtue of the drag reducing ability of the pulp (Newazkazi et al., 1999; Higgins and Wahern, 1982) the small scale high frequency eddies existing in the hydrodynamic boundary layer are damped, as a consequence the diffusion layer across which the depolarizer diffuses to the pipe wall increases in thickness with a subsequent decrease in the rate corrosion. The mass transfer is related to the diffusion coefficient and the boundary
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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Table 1 – Effect of pulp slurry concentration on the % reduction in mass transfer coefficient. Solution velocity, cm/s
% reduction in k for different pulp consistency 0.1%
9.95 13.26 16.76 39.8 53.07 63.69
Fig. 4 – Effect of Re on Sh at different pulp consistency (pulp consistency: × – 0.1%, – 0.2% and – 0.3%).
layer thickness by the relation (k = D/ı) (Welty et al., 2008; Abdel-Aziz et al., 2013a,b)
3.6 5 6.8 10 11.3 11.7
0.2% 5.1 6.5 7.9 11.8 12.4 12.7
0.3% 6.2 7.2 9.6 14.8 15.9 16.1
An overall mass transfer correlation was envisaged using the dimensionless groups Sh, Sc and Re. Fig. 5 shows that the data for the conditions: 1133 < Re < 7311 and 1649 < Sc < 6559, fit the equation: Sh = 0.35Sc0.33 Re0.51
(10)
with an average deviation of ±8.4%.
3.2.
Data correlation
To correlate the present mass transfer data, the method of dimensional analysis was used (Welty et al., 2008). Dimensional analysis leads to the dimensionless equation:
Comparison of the rate of pipe corrosion in the 3.3. pulp slurry with the blank data
where a, ˛ and ˇ are constants. Following previous theoretical and experimental mass transfer studies, a Schmidt number exponent of 0.33 was used for correlating the present data (Pickett, 1977; Abdel-Aziz et al., 2012). Fig. 4 shows the effect of Re on Sh at different values of pulp consistency. The increase in the degree of turbulence with the increasing Re, increases Sh according to the equation:
Fig. 3 and Table 1 show that the addition of low amount of pulp consistency (0.1–0.3%) to the solution reduces the rate of mass transfer coefficient by an amount ranging from 3.6 to 16.1% depending on pulp consistency and solution velocity. The percentage reduction in mass transfer coefficient was found to increase with the increase in pulp concentration and solution velocity, but at high solution velocity the % reduction increases slightly. The slight increase in % reduction in mass transfer coefficient at high solution velocity may be attributed to the ability of pulp fibers to damp the small scale high frequency eddies existing at the pipe wall. Also, it would be of interest to compare the present mass transfer correlation obtained in the presence of pulp slurry, with the mass transfer correlation obtained in the absence of pulp slurry. Fig. 6 shows that the overall mass transfer correlation for the present study at a different dichromate concentration (absence of pulp) fit the equation:
Sh ∝ Re0.51
Sh = 0.26Sc0.33 Re0.59
kd =a D D
˛ Vd ˇ
(7)
i.e. Sh = aSc˛ Reˇ
(8)
(9)
(11)
Fig. 5 – Overall mass transfer correlation for corrosion of copper in acidified dichromate at different pulp consistency (Sc: × – 1649, – 2985 and – 6559). Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
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metal corrosion. From Eqs. (1) and (2) the following equation can be concluded: NM = 2NO2
(12)
The dissolved oxygen flux (NO2 ) is given by Fick’s first law of diffusion: NO2 = −D
dC dx
(13)
Integration of Eq. (13) across the diffusion layer yields: NO2 = k(Cb − Ci )
Fig. 6 – Overall mass transfer correlation for corrosion of copper in acidified dichromate in the absence of pulp slurry (Sc: × – 850, – 1023 and – 1141).
(14)
Assuming that Ci = 0, where oxygen reduction occurs instantaneously at the surface. Eq. (14) reduces to: NO2 = kCb
(15)
and the rate of corrosion is given by: For the conditions: 2189 < Re < 14,011 and 850 < Sc < 1141, with an average deviation of ±7.6%. The power of Re (0.59) is consistent with the finding of Sedahmed et al. (1999), who studied the diffusion controlled corrosion of copper pipeline under turbulent axial flow where the power of Re was 0.58. Fig. 7 shows a comparison between the mass transfer data in the absence and in the presence of pulp. The data show that the presence of pulp in the solution decreases the rate of mass transfer and the effect becomes more significant as Re increases which confirms the drag reducing ability of the pulp (Newazkazi et al., 1999; Higgins and Wahern, 1982). The low Re exponent (0.51) obtained for the diffusion controlled corrosion of copper pipe in the presence of pulp slurry compared to that obtained in the absence of pulp (Re exponent is 0.59) confirms the role played by the pulp slurry in decreasing the rate of mass transfer and rate of metal corrosion. There may be a question which arises on how the present data can be used in estimating the rate of diffusion controlled corrosion. Knowledge of the rate of diffusion of dissolved oxygen to the metal surface can be used to determine the rate of
R = 2kCb
(16)
The present study will make it possible to determine the value of k [Eqs. (10) and (11)] and to estimate the rate of corrosion at the inner surface of the pipe [Eq. (16)].
4.
Conclusions
(1) The presence of pulp slurry in corrosive media was found to play an important role on the rate of diffusioncontrolled corrosion of metallic pipelines. Pulp fibers decrease the rate of diffusion controlled corrosion via (i) damping wall turbulence and, therefore, increase the diffusion layer thickness across which the depolarizer diffuses to the pipe wall, (ii) decreasing the depolarizer diffusivity by the obstruction effect of the pulp slurry. Although the % decrease in the rate of corrosion in pulp slurry is modest (3.6–16%) its economic impact is considerable in the long run. (2) The dimensionless equations obtained in the present study can be used to predict the corrosion rate and hence the corrosion allowance needed to design the pipelines. In case of heat exchangers the advantage of corrosion inhibition by pulp slurry should be weighed against the decrease in the rate of heat transfer, by virtue of the analogy between heat and mass transfer (Kayser, 1953; Abdel-Aziz et al., 2013b). It is hoped that the beneficial effect would outweigh the harmful effect. (3) The use of pulp slurry as corrosion inhibitors is the way forward in the search for safer and environmentally secure protection against metal corrosion.
References
Fig. 7 – Comparison of the mass transfer data in the absence and in the presence of pulp in the solution.
Abdel-Aziz, M.H., 2013. Solid–liquid mass transfer in relation to diffusion controlled corrosion at the outer surface of helical coils immersed in agitated vessels. Chem. Eng. Res. Des. 91, 43–50. Abdel-Aziz, M.H., Amin, N.K., El-Ashtoukhy, E-S.Z., 2013a. Removal of heavy metals from aqueous solutions by liquid cation exchanger in a jet loop contactor. Hydrometallurgy 137, 126–132. Abdel-Aziz, M.H., Mansour, I.A.S., Sedahmed, G.H., 2010. Study of the rate of liquid–solid mass transfer controlled processes in
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023
CHERD-1482; No. of Pages 6
6
ARTICLE IN PRESS chemical engineering research and design x x x ( 2 0 1 4 ) xxx–xxx
helical tubes under turbulent flow conditions. Chem. Eng. Process. 49, 643–648. Abdel-Aziz, M.H., Nirdosh, I., Sedahmed, G.H., 2012. Mass transfer at a vertical oscillating screen stack in relation to catalytic and electrochemical reactor design. Ind. Eng. Chem. Res. 51, 11636–11642. Abdel-Aziz, M.H., Nirdosh, I., Sedahmed, G.H., 2013b. Liquid–solid mass and heat transfer behavior of a concentric tube airlift reactor. Int. J. Heat Mass Transfer 58, 735–739. Abdel-Aziz, M.H., 2011. Mass transfer behavior at horizontal cylinder under different flow conditions. Int. Commun. Heat Mass Transfer 38, 493–498. Cornet, I., Greif, R., Teng, J.T., Roehler, F., 1980. Mass transfer to rotating rods and plates. Int. J. Heat Mass Transfer 23, 805–811. Cussler, E.L., 1988. Diffusion Mass Transfer in Fluid Systems. Cambridge University Press, Cambridge. Findlay, A., Kitchener, J.A., 1965. Practical Physical Chemistry, 8th ed. Longmans, London. Fontana, M.G., 1987. Corrosion Engineering. McGraw-Hill, New York. Fouad, Y.O., Malash, G.F., Zatout, A.A., Sedahmed, G.H., 2013. Mass and heat transfer at an array of vertical tubes in a square stirred tank reactor. Chem. Eng. Res. Des. 91, 234–243. Gregory, D.P., Riddiford, A.C., 1960. Dissolution of copper in sulphuric acid. J. Electrochem. Soc. 107, 950–956. Higgins, B.G., Wahern, D., 1982. Optimum consistency for pumping pulp. TAPPI J. 65, 131–133. Hoyt, J.W., 1972. Effect of additives on fluid friction. Trans. ASME J. Basic Eng. 94, 258–285. Huhtanen, J.T., Karvinen, R.J., 2005. Interaction of non-Newtonian fluid dynamics and turbulence on the behavior of pulp suspension flows. Ann. Trans. Nordic Rheol. Soc., 13. Incropera, F.P., Dewitt, D.P., 2005. Fundamentals of Heat and Mass Transfer, 6th ed. John Wiley & Sons, New York. Kayser, R.F., 1953. Analogy among heat, mass, and momentum transfer. Ind. Eng. Chem. 45, 2634–2636. Little, R.C., Hansen, R.J., Hunston, D.L., Kim, O.K., Patterson, R.L., Ting, R.V., 1975. The drag reduction phenomenon, observed characteristics, improved agents proposed mechanisms. Ind. Eng. Chem. 14, 283–296. Madden, J., Nelson, D.G., 1964. A novel technique for determining mass transfer coefficients in agitated solid–liquid system. AIChE J. 10, 415–430. Newazkazi, M.S., Duffy, G.G., Dong Chen, X., 1999. Heat transfer in the drag reducing regime of wood pulp fiber suspensions. Chem. Eng. J. 73, 247–253. Patil, V.K., Sharma, M.M., 1983. Hydrodynamics and mass transfer characteristics of co-current down flow packed tube column. Can. J. Chem. Eng. 61, 509–516.
Pickett, D.J., 1977. Electrochemical Reactor Design. Elsevier, New York. Reese, J., Jiang, P., Fan, L.S., 1996. Bubble characteristics in three-phase systems used for pulp and paper processing. Chem. Eng. Sci. 51, 2501–2510. Schmitt, G., 1996. Drag reduction – an important contribution to the protective action of corrosion inhibitors and surfactants in corrosive flow system. In: Fourth International Workshop on Electrochemical Flow Measurements, Fundamentals and Applications, Lahnstein, Germany. Sedahmed, G.H., 2005. The use of drag reducing polymers to combat diffusion controlled corrosion and erosion-corrosion in equipments operating under turbulent flow – a review. Trends Chem. Eng. 9, 65–72. Sedahmed, G.H., Abdo, M.S.E., Amer, M.A., Abd El-Latif, G., 1999. Effect of drag reducing polymers on the rate of mass transfer controlled corrosion in pipelines under developing turbulent flow. Int. Commun. Heat Mass Transfer 26, 531–538. Sedahmed, G.H., Farag, H.A., Kayar, A.M., El-Nashar, I.M., 1998. Mass transfer at the impellers of agitated vessels in relation to their flow induced corrosion. Chem. Eng. J. 71, 57–65. Sedahmed, G.H., Khatab, M.A., Mahgob, F.M., Al-Azzony, M.R., 2004. Solid liquid mass transfer at the base of a rectangular agitated vessel. Chem. Eng. Commun. 191, 168–181. Sellin, R.H., Hoyt, J.W., Scrivener, O., 1982. The effect of drag-reducing additives on fluid flows and their industrial applications. Part 1: Basic aspects. J. Hydraul. Res. 20, 29–68. Shehata, A.S., Nosier, S.A., Sedahmed, G.H., 2002. The role of mass transfer in the flow-induced corrosion of equipments employing decaying swirl flow. Chem. Eng. Process. 41, 659–666. Vogel, I., 1985. A Text Book of Quantitative Inorganic Analysis. Longmans, London. Walsh, F., 1993. A First Course in Electrochemical Engineering. The Electrochemical Consultancy, Romsey, UK. Welty, J.R., Wicks, C.E., Wilson, R.E., Rorrer, G., 2008. Fundamentals of Momentum Heat and Mass Transfer, 4th ed. John Wiley & Sons, USA. Zahran, R.R., Sedahmed, G.H., 1998. Effect of drag reducing polymers on the rate of flow induced corrosion of metals. Mater. Lett. 35, 207–213. Zaki, M.M., Nirdosh, I., Sedahemd, G.H., 1997. Forced convection mass transfer inside large hemispherical cavities under laminar flow conditions. Chem. Eng. Commun. 159, 161–171. Zakin, J.L., Lu, B., Bewersdorff, H.W., 1998. Surfactant drag reduction. Rev. Chem. Eng. J. 14, 253–262.
Please cite this article in press as: Amin, N.K., et al., Effect of pulp fiber suspensions on the rate of mass transfer controlled corrosion in pipelines under turbulent flow conditions. Chem. Eng. Res. Des. (2014), http://dx.doi.org/10.1016/j.cherd.2014.01.023