failure analysis of flue gas duct in a steam power...

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:20 No:01 48

200101-9797-IJMME-IJENS © February 2020 IJENS I J E N S

Failure Analysis of Flue Gas Duct in a Steam

Power Plant Ahmed F. Mohamed1, 2, Mohammad E. Habash1, Mohammad S. AlSoufi1, Mohamed K. Hassan1, 3

1Mechanical Engineering Department, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah,

KSA 2Mechanical Engineering Department, Faculty of Engineering, Sohag University, Egypt

3Production Engineering & Design Dept., Faculty of Engineering, Minia University, Egypt

Abstract-- Power plant consists of systems that effect on each

other. The main two cycles in power plant are Water – Steam

and Air – Gas cycles. Flue gas duct is used in air-gas cycle to

release the flue gas from the furnace to the atmosphere. The

cracks and holes occur in the gas duct because of corrosion,

which resulted in allowing the air ingress into the duct and

consequently cause a chemical reaction with flue gas, this

reaction will create a sulfuric acid layer and hence accumulate

on the internal surfaces of the duct and transfer to Induced

Draft Fan (IDF). The main objective of this work is to introduce

a composite layer to Corten Steel (the material from which the

gas duct made) to improve a corrosion resistance. This coating

layer consists from serval nanoparticles (ZnO, ZrO2, SiO2 and

NiO) as reinforcement phase with epoxy resins matrix. The

surface roughness profiles of Nano-epoxy composite coating

show an improvement in surface roughness compared to the

original Corten Steel without coating. Furthermore, XRF

analysis shows the Nano-epoxy composite coating element and

the increment of element that improve corrosion resistance.

Index Term-- Flue Gas Duct, Nano-Epoxy Composite Coating,

Nanoparticles, Surface Roughness, ZnO, ZrO2, SiO2, NiO.

1. INTRODUCTION

Air gas cycle in steam power plant starts from

sucking the air from atmosphere by means of Forced Draft

Fan (FDF) to supply boiler furnace with enough air for

combustion. Then air flows through two stages before reach the boiler. The first stage is Steam Coil Air Preheater

(SCAPH), it is used to raise the air temperature by make the

air flows through steam coil and the second stage is Air

Preheater, it is also used to raise the air temperature by

exchange the heat between air and flue gas, as shown in

Figure 1. The flue gas duct is made from Corten Steel with 6

mm thickness and materials used for insulation are minerals

wool 250 mm with density 100 kg/m3 and covered by

aluminum sheet 1.3 mm.

Fig. 1. Air- Gas cycle in steam power plant



To release the flue gas by using Induced Draft Fan

(IDF) connected to boiler by duct. This duct get damaged in

a certain area causes cracks and holes, due to corrosion, these

damages let the air enter inside the duct and react with the

flue gas, which causes the composition of sulfuric acid (SOx)

and ash causing corrosion and starts to accumulate on the

internal surface of duct and on IDF, as shown in Figure 2.

Fig. 2. Cracks and corrosion as found on internal surface of flue gas duct

The objective of this work is to study the

improvement of the properties of the flue gas duct's material

by using the composite material with different types of Nano-

Particles with resins epoxy as a coating by applying different

characterization analysis such as, Surface Roughness, XRF

and XRD.

A brief literature review of failure analysis of flue

gas duct and other aspects of metal protection are introduced.

Z.B. Wang, [1] carried out the study of the Performance of

corrosion protection for Nano-SiO2/Epoxy Composite

Coatings in Acidic Desulfurized Flue Gas Condensates. A

series of nano-SiO2/epoxy composite coatings were

designed to improve both the acid resistance and thermos

resistance by considering the addition order of the surface-

modified nano-SiO2 and the sealing effect on the micro holes.

Takehide AIGA, [2] introduced a study of advanced anticorrosion coating technologies in steelworks

maintenance. Corrosive environment such as marine

environment and corrosive gas environment investigate these

corrosive conditions and apply advanced anti-corrosion

coating technologies, aiming to minimize the LCC (Life Cycle Cost) of industrial facilities. Evaluation methods of the

coating performance and application technologies such as

Coating Film Diagnosis Technology and Anticorrosion

Coating Technologies are introduced.

Tuan Anh Nguyen, [3] performed the study of the

Effect of Nanoparticles on the Thermal and Mechanical

Properties of Epoxy Coatings. Epoxy coatings incorporated

with several nanoparticles, such as nano-SiO2, nano-Fe2O3,

nano- clay and nano-TiO2, were synthesized on the surface

of steel substrates by solvent sonication and room

temperature curing of fully mixed epoxy slurry.

2. EXPERIMENTAL WORK

2.1 Material

Corten steel, epoxy, and nanoparticles are materials

used in the experimental work. Corten steel are weather

resistant steel grades optimized through their alloying

elements copper, chromium, nickel and phosphorus for a variety of environments and purposes. The main properties of

this type of steel are corrosion resistant [4].

Belzona 1391T is a 2-part ceramic filled epoxy coating which provides erosion and corrosion resistance

to high temperature equipment operating under immersion up

to 120°C. It offers excellent resistance to a wide range of

aqueous solutions, hydrocarbons and process chemicals, [5].

Four types of Nanoparticles are used in this work

are: Zinc Oxide (ZnO, 99%, 35-45 nm), Zirconium Oxide

Nanoparticles (ZrO2, 99+%, 40 nm), Silicon Dioxide

Nanoparticles (SiO2, 99+%, 20-30 nm) and Nickel Oxide

Nanoparticles (NiO, 99%, 10-20 nm), [6].

2.2 Preparation of Composite Coatings

Matrices of all prepared composite coatings is epoxy

resins (Type 1391T from BELZONA Co.) and the

reinforcement are four types of nanoparticles. The epoxy

mixed with different ratios of the nanoparticles as shown in

Table I.



Table I

Composite coating samples and percentage combination

Sample Code Composite Coating Percentages No. of

Samples

EPX Epoxy Pure Epoxy 1

EZn Epoxy with Nanoparticles ZnO 2, 4, 6 and 8 % with Epoxy 4 EZr Epoxy with Nanoparticles ZrO2 2, 4, 6 and 8 % with Epoxy 4

ESi Epoxy with Nanoparticles SiO2 2, 4, 6 and 8 % with Epoxy 4

ENi Epoxy with Nanoparticles NiO 2, 4, 6 and 8 % with Epoxy 4

The five composite coatings are applying on 16

different pieces of corten steel, with different intensity

percentage of 2, 4, 6 and 8% and one piece of corten steel to

applying pure epoxy. Figures 3 and 4, show the preparation

of nano-epoxy composite coatings.

Fig. 3. Materials and tools used equipped for preparing samples.



Fig. 4. Samples after coating with a layer of nano-epoxy composite coating.

2.3 Experimental Tests

In this section, Surface Roughness, XRF and XRD

test were performed on all samples. Stylus based technique

used to find surface roughness profile, a stylus based

equipment by Taylor Hobson, tracks small changes in surface

height, and a skid that follows large changes in surface

height. The use of both of them together reduces the effects

of non-flat surfaces on the surface roughness measurement.

X-ray fluorescence (XRF) is to analysis the emission of

characteristic "secondary" (or fluorescent) X-rays from a

material that has been excited by being bombarded with high-

energy X-rays or gamma rays. The DELTA Professional by

OLYMPUS device (used in this experiment), use new X-act Count Technology.

3. RESULTS AND DISCUSSION

3.1 Surface Roughness Profiles

As per surface roughness profile for epoxy

composite coating (EPX) and nano-epoxy composite

coatings (EZn, EZr, ESi and ENi) samples and compared to

the original corten steel sample (CS1), the average roughness

Ra shows high improve (Ra value decrease) at the low

intensity of nanoparticles at 2 % in coating mixture, as shown

in Figure 5, on other hand when the concentrations

percentages of nanoparticles increment the average

roughness Ra values. However, most Nano-epoxy composite

coating recorded good improvement of surface roughness.

Fig. 5. Comparison between original corten steel (CS1) and nano-epoxy composite coating according to the average roughness Ra values.

00.5

11.5

22.5

33.5

4

CS1

EPX

ENi2

ENi4

ENi6

ENi8

ESi2

ESi4

ESi6

ESi8

EZn

2

EZn

4

EZn

6

EZn

8

EZr2

EZr4

EZr6

EZr8

Ave

rage

Ro

ugh

nes

s R

a (u

m)

Nano-epoxy composite coating samples

Comparison of Ra value between original corten steel with Nano-epoxy composite coating

https://en.wikipedia.org/wiki/X-rays

https://en.wikipedia.org/wiki/Gamma_rays



Moreover, the normalized values of average roughness Ra for

epoxy and nano-epoxy composite coatings to original corten

steel (CS1) as shown in Figure 6. Its show the improvement

of Nano-epoxy composite coatings, ESi2 introduces 89 % of

improvement in surface roughness, EZn2 and ENi2 also

introduce 85% of improvement. The other recorded

improvement form 30 % to 80 %.

Fig. 6. Comparison of normalized values.

3.2 X-ray Fluorescence (XRF) result

XRF, is an effective way and widely used to analyze the characterization of materials. In the following the XRF result

for epoxy composite coating (EPX) and Nano-epoxy

composite coatings (EZn, EZr, ESi and ENi) samples

compared to the original Corten steel sample (CS1) and the corroded sample, which shows the elements of all samples.

Fig. 7. XRF analysis device during taking reading of corroded sample

Comparing the obtained results for XRF corroded sample

against the original corten steel sample (CS1), as shown in

Table II. It shows a reduction of Iron (Fe) element around 4

% and shows some Sulphur, this cause due to corrosion in the

internal surface of flue gas duct.

-100

-80

-60

-40

-20

0

20

40

60

80

100

EPX

ENi2

ENi4

ENi6

ENi8

ESi2

ESi4

ESi6

ESi8

EZn

2

EZn

4

EZn

6

EZn

8

EZr2

EZr4

EZr6

EZr8

Surf

ace

Ro

ugh

nes

s Im

po

rovm

net

, (%

)

Samples

Normlaized Value



Table II

XFR result of the corroded and the original corten steel samples (CS1)

Corroded Sample Original Corten Steel Sample (CS1)

ELEMENT % ELEMENT %

Fe 94.74 Fe 98.79

S 1.67 Mn 0.96

Mn 1.08 P 0.115

Ni 1.02 Nb 0.026

P 0.27

V 0.18

Cr 0.13

The XRF obtained result of original corten steel

sample (CS1), shows a high concentration percentage of Fe

element and less than 2 % from Mn, P and Nb elements, as

shown in Table II. Furthermore, as shown in Table III, the

XRF result for epoxy composite coating sample (EPX), it

shows reduction of the Fe element to 70 % with new elements

such as, Ti with 21%, Co and Zr by less than 5%, this avails

the effectiveness of the epoxy composite coating which

makes a barrier between corten steel surface and surrounding

atmosphere.

Table III

XRF result of CS1 and EPX samples

CS1 EPX

ELEMENT % ELEMENT %

Fe 98.79 Fe 70.35

Mn 0.96 Ti 21.63

P 0.115 Co 3.87

Nb 0.026 Zr 1.51

P 0.52

Mn 0.49

S 0.38

V 0.33

Table IV shows the XRF results for the nano-epoxy

composite coatings (EZn), with four different concentration

percentages 2, 4, 6 and 8 % from ZnO to epoxy. On EZn2

(ZnO nanoparticles is 2 %) sample, the results identify that

45 % form Zn and show 14 % of Ti, the existing of zinc and

titanium will improving of the coating corrosion properties

and reduction of the iron element, it means that the coating

is making barrier layer on the Corten steel surface.

Furthermore, the EZn4 shows a high concentration

percentage of iron with 68 % and reduction of zinc to 25 %

and titanium to 4 %. For EZn6, the results show an increase

in the concentration of zinc to 52 % and reduction in the iron

to 36 %, with improving of titanium compared to EZn4 to 7

%. EZn8, shows an increase in the iron concentration to 67

% and reduction of zinc concentration to 27 % compared to

EZn6.

Table IV

XRF result of the EZn samples

EZn2 EZn4 EZn6 EZn8

ELEMENT % ELEMENT % ELEMENT % ELEMENT %

Zn 45.59 Fe 68.08 Zn 52.62 Fe 67.05 Fe 35.6 Zn 25.07 Fe 36.94 Zn 27.93

Ti 14.35 Ti 4.53 Ti 7.84 Ti 3.15

Co 1.79 Co 1.01 Co 1.09 Co 0.62

Zr 1.13 Mn 0.65 Zr 0.49 Mn 0.68

P 0.49 P 0.24 Mn 0.31 P 0.2

Mn 0.26 Zr 0.2 P 0.25 Zr 0.113

Nb 0.04 Nb 0.073 Nb 0.036



As shown in Table V, the XRF test results for the

nano-epoxy composite coating (EZr), with four different

percentages 2, 4, 6 and 8 % from ZrO2 to epoxy. EZr2, EZr4,

EZr6 and EZr8 show high concentration around 90 % of iron,

from 3 % to 7 % of Zr and 3 % of titanium.

Table V

XRF result XRF of the EZr samples

EZr2 EZr4 EZr6 EZr8


Fe 90.43 Fe 93.74 Fe 86.21 Fe 88.05

Zr 3.51 Zr 2.22 Zr 7.55 Zr 6.65

Ti 3.44 Ti 1.83 Ti 3.66 Ti 2.71

Co 1.06 Mn 0.9 Co 1.11 Co 1.12

Mn 0.82 Co 0.77 Mn 0.82 Mn 0.79

Hf 0.23 Hf 0.17 Cu 0.23 P 0.21

P 0.23 P 0.15 P 0.21 Cu 0.14

Nb 0.046 Nb 0.003 Nb 0.042 S 0.13

As shown in Table VI, the XRF result of the nano-

epoxy composite coating (ESi), with four different

percentages 2, 4, 6 and 8 % from SiO2 against epoxy. ESi2, show 76 % of iron and 15 % of titanium. Comparing ESi4 to

ESi2, the results show an increase in the concentration of iron

and decreasing in the concentration of titanium. ESi6 and

ESi8 show increasing of titanium 18 % and 28 %

respectively, as increase of concentration of SiO2 in nano-epoxy composite coating.

Table VI

XRF result of the ESi samples

ESi2 ESi4 ESi6 ESi8


Fe 76.08 Fe 91.38 Fe 71.62 Fe 59.56

Ti 15.51 Ti 5.16 Ti 18.71 Ti 28.22

Co 3.76 Co 1.74 Co 4.36 Co 4.62

Zr 1.53 Mn 0.69 Zr 2.07 Zr 3.44

P 0.7 Zr 0.39 P 0.78 P 1.04

Mn 0.57 P 0.24 S 0.66 S 0.68

S 0.49 Nb 0.087 Mn 0.51 Bi 0.57

Bi 0.28 Bi 0.32 Mn 0.42

As shown in Table VII, the XRF result for the nano-

epoxy composite coating (ENi), with four different

percentages 2, 4, 6 and 8 % from NiO against epoxy. ENi2,

show high concentration of Ni 44 % and 38 % of Ti with 7 %

of iron, as known from Nickel is slowly oxidized by air at

room temperature and is considered corrosion resistance. The

result shows improving of corrosion resistance and strength.

ENi4 and ENi6, show good intensity of Ni 32 and 23 %,

respectively, but it shows increase of iron concentration

comparing to ENi2. ENi8, show high Ni percentage 68 %,

but low Ti concentration 8 %.

https://en.wikipedia.org/wiki/Oxidation



Table VII

XRF result of ENi samples

ENi2 ENi4 ENi6 ENi8


Ni 44.56 Fe 57.64 Fe 71.63 Ni 68.26

Ti 38.95 Ni 32.66 Ni 23.68 Fe 19.26

Fe 7.31 Ti 6.54 Ti 2.78 Ti 8.88

Zr 3.9 Co 1.46 Co 0.76 Co 1.42

Co 1.47 Mn 0.63 Mn 0.73 Zr 0.76

P 0.79 Zr 0.39 P 0.14 Mn 0.55

Bi 0.7 P 0.23 Zr 0.1 P 0.32

S 0.7 Nb 0.079 Nb 0.04 Bi 0.13

3.3 X-ray diffraction analysis (XRD) Results

The following XRD pattern shows the homogeneous of the

nano-epoxy composite coating. As shown in the Figure 8

and 9, which clarifies the XRD pattern of the original

Corten steel and epoxy composite coating (EPX).

Fig. 8. XRD pattern of CS1 sample

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7000

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10000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Inte

nsi

ty (

cps)

2 theta (deg.)

XRD Pattern of CS1 Sample



Fig. 9. XRD pattern of EPX sample

The following XRD pattern shows the homogeneous of the

nano-epoxy composite coating. As shown in the Figure 10,

11, 12 and 13, which clarifies the XRD pattern of the nano-

epoxy composite coatings (EZn, EZr, ESi and ENi).

Fig. 10. XRD pattern of EZn samples

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4000

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6000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Inte

nsi

ty (

cps)

2 theta (deg.)

XRD Pattern of EPX Sample

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8000

9000

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11000

12000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Inte

nsi

ty (

cps)

2 theta (deg.)

XRD Pattern of EZn Samples

EZn2 EZn4 EZn6 EZn8



Fig. 11. XRD pattern of EZr samples

Fig. 12. XRD pattern of ESi samples

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25000

30000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

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nsi

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cps)

2 theta (deg.)

XRD Pattern of EZr Samples

EZr2 EZr4 EZr6 EZr8

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0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Inte

nsi

ty (

cps)

2 theta (deg.)

XRD Pattern of ESi Samples

ESi2 ESi4 ESi6 ESi8



Fig. 13. XRD pattern of ENi samples

4. CONCLUSION

Four types of Nano-Epoxy composite coatings were

successfully prepared on Corten steel. These nano-epoxy composite coatings show significant improvements in

corrosion resistance obtained by measuring the surface

roughness and the XRF test, which have been conducted in

order to investigate the surface compositions for several

coating layers. According to the above mentioned test results.

It has been revealed that the surface roughness profile at 2%

concentration shows a dramatic improvements in the all four

types of nano-epoxy composite coatings (EZn, EZr, ESi and

ENi), which is equivalent to 0.28 µm for EZn2, 0.91 µm for

EZR2, 0.2 µm for ESi2 and 0.28 µm for ENi2, Compared to

the original Corten steel (1.96 µm). From improvement

percentage perspectives, around 85% improvement in the

surface roughness in EZn2, 53% in EZr2, 89% in ESi2 and

85% in ENi2. On the other hand, increasing the Nanoparticles

intensity in the composite coating will result in increasing the

surface roughness and vice-versa.

In terms of the XRF and XRD, it has been proved

that the coating layer creates a barrier layer which reduced

the Fe intensity in the complete martial (Corten Steel)

composition, which means insulating the steel from being

exposed to the surrounding atmosphere, hence resulting in prolonging the material life span and reducing the corrosion

as well. From the test results, adding the Nanoparticles to the

composite coating resulted in increasing the intensity

percentage of the Zn, Ni and Ti in the overall material

composition e.g. in ENi2, the Ni intensity percentage

increased to 44% and Ti to 38 % compared to zero% in the

original Corten steel. These increase in those valuable

minerals will improve the resistance to the corrosion and will

strengthen the coating layer.

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Eds. Springer, 2006, pp. 1–31.

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12000

14000

16000

18000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

Inte

nsi

ty (

cps)

2 theta (deg.)

XRD Pattern of ENi Samples

ENi2 ENi4 ENi6 ENi8

failure analysis of flue gas duct in a steam power...

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