TITANIUM EROSION IN UREA STRIPPERS & EMERGING

TECHNOLOGIES

Fauji Fertilizer company Limited

Ali Abrar

Unit Manager InspectionAreas of expertise reliability, Integrity, Inspection

Titanium Urea Stripper

Urea Stripper Function

The urea stripper strips out vapors (In the form of Ammonia and Carbon dioxide) from the urea solution.

PRC-13V

MC

MS

STRIPPER

Solution in

Vapors out

Solution out

Steam in

Construction

Pressure Retaining shell Carbon steel

Corrosion resistant material Titanium

Tubes and inside clad material is Titanium

Internals 25CR-22Ni-2Mo

TUBE

FERRULE

Solution film formation inside tube

TUBE SHEET

Vapors stripping

TANGENTIAL HOLES

Erosion in Titanium Strippers

Erosion of cladding

Groove formation at ferrule end

Tube thickness reduction below top tube sheet

Solution inlet liner erosion

Cladding thickness loss

More area erodes against solution inlet

nozzleMaximum erosion rate expected =0.25 mm/yr

Repaired pits

Mock up

Erosion of tubes at top tube sheet

• Tube Edge Erosion (A)• Old Groove (B)• New Groove formation (C)• Thickness below new groove (D)• Thickness below top tube sheet (E)

Year min max Avg min max AvgGM 2003 3.07 3.97 3.56 - - -Donagani 2006 2.95 3.90 3.53 0 0.19 0.01

B Force 2005 2.51 3.38 2.89 0.05 0.63 0.33

C Donagani 2006 2.10 3.95 2.95 0 1.17 0.51

D Donagani 2006 2.75 3.75 3.17 0 0.24 0.13

Donagani 2003 2.42 3.96 3.40 0 0.33 0.10Force 2005 2.17 3.69 2.87 0 - 0.26Donagani 2006 2.15 3.95 2.91 0 0.45 0.16

a Avg 0.163b Max Value >2XAvg 0.327c Compensation 0.06/EC 0.120

Max Expected value (b+c) 0.447

B

C

D

Year min max Avg min max Avg

a Avg 0.163b Max Value >2XAvg 0.327c Compensation 0.06/EC 0.120

Max Expected value (b+c) 0.447

A

B

C

D

A

CD

E

B

Erosion of tubes at top tube sheet

Erosion of the tube is visible at the top edge and inside due to solution by passing

Grooves are visible inside the tubes

Cutaway section of a tube, groove is visible.

Erosion of tubes at top tube sheetB

C

R21T8 R21T6R21T7

EC signals of grooves.

EC thickness profile of a tube

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1011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465

E-101 TOP TUBE SHEET LAYOUT

Count FROM TO9 0 2.45

29 2.46 2.5103 2.51 2.6370 2.61 2.7676 2.71 2.8

1589 2.81 3.972776

EC data of tubes thickness

Tubes thickness reduction trends

Urea stripper refurbishment procedure

Urea stripper refurbishment activities

Urea stripper refurbishment activities

Installation of rehabilitated stripper

Experience of refurbished stripper

High rate of erosion at the end of ferrule adaptors in the tubes.

Old groove

New groove

Advancement of adaptor to cover

eroded part of the tubes

New Technology Development

Pure Zr and Ti-Zr tubes being installed in TA-2005

Extrusion bonded Titanium tube with Zirconium

Extrusion bonded Inertia welded tube

Condition of Zr & Ti-Zr and friction welded Tubes (after one year of operational testing)

Zr tube joined with Coaxial (Ti-Zr) tube with friction weld. The mockup was installed at the bottom

of stripper.

Two sample tubes were installed in TA-2005; Pure Zr and the other Co-axial Ti-

Zr tube. The results were found satisfactory in TA-2006. However there are reservations on quality of welds for pure Zr tubes in Titanium strippers for

new equipment.

Pure Zr tubeTi-Zr Coaxial tube