Construction Details of Urea Reactor UR211 Presented By

Construction Details of Urea Reactor (UR-211) Presented By : Imran Khan Apprentice Engineer P. No. 20320 Batch # 14

Objective � Multi-layered vessel fabrication � Welding and fabrication techniques � Modifications in Reactor � Stamicarbon Urea Synthesis Process

Outlines � � � Urea Synthesis Process Specifications of Urea Reactor (UR-211) Mechanical Construction Shell Leak Detection System Hemispherical Heads Sieve Trays Top Cover & Nozzles Insulation Installation of Siphon Jet Pump Current Status Stamicarbon Inspection Lining Repair Job

Urea Synthesis Process Urea is produced from carbon dioxide and ammonia and composed of two chemical reversible reactions 1) 2 NH 3 + CO 2 2) NH 4 COONH 2 (-28. 4 Kcal/ Mole) NH 2 CONH 2 + H 2 O (+5. 97 Kcal/ Mole) The first reaction is fast and takes place in very short period of time, whereas second reaction is relatively slow and requires longer time

Off Gases to Vent thru UC-291 4 kg/cm 2 Absorber Reactor HPCC UH UR-211 -241 Scrubber UH-221 Carbamate Solution from UP-271 HV-221. 09 Gas HV-231. 02 UJ-221 Ejector Liquid 34% Urea Solution Stripper NH 3 from HP-Pump (UP 211) UH-231 CO 2 In from CO 2 Compressor HV-231. 07 HV-221. 10 LV-231. 04 Urea Solution 54% to LP Section

Specifications of Urea Reactor (UR-211) � Internally lined/overlayed multilayered vertical vessel with sieve trays & overflow pipe as internals. � Fabricated by M/s. Nooter Corporation USA in year 1997 -98. � Process Design � Codes & Standards

Construction Details • Reactor Shell • Hemispherical Heads • Inlet Nozzles • Reactor Overflow R 8 R 7 RR 66 R 55 R • Sieve Trays • Top cover & Outlet Nozzles RR 44 • Insulation • Modifications • Siphon jet pump Installation R 3 R 2 • Provision of Manholes in Trays R 1 R 2

Shell Can 3 Plates per Wrap, Total 39 Wrap Plates (13 Nos. ) Plates per Shell Can Width = 3042 mm , Length= 3669 mm Thickness = 7. 94 mm Material = SA-724 Gr. B Liner (01 Nos. ) Core Plate (01 Nos. ) Width = 3669 mm , Length = 9242 mm Thickness = 19. 1 mm Material = SA-724 Gr. B

Reactor Shell � Core Plate � Machining of Leak detection grooves and barrier layer faces � Weld seam barrier layer is overlayed on pre-machined faces by using 310 Mo. L (25: 22: 2) through plasma arc welding (PAW) on inside of core plate � Longitudinal welding : SMAW with E- 9018 -D 1 as filler rod Groove for Barrier layer faces 3669 mm 9242 mm 19 mm Leak Detection Grooves(3× 5 mm)

Welding of Wrap Plates � Drilling of vent holes prior to welding for venting of welding gases � Qty : 04 (Both ends of each Shell Can ) � Dia. : 9. 5 mm up to core plate in first 3 wrap plates and 19. 5 in the remaining 10 Nos. of plates � At 90 degrees apart radially drilled in wrap plates � Longitudinal seams : SMAW process � Electrode : E-9018 -D 1

Liner Welding � 04 plates are rolled, welded and inserted in each shell can - 03 longitudinal butt welding of rolled plates - Final Liner weld seam after insertion in shell can - Welding technique : PAW (Plasma Arc Welding)

Shell Cans Welding � Both ends of each Shell Can are build-up using SMAW and E-9018 -D 1 as Electrode for integrating core and all wrap plates � Circumferential welding joint � : Root pass (at core plate ) � 02 barrier layers welded by using plasma arc welding with 310 Mo. L prior to final circumferential weld joint of the liner

Leak Groves & Liner Welding B A A B See Details

Hemispherical Heads Material : A-516 Gr-70 Plate thickness : 135 mm Process : Hot forging Thickness after forging : 119 mm Heat treatment : Normalizing (To relieve work hardening stresses) • After dimensional checks bevels were made on circumferential ends as per drawing (at 8˚).

Hemispherical Heads � Manhole and nozzles are fabricated and installed by full penetration welding � Manhole is welded by SMAW using E- 9018 D 1 as Electrode. � After this welding the inside surface of heads is strip overlayed by Plasma Arc Welding technique using 310 Mo. L as filler in 03 layers.

Head to Shell Weld Seam STD. 8⁰ U-Bevel 3 To 1 Taper Weld Build up Hemi. Head Core Plate 25 Min. Liner Plate 30 Head Overlay

SIEVE TRAYS Total No. of Sieve Trays : 10 EA Overflow Pipe No. of segments per tray : 06 EA Material : 316 L (BC 01) Thickness : 10 mm Clamping Nut Bolts : M 14 (25/22/2) # Tray No. of Holes Hole Dia. (mm) Pitch (mm 2) 1 1, 2, 3 1270 8 52 2 4, 5, 6 920 8 62 3 7, 8, 9, 10 570 8 79

Top Cover & Bolting Top cover Outside Diameter Thickness of Cover Material of Cover Top Cover Weight Number of Nozzles Overlay Number of Holes Gasket : : : : 1220 mm 331 mm A-266 class 2 2. 5 Tons One 6” and other is 3” 9. 5 mm (310 Mol , PAW) 16 (diameter: 96 mm) 804 mm I. D x 854 mm O. D (Serrated type with PTFE envelope, BC-03) Detail of bolting Number of bolts Size of bolts Length of Bolts Material of Bolts : : 16 each M-90 X 6 632 mm A-193 Grade B 7

Top Cover

Siphon Jet Pump Skirts � Reduction of HS steam consumption (25 -60 Kg/hr) in stripper � Improvement in urea conversion � Improvement in gas-liquid mixing � Improvement in equal temperature distribution throughout the reactor � Reduction in stagnant zones in reactor � Easy to install on conventional trays with minor modifications

Sieve Trays after Modification S. No Tray No. of Holes 1 1, 2 2 3 3 4 4 5, 6 5 7, 8, 6 9, 10 Hole Dia. (mm) Pitch (mm 2) No. of Holes after Modification 730 1270 920 52 8 600 62 480 400 570 79 345

Siphon Jet Pump Skirts SIPHON SKIRT GUIDE RING OVERFLOW PIPE EXISTING SIEVE TRAY MANHOLES

Installation Details 900 mm Siphon Skirt 08 Segments 500 mm Guide Ring

Siphon Jet Pump Skirts

Inspection History of UR-211 � TA-2000 &TA-2001 : � Jointly executed by FFBL & Stamicarbon � Revealed no major abnormality � UT of Liner revealed a corrosion rate of about 0. 05 mm/yr. � TA-2004 � Siphon jet skirts were installed � Minor repair of pinholes defects was carried out using pencil grinder � TA-2006 � Minor repairs were carried out as previously � But increase corrosion rate of liner observed as compared to previous years � TA-2007 � To confirm the thickness monitoring results achieved during TA-2006 � Increase in corrosion rate i. e. 0. 15 mm/yr and 0. 213 mm/yr � Minimum thickness of 7. 41 mm at top compartment

Inspection History of UR-211 � TA-2009 � Inspection and Eddy Current thickness measurement by Stamicarbon � SIIC cracks found by Eddy Current testing just below the top head to shell circumferential weld � Surface was ground smooth using pencil grinder. DPT revealed cracking and subsequent grinding indicated the ~4 mm deep crack � Liner Thickness Measurement: Compartment 1997 2009 (mm) Average(mm) Min. Max. Avg. Corrosion Rate (mm/yr) 1 (Top) 8. 61 7. 6 7. 35 0. 15 5 (Middle) 8. 67 7. 5 8. 2 7. 78 0. 11 10 (Bottom) 8. 67 8. 2 8. 5 8. 38 1. 04

Inspection History of UR-211 �Stamicarbon TA-09 Inspection Recommendations: � Partial Relining of the top compartment within 1 -2 years � Lower the liquid level in the reactor up to ½ meter below the top circumferential weld seam � Improve insulation gas phase area in top � Next inspection after 4 years effective on-stream time � But, relining to be checked after 1 year

THANK YOU Questions-Answers

Shell Liner � Plates are hot rolled, solution annealed and pickled. � dimensions � Length � � : 3680 mm Width : 2292 mm (radius) Thickness : 8. 4 mm Quantity : 04 plates per shell can (total 32 plates in 08 shell cans) Material : SS-316 LN (Stamicarbon BC. 01) BACK

Liner long Weld seam Section A-A Core Plate 38 mm 16 mm Leak detection Grooves 5 mm 5 mm 30⁰ Liner PAW Weld seam barrier layer overlaid on pre-machined faces (PAW). 60 ⁰ 8 Min. Gap

Liner long Weld seam BACK

Circumferential Weld seam 152 mm 4 Nos. Vent Holes located 90 apart thru each end of each Shell Can ½’’-3000# Half coupling 128. 5 mm Wrap Plates 30 3 mm Core Plate 19. 05 mm Liner 8. 4 mm

Liner Circumferential Weld Seam BACK

Leak Groove and Hole ¾ ’’ SCH-160 Pipe SS-316 L Circ. Leak Groove ½’’-NPT with SS Plug 10 mm Leak Groove Long. Leak Groove BACK

Strain Induced Integranular Cracking (SIIC) �SIIC is an electrochemical corrosion mechanism in combination with deformation (strain). The following conditions are a pre-requisite for occurrence of these cracks : � The presence of an electrolyte as a result of condensation of ammonium carbamate in the gas phase or liquid phase. If the liquid level is extremely high, such cracks are also observed in the liquid phase because an electrolyte is always present. � Plastic deformation (=strain) of the liner material. Plastic deformation of the liner plates will always occur during start up of the plant (heating the synthesis section with steam). � Other conditions can enhance this failure mode, such as : � � inferior liner material and/or weld quality ; presence of chloride and/or sulphur in the porous oxide layer ; an increased gap between the liner plates and the shell ; and large number of pressure cycles (start/stops). BACK

SIIC-(Grinding using Pencil grinder) BACK

Chemical Compositions Material C (max) Cr Ni Mo Si Mn N 304 L 0. 03 18 -20 8 -12 --- 0. 75 2 0. 10 304 L U. G (BB) 0. 03 17 -20 8 -12 --- 1 2 0. 22 316 L 0. 03 16 -18 10 -14 2 -3 0. 75 2 0. 10 316 L U. G (BC. 01) 0. 03 17 -18. 5 13 -15 2. 2 -3 1 2 0. 22 X 2 Cr. Ni. Mo 25 22 2 (BC. 05) 0. 02 24. 525. 5 21 -23 1. 9 -2. 3 0. 40 2 0. 1 -0. 16 Safurex (BE. 06) 0. 03 28 -30 5. 8 -7. 5 1. 5 -2. 6 0. 5 0. 8 -1. 5 0. 3 -0. 4 BACK

Mechanical Properties Material C. Steel Yield strength (Mpa) 20 /225 C 248 / 202 Tensile strength (Mpa) 20 /225 C Elongation (%) 20 /225 C Thermal Expansion * 10 -6/ C 20 /225 C Module of Elasticity N/mm 2 at 20 /225 482 / 482 >16 12. 5 / 12. 5 190 BC. 01 190 / 135 490 / 412 > 40 16. 5 / 16. 5 184 BC. 05 270 / 195 580 / 495 > 30 16. 5 / 16. 5 184 800 / 717 > 25 11. 5 / 11. 5 184 Safurex 650 / 465 BACK

Safurex • Corrosion Resistance • Low overall cost • Low weight BACK

Plasma Arc Welding (PAW) §Plasma • . arc welding (PAW) is a advanced version of the gas tungsten arc welding (GTAW). §GTAW has a free-burning arc, which is unstable and tends to wander in the low current range. With increase in current, the arc power increases and the arc diameter also increases. This leads to a lack of concentrated power in the workpiece, which results in a bigger seam and a larger heataffected zone. §Unlike GTAW-welding torches, PAW uses a constricting nozzle and employs two separate gas flows, which give rise to a concentrated plasma arc having a narrow columnar shape. §The plasma column is now stabilized along the axis of the electrode and is more intense than the GTAW-welding arc. § The column temperature in PAW is 10, 000 -24, 000 K as compared to 8, 000 -18, 000 K in case of GTAW BACK

Process Design Type of Reactor : Plug Flow Reactor Density of Inlet Liquid : 990 -1130 Kg/m 3 Density of Inlet Gas : 114. 7 -126 Kg/m 3 Operating Temperature : 170. 2º C at inlet & 183º C at outlet Flow Rate of Inlet Gas : 198 m 3/hr Flow Rate of Inlet Liquid : 219 m 3/hr Reactor Hold up Volume : 192 m 3 Residence Time : 60 minutes (at 100 % load) Inside Diameter of Reactor : 2917 mm Number of Sieve Trays : 10 Height of Reactor : 29100 mm

Codes& Standards Design Code : ASME Boiler & Pressure Vessel Code, Section VIII, Division-2. 1995 Design Pressure : 162 Kg/cm 2 (2304 psig) Design Temp : 190º C (374º F) Hydro test Pressure : 2880 psig Corrosion allowance : 1 mm Ext. on Head & Shell, 2 mm Int. & Lining Wind Loading : Per UBC 88, Wind Speed = 150 Km/hr, Exposure ‘C’ Radiography : 100 % all liner, Shell can and shell to head weld joints PWHT : Heads only

Leak Detection System • 8 Nos. of Inlet air lines • Leak Detection Grooves • Ammonia Analyzer

HP Urea Synthesis Loop

M 90 Studs Construction Details (16 nos) � Reactor Shell Multilayer Shell Can, R 8 � Hemispherical Heads (Typical) 3670 mm (Typical) R 7 � Sieve Trays R 6 � Reactor Overflow R 5 � Inlet / Outlet Nozzles R 4 � Modifications � Siphon Jet Pump Installation � Provision of Manholes in Trays Top Hemispherical Head Sieve Trays (10 Nos. ) Overflow Pipe R 3 R 2 R 1 Bottom Hemispherical Head 34% Urea Liquid Inlet Gas Inlet