Indigenization of Russian Make WHR by Vizag Steel

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Indigenisation of Russian Make Waste Heat Boilers System

Our Experience

1. Salim G Purushothaman, AGM, Vizag Steel

2. B. Ravishankar, Manager, Vizag Steel

3. Jeevan Kumar, Assistant Manager, Vizag Steel

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Waste Heat

Heat Evolved from Dry Quenching of Metallurgical Coke Produced In House

Quenching Medium – Circulating Nitrogen

Before Recovery - 800 Deg C

After Recovery - 160 Deg C

9 x 80,000 N Cu M/Hr

TOTAL Net HEAT AVAILABILITY = 124 G Cal/Hr

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Metallurgical Coke

Required for Smelting Iron Ore in Blast Furnace

Each Ton of Hot Metal Produced needs Half Ton Coke

We make Aprox 8500 Tons a Day

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COKE MAKING

Destructive Distillation of Low Ash Coal

- Heating Coal in the absence of Air to 1100 Deg C

Thus expelling all volatiles

To obtain Porous Carbon Concentrate, COKE

Made in Coke Ovens

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Coke Ovens

Coal Charged

Part of A Battery – Coke Ovens

Coking Time /Oven - 16 Hours

1 Battery – 67 Ovens

Batteries - 4

Rated Production– 100Pushings/Day/Battery

1 Oven – 32 Ton Coal to 25 Tons Coke

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Our Coke Oven Battery

Total Such Batteries in VSP – 4 Numbers

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Coke Produced

Collected In Buckets, 1 Pushout = 25Tons Coke

Temperature = 1000 to 1100 Deg C

Nature - Incandescent

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Need to Quench Coke

Coke to be Shipped to Blast Furnace

Shipment through Conveyors

Temperatures above 180Degrees Burns Conveyor

For Safety of Conveyor and Handling

Coke to be Quenched to 160 Deg C

Implication:

350 M Cal Heat /Ton Coke to be Removed

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Types of Quenching

Cooling Water

Coke Car

1.WET Quenching

All Heat – Lost

Pollution - Severe

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Types of Quenching

2. DRY Quenching

All Heat –Recovered

Pollution- Eliminated

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DRY vs WET (Quenching)

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CDCP Blocks of VSP

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RUSSIAN BOILERS OF CDCP

• Commissioned in 1986-87

• Make: Belgorod Power , Russia (Erstwhile USSR)

• Model : KCTK 39/440

• Type : Drum, Forced Circulation

• Rating : 39 Bar, 440 Deg C , 25.5 TPH MCR

• Gas Flow Rate : 80 000 N CuM/Hr

• Hot Gas Inlet : 800 Deg C

• Cooled Gas Outlet : 160 Deg C

• Construction : Twin Shaft , Refractory walled , Counter Flow Eco, & Evap

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SIDE VIEW

To Drum

From

Circulation Pump

Output

SH

Steam,

39 Bar

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Problems Faced • Heavy Erosion – at Riser Tubes

-- at Evaporator side Bends

• Bi Metallic Corrosion – Bracket Area of Evap Top Bundle

• 2 Days Cooling Time for shutdown inspections

• No access to inspect Sides of Bundles

• Frequent damages to Refractory lining due to cyclic stresses, causing forced outages

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Gas Erosion • Evaporator Cross Section = 3.8 x 3.66 = 13.9 sqM

• Projected Area of Tubes =

100 Nos x 28mm x 3.6 M long = 10.1 sq M

NET FLOW AREA = 3.8 sq M

Gas Flow Rate = 80,000 NCuM/Hr

Gas Velocity = 80000/3.8/3600 = 5.85 m/Sec Dust Loading = 5-10 gm/N CuM of Gas

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RISER TUBES

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SIDE BENDS

SIDE WALL

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Erosion – of Evaporator side Bends

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Improvement Plan

• Immediate:

1. Baffled the Bends to protect them

2. Shielded the Riser tubes by providing Armour plate upstream

• Long Term:

1. Monitor Tube Thinning & Schedule for Phased Replacement

2. Indigenisation of tubes with Erosion Resistant Indian Makes

• Futuristic:

Future Boilers for Plant Expansion to have lesser gas

Velocity.

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SIDE BENDS

SIDE WALL

Side Baffles

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Trigger For Tube Replacement

• Annual Tube Thickness Survey with D Meter

• Monitoring of Thinning Trend with recorded D Meter Readings

• Forecasting Thinning Rate and Procurement of Spare Tubes

• Determined value of Residual thickness to replace Tubes as

- 1.9 to 2.0 mm for Straight Part

- 1.8 mm at Bends ( Based on IBR Regn 338)

Tubes = OD 28 mm , Seamless Original Thickness = 3mm Nominal with +0 , -10% Tolerance (GOST) Calculated Thickness for Working Pr of 47 Bar as per GOST = 0.64 mm Calculated Thickness for Working Pr of 47 Bar as per IBR = 1.31mm, But Required Minimum Thickness for Coil Tubes, For Forced Circulation and Tube OD < 29 mm = 1.62 mm (IBR Reg 338, b)

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Towards Indigenisation

• Evaporator Top Coils – 15 XM (GOST)

• Evaporator Other Coils – Steel 20 (GOST)

•Evaporator Service Conditions:

Water Temp – 270 Deg Max,

Pressure 47 Bar Max (Excess Condition)

MCR: Inlet 46 Bar, Outlet 43 Bar

Outside Temp – 800 Deg Max

Material Testing Done in our own Laboratory – QATD Dept of VSP

•Hardness

Brinnell Hardness value Varied

from 130 to 135 sample to

sample

ie Rockwell B (HRB) 72 to 75

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Material Selection

• Involved Plant Design Dept , & QATD Dept of VSP

• Consulted Dy Chief Inspector of Boilers , Visakhapatnam

• Furnished Sample tubes to BHEL

• Advice of Design Engineers from BHEL

Objectives # Medium Carbon Steel for Evaporator service ; C = 0.2 to 0.25 % range # Hardness to be around 80 HRB to be more resistant to Erosion # At the same time % Elongation to be minimum 27% - Bends to be safe in repeated Thermal Cycling (Bend R = 2D) # Economy

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Material Selection

• SA 192

SA 210 Gr A1

SA 210 Gr C

SA 213 T11

Selected SA 210 Gr A1- CDS

• Hardness > 75 HRB; CDS will have more due

to work hardening.

• % Elongation = 30% Better Flexibility for Bends

• Thickness : Always > 3mm (as Tol = +20%, - 0%)

• Easy Availability, Weldability

Considered

Plant Design Dept of VSP Developed Tender Drawings accordingly

for Procurement of Spares from Indian Market

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Bundle Replacement

• Thickness Reduction found reaching Threshold in

Two Boilers during Annual Thickness Survey

(Residual thickness, 2.2 mm against Normal 3 mm)

• Procurement Action Initiated . Planned to Replace next Year

Year : 2000

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Bundle Replacement

• Residual Thickness varied from 1.9 to 2.1- Time to Replace!

• Dy Chief Inspector of Boilers advised Evaporator Bundle Replacement

• Replacement Program was approved by DOB , Hyderabad

• First Indegeneous Coil Bundle Erected in one of the Boilers in 2001

Erosion Rate Drastically Reduced in that Boiler Ever since

Thereafter All Russian Boilers underwent Indigenisation of Coils

Including Economiser Coils

Over a 10 Year Period

Year : 2001

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New CDCP Boiler Installation

• 2002-03 Planning for Capacity Expansion involving new Coke Oven Battery

• Plan Entailed 4 More CDCP Boilers with similar Capacity

• Desired to have Design Gas Velocity as minimum as possible

• Thermax Pune Introduced the idea of Single Shaft CDCP Boilers – As Working in Vental Steel Plant,Russia - Designed by a Finnish

Corporation Rautaruukki

– Thermax offering such CDCP Boilers to Neelanchal Ispat, Orissa

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Rautaruukki Design • Retains the Elevation of Gas Entry Axis; Overall

Height increased • Water Wall with Natural Circulation and Evaporators

with Forced Circulation. • Overall Foot Print within Russian CDCP Boiler’s • Bigger Tubes • Bigger Pitches –Longitudinal & Transverse • Cross Section Area gets doubled almost but Projected

area of Coils is reduced by reduction in tubings ( HSA requirement curtailed by Water Wall).

• Marginal increase only in Overall HSA

CIRCULATING GAS VELOCITY REDUCTION OF 30 %

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New CDCP Boiler Installation • Thermax designed Single Shaft CDCP Boiler for NINL

• We inspected Thermax Boilers at NINL : During their Erection & Commissioning (Consultant MECON)

• Their Operation was found satisfactory

• Decided to Opt for Single Shaft Boilers; Made Specs accordingly , under Consultancy of MECON, & Tendered out.

• Thermal Systems, Hyderabad Bagged the Order (L-1) for Design ,Supply & Erection of Single Shaft CDCP Boilers.

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Thermal Systems Boiler

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Thermal Systems Boiler Cross Section Area = 5.2 M x 4.8 M = 24.96 sq M

Total Projected area for Coils and Hanger Tubes

(46 Tubes x 44.5mm x 5.2 M) + 15% =12.25 sq M

Net Flow Area = 24.96 – 12.25 = 12.71 sq M

Max Gas Velocity at MCR = 80000/12.71/3600

=1.75 m/Sec

Reduction in Velocity = (5.85-1.75)/5.85

=70.1% Reduction

4 Such Boilers in service since 2008 No Erosion Mark Reported yet

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Bi Metallic Corrosion

BRACKETS

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Bi Metallic Corrosion

Tube Material - Alloy Steel ( 15 XM) 1.5 Cr, 0.44 Mo

Clamp Material - Micro Alloy Steel

High apart in Electro chemical Series

During Service Period Coke Dust gets filled between pipe and clamp

During off Service period Coke Dust absorbs Moisture and turns

conductive

Electrolytic Corrosion starts, Anodising the Tube. Pittings formed

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Improvement Plan

• Immediate:

1. Stopped Water Washing

2. Placement of Silica Gel Bags inside Shaft during down period

• Long Term:

Specified Safe material for Clamp while ordering for indigeneous tubes

• Futuristic:

Future Boilers for Plant Expansion to have this angle considered during design phase .(Included in Specification)

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Reason: Thick Refractory Walls

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Refractory Walls

HEAT

Wall thickness = 410 mm

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Improvement Plan

• Frequent Damages: 1. Refractory Engg Dept of VSP selected better materials to resist Cyclical Changes 2. Improved Re inforcement with steel wire nets • Long Term: Planned Replacement of Refractory Lining in all Boilers

undergoing • Futuristic: Future Boilers for Plant Expansion not to have Refractory Walls

, but to have water walls instead

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Results of Indigenisation

• Russian Boilers: 1. Mitigating the Erosion Problem with Indigeneous Coils 2. Eliminated Bi Metallic Corrosion Altogether 3. Eliminated Refractory Damage related Outages 4. Sustained the OEM Norms of Output and Efficiency • Expansion Boilers: 1. Indigenised Sourcing. 2. Proven Freedom from all problems faced in Russian Boilers 3. Improved Energy Efficiency : 5 TPH extra steam production per Boiler with same Heat Input Rate 4. Improved Service Life ; Reliablitiy, Availability

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Our Enablers

Directors of Boilers, AP

Dy Chief Inspectors of Boilers, Visakhapatnam # Technical Guidance # Timely Advises # Boundless Co-Operation

We are indeed indebted to them………………………

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1. Salim G Purushothaman AGM, Thermal Power Plant 2. B Ravishankar

Manager, Thermal Power Plant 3. Jeevan Kumar

Asst. Manager, Thermal Power Plant

Engineering

Indigenization of Russian Make WHR by Vizag Steel