HRSG - Basic Understanding

GE Energy

HRSG – 101 TPSE – Dave Rogers, Wulang Chriswindarto

Date

What, Where, Why…?

What is an HRSG? Heat Recovery Steam Generator Wikipedia – energy recovery heat exchanger that recovers heat from a hot gas stream. It produces steam that can be used in a process (cogeneration plant) or used to drive a steam turbine (combined cycle power plant)

It’s A Boiler…!!! 3 GE Internal - For internal distribution only.

HRSG – More Than Just A Box of Tubes Overview

Operational Challenges on Installed Based

Converts exhaust energy

BOP trips driven by HRSG accessories

from gas turbine into steam

25% of forced outage hrs

Enables plant efficiency from 38% to 58%

Drum level issues cause trips preventing fast starts

$20-$25MM Parts $8-$9 MM Ship

Tube cracks and failures

$10 MM Field Assembly

are costly … critical path during outages

Modular assembly

Upgrades to GT often require HRSG analysis … potential showstopper 4 GE Internal - For internal distribution only.

Differences: HRSG vs Fossil Boiler HRSG uses exhaust gas (e.g. gas turbine) as a heat source and typically does not required a dedicated firing system HRSG do not use fans (draft is from gas turbine exhaust) HRSG generates steam at multiple pressure levels to improve heat recovery efficiency Heat transfer is typically by convection rather than radiation HRSG do not use membrane water walls HRSG uses finned tubes to maximize heat transfer HRSG typically has lower height profile & smaller footprint

Fossil Boiler 5 GE Internal - For internal distribution only.

Basic Components Water/ Steam Side: - Economizer/ Pre-heater (gas to heated water) - Evaporator & Drum (gas to boiling water to steam)

Gas out

- Superheater (gas to dry steam)

Gas Side: Inlet Duct, Baffles, Structural Steel, Casing, Insulation & Liner, Stack

Gas in

Accessories: - Silencers (gas & steam side) - Stack Damper & Bypass Stack Damper - Supplemental Fire/ Duct Burner

Evaporator

- Feedwater Pump

Superheater

- CO Catalyst & SCR System

Economizer

- Valves & Instruments

6 GE Internal - For internal distribution only.

HP Drum

NOx & CO reduced 80%

Gas Out – 180 F

LP Steam Out – 540 F

HP & RH Steam Out – 1050 F

In and Out

Stack Height ~ 150 – 200’

Integral Deaerator

Height ~ 85’ IP Drum

3 Pressure Level Reheater HRSG

50’

Gas in - 1100 F NOx CO

20’

Feedwater – 100 F

HP Superheater Reheater Duct Burner

HP Evaporator

SCR / CO Catalyst

IP Economizer IP Evaporator IP Superheater

GE Internal - For internal distribution only.

LP Economizer LP Evaporator LP Economizer

Length- ~ 100’ 7

Why HRSG is important? 3. Steam Turbine (ST):

1. Gas Turbine (GT): Converts Fuel

Converts Steam to

to Electricity and Waste Heat

Electricity

*Combined Cycle: A combination of thermodynamic Gas (GT) Cycle and Steam (HRSG & ST) Cycle in an Electrical Generating Power Plant to gain higher power output and efficiency

2. HRSG: Converts Waste Heat to Steam HRSG is the critical link between gas turbine and steam turbine in a combined cycle power plant 8 GE Internal - For internal distribution only.

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Combined Cycle T-S Diagram Combined Brayton and Rankin Cycle Heat Source

T

N EXPANSIO

COMPRESSI

ON

GAS TURBINE TOPPING CYCLE HRSG

STACK

N EXPANSIO

TEMPERATURE

COMBUSTION

BOTTOMING CYCLE CONDENSER Heat Sink

ENTROPY

S 5/

11 GE Internal - For internal distribution only.

Typical Energy Utilization Chart GT POWER (35.8%)

HRSG CASING LOSSES (0.5%)

ST LOSSES (1% ACCESORIES)

FUEL (100%) to Gas Turbine

EXHAUST HEAT (62.4%) to HRSG

GT LOSSES (1.8% ACCESORIES)

STEAM TURBINE (54.8%)

STACK LOSS (7.1%)

ST POWER (20.9%)

CONDENSER (32.9%)

Combined Cycles Systems (with HRSG & ST) Utilize More Fuel Energy to Produce Useful Work Than GT Alone 12 GE Internal - For internal distribution only.

Design Philosophy

HRSG Design Philosophy Pinch

Temperature

Approach

Tur Super Heater

bin

e Ex

hau st

HRSG design is a precise balance of the utilization of exhaust energy to produce steam energy in an economic way

Gas

Evaporator Economizer

Heat Duty Pinch Point The Difference Between Gas Temperature and Saturation Temperature at the Outlet of the Generating Bank Approach Temperature The Difference Between Economizer Discharge Temperature and Saturation Temperature

SH

EVAP ECON

The smaller the pinch and approach temperatures, the more efficient the HRSG, but also the more expensive the design 14 GE Internal - For internal distribution only.

HRSG Pinch Point Plot Steam and Water HP

Temperature °F°F Temperature

1200

/ Reheat

IP LP

800 400 0 0%

20%

40%

60%

Percent Exhaust Energy Used Percent Exhaust Energy Used GE Internal - For internal distribution only.

80% 15

HRSG Types

HRSG Types Horizontal

Vertical

Once Through

• Horizontal gas flow direction

• Vertical gas flow direction

• Vertical tubes arrangement

• Horizontal tubes arrangement

• Either horizontal or vertical gas flow direction & tubes arrangement

• Majority installed

• Smaller footprint (historically common in Europe or outside US)

• Once Through eliminates the need of drum • Phase change from water to steam is free to move throughout the bundle • Theoretically more agile

17 GE Internal - For internal distribution only.

Product Features

Product Features

Finned Tubes

Internal insulation & Liner

Drum & Internals

Prevent heat losses, Provide outside casing temp of ~80 F

Is separated to produce dry steam

Steam & water mixture

Act as heat transfer/ exchanger medium Fins increase surface areas

Gas Baffles To Prevent Gas bypassing the heat exchanger

Duct Burner Supplemental firing to increase heat input for peak load Gas dP 0.25” w.c expected

SCR Systems

Burner Skid & Elements/ Runners

NOx reduction by ~ 86%

BMS-Burner Management System Flame Scanner

Gas dP 2-3” wc expected

Ignitor

Skid, Ammonia Based, Injection Grid, Catalyst

CO catalyst CO reduction by ~ 80% Gas dP ~ 1” wc expected

19 GE Internal - For internal distribution only.

Manufacturing

Manufacturing – Heat Transfer Section Headers

Bare Tubes

Bare TuinSlit Fin Coil Coil Slit

Harps Assembly

ERW

Finned Tubes to header weld

Finned Tubes

Finned Tubes to header fit up

21 GE Internal - For internal distribution only.

Manufacturing – Casing, Insulation & Liner

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Manufacturing - Drums

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Field Assembly

HRSG – Typical Field Assembly

PLACE PO 1 - 2 Months

OBTAIN MATERIALS 2 - 3 Months

MANUFACTURE 7 - 9 Months

SHIP COMPONENTS 3 - 4 Months ASSEMBLY 7 - 9 Months

COMMISSION 1 - 2 Months

Total Cycle Duration: 21 - 29 M onths

25 GE Internal - For internal distribution only.

HRSG- Degree of Shop Modularization

1. Harps

3. C-Frame

2. Modular

4. Full Assembly 26 GE Internal - For internal distribution only.

HRSG Life Cycle Issues & Opportunities

HRSG issues

Light and Heavy Ammonium Bisulfate Deposits

Considerations for Cycling Operation Component fatigue damage

GT Exhaust Non Uniform Flow

Chemistry control Attemperation Drum level control Sulfur dew point corrosion

Critical Components affected by Cycling HP Drum HP Superheaters RH Superheaters

Factors that impact fatigue damage GT Ramp Rates Pressure Management Heat retention during offline periods HRSG design & construction Flow Accelerated Corrosion (FAC) 28 GE Internal - For internal distribution only.

GE technologies applicable to HRSG

Metallurgy & coatings Creep, oxidation Thermal barrier Anticorrosion

Sensing and inspection Pulse eddy current, bore scope, high temp ultrasound, digital radiography etc.

Aeromechanics/CFD Bent fin tube CFD modeling

Performance improvement Gatecycle, eMap Acoustic cleaning

Life models Physics based & empirical lifing models

M&D Technology Water chemistry Remote M&D Monitoring, chemicals, 24/7 monitoring chemistry models, laboratory failure analysis etc. 29

GE Internal - For internal distribution only.

Thank you.

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