boiler controls & instrumentation k karthikeyan manager controls & instrumentation bhel,...

Boiler Controls & Instrumentation

K KarthikeyanManager

Controls & InstrumentationBHEL, Tiruchirappalli

Email : [email protected]

Bharat Heavy Electricals Limited - Tiruchirappalli

Boiler C&I

INTRODUCTION

PART I - BOILER

PART 2 - INSTRUMENTATION

PART 3 - CONTROLS



Boiler C&I

Boiler C&I -Functions


Boiler C&I

• Control systems engineering• Instrumentation engineering• Electrical systems engineering • New product development


Broad engineering activities


Boiler C&I

• Proposal Engineering• Contract Engineering• Product Engineering• Quality Assurance & Control• Field Engineering• Research & Development


Functions


Boiler C&I

Proposal Engineering



Boiler C&I

• Scope of Work• Project Estimate• Offer submission• Offer evaluation by

customer• Award of contract

Proposal EngineeringBoiler Controls & Instrumentation


Boiler C&I

• In summary, the purpose is to draw-up

- Scope of Work- Project Estimate

of the project.

Deliverables : - Estimable quantity(BOM)- main and spares- Datasheets- Descriptive offers of packages & - Preliminary design sketches(P&IDs, GA).


Proposal Engineering


Boiler C&I

• Arrived based on a broad specification prepared by the customer/consultant.

• Individual system scope identified gets recompiled into a project scope of work .

• Project scope document includes scope of work , terminal points & exclusions

Scope of Work



Boiler C&I

• The typical scope covered in Boiler C&I discipline include– Furnace safeguard Supervisory system– Secondary Air Damper control system– Soot blower control system– Boiler area field instruments – Associated cable & accessories.– Electricals(MCC, elevator etc.)

Scope of Work



Boiler C&I

Offer evaluation

• The offers get evaluated at the customer end.

• Customer awards the contract on a technically qualified bid with the lowest price.

• The award of contract is indicated by a ‘Letter of Intent’ received from the customer.



Boiler C&I

Award of contract

• The offers get evaluated at the customer end.

• Customer awards the contract on a technically qualified bid with the lowest price.

• The award of contract is indicated by a ‘Letter of Intent’ received from the customer.



Boiler C&I

Contract Engineering



Boiler C&I

Packages• SG integral C&I(Trichy)• Station C&I(PEM or customer)- in case of BTG

or Turnkey• SG integral electricals(Trichy)• Station Electricals(PEM or customer)- in case

of BTG or Turnkey



Boiler C&I


The role involves system level contract coordination for the boiler C&I area.

• Applicable PGMA List• Sub Delivery check list.• Boiler Contract Regular activity(BCR) schedule• ‘00’ PG list(erection documents).• Applicable O&M documents.


Boiler C&I

System Engg. Documents involved :• Piping&Instrumentation Diagrams(P&IDs)• Measurement & control recommendations• Automatic control schemes• Interlock & protection schemes



Boiler C&I

P & I Diagram- Air & flue gas (portion)


Boiler C&I

Instrument schedule steam & water (sample)


Boiler C&I


Boiler C&I

Product Engineering


Boiler C&I

Product Engineering

Detailed design of Boiler C&I products & systems

• Digital controls• Analog controls• Electrical systems & cables• Field instruments• Special instruments• Actuators

• Digital ControlsBurner management system.Soot Blower control system

• Analog Controls Secondary air damper control system.Auxiliary PRDS control system.

Product Engineering


Boiler C&I

• Electrical systemsControl supply panels

LT Motor control centresPower distribution panels

• Field instrumentsSwitches & gauges for Pressure,Level &

temperatureThermocouplesFlow elements

Product Engineering


Boiler C&I

• Flame scanner system• Acoustic steam leak detection system.• Electronic water level indicator.• Closed circuit television system.• Vibration monitoring system.• Flue gas analysers.• Steam and water analysers.

Product Engineering


Boiler C&I

Special instruments

• Electrical and C & I engineering design• Release of indents for C & I sub-delivery items.• Evaluation of technical offers for bought-out items• Technical Delivery Conditions (TDC)

Product Engineering


Boiler C&I

Quality Control & Assurance



Boiler C&I

The role involves preparation/review of following activity w.r.t C&I products & systems

• Prepare Standard Quality Plans (SQP)• Prepare Contract Quality Plans (CQP)• Review/Approve Vendor Quality Plans (VQP)• Issue Reference Quality Plans (RQP)• Prepare Inspection Check Lists (ICL)



Boiler C&I

• Performing inspection at vendor works for CI products & systems - bought-out items

• Review & dispose Site Action Requests on CI products & systems



Boiler C&I

Field Engineering


Boiler C&I

The role involves • Providing technical support / trouble shooting of

C&I products / system during - Erection & commissioning stage of project

- Operation after handing over to customer• Review & dispose Commissioning action requests• Review & dispose Contract closing pending issues• Visiting sites to ensure smooth progress of C&I site

activity

Field Engineering


Boiler C&I

Research & Development



Boiler C&I

• Microprocessor based Gravimetric coal feeder controls - BHELFEED

• Microcontroller based Flame moniotirng system - BHELSCAN

• Acoustic steam leak detection system – BHELSONIC

• Electronic water level Indicator system- BHELVISION

Research & Development


Boiler C&I

In-house developed C&I systems & products


Boiler C&I

Boiler Basics

BOILER CLASSIFICATION


Boiler C&I

BHEL BOILERS

• Power Boilers Up to 600 MW rating(Coal, oil and gas fired - Subcritical)Up to 800 MW - Supercritical

• Nuclear steam generators Up to 235 MW rating

• Industrial boilers Up to 450 Tonnes/hour rating Fertilisers, Petrochemical, Steel & Paper industries Wide range of fuels- Oil, Gas, BFG, Bagasse, Black liquor.


Boiler C&I


Boiler C&I

Schematic of a boiler

• Furnace & Circulation system• Superheaters• Reheaters• Economiser• Airheaters• Fans• Pulverisers• Raw coal feeders• Fuel firing system• Sootblowers


Boiler C&I

UTILITY BOILERS - ESSENTIAL COMPONENTS

• Natural circulation• Controlled circulation • Once through

Circulation ratio :

Mass rate of water fed to the steam generating tubes to the

mass rate of steam generated.

Natural circulation 6

Controlled circ 4

Once through 1

CIRCULATION SYSTEMS


Boiler C&I

BOILER CIRCULATION SYSTEMS


1. Axial

– Impulse type - IGV Control.

– Reaction type - Blade pitch Control.

2. Radial

Inlet damper control, Variable speed control;

Variable speed control by two speed motor,

Hydraulic coupling or Variable frequency drive.

Fans


Boiler C&I

Radial FanBharat Heavy Electricals Limited - Tiruchirappalli

Boiler C&I

Axial Reaction


Boiler C&I

- Flow proportional to Speed - Flow proportional to (Impeller Dia) 3

- Head proportional to (Speed) 2

- Head proportional to (Impeller Dia) 2

Hence Variation in speed alters the performance


RADIAL FANS - SPEED CONTROL

Boiler C&I

FANS IN BOILER - SCOPE

• Primary air fans - Dries & transports Pulverised coal

• Forced draft fans - Supplies Combustion air

• Induced draft fans - Sucks Flue gas out of furnace


Boiler C&I

MILL - GRINDS COAL

• Slow speed mills (Tube mills - 15 to 25 RPM)

• Medium speed mills (Bowl mill, Ball and race mill

etc.- 50 to 100 RPM)

• High speed mills (hammer mills directly coupled to

motor - 750 to 1000 RPM)


Boiler C&I

RAW COAL FEEDERS

• Volumetric - Rotary and drag link,

• Gravimetric – Endless belt type


Boiler C&I

Scope : CONVEY RAW COAL TO MILL

Types :

AIRHEATER

Heat recovery equipment

Extract heat from Flue gas to heat primary & secy. Air

• Regenerative type ( Rotating drive )

• Tubular type


Boiler C&I

Types :

SOOTBLOWERS

Remove ash & slag from pressure part tubes

Types

• Long retractable sootblowers - traverse & rotary motors

• Half retractable sootblowers- traverse & rotary motors

• Rotary blowers - rotary motor

• Wall blowers - traverse & rotary motors

• Furnace temperature probe - Used during boiler start up


Boiler C&I

Fuels : Coal Oil Gas

H/C ratio • Natural gas 0.3 Fuel oil 0.1 Coal 0.07

Calorific value (kcal/kg )• Gas 10000 Oil 8000 • Bituminous coal 3000-3500 Lignite 2500

Coal burning methods• "On grate" “In suspension" Fluidised bed

Three 'T's of combustion – Time – Temperature and – Turbulence.

FUELS & COMBUSTION


Boiler C&I

• Short period of time• High temperature & • Very turbulent flame .

FUELS & COMBUSTION

Rapid combustion

•Less turbulence and longer burning produces fewer nitrous oxide.

•In some cases combustion is delayed or staged intentionally to obtain fewer nitrous oxide or to obtain desired flame characteristics.

Boiler C&I


Boiler Instruments


Boiler C&I

Boiler measurements

• Pressure• Differential pressure• Temperature• Differential

temperature(heat flux)• Flow • Level• Vibration (rotating

device)• Speed (rotating

device)• Position• Weight

• Flue gas analysis(O2, CO, SOx, NOx, Opacity)

• SWAS(Conductivity, pH, Silica, DissilvedO2, Hydazine)

• Image sensing(CCTV)

• Sound(steam leak)

• Viscosity (fuel oil)

• Calorific value


Boiler C&I

First letter• P-Pressure• T-temperature• F- Flow• A- Analytical

Succeeding letters• A- Alarm• I- Indicate• R- Record• Q- Integrate• C- Control• S- Switch• T- tansmitter• E- Element• P- Pocket• W- Well


Boiler C&I

Instrumentation representation- ISA

Boiler Controls


Boiler C&I

Continuous control :

Objective

Enabling Automatic Operation.

Optimising operating performance.

On-Off control :

Objective

Supervise process operation for safety

Prevent process from entering unsafe condition.


Boiler C&I

BOILER CONTROLS

BOILER CONTROLS

• Auto control system

• Boiler Auxiliaries interlocks & protection system

• Furnace safeguard supervisory system (FSSS)


Boiler C&I


Boiler C&I

• Master demand

• Combustion and draft control

• Feed-water control

• Steam-temperature control

Auto control system.


Boiler C&I

Master demand

• 'Master demand' controls the boiler operation.

• Set from unit load demand or main steam header pressure control

• ‘Master demand’ sets burners firing at a rate required for steam

production and corresponding air flow demand

Objective :

Fuel is consumed at a rate that exactly matches the Steam demand.

Fuel is consumed safely, so that the energy is released without risk to plant, personnel or environment


Boiler C&I Combustion control

• Fuel flow control

• Air Flow Control

• Coal mill control


Boiler C&I Combustion control Air Fuel/Cross Limiting

AIR CONTROL

FT PT FT

A

A T

P I

A T

P I

A T

P I

f(x)

f(x)

Fuel FLOWSTEAMHEADER PRESSURE AIR FLOW

SP SP

LO SELECT HI SELECTFuel CONTROL

Fuel FeedAIR DAMPER

Air Feed

67

Mill uses primary air -

• For transporting coal from mill to furnace.

• To "dry" coal.

• Air flow to mill and mill outlet temperature are regulated using Hot air damper and cold air damper respectively


Boiler C&I

Mill air flow and temperature control

Feedwater control


Boiler C&I

Objective :

To supply enough water to the boiler to match the evaporation rate.

Water level in the drum indicates amount of water in boiler

Actual Steam Flow - Used to determine required feedwater during transient conditions when level may not be accurate.

Difference between Actual steam flow and Actual Feedwater Flow is added to the level error to form the ‘Feedwater demand’.

Feedwater demand drives the feed control station to adjust feedwater sa as to maintain the drum level to normal value.

Feedwater control


Boiler C&I

P R E S S U R EC OMP E N S AT IO N

f(x)

A

X

P T F T T E

f(x) f(x)

X

LT P T

f(x)

X

F T T E

f(x)

K

K

D

D

T A

FINA LC ONT R O LD E VIC E

M/A C ONT R O LS TATION

S E T P OINT

P R E S S U R E ANDT EMP E R AT U R EC OMP E N S ATION

S T E AM

T EMP E R ATU R EF L OWP R E S S U R E

Typical single-drive control system. For simplicity, redundanttransmitters have not been shown on this typical control drawing.S ee Figure 4A for AN S I/IS A- S 5.1-1984 format.

L E V E L P R E S S U R E

D R UM

T EMP E R AT U R EC OND E N S ATION

F L OW T EMP E R AT U R E

F E E DWAT E R

Objective: To maintain a constant steam temperature at turbine inlet despite large load swings .

Basic methods :

DESUPERHEATING (ATTEMPERATION)

Fine spray of comparatively cool water droplets into the vapour to reduce steam temperature.

BURNER TILT POSITIONING

Raise/Lower the Fireball in the furnace by tilting burners upwards or downwards.

Steam temperature control


Boiler C&I



Boiler C&I

Secondary Air Damper Control

Maintains proper windbox air flow distribution

0 to 30 % unit load, all auxiliary dampers modulated to maintain windbox to furnace differential pressure

Above 30% unit load, BMS “closes” elevations of auxiliary dampers that are not required for elevations of fuel currently in service

Fuel air dampers are positioned on an elevation basis as a function of thecorresponding coal feeder speed

High windbox to furnace differential pressure opens all the secondary air dampers

Two types of dampers – Fuel air dampers & Auxiliary air dampers


Boiler C&I

• Cascade control used for Spray de-superheating loop

• MS temperature error establishes the set point for SH DESH outlet temp.

• SH DESH outlet temp. error positions the spray control valve such as to regulate the MS temperature within allowable limits.

• Burner tilt responds to the lower of SH or RH outlet temp.

• Spray control responds to the higher of SH or RH outlet temp.



Boiler C&I

BOILER AUXILIARIES INTERLOCKS AND PROTECTION SYSTEM

Scope :

Sequence control of starting and protection & interlocking of boiler auxiliaries…

– FD fans – ID fans– PA fans – Airheaters– Dampers– Valves


Boiler C&I

FURNACE SAFEGUARD SUPERVISORY SYSTEM

( FSSS )

This system takes care of interlocks required for starting, supervising the operating and safe shut down of the equipments connected with fuel firing

system.


Boiler C&I

Tangential Windbox


Boiler C&I

FURNACE PLAN CORNER DESIGNATION

FRONT WATER WALL

SE

CO

ND

AR

Y A

IR

2

C

E

RN

O

R -

SE

CO

ND

AR

Y A

IR

1

C

E

RNO

R-

4

C

E

RN

O

R-

3

C

E

RNO

R-


Boiler C&I

Fireball –Tangential Firing


Boiler C&I

CAUSES OF FURNACE EXPLOSIONS– An interruption of

• Fuel or • Air supply or • Ignition energy

to the burners, sufficient to result in momentary loss of flames, followed by restoration and delayed re-ignition of an accumulation.

– Fuel leakage into an idle furnace and the ignition of the accumulation by a spark or other source of ignition.

– Repeated unsuccessful attempts to light-off without appropriate purging, resulting in the accumulation of an explosive mixture.

– The accumulation of an explosive mixture of fuel and air as a result of loss of flame or incomplete combustion at one or more burners in the presence of other burners operating normally or during lighting of additional burners.

– The accumulation of an explosive mixture of fuel and air as a result of a complete furnace flameout and the ignition of the accumulation by a spark or other ignition source, such as could occur where attempting to light a burner(s).

– Purging with an airflow that is too high, which stirs up combustibles smoldering in hoppers.


Boiler C&I

CAUSES OF FURNACE IMPLOSIONS

– A mal-operation of the equipment regulating the boiler gas flow, including air supply and flue gas removal, resulting in furnace exposure to excessive induced draft fan head assembly.

– The rapid decay of furnace gas temperatures and pressure resulting from either a rapid reduction in fuel input or a master fuel trip.

– A combination of the two conditions indicated in a, b above has resulted in the most severe furnace implosion incidents.


Boiler C&I

FUNCTIONS OF FSSS

1. FURNACE PURGE SUPERVISION2. SECONDARY AIR DAMPER MODULATION AND ON-OFF

CONTROL AND SUPERVISION3. IGNITOR ON-OFF CONTROL AND SUPERVISION4. LIGHT OIL ON-OFF CONTROL AND SUPERVISION 5. HEAVY OIL ON-OFF CONTROL AND SUPERVISION6. PULVERIZER AND FEEDER ON-OFF CONTROL AND

SUPERVISION7. FLAME SCANNER INTELLIGENCE AND CHECKING8. BOILER TRIP PROTECTION.


Boiler C&I

FSSS

F S S S

F - FURNACE

S - SAFEGUARD

S - SUPERVISORY

S - -SYSTEM

FSSS ENSURES SAFE FURNACE OPERATING CONDITIONS DURING

START UP LOW LOAD OPERATION SHUT DOWN.


Boiler C&I

SOME OF THE PRECAUTIONARY MEASURES TO ACHIEVE SAFE AND RELIABLE OPERATION

FURNACE SHOULD BE PURGED BEFORE LIGHT UP ADEQUATE IGNITION ENERGY TO EACH BURNER ADEQUATE AIR SUPPLY TO EACH BURNER TO AVOID

FLAME OUT OPTIMUM FURNACE PRESSURE CORRECT AIR TO FUEL RATIO


Boiler C&I

FSSS

FUNCTIONAL DIVISION OF LOGICS

UNIT LOGIC

ELEVATION LOGIC

CORNER LOGIC


Boiler C&I

FSSS

TYPICAL CONDITIONS FOR FURNACE PURGE:

- Heavy fuel oil trip valve closed.- Heavy fuel oil nozzle valves closed.- Light fuel oil trip valve closed.- Light fuel oil nozzle valves closed.- Flame scanners on each elevation indicate no flame.- Air flow greater than 30% and less than 40%

- All pulverisers off. - All feeders off.- Pulveriser outlet gates closed.- All hot air gates closed. - All cold air dampers not greater than 5° open.- Both PA fans off.- No boiler trip existing.– All auxiliary air dampers modulating.


Boiler C&I

BOILER TRIP COMMAND IS INITIATED BY

LOW OR HIGH DRUM WATER LEVEL BOTH I.D OR F.D ARE OFF LOW OR HIGH FURNACE PRESSURE REHEATER PROTECTION TRIP TURBINE LOSS OF ALL FUEL TRIP LOSS OF UNIT D.C POWER LESS THAN FIRE BALL AND LOSS OF AC AT

ANY ELEVATION MANUAL TRIP UNIT FLAME FAILURE TRIP INSUFFICIENT PRIMARY AIR


Boiler C&I

FSSS

BOILER TRIP COMMAND RESULTS IN

STOPPAGE OF ALL FUEL INPUTS BY TRIPPING

1. ALL PULVERIZERS

2. ALL FEEDERS

3. ALL OIL GUNS

4. ALL IGNITORS

IT CLOSES

1. IGNITOR

2. LIGHT OIL TRIP VALVES

3. HEAVY OIL TRIP VALVES


Boiler C&I

FSSS

Scanner Fan logic

• “Scanner duct to furnace DP” when low initiates a Scanner air fan -A “run” command

• If DP value remains “low” for more than five seconds, scanner air fan -B “run” command is issued.

• If DP condition is low even after 10 seconds “Loss Of Scanner Cooling Air” alarm is generated


Boiler C&I

Seal Air Fan Control

• When either Primary Air Fan is on, seal air fan “A” is automatically placed in service.

• If either Primary Air Fan is on & Seal Air Header/Cold Air Duct DP is low, the seal air fan is auto started.

• When both seal air fans are on and the Seal Air Header/Cold Air Duct DP is not low,either seal air fan can be stopped manually.


Boiler C&I

PULVERIZER STARTING PROCEDURE

START< “PULVERIZER ON” FEEDBACK OPEN HOT AIR GATE< WAIT TILL PULVERIZER COMES TO TEMPERATURE

( 140°F ) START FEEDER ( AT MINIMUM FEEDER SPEED )< COAL FLOW INDICATOR OR PULVERIZER AMPERE (

( WITH IN 5 SECONDS )< FIFTY SECONDS FEEDER SPEED RELEASED TO AUTOMATIC CONTROL FUEL AIR DAMPER OPENED

FUEL AIR DAMPER MODULATED TO AUTOMATIC CONTROL.


Boiler C&I

FSSS

PULVERIZER START REQUIREMENTS

A IGNITION ENERGY AVAILABLE

B. ADEQUATE PRIMARY AIR

C. D.C POWER AVAILABLE

D. LOCAL PULVERIZER CONDITION SATISFACTORY

E. IF NO OTHER FEEDER IS WORKING FUEL AND AIR NOZZLE TILTS PLACED IN HORIZONDAL CONDITION.


Boiler C&I

FSSS

CONDITIONS ( LOCAL ) TO BE SATISFIED TO START RESPECTIVE PULVERIZER

A. DISCHARGE VALVE OPEN

B. SEAL AIR VALVE OPEN

C. COLD AIR DAMPER OPEN

D. PULVERIZER DAMPER OUTLET LESS THAN 200°F

E. FEEDER INLET GATE OPEN

F. TRAMP IRON HOPPER VALVE OPEN.


Boiler C&I

FSSS

PULVERIZER IGNITION ENERGY AVAILABLE

A MINIMUM OF 3 OF THE 4 LIGHT OIL OR HEAVY OIL NOZZLE VALVE OF THE ELEVATION JUST ABOVE OR BELOW, ARE OPEN

OR

BOILER LOADING IS GREATER THAN 30% AND PULVERIZER JUST ABOVE OR BELOW IS IN SERVICE AT GREATER THAN 50% LOADING.


Boiler C&I

FSSS

MILL OUTLET TEMPERATURE CONTROL

HIGH PULVERIZER OUTLET TEMPERATURE (ABOVE 200°F )

WILL

OPEN COLD AIR DAMPER

AND

CLOSE HOT AIR GATE.


Boiler C&I

FSSS

FEEDER CONTROL

A. FEEDER RUNS AT MINIMUM SPEED UNTIL INITIATING CONDITION IS CORRECTED, AT WHICH TIME THE FEEDER WILL BE RETURNED TO CONTROL.

A. PULVERIZER BOWL DIFFERENTIAL HIGH.B. PULVERIZER AMPS. ABOVE MAXIMUM SET POINT.

B. LOSS OF COAL FLOW AND LOW PULVERIZER CURRENT WILL TRIP THE FEEDER, OPEN COLD AIR DAMPER AND CLOSE HOT AIR GATE.AFTER CORRECTIVE ACTION THE HOT AIR GATE IS OPENED AND FEEDER IS RESTARTED.


Boiler C&I

FSSS

CONDITIONS FOR A PULVERIZER TRIP

PULVERIZER DISCHARGE VALVE NOT OPEN

LOSS OF UNIT DC POWER (FOR MORE THAN 2 SECONDS)

PULVERIZER IGNITION PERMIT NOT SATISFIED AND SUPPORT

IGNITION IS REQUIRED.

BOILER TRIP

PRIMARY AIR FAN TRIP


Boiler C&I

FSSS

PULVERIZER SHUT DOWN SEQUENCE

START ASSOCIATED OIL ELEVATION REDUCE FEEDER SPEED TO MINIMUM CLOSE HOT AIR GATE< PULVERIZER OUTLET TEMPERATURE IS 120°F STOP FEEDER< WAIT FOR 2 MINUTES STOP PULVERIZER< FURNACE STABILIZES ASSOCIATED OIL LEVEL SHUT DOWN.


Boiler C&I

FSSS

PULVERIZER SHUT DOWN

START ASSOCIATED OIL ELEVATION REDUCE FEEDER SPEED TO MINIMUM CLOSE HOT AIR GATE< PULVERIZER TEMPERATURE IS 120°F STOP FEEDER< TWO MINUTES STOP PULVERIZER< FURNACE STABILIZES SHUT OFF ASSOCIATED OIL ELEVATION.


Boiler C&I

FSSS

ARRANGEMENT OF SYSTEM

FSSS - MAJOR PARTS

LOGIC CABINET CONSOLE INSERT SECONDARY AIR DAMPER PANEL MILL PANEL FIELD EQUIPMENTS CUSTOMER SUPPLIED INTERFACE

EQUIPMENT.


Boiler C&I

FSSS

Oil gun start sequence

• HEA Advances• Atomising valve opens• Corner oil valve opens• HEA sparks• Flame scanner picks up flame• HEA retracts • Corner valve closes if flame is not sensed.


Boiler C&I

Boiler C&I

FSSS – Oil gun start up timing sequence

THANK YOU

boiler controls & instrumentation k karthikeyan manager controls & instrumentation bhel,...

Documents

boiler ci area

boiler ci discipline

tiruchirappalli email

individual system scope

project scope of work

system engg

auxiliary prds control

customer end