Furnace Start-up and Shutdown

5/25/2018 Furnace Start-up and Shutdown

1/47

A Sunrise Project for a Sunshine Future

PARADEEP REFINERY PROJECT

FacultyN R Das

SPNE-CG

Prepared byProduction-CG Team


2/47

AGENDA FOR THE PRESENTATION


Configuration of High Efficiency/ Modern Heaters

Heater Instrumentation and controls

Introduction to Burner Management System

Heater Commissioning/ Start-up

Start-up Precautions and Monitoring

Heater Shutdown

What May Go Wrong



3/47

PARADEEP REFINERY PROJECTA Sunrise Project for a Sunshine Future


4/47

CONFIGURATION OF MODERN HEATERS



5/47

CONFIGURATION OF MODERN HEATERS



6/47



7/47

HEATER INSTRUMENTATION & CONTROLS


PC

TC

FC

PT

PT

FQ

FT

FT

FC

FC

FC

O2

SOxNOx

TT

TT

TT

TT

TT

PTTT

TT

TTTT

FT


8/47

HEATER FIRING CONTROL


PC

TC

FC

FT

PT

FQ

FT

FT

FC

FC

FC

O2

SOxNOx

TT

TT

TT

TT

TT

PTTT

TT

TTTT

FIRING

CONTROL


9/47PARADEEP REFINERY PROJECT



10/47

NEED FOR BMS


BMS System evolved out of a need for a Separate System apart

from the control system for

Optimization of fuel consumption

Safe start-up of the furnace through programmed sequences bounded by

safety Interlocks and Start permissives

Supervising the safety limits during operation

Supervising the presence of pilot and Main flame during operation with the

help of Dedicated flame scanners

Activation of safe Shutdown in the event of any unsafe condition

Preventing the catastrophic combustion of fuel or Explosion

For providing the operating personal an environment free of Hazards



11/47

BMS - How Burner is managed?


Sequence Controls (Permissives)-For Startup

Pilot & Main Fuel Block Valves leak proved Absence of Flame proved

Prepare flow proved

Prepurge Timer complete

Minimum configured pilots are lit

Trip Interlocks-For Normal Operation

Loss of Flame

Fuel pressure Low

Fuel pressure High Loss of Combustion air

High Process Temperatures


12/47PARADEEP REFINERY PROJECT



13/47

SAFETY CHECKS BEFORE HEATER STARTUP


A furnace is safest when it is functioning properly.

Combustion occurs when fuel and oxygen meet a source of ignition.

If any one of these three elements is missing, ____________ cannot take

place.

Combustion can occur in an idle furnace, if fuel, oxygen, and a source of

ignition come together. Wherever there ia air, you can be sure there is

_______________.

During shutdown, flammable vapors may seep into the firebox. Anything

that can burn is ______________.


combustion

oxygen

flammable


14/47

SAFETY CHECKS BEFORE HEATER STARTUP


Fuel and oxygen need only a source of ignition to ________.

Even though a furnace is idle, you must assume that there may be ________

in the firebox.

Rapid ignition or combustion in a confined space is an explosion. Explosions

occur when air and fuel have mixed and come into contact with a source of

__________.

The longer an unblinded furnace has been idle, the more likely it is to lack

only a _________ of ignition.

Over the years, more than half of all furnace explosions have occurred

during startup. Most explosions happened because fuel that the operator

didntknow was there had mixed with _______ and was waiting for ignition.

A furnace is most dangerous at ______________.


Start up

burn

fuel

ignition

source

air


15/47

PHYSICAL CHECK BEFORE STARTUP


The furnace and the area around it must be clean and free of flammable

material.

All valves in the fuel gas and fuel oil systems and all burner valves must be

checked to see that they are closed.

Both the _________ gas valve and the pilot valve must be checked to be

sure they are _____________.


steam

On an oil burner, you normally

have two oil valves and three

steam valves to close. All

_______ and ________ valves

must be closed.

burner

closed

oil


16/47

PHYSICAL CHECK BEFORE STARTUP


After the damper mechanism has been checked, the stack ___________

should be fully opened.

The secondary air doors on all _____________ should be fully opened.

To purge the furnace properly later on, the purging steam or air must be

able to flow freely through the furnace. The stack damper and all secondary

air dampers must be _________ to provide this flow.


damper

burners

open


17/47

PURGING BEFORE LIGHTING THE BURNERS


It is dangerous to light the burner without ________the furnace first.

Purging must be thorough to make sure that no flammable __________remain in the furnace.

Steam is used for purging. Ensure that the steam is free of condensate.

Steam purging provides heat to start the draft.

Your unit operating instructions tell you how long to purge the furnace with

steam, and may specify a minimum draft during the purge.

Purging is used to create a _________ and remove all flammable

__________ from the furnace.


gases

purging

gases

draft


18/47

PURGING BEFORE LIGHTING THE BURNERS


Purging makes sure that you have the three elements of ____________

(fuel, air, and heat) under control when you light the burners.

Ensure that there are no flammable vapors mixed with air in the firebox.


combustion


19/47

REMOVING BLINDS - BEFORE LIGHTING THE BURNERS


Before lighting the burners, follow Standing Instructions and SOP (Standard

operating procedures).

Ensure that the blinds in the main fuel lines to the furnace are removed as

per unit operating instructions. Purge the fuel system as per the instructions.

With the blinds removed, the chances that the fuel may seep into he firebox

through any valve leakage are now increased.

Ensure that all burner valves are __________ before opening the main fuel

valve to furnace.

Drain fuel gas knockout pot to ensure that there is no presence of liquid

hydrocarbon in fuel gas.

Ensure that there is no water in the fuel oil line.


closed


20/47

LIGHTING THE BURNERS


On a furnace with a gas pilot, light the pilot before you light the burner.

Once the pilot is lighted, it is a steady __________ of ignition for the burner.

Establish circulation through furnace coils before the first __________ is

lighted.

A furnace burning both gas and oil is normally started with ________.

The gas burner provides a steady source of __________ for the oil.

Gas ignites and burns more easily than oil.

Begin lighting the burners immediately after you have finished __________

purging the furnace.

Automatic igniters are installed for lighting of pilot burners.


source

burner

gas

ignition

purging


21/47



Portable igniters are also used to light the pilot burners.

In earlier days, torch was used to light the pilot burners.

After lighting the burner, steady the ________ pattern by adjusting air

dampers.

If the fuel does not ignite promptly, shut off the burner.

If the fuel does not ignite at the first burner, you must _______________.

If you have to purge again, repeat the whole ___________ procedure.

One burner should never be lighted from another burner. This is a

dangerous practice. Only a _________ provides a steady and reliable source

of ignition.


flame

purge again

purging

pilot


22/47



When you are firing two fuels, one is normally base loaded and you

control temperature with the other.

Do not try to light the oil gun of a combustion burner until the _______

burners are maintaining a stable flame pattern.

Ensure draining of _____________ from atomising steam line, before

lighting up oil burner.

During startup, frequently check the individual burner flames and the

flame pattern in the ____________. Wear a face mask whenever you look

into the firebox.

Watch for irregular burning patterns. Flame impingement causes hot spots.

Watch the radiant tubes for hot spots and adjust the _________ pattern to

eliminate them.


firebox

gas

condensate

flame


23/47



Tubes should be checked from shift to shift to detect hot ________ and to

observe how much the spots are changing, and how fast.

After the furnace is on stream and lined out, check the entire operation for

draft and _________ air control.


excess

spots


24/47

HEATER STARTUP PRECHECKS


Check all the following conditions are satisfied

Check if all the Manual block valves in fuel lines are closed

Fuel gas control valve set at 20% on manual mode

Steam to SAPH closed

All burner air dampers are open

Stack Damper Open

ID fan inlet (IGV) closed

Flue gas analyser not in operation



25/47

START PERMISSIVES


Check if all the following Permissives are Healthy

All pilot flame scanners unhealthy.

All main flame scanners unhealthy.

All pilot header block valves closed and bleed valves open.

All main FG header block valves closed and bleed valves open.

All BMS interlocks are healthy/necessary interlocks bypassed.

Local Reset Push button activated.

Main stack damper open.



26/47

FUEL GAS LINESPURGING & LEAK CHECK


Purging of Pilot and Fuel Gas lines

Before admitting fuel gas into the line to the burners it may be

necessary when fuel gas is containing more than 15 vol. % H2 to purgethe line with nitrogen.

Connect N2 Hose in the common fuel gas line LPD downstream of Filter

pressurize and purge it through HPV in the ring headers of Pilot and Main FG

Leak Check of Pilot Gas line Automatic Block Valves

Line-up all the block valves in Pilot and Main FG lines (except burner

globe and ball valves)

Initiate Pilot & Main burner leak check by pressing Start leak test

Push Button Pilot leak test in progress lamp glows in LCP and a preset timer starts

which will be reset only if Start purge button Pressurisation step: Pilot gas line bypass block valves open and bleed valve

closes. The system checks if the downstream pressure reaches the upper

leak check set point within the pressurisation period (1 min and

adjustable).



27/47



Depressurisation Step: Pilot gas line bypass block valves closes and bleed

valves open. The system checks if the downstream pressure reaches the

lower leak check set point within the depressurisation period (1 min andadjustable)

If Pressurisation and depressurisation steps are completed successfully

Pilot Leak test clear appears in LCP. If during pressurisation or

depressurisation tests, the set value checks fail Pilot leak test failed

appears in LCP.

If leak check fails rectify the problem and start leak test again.



28/47



Leak Check of Main Fuel Gas line Automatic Block Valves

Once the Pilot leak check is cleared, the BMS will automatically initiate

Main FG leak check. Burner leak test in progress lamp glows in LCP.

Pressurisation step: Main FG gas line bypass block valves open and bleed

valve closes. The system checks if the downstream pressure reaches the

upper leak check set point within the pressurisation period (1 min and

adjustable)

Depressurisation Step: Main Fuel gas line bypass block valves closes andbleed valves open. The system checks if the downstream pressure reaches

the lower leak check set point within the depressurisation period (1 min

and adjustable)

If Pressurisation and depressurisation steps are completed successfully

Burner Leak test clear appears in LCP. If during pressurisation or

depressurisation tests, the set value checks fail Burner leak test failedappears in LCP.

If leak check fails rectify the problem and start leak test again.



29/47

FUEL GAS LINESLEAK CHECK


PT

PT

O2

SOxNOx

TT

TT

TT

TT

TT

FT


30/47

FURNACE BOX PRE-PURGING


Heaters must be purged with air before burners are lighted to evacuate all gas

that could have been sent to the firebox during the test

Now start FD fans (at least one) as per the start-up procedure and open

the discharge damper

Reach a maximum air flow or flow recommended by vendor.

Activate Start Purge Push button.

All the above steps are to be completed before timer that got activated

during burner leak check (Depends upon the vendor)

Minimum Purgiging time should be such that it should renew 5 times the

volume of heater or 15 Minutes


31/47

PILOT GAS BURNERS LIGHT-UP


Pilot gas burner light-up Preparation

Reduce the air flow from FD fan to say 25% of capacity

Adjust the stack damper so that the proper draft level for furnace operation isachieved.

Close the burner air control dampers to the 25% open position.

Pilot gas burner light-up can be started once the Open pilot block valves

push button is pressed Open the main pilot fuel supply valve making fuel gas available upto all of the

individual pilot valves

Keep the pilot mixer air door is of the pilot to be first lit-up to say 50% open.

Insert the igniter, Press the Open push button for that pilot to be lit-up and

activate the igniter. The pilot should light instantly. If the pilot does not light after 10 seconds

automatic block valve will get closed.

If lit-up adjust the pilot valve and air door for a stable flame.

Light up all pilots in the same manner.


32/47

MAIN GAS BURNERS LIGHT-UP


Main gas burner light-up Preparation

Adjust the draft such that there is sufficient air pressure drop across the burner

Set the burner air control dampers at 50% open.

Main gas burner light-up can be started once the Open main FG block

valvespush button is pressed

Now the automatic block valves will open and charge the FG upto individual block

valves

The burners can now be ignited manually by opening the burner isolation valve

(ball valve) slowly while observing the flame.

If flame is not established within 3 secs of valve being fully open, it should be

closed immediately. Further attempts shouldnt be made for 5 minutes.

All main burners can be lit up in similar fashion.

Adjust the operating conditions as required by the process. But the minimum

firing rate prescribed by the vendor should be respected.

Adjust the conditions for optimum O2 level in the Stack


33/47

OIL BURNERS LIGHT-UP


Oil burner light-up Preparation

Reset the Oil supply and return automatic block valves

Lineup supply and return line valves upto the individual burner block valves

Establish oil circulation

Light-up Sequence

The burner which is going to be taken in line should already be lit-up with fuel gas Open the steam valve and cross over valve (purge) to the oil gun until both oil and

steam lines to each burner and also the oil gun are completely warmed up with

steam only.

Close cross over valve and adjust steam valve to 3.5-4.0 Kg/cm2g steam pressure.

Open oil valve gradually until ignition is established. Isolate fuel gas to that Burner

Adjust oil valve for capacity required and adjust steam valve to achieve proper

flame pattern.


34/47



35/47

START-UP PRECAUTIONS


The following Precautions needs to be exercised during furnace start-up

Quick heating-up is likely to cause excessive stresses on tubes and supports

Over pressure in the fire chamber can cause personnel injury or material damage

as hot flue gas would leak out of sight doors, not blanked-off connections,

unpacked tube seals, etc

Ensure Flow through the coils as it is a certain way of protecting the tubes from

excessive temperature.

Too low a flow rate through the passes with respect to heat flux can be the causeof tube overheating or hydrocarbon coking.

Possibility of condensation in the fuel lines must be checked with respect to

atmospheric conditions and avoided. Line must be drained frequently checking for

water or condensates.

Burner operation shall also be carefully and constantly watched to identify any

abnormal occurrence: flame impingement, wrong shape, instability, nozzle

plugging, coke formation, etc

During start-up, heater draught must be watched as it increases progressively with

the heat released


36/47

START-UP MONITORING


During start-up, heater draught must be watched as it increases progressively

with the heat released, using for that the draught gauges installed locally and

comparing them to the values transmitted to control room. Operation of thedraught dampers when there is one must be smooth and draught must be

effectively controlled.

During first start-up, all devices and instruments being used for the first time

in real conditions, it is of paramount importance to check their actualoperation and response constantly, until sufficient confidence is gained. Quick

material and thermal balances will help to detect abnormal recordings.

It comes naturally up that first start-up must be conducted slowly and if

possible stepwise to allow timely checking and observation.

In case of abnormal occurrence, it is of paramount importance that operators

can react in the right way within the shortest time.


37/47



38/47

CONTROLLED SHUTDOWN


Controlled Shutdown Sequence

Reduce fuel pressure slowly from control panel and simultaneously reduce the

combustion air flow

Once fuel pressure downstream of Pressure control valve reduces to a minimum

value or PCV opening reduced to minimum, start cutting off burners one by one.

Individual burner air dampers needs to be throttled as CA duct pressure reduces.

If oil burners are in line, isolate them and flush with atomizing steam

When main fuel gas is to be tripped, close the PCV completely and automatically

the block valves will get closed

Open Stack damper fully.

Actuate Pilot gas trip by isolating the main pilot line isolation valve. This action will

trip FD fan also.

Bypass Pilot gas low low pressure trip and Restart FD fan

Allow cooling of the furnace box with FD fan running


39/47

SHUTDOWN


The flow rate of the charge and the heat of the furnace are reduced together.

The charge rate and temperature are gradually ____________ over a period

of several hours.

When the charge rate and temperature have been reduced to a fraction of

normal, all furnace __________ are shut off.

The entire unit is circulated down. The oil left in the unit is circulated within

the unit oil system, including the ____________ tubes.

Circulation is continued through most equipment for several hours to cool the

unit. When the unit is cool enough not to vaporise the oil anywhere in it,

circulation is __________.stopped

reduced

burners

furnace


40/47

SHUTDOWN


Reduction in the transfer temperature automatically ____________ the burner fuel

supply. While reducing transfer temperature, cut off burners as per requirement.

When the charge rate and temperature are down to the desired level, all

____________ are shut off by closing each burner fuel valve individually.

Each gas pilot is shut off by closing the pilot _______.

Steam is left on in each oil gun as the oil regulating valve is closed. It is used to

_____________ the oil gun.

After all the burner gas valves are closed, the gas header valve is closed. Then all block

valves and bypass valves are closed.

If the furnace is to be out of service for some time, blinds should be installed in the

_________ lines.fuel

reduces

burners

valve

purge


41/47

EMERGENCY SHUTDOWN


Emergency shutdown is called for when furnace operations becomes

seriously abnormal.

In order to act wisely, you must know the maximum allowable temperature

and pressure of the _________ metal.

You must know the maximum allowable _____________ for the firebox,

breeching, and the stack.

You must be ready to stop combustion by removing one or more of the three

elements of combustion, ___________ air, or heat.

You must know in advance that emergency block and blowdown valves are in

working order and how to reach them in an emergency. These emergency

controls are located in a protected area where they can be reached with

_________________ risk.

fuel

tube

temperature

minimum, or little


42/47

REVERSING THE PROCESS OF COMBUSTION


You can ordinarily keep fuel oil and gas out of the firebox by closing the

burner _____________. You may have to go back to the block valves or the

header block valve. These valves stop the fuel to all _________.

In normal operation, you do not think of the charge as fuel. In the event of a

tube rupture, the charge enters the firebox from the ruptured tube and

burns. Then you must think of charge as ____________.

Since the charge is under pressure, a tube rupture may dump large amounts

of the charge into the firebox. Shutting off the charge and dumping it from

the furnace does not get rid of what is in the _____________.

The oil is best disposed of by burning it where it is, since the firebox is built to

support the heat of burning. To keep temperatures from running too high

during this combustion, you may need to control the __________ supply.air

valves

fuel

burners

firebox


43/47



You may have to choose which of the three elements of combustion to

control or get rid of, or try to eliminate all the three at once.

Stop or control the __________ Restrict the _______

Cool and put out any source of ____________ that is present

A tube rupture may suddenly admit a large amount of fuel into the firebox.

Your action will depend upon how serious the situation is and how well you

can control temperatures. If the leak is small, the charge may be left in the

____________ tubes while the unit is circulated down.

The furnace must be isolated and depressured if the rupture is large. Shut off

the burner fires. Dump the furnace and cool the tubes by turning steam into

them. Then ___________ the firebox with steam.purge

fuelair

ignition

furnace


44/47



Improper operation of oil burners could lead to large amounts of oil burning on the

floor of the furnace. Correct the burner operation. If temperatures become excessive,

restrict the input of ______ by adjusting the stack damper.

Flammable liquid in the fuel gas line may fill the firebox with uncontrolled flames.

Drain the fuel gas system. If temperatures become excessive, adjust the stack damper

to restrict the input of ______.

Cool the firebox with steam. If temperatures still rise in the tubes beyond themaximum, block off the furnace and dump the ___________. Put steam into the

tubes.

An operator who has worked successfully through an emergency shutdown has new

knowledge of himself and his _______________________.

By deliberately applying your knowledge and measuring your actions by the severity

of the emergency, you turn each ___________ into experience that prepares you

better for all furnace operating situations.

emergency

air

air

charge

equipment, or furnace

WHAT MAY GO WRONG?


45/47

WHAT MAY GO WRONG?


Furnace Explosions can occur with any or a combination of the

following

Loss of Flame in one or more burners while the others are in operationAccumulation of Combustible gasses inside the furnace followed by

formation of explosive mixture inside the box

Complete Flame-out followed by an attempt to light a burner

Accumulated Hydrocarbons inside the furnace after Flame-out forms

explosive mixture and explodes while re-ignitionFuel Leakage into an idle furnace ignited by a source of ignition

Fuel leakage into the Idle furnace due to passing of fuel gas block valves

leading to formation of Explosive mixture

Repeated attempts to light-off the furnace without properly purging the box

Accumulation of Hydrocarbons due to delay in ignition of burners due to

problem of igniter or flow of excessive combustion airMomentary loss of flame followed by delayed ignition

After burn causes sudden rise in pressure in the convection section or the

flue gas duct causing damages


QUERIES


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QUERIES



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Documents

Furnace Start-up and Shutdown