fired heatershjg

7/30/2019 Fired Heatershjg

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FIRED HEATERS


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SCOPE TYPE OF HEATERS

IN GENERAL

IN MRPL

NOMENCLATURE

BURNERS

TYPES

REFRACTORIES


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TYPES OF HEATERSClassified on

Draft

Fuel used

Orientation of burners

Orientation of tubesShape of the heater


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DRAFT

Flow of gas/air in the heater

As gases become hotter they becomelighter, and this makes it to rise up

When this is routed through a narrow

space, a negative pressure isgenerated.


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DraftPRESSURE

Weight of Air

column

P1 = Wt of Cold Air + Wt of Hot Air

P2 = Wt of Cold Air

P2 > P1


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DRAFT.. This pressure differential causes air to

come into the heater

Why Essential?

Scavenging Gas Out

Bringing New Air

Distribute Heat


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NATURAL DRAFT Draft by density difference.

The weight of air inside theheater/stack is lesser than the weightoutside

This forces the air to come rushing in

from the outside creating a draft


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EXAMPLES OF NAT DRAFT NSU HEATER

NAPTHA VAPOURISER

CIRCULAR HEATERS IN HCU

KERO HEATER IN CDU2

(EFFICIENCIES OF NAT DRAFTFURNACES ARE VERY LOW. SO NOT

GENERALLY PREFERRED)


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FORCED DRAFT Fresh air is forced into the heater

Forced draft fan

Hot air/flue gases goes out by itself thru astack

The heater will be under positive pressure


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EXAMPLES OF FD Boilers in CPP

(Box is under positive pressure. Thereforeprone to leakage/ accidents)


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INDUCED DRAFT Flue gases induced out of the

heater

By a fan or blower The gases so induced are forced

into the stack

Because of the -ve pressure, cold aircomes into the box


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EXAMPLES No pure ID heaters in MRPL

(Fine control not possible on inlet air)


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BALANCED DRAFT

Cool air forced into the heater Flue gases induced out of the heater

Forcing & Inducing by Fans

Net Negative Pressure inside box


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BALANCED DRAFT MRPL BALANCED DRAFT.

ADVANTAGES

Better draft control

Smaller heights of chimneys

Air-pre heaters increasing efficiency


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TYPICAL DRAFT IN HEATERS


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FUELS

Varied Fuels

Gas Fired

Oil Fired

Combination Fired

Waste Heat (Only Flue Gases)

Solid Fuel


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FUELS...

SOLID FUEL

Low Cost

Large Peripherals (Grate, Mills etc)

GAS

Precise control

Minute Variation

Fluctuating Loads


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FUELS...

OIL

High Heat Duty

Steady Loads

COMBINATION

Advantages of Both

Higher Heat Duty


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FUELS- IN MRPL

Solid Fuel None

Gas Fired HCU Reactor, H2 Reformer, CCR1

Reformer

Oil Fired Boilers Of CPP

Combination Crude, HCU, CCR2, VBU


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BURNER ORIENTATION

SIDE FIRED

BURNERS IN THE SIDE

CCR1 REFORMER

Shorter Heaters

Different Arrangements(RW)


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BURNER ORIENTATION

TOP FIRED

BURNERS ON THE TOP

FIRING DOWN H2 REFORMER

Better Heat Flux Control

Heater Size Smaller

Material Near Cracking


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BURNER ORIENTATION

BOTTOM FIRED

BURNERS ARRANGEDAT THE BOTTOM

ALL HEATERS

Oil can be used

High Heat Duty


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BURNER ORIENTATION RADIANT WALL

Burner fires to

Wall Heat Radiates

from Wall

Tubes see heat

not fire Even Distribution

of Heat


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BURNER ORIENTATION

INDIRECT FIRED

Better Control of Skin

Material in tubes nearcracking
http://www.schafferswelding.ca/images/flatflame1.jpg


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ORIENTATION OF TUBES

- HELICAL COIL

- VERTICAL COIL

- HORIZONTAL COILS


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SHAPE OF HEATER

CYLINDRICAL NSU, HCU-REACTOR,

NAPHTA VAPOURISER

CABIN CDU, VDU,HCU

FRACTIONATOR BOX

CDU2

NOMENCLATURE


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NOMENCLATURE

Shock Tubes


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NomenclatureStack

Damper

Arch

ConvectionTubes

ShockBank

RadiantTubes

RefractoryLining

Firebox


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HEAT TRANSFER

Heat transfer takes place in two ways

By radiation

By convection

Zones of the heater are also defined bythe mode of ht tfr


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HEAT TRANSFER

Radiant Section

Tubes directly see Fire

Convection Section

Heat transfer from hotgases to tubes


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BURNERS

Functions of a burner

Carries fuel into the heater

Mixes fuel with air

Provides area for safe burning


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TYPES OF BURNERS

Gas

Normal

Flat flame

Oil

Mechanical Atomization

Air Atomization

Steam Atomization


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TYPES

Combination

Oil and gas

Pilot

Low heat duty, provides a flame inside

Normally gas fired


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PILOT BURNERS

Provide flame inside heater at all times

Low heat duty burners

Normally gas fired

Air and gas is pre-mixed in a mixer

Mixture is burned in the pilot


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PILOTS

MIXER ASSEMBLY


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GAS BURNERS

Fuel used is Fuel Gas/ LPG/ Methane

Low heat duty burners No need for special atomization

Clean burning- no deposition on

tubes

Can be round flames or flat flames


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GAS BURNERS

ROUND FLAME FLAT FLAME


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OIL BURNERS

Fuel used is fuel oil LSHS/ VR

Atomizes the fuel into easily burnable

particles

Atomization by means of

Mechanical/ Swirler (CPP1)

Air atomization

Steam atomization

OIL BURNERS


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OIL BURNERS


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ATOMIZATION

Oil Enters Spud Velocity is

Increased

Oil & Steam MixesAtomized Mixture

Sprayed


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COMBINATION BURNERS

Combination of oil, gas and pilotburners

Advantages

Heavy duty

Fine control possible by gas burners

COMBINATION BURNERS


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COMBINATION BURNERS


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AIR

3 different airs exist in burners

Primary Air

Provides air for combustion to oil gun

Secondary air

Provides air for combustion for gas burners


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AIRS

Tertiary Air

Found in low NOX burners

At high temperature Nitrogen in air andOxygen tend to form NO or NO2

To prevent this tertiary air or cooling air is

provided around the burner


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AIRS

PRIMARY AIR

SEC AIR

TERTIARY AIR


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TROUBLESHOOTING

Problems

Flame Impingement

Tall Flame

Bushy Flame

Oil Seepage

Clinker Formation Meltdown


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FLAME IMPINGEMENT

Correction

Correct Alignment

Probable Cause

Misalignment


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TALL FLAME/ BUSHY FLAME

Tall flame

Excess fuel pressure/ atomizing media

pressure Burner too high in the block

Bushy flame

Lower pressure of fuel/ atomizer Burner too low in block


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OIL SEEPAGE

Cause

Improper

atomization Burner height too

low

Oil impinges on tile

Causes seepage


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CLINKER FORMATION

Improper atomization

Low oil flow thru oil tip Higher heat pick up from gas burners

Incorrect gun position


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MELTDOWN

Any Above left Unattended

High Heat of Tip

Melting

Spillage Fire

Meltdown


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REFRACTORY

Types Castables

Applied after forming a mortar Bricks/ preformed section

Ready use, applied with mortar

Ceramic blankets Std dimensions, locked with ceramic cup

locks

Ceramic modules Preformed sections, locked to holders


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REFRACTORY - APPLICATION

Type -- Location

Floor

Castable

Fire Brick / Insulating Brick

Radiant wall

Fire brick, Insulating brick, Ceramicblankets


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REFRACTORY-APPLICATION

Hip arch/ convection section

Castable/ ceramic modules

Corbel Castable

Ducts

Castable with potassium silicate coating


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REFRACTORY - DRYOUT

Refractory uses Water

Sudden Increase in Heat Steam Formation

Sudden Expansion

Collapse of Refractory

Slow Increase in Heat Hold at different steps (60, 80, 100, >100)

Outside Wall Temperature = 100** (>60)


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