chemical plant equipment & systems - topic 3-heat transfer equiment r1
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8/9/2019 Chemical Plant Equipment & Systems - Topic 3-Heat Transfer Equiment R1
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CLC122:
CHEMICAL PLANTEQUIPMENT & SYSTEMS
Topic 3: Heat Transfer
Equipment
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Topic 3.1: Modes of Heat Transfer
• Transfer of heat to and from process fluids is an essential partof most chemical processes in chemical plants.
• Heat is a type of energy called thermal energy and can be
transferred (moved) by three main modes: Conduction
Convection
Radiation.
• During heat transfer, thermal energy always moves in thedirection of Hot to Cold:
HOT COLD2
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• Temperature is a measure of how hot an object is.
• Heat transfer only takes place when there is a temperaturedifference. The heat energy flows from a hotter (highertemperature) area to a cooler (lower temperature) area.
• Different materials need different amount of energy to increasetheir temperature by the same amount.
To increase thetemperature of 1 kg
of water by 1°C,
requires 4200 J.
To increase thetemperature of 1 kg
of copper by 1°C,
requires 390 J.
Topic 3.1: Modes of Heat Transfer
Water
Copper
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• Water and copper require different amounts of energy becausethey have different values for a property called specific heatcapacity.
• Specific heat capacity is the amount of thermal energy requiredto increase the temperature of 1 kg of a material by 1°C.
• Thus, the specific heat capacity for water is 4200 J/kg°C; andfor copper is 390 J/kg°C.
• We can use specific heat capacity to calculate how muchthermal energy is needed to raise the temperature of a material
by a certain degree:
Thermal
energy
specific heatcapacity
temperaturechange= mass x x
T C mQ p
Topic 3.1: Modes of Heat Transfer
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For example:
Knowing the specific heat capacity of water is 4200 J/kg°C, howmuch energy is needed to increase the temperature of 600 g ofwater by 80°C in a kettle?
• Note: mass = 600 g = 0.6 kg (units consistency)
• Energy (Q) = 0.6 kg x 4200 J/kg°C x 80 °C
= 201,600 J
T C mQ p
Topic 3.1: Modes of Heat Transfer
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• Molecules arranged in solid, liquid and gas differently.
• Particles that are very close together can transfer heat energyas they vibrate. This type of heat transfer is calledconduction.
• Conduction is the method of heat transfer in solids but not inliquids and gases.
solid liquid gas
Topic 3.1: Modes of Heat Transfer(Conduction)
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Conduction in non-metals
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How do metals conduct heat?
• Metals are good conductors ofheat. The outer electrons of metalatoms are not attached to anyparticular atom. They are free tomove between the atoms.
• When a metal is heated, the freeelectrons gain kinetic energy.
• The free electrons move faster andtransfer the energy through themetal.
• Insulators do not have freeelectrons and so they do notconduct heat as good as metals.
heat
Conduction in metals
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• Liquids and gases are called fluids as they can both flow andbehave in similar ways.
• When a fluid is heated, the heated fluid particles gain energy, sothey move about more and spread out. The same number ofparticles now take up more space, so the fluid has become lessdense.
heat
less dense
fluid
Topic 3.1: Modes of Heat Transfer(Convection)
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• Warmer regions of a fluid are lessdense than cooler regions of thesame fluid.
• The warmer regions will rise because they are less dense.
• The cooler regions will sink as theyare more dense.
• This is how heat transfer takesplace in fluids and is called
convection.
• The steady flow between the warmand cool sections of a fluid, such asair or water, is called a convectioncurrent.
Topic 3.1: Modes of Heat Transfer(Convection)
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Convection in Liquid
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Convection in Gas
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Convection is important in fridges
• The freezer compartment is at thetop of a fridge because cool airsinks.
•
The freezer cools the air at the topand this cold air cools the food onthe way down.
• It is warmer at the bottom of thefridge.
• This warmer air rises and so aconvection current is set up insidethe fridge, which helps to keep thefridge cool.
Convection in gas
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• The Earth is warmed by heat energy from the Sun.
• There are no particles between the Sun and the Earth, so the heat
cannot travel by conduction or by convection.
• The heat travels to Earth by electromagnetic waves. These aresimilar to light waves and are able to travel through empty space(vacuum).
Electromagneticwaves
Topic 3.1: Modes of Heat Transfer(Radiation)
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• Heat can move by travelling as electromagnetic waves. Theseelectromagnetic waves are like light waves, but with a longerwavelength.
Electromagnetic waves act like light waves:
• They can travel through a vacuum.
• They travel at the same speed as light – 300,000,000 m/s.
• They can be reflected and absorbed.
• Electromagnetic waves heat objects that absorb them and are
known as thermal radiation.
Topic 3.1: Modes of Heat Transfer(Radiation)
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Radiation emit from surface
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• All objects emit (give out) some thermal radiation.
• Certain surfaces are better at emitting thermal radiation thanothers.
• Matt black surfaces are the best emitters of radiation.
• Shiny surfaces are the worst emitters of radiation.
white silvermatt
black
best emitter worst emitter
Topic 3.1: Modes of Heat Transfer(Radiation)
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Radiation absorb by surface
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• Thermal radiation heat objects that absorb (take in) them.
• Certain surfaces are better at absorbing thermal radiation thanothers. Good emitters are also good absorbers.
• Matt black surfaces are the best absorbers of radiation.
• Shiny surfaces are the worst absorbers because they reflectmost of the radiation away.
• This is why solar panels used for heating water are covered in a
black outer layer.
best emitter worst emitter
best absorber worst absorber
white silvermatt
black
Topic 3.1: Modes of Heat Transfer(Radiation)
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• Heat transfer is an important function of many chemical processes.
• Heat exchangers are equipment that widely used to transfer heatfrom one process to another .
• A heat exchanger allows a hot fluid to transfer heat energy to acooler fluid through conduction and convection. In fired heater , inaddition to conduction and convection, radiation is an important
mode of heat transfer as well.
Topic 3.2: Heat exchangers and theirapplications
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• The main types of heat transfer equipment used in the chemicalprocess industries are listed below, and they will be introduced in thesubsequent slides.
i. Double-pipe exchanger : the simplest type, used for cooling andheating.
ii. Shell and tube exchangers: used for all applications.
iii. Plate heat exchangers: used for heating and cooling.iv. Air cooled: used as coolers and condensers.
v. Fired heaters: used as charge heaters.
Topic 3.2: Heat exchangers and theirapplications
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Shell and tube heat exchanger
Double pipe heat exchanger
Plate heat exchanger
Air cooled heat exchanger
Fired heaters
Topic 3.2: Heat exchangers and theirapplications
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• The general equation for heat transfer across a surface is:
where Q = heat transferred per unit time, W or J/s
U = the overall heat transfer coefficient, W/m2°C
A = heat-transfer area, m2
ΔTm = the mean temperature difference, the temperaturedriving force,°C
mT UAQ
Topic 3.2: Heat exchangers and theirapplications
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• The overall heat transfer coefficient, U , will depend on the natureof the heat transfer process (conduction, convection,condensation, boiling or radiation), on the physical properties ofthe fluids, on the fluid flow-rates, and on the physical arrangementof the heat-transfer surface.
• During operation, most process fluids will deposit material (fouling) on the heat-transfer surfaces in an exchanger to some extent. The
deposited material will normally have a relatively low thermalconductivity and will reduce the overall coefficient.
• It is therefore necessary to oversize an exchanger to allow for thereduction in performance caused by fouling during operation.
Topic 3.2: Heat exchangers and theirapplications
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• Temperature difference is the driving force by which heat istransferred from a hot fluid to cold fluid.
• General equation for heat transfer across a surface and equationto calculate energy needed to raise the temperature of a fluid canbe used together in heat exchanger design calculation.
mT UAQ T C mQ p and
Topic 3.2: Heat exchangers and theirapplications
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For example:
Calculate the heat transfer surface area of a heat exchangerneeded to raise the temperature of a process stream flowing at100 kg/s from 30 °C to 60 °C. Given that the specific heatcapacity of the process stream is 2500 J/kg°C, the overall heat
transfer coefficient of the heat exchanger is 300 W/m2°C, andthe mean temperature difference is 25 °C
• Heat needed to raise the temperature of a process streamfrom 30 °C to 60 °C is :
• Heat transfer surface needed:
2
2
1000
25300
000,500,7
m
C C m s
J S
J
T U
Q A
T UAQ
m
m
s
J C C kg
J
s
kg
T C mQ p
000,500,7)3060(2500100
Topic 3.2: Heat exchangers and theirapplications
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Double pipe heat exchanger:
• The double pipe heat exchanger incorporates a tube within a tubedesign. Standard shell diameters range from 2” to 6”.
• It can be found with plain tube or externally finned tubes.
• In chemical plants, they are commonly used for high foulingservices and it is economical for smaller duties where the heattransfer area is less than 400 ft2 (40 m2)
Topic 3.2: Heat exchangers and theirapplications
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Finned tube
Double pipe heat exchanger using finned tube
Topic 3.2: Heat exchangers and theirapplications
Double pipe heat exchanger:
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Double pipe heat exchanger:
• In double pipe heat exchanger, the temperature changes of hotand cold fluid as they pass through a heat exchanger depends onthe flow arrangement.
• In parallel flow (Cocucurrent flow) case, both fluid enter at thesame end of exchanger and exit at the other .
Topic 3.2: Heat exchangers and theirapplications
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Double pipe heat exchanger:
• The cold fluid (lowercase t’s) experience a temperature increase,and the hot fluid (capital T’s) a temperature decrease. Thetemperature difference varies from T1-t1 at the inlet to T2-t2 at the
outlet.• The cold fluid exit temperature (t2) cannot exceed the hot fluid exittemperature (T2).
Topic 3.2: Heat exchangers and theirapplications
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Double pipe heat exchanger:
• In the counter-flow case, the fluids flow in opposite directions.This is much better than the parallel flow for most applications.
• The cold fluid exit temperature (t2) can exceed the hot fluid exit
temperature (T2) when there is sufficient heat transfer area.
• Counter-current flow maximizes temperature differences betweenshell-side and tube-side fluids.
Topic 3.2: Heat exchangers and theirapplications
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• When using the general equation for heat transfer in double pipe heatexchangers calculation, as the temperature difference between thecold and hot fluid vary continuously from one end of the exchanger tothe other , a log mean average temperature difference (LMTD) is used
for ΔTm.
And
)( LMTDUAQ
Topic 3.2: Heat exchangers and theirapplications
differenceretemperaturminalLesser te LTTD
differenceretemperaturminalgreater teGTTD
ln
Where
LTTD
GTTD LTTDGTTD LMTD
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For example: If hot fluid enters the exchanger at 90 °C exit at 60 °C,and cold fluid enters the exchanger at 40 °C exit at 55 °C.
If they are in parallel flow, the LMTD is:
If they are in counter-flow, the LMTD is:
C LMTD 6.19
5
50ln
55090 °C 60 °C55 °C40 °C
90 °C 60 °C
40 °C65 °C
50 °C 5 °C
25 °C 20 °C
C LMTD
4.22
20
25ln
2025
Note: Counter flow has a higher LMTD due to maximize temperature differences
Topic 3.2: Heat exchangers and theirapplications
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• For example:
ΔTm for Counter current flow:
∆=∆2 − ∆1
ln(∆2∆1
)
=50℃ − 40℃
ln(5040)
= 44.8℃
Topic 3.2: Heat exchangers and theirapplications
ΔT1 = (100 – 60)°C = 40°C
ΔT2 = (70 – 20)°C = 50°C
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ΔTm for Cocucurrent flow:
∆=∆2 − ∆1
ln(∆2∆1)
=80℃ − 30℃
ln(8030)
= 50.9℃
Topic 3.2: Heat exchangers and theirapplications
ΔT1 = (70 – 40)°C = 30°CΔT2 = (100 – 20)°C = 80°C
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Shell and Tube exchanger:
• The shell and tube exchanger is the most commonly used type ofheat-transfer equipment used in the chemical industry.
•
The advantages of this type of heat exchanger are:1. The configuration gives a large surface area in a small volume.
2. Good mechanical layout (a good shape for wide pressurerange operation).
3. Uses well-established fabrication techniques.
4. Can be constructed from a wide range of materials.
5. Easily cleaned.
6. Well-established design procedures.
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Shell and Tube exchanger:
• Essentially, a shell and tube exchanger consists of a bundle oftubes enclosed in a cylindrical shell. The ends of the tubes arefitted into tube sheets, which separate the shell-side and tube-side
fluids.• Baffles are provided in the shell to direct the fluid flow and supportthe tubes. The assembly of baffles and tubes is held together bysupport rods and spacers.
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Tie Rods Spacers
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Shell and Tube exchanger:
• Tube layout (arrangement) in tube bundle is typically, 1 in tubes ona 1.25 in pitch or 0.75 in tubes on a 1 in pitch.
• Triangular layouts give more tubes in a given shell. However,
triangular pitch makes mechanical cleaning of shell side notpossible. Hence not suitable for high shellside fouling services.
• Square layouts give cleaning lanes with close pitch.
Flow
pitch
Triangular
30o
Rotated
triangular 60o
Square
90o
Rotated
square 45o
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Square layout Triangular layout
Flow Flow
Topic 3.2: Heat exchangers and theirapplications
Shell and Tube exchanger:
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Shell and Tube exchanger:
• Flow in the tube side of the shell and tube heat exchangers canhave one or more tube pass through the shell as shown below.
One tube pass per shell
Two tube pass per shellFlow inside tubes
Two tube pass per shell
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Shell and Tube exchanger:
• Shell and tube heat exchangers can be connected in variety ofways. The two most common are series and parallel.
• Series arrangement is used where there are large heat transfer
surface requirements. Parallel arrangement is used where thereare needs to reduce pressure drop through exchangers.
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Shell and Tube exchanger:
During design, following guidelines can be used to allocate fluids inshell and tube heat exchangers.
• Put dirty stream on the tube side - easier to clean inside the tubes.• Put high pressure stream in the tubes to avoid thick, expensiveshell.
• When special materials required for one stream due to for examplecorrosivity, put that stream in the tubes to avoid expensive shell.
• Cross flow over tubes gives higher heat transfer coefficients thanflow in tubes, hence put fluid with lowest coefficient on the shellside.
• If no obvious benefit, try streams both ways and see which givesbest design.
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Reboilers
• Reboilers are group of shell and tube heat exchangers in whichthe mixed phase flow is important. It is closely associated withdistillation tower operation.
• The major types of reboliers are thermosiphons, kettle, andinternal (stab-in) reboilers.
Thermosiphons Kettle Internal
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Reboilers - Horizontal thermosiphon
• A fundamental difference between a vertical and horizontalthermosiphon arrangement is fluid assignment.
• For a horizontal thermosiphon, the boiling liquid is placed on the shell
side. Horizontal arrangement allows reboiler to be installed closer tograde which is easier for tube bundle cleaning. However, large plotarea is needed for tube bundle pulling.
• Tube side inlet should be on the top of exchanger and outlet on thebottom. In this way, the density increase as hot fluid cooled will not
affect flow.
Horizontal Thermosiphons Vertical Thermosiphons
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Reboilers - Vertical thermosiphon
• In vertical thermosiphon, the heating liquid is in the shell side andthe boiling liquid in the tubes.
• For vertical thermosiphon, the tube side has to be single pass.
• Vertical thermosiphons are often attached right to the tower andhave a short process return line. Piping is therefore simple andinexpensive. However, tube bundle cleaning is more difficult.
Vertical Thermosiphons
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Reboilers - Kettle
• Kettle reboiler is a type of horizontal exchanger. It typically has amulti-pass tube bundle located along the bottom and an over sizeshell providing excess space above the bundle for vapor liquiddisengagement.
• A vertical dam keeps the tubes covered with liquid at all times.Non vaporized liquid flows over the dam into a holding area andwithdrawn as distillation tower bottom product under level control.
Kettle
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Reboilers – Internal
• Internal reboilers are inserted directly into distillation tower , therebyeliminating the shell and process piping costs.
• They are useful where only moderate or small heat transfer areasare required.
Internal reboiler
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Plate heat exchangers (PHE)
• PHE are high heat transfer surface exchanger.
• They consist of a series of gasketed plates, sandwiched togetherby two end plate and compression bolts.
• The channels between the plates are designed to creaseturbulent flow so high heat transfer coefficients can be achieved.
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Plate heat exchangers (PHE)
• As hot fluid enters the hot inlet port on the fixed end cover of PHE,it is directed into alternating plate sections by a common discharge
header.
• As cold fluid enters the counterflow cold inlet port, it is directed intoalternating plate sections. Cold fluid moves up the plates while hotfluid flows down across the plates.
• Heat energy is transferred through the walls of the plates byconduction and into the liquid by convection.
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Air cooled heat exchangers
• They compose of a structured matrix of plain or finned tubesconnected to an inlet and return header .
• Rectangular tube bundle contains several rows of tubes on atriangular pitch arrangement. The hot fluid entering at the top rowof the bundle and air flowing vertically upward through thebundle.
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Air cooled heat exchangers
• Air cooled heat exchanger are used when the use of cooling wateris impractical due to high process temperatures.
•
The two most common types of Air cooled heat exchanger use inchemical plants are:
1. Forced-draft type, where air is pushed across the tube bundle.
2. Induced-draft type, where air is pulled through the bundle.
Force draft Induced draft
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Week 7 Class Test (Tue during lecture)
•Topic 1, Topic 2, Topic 3.1
•Test duration: 1 hour
•TEN (10) questions in Section A – Fill in the blank
•THREE (3) questions in Section B – calculationsand explanations
• Answer all questions
•Equations for calculating pump Liquid Horsepower
and capacity of a rotary pump will be given• All other equations will not be given
•Unit conversion factors will be given if needed
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• A fired heater or furnace is a direct-fired heat exchanger that uses theflame and hot gases (flue gas) ofcombustion to raise the temperatureof a process fluid flowing through
coils of tubes that run along the insidewalls and roof of the heater .
• The combustion happen in burners and the hydrocarbon fuel used forburners can be in gaseous or liquidform.
• The primary modes of heat transfer ina fired heater are radiation andconvection; however, heat must passthrough the tube walls by conduction to be absorbed by the fluid flowing
inside the tubes.
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Radiation& Convection
Conduction
Convection
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Combustions• Combustion is a rapid chemical reaction that occurs when theproper amounts of fuel and oxygen in the air come into contactwith an ignition source and release heat and light.
• Fired heaters use combustion reaction of hydrocarbon fuel in
burners to provide heat for heating of process fluids.
• Complete combustion occurs when the hydrocarbon fuel and airare in correct proportions, and all the fuel is converted to waterand carbon dioxide. Complete combustion is desirable duringfired heater operations. CxH2y + (x+y/2)O2 ---------> xCO2 + yH2O
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Incomplete combustion:
• Incomplete combustion can occurs in fired heaters wheninadequate oxygen exist, caused by insufficient supply of air to theheaters. This leads to presence of unburned fuel and production of
carbon monoxide in the heaters.
• Incomplete combustion is undesirable as it wastes fuel, unburnedfuel and carbon monoxide produced can cause after burning whichcan lead to wall, tubes and stack damage, scaling on tubesexternal by carbon black particles can reduce heat transfer , andflame impingement can occur due to elongated flame resulted frominsufficient oxygen.
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Flame impingement:
• Flame impingement refers to the burner flames touching the tubes and the wall of the furnace. Generally, in any heater, the flameshould be as short as possible to give uniform temperature in the
heater and prevent flame.
• Flame impingement on the tubes causes local overheating ofprocess fluid flowing through the tubes. For hydrocarbon fluids,decomposition and coke formation will occur inside the tube andcan lead to mechanical failure of tube wall.
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High tube wall temperature aspoor heat removal by fluid flowinginside tube due to coke formedinside tube
lead to
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Flame impingement:
After burning
• After burning is the delayed combustion of air and unburned fuel
in the upper section of the heater due to air leakage at thatsection. After burning can cause damage to the walls, tubes andstack .
Flame impingement
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After Burningcan occur if there isair leaking in atconvection section
Incomplete combustionresults in unburned fuelin flue gas.
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Theoretical air and Excess air
• In heater operations, theoretical air refers to exact amount of air,based on chemical reaction equation, that will completely convert
all the fuel to water and carbon dioxide.
• To assure completion combustion, amount of air supply to theheater burners must be above the theoretical air , the mount of airexceeded the theoretical air is call “excess air” which is expressed
as % excess.
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CxH2y + (x+y/2)O2 ---------> xCO2 + yH2O
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Theoretical air and Excess air
• Excess air increase the amount of oxygen and the probability ofcombustion of all fuels. Typical excess air to achieve good heateroperations are 10 – 15 vol% excess for natural gas, 15 – 20 vol%excess for fuel oil.
• In theory, the most efficient combustion is achieved by keeping theexcess air as low as possible. However, low excess air is limited
by:Reaching incomplete combustion
Obtaining poor heat distribution among burners
Establishing an unstable and long flame pattern
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Heating value of fuels
• Different fuels release different amount of heat energy as they areburned. The heat energy referred to as the net heating value (orcalled low heating value, LHV) is measured in Btu per volume orper mass or per mole. For example, hydrogen has the LHV of 274Btu/ft3, 51596 Btu/lb whereas CH4 has a LHV of about 909 Btu/ft3,
21522 Btu/lb.
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Fire Heater Sections:• Fired heaters come in a variety of shapes and sizes, havedifferent tube arrangements and feed inlets, burn differenttypes of fuels and have different burner design. However, theydo have sections in common which are:
1. Radiant section
2. Shield section
3. Bridgewall
4. Convection section
5. Breeching
6. stack
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Radiant section:
It is where heater fire box located. Firebox contains burners and it’s wall is lined with a refractory layer that reflects heat back into theheater . The radiant tubes, either horizontal or vertical, are locatedalong the walls of the firebox and receive radiant heat directly from
the flame and refractory wall. Heat is transferred by radiation fromflame and wall, convection by flue gas, and by conduction throughthe tube wall to process fluid flowing inside the tubes. Sight doorsare provided at firebox wall for operators to check flame pattern andfirebox conditions.
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Bridgewall: This is the area between radiantsection and shield section. Several importantmeasurements are normally made atbridgewall, e.g. bridgewall temperature is thetemperature of the flue gas after the radiant
heat is removed by the radiant tubes andbefore it enters the convection section.
Measurement of the draft (negative pressureinside heater) is also important since thisdetermines how well draft in the heater is set
up.
This is also the ideal place for flue gasoxygen and ppm (parts per million)combustibles measurement.
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Shield Section: This is above the radiantsection, and contains two rows of bare tubes(without fins or studs) which shield theconvection section tubes from the directradiant heat.
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Convection section: This section is located in the upper part of theheater , immediately above the shield section. At this section, fluegas heat is transferred to the tubes by convection and throughtubes wall by conduction. The tubes are usually finned type orstudded type to increase heat transfer area.
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Breeching: The transition from the convection section to the stack iscalled breeching. Measurement of stack emissions for compliancepurposes is normally made at breeching.
Stack: As the flue gas contains combustion by products such asNOx, SOx, stack is necessary to discharge flue gas at height in theatmosphere such that they cannot endanger personnel and thatpollution requirements are met.
Stack Damper : Stack damper at the stack inlet permits adjustmentof heater drafts.
Stack Damper
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Draft
• Draft is defined as the negative pressureof the flue gas measure at any pointwithin the heater .
• Negative pressure or draft occursbecause the hot flue gas within theheater is less dense than thesurrounding atmospheric air .
• The greater the difference in densities,the greater the draft or negativepressure within the heater.
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Draft
• The difference in densities causes air toflow into the heater through the burnersor through other openings, and the hotflue gas to flow out of the heater .
• In this manner the movement of cooloxygen containing air through the heaterbecome continuous.
• The control of draft or flow of air throughthe heater is by damper placed at heaterstack inlet In process plants, stackdampers resemble huge butterfly valvesand require only one quarter turn to be
100% open or close.
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Flow of air into heater causes by draft
Cool AirCool Air Hot flue gas
Low Pressure
High Pressure
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Burners:
• Air enters through a muffler whichdampens the noise from the burners.
•
The plenum (windbox), distributes air tothe burner throat and dampens thenoise from the firebox.
• The burner tile is a refractory piece thatshapes and stabilizes the flame.
• One or more burner tips are used toinject fuel into the air stream. A smallpilot burner provides an ignition sourcefor the main burner.
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• Burners can be classified by their flame shape as well, the twomost common flame shapes are round and rectangular .
Round Flame Burners Rectangular Flame Wall-Fired Burners
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Burners:
• Many refinery and chemical plants useboth liquid and gas fuel for the heaters.For such heaters, combination gas/oilburners will be used.
• Firing a liquid fuel requires atomizationof the liquid. Breaking liquid fuel intosmaller droplet allow fast surfacevaporization, providing the required gasphase for mixing with the air during
combustion.
Oil Gun Atomizationof liquid fuel
Atomization steam
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Burners:
• Atomization of liquid fuel is done by oilgun. Most oil guns have a concentrictube design in which oil flow through theinner tube while the atomizing medium,
steam, flow through the annular between the inner and outer tube. Fuelatomizers provide proper mixingbetween the oil and steam in oil burners
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Atomization in Oil Gun
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Flame patterns:
Pilot Flame Oil Firing Gas Firing
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Pilot Burners:
• Pilot burners are small, independentlycontrolled burners that act as an ignitionsource for the larger process burners.
• Pilot burners are predominantlypremixed. The mixer which premixes theair and fuel, is located externally to theburner housing, so the combustion airfor the pilot burners is typically ambientair.
Premix gas pilot
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Flame out protection:• To prevent forming of explosive air/ fuelmixture inside heater , flameoutprotection is required for each burner ina heater. This is usually accomplished
by using gas-fired continuous pilot.• The main function of a continuous pilotis to ensure a safe source of ignitionalways available for re-ignition of mainburner.
•
For such pilot burner, pilot flameoutdetection is accomplished by usingflame rod. In the event that pilot flame isout, a safety system will shut off the flowof fuel to both the main and pilot burner .Pilot fuel
Main burner fuel
shut off valve
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