1
FIRED PRESSURE VESSEL
CHAPTER 4
4.0 Fired Pressure Vessel
2
4.1 Boiler
4.2 Furnace
4.3 Reactors and Reformer
Learning Outcome

At the end of this session students should be able to
1. Describe the various types of direct fired heaters. (C2)
2. Describe the basics operation of fired pressure vessel.(C2)
2. Describe main components of a boiler, furnace, reactor and
reformer. (C2)
3. List some boiler operating problems. (C1)
4. Describe different types of furnaces. (C3)
4.1 Boiler
Definition - Steam boiler is a closed vessel in which steam is
generated under pressure greater than atmospheric pressure
 Purpose - It is a device which generates

 steam for power, processing or heating purposes
 hot water for heating purposes
 hot water supply

Two categories of application for the energy contain in steam
 Converted to work for example steam engine and turbine
 Used as a heat source for example heater and heat exchanger
Boiler Types

2 major type of boiler
 Water tube
 Fire tube

Based on location of water and hot gaseous in tube
Water Tube Boiler
The source of heat is located outside of the tubes
 The water to be heated will flow inside the tubes and absorb the heat from
outside the tube
 It should be noted that all tubes must be filled with water and not steam
 It preferred when large capacities of steam are required and also when the
pressures and temperatures are high

Water Tube
9
Fire Tube Boiler
Hot gaseous products of combustion pass through the boiler tubes which
are surrounded by water
 The water to be heated surrounds the tubes
 All tubes must be completely immersed inside the water at all times
because it may overheat and rupture

Boiler Type

Based on construction or design
 A type
 D type
 O type

Refer to water tube boiler
A - Type

One steam drum and two mud drum located in an A pattern with
steam drum at the above and the mud drum at the bottom
D - Type
Steam drum and mud drum are located directly above one another and
off to one side of the furnace in D pattern
 A series of tubes run vertically between the mud drum and steam drum
 The rest of the tubes extend horizontally from the steam drum and mud
drum to the furnace wall at which point they become water tube

O - Type

In this arrangement the steam drum is also located directly above the
mud drum but both are located in the center of the boiler and the
connecting tubes are in an O pattern
Boiler Type

Based on source of fuel
 Solid
 Liquid
 Gas
 Electric
 Nuclear
Boiler System Consist Of
Feed water system
2. Fuel system
3. Steam system
1.
BURNER
❖ Function:
- Mixing oil and air in proper proportions.
- To produce heat by combustion of fuel & air.
- Forced Draft air is forced in to combustion chamber.
❖ Design:







Fully automatic & step less modulating (20 to 100%)
High pressure atomizing (jet),means oil is atomized by nozzle
and vaporization occurs in combustion space.
Forced draught combustion air blower with motor
Nozzle
Ignition transformer with electrode
Solenoid valve
Photocell operated safety device
COMBUSTION

High speed fuel oxidation that produces light, heat & flame.
Three necessary components require for combustion:
Ignition
1. Oxygen ( Air)
2. Ignition
Combustion
3. FUEL
Triangle
Oxygen

Four important factors that control combustion
1. Air supply
2. Mixing of fuel and air
3. Temperature
4.Combustion time
fuel
BOILER MOUNTINGS
❖
Boiler mounting are required for
➢
the complete controlling of steam generation,
measurement of some of the important properties of
steam,
provide safety to the boiler
➢
➢
❖ Following mountings should be fitted
to the boiler,
1.
Two safety valve:
Function : To blow off steam when
the pressure in the boiler
exceeds the working pressure.
2. Two water level indicators:
Function: Indicate the water level in boiler.
Also level transmitter used for display the
water level in boiler.
3. Pressure gauge:
Function :Indicates the pressure of
steam in boiler.
4. Steam stop valve:
Function:To stop the flow of steam
from the boiler to main
steam header.
5. Feed check valve:
Function:Control the supply of feed
water to boiler & also acts as
a non-return valve.
6.Blow down valve:
Function:continuous use to control the
concentration of dissolved
solid in boiler water.
7.Fusible plug:
Function:To protect the boiler
against damage due
to over heating
caused by low water
level in boiler.
8. Man hole & Mud hole:
BURNER TRIP
 Mobery controller :boiler water level
low & extra low
 Photocell :flame failure
 Flue gas temp.high
 Burner return oil pressure high
 Ring main pressure low
 Furnace oil temp.low- OPH outlet
 Flue gas outlet damper closed
 Instrument air pre.Low
 Furnace oil supply pre.Low
BOILER CONTROLS
Sequence control
 Feed water level control
 Pressure (firing ) control
 Trim control
 Blow down control

Performance Evaluation of Boilers
•
The performance parameters of boiler, like efficiency and
evaporation ratio reduces with time due to
– poor combustion,
– heat transfer surface fouling and
– poor operation and maintenance.
OPERATION

Water Tube
Basic Operation
Water from dearator comes into upper drum through feed water
 Water travel from upper drum to lower drum through tube called
downcomer
 Dissolved solid will settle in lower drum and discharge by blowdown
valve
 The burner will heat the water in tube called riser
 This will increase the water temperature and pressure

Basic Operation (continue)
High temperature water will rise to upper drum and produce steam
 Steam and water will separate in upper drum by steam separator
 Steam will go out through super heater to get dry steam
 Dry steam now can used either to used for turbine or other process
 These process continue and water will circulate in the boiler

OPERATION

Fire Tube
Basic Operation
The flame from burner will heat the combustion chamber and hot
gaseous flow through the tube
 The water outside the tube and combustion chamber will heat and the
temperature of the water increase
 These will produce the steam at the upper of the drum
 Steam flow through steam outlet to other process

OPERATION

Boiler Startup
 What equipment must start
 To ensure smooth operation
 To uniform the heated and pressured of boiler
 Step to start the boiler
 Boiler safety
OPERATION

Boiler Startup
 Open all steam drain and close all blowdown
 Start the draft system and purging the boiler
 Start the first pilot and first burner at minimum firing
 Slowly rising the pressure and temperature not more than 500C per hour
 Close all vent air and steam drain
 Open steam stop valve slowly
 Open boiler continuous blowdown
 Start chemical injection system
OPERATION

Boiler Shutdown
 What to do to stop the boiler
 Cooling down
 Depressured the boiler
 Boiler safety
OPERATION

Boiler Shutdown
 Reduce firing slowly to minimum
 Take off burners (shut off fuel)
 Keep draft running for purging
 Stop draft and open damper
 Open all vent and drain at pressure 2 bar
 Close steam stop valve
 Isolate electrical supplies
OPERATION

Boiler In Operation
 What to control for smooth operation
 Checking
 record
OPERATION

Boiler In Operation
 Test gauge glass
 Clean fuel strainers and burners
 Check flue gas outlet temperature
 Check combustion condition
 Blowdown as instructed by chemist
 Record important parameter
 Check all joint tightness
 Record all activities in log book
OPERATION

Boiler Blowdown
 Continuous or top blowdown
◼ To control the level of total dissolved solids
 Intermittent or bottom blowdown
◼ To remove accumulated sludge and sediment
WATER TREATMENT
Important to prevent boiler failure
 Water from river (source) to boiler
 External or Internal treatment

Water Treatment

2 condition of water
 Feed water condition
 Boiler water condition
Water Condition

Feed water condition
 Hardness
 pH
 TDS
 Chloride
 Alkalinity
(< 5 ppm)
(6.8 – 7.5)
(> 100 ppm)
Water Condition

Boiler water condition
 Hardness
 pH
 TDS
 Silica
 Iron
 Phosphate
 Sulfate
 Chloride
 Caustic Alkalinity
(< 2 ppm)
(10 – 11)
(< 2000 ppm)
(< 150 ppm)
(< 2 ppm)
(20 – 40 ppm)
(40 – 60 ppm)
(300 ppm)
(300 – 600 ppm)
External Treatment
Clarifier
 Filter

 Pressure
 Carbon
Softener
 Dearator

 Vacuum
 Pressure
Internal Treatment
Injected chemical in water
 Phosphate

 Remove dissolved oxygen which caused pitting

Sulfate
 Prevent formation of scale deposit

Alkalinity
 Raise pH to control corrosion

Sludge Conditioner
 Prevent other scale and deposit on boiler surface
Softener
To remove the ion mg content in water
 A unit of vessel content of Resin
 The resin absorb mg ion content
 Can be backwash to remove the dirt or to active the resin
 Can be regenerate to add power of the resin

Dearator
Many type either pressure or vacuum and either vertical or horizontal
 Fitted with sprays arranged to remove oxygen, carbon dioxide and
other gases by scrubbing action of steam
 Located before inlet boiler feed pump

Maintenance

Two type of maintenance
 Corrective Maintenance
◼ Is a daily working procedure for which every person who involved with boiler
◼ Either during start up boiler or boiler still running
◼ Repair work
 Preventive Maintenance
◼ Checking or visual inspection
◼ Planning or schedule to repair
Testing
Boiler shall tested from first fabrication until finish and also during
operation
 The most important testing is called Hydrostatic Test (HT)
 Every boiler must HT every 8 years operation

Failures
Boiler fail because of poor water treatment and poor operation
 Type of failure





Bursting Tube
Drum Surface
Leaking
Three courses to failure



Corrosion
Deposit
Overheating
Safety
This is important and precaution either the boiler stop or running
 Working in high temperature and high pressure
 All work shall refer to the competent person and Factory and
Machinery Act
 Competent Person

 Steam Engineer
 Engine Driver
FURNACE
Reaction Furnaces
A simply fireboxes containing an
arrangement of tubing through
which the reactant stream is
passed.
 A fuel and air mixture is
introduced into the brick lined
firebox, which provides the heat
for the reaction in the tubes.
 Most furnaces used for crack
hydrocarbon

Exothermic reaction
Exothermic reaction are characterized by a chemical reaction
accompanied by the liberation of heat.
 Three (3) ways to control the reaction.
 Control the reactant flow rates
 Remove heat
 Provide cooling to the reactions.

REACTOR
Reactor
Definition – Reactor is a vessel in which a controlled chemical reaction
takes place.
 Basic types of reactor
i. Stirred tank reactor
ii. Fixed bed reactor or converter
iii. Fluidized bed reactor
iv. Tubular reactor
v. Furnaces

Stirred Reactor
A common type of reactor.
 The basic components of the
device will include a mixer.
 The stirred reactor is designed to
mix two or more components into
a homogenous mixture
 As these components blend
together, chemical reactions
occurs that creates a new
product

Fixed Bed Reactor
Often called as converter.
 It is a vessel that contains a mass of small
particle.
 The mass usually a packed “bed” of catalyst
which promotes the reactions.
 As the process medium passes through the
catalyst, the reaction occurs.
 The main reason for arranging the packed
beds in a configuration other than the large
single bed are to provide better heat
transfer, to provide better distribution of the
reaction mixture through the converter

Fluidized Bed Reactor
A fluidized bed reactor suspends
solids by the countercurrent flow
of gas from the bottom of the
reactor.
 Over time, particles segregate
as heavier components fall to the
bottom and lighter ones move to
the top.

Tubular Reactor
A heat exchanger in which a
chemical reaction takes place
 Used for chemical synthesis.
 Used for liquid and gaseous
reactions.

THE END
See You Soon