Analysis of Power Generation Plant at Pakistan Steel Mills

Pakistan Steel Mills
“Thermal Power Plant”
Visit Report
Group Members:
 Waleed Ahmed ME-071
 Talha Fareed Khan ME-072
 Abdul Rafay Khokar ME-073
 Syed Wajahat Hassan ME-075
 Danial Sohail ME-089
 Syed Osaid ul Haq ME-102
 Daniyal Iqbal Khan ME-103
 Owais Ali ME-105
 Syed Wajahat ME-106
 Muhammad Hasan ME-108
 Rafay Mustafa ` ME-124

Thermal Power Plant Pakistan Steel Mills
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Preface / Acknowledgments
Relating theoretical knowledge with practical experience is important as it enhances concepts
and this is reason, why engineering students are advised to visit industries and relate their
theoretical knowledge with industrial practices.
Instructed by course instructor of “Steam generation and steam turbine” students had to visit any
industry with its own Power generation capability, in groups, and to present their learning in
form of reports. As a result we managed a visit to Pakistan Steel Mill, which has its own Power
generation plant with production capacity of 155 Mw.
This report presents a brief description of Russia made power generation plan implied by PSM’s
Thermal Power Plant. It briefly discuss every component in plant along with detailed description
of boiler and turbine, main components related to our course SGST, it also presents some
recommendations that according to our point of view, should be applied by PSM to their plant in
order to increase overall efficiency and to reduce damages occurring to boiler due to scale
formation in tubes.
All in all this report provides its reader an overview of Power generation and also gives an
insight to an engineering student about technologies of mid 70’s as Russia installed this power
generation plant in 1973.
This visit helped a lot to boost our knowledge about Steam Generation and Steam Turbine, but
this would be impossible without help Mr. Shamsi and Engr. Shakeel Ahmed, who organized
this visit for us and helped us throughout our visit. We also want to thank Mr. Izhar ul Hasan
(deputy manager) who illustrated and demonstrated every component of power cycle and onsite
made it easy for us to understand function of individual component.

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Table of Content
S.no Contents Pg. no
1. Thermal Power Plant - Pakistan Steel Mills 3
2. Power Generation Cycle 4
3. Water chemical treatment plant 5
4. Furnace Fuel 9
5. Boilers 10
6. Turbines 16
7. Turbo blower station 17
8. Recommendations 18
9. Source of information 20

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Thermal Power Plant - Pakistan Steel Mills
When project of PSM was approved by Govt. of Pakistan in 1970’s it also included PSM’s own
Power generation Plant. This power generation project was included because consumption of
electricity at PSM was going to be too high that electricity from K.E grid would have cost a lot to
fulfill demands of PSM. This demand of electricity is due to high capacity blowers, compressors
and other plant equipment which fire up PSM’s furnaces, not only this but area occupied by PSM
is like a small city and all these power requirements are fulfilled by Thermal Power Plant at
Pakistan Steel Mill.
Another reason for installing a power plant was availability of fuel. PSM produces Blast Furnace
Gas, Coke Oven Gas and Coal Tar as by product of steel making process. All these by-products
can be used as fuels and burning these fuels to produce electricity reduces plant operating cost.
All these fuels have low market value because of its quality, but PSM’s power plant furnace is
capable of burning these fuels. In short PSM utilizes it’s by product to get electricity.
PSM’s Thermal Power Plant (TPP) has total electricity production capacity of 155 Mw. 4 Russia
made natural circulation water tube boilers produces steam to drive 4 turbines, three 55 Mw
turbines are used for electricity generation and fourth 60 Mw turbine is used to drive compressor
at Turbo Blower Station (TBS).
Water Chemical Treatment Plant WCTP provides de-mineralized water to boilers and residual
steam from turbines is supplied as process heating in different departments of PSM and some
amount is utilized to drive turbine in TBS.

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Power Generation Cycle:
WCTP at TPP provides de-mineralized water to boilers, capacity of each boiler is 220 tons/hr,
and boiler provides super heated steam at a temperature of 560 o
C.
Boiler utilizes 2 Forced draft and 2 Induced draft fans for supply and suction of fresh air and flue
gases respectively. Each boiler have 8 burners for burning fuel, it can burn 4 different kind of
fuels, but PSM mostly use Natural Gas for firing furnace because of its good Calorific value and
less cost.
From boiler steam is supplied to turbine for power production, turbine rotates and provides shaft
power and this shaft power is converted into electricity from generators, electricity from
generators is supplied to M.S.G.R where it is connected to K.E grid.
Turbines have extraction points for Feed water heater, which pre heats water entering boiler,
residual steam from turbine is supplied to TBS where another turbine is driven and its shaft
power is used to drive a compressor for blowing air into furnace. Rest of residual steam is
supplied to different departments in steel mill where it helps in processes like rolling, forging etc.
Some departments of steel mill also have small scale boilers therefore they use condensate from
TPP as feed water because of its de-mineralized nature.
Condensate from TBS and other departments of PSM reaches WCTP where it is again treated
completely because fewer precautions are taken during transfer of condensate and it has lost its
de-mineralized nature. From WCTP water is taken to boiler and cycle continues.

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Water Chemical Treatment Plant (WCTP):
It is designed to meet the following demands;
 De-mineralized water for steam generation purpose
 Soft water for plant technological needs.
 Steam condensate cleaning to treat the contaminated condensate received from different
shops (TPP & TBS).
Processes in Water Chemical Treatment Plant
(WCTP):
CLEARIFIER
Lime
coagulated
storage
Mechanical
filter
Rear
Pump
Primary Cat-
ion
exchanger
Secondary
Cat-ion
Exchanger
Secondary
An-ion
Exchanger
Storage
Water
tank De
Carbonizer
Primary An-
ion
Exchanger

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Stages of Water Treatment:
The process of water treatment may be divided into the following stages;
 Cold process softening by liming followed by clarification added with coagulation to
remove mechanical and organic suspended particles
 Mechanical filtration
 Softening by ion-exchange to reduce hardness of water.
 Demineralization to remove all dissolved salts from water by treating it in a series of cat-
ion and anion exchangers
 Degasification (de-carbonization) to reduce the concentration of dissolved CO2 in water.
Raw Water Treatment Scheme at WCTP:
It consists of following steps;
 Pre-heating Of Water:
Raw water is pumped to the WCTP by two lines up to the inlet of four raw water inlet booster
pumps. From here the water is pumped to the main building (TPP) where it is heated up to 36-40
C in raw water heaters.
 Clarifier:
A pair of pipelines carries water to (TPP) and another pair carries it back to Clarifier at WCTP.
Here liming and coagulation is carried out simultaneously in order to remove magnesium and
calcium temporary hardness present in soluble form by converting them to less soluble
compounds. Hydrated Ca(OH)2 and coagulant ferrous sulphate (FeSO4.7H2O) are used for this
purpose.
The following are the reactions;
Ca(HCO3)2 + Ca(OH)2 = CaCO3 + H2O
Mg(HCO3)2 + Ca(OH)2 = MgCO3 + CaCO3 + H2O
MgCO3 + Ca(OH)2 = Mg(OH)2 + CaCO3

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 Mechanical Filter:
Now clarified water is pumped into the double chamber mechanical filter. Here all the suspended
materials are removed mechanically by passing the water through chamber of coal. After this
filtration water is divided in to two parts one is given to sodium-Anion exchanger and other is
given to Hydrogen-Cation exchanger.
 Sodium Cat-ion Exchanger:
In sodium ion exchanger remaining calcium and magnesium cations that are hard to remove are
exchanged by sodium cations known as “sulforated coal” this is a Na-Cycle. At the exhaust of
ion exchange capacity the Na-cation exchangers are regenerated with a 3-6% solution of
common salt NaCL.
 Primary Cat-ion Exchanger:
The second steam coming out of a mechanical filter is treated in hydrogen-cation exchanger .
Here the calcium, magnesium and sodium cations of water soluble salts are exchanged by
hydrogen-cation of H-carbon exchange material. Regeneration of H-carbon exchange material of
this stage is carried with 1.5-2.2% sulfuric acid solution.
 Primary Anion Exchanger:
Acidic water of H-carbon exchanger led to primary anion-exchanger. This is the first step of
anion exchanger. Here the exchange of anions of strong acids (SO2,Cl2,NO3) takes place with
the OH- ions of exchange resin. At the end it is regenerated with 2-4% aqueous sodium
hydroxide NaOH.
H2SO4 + KOH = H2O + KSO4
HO + KOH = H20 + KCL
HNO3 + KOH = H20 + KNO3

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 De-carbonizer:
After this ion exchange two pipe lines take this water to decarbonizer units. Decarbonizer is
filled with 1 inch porcelain “rashing rings”, dumped into cylindrical shell in order to increase
water and air surface contact area to effect degasification. Carbonic acid H2CO3 formed during
H-Cation exchange is decomposed by spraying the water from the top.
H2CO3 = CO2(g) + H2O
 Secondary Cat-ion Exchanger
Two decarbonizer water collecting tanks V=200m3 at the bottom of decarbonizer collect this
water. From these tanks it is pumped into 2nd
stage H-cation exchanger. The H-Cation replaces
remaining traces of sodium as well as calcium and magnesium cations of different salts from
water with their H-Cation.
 Secondary Anion Exchanger:
After the ion exchanger in secondary H-Cation exchanger the water enters a final stage of ions
removal called secondary anion exchanger. Here a strongly basic anion exchange resin AB-17
exchanges the ion of week acids H2CO3 & H2SiO3. The ion exchange resin of of secondary
cation exchanger is regenerated with 3.5-5.5% sulfuric acid and that of secondary anion
exchanger with a solution of 4-4.5% sodium hydroxide.

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Fuels
Fuel is one of most important consideration when designing boilers because of day by day
increasing cost of fossil fuels. Special attention was given to this perspective when boilers of
thermal power plant at PSM were designed, boilers were designed in such a way that it doesn't
rely completely on fossil fuel but can also work with fuels obtained as by-product of steel-
making process. These boilers can burn Natural Gas, Blast Furnace Gas, Coke Oven Gas and
Coal Tar, where blast furnace gas and coke oven gas is by-product of different metallurgical
process at PSM.
Calorific value of above mentioned fuel is as follows:
Calorific value (Kcal/m3/hr)Name of gas
8400Natural gas
880Blast furnace gas
8900Coal tar
4600Coke oven gas
Calorific value while dealing fuels in boilers is important in determining flow rate of steam
exiting boiler, lower CV gives lower flow rates. Because of limited burning capacity of fuel in
furnace.
Given boiler gives following steam flow rates while burning different fuels:
 While burning blast furnace gas: - 135 tons/h.
 while burning natural gas :- 220 tons/h
Furthermore; availability of Coke oven gas and Blast furnace gas has decreased because of
decrease in production at PSM, only 10% of total capacity nowadays, therefore these fuels
individually does not fulfill demand of boiler and Coal Tar produces ash which needs to be
removed from time to time. Therefore boiler furnace works on mixture of coke and natural gases,
and mixture of coal tar and blast-furnace gas for better burning with better Net Calorific Value of
fuel along with fulfilling requirements of boiler.

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Boiler
In order to fulfill power requirements of Pakistan Steel Mill, electricity generation plant was
setup with capacity of producing 165 Mw of power through three 55 Mw Steam Turbine
accompanied by 3 Russia made boilers for producing super-heated steam at a rate of 220 tons/
hour each. Not only electricity is generated but residual steam is utilized to run another turbine
which drives compressors directly in Turbo Blower Plant, and is also used as purified feed water
for boilers in different departments of Steel mill.
Boiler Type and Specification:
Boilers are high pressure water tube boilers with Natural Circulation, as mentioned in their
model number: TIM-159/CO, where CO denotes Natural Circulation of water inside boiler due
to pressure head.
Capacity 220 tons/hour
Steam Pressure 100 kgf / cm2
Super-heated steam temperature 540 o
C
Total Heating area 19393 m2
Feed Water Pressure 160 kgf/ cm2
Boiler Structure:
Boilers basic structure is a ∩ shaped where one shaft is up-stream flue gas duct called Furnace
or Radiation Shaft, special arrangements are at roof of boiler for super-heated steam, and other is
downstream shaft call Convective Shaft with an exit for flue gases into air preheater at bottom of
shaft.

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Schematic showing basic boiler components along with flow direction of water (green) and steam (red)

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BOILER FURNACE:
Boilers furnace is versatile type furnace with ability to burn four different kinds of fuel through 8
burners located on radiation shaft different burners. These fuels include Natural Gas, Blast
Furnace Gas, Coke Oven Gas and Coal Tar. Not only individually using these fuels, furnace can
also work with mixture of coke and natural gases, and mixture of coal tar and blast-furnace gas
for better burning with better Net Calorific Value of fuel.
All eight burners are placed on up-stream radiation shaft in such a way that 4 burners are on one
side of shaft and other four on other side. As shown in following figure:
Burners located on upper side are designated to burn Natural Gas and Coal Tar while lower
burner use Blast furnace gas and Coke oven gas as fuel.
Amount of gas that can be burned by burners according to fuel used is as follows:
Fuel Burning Capacity
Natural Gas 4000 m3
/ hr.
Blast Furnace Gas 25000 m3
/ hr.
Coke Oven Gas 3875 m3
/ hr.
Coal Tar 1.2 ton/ hr.

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Regenerative air heaters:
Burning large amount of fuel requires a large amount of air. Air is supplied to furnace through 2
Forced draft fans and is sucked into Regenerative Air heaters through 2 induced draft fans.
Each F.D fan forces fresh air at a rate of 60,000 m3 / hr. into R.A.H, where fresh air is heated
through flue gases exiting boiler. Flue gases exits boiler at a temperature ranging from 230-270
C and drops its temperature to 150 C in R.A.H, where as fresh air enter R.A.H. at 40 C and exits
R.A.H at 220 C.
Regenerative air heaters have two vertical columns. Fresh air from F.D fans travels in one
column and flue gases from boiler travels in other column. Air heater fan is placed in such a way
that it intersects the two columns. Air heater fan travels from one column to another column
without allowing two gases to mix into each other. Fan absorbs heat into its fins due to higher
temperature of flue and dissipates its energy into low temperature fresh air region. Speed of air
heating fan ranges from 2-3 rpm.
Feed Water Economizer:
Water before supplying to steam drum for evaporation cycle is heated to raise its temperature,
feed water economizer is placed at bottom of radiation shaft when flue gases have lost most of
their energy content and have less temperatures for producing super-heated steam, therefore that
energy is utilized in preheating water.
Lower Headers:
Below furnace of boiler are Header known as lower headers, here saturated water is collected
before sending it to water walls for heating, they acts as mud drum in boilers, TIM 159/CO has
14 lower headers in total with 4 located on wider side of boiler while rest are on other side of
boiler.
Distribution of risers in headers is as follows:
Header Location Number of headers in that
location
Numbers of tubes in each Header
Left 3 35
Right 3 35
Front 4 32 (2) and 38 (2)
Rear 4 32 (2) and 38 (2)

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Upper Headers:
These are chambers at top of furnace where steam and water is collected from risers and water
walls, and steam is forwarded to Steam drum whereas water recirculates till it becomes steam.
There are 14 upper header in all positioned in same manner as lower header but number of down
comers is less than number of risers, water comes down to lower header through 44 tubes.
Steam Drum:
From upper header steam is directed to steam drum located above the radiation chamber. Here
steam is separated from carryover through cyclone separators and remaining water is brought
back to lower headers for recirculation. Steam pressure inside steam drum is 100 Kgf / cm2
(98
bars). Saturated steam from steam drum enters Ceiling Super heaters.
Ceiling Super Heater and Screen Super Heater
In ∩ shaped boiler, portion connecting ceiling of radiation shaft with ceiling of convective shaft
is covered with ceiling super heater. for further heating steam from ceiling super heating enters,
these are vertically hanging tubes located at horizontal shaft connecting radiation and convective
shafts.
De Super heaters
Superheated steam from Screen super heaters enters De Super Heater, it reduces/regulates
temperature of steam especially when boilers is working on partial load to avoid damages to
tubes and components.
Condenser:
Function of condenser is to form condensate for de super-heaters.it is located outside but on the
top of boiler plant. It consist of cylindrical steel shell in which feed water tubes are passing
through, and is connected to boiler drum by two pipes through which steam is provided. Here
steam transfers its energy to feed water, it gets preheated, and steam condensates to liquid water
which is free from all impurities.
Suspension Super Heater:
Steam from De super heater enter Suspension super heater, these are horizontal pipes containing
steam for super heating, place in such an order that a only a little space is present in between
pipelines so that flue gases get forced over its surface and maximum heat transfer take place.
Suspension super heater gets its name from face that these tubes are suspended with help of
clamps in convection chamber.

15 | P a g e
There are two stages of suspension super heater:
● 1st
stage Convective Super Heater or Inlet Packet
● 2nd
stage Convective Super Heater or Outlet Packet
Steam Chest:
Super-heated steam from Suspension super heaters enters Steam chest, a cylindrical drum at top
of boiler. Steam chest is place where steam is temporarily stored before supplying to turbine for
power extraction.
Temperatures of Water and Steam at inlet and outlet of different
Boiler components:
COMPONENT INLEToC OUTLEToC
Suspension System 215 228
Condenser 228 271
Economizer 271 320
Ceiling super heater 320 350
Turning Chamber 350 360
Screen Super heater 360 485
Convective Suspended S.H
(Inlet Packet)
485 540
Convective Suspended S.H
(outlet Packet)
540 560

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Turbines
The TPP operates on a Rankine Cycle. The plant has 3 steam turbines installed. Each turbine
consists of 28 stages, of which, 15 are impulse stages and 13 are reaction stages. 1st
of every
turbine has Curtis blading that is double blades to withstand the impulse force exerted by
incoming high pressure superheated stem from boiler. Labyrinth seal is used as a Seal to seal the
turbines. A generator is installed after each turbine which converts the mechanical energy from
turbine in the form of rotary motion of shaft, into electricity
Turbine Specification
 Two extraction 10-16 atm and 1.5 to 3 atm
 Rated output 60 Mw
 Speed 3000 rpm
 Frequency 50 Hz
 Steam Pressure = 85 – 95 Kg/cm2
 Steam Temperature = 525 – 540 C
 Cooling water flow rate (through Condenser) = 8000 m3/hr
 Cooling water inlet temperature = 28C
 Max steam flow at nominal conditions = 402 ton/hr
Turbine Efficiency
To increase overall efficiency of the power plant cycle, feed water heating is performed. Bled
steam from different stages is used for regeneration.
To maximize turbine efficiency, the steam is expanded, doing work, in a number of stages. These
stages are characterized by how the energy is extracted from them are known as either impulse o
reaction turbines. Most steam turbines use a mixture of the reaction and impulse designs: each
stage behaves as either one or the other, but the overall turbine uses both. Typically, higher
pressure sections are impulsive type and lower pressure stages are reaction type.

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Turbo Blower Station “TBS”
Pakistan Steel is the largest steel making plant in Pakistan, with a production capacity of 1.1
million ton per annum of steel. Pakistan steel mill uses 2 blast furnaces to meet that requirement.
Blast furnace requires hot compressed air for melting iron and for that purpose a turbo blower
station was set up. A fraction of steam (process steam) is taken out the thermal power plant
turbine and fed into a thermal blower turbine which in turn drives a compressor providing
compressed air.
The compressor consists of 4 stages. Those are
 Sucking air from the atmosphere and passing it through a mechanical filter
 Compressed air goes into the cooler
 Comes back from the cooler
 Finally it is blown into the blast furnace.
The cooling water passes through the condenser to remove the heat generated by compressing
gas, at a rate of 8000m3
/hr.
The inlet temperature of cooling water is around 28⁰C.
There are 3 blowers present at the turbo blower station, each compressing air up to 4 atm
absolute pressure. Their specification is listed below.
Specification of turbo blowers
 There are 3 blowers present at the turbo blower station.
 Each blower has 4 stages
 The blowers are run by steam turbine operating at 29 atm pressure
 Each blower has the capacity to produce 1600 Nm3
/min to 2200 Nm3
/min of air for the
blast furnace.
The turbine installed at TBS is Russian made (model no ∩T-60-90/13).The turbine has two
extraction points for steam at 10-16 atm pressure and1.5-3 atm and the rated power output is
60mw at 3000 rpm

18 | P a g e
Recommendation:
De-Mineralization of Feed Water:
In order to deliver pure de-mineralized water to boiler in Thermal Power Plant, WCTP has to
treat condensate steam every time it circulates because of mishandling of condensate in TPP,
TBS and other department of steel mill, which utilizes low quality steam discharge by Power
Plant, cause an overload on WCTP thus decreasing quality of water delivered by WCTP.
Currently WCTP delivers medium quality de-mineralized water to TPP, this medium quality
water is reducing boiler efficiency as well as causing damage to boiler tubes and turbine rotors.
Therefore Pakistan Steel Mill should update WCTP with modern technologies and should install
other plants too for handling such higher flow rates. Listed below are the processes that can be
used to produce de-mineralized water.
 Reverse osmosis
De mineralization of water can be done on industrial scale by using the reverse osmosis
process. RO is similar to osmosis but the only difference is that a large pressure is applied to
make the flow of water against the osmotic pressure. To obtain highly demineralized water,
the process is carried out two times. RO is preferred for large scale purification.
 Nanofilteration
Nanofilteration process can be used along with RO process to obtain high quality water.
Membranes of nanofilters are limited to nano sizes and further purification can be done RO.
Theses process have no heating cost and the separation takes place at room temperature. The
only disadvantage of this process is that the membranes have to be changed after a while and
they are not yet commercially available.
 Distillation
The process of distillation can be used to remove impurities from the water. The process is
carried out by first heating water to its boiling point and collecting the steam in a separate
container. All the suspended impurities are left behind as the water evaporates. However to
obtain a high quality distilled water, the process is carried out twice because certain volatile
oil get mixed with the water droplets during the boiling process. This process is not usually
preferred due to high heating cost.

19 | P a g e
Effective Utilization of Feed Water:
Thermal Power Plant discharge flue gases at 150 o
C, thus wasting a lot of available energy, this
energy can be utilized for better efficiency and maximum utilization of resources, this energy can
be utilized in following ways:
● For distillation of KSWB water for obtaining pure feed water.
● For heating fuel used in furnaces in different department of Pakistan Steel Mill.
● For heating raw water in WCTP to optimize it for best chemical reactions.

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Sources of Information:
 Boiler Structure diagram by Russian engineer
 PSM official website
 Notes by Site engineer at TPP
 Turbine handbook
 Notes by engineer at WCTP

Analysis of Power Generation Plant at Pakistan Steel Mills

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