Production of 5000 TPD of “Direct Reduced Iron”(DRI)

Project AdvisorEngr. Zia -ul-HaqSession: 2009-2013Group members:

Waseem-ur-Rehman 09-CH-02M.Faiq Ilyas 09-CH-10Muddsir Munir 09-CH-38M.Yasar Zia 09-CH-98M. Kamran Hyder 09-CH-104

Presentation Sequence

• Introduction• Comprehensive Flow Sheet• Overall Material Balance• Overall Energy Balance• Designing

Introduction

• Direct-reduced iron (DRI) also called sponge iron is produced from direct reduction of iron ore (in the form of lumps, pellets or fines) by a reducing gas produced from natural gas.

• The reducing gas is a mixture majority of hydrogen (H2) and carbon monoxide (CO) which acts as reducing agent.

• Fe2O3 + CO —> 2Fe + CO2• Fe2O3 + H2 —> 2FeO + H2O

Process Description

• The direct reduction of the oxide is carried out on a continuous basis. The iron oxide, fed to the top of the shaft furnace, flows downward under gravity and is discharged from the bottom in the form of direct reduced iron.

• Reduced Gases having major components of Hydrogen and Carbon monoxide is fed into the Shaft Furnace.

• Reaction between Iron Oxide and Reduced Gases occurs at 950oC and Reduced iron in form of Pellets is achieved at the bottom of the Furnace.

• At the top of the Furnace, Spent gases are exists.

Cont….

• Spent gases are recompressed and mixed with Natural gas and transported to the Reformer.

• Hence a Continuous process occurs.

In 2003 the MIDREX® Direct Reduction Process was the leading direct reduction technology with more than 60% of world DRI production for the 17th consecutive year.

Direct Reduction Technology

2003 World DRI Production by Process

2003 World Direct

Reduction Capacity

Utilization by

Process

Direct Reduction Process DRI Flowsheet

MIDREX® Technology Benefits• Highly Competitive Operating Costs• Process Reliability / Proven Processes• Low Capital Costs / Quick Payback• Predictable Operating Costs• Hot Steelmaking Options• Environmentally Friendly• Feed Material Flexibility• Waste Process Options

MIDREX® Direct Reduction Plants

1. Acindar2. American Iron Reduction3. Amsteel Mills4. ANSDK5. Caribbean Ispat Ltd. 6. COMSIGUA

7. Delta Steel 8. Essar Steel 9. Georgetown Steel10. Hadeed11. Hanbo Steel12. IMEXSA13. Ispat HSW14. Ispat Industries15. Khouzestan Steel 16. LISCO

17. OPCO18. NISCO19. OEMK20. QASCO21. Saldanha Steel22. Ispat Sidbec23. SIDERCA24. SIDOR25. CORUS Mobile26. VENPRECAR 27. TSML(Pak)

MIDREX® Direct Reduction Plantsworldwide

Material Balance Sheet

• Reformer• Methane+ Process Gases= Reformed Gases• 33169.73 + 311383.613 =344553.343 • Fuel gas + Air=Flue Gases• 120021.7+166286.2=286307.4• 286307.9=286307.4• Furnace• Reformed Gases + Iron Oxide= DRI + Top gases• 344553.343 + 331006.3 = 241718.2 + 433804.6 • 675559.64 = 675522.8

Overall Material Balance Sheet

Streams in (Kg/hr)• Methane= 33169.73• Process Gases= 311383.613• Fuel gas=120021.7• Air Supplied=166286.2• Iron Oxide= 331006.3• Total=961867.54

Streams out(Kg/hr)• Flue Gases=286307.4• DRI= 241718.2• Top gases= 433804.6

• Total=961830.2

Overall Energy Balance Sheet

Furnace• Streams in(MW)• Reduced Gases=-0.60779 • Iron Oxide =-0.47317805

Reformer• Feed Gases=801.53

Heat Exchanger• Feed Gases= 278993 • Air Supplied= 62027.39

• Streams out(MW)• Top Gases =-1.08017565 • DRI =0.005210552

• Reduced Gases=596.85• Fuel Gases=204.6733

• Flue Gases= 341018

Designing of Tubular Reformer

Reformer and its types

• Definition of Reforming• Reforming is the process that converts straight-chained

hydrocarbons into branch-chained, cyclic and aromatic hydrocarbons.

• Through reforming Synthesis gases(CO+H2) are produced.

• Types of Reforming• Reformer is classified into 3 types, which are as follows

1- Thermal Reforming2- Steam Reforming

Thermal Reforming

• Thermal Reforming is the oldest and the first form of reforming that was developed in the late 1920s.  As its name indicates, this process is carried out under a lot of temperature and pressure.

• Mostly used in Petroleum industries.• Most of the problems occur in this type of reforming Such

as the impurity of Product and the By products.

Selection of Steam Reforming

• Using natural gas as a feedstock the basic reforming reaction is:

CH4 + H2O      =>       CO + 3H2

• There can be many catalysts for this reaction, but for commercial ease, nickel catalysts are commonly employed.  This reaction is endothermic.  During the reforming process, there are many reactions that can occur to result in carbon formation, which is not preferred because the solid carbon can deposit on the catalyst and deactivate it.  This problem is solved with the use of excess steam to shift the carbon formation reaction to the right:

Cont…..

• We have used Steam Reformer because:• The burning value of the fuel is increased, because steam

reforming is an endothermic process, resulting in a more efficient fuel.

• Steam reforming produces less exhaust emissions than burning the feedstock fuel.

Types of Steam Reformer according to design

• Radiant wall or side fired• Top fired• Bottom fired/Terrace wall fired

• High Flux Steam Reforming by Thomas Rostrup-Nielsen Haldor Topsoe A/S, Lyngby, Denmark

Radiant wall or side fired Reformer

• These Reformer contains tubes mounted in a single row along the centerline of the furnace. In larger installations, two such furnaces are erected side by side with common inlet and outlet systems and with common fuel supply, flue gas duct, and waste heat section. Burners are mounted in several levels in the furnace walls, and the flames are directed backwards towards the walls. The tubes are heated by radiation from the furnace walls and the flue gas and to a minor extent by convection. The flue gas leaves the furnace at the top so that the flow of process gas and flue gas is counter-current.

• STEAM-HYDROCARBON REFORMER FURNACE DESIGN by Foster Wheeler

Top fired Reformer

• The top fired reformer features of a furnace box with several rows of tubes. Burners are mounted in the furnace ceiling between the tube rows and between the tubes and the furnace wall. From the burners, long flames are directed downwards, and the tubes are heated by radiation from the flames and the hot flue gas and by convection. The flue gas leaves the furnace box at the bottom, so that the flow of process gas and flue gas is co-current.

Bottom fired/Terrace wall fired

• The bottom fired type has easy access to the burners and gives an almost constant heat flux profile along the length of the tube. Since the tubes are hot in the bottom a substantial margin is required on the tube design temperature limiting the outlet temperature.

• The terrace wall fired type reformer is a modification of the bottom fired type, having slightly lower tube wall temperatures.

Reformer

Gas-tight refractory-lined furnace with catalyst tubes through which gas flows upward

NG plus recycled top gas (feed gas) is catalytically reformed

Reducing gas is approximately 90% (H2 + CO), used without quench

Reducing GasReducing Gas

FlueFlue GasGas

FeedFeed GasGas

Fuel Gas and Fuel Gas and Combustion AirCombustion Air

Reformer Reformer DetailDetail

(Side View)(Side View)

Flue Flue GasGas

Feed Feed GasGas

Fuel Gas and Fuel Gas and Combustion AirCombustion Air

Reducing Reducing GasGas

Reformer Tubes Reformer Tubes with Catalystwith Catalyst

Design ApproachKine

tics

Unkno

wn

Kinetics

known

Design Specifications

MIDREX® Reformer Reactions

ReactionReaction HeatHeat DescriptionDescriptionCHCH44 + CO + CO2 2 2CO + 2H2CO + 2H2 2 EndothermicEndothermic COCO22 reforming reforming

CHCH44 + H + H2 2 O CO + 3HO CO + 3H2 2 EndothermicEndothermic HH22O reformingO reforming

Designing Calculations

• Heat Load(Heat Duty)=286941333 KJ/hr

• Average heat flux= 113556.49 KJ/hr.m2 • Heated Length=ZH=L=11.27m• Diameter of Tube=D=0.13m• Area for Single tube=A1=ᴫDL =4.600414 m2 • Area required for Heat Load= Heat Load(Q)

Heat Flux (from Process Heat Transfer by DQ.KernChap#19& Chemical Reactor Design for Process Plants Case

Study 111 by Howard F.Rase)

(Rule of Thumb, Chapter#19 Process Heat Transfer by DQ.Kern pg#603)

Cont……

• Area required for Heat Load=At= 286941333 KJ/hr

113556.49 KJ/hr.m2 = 2526.8598 m2 • No of Tubes= At

A1

= 2526.8598 m2 = 549.26791

4.600414 m2 By Giving 30% Corrosion allowanceExtra Tubes= 0.3(549.26791)= 164.7804

Cont….

• Total no of tubes= 549.26791+ 164.7804

= 714.0483 ≈ 714 • Volume of 1 tube=V= ᴫD2L = 0.1495135 m3 4• Volume of Total tubes= 714* 0.1495135 m3

= 106.75261 m3 • Volume of Total tubes=Volume of CatalystSo,• Volume of Catalyst= 106.75261 m3

Cont….

• Bundle diameterDb= do(Nt/k1)1/n1

Here,n1= 2.142 (for one pass)k1= 0.319do= 0.1524mNt= 714

Db= 5.583425 m

Cont….• Pitch(Triangular)• Pitch = 1.25do

= 0.1905 m• Clearance = Pitch – outer dia = 0.1925 – 0.1524

= 0.03810 m • Inner dia of Shell=D= 5.583425 + 0.03810= 5.6215m• Area of Shell= πD2/4= 24.807232 m2

• Length of Shell = 12.1921m• Volume of Shell = πD2L/4 = 302.45m3

• From RC vol 6,Chapter#12,pg# 665• Process Heat Transfer by DQ.Kern

Selection of Catalyst• Steam reforming of natural gas has been performed at high

temperatures over Ni - based catalysts.• Ni Oxide has been the favored because of its sufficient

activity and low cost.• These catalysts are shaped into an optimal form, often in

the shape to have a better heat and mass transfer and to minimize the pressure drop under the industrial operating conditions.

• The Ni - Oxide suffer from catalyst deactivation by coke formation at high temperatures.

• Catalyst is in form of Rasching Rings pellets.

Calculations….

• Pellet Diameter =DP=0.017 m• Wall Thickness=0.005 m • Length=0.017 m• Bulk density=ρb=913.05241 Kg/m3 • Porosity=є=0.52• Mass of Catalyst=Bulk Density*Volume = 913.05241 Kg/m3 * 106.75261 m3 = 97470.73 Kg

Cont….

• Mass Flow in Each Tube= = (114851.1 *4)/(3.14*0.132*714)

= 12124.97 Kg

Pressure Drop Calculations• By Ergun Equation ∆P = 150 µG(1-є)2 + 1.75 G2(1-є) L kgρD2є3 kgρDє3

Here,ΔP = pressure drop, lb./in2, or psi L = Heated length, ft= 37G =Mass velocity, lb./hr.-ft2 = 2478.242 ρ = fluid density, lb/ft3 = 0.044 μ = fluid viscosity, lb/hr.ft = 3.13*10-5

D = effective particle diameter,ft = 0.055774 ε = interparticle void fraction, dimensionless =0.52g = gravitational constant, 4.17 x 108 lb.-ft./lb.-hr2 k = conversion factor, 144 in2/ft2

Cont….

• By putting all values in previous equation ∆P = 9.4 Psi

Specification Sheet Reformer Type Steam Reformer

Equipment Id RF-A40

Operating Condition

Operating Temperature 950oC

Operating Pressure 2.469 bar

Heat Flux 113556.49KJ/hr.m2

Heat Duty 2.86*108KJ/hr

Length(tube) 11.27m

Inner Dia (Tube) 0.13m

Outer dia(tube) 0.1524m

No of Tubes 714

Specification Sheet Volume of Tubes 106.7526m3

Mass of Catalyst 97470.73Kg

Mass flow in each tube(G) 12124.97Kg/hr.m2

Db(bundle diameter) 5.583425

Pitch 0.1905 m

Clearance 0.03810 m

Inner dia of Shell(D) 5.6215m

Area of Shell 24.807232 m2

Length of Shell(L) 12.1921m

Volume of Shell 302.45m3

Pressure Drop(∆P) 9.4 Psi

Material of Construction Carbon Steel

Designing of Blowerby

Yasar Zia

Definition Of Blower

These are machines that move and compress gases .

High speed rotating devices that develop a maximum

pressure of 2 atm.

Types Of Blowers

Positive-displacement blower

• These machines operate as gear pump because of the

special design of the “teeth”.

• A single stage blower can discharge gas at 0.4 to 1 atm

gauge.

• Two stage blower can discharge gas at 2 atm.

Centrifugal Blower

In appearance it resembles a centrifugal pump.

They are high speed operating machines, 3600 rpm or

more.

High speed and large impeller diameters are required

because very high heads.

Block Diagram

166286.2 kg/hr 166286.2 kg/hr

P= 105526.03 Pa P= 119026.36 Pa

Main Air Blower

Calculations--- Work done by Blower

Wb= ∆H/ η

Power of the BlowerPB = m0Wp

hs = Ps/ℓg ; hD = PD/ℓg

Vs = Vs^2/2ℓg ; VD = VD^2/2ℓg

Reference: From Mc-cabe Smith unit operation 7th edition

Continued…………. Total Suction head = Ps/ℓg + Vs^2/2gℓ

Total Discharge head = PD/ℓg + VD^2/2gℓTo Find,

∆H = hD – hs

∆P = PD – Ps

Reference: From Mccabe Smith unit operation 7th edition

Continued………

PV = znRT

V = znRT/P

n= 16628.62/28.8

n= 576.98 kgmol

R= 8.314 kJ/kgmol.k

T= 299 K

Ps= 105526.03 Pa

Z= 0.8

Continued……….

Continued………. V= Velocity*Area10.873= Velocity*5.814Velocity= 1.870 m/hr

To Find Suction Head, Ps/ℓg + Vs^2/2gℓ

105526.03/1.225*9.5+(1.870)^2/2*1.225*9.8= 8790.17+0.145

= hs=28790.31 Pa

Continued……….

Continued…….

Work done by Blower,Wb= ∆H/ η

= 1575.01/0.6 Wb = 2625.01 Joule

Reference: Efficiency taken as 60 % from Unit operation Mccabe Smith 7th edition.

Continued……….Power Of Blower,

PB = m0Wp = 16628.62*2625.01 PB = 58512.458 1Hp = 746 Watt PB = 58512.458/746 = 5.8*103HP

Specification sheet BlowerEquipment Code CP-B01

Equipment Name Main Air Blower

Operating Conditions ………………………

Inlet temperature 26 0C

Outlet temperature 665 0C

Inlet Pressure 105526.03 Pa

Outlet Pressure 119026.36 Pa

Flow rate 166286.2 kg/hr

Work done by Blower 2625.01 J

Power of Blower 5.8*10^3 HP

Total suction pressure hst=28790.31 Pa

Total Discharge Pressure Hst=30365.32 Pa

Designing Of Heat Recovery Unit

BYMuhammad Yasar Zia

09-CH-98

Heat recovery unit

• A heat recovery unit (HRU) is an energy recovery heat

exchanger that recovers heat from hot streams with

potential high energy content, such as hot flue gases from

a diesel generator or steam from cooling towers or even

waste water from different cooling processes such as in

steel cooling.

Continue…….

• Waste heat found in the exhaust gas of various processes

or even from the exhaust stream of a conditioning unit can be used to preheat the incoming gas. This is one of the

basic methods for recovery of waste heat. Many steel

making plants use this process as an economic method to

increase the production of the plant with lower fuel

demand.

Different types of heat recovery units

• Recuperators: This name is given to different types of

heat exchanger that the exhaust gases are passed through, consisting of metal tubes that carry the inlet gas and thus preheating the gas before entering the process

• Heat pipe exchanger: Heat pipes are one of the best

thermal conductors. They have the ability to transfer heat hundred times more than copper. The heat pipe is mainly used in space, process or air heating.

Continue…..

• Economizer

In case of process boilers, waste heat in the

exhaust gas is passed along a recuperator that carries the

inlet fluid for the boiler and thus decreases thermal energy

intake of the inlet fluid.

Three Streams In Heat Recovery Unit

Cold Stream

Feed Gas 580 0c

131 0CCold Stream 665 0C

Air 26 0C 

Flue Gases Hot Stream 1125 0c368 0C

Flue Gas and Feed Gas System

Q=m1Cp1∆T1= m2Cp2∆T2

Q= m1Cp1(1125-T) = m2Cp2(T2-T1)

286307.4*1.557*(1125-T) = 344553.3*1.7310*580-131

445780.621 * (1125-T) = 267793371.3

1125-T = 600.721

T = 524.27 0C

To Find Area Of the tubes

We Know that Q= UA ∆T

To Find ∆Tm, = (Ѳ2- Ѳ1)/ln(Ѳ2/Ѳ1)

= 545-393/ln(545/393) ∆Tm = 465.65 0C

Continue…..

Q= UA ∆Tm

A= Q/U∆Tm

A = 267793371.3/4000*465.65

A = 143.77 m2

Reference: U = 4000 Watt/m2 .K from Aspen plus

Continue…… To find Number of Tubes,

Nt = ?We know that Area = 2∏rl

Area = 795.31 m2

r= 0.0508 m l= 4 m

l= A/2∏rl= 395.31/2*3.14*0.0508

l= 2492.94 m

Continue……Now to find Number of Tubes,

Nt = 2492.94/4

Nt = 623.23 tubes

Dia of each tube,

Outer dia of tube d0 = 2”

Inner dia of Tube di = 1.6Reference;.

Unit operation by Mccab smith 7th edition

Flue Gas and Air SystemSimilarly,

m1Cp1∆T1= m2Cp2∆T2

m1Cp1(524-T) = m2Cp2(500-26)

286307.4*1.557*(524-T) = 166286.2*2.01*(500-26)

445780.62*(524-T) = 158427514.2

524 – T = 355.393 0C

T = 168.60 0C

Continue……… To find Area,

Q= UA ∆Tm

A= Q/U∆Tm

∆Tm = Ѳ1- Ѳ2/ln(Ѳ1/Ѳ2)

= 142-24/ln(142/24)

∆Tm = 66.4 0C

Area = 158427514.2/3000*66.4

A = 795.31 m2

Continue…..To Find Number of tubes,

Area = 2πrl Area = 795.31 m2

r=0.0508 m l= 4 m

l= A/2πrl= 795.31/2*3.14*0.0508

l= 450.65 mNt = 113 tubes

Dia of each tube,

Outer dia of tube d0 = 2”Inner dia of Tube di = 1.6”

Specification SheetEquipment Code HE-B05, HE-A65Equipment Name Heat Recovery Unit

Operating Conditions

Inlet temperature 1125 0C of flue gases

Outlet temperature 368 0C of flue gases

Inlet pressure 100724.85 Pa of flue gases

Outlet pressure 100324.7 Pa of flue gases

Inlet temperature 580 0C of feed gases

outlet temperature 131 0C of feed gases

Inlet pressure 148336.59 Pa of feed gases

Outlet pressure 153137.7 Pa of feed gases

Inlet temperature 26 0C of air

Outlet temperature 500 0C of air

Inlet pressure 100524.8 pa

Outlet pressure 119029.36 Pa

Heat Transfer area of flue gas and air system

795.31 m2

Heat transfer area of flue gas and feed gas 143.77 m2

Heat transfer coefficient of flue gas and feed gas

2667793371.3 watt/m2.k

Heat transfer coefficient of flue gas and air system

158482751.42 watt/m2.k

Material of Construction Carbon steel

Corrosion Allowance 0.1

Thickness of Material 0.2”

Outer dia 2”

Inner dia 1.6”