optimization of the mg(oh)2 production step - users.abo.fiusers.abo.fi/hghanbar/optimization of...

6-Oct-10 Åbo Akademi University - Thermal and Flow Engineering

Biskopsgatan 8, FI-20500, Åbo, Finland

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Optimization of Steel and Methanol

Production in an Integrated

H. Ghanbari, H. Helle, M. Helle,

F. Pettersson and H. Saxen

Åbo Akademi University

Heat Engineering Laboratory

Åbo / Turku, Finland

tel. +358 2 215 4440

[email protected]

Process Integration Forum for the steel industry 3rd annual meeting, 6-7 September, 2010, Luleå, Sweden



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Energy saving is an important issue in the steel industry. Improvement of the

energy efficiency, to reduce the energy consumption, will increase the

economic profitability as well as reducing the environmental impacts.

Introduction1

Steel plants have a significant contribute to the global CO2

emission:

4-6% of man-made CO2,

largest point source of CO2 in the world,

Blast Furnace Ironmaking is responsible for 80-90 % of this emission,




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Introduction2

Potential Direction:

New Technologies

New Reductant and fuels; focus on biomass

Process Integration; by-products and CO2 Capture and Storage


Most of the high value Off-gases from different units such as Coke Oven Gas

(COG), Blast Furnace (BF) and Based Oxygen Furnace (BOF) are used in

Combined Heat and Power plant which is not the most efficient way to use

them.

According to ULCOS:

CO2 issue is a business risk for the Steel Industry in Europe

Cost Acceptance by society



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Introduction3


MeOH as a FUEL

MeOH production from natural gas or biomass resources

Several commercial technology to produced MeOH from COG in china e.x. Shanxi

Tiianhao chemical company Ltd (first plant, 2005); production of 300000 tons per year.



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CP: coke-making plant, SP: sintermaking plant, ST: hot stoves, CS: CO2

stripping unit, BF: blast furnace, BOF: basic oxygen furnace and PP: power

plant.

Models of the Unit Process and Emissions1




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Input and output variables and their

constraints, as well as sinter and coke mass

production rate constraint.

Blast Furnace Model:


Treatment of the Gas Preheating

State Hot Stoves Comp.

State NO. 1 TGR+BL* TGR+BL

State NO. 2a BL TGR+BL

State NO. 2b BL(No TGR) BL(No TGR)

State NO. 3 TGR TGR+BL

State NO. 4** TGR TGR

*Bl: Oxygen Enriched air

**State No. 4: pressuerized Cold Oxygen



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Coke Plant: Linear relations between the mass flow rate of feed coal and the mass flow rate of

coke and volume flow rate of (purified) coke oven gas (COG) are assumed

t

nm319.7;0.695

3

cokeCOGcoalcoke mVmm

t

MJ12.85;0714.0;046.0 ,042.1 sintsintsintsintlime,sintsintcoke,oresint mQmmmmmm

sintcoke,cokeint coke, mmm

Sinter Plant: Only the raw materials iron ore, coke and limestone are considered, and in

addition to them, the recovered heat is also taken into account, i.e.,

which gives the (internal) flow rate of coke available for the blast furnace:

Hot Stoves: The strongly oxygen-enriched blast and the recycled and CO2-stripped top gas are

compressed and then heated in the hot stoves, which are assumed to operate as a single

continuous counter-current heat exchanger in steady state with the heat transferred from burning

oil.




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Basic Oxygen Furnace: The mass flow of liquid steel and the volume flow rates of oxygen to and

off-gases from the BOF are given as function of the mass flow of hot metal (hm);

t

nm5.41;

t

nm6.45;895.0

3

hmBOF

3

hmBOF,Oscraphmls 2mVmVmmm

CHP plant: overall energy balance between residual of gases from BF and part of the BOF are

used to produce electricity and district heat.

.

; 1PP PPP QE E

Epp=(1-β-М)VBFHBF+kVBOFHBOF




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Treatment of the Gas Preheating

Coke Plant: Linear relations between the mass flow rate of feed coal and the mass flow rate of

coke and volume flow rate of (purified) coke oven gas (COG) are assumed

t

nm319.7;0.695

3

cokeCOGcoalcoke mVmm

t

MJ12.85;0714.0;046.0 ,042.1 sintsintsintsintlime,sintsintcoke,oresint mQmmmmmm

sintcoke,cokeint coke, mmm

Sinter Plant: Only the raw materials iron ore, coke and limestone are considered, and in

addition to them, the recovered heat is also taken into account, i.e.,

which gives the (internal) flow rate of coke available for the blast furnace:

Hot Stoves: The strongly oxygen-enriched blast and the recycled and CO2-stripped top gas are

compressed and then heated in the hot stoves, which are assumed to operate as a single

continuous counter-current heat exchanger in steady state with the heat transferred from burning

oil.



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Gas Reforming unit:

Endothermic Reaction favored by high temperature and low pressure.

The reaction produces 1:3 CO/H2 instead of the 1:2 needed for MeOH

synthesis, so CO2 is imported to the unit and in water-gas shift reaction, CO2

is shifted back to CO by consuming some H2. The CO2 to CH4 molar feeds

ratio needs to be 1:3 to get 1:2 CO to H2 for MeOH synthesis, though any

incomplete conversion of CO2 would call for a slightly higher feeds ratio.

Unconverted CO2 will be purged from the synthesis loop.

Methanol unit: The converter in Lurgi LP plant is a cooled multi-tubular

reactor. The heat of reaction is directly used to generate high pressure steam

4 2 2, ,

0

MeOH MeOH purge purge j j

j CH H O CO

out MeOH MET

F H F H F H

Q F Q




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SMR Reactor Condition: CH4+H2O=CO+3H2

• Endothermic Reaction; therefore, during its operation it will be heated via

the combustion of natural gas.

• T=700-1000 ‘C

• Methane Conversion more than 95%[13]

MeOH Reactor Condition:

T=250-300 ‘C

P=5 MPa

Selectivity more than 99%

Different Catalysts

CO+2H2=CH3OH

CO2+3CH4+2H2O=4CH3OH





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COP BF

Methanol Reactor

BOF

CHP

MeOH Plant

Gas Reformersteam

Coal

Coke

Oil

Air/O2

Ore

Limestone

Pellet

scrap

Heat

Power

Steel

Slag

Co2

methanol

Schematic description of PI model

k

β




1313

Core 80 €/t

Cpellet 100 €/t

Ccoal 145 €/t

Ccoke,ext 300 €/t

Coil 150 €/t

Clime 30 €/t

CO2 50 €/km3n

Cscrap 100 €/t

Cel 50 €/MWh

Cheat 10 €/MWh

Cmethanol 250 €/t

Objective Function

Costs in the objective function

2,2

. .

,

440.95

12CO strip rg CO stripm V Y

2 , lime C,lime ,

, , , , ,

. 44(

12

)

COCoal C coal Oil C Oil

Coke ext C coke C bio ls C ls MeOH C MeOHbio

m m X m X m X

m X m X m X m X


2 2 2 2

lim lim

3 3

2,

(pel pelore ore coal coal

coke coke oil oil e e

o o co coscrap scrap

co strip

m Cm C m CF

Euro t steel t h Euro t t h Euro t t h Euro t

m C m C m C

t h Euro t t h Euro t t h Euro t

V C m Cm C

t h Euro t km n h Euro km n t h Euro t

m

) /strip MeOH MeOH el dh heat steel

steel

C m C C Q C mP

t h Euro t t h Euro t MW Euro MWh MW Euro MWh t h



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Conclusion1

Effect of increasing cost of emission is more significant in comparison of

cost of biomass.

The effect of first and second stage of integration shows that the price of

steel will decrease 10-20 euro/t and 30-45 euro/t, respectively which the

effect of integration increasing by rising the cost of emission.

The optimum operational condition of integrated system does not a

significant change according the cost of emission and biomass in case

study.

Both integrated stages produce less CO2 than steelmaking without

integration.




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In order to considering the emissions from fossil fuels in the systems,

using biomass decreases around 0.2 tCO2 per tsteel emission in steel plant

without integration .

The first and second stage integration will decrease 0.4-0.45 tCO2 per tsteel

emission in comparison with steelmaking without integration.

Production of methanol has increased by increasing of steel production

rate and is estimated to be between 17-24 tone per hour and 24-30 tone

per hour for the first and second stage integration respectively.

Conclusion2




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Conclusion and Future works1

The study has demonstrated that the optimal recycling degree of top gas varies

with the cost structure of emissions, CO2 stripping and will effect in methanol

production.

- Lower values of top gas recycling at high stripping cost

- Max recycling at high cost of emission

- Costs of liquid steel are estimated to be 10 Euro/t steel lower

than common case.

- Min CO2 emission is found in Max CO2 cost

For state which the cost of emission and stripping are equal (Cco2=Cstrip=20

€/t), in lower production rate the optimal condition is in high values of top gas

recycling that shows the balance between decreasing CO2 emission and

methanol production in minimization of steel production cost and in higher

production rate the condition change to lower β and increasing in CO2 emission

and methanol production.




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By increasing production rate, estimation of the steel cost –in case study- will

be decreasing in an integrated plant between 3.4-4.35% which the lower values

will decline by increasing the CO2 emission cost.

The costs of liquid steel are estimated to be 17-25 €/t ls lower than for the case

without top gas recycling and methanol plant.

The price of liquid steel has increased by of 10 and 13 €/t when the cost of CO2

stripping and emission rise by 20 €/t respectively.

Conclusion and Future works2

The results show that with the assumed amount of available top gases could

be produced nearly 12-18 tone per hour methanol in an integrated steelmaking

plant with top gas recycling in blast furnace.




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Future Works



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Thank you for your attention !

Questions, Comments, Remarks, Advice?


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