Optimization of Steel and Methanol Production in an Integrated

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]

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.

Introduction ¹

Steel plants have a significant contribute to the global CO ₂ emission:

 4-6% of man-made CO ₂ ,

 largest point source of CO ₂ in the world,

 Blast Furnace Ironmaking is responsible for 80-

90 % of this emission,

Introduction ²

Potential Direction:

 New Technologies

 New Reductant and fuels; focus on biomass

 Process Integration; by-products and CO ₂ 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:

CO

issue is a business risk for the Steel Industry in Europe

Cost  Acceptance by society

Introduction ³

 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.

CP: coke-making plant, SP: sintermaking plant, ST: hot stoves, CS: CO2 stripping unit, BF: blast furnace, BOF: basic oxygen furnace and PP: power

Models of the Unit Process and Emissions

Models of the Unit Process and Emissions

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

Models of the Unit Process and Emissions ³

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 n 319.7 m

; 0.695

3 coke COG

coal

coke

m V m

m      

t 12 MJ

. 85

; 0714 . 0

; 046 . 0 ,

042 .

1

sint

m m m m m Q m

m            

sint coke, coke

int

coke,

m m

m     

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 CO

-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

Models of the Unit Process and Emissions

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 n 5 m

. 41 t ;

n 6 m

. 45

; 895

. 0

3 hm BOF

3 hm BOF

, O scrap

hm

ls

m m V

m V m

m           

CHP plant: overall energy balance between residual of gases from BF and part of the BOF are used to produce electricity and district heat.

 

.

; 1

PP PP

P   E Q     E

E _pp =(1-β-М)V _BF H _BF +k V _BOF H _BOF

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 n 319.7 m

; 0.695

3 coke COG

coal

coke

m V m

m      

t 12 MJ

. 85

; 0714 . 0

; 046 . 0 ,

042 .

1

sint

m m m m m Q m

m            

sint coke, coke

int

coke,

m m

m     

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 CO

-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

Models of the Unit Process and Emissions

Gas Reforming unit:

 Endothermic Reaction favored by high temperature and low pressure.

 The reaction produces 1:3 CO/H ₂ instead of the 1:2 needed for MeOH synthesis, so CO ₂ is imported to the unit and in water-gas shift reaction, CO ₂ is shifted back to CO by consuming some H ₂ . The CO ₂ to CH ₄ molar feeds ratio needs to be 1:3 to get 1:2 CO to H ₂ for MeOH synthesis, though any incomplete conversion of CO ₂ would call for a slightly higher feeds ratio.

 Unconverted CO ₂ 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



 

  

 

SMR Reactor Condition: CH ₄ +H ₂ O=CO+3H ₂

• 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+2H ₂ =CH ₃ OH

CO ₂ +3CH 4 +2H 2 O=4CH ₃ OH

Models of the Unit Process and Emissions ⁶

COP BF

Methanol Reactor

BOF

CHP

MeOH Plant Gas Reformer

steam

Coal Coke Oil Air/O2 Ore

Limestone Pellet scrap

Heat Power Steel Slag Co

Schematic description of PI model

k

β

C

80 €/t

C

100 €/t

C

145 €/t

C

300 €/t

C

150 €/t

C

30 €/t

C

50 €/km

n

C

100 €/t

C

50 €/MWh

Objective Function

2, 2

. .

,

44 0.95

CO strip

12

m  V Y

2 , lime C,lime ,

, , , , ,

.

44

12 (

)

CO Coal C coal Oil C Oil

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

m m X m X m X

m X m X m X m X

  

   

2 2 2 2

lim lim

3 3

2,

(

coke coke oil oil e e

o o co co

scrap scrap

co strip

m C

m C m C

F

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 C

m C

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

     

     

     



) /

steel

C m C P C Q C m

t h  Euro t  t h  Euro t  MW Euro MWh   MW Euro MWh  t h

Conclusion ¹

 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 CO ₂ than steelmaking without

integration.

 In order to considering the emissions from fossil fuels in the systems, using biomass decreases around 0.2 t _CO2 per t _steel emission in steel plant without integration .

The first and second stage integration will decrease 0.4-0.45 t _CO2 per t _steel 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.

Conclusion

Conclusion and Future works ¹

The study has demonstrated that the optimal recycling degree of top gas varies with the cost structure of emissions, CO

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 CO ₂ emission is found in Max CO ₂ cost

 For state which the cost of emission and stripping are equal (C co

=C

=20

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

recycling that shows the balance between decreasing CO

emission and

methanol production in minimization of steel production cost and in higher

production rate the condition change to lower β and increasing in CO

emission

and methanol production.

 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 CO

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 CO

stripping and emission rise by 20 €/t respectively.

Conclusion and Future works

 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.

Future Works

 Thank you for your attention !

 Questions,

Comments,

Remarks,

Advice?