Conference Norilsk September 2012

1Milano, 18 Aprile 2012

Environmental protection and industrial activity in the North - Norilsk. 11-14 September, 2012 1

SO2 removal from metallurgicalprocess off gas

by Michele Genova

Environmental protection and industrial activity in the North Norilsk. 11-14 September, 2012


Environmental protection and industrial activity in the North - Norilsk. 11-14 September, 2012

Outline Introduction Gas cleaning unit Sulphur Dioxide Concentration Unit Sulphur Recovery Unit Sulphur Storage and Handling

Facilities Conclusion



Our group Six leading companies operating worldwide

Permanent Employees: 57,000



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38%

8%

5%5%

3%

Sales by Company

Techint Group Revenues: Over USD 24 billion as of Dec 31, 2011

Our group



Available services: Feasibility Studies Basic and FEED Detail Engineering Project Management Procurement Services Construction Construction Management Project Financing Commissioning Operation and Maintenance

What we do



INTRODUCTION

Techint is involved to design & implement thetechnical solutions for elementary sulphurrecovery from flue gases coming frommetallurgical plant.

The adopted technical solutions consent toreduce the sulfur emissions of 95% wt producingElementary Sulfur.



1. Purification and cooling of the flue gas stream2. Physical absorption of sulfur dioxide3. Stripping of sulfur dioxide4. Cooling and compression of the sulfur dioxide

product5. Reduction of sulfur dioxide to hydrogen sulfide6. Sulfur recovery unit7. Liquid and solid sulfur storage facilities

The selected processes includes the following units:

INTRODUCTION



The aim of the cleaning unit is to purify the fluemetallurgical gases before sending them to the SO2concentration units.

In the flue gas cleaning unit all the impurities suchas heavy metals, sulfuric acid mist and halogensare removed to avoid the following implications onthe downstream equipment:

Corrosion of the EquipmentHigh consumption of solventContamination of the product.

FLUE GAS CLEANING



CLEAN

GAS TO

DRYING

TOWER

HOT,

DIRTY

GAS

INLET

MAKE-UP

WATER

WET ELECTROSTATICWET ELECTROSTATICWET ELECTROSTATICWET ELECTROSTATIC

MIST PRECIPITATORSMIST PRECIPITATORSMIST PRECIPITATORSMIST PRECIPITATORSBLOWDOWN

PRIMARY REVERSEPRIMARY REVERSEPRIMARY REVERSEPRIMARY REVERSE

JET SCRUBBERJET SCRUBBERJET SCRUBBERJET SCRUBBER

GAS COOLING TOWERGAS COOLING TOWERGAS COOLING TOWERGAS COOLING TOWERTWO STAGE FINALTWO STAGE FINALTWO STAGE FINALTWO STAGE FINAL

REVERSEREVERSEREVERSEREVERSE

JET SCRUBBERJET SCRUBBERJET SCRUBBERJET SCRUBBER

WEAK ACID

COOLER

FLUE GAS CLEANING

10

Milano, 18 Aprile 2012


Reverse Jet Scrubber

Hot gas quenching Particulate removal Acid gas absorption Uses large orifice

liquid injectorsNon-atomizingNon-plugging

FLUE GAS CLEANING

Source: MECS

11



Uses pressure drop effectively Doubles removal efficiencies Reduces costs by using

multiple Reverse Jets in single inlet barrel

FLUE GAS CLEANINGMultiple Jet ScrubberSome advantages of the technology are:

Source: MECS

12



FLUE GAS CLEANINGWet Electrostatic Precipitators

Source: GEA Bischoff

13



FLUE GAS CLEANING

Source: GEA Bischoff

14



SO2 CONCENTRATION

Source: MECS

Physical Absorption System Selectively absorbs SO2

from the gas stream SO2 emissions - 300 ppmv

or less Some contaminants like

CO2 are also absorbed to a lesser extent

SO2 is stripped from the solvent with heat

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Physical vs Chemical AbsorptionPhysical vs Chemical AbsorptionPhysical Absorption Aprotic Solvent No Chemical

Reactions Lower Solvent Loss Simple Chemistry Organic system Lower Steam Usage Higher L/G Follows Henrys Law

Chemical Absorption Protic Solvent Many Chemical

Reactions Higher Solvent Loss Complex Chemistry Aqueous system Higher Steam Usage Lower L/G No Henrys Law

SO2 CONCENTRATION

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Process Differences Chemical versus PhysicalSolventProcess Differences Chemical versus PhysicalSolventMuch more energy required for

regenerating chemical solvent.Capital cost for regenerating chemical

solvent is higher than for physical solvent.More process steps for regenerating

chemical solvent.

Absorption step is similar.

SO2 CONCENTRATION

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SO2 CONCENTRATIONSulfur Dioxide Solubility

in Physical and Chemical Absorbents

0

1

2

3

4

5

6

7

8

9

10

0% 10% 20% 30% 40% 50%

Sulfur Dioxide in Liquid Phase (mole %)

S

O

2

P

a

r

t

i

a

l

P

r

e

s

s

u

r

e

(

k

P

a

)

PhysicalChemical

Solvent LossPhysical vs Chemical Absorpiton

1

10

100

1000

0% 2% 4% 6% 8%

Gas Strength (% SO2)S

o

l

v

e

n

t

L

o

s

s

(

l

b

/

M

M

S

C

F

)

PhysicalChemical

18



SO2 ConcentrationInlet Gas Conditions of SO2 concentration unitsInlet Gas Conditions of SO2 concentration units Gas Stream contaminants (Particulate, Acid Mist) have

a significant impact on solvent loss: 10 mg/Nm3 Particulate Desired 20 mg/Nm3 Acid Mist Desired

Product SO2 StreamProduct SO2 Stream

Concentrated SO2 up to 98% wt, with some impurities, particularly CO2, depending on inlet gas conditions and water saturated

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SO2 ConcentrationReference ProjectReference Project

Design basis 300,000 Nm3/h 0.2% SO2

Performance 100 ppm SO2 98% SO2 after

CO2 stripping

Source: MECS

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Sulphur Recovery Unit

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Sulphur Recovery Unit (SRU)The sulphur recovery unit could include thefollowing section:SO2 Feeding to SRUThermal stage (Burner, furnace & Waste heat

Boiler)Catalytic stage (Claus Reactors and Condensers)Tail gas incinerator and heat recoverySulphur degassing storage and exportSulphur solidification (if any) and solid sulphur

handling systems

22



Sulphur recovery facilities are provided toproduce sulphur from concentrated streams ofsulphur dioxide.

The overall sulphur recovery is at least 95%based on the SO2 feed to the concentrator units.Losses from the concentrator units mean that thesulphur recovery facilities need to recover morethan 95% of the sulphur fed to them.

Sulphur Recovery Unit (SRU)

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The heart of this special SRU is the thermalreactor where the SO2 is reduced to H2S andsulphur by a combination of reducing gasesgenerated from the combustion of the natural gas.

The furnace gases are cooled in the WHB, whichis used to generate steam for process heating inthe Claus unit. The excess high pressure steam isexported. The gases react during cooling in theWHB tubes and the sulphur species in the outlettail gas are mainly H2S, SO2, COS, CS2 andsulphur vapour.


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The overall reactions taking place in thermalreactor during the direct reduction of SO2 can besummarized in:


@ ~ 1200 C2SO2 +

+ 4H2S

CH4 S2 + 2H2O + CO2

6SO2 + 4CH4 S2 + 4H2O + 4CO2@ ~ 1200 C

(4n+m) 2CnHm + mH2O + 2nCO2

The heat will be provided by the combustion of fuel gas:

2O2

25



The gases heated at the correct temperatureusing a steam heater enter in the Clausreactors where H2S and SO2 react to formmore sulphur, the process gases flow to thecondensers; the condensed sulphur drained tothe degassing system via a seal leg.

The tail gases from the final Claus condensercontaining Sulphur compounds and about 4%H2 and 6% CO, are incinerated at 800C toconvert all the sulphur compounds to SO2.


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The effluent from the incinerator is cooled inthe incinerator WHB before be discharged tothe existing chimney. The steam is generatedat adequate pressure in the WHB so that thiscan be used as heating steam for the Claus.

The steam pressure in the WHB will beselected in order that the tube walltemperature is higher than the sulphuric aciddew point to avoid corrosion in the chimney.


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Sulphur is rundown from the condensers to asulphur collection pit with sufficient capacityfor 24 hour hold-up of the produced sulphur.The sulphur is degassed sufficiently to reduceodour during the solidification of the sulphur.

Sulphur is circulated around the pit via sulphurpumps in order to stir the liquid and reducedHydrogen Sulfide content..


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Sulphur Recovery UnitReference ProjectReference Project

Client : WEPEC

Type : SRU + TGT

Process : LGI

Application : Refinery

Capacity : 315 t/day

Hydraulically equivalent to 1 train to be

design for MZ Copper plant

Site : China

Source: LGI

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The liquid Sulphur could be solidify or sale as wellas it is. The granulation unit consists of packagedgranulating systems, complete with one liquidsulphur conditioning system. The conditioningsystem consists of a liquid-sulphur filter, liquid-sulphur cooler, liquid-sulphur day vessel andsulphur day vessel pumps for liquid sulphur feed tothe granulators. The granulator system could besized to granulate the total capacity of sulphur.Each unit could produce up to 400 metric tonnes ofhigh quality granules per day.

Storage and Packing

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Summary

To optimize the size of SRU, you install the SO2concentration unit, using a physical solvent to reducealso the OPEX.

To minimize the solvent degradation, you clean themetallurgical process off gas to remove all the impuritiessuch as heavy metals, sulfuric acid mist and halogens.

SO2 from metallurgical process off gas could beefficiently removed using a modified Claus process witha special thermal reactor. The aim of this reactor is tooptimize the ratio of SO2 and H2S before to feed theprocess gas to Claus converters.

With the presented process you recover not less than95% of Sulphur, contributing significantly to reduce thepollution of the environmental.

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The author thanks

LE GAZ INTEGRAL

MECS

GEA BISCHOFF

for the permission to use their information.

Acknowledgements

32


Environmental protection and industrial activity in the North - Norilsk. 11-14 September, 2012 32

Michele Genova - email: [email protected] +39 335 7750 947

THANK YOUFOR

YOUR ATTENTIONSO2 removal from metallurgical process off gas

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Conference Norilsk September 2012