6 waters impact on dri

8/13/2019 6 Waters Impact on DRI

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Process Overview DRI Water Systems

Specific Water Issues Typical Challenges Recommendations

Water Quality Microbiological Solids Balance

Take Away Items

2ChemTreats Steel Industry Water Conference 912 to 9142012 , Clearwater Beach FL* Confidential * Do Not Duplicate without Permission


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Direct Reduced Iron Midrex & HYL: > 75% of DRI produced

Reaction occurs above iron melting point Oxygen removal process

2

Typically cracked natural gas (CH4)

Lump/Pellet/Hot briquetted

(HBI)

Fixed chemistry Reduced tramp elements Combined carbon Increase EAF efficiency

Lower CO2 vs. Coal based processes Operational Flexibility



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Natural Gas Costs Driving factor for DRI locations

Historically located in Middle East, Asia, and Southern Caribbean

Decades low prices Shale supplies North American competitive advantage

A ma or g o a stee pro ucers are eva uat ng DRI production options



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Tenova/Danieli Energiron HYL DRI PlantTenova/Danieli Energiron HYL DRI Plant

Water Quality Tenova Company Mar eting wit Danie i 32 Modules in operation Operating Pressure: 45 Bars

ncrease 2 concen ra on Smaller foot print

Less fines

Steam reforming (HYL3)

Water/CO 2 generation Selective elimination

CO2 absorption & capture Mechanical seals

Lock hoppers & Double Valves



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DRI PlantCooling Water Systems

MachineryClosed Cooling

1.) Reactor Jacket Cooling2.) Bottom Flow Feeders3.) Gas Compressor Cooling

Direct ContactCooling Water

Non ContactCooling Water

. as er oo ers

1.) Heat Exchangers2.) Air Compressors3.) Lube Oil Cooler4.) Alternative to

1. Process Gas Scrubber2.) Cooling Gas Scrubber3.) Dust Collection Scrubbers4.) Quench Orifice/Venturis

Closed MachineCooling5.) Quench Tower6.) Cooling Tower / HX7.) Ammonia Scrubber8.) Clarifier



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Cooling TowerOr

Heat Exchan er

Top Gas ScrubberCooling Gas ScrubberSeal Gas CoolerDust Collection Scrubbers

Ammonia Scrubber Blow down

ClassifierClarifierot e

SludgeDewatering

Dewatered Sludge



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Top Reducing Gas Reuse (Top Gas) Cools process gas for reuse Cleaned by wet scrubbers

Gas exits

reactor

at

~ 400

oC

(Counter

flow)

1/3 of gas used for reformer burner fuel 2 3 of as re in ected throu h reformer

Reducing gas or seal gas system makeup

Cooling Gas oo s o oun er ow Reduces re oxidation potential Helps to define Fe3C (Carbon content)

Cooled, compressed, recycled Made up with natural gas

Auxiliary (Product/Oxide handling)



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FROM DUST

Removes iron particulates, lime and

other solids from the gas streams

PICK-UP POINT

SEPARATOR

TO SCRUBBERFAN SUCTION

ean ry gas s nee or op m za on Spray and Swirl water Provides gas cooling

SPRAYNOZZLE

VENTURI

CHEVRON MISTELIMINATOR

MESH PAD

INLETBOX

WATER INLET

Water returned to process clarifier Minimize water carryover

INSERT

THROAT AIR

DISTRIBUTIONPLATE

LEVELGAUGE

WATER INLET

ELBOW

SUMP PUMP

TO SCRUBBERCLARIFIER

WATER INLET

ACTUATOR

CENTRIFUGAL

LCV

PUMP



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ar er Removal targets

Iron articulate

Soluble Iron

Mineral precipitants

Typical solids loading Influent 500 2500 ppm Effluent 20 40 ppm

Treatment chemistry

pH Control


Proper c ar er operat on w t so s mass a ance is critical for plant operations


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Gas Compressors 2stage Process & Cooling Gas Compressors Seal Gas Compressors

Direct Water Injection Reduces heat of compression Rinses lobe surfaces Minimizes pressure loss Reduce gas volume Corrosion

Rack DrainOr

CompressorDrain

Compressor seal failures Erosion/Corrosion lobes

Reuse

Damage to heat recovery bundles Reforming catalyst poisoning



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High temperatures Gas velocity (Erosion potential)

RO or Softener

CO2 / Sulfur

pH

depression Wet/Dry potential StorageSodiumHydroxide

High quality spray water Drain water monitoring

CorrosionInhibitor

Iron Corrosion rate

Compressors

Compressors

Corrosion Corrosion

Online digital probes Flow

ac

DrainOr

Reuse



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Foaming Tendancy Catalyst Poisons

Scrubber Operations Limited Standardization

Limited Disspersion

Reducing Gas Suspended Solids

Benchmarking

ompos on an Consistancy

Oxide Coatings

Microbiological

Chlorides

Intermitant Ops Remet additon

CO2 & Sulfur



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Impact on DRI Process Elevated Microbio Activit

Process Water Contaminants Soluble Iron Clarifier Post Precipitation

Increased TSS

loading

Fouling

potential Corrosion potential

CO2 stripping pH increase Insoluble Iron fouling

equipment / piping wear

Increased chemical demand

Oxide Coating

Lump Iron vs. Pellets Increased energy usage

Cooling tower fouling Reduced

u ur 2 con am na on Ammonia generation

Increased Cleaning Frequency Reduced Gas Cleaning ata yst o son ng

Moisture Carryover

to

off

gas



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Clarifier pH adjustment (8.0 8.3)

Soluble Iron

Comineral precipitants Caustic or lime

Strip CO2 pH increase Oxidize Soluble Iron

Air Lance Peroxide

Chemical Program Chemistry/Prep/Location

Avoid dispersants Evaluate sludge recirculation Evaluate sludge bed depth



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Iron Management

Know the system (TSS/Iron) Dont recycle solids from sludge

Solids in

must

balance

with

out Chemical

clarifier and sludge dewatering

pH to remove soluble iron CO stri in

Mechanical Limit lump iron use Limit & Control Remet use Consider alternatives for

auxiliary scrubbers



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Process Challenges Process Challenges Plugged Spray NozzlesPlugged Spray Nozzlese uce cru er er ormance

Increased Packing Fouling

ncrease op as ue emp Results in increased moisture Higher flue gas volume

Less Water

thus

increased

fouling

Microbial potential

Increased burner natural gas rate Increased ejector stack fan

electricity



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Process Challenges Process Challenges Fouled EquipmentFouled Equipment

Mineral Scale Oxide Coatings

Increased pH & Alkalinity CO2 Stripping

Increased pH Caustic Addition Iron removal

Increased pH

Mechanical Seal Lowers Tower Cycles Water Balance

Consider pH adjustment

Acid or CO2 re injection Organic phosphate scale inhibitor



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Microbial Monitoring Sessile & Planktonic Di slides / ATP / Cultures Multiple Monitor Points

Bulk Water Treatment on ox zers on y rex Low foaming Plant Trip

Correct biocide selection Localized Treatment

TGS & CGS

Greatly Increase Iron Fouling Potential



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Cooling Tower or Heat Exchangers Post precipitation of iron Sus ended solids Mineral scale Microbiological

Increased gas temperature Reduced process efficiency

High tower maintenance, cleaning costs, & fill replacement

Cooling tower fans Gas compressors



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Both processes generate NH4 Local limits may be exceeded

20 40 ppm Blow down treatment

95% removal at pH > 11.5

pH increases scaling potential Highly susceptible to fouling Decreased removal efficiency Increased maintenance costs Redundancy or increased down time



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DRI Process Water DRI Process Water Key Performance Key Performance

Average Good

Coolin Tower Cleanin 1 ear 2 ears

HX Cleaning


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DRI DRI Leading IndicatorsLeading Indicators

Average Good

Sus ended Solids TSS < 40 m < 20 m

Chlorides (as Cl) < 100 ppm < 75 ppm5 4

Sessile Microbio < 10 6 cfu/cm 2 < 10 5 cfu/cm 2

RSI / LSI 5.0 6.5 / 0 1.5



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Steel Corrosion: < 5 mpy

System Soluble Iron: < 1.0 ppm

Correct treatment chemicals (Midrex)

No phosphate/Bleach/Bromine

Process Cooling WaterProcess Cooling Water

TSS < 25 ppm Ideal < 20 ppm

System Chlorides: < 100 ppm as Cl

Monitor both lanktonic and sessile bacteria

Do not use disspersants

Equipment inspections are critical

Dont underestimate im act of CO and

pH control is critical for Iron removal

pH is critical for system scale and corrosion

sulfur on process performance

Trend individual flow rates vs time and

design specifications as important as correct product

Organic phosphate is required for high LSI system with oxide coating application

RSI/LSI/scale monitoring should be part of service plan

Consider impact of makeup water

Consider multiple feed points for both organic phosphate and microbiocide

Microbiocides must be low foaming

Complete frequent water and TSS balances

Monitor KPIs to provide ecomomic ustification for s stem treatment

improvements

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6 waters impact on dri

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