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Recovery and Power

• Virgin pulp– Chemical pulp

• Sulphate process• Sulphite process

– Semi chemical pulp, NSSC

– Mechanical pulp• TMP• SGW

• Recycled pulp

Manufacturing of pulp

Chemical pulp

• Wood consist of cellulose, hemicellulose and lignin• The chemical pulping process is made to remove lignin

Chemical Pulping - Sulphate process – Kraft process

• Today the most common chemical pulping process– Gives a stronger fiber

• Wood chips are treated with ”white liquor” and heated in a cookingprocess. Black liquor is developed and then evaporated.

• The high consistency black liquor is used as fuel in boiler• A smelt is created in the boiler, and will become green liquor.• Recovery of boiler chemicals, and white liquor is again created• Active cooking molecules;

– Sodium sulfide and Sodium hydroxide– (Earlier use of Sodium sulphate, is the reason for the name Sulphate process)

• Process is alkaline

Chemical recovery in kraft pulp

Chemical Pulping - Sulphite process• Earlier the most common pulping process

– Smells less, more easy to bleach, cheaper investment– But, due to high levels of effluent, not suitable for pine wood, the fiber is weaker

and has a higher manufacturing costs, the technology was reduced

• Use of different ”bases”– Ca2+ - used to be the most common, not possible to recover cooking chemicals– Na+ - cooking chemicals can be recovered, used in Aditiya Birla Domsjö– Mg2+ - cooking chemicals can be recovered, today most common, magnefite bi sulphite– NH4

+ - cooking chemicals can not be recovered

• The liquor is called red liquor or sometimes brown liquor• Process is most often acid• During the recovery of the liquor, thick liquor is oxidatively burned, resulting in

magnesium oxide dust and SO2 gas. The MgO dust is taken up in water and brought into contact with the SO2-containing waste gas from the liquor combustion to form magnesium bisulphite liquor again – much more simple process than kraft

• The liquor cause big problems with deposits, and often the walls are of lamella type, as these plain surfaces makes it more difficult for deposits.

Chemical and energy recovery in the pulp mill

Heat Management’s product portfolio

1. Optimized steam soot blowingDue to the high dust load and stickycharacteristics of recovery boiler ash, steam soot blowers are crucial to maintainhigh availability of recovery boiler

Inefficient operation is costly:• Power generation losses• Additional feed water treatment• Risk of reduced boiler availability• Compensation firing in power boiler• Wear on heat exchangers

Traditional soot blowing mechanisms

• Steam is used on both forward and return stroke• Most cleaning effect occurs at first impact (during forward stroke)• Soot blowing on return has no or little effect, but costs as much as forward stroke

Cleaning effect from first impact

How to decrease the fouling rate?

• Affect the liquor properties Reduce Cl, K and Sulfidity

• Decrease flue gas temperatures Lower load or soot blow more

• Decrease carryover rate Optimize combustion controls

• Improve surface cleaning effect Soot blow more efficiently

Flue gas temperature – Soot blow more often

FLUE GAS STICKY TEMPERATUREAt a flue gas temperature >500oCthe deposits on tubes quicklyreach a maximum strength in lessthan one hour.

Cool off the flue gas beforeexiting the super heaters

Most soot blowers in the superheater

Innovative soot blower operation

Individual actuators regulating steam flow

1. Soot blower (SB)starts travelling intoboiler, SB mechanicalarm starts steam flow

2. SB reaches innerend point, turns backout. Actuator closessteam flow, leavingonly 5 % coolingflow

3. Reaches homeposition and SBmechanical armcloses poppet valve

HISS operator interface in DCS

Surveillance, Detection and Frequency of problem

HISS monitors soot blowers status continuously

Innovative overlapping operation

Where to focus the steam soot blowing?SuperheatersSoot blow more while saving steam Maintain Tgas < Tsticky

EvaporatorSoot blow more at screen and upper evaporator, while saving steam with one-way steam flow

EconomizerSave steam by soot blowing as normal, with one-way steam flowPreventive cleaning with infrasound

Flue gas coolerPreventive cleaning with infrasound

Mill experience

Recovery boiler: 2700 ton DS/dayManufacturer: Kvaerner (Valmet) 1999No soot blowers: 80 fully retractableNo of headers: 2Start-up: April 2016

ResultsIncreased soot blowing by 30 %Reduced soot blower steam consumption by 33 %Increased average boiler load from 101.3 to 109.2 ton DS/hLower flue gas dP, in spite of higher boiler load

Mill experience

• Issues with the evaporators led to changes in liquor and subsequently ash characteristics

• The ash changes are considered very significant since clogging of ESP took place, which is rare

• Increasing soot blowing to 200% was successfully performed by the operators, to prevent clogging of the boiler. (Clogging of the ESP can’t be prevented since no soot blowers in the ESP)

Mill experience

References and resultsBoiler size, TS/day No of soot

blowersSteamsaving (%)

Increased soot blowing (%)

Other results

1 400 60 35 30 Start-up May-2019, guaranteed minimumsavings 34 000 ton (1.11 kg/s)

2 700 80 35 30 Production increase 6 %, while saving 65 000ton steam/year. Now operating 18 monthcontinuously thanks to HISSTM (2.125 kg/s)

2 400 100 23 50Increased production with remained boiler up-timeincombinationwithsavingsteam

800 24 0 100Extend time between water wash andincreased production

1 050 23 0 100Elimination of stops for cleaning betweenplannedrevisionstops.

1 500 64 35 30Production increase 5 %, while saving 26 000ton steam/year (0.85 kg/s)

One ton of process steam is worth €10 – €151 kg/s steam (450oC / 60 bar) equals roughly 0.5 MW electric turbine output**with 3 bar back-pressure turbine and turbine overall efficiency 71 %

Sustainable soot blowing – What can I Save?

• Increased power generation from recovery boiler• Use steam for mill processes• Reduced feed water make-up• Improve boiler availability with more cleaning capacity• Reduce compensation firing in power boiler• Reduce wear on heat exchangers

2. Infrafone, Technology Principles

Infrasound

Infrasound principles

fu⋅

=π

ξ2

Infrasound principles

Infrasound, recovery boiler applications

Economizers

SCR

Air pre-heaters

ESP

Ducts

Flue gas temp range500 °C > T > 140 °C

Domtar Kingsport, Black Liquor Recovery Boiler

Situation prior installation-The inlet vanes to each precipitator was water washedevery 3-4 weeks

Infra sound cleaners: 2 x APX2000 Cleaning area: Economizer and 2 parallel goose necksFuel: Black liquor, Sulphur free process

Recovery references

Domtar Kingsport, Black Liquor Recovery Boiler

Result• The duct is clean• Infrasound Cleaners had significant cleaning effect

in the ECO, keeping dP low and stable

Recovery references

Stevenson RockTenn, Black Liquor Recovery Boiler

Situation prior installation-Plugging problem required manual cleaning of goose neck to be carried out every 6-7 days.-Precipitator failure required manual cleaning to be carried out every 20 days-Due to precipitator performance, full boiler operation was not allowed-Availability of boiler <85%

Infra sound cleaner: 1 x APX2000 Cleaning area: Goose neck and precipitatorFuel: Black liquor, high sulphur

Recovery references

Stevenson RockTenn, Black Liquor Recovery Boiler

Result• The plugging and fouling issues eliminated, availability of boiler >95 %.• 10°F decreased outlet flue gas temperature,

estimated fuel savings equal to $300,000/year.• State allowed for 15% increased boiler production

rate based on stack tests.• The precipitator has been tested for stack particulate

emissions of 0.34 g/GJ. The environmental permit level is 1.36 g/GJ.

• ROI in only a few months of avoided outages.

Recovery references

Korsnäs Frövi, Black Liquor Recovery Boiler

Situation prior installation-The duct was at this time cleaned with four steam soot blowers-Water washing was necessary every other day-Shutdown for water washing every 6 weeks

Infra sound cleaner: 1 x APX2000 Cleaning area: Duct between boiler and economizerFuel: Black liquor, pH 10.5

Recovery references

Korsnäs Frövi, Black Liquor Recovery Boiler

Result• All plugging and fouling issues eliminated• Differential pressure is kept low and stable• Water washing has been completely eliminated• Two steam soot blowers have been shut down.

The other two are at reduced operating levels.• Pulp production records have been achieved.• Return of investment has shown to be less than

six months.

Recovery references

Korsnäs Frövi, Black Liquor Recovery Boiler

Recovery references

Before infrasound cleaning: Very unstable differential pressure (green). Clogging of the duct also was related to unstable temperature in the smelt spouts (red, blue).

With infrasound cleaning: Stabilized differential pressure (green) and smelt spouts temperatures (red, blue).

Pulp production records were achievedOperating personnel signal significant improvements in boiler OEE

Thank you!