CPPA Bleaching Committee

Technical Session, October 22, 1996

 

53 person attending                                                  (See also Appendix 4)

 

 

1.  Chlorine Dioxide Substitution and “ECF Best Practices” Survey Results - Doug Pryke (see Appendix 3)  co-author - Doug Reeve

 

·       2 questionnaires have been sent to all mills in Canada to 42 mills.  38 have been returned.

·       36 ECF bleaching lines :

·       29 SWD,   7 HWD

·       2 subcategories

·       O2 delignification

·       Non-O2

 

·       10 mills ECF in 1987,   47 mills in 1996

·       All bleach plants use >50% ClO2 substitution

·       Average % substitution in Canada is 87%

·       60% of bleach plants only produce ECF pulp

·       Most popular sequence:    DEopDED

·       Brightness:

·       88-90  mostly used

 

·       Kappa Number in:

·       Ave softwood   28.7

·       O2 delignification  17.5

 

·       Black Liquor Carryover:

·       O2       8 kg/t saltcake and

·       COD:    Both O2 and conventional the same

 

·       Do stage:

·       Low consistency typical

·       2.5 pH:    65% of bleach plants add H2SO4 for pH control

·       Shortest:   6 minutes,       Longest   75 minutes

 

·       Kappa Factor:

·       O2 delignification:                  ave. 0.2

·       Conventional:                        ave. 0.23

 

·       Eop Stage:

·       10% of conventional mills have Papricycle

·       35% have O2 delignification

·       pH:   10.5-10.8

·       O2 and H2O2 used in 90% of bleach plants

·       O2:   5.5 kg/ADMT,      H2O2:   3.4 kg/ADMT

·       DEop Delignification:  80%

·       Extracted  Kappa No.:   conventional:   4-4.5 ,   O2 delignification:   3.5

·       Time:    15 minutes to 2 hours

 

 

 

·       D1 stage:

·       160 min

·       Upflow pH:   3.8-3.9 ,    end pH:   3.3-3.8

·       Optical sensors

·       Brightness:   83 ISO average

·       Retention time:

·       Longest:             200 minutes

·       Shortest:            110 minutes

·       O2 delignification:    4 hours highest

 

·       Sequence Kappa Factor:

·       Conventional:   0.40

·       O2 delignification:   0.45  average

 

·       Bleaching Efficiency:

·       Bleaching for conventional pulp is more efficient for conventional based on Kappa Factor

·       Overall costs:   conventional higher:   $45-55/ton

·       Difference:   $9.25 less for O2 delignification than for conventional bleaching.

 

 

Optimization Analysis

·       Sorted by kappa Number and final brightness

·       2 groups;

·       Relatively “low”

·       Relatively  ”high”

 

·       Optimization Summary    Figure 16

·       O2 mills

·       Ultimate goal:     minimizing costs and ClO2 consumption   and maximizing  brightness

·       Figure 17

·       O2 delignification:

·       significant difference:    mills with the  high chemical consumption had relatively low retention times.

·       Conventional lines:

·       Lower brightness mills optimizing for cost

·       Higher costs optimizing for brightness

·       Retention time not much difference

·       Cost:    Fig 26

 

 

 

SUMMARY:      See page 25 of paper

 

 

QUESTIONS/COMMENTS:

·       Dennis Owen:   most mills he has worked with, with high emissions from bleach plant scrubber solved their emission problems by optimizing the Bleach Plant operation to lower ClO2 usage and residuals so that less ClO2 residual gas goes to the scrubber.

·       If mill can control carryover and kappa number lower costs will occur with lower ClO2 emissions.

·       Additional comments are attached in Appendix 4

     

 

2.  Report on Visits to Mill’s Undergoing Closure Trials (Scandinavia and North America)

             - Dennis Owen

 

·       4 or 5 papers have been published.

·       Dennis will give reference for minutes.  (See Appendix 4)

 

 

      2.1  Guvon mill         January  paper in Altanta

·       2 ECF bleach plants

·       One of the few mills that have secondary treatment in Scandinavia

·       M/C  O2 delignification

·       Green liquor filtration

 

·       ICT process

 

·       Hardwood pulp

·       Digester

·       Diffusion washers

·       Very, very good washing thus low chemical costs

 

·       Softwood line

·       Diffusion washing

·       Very, very good washing

 

 

·       DoEopDEpD

·       SWD   kappa no 14,      13 kg ClO2/mt   consumption    very low

 

·       Emission

·       Year  2000:     COD 15 kg/ADMT,    AOX  0.1 kg/ADMT

 

 

 

 

      2.2  Eka Nobel Paper   95 TAPPI Pulping Conference

·       MVR vacuum pre-evaporation

·       Mechanical recompression vacuum evaporator

·       Closed cycle bleach plant      DoEoDnD

·       Filtrates treated  to a salt solution and metals removal

·       Concentrator (conventional),   then oxidizer,    then salt treatment

·       Water removal

·       Evaporator:           9.64  m3/ADMT

·       total:                  10 m3/ADMT

 

·       Evaporator / concentrator / oxidizer:     main thrush of their project

·       MVR  mechanical vapour recompression

·       Other ideas:

·       Evaporation Flocculation ElectroDialysis

·       Evaporator   water removal

·       Floc  sludge removed

 

 

      2.3  Jaakko Poyry Paper

·       Summarized treatment processes

·       Main objective to produce clean water and remove the nasties (COD, salts, organic materials)

·       ME evaporation

·       MVR process

·       Membrane filtration

·       Final disposal of residue

 

·       Cost for operation costs for processes given

·       Evaporation:        $10-15/ADT

·       Treatment:          $  6-7 /ADT

 

·       Evaporation most efficient method

·       If you do not have secondary treatment, this process becomes attractive

·       Stopping the brown stock and liquor getting out of the brown stock area

 

 

 

 

      2.4  ABA Paper

·       Goal 2000

·       Guvon:                            100 m3/adt

·       Most Scan mills              still >80 m3/adt

 

·       Questions:

·       none

 

 

 

 

3.  BFR Update -   Gerald Delaney,  Wheelabrator Water Technologies,  Canton

 

      3.1  BFR overview:

·       Method to recover ECF Bleach Plant filtrates through existing pulp mill recovery processes

·       Based on 6 years of work

·       Takes advantage of Champion’s OD110 process   three stage bleach plant

·       Some degree of countercurrent washing and purge from each stage

·       BFR closing up first two stages

·       Mineral removal process (MRP)

·       Chloride removal process (CRP)

 

·       6-10% increase in evaporation requirements with BFR due to recycle of filtrate for washing versus fresh water washing

 

·       Slide:           Mill with  OD(EOP)D sequence and BFR with Final Stage Closed

·       with O2 delignified pulp should be able to close first two stages

 

·       Issues with closure:

·       High chloride concentration

·       Increased evaporation requirements

·       Higher bleaching costs

·       Build-up of minor wood components

·       BFR addresses these concerns

·       BFR utilizies:

·       O2 delignification

·       100% ClO2 substitution

·       Use of H2O2

 

·       Use of BFR process

·       NaCl into the recovery cycle:

·       Thunder Bay:      50 kg/ADT

·       BFR - Hardwood:   5- 6

·       BFR - Softwood:    8-10

 

 

1. Chloride Removal Process (CRP)

·       Precipitator ash dissolved,

·       Goes to crystallizer

·       Evaporation

·       Salt cake filter removes saltcake to recovery cycle

·       Filtrate contains Cl- ions.    K ions also removed.

·       Efficiency of removal is shown in the graph given

 

2.  Issue:  Increased Evaporation Requirements

·       BFR:

·       Chloride input = low evaporation

·       Low bleach filtrate volume

 

3. High Bleach Chemical Consumption

·       BFR :

·       Low kappa pulp to bleach plant

·       High oxidized dissolved solids

·       Selectivity of chlorine dioxide

 

·       Final D stage

·       Slight increase in chemical demand

 

4.   Build-up of Minor Wood Components

·       BFR:

·       Potassium removal by BFR

·       Highly oxidized dissolved solids

·       Metals removal

 

·       Integration of metal removal process into D100 stage     (slide)

·       D100 washer more of a metal washer than an organics washer

·       Effluent Benefit:

·       Lower colour

·       Lower AOX

·       Lower BOD

·       Lower COD

 

·       Still some components in effluent since last D stage filtrate is not recovered.  If this stage is recovered  -  zero effluent

 

 

 

·       Cost:

·       MRP chemicals

·       CRP chemicals

·       Additional bleach cost, steam, etc.

·       Additional costs:   $4 - 5/ADT

 

·       Start-up in Sept. 1995

·       Partial closure on D100 and Eop Stages

·       Full closure of  first  2 stages by summer 1996

·       By next summer full closure

 

·       Chloride removal sized for both lines:

·       Metal removal for SWD line only

·       Cl- removal:   3 body multiple effect bodies, then to saltcake filter

·       Predict the chloride to level out at  4-5 g/l NaCl

 

·       CRP:

·       95% chloride removal

·       85% potassium removal

·       85% saltcake recovery

 

·       Metal Removal Process   (MRP)

·       Untreated filtrate through multimedia filters to remove suspended matter

·       Softener to remove metals

·       Performance

·       92 % removal of Ca, Mg, Mn

 

·       Problems:

·       Mechanical failure

·       Filtration capacity

·       Softener pluggage

·       Resin oxidation

·       Water infiltration

 

·       Remaining issues:

·       Reduce water infiltration

·       Optimize control of filtrate recovery

·       Closing up of filtrate recycle

 

 

 

 

 

 

      3.2  Metals Removal  -  Bob Caron, Champion

·       Have eight full days of BFR operation thus far.

·       Preliminary operating data

·       Slide handed out - Preliminary BFR Demonstration Results

·       Predicted numbers are for two stage closure   (D2 stage filtrate to sewer)

·       Full recovery of E stage   and full recovery of Do stage except for 100 gpm

·       D1 on chart is the first D stage (we call as Do)

 

 

·       Washer wash water

·       Prebleach washer:    use treated filtrate and some untreated D1 filtrate

·       D1 washer use treated filtrate

·       Eop washer - ???

·       D2 washer - condensates

 

·       Metals profile:

·       Metal management is important

·       Calcium off D100 stage   - 80% reduction with BFR

·       Oxalate data  (Ox)   (would indicate scaling)   -  some problem with the data thus it is not representative.

 

 

·       Questions/Answers:

·       Prebleached washer filtrate goes to brown decker and eventually back to O2 and recovery cycle.

 

 

 

 

 

4.  Mill Roundtable on Water Reduction and Closure

 

      4.1  Eop Filtrate Recycle at Skookumchuck - Gary Billmark

·       2 phases for recycle

·       Phase 1 recycle Bleach Plant filtrate back to the liquor cycle

·       Phase 2 - use of fully oxidized white liquor in the bleach plant

 

·       Benefits phase 1

a) Reduced colour

·       Eop stage accounts for 40-50% of mill effluent colour

·       Running 1 CU higher colour

b) Reduced effluent flow

c) Increase soda recovery

d) First steps to mill closure

-------------------------------------------------------------------------------------------------------------

·       Recovery boiler designed for 25 g/L chloride

·       Implemented July 23, 1996,    slowly recycling 10% of flow,   100 gpm

·       Ongoing monitoring

·       Chloride in WL

·       Has increased from 1.2-2   to 3-3.5  with recycle of 10% of filtrate

·       NPE’s    (non process elements):

·       Corrosion rates   (tabs)

·       Daily process data

-------------------------------------------------------------------------------------------------------------

·       WL oxidizer supplied by Air Products

·       Just partial oxidization at this time.     By end of January full oxidation

·       Some modifications required before full oxidation before increasing recycle rate

·       Mill down to 60 m3/ADT effluent

-------------------------------------------------------------------------------------------------------------

·       Questions:

·       maximum recycle rate:

·       Tom Mullens:    40% recovery for 8g/L NaCl

      4.2  Scrubber Filtrate Recycle at Portage du Fort  - Gilles St.-Jean

·       Sept. 93:    new R8/R10 installation

·       New WL scrubber also installed.

·       Both makeup WL and hot water is added.

·       Water added to keep sufficient liquid in scrubber for scrubbing.

·       Control WL flow by pH of the scrubbing media

 

·       Treat D1, D2 vents and vent from R8 in new scrubber

·       Spent WL goes to the saltcake dissolving tank.

·       Control density and pH before going to the recovery boiler

 

·       Recover saltcake and WL together for 16 hours per day.   Rest of time sewered.

 

·       Questions/Answers:

·       Scrubber efficiency not known at this time

·       Average use:   2.5 gpm WL

·       ClO2 generator:   42 tpd.    Presently run a lot lower.

·       WL not filtered before use.

 

 

 

 

 

      4.3  System Closure - The Questions to Ask

                  Paprican’s Overview on Closure - Richard Berry

·       Summary from AET workshop that Doug Pryke put on 2-3 weeks ago on System Workshop-

 

·       The questions to ask and answered by a group of experts:

 

·       Group of questions:    Questions and answers in the appendix

      1.   Environmental Significance (I)

 

      2.   Environmental Significance (II)

 

      3.   Technology Options (I)

 

      4.   Technology Options (II)

·       Backing away from extreme delignification  (yield lost)

 

      5.   Economics (I)

·       Quality of chips into process

·       Lower kappa number (extended cooking)

·       O2 delignification       - low kappa number for TCF and low chloride for ECF recycling

·       Brown line closure

·       Spill control and recovery

 

      6.   Economics (II)

·       Extensive washing

·       Capital costs

·       Operating costs

·       Energy cost

·       Wood demand increases

 

           

      7.   Further Technology Issues (I)

·       Unlikely to have dioxin formation in recovery boiler due to high sulphide levels.

·       If separate incinerator,  dioxin more likely to be formed since no sulphide present.

 

      8.   Further Technology Issues (II)

·       Pulp quality problems

·       Either very little data in this area or very confidential,   thus no answers

·       Tear/tensile  not only parameter

·       Fibre surface properties

·       Chloride is the difference between the two sets of process:   ECF, TCF

·       No answer for pulp quality

 

      9.   Further Technology Issues (III)

·       Emphasis on environmental effects monitoring will continue

·       Effects monitoring

·       System closure by marketing effects versus environmental or quality aspects

 

 

·       Doug Pryke:

·       Need terminology  to be used instead of   “low environment impact”

·       Need equal balance

·       Low incremental changes towards system closure will be done:

·       e.g., lot more than reducing bleach plant effluent impact,   e.g., odour concern

 

·       Chris will look into doing this for the annual Meeting

 

 

 

 

 

 

      4.4  Bleach Plant Water Reduction Program at Kamloops - Gary Berndt

·       MIM - minimum impact manufacturing Vision

·       Minimum environmental impact

 

·       What is it?

·       Vision identifying where Kamloops is going

·       Philosophy

·       Strategy

·       Tool

 

·       Consider stakeholders:    customer,  employees ,shareholders,,  community

·       Always making changes and improving

·       Continuous improvement

·       Improve process, not downstream results

 

·       MIM application to Bleach effluent reduction

·       Move to BER:    Bleach effluent reduction

 

·       Water reduction why?

·       P&P large water user   - 3rd largest industrial user in the USA

 

 

·       Value of water usage reduction

·       Save $

 

·       Total Reduction to 250 m3/ADT in 1970  to 50m3/adt   in 2000

·       Bleach 70 to 30 m3/adt

 

·       “A” Mill   

·       DEEpDEpD

·       Papricycle

 

·       “B” Mill

·       Kamyr EMCC

·       1040 tpd

·       DEEop(DE)D

·       Papricycle

·       Short extraction at the bottom of D1 tower thus (DE)   versus  Dn used by others

 

·       Bleach plant Effluent - 50 cu m / t

·       Total effluent flow   ~120,000 m3/yr  ??

·       Effluent colour  -  1995-96   to   100 tpd

·       Peroxide to Eo stage in 1980 for colour reduction

·       1988 - higher ClO2 substitution

·       1992 - 100% ClO2 substitution

·       1995 Kamyr EMCC and lower Kappa Numbers

 

·       Modernization

·       B mill

·       Increase production by 100 tpd

·       O2 delignification

·       Bleach effluent flow reduction

 

·       Bleach effluent flow reduction

·       Convert Do to M/C                                         20

·       Reconfigure showers                                     11.3

·       Instrumentation                                             ?

·       Do filtrate recycle      low screw dilution           5.4

·       Eop filtrate recycle to brown                            3?

 

·       Total reduction to 0 for alkaline effluent and 5 m3/t for acid effluent

 

·       Benefits:

·       Reduced pumping costs

·       Chemical savings

·       Increase retention time in ASB

·       All effluent properties improved

 

·       Timing

·       MC conversion:                     Sept. 1997

·       O2 delignification:                  Dec. 1997

·       Eo filtrate recycle:                 March 1998

 

 

 

      4.5  Reduced Water Consumption at Irving - Don McCabe

·       D/C Eop D Ep D    bleach plant

 

·       #1 M/C                     170 fpm             450 tpd

·       #2 M/C                       70 fpm                        150 tpd

·       #3 M/C                     130 fpm             300 tpd

 

·       Key projects:

·       Andritz Press

·       Replace mould and Kamyr press of # 3 M/C with this

 

·       Recovery boiler rebuild

·       New electrostatic precipitator

·       New teller scrubber packing

·       Auxiliary equipment rebuild

 

·       Lime kiln and precoat upgrades

·       Capacity increase

·       ID fan

·       150 tpd increase to 240 tpd

·       Energy from 10.5 to 7.5 mm btu/ton

·       New refractory, etc.

·       DCS system

 

·       Bleach Plant:

·       Honeywell  DCS system  1995

·       Reduced bleaching chemical cost

·       Reduce effluent especially with o2 delignification

 

·       Increase pulp storage

·       New 800 t Bleach HD Storage:   Fall 1995

 

·       Enhanced spill recovery system

·       Additional sumps

·       New WBL storage:   Spring 1995,     1,000,000 gal

·       New 50% BL storage tank

 

·       Evaporator expansion

·       High solids crystallizer

·       Additional effect

 

·       Condensate stream stripper system

 

 

·       Fibre line  EIP  environment improvement project

·       Brown stock washing

·       New single line Sunds wash presses

·       Replace two lines

·       New knotters

·       New pressure screening

·       Brown stock screen

·       Sloted screens, pressurized

·       Close screen room

·       O2 delignification

·       2 presses

 

·       Small item to do:

·       Water balancing

·       Wire cleaning showers

·       Recycling to seal tanks

·       Warm and hot water reuse instead of sewering.   Still sewering these

·       Repulper dilution due to limitation to thick stock pumps.

 

·       Water usage now   >100 m3/t   still high

 

 

 

 

 

      4.6  Water Reduction Program at Canton - Derek Brown,  Champion  Canton

·       1908 start-up initially

·       Water and colour reduction programs

·       1990 modernization process

·       650 SWD pine line,   O2 delignification  and 100 m3/t

·       Old mill converted to 775 tpd hardwood

 

·       Water reduction

·       Cooling tower for pulp mill heat exchanges

·       MEE condensate segregation

·       Condensate stripper

·       Replacement of multiple unit equipment with larger units   (e.g., reduce number of washers)

 

·       Cooling water system sources

·       Evaporator surface condenser

·       Turbine cooling water

·       Secondary blow heat condenser

·       Turpentine condenser

·       Bleach Plant effluent cooler

·       Excesses blow heat water

 

·       Paper M/C reduction

·       Vacuum pump seal recirculation system

·       White water strainer

·       White water reclaim systems

 

·       Present limit:

·       Water use 29 MM gallons per day

·       Plus 0.9 MM gpd  water being feed to city of Canton.