Standards Certification Education & Training Publishing Conferences & Exhibits Unit Processes and Optimization Opportunities in the Pulp & Paper Mill Brad S. Carlberg, P.E. Senior Controls & Instrumentation Engineer Waste Treatment Plant Bechtel National Inc. Richland, WA

2 Brad S. Carlberg, P.E. (Control Systems) My Pulp & Paper career began with my 3 rd grade science project in 1965 – who knew? Over twenty years experience in Process Engineering and Process Control specifically with Distributed Control Systems and Programmable Logic Controllers combining extensive experience with both Hardware and Software Design, Programming, Implementation and Startup, including Advanced Continuous and Batch Control Programming. Currently working (less than an hour drive from where he was born) for Bechtel on the Hanford Vitrification Plant in Richland, Washington

3 Lessons learned: understand the equipment and the processes in a pulp & paper mill understand the similarities to other industries understand specific areas where control system optimization can decrease costs and/or increase production

4 The Typical Pulp & Paper Mill There are six main “islands” of automation of the mill: raw material receiving & preparation (the woodyard) the pulp mill the powerhouse the paper mill converting and finishing effluent treatment.

5 THE WOODYARD (RAW MATERIAL RECEIVING & PREPARATION) Debarking Drum is rotates and raw logs pass axially through to remove bark Bark doesn’t make good paper AT ALL

6 THE WOODYARD Pulpwood logs out of debarking drum to the chippers Chips are ”classified” (sorted) by size & species

7 THE WOODYARD (RAW MATERIAL RECEIVING & PREPARATION)

8 Chips pneumatically transported from the Woodyard first to the chip bins and then to fill the Digester

9 THE PULP MILL Lime Kiln (the two rotating cylinders) Gas/Oil fired Dry and Calcine the Lime Mud from the Slaker for reuse in the Causticizer

10 THE POWERHOUSE Multiple stories to house the Kraft Recovery Boiler Like any industrial boiler, EXCEPT burns Black Liquor Produces Green Liquor for Pulping Induced Draft Fan Multiple (~Fifty) Sootblowers Electrostatic Precipitators remove particulate from stack gases Steam feeds Digester, Evaporators, Paper Machine & Turbine-Generator

11 LIQUOR BURNERS IN THE KRAFT RECOVERY BOILER Multiple (~12) burners per boiler Strong black liquor 65% solids Recovers inorganic chemicals as molten smelt that exits the bottom of the boiler into the green liquor dissolving tank to be reused in the digesting (cooking) process

12 % CONSISTENCY (of Wood Pulp Fiber) = 100 x Lbs fiber / (Lbs fiber + Lbs Water ) Can be pumped at 3-5% Can be stored at 15% Rotating Disk Blade microwave

13 BROWN STOCK WASHERS Rotating Cylinders covered with wire mesh pick up a 2” mat of pulp from the vat COUNTERCURRENTLY Wash the pulp mat with water to Remove the weak black liquor Filtrate sucked through the wire mesh by a gravity-formed vacuum into tanks directly below Washed pulp “doctored” off of the rotating cylinders 180 o after pickup

14 BLEACH PLANT TOWERS Towers provide residence time for Bleaching chemicals to react with and to brighten pulp stock 3-Stage: D 1 -Eop-D 2 D=Chlorine Dioxide E op = Extraction with oxygen & peroxide

15 CHLORINE DIOXIDE GENERATOR Environmentally friendly alternative to Liquid or Gaseous Chlorine Bleaching Agent Interlocked to guard against a “puff” (explosion) A great case for MPC control to control C l O 2 density ( g/l )

16 BLEACH PLANT WASHERS Used to remove residual bleaching chemicals from the pulp

17 PULP HIGH-DENSITY STORAGE CHESTS That’s A LOT of pulp Enough for a couple of shifts in case the pulp mill goes down – the paper machine can still run

18 THE PAPER MILL – STOCK PREP The refiners condition the pulp stock when cooking in the digesters is stopped early

19 THE PAPER MILL – STOCK PREP The two plates cut & brush up the fibers Optimize Power/Ton

20 STOCK PREP CLEANERS Centrifugal force separates lights from heavies Remove contaminants or non-uniform sized fibers

21 THE PAPER MILL – WET END Headbox at the far end feeds the Fourdrinier wire Vacuum to remove water

22 PAPER MACHINE – DRY END LOOKING TO WET WET END ~100 yards long Forming section Press section Dryer section Finishing section

23 CONVERTING AND FINISHING Cut the big rolls of paper into transportation-size rolls Rewind the big rolls of paper into transportation- size rolls

24 EFFLUENT TREATMENT Just like a municipal waste treatment plant Aeration Basin Clarifiers Settling ponds

25 OPTIMIZATION OPPORTUNITIES IN THE PULP & PAPER MILL RECOVERY BOILER SOOTBLOWING BLACK LIQUOR EVAPORATORS CAUSTICIZING BATCH AND CONTINUOUS DIGESTERS SCREENING AND REFINING WASHING BLEACHING LIME KILN PULP STOCK PREPARATION, CLEANING, REFINING, AND BLENDING PAPER PAPERMAKING, PRESSING AND DRYING SECTIONS OF THE PAPER MILL

26 PULP & PAPER PROCESS OVERVIEW Shipping Bleach Plant Paper Mill WoodyardDigesterWasher Evaporator Recovery Boiler Dissolving Tank Causticizing Weak Black Liq White Liquor Lime Kiln Strong Black Liq Green Liquor Pulp Mill Hot Buttons Wood Supply Causticizing operation Digester/Washer Production Air Pollution Water Pollution Pulp Quality Chemical and Energy use Maintenance

27 RECOVERY BOILER DCS GRAPHIC

28 RECOVERY BOILER ROTARY SOOTBLOWER Uses high-pressure steam to blow soot off of boiler tubes to improve heat transfer between furnace gases and boiler water Sequence the individual sootblower operation for optimal steam usage Low Temp & High Diff Press signal which sections to blow

29 LIME KILN PROCESS Big energy savings possible here!

30 LIME KILN DCS GRAPHIC Long Deadtime means Good case for Multivariable Predictive Controller CV – Temps MV – ID Fan ASD DV – Production Rate

31 RECAUSTICIZING – traditional control Big chemical savings possible here! Long Deadtime means Good case for Multivariable Predictive Controller CV – Conductivity MV – Green Liquor & Lime feeder ASDs DV – White Liquor Production Rate

32 RECAUSTICIZING – new sensors Big chemical savings possible here!

33 RECAUSTICIZING DCS GRAPHIC

34 BLACK LIQUOR EVAPORATOR Fouling reduces efficiency Automate boilout when fouling decreases heat transfer from steam to liquor

35 EVAPORATOR DCS GRAPHIC

36 BROWN STOCK WASHERS DCS GRAPHIC An Optimum Dilution Factor of 1.0 means that the Lbs wash water equals the lbs pulp stock Less wash water reduces the load on the evaporators i.e. steam usage

37 CONTINUOUS DIGESTER DCS GRAPHIC Kappa Number is the amount of delignification of the pulp fiber For example, brown board will have a higher Kappa Number than bleached pulp White Liquor Analyzer to sense residual chemical Kappa Analyzer to sense fiber delignification

38 BATCH DIGESTERS DCS GRAPHIC Batch Scheduling - Steam Leveling smoothes boiler operation Chip Qualities – uniform moisture Batch digesters- liquor analyzer Better Kappa control Reduce white liquor usage Batch digesters- Kappa analyzer Better Kappa control

39 PAPER MACHINE SCANNER Multiple sensors across width machine width measure: Moisture Basis Weight Caliper (Thickness)

40 PAPER MACHINE SCANNER

41 PAPER MACHINE DRYERS Paper sheet rolls over the steam- heated dryer cylinders to evaporate moisture Optimize Steam Usage to save energy costs

42 IN CONCLUSION After reading this paper and seeing this presentation you now have a better understanding of the equipment and the processes in a pulp & paper mill, you can see the similarities to other industries You have an idea of several specific areas where control system optimization can decrease costs and/or increase production

43 ACKNOWLEDGEMENTS First and foremost, I would not be here today (literally and figuratively) had my Father not spent his entire career with the same pulp & paper manufacturer and, in fact, gave me the raw materials and the technical background for my 3 rd science project I likely would not be in instrumentation & controls had (ISA PUPID Life Fellow) John Lavigne written the book “An Introduction To Paper Industry Instrumentation” which I read immediately following graduation I must thank the pulp & paper mill workers in mills scattered throughout North America from whom I gained the immeasurable experience to write this paper

44 QUESTIONS If you think of questions later: Feel free to call or me at either (509) or (251) or me at either: or