Energy Systems in Board Plants

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Wechsler Engineering and Consulting, Inc. (WEC,
Inc.)

• Energy Systems in Board Plants

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About Wechsler Engineering Consulting, Inc.

• In business since August 2002
• Specializing in combustion processes, energy
  recovery, and air pollution control
• Wood industry is a primary area of activity
• Principal Tom Wechsler
• Engineering degree from Georgia Tech in
  mechanical engineering
• 20 years experience in combustion and air
  pollution control
• American Combustion advanced burner systems
• Von Roll Inc. Incineration, air pollution
  control energy recovery
• GTS Energy energy systems for board plants

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WEC, Inc. Services

• Process Optimization and Troubleshooting
• Combustion optimization furnace tuning
• Optimizing heating performance
• Thermal oil output
• Hot Gas supply for drying
• Steam
• Heater/system fouling
• Slagging issues
• Spark carryover
• Operator Training

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WEC, Inc. Services

• Design and Evaluation
• System expansions capacity upgrades
• Thermal oil loops
• Hot gas
• Add-ons
• Replacements
• Modifications and improvements
• Flue gas re-circulation
• Press exhaust handling
• Fuel handling
• New Systems
• Feasibility studies
• Budget estimates
• Preliminary designs and concepts

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Energy Systems in Board Plants
As a Board plant operator What we would like
from an Energy System
Fuel In
Energy Out
Black Box
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Energy Systems in Board Plants

• What we actually have
• Multitude of components

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Type of Energy for Modern Board Mill

• Direct hot gas energy
• Drying
• Thermal oil energy
• Press
• Log Thawing
• Building Heat
• Wax tank heating and resin preparation
• Steam generation

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Usable Waste Fuels

• Bark from debarking operations (wet)
• Plant waste wood trimmings, reject panels etc
• Rejected flakes/chips from screener
• Fines and sawdust
• Sanderdust from sanding operations

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Combustion OptionsFor Differing Fuel
Availabilities

• Wet wood fuel/bark only reciprocating grates
  typical (current preferred technology), also wet
  cells
• Dry fines Pile burners/underfeed stokers,
  Suspension burners (McConnel type)
• Sanderdust only dedicated suspension burners
• Other system custom configurations possible

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Important Features of a Well Designed Heat-Energy
System

• Provide all of plants process energy needs
• Use as much plant wood waste as possible
• Operate continuously (24 hours/day)
• High reliability and on-line time (typical 340
  days/year or more)
• Automatic operation

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Typical Modern OSB Energy System
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Typical Modern MDF Energy System
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Common Energy System Operational Issues

• Furnace Issues
• Slagging
• Buildups of ashes in heaters, multi-clones, ducts
• System instability - large swings in output or
  system temperatures
• Excessive wear of refractories, castings (grate
  bars), etc.
• Emissions issues (CO, NOx, VOCs)
• Spark Carryover

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Common Energy System Operational Issues

• Performance/thermal output
• Hot gas supply - dryer performance
• Thermal oil output
• Poor pump seal life
• Pump cavitation issues
• Low secondary loop output (below design)
• And others

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Solving Performance Issues Tools of the trade

• Operator discussions/observation of operation
• Visual inspection fire distribution, ash
  quality, equipment etc.
• Plant historical data/trending
• Manometer measure draft
• Gas Analysis O2, also CO, NOx
• Process Modeling Heat and Material Balances
• Lab Analysis
• Fuels
• Ash bottom ash, multiclone, buildups
• Experience

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Example Poor And Erratic Drying Performance

• Case Loss of drying performance over time, up
  to 15-20 of historical
• Review of operations,
• Review of historical data, and
• modeling showed
• With existing control system setup, consistent
  temperature control to dryer difficult, resulting
  in wide swings of hot gas temperature. Dryer
  would ask for more heat at high production rate,
  but (at times) heat supplied at too low a
  temperature. Result too much gas flow, dryer
  plugging
• fuel bed/fire distribution problems, air supply
  issues (Press Air)

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Example Poor And Erratic Drying Performance

• Solution(s)
• Re-tune furnace parameters
• Grate speed
• Fuel feeder rate settings
• Tuned air control loops
• Revised control logic for secondary and blend air
  control to provide steadier secondary air supply,
  to provide
• Steady higher upper furnace temperature (within
  design)
• Consistent higher quality (hotter) hot gas to
  dryer
• Result
• recovered lost dryer performance, and
• Improved consistent dryer performance

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Example Emissions Problems

• Case CO and NOx exceeding permit limits
• Furnace tuning and operator guidelines to
• Optimize Combustion parameters including
• secondary air
• Furnace temperatures
• Flue Gas Recirculation
• Improve loop tuning
• Minor damper adjustements
• Result in CO and NOx reduced by 30-50

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Examples Excessive Fouling And Ash Buildups

• Mechanisms for fouling and buildups in flue gas
  path (heater, ducts, multi-clones, etc) can be
  complex
• Causes of fouling can be one or combination of
  several factors
• Fuels characteristics
• Heater design
• Furnace design
• Ducts and off gas systems design
• Energy system operations
• Other plant operations will also affect energy
  system!

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Excessive Fouling And Ash Buildups

• Methodology for solving issues are similar in
  each case
• Review operations parameters visual,
  temperatures, flows, fuel distribution in
  furnace, primary/secondary air balance
• Lab analysis of fuels to check for fouling
  potential of fuels
• Visual and lab analysis of ash generated
• Review of energy system design weaknesses which
  may contribute
• Review of plant operations (type and amount of
  waste fuels generated, resins used etc.)

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Example Excessive Fouling And Ash Buildups
Severe Heater Fouling
At inlet to heater, after 4-6 weeks operation
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Example Excessive Fouling And Ash Buildups
Severe Heater Fouling
At inlet to heater, after 4-6 weeks operation !
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Solutions Excessive Fouling And Ash Buildups
Severe Heater Fouling

• Case Heater Fouling
• Source High alkali in virgin fuel (bark)
• Solution(s)
• Addition of flue gas recirculation system
• Furnace tuning (improved temperature control)
• Sootblower improvements
• Result decreased shutdown to manageable 3-4
  months period

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Example Excessive Fouling And Ash Severe
Buildups in Multiclone
Tubes severely plugged with ash
Tubes cleaned
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Solutions Excessive Fouling And Ash Buildups
Severe Buildups in Multiclone

• Case Multiclone plugging every 2 weeks or less
  of operation
• Traced problem to additives in resins returning
  back to energy system in plant waste
• Renegotiated resin contract with new supplier to
  eliminate addition of salts
• Result eliminated plugging completely

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Solutions Excessive Fouling And Ash Buildups
Severe Buildups in Multiclone

• Current case
• similar, but ash softening agent cannot be
  removed from resins.
• Customer cannot meter dry fuels to system (all
  or nothing)
• Different solution involving managing waste
  material needed here
• Solution Improve dry fuel metering systems, and
  
• Portion of dry material to be disposed to achieve
  proper fuel balance

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Other ServicesSystem Upgrade Needs

• Secondary thermal oil loop additions and upgrades
• Furnace control improvements
• Fuel changeovers
• Environmental upgrades
• Flue gas re-circulation
• Press exhaust handling
• Temperature control/CO control
• NOx reduction
• Sparks
• Thermal oil loop distribution/piping/flow
  analysis to improve pump life and loop
  performance
• Economizer additions (feasibility)

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Other Services System Upgrade NeedsExpansion
or add on to existing loop(s)

• Use of unused thermal oil capacity to add or
  upgrade thermal oil loops
• Evaluation of existing thermal oil capacity by
• Analysis
• On site observation/measurements
• Knowledge of existing thermal oil systems
• Investigation of options
• Specifying process equipment
• Design
• Flow/Piping analysis of primary and secondary
  loops
• Layouts
• Piping modifications
• Pump/pump skid modifications

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ExampleExpansion of existing log wash loop
Existing loop capacity (actual measured) of 12 mm
Btu/hr

• Addition of new heat exchangers to increase loop
  capacity to 40 mm Btu/hr

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Example System Upgrade NeedsExpansion of
existing log wash loop Pump skid modifications
to accommodate larger pump

• Original Skid

Fitting larger pump in
Modified Skid
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Example System Modification NeedsFuel
Conversion of Thermal Oil HeaterSanderdust to
Natural Gas

• Existing system inspection
• Heater evaluation (for added output capacity)
• Suspension burner replacement
• Primary loop modifications
• Flow/piping analysis
• Layouts

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Other Services Equipment Design

• Ash Conveyor Redesign for Replacement

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Other ServicesEquipment Modifications

• Pump Skid Modifications

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Other Services System Upgrade NeedsAddition to
Existing Plant CapacityFeasibility Evaluation

• Design of system add-on
• Evaluation of existing plant balance
• Energy
• Waste fuels (plant mass balance)
• Evaluation of future plant needs
• Investigation of options
• Wet fuel system
• Direct suspension burning
• Gas fired plant heat
• Preliminary layouts
• Budget costs for each option (Gate 2)

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Other Services New SystemsBrown Or
GreenfieldFeasibility Evaluation And Preliminary
Plant Design

• Feasibility Study
• Preliminary plant fuels/energy balance
• Technical feasibility analysis and concept
  developments
• Air pollution control systems (WESPs, other)
• support regulatory and permitting issues
• Co-generation options (if applicable)
• Alternate Fuels
• Technical specifications requirements
• Installation specifications
• Specification and preliminary plant design/layout
  drawings
• Supplier Qualification/List
• Bidding and bid evaluation

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• Thank You!
• The End