Reasonable Progress (RP) Four-Factor Analysis of Control Options 

For 

Roseburg Forest Products Co./Missoula Particleboard

I. Source Description 

 Owner/Operator: Roseburg Forest Products Co. 

 Source Type: Steam Generating Unit/Process Heat 

 RP Emission Sources: Wall-Fired Sander Dust Boiler - 1969 Babcock & 

Wilcox suspension burner rated at 55 

MBtu/hr 

 

 ROEMMC Sander Dust Burner - 1978 ROEMMC 

suspension burner rated at 50 MBtu/hr 

 SolaGen Sander Dust Burner - 2005 SolaGen 

suspension burner rated at 45MBtu/hr 

Roseburg Forest Products Co., processes raw wood fiber into particle board. The process 

begins by reducing the moisture content of the raw material in a pre-dryer. Next the dry 

material is blended with resin and pressed to produce particle board. Additionally, there 

are six final dryers that produce dried wood furnish for face and core material in the 

particleboard. This Reasonable Progress analysis focuses on three emitting units at the 

Missoula Particleboard facility, listed above. The SolaGen burner provides heat for the 

pre-dryer. The sander dust boiler provides steam for facility processes. The combined 

heat (exhaust) from the sander dust boiler and ROEMMC burner provide heat for the 

final dryers. 

The final dryers are organized into two production lines. Line 1 is a multi-platen batch 

press, followed by four final dryers. Line 2 is a continuous press, followed by two final 

dryers that produce the dried wood furnish for face and core material in the particleboard. 

The configuration of the boiler and ROEMMC burner is as follows. A horizontal 

manifold connects the two exhausts stacks prior to Line 1 and 2 dryers with the ability to 

divert either exhaust stream directly to the atmosphere in the event of an emergency or 

malfunction. Following the common manifold exhaust passes through both Line 1 and 

Line 2 processes. Line 1 (dryers 1-4) each exhaust to their own multi-clone before the 

four exhaust streams are recombined and emitted to the atmosphere through a common 

stack. Line 2 (dryers 5-6) each exhaust to a multi-clone. Both dryer 5 multi-clone and 

dryer 6 multi-clone have individual stacks that emit to the atmosphere, but it is assumed 

that these stacks would be combined if add-on controls were applied to Line 2. 

The SolaGen burner utilizes a low NOx burner (LNB) to the combust sander dust fuel. 

Also, flue gas reinjection (or flue gas recirculation, FGR) is utilized to reduce NOx
emissions further. Exhaust from the burner is routed to the pre-dryer where the raw wood 

is introduced to reduce the moisture content (initially approximately 50% moisture) by 

80% or more. After the pre-dryer, emissions are controlled by a cyclone, a wet 

electrostatic precipitator (WESP) and a regenerative thermal oxidizer (RTO). 

Reasonable Progress Evaluation of Nitrogen Oxide (NOx) Emissions

Step 1: Identify All Available Technologies 

 Selective Catalytic Reduction (SCR)

SCR utilizes a nitrogen based reagent (usually ammonia) injected in the flue gas to 

enhance the reduction reaction of NOx over a metal based catalyst to nitrogen and water.

Some of the reagent injected will not react with the flue gas and will be emitted (this is 

referred to as ‘ammonia slip’). However, low levels of ammonia slip are associated with 

properly operated SCR. NOx emission reductions associated with SCR on a variety of 

source categories can be as high as 95%. The optimal temperature range for most SCR 

catalyst ranges from 600 degrees Fahrenheit to 800 degrees Fahrenheit (Plum Creek 2011 

Response, page 5). The level of control possible is dependent on the catalyst, the 

temperature of the reaction, the amount and location/s of reagent injected, exhaust gas 

constituents that prevent the desired reaction, and the ability to control the system during 

changes to combustion and flue gas characteristics.

 Regenerative SCR (RSCR)

 RSCR uses a regenerative thermal oxidizer (or waste heat transfer system) to bring cool 

exhaust gas back up to the temperature required for SCR catalyst to be effective at 

reducing NOx to nitrogen and water. RSCR is a good option for exhaust gas that has 

constituent that may require removal prior to introduction into the catalyst (to prevent 

fouling or plugging), such as high particulate matter (PM) concentrations in the exhaust. 

 Selective Non-Catalytic Reduction (SNCR)

SNCR involves the injection of a nitrogen reagent (ammonia or urea) in the hot 

combustion zone (1600 to 2100 degrees Fahrenheit) to reduce NOx to nitrogen and water 

without the use of a catalyst. Levels on control may vary widely based on case specific 

conditions including injection temperature and residence time, mixing characteristics of 

the flue gas and reagent, and constituents of the exhaust gas that may reduce the desired 

reduction of NOx. 

 SNCR/SCR Hybrid

This hybrid approach involves injecting the reagent (ammonia or urea) into the 

combustion chamber (which is a higher temperature zone than traditional SCR injection). 

This provides an initial reaction that is similar to SNCR systems. A catalyst is placed 

downstream to further the reduction of NOx and any reagent that remains. 
Combustion Controls

 

 Staged Combustion

Staged combustion can be achieved through a wide variety of methods and techniques, but in 

general always creates a fuel rich zone followed by a fuel lean zone. This reduces the peak flame 

temperature and the generation of thermal NOx. 

 Fuel Staging

Fuel staging is a technique that utilizes 10% to 20% of the total fuel input downstream from the 

primary combustion zone. The fuel in the downstream secondary zone acts as a reducing agent 

reducing NO emissions to N2. Natural gas or distillate oil are usually used in the secondary 

combustion zone. 

 Low NOx Burners (LNB)

LNB stage the combustion process by injecting fuel in a rich state and injecting excess air 

surrounding the fuel rich area to complete combustion and reduce the peak flame temperature. 

LNB are often employed with separated overfire air (SOFA or OFA) to further ensure complete 

combustion. 

 Overfire Air (OFA)

OFA is a technique in which some combustion air is diverted from the burner to a location 

downstream from the burner and flame front. This creates a staged combustion with a rich 

combustion zone followed by a lean combustion zone, lowering the overall flame temperature 

and thereby, thermal NOx emissions. 

 Low Excess Air (LEA)

LEA reduces NOx generation by reducing the amount of air available for combustion thereby 

reducing flame temperature and NOx. 

 Flue Gas Recirculation (FGR)

FGR reduces NOx emissions by reintroducing a portion of the unit’s exhaust into the combustion 

zone, reducing the available oxygen and reducing the combustion zone temperature. 

 Optimization/Tuning

Optimum combustion conditions (including air/fuel ratio adjustments) reduce the 

generation of all pollutants except for water, CO2, and N2 (which are maximized under 

ideal combustion conditions). Automated, or intelligent, controls include sensors and 

software to optimize the air/fuel ratio (ECR Nov 2011, page 4; WRAP Report) in order to 

maximize the energy recovered from the burning of the fuel and minimize the pollutants 

produced. Plum Creek utilizes intelligent controls (ECR Nov 2011, page 4; 2011 Plum 

Creek Response Document). 
Step 2: Eliminate Technically Infeasible Options 

 SCR

SCR catalysts may be fouled or plugged by exhaust gas that contains high concentrations 

of PM, as is the case with the combustion of wood, biomass, or hog fuel. To prevent the 

premature failure of the catalyst the PM must be removed from the exhaust stream prior 

to the SCR. In this case the exhaust from the PM control equipment will not meet the 

minimum temperature required for SCR to be effective. In addition to these issues, there 

is insufficient space for both PM controls and SCR to be added prior to the dryers. If 

there were adequate space to fit the controls another issue would now be insufficient heat 

being sent to the dryers. For these reasons SCR is considered technically infeasible. 

 SNCR

The exhaust from all of the units act as direct contact heat sources for the drying 

processes at the facility. The use of SNCR would require injection of the reagent prior to 

the dryers introducing ammonia to the product lines. Roseburg has stated that contact 

with ammonia may result in reduced product quality. Specifically ammonia is known to 

stain, or darken, wood. At higher levels of exposure, ammonia can be used to prevent the 

spring-back of shaped/bent wood to the original shape. However, this practice may 

reduce the compressive strength of the wood. Roseburg stated that their product must 

remain light in color to allow for the addition of melamine (which is a white/light stain) 

and/or other staining or coloration. Roseburg has stated that darker products (as would be 

anticipated if ammonia were to come in contact with the product) do not meet the 

demand of their customers. Additionally, Roseburg stated that ammonia may react with 

any formaldehyde based resins having a negative effect on the product. For these reasons 

SNCR is not considered to be technically feasible for the Roseburg product lines. 

 SNCR/SCR Hybrid

Since the PM concentrations would require the PM controls to precede the catalyst 

section of the hybrid system, reheat would be required. RSCR is considered to be feasible 

without firebox/SNCR injection, therefore SNCR/SCR Hybrid systems are not examined 

further. 

 Fuel Staging

In order for fuel staging to be effective at reducing NOx emissions there needs to be 

sufficient space to create two stable zones of combustion. If there is insufficient space 

the secondary fuel and combustion zone will impinge on the primary zone having the 

effect of raising the peak flame temperature and in turn increasing NOx emissions. There 

is not sufficient room within the boiler, ROEMMC, or SolaGen to achieve fuel staging 

while maintaining the with necessary heat input to operate the dryers. The creation of a 

larger combustion zone within the boiler also has the possibility of causing greater flame 

impingement on the boiler wall and tubes, which may compromise their integrity causing 

premature failure. For these reasons fuel staging in considered technically infeasible for 

the boiler, ROEMMC, and SolaGen burners. 
 Staged Combustion

The SolaGen burner is a LNB, which is a form of staged combustion. Therefore further 

staging would not be technically feasible for the SolaGen. The ROEMMC burner’s 

combustion chamber is 1⁄4 the size of the SolaGen’s combustion chamber. Since the 

ROEMMC is much smaller and staged combustion techniques increase the volume of the 

flame front for a given heat input rate, it would be necessary to reduce the overall heat 

input to levels below what is needed to operate the dryers. Staged combustion is 

considered feasible for the boiler in the form of a new SolaGen type LNB. However 

staged combustion in the form of OFA is considered technically infeasible for the boiler, 

see Step 2, OFA for that discussion with regard to the boiler. 

 

 Low NOx Burners (LNB)

As stated earlier, the SolaGen burner is a LNB design. The ROEMMC burner’s 

combustion chamber is roughly 1⁄4 of the size of the SolaGen’s combustion chamber. As 

stated in the Step 2, for staged combustion, LNB designs increase the length of the flame 

front. In order for the ROEMMC to operate as designed (with a rich and lean zone) the 

heat input to the ROEMMC burner would need to be decreased so that a smaller, yet 

longer flame could be created within the same physical space available with the current 

combustion chamber. The reduced firing rate would have the effect of reducing the 

necessary heat input below acceptable levels for operating the dryers. For these reasons 

LNBs are technically infeasible for the ROEMMC burner. LNB are considered feasible 

for the boiler. 

 OFA

The SolaGen burner already utilizes a LNB design making further excess air infeasible to 

support stable combustion. The ROEMMC does not have sufficient space to install OFA 

ports. In addition to space constraints, suspension burners (including the ROEMMC, 

SolaGen, and boliler) need high air flow through the fuel feed auger and burner to 

suspend and fluidize the solid fuel. Splitting the combustion air to OFA ports would 

result in poor and perhaps unstable combustion at the burner tip. Therefore, OFA is 

technically infeasible for all three sources. 

 Low Excess Air (LEA)/FGR

LEA is considered to be technically infeasible because sander dust suspension burners 

require high levels of air in order to fluidize the solid fuel. Poor operation of the burners 

would result with LEA since high excess air conditions are found under the conditions 

necessary to sustain stable combustion. The boiler, ROEMMC, and SolaGen are all 

suspension type burners. 

FGR is a technique having multiple mechanisms for reducing NOx, one of which being 

that it reduces the available oxygen since some exhaust gas replaces oxygen rich ambient 

air (similarly to LEA). As with LEA, some combustion air must be reduced to 

accommodate the recirculating flue gas, which may cause the suspension burner to 

operate improperly. If combustion air is not reduced to maintain proper suspension of 

fuel through the burner additional combustion chamber volume would likely be required 

to accommodate the same heat input while maintaining a reduced flame temperature. 
The SolaGen does imploy FGR, which is accommodated by the size of the SolaGen 

(roughly 4 times the size of the ROEMMC burner). 

All other control options are considered to be technically feasible. The following table 

provides a summary of what controls may be considered technically feasible for each unit 

Emission Unit

Boiler ROEMMC SolaGen

Feasible 

Controls

RSCR RSCR RSCR 

LNB 

Optimization/Tuning Optimization/Tuning Optimization/Tuning

Step 3: Evaluate Control Effectiveness of Each Remaining Technology 

It is important to note that NOx emissions from wood and bark are low when compared

with fossil fuel NOx emissions (on the order of 0.1 - 0.35 lb/MBtu expressed as NO2). 

Thermal NOx generated is less than for fossil fuels due to the low combustion 

temperatures. Fuel bound nitrogen conversion to NOx is dependent on conditions 

including excess air, air staging, heat release rate, and fuel sizing and moisture content. 

Studies have found NOx to vary inversely with fuel moisture content. Smaller fuel 

particles have been known to generate higher NOx emissions because of their increased 

heat release rate (faster burn rate). Fuel NOx emissions can be significantly reduced by 

reducing the available oxygen in the early stages of combustion (Kitto, John B. and 

Steven C. Stultz Ed. Steam: Its Generation and Use, Ed. 41, The Babcock & Wilcox 

Company, 2005). 

 Regenerative SCR (RSCR)

RSCR achieve equivalent reductions to SCR and perhaps higher reductions due to the 

pretreatment of the exhaust gas to remove PM. 70-95% reduction is commonly cited for 

SCR systems on a wide variety of emission units. However, the use of western biomass 

poses several challenges that may reduce the ability to control NOx. Babcock Power is 

currently the only manufacturer of RSCR systems. They believe that for a unit firing 

western wood based fuel the probable removal efficiency would be in the range of 70% 

to 80% (see Babcock Power technical memos). For this analysis Roseburg (and their 

consultant, Golder Associates) assumed that a 75% reduction would be achievable based 

on emissions data from several operating wood fired boilers with the Babcock Power 

RSCR. 

 LNB

LNB are a form of staged combustion and may be able to achieve 50-70% reductions in 

NOx emissions when firing coal, and depending on the design or generation of the burner 

(Kitto, John B. and Steven C. Stultz Ed. Steam: Its Generation and Use, Ed. 41, The 

Babcock & Wilcox Company, 2005). However, NOx reductions are highly dependent on 

the specifics of the burner design, fuel fired, and the operational setting. Roseburg 

presented a control efficiency for LNB applicable to the boiler of 22.2%, which was 

based on information from the LNB vendor. This is not unreasonable considering the 

that biomass produces primarily fuel NOx rather than thermal NOx, and LNB primarily 
reduce the generation of thermal NOx. For the purpose of this analysis we have assumed

that 20% reduction may be achievable. Although we recognize that greater reductions 

may be achieved in practice. 

 Optimization/Tuning

Optimum combustion conditions (including air/fuel ratio adjustments) for reducing 

thermal NOx generation have been identified as an option that can reduce NOx emissions 

by 20 - 30% from a boiler that is not equipped with intelligent controls that include 

sensors and software to optimize the air/fuel ratio (ECR Nov 2011, page 4; WRAP 

Report, Roseburg EC/R 11/16/2011). Roseburg submitted the following information with 

regard to how they operate and maintain the units. 

Operation: 

All three burner systems employ high quality control systems. The boiler and SolaGen 

systems have the combustion controls embedded in Programmable Logic Control (PLC) 

systems. The control drives are VFD variable speed drives for combustion air control 

with induced draft fan furnace draft control and wood fuel feed metering. The fuel 

transport fan for the SolaGen is controlled as well. The standby gas control valves are 

driven by high quality electric control drives with position feedback. The ROEMMC 

burner employs Moore model 352 multi loop controllers integrated with a PLC, and high 

quality electric actuators with feedback. 

To ensure that proper operation of the boiler and burners is maintained at all times, a 

licensed boiler operator is maintained on site whenever the burners and boiler are 

operating. Additionally, to the extent possible, Roseburg shuts down peripheral 

equipment to lighten the load on the boiler. Roseburg employs a staff Electrical Engineer 

with broad experience, highly trained Electricians with instrument and PLC experience, 

and highly trained Millwrights, also with years of experience. 

Maintenance: 

Roseburg utilizes an outside consultant to conduct regularly scheduled performance 

assessments and conducts annual inspections of the boiler and burners. Periodic tune-ups 

are performed by outside consultants that include burner adjustments, air damper 

adjustments, and adjustments on fans and motors. Refractory lining and oxygen sensors 

are also replaced as necessary. Fan balancing and motor adjustments are performed 

annually. If needed, these adjustments are made more frequently by Roseburg’s team of 

on-site technicians and engineers. 

In addition to maintenance, regular cleaning is conducted on the boiler and burners. 

Every three months the boiler is shut down for cleaning. Every month the ROEMMC is 

shut down for cleaning. During every shutdown of the SolaGen (approximately every 10 

days) the SolaGen burner is cleaned. 
Step 4: Evaluate Factors and Present Determination 

Factor 1: Cost of Compliance 

Note: no costs have been analyzed for optimization/tuning since Roseburg already 

follows these practices. Therefore optimization/tuning has no further cost associated with 

its implementation and has not been included in the cost table below. Costs below were 

adapted from costs presented by Roseburg to account for 7% interest and 20 year 

equipment life. 

Unit Control 

Type and 

Control 

Efficiency

NOx

Potential 

Emissions 

(tpy)

NOx

Reduced 

via 

Control 

(tpy)

Capital Cost 

($)

Annual Cost 

($/year)

Average Cost 

Effectiveness 

($/ton 

reduced)

Line 1 - 

Boiler and 

ROEMMC 

(post 

combustion

controls)

RSCR 

(75%) 

202 151 $12,299,970 $2,261,273 $14,975 

Line 2 - 

Boiler and 

ROEMMC 

(post 

combustion 

controls)

RSCR 

(75%) 

92 69 $6,162,966 $1,234,469 $17,891 

SolaGen 

Predryer 

RSCR 

(75%) 

58 43 $3,556,967 $748,097 $17,398 

Boiler LNB 

(20%) 

134 30 $748,190 $70,624 $2,354 

Factor 2: Time Necessary for Compliance 

 RSCR

EC/R presented information to EPA, separately from the information presented by Golder 

Associates that indicates that Babcock Power Inc. believes that systems can be 

operational within eight months from the time an order is made. No information was 

presented by Roseburg Forest Products that would indicate the time necessary to place 

the order or the timeframes necessary to bring the equipment off-line to accommodate the 

retrofit. However, it is appropriate to assume that the process could be completed within 

eight months to one year. 
 LNB - Boiler Only

The technical support document for EPA’s Transport Rule was cited by EC/R with 

respect to the time necessary to retrofit boilers with LNBs. EPA found cases in which 

boilers have been retrofitted with LNB in less than six months. However, this does not 

take into account variable that affect the ability of a company to have equipment off-line, 

such as seasonal variations in business that may require Roseburg to postpone retrofit 

until such time as is appropriate. It could be expected that LNBs could be installed in 

less than 6 months to a year. 

 Optimization/Tuning

All units are already tuned for optimal efficiency and to minimize the units emissions 

profile. It is assumed that no further time would be required to operate the units 

optimally. 

Factor 3: Energy and Non-Air Quality Impacts 

 RSCR

RSCR requires the reheat of the flue gas either through a heat exchanger that utilizes 

plant waste heat, and/or through direct reheat of the flue gas through the use of additional 

combustion or electrically powered heating elements. Roseburg has indicated that the flue 

gas at the boiler exhaust is approximately 572 degrees Fahrenheit and the temperature of 

the exhaust of the ROEMMC varies between 700 and 1050 degrees Fahrenheit. These gas 

streams then mix, along with additional ambient air and pass through the Line 1 and Line 

2 dryers further reducing the exhaust gas temperature to 130 - 155 degrees Fahrenheit. In 

order to reheat the gas stream and operate the RSCR system Golder Associates reported 

that it is anticipated that the following resources would be required or consumed: 

Ammonia Natural Gas Electricity Compressed 

Air

Line 1 RSCR

Boiler & 

ROEMMC

433,000 

gal/year 

9.7 million 

scf/year 

3.6 million 

kWh/year 

7.2 million 

scf/year 

Line 2 RSCR

Boiler & 

ROEMMC

433,000 

gal/year 

4.7 million 

scf/year 

1.7 million 

kWh/year 

3.8 million 

scf/year 

SolaGen

RSCR

304,000 

gal/year 

2 million 

scf/year 

700,000 

kWh/year 

1.3 million 

scf/year 

Additionally SCR catalysts and likewise RSCR may have the potential to emit ammonia (as 

ammonia slip) and generate nitrous oxide (a powerful GHG) if not operated optimally. Catalysts 

must be disposed of, presenting a cost. However many catalyst manufacturers provide a system 

to regenerate or recycle the catalyst reducing the impacts associated with spent catalysts. In 

addition to these considerations, there are issues associated with the production, transport, 

storage, and use of ammonia. However, the regularity with which ammonia is handled has 

reduced the risks associated with its transport, storage, and use. 
 LNB

LNB would reduce the heat rate that could be sent to the units without increasing the volume of 

the combustion chamber. That would have the effect of reducing the mass flow rate and heat flux 

through the dryers. In order to make up for the lost heat it may be possible to add an additional 

heat source (which would have emissions associated with it) or install additional insulation to 

prevent heat loss (where possible and not already in place). It may be possible to reduce the 

amount of ambient air mixed into the exhaust prior to the dryers, but this is unlikely since 

sufficient air flow, in addition to heat, is required to reduce the moisture content of the product. 

Factor 4: Remaining Useful Life 

Roseburg’s 2011 response document indicates that the useful life of their equipment is as 

follows: 

Boiler - 10 years 

ROEMMC - 10 years 

SolaGen - 25 years