Reasonable Progress (RP) Four-Factor Analysis of Co ntrol 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 fi ber 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 produ ce particle board. Additionally, there are six final dryers that produce dried wood furnis h for face and core material in the particleboard. This Reasonable Progress analysis fo cuses 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 fo r facility processes. The combined heat (exhaust) from the sander dust boiler and ROEM MC 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 i s 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 atmosp here 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 emi t to the atmosphere, but it is assumed

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

The SolaGen burner utilizes a low NO

x burner (LNB) to the combust sander dust fuel. Also, flue gas reinjection (or flue gas recirculati on, FGR) is utilized to reduce NO

xemissions further. Exhaust from the burner is rout ed to the pre-dryer where the raw wood

is introduced to reduce the moisture content (initi ally approximately 50% moisture) by 80% or more. After the pre-dryer, emissions are co ntrolled by a cyclone, a wet electrostatic precipitator (WESP) and a regenerativ e thermal oxidizer (RTO).

Reasonable Progress Evaluation of Nitrogen Oxide (N O

x ) Emissions Step 1: Identify All Available Technologies Selective Catalytic Reduction (SCR) SCR utilizes a nitrogen based reagent (usually ammo nia) injected in the flue gas to

enhance the reduction reaction of NO

x over a metal based catalyst to nitrogen and water. Some of the reagent injected will not react with th e 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. NO

x emission reductions associated with SCR on a varie ty of source categories can be as high as 95%. The optima l 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 locatio n/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 wast e heat transfer system) to bring cool exhaust gas back up to the temperature required for SCR catalyst to be effective at reducing NO

x to nitrogen and water. RSCR is a good option for e xhaust gas that has constituent that may require removal prior to intro duction into the catalyst (to prevent fouling or plugging), such as high particulate matt er (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) t o reduce NO

x to nitrogen and water without the use of a catalyst. Levels on control ma y vary widely based on case specific conditions including injection temperature and resi dence time, mixing characteristics of the flue gas and reagent, and constituents of the e xhaust gas that may reduce the desired

reduction of NO

x .

SNCR/SCR Hybrid This hybrid approach involves injecting the reagent (ammonia or urea) into the combustion chamber (which is a higher temperature z one than traditional SCR injection). This provides an initial reaction that is similar t o SNCR systems. A catalyst is placed

downstream to further the reduction of NO

x and any reagent that remains.Combustion Controls

Staged Combustion Staged combustion can be achieved through a wide va riety 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 NO

x .

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 downstrea m secondary zone acts as a reducing agent reducing NO emissions to N 2 . Natural gas or distillate oil are usually used in the secondary

combustion zone.

Low NO

x 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 combusti on 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 cr eates a staged combustion with a rich combustion zone followed by a lean combustion zone, lowering the overall flame temperature and thereby, thermal NO

x emissions.

Low Excess Air (LEA)

LEA reduces NO

x generation by reducing the amount of air available for combustion thereby reducing flame temperature and NO

x .

Flue Gas Recirculation (FGR)

FGR reduces NO

x emissions by reintroducing a portion of the unit’s exhaust into the combustion zone, reducing the available oxygen and reducing th e combustion zone temperature.

Optimization/Tuning Optimum combustion conditions (including air/fuel r atio adjustments) reduce the generation of all pollutants except for water, CO 2 , and N 2 (which are maximized under ideal combustion conditions). Automated, or intelli gent, controls include sensors and software to optimize the air/fuel ratio (ECR Nov 20 11, page 4; WRAP Report) in order to maximize the energy recovered from the burning of t he 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 g as 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 re moved from the exhaust stream prior

to the SCR. In this case the exhaust from the PM co ntrol equipment will not meet the minimum temperature required for SCR to be effectiv e. 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 anoth er 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 con tact heat sources for the drying processes at the facility. The use of SNCR would r equire 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 exposur e, ammonia can be used to prevent the spring-back of shaped/bent wood to the original sha pe. However, this practice may reduce the compressive strength of the wood. Rosebu rg 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 s tated 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 s tated that ammonia may react with any formaldehyde based resins having a negative eff ect on the product. For these reasons SNCR is not considered to be technically feasible f or the Roseburg product lines.

SNCR/SCR Hybrid Since the PM concentrations would require the PM co ntrols to precede the catalyst section of the hybrid system, reheat would be requi red. 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 reduci ng NO

x emissions there needs to be sufficient space to create two stable zones of comb ustion. 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 NO

x emissions. There is not sufficient room within the boiler, ROEMMC, o r 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 t he 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 sta ged combustion. Therefore further staging would not be technically feasible for the S olaGen. The ROEMMC burner’s

combustion chamber is 1⁄4 the size of the SolaGen’s c ombustion chamber. Since the ROEMMC is much smaller and staged combustion techni ques increase the volume of the flame front for a given heat input rate, it would b e 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 NO

x Burners (LNB) As stated earlier, the SolaGen burner is a LNB desi gn. 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 de signs increase the length of the flame front. In order for the ROEMMC to operate as design ed (with a rich and lean zone) the heat input to the ROEMMC burner would need to be de creased so that a smaller, yet longer flame could be created within the same physi cal space available with the current combustion chamber. The reduced firing rate would h ave the effect of reducing the necessary heat input below acceptable levels for op erating the dryers. For these reasons LNBs are technically infeasible for the ROEMMC burn er. LNB are considered feasible

for the boiler.

OFA The SolaGen burner already utilizes a LNB design ma king further excess air infeasible to support stable combustion. The ROEMMC does not hav e sufficient space to install OFA ports. In addition to space constraints, suspensio n burners (including the ROEMMC, SolaGen, and boliler) need high air flow through th e 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 t he burner tip. Therefore, OFA is technically infeasible for all three sources.

Low Excess Air (LEA)/FGR LEA is considered to be technically infeasible beca use 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 conditi ons 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 r educing NO

x , one of which being that it reduces the available oxygen since some exh aust gas replaces oxygen rich ambient air (similarly to LEA). As with LEA, some combustio n air must be reduced to accommodate the recirculating flue gas, which may c ause the suspension burner to operate improperly. If combustion air is not reduc ed to maintain proper suspension of fuel through the burner additional combustion chamb er volume would likely be required to accommodate the same heat input while maintainin g 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 tech nically feasible. The following table provides a summary of what controls may be consider ed 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 Rema ining Technology It is important to note that NO

x emissions from wood and bark are low when compared

with fossil fuel NO

x emissions (on the order of 0.1 - 0.35 lb/MBtu expr essed as NO 2 ).

Thermal NO

x generated is less than for fossil fuels due to the low combustion temperatures. Fuel bound nitrogen conversion to NO

x is dependent on conditions including excess air, air staging, heat release rat e, and fuel sizing and moisture content.

Studies have found NO

x to vary inversely with fuel moisture content. Small er fuel particles have been known to generate higher NO

x emissions because of their increased heat release rate (faster burn rate). Fuel NO

x emissions can be significantly reduced by reducing the available oxygen in the early stages o f 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 perha ps higher reductions due to the pretreatment of the exhaust gas to remove PM. 70-9 5% reduction is commonly cited for SCR systems on a wide variety of emission units. Ho wever, the use of western biomass poses several challenges that may reduce the abilit y to control NO

x . Babcock Power is currently the only manufacturer of RSCR systems. Th ey believe that for a unit firing western wood based fuel the probable removal effici ency would be in the range of 70% to 80% (see Babcock Power technical memos). For thi s analysis Roseburg (and their consultant, Golder Associates) assumed that a 75% r eduction 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

NO

x emissions when firing coal, and depending on the d esign 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, NO

x 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 t o 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 NO

x rather than thermal NO

x , and LNB primarilyreduce the generation of thermal NO

x . For the purpose of this analysis we have assumed

that 20% reduction may be achievable. Although we r ecognize that greater reductions may be achieved in practice.

Optimization/Tuning Optimum combustion conditions (including air/fuel r atio adjustments) for reducing

thermal NO

x generation have been identified as an option that can reduce NO

x 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 submitt ed the following information with regard to how they operate and maintain the units.

Operation: All three burner systems employ high quality contro l systems. The boiler and SolaGen systems have the combustion controls embedded in Pr ogrammable Logic Control (PLC) systems. The control drives are VFD variable speed drives for combustion air control

with induced draft fan furnace draft control and wo od 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 controlle rs integrated with a PLC, and high quality electric actuators with feedback.

To ensure that proper operation of the boiler and b urners is maintained at all times, a licensed boiler operator is maintained on site when ever the burners and boiler are operating. Additionally, to the extent possible, R oseburg shuts down peripheral equipment to lighten the load on the boiler. Rosebu rg 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 b urner adjustments, air damper adjustments, and adjustments on fans and motors. Re fractory lining and oxygen sensors are also replaced as necessary. Fan balancing and m otor adjustments are performed annually. If needed, these adjustments are made mor e frequently by Roseburg’s team of on-site technicians and engineers.

In addition to maintenance, regular cleaning is con ducted on the boiler and burners. Every three months the boiler is shut down for clea ning. Every month the ROEMMC is shut down for cleaning. During every shutdown of t he 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/tunin g since Roseburg already follows these practices. Therefore optimization/tu ning 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 NO

x

Potential

Emissions (tpy) NO

x

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. b elieves that systems can be operational within eight months from the time an or der is made. No information was presented by Roseburg Forest Products that would in dicate 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 tha t 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 w ith 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 re quire Roseburg to postpone retrofit until such time as is appropriate. It could be exp ected 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 thr ough a heat exchanger that utilizes plant waste heat, and/or through direct reheat of t he 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 degr ees Fahrenheit and the temperature of

the exhaust of the ROEMMC varies between 700 and 10 50 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 temperatu re 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 ha ve the potential to emit ammonia (as ammonia slip) and generate nitrous oxide (a powerfu l GHG) if not operated optimally. Catalysts must be disposed of, presenting a cost. However ma ny 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 regularit y with which ammonia is handled has reduced the risks associated with its transport, st orage, and use.LNB

LNB would reduce the heat rate that could be sent t o 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 los t 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 i n 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 requir ed to reduce the moisture content of the product.

Factor 4: Remaining Useful Life Roseburg’s 2011 response document indicates that th e useful life of their equipment is as

follows:

Boiler - 10 years

ROEMMC - 10 years SolaGen - 25 years