Contents:

• Recovery Boiler NO_x Reduction – Jansen Lands Several Upgrades
• Boiler MACT and CISWI Rulings – Another Update
• Changing of the Guard at Jansen
• Update on Biomass Boiler Combustion System Upgrades
• Jansen Technical Papers and Industry Presentations
• New Employees: Roger Lawton and Moriel Arango
• Jansen Projects in Canada
• News Briefs
• Visit Jansen’s Booth at Upcoming Conference Trade Shows
• Receive Our Newsletter by E-mail
• Boiler House Cartoon
• Announcement PSA/Jansen Boiler Workshop in Prague
• Dates & Locations Biomass Boiler Workshops in 2012

Recovery Boiler Capacity Upgrades and NO_x Reduction – Jansen Lands Several Upgrades

Mill conversions to dissolving grade pulp production often necessitate recovery boiler combustion system modifications to increase the boiler’s solids burning capacity while at the same time reducing NO_x emissions. Recently, Jansen was awarded several of these capacity upgrade contracts. 

In recent years, consumer product market trends in the Pulp & Paper Industry are increasingly favoring dissolving pulp grade products. To meet market demand for these products, several mills are in the process of “retooling” the pulping line from producing conventional kraft pulp to dissolving grade pulp. Typically, this change in product leads to increased quantities of black liquor dry solids (BLDS) generated with potentially higher heating values. Because of the higher heat input rate to the recovery furnace and potential increase in fuel nitrogen content, generation of NO_x would be expected to increase, thereby leading to higher stack emission rates.

To improve the recovery boiler’s BLDS throughput capacity and offset potential increases in NO_x, optimization of the existing combustion air delivery system is needed and further staging of combustion air supply can be applied by adding a fourth level of air. In the industry, this fourth level of air is named quaternary air (QA) and has been shown to reduce NO_x emissions. 

At several mills, Jansen was contracted to conduct evaluations of recovery boiler BLDS burning capacity and associated NO_x generation before and after making the change from kraft to dissolving pulp. This evaluation typically consists of a site visit for first-hand collection of operating data, followed by process evaluations and mass and heat balance calculations. An important element of the evaluation process is Computational Fluid Dynamics (CFD) modeling of the furnace combustion conditions with the different BLDS supply rates and heating values. CFD modeling is typically conducted for several configurations of combustion air supply and at the conclusion, a parametric evaluation of key performance factors provides valuable input to the engineering design of the air system modifications. The end result is an air system that best meets the client’s needs.

An example of CFD modeling results is shown in the sketch. The furnace is modeled without QA (on the left), then two different elevations of QA are modeled. A NO_x reduction by 27% is predicted by the models between no QA and QA at a higher elevation (at right).

Jansen has successfully CFD modeled recovery and biomass boiler operation for over 20 years. The modeling is conducted in-house by experienced Jansen personnel, under the direction of Dr. Allan Walsh.  At the annual Recovery Boiler Committee Conference of the American Forest & Paper Association (AF&PA), held in Atlanta this February, Dr. Walsh made a presentation titled “An Improved Method for Modeling NO_x Emissions from Recovery Boilers”. The presentation evaluated several different NO_x modeling mechanisms and their respective complexities in predicting NO_x generation from combustion of black liquor in recovery boilers.

After completing the boiler capacity and NO_x evaluations referenced above, Jansen submitted proposals for the design and supply for the upgrades of the boilers’ combustion air systems. Of these upgrade proposals, projects on two (2) units were recently awarded to Jansen, with proposals for three (3) additional units under review by clients at press time.  The respective planned installation of these upgrades is between March of this year and May of 2013. We will keep you posted on actual upgrade results in later newsletters.  

For general information or specific inquiries, please contact Arie Verloop at 425.952.2825, or John La Fond at 425.952.2832 or by e-mail at firstname.lastname@jansenboiler.com.

Boiler MACT & CISWI Rulings

Another Update

In our previous Newsletter one year ago, we reported that the EPA had issued “final” Boiler MACT and CISWI rulings in March 2011 after a fifteen (15) month extension request was denied by court order. These rulings, however, were not considered final by the EPA due to a number of unresolved issues and the acknowledgement that their formulation had been rushed. The rulings were accompanied by a notice that the EPA intended to reconsider the rules.

The EPA issued a Delay Notice in May 2011 to suspend the effective dates for Boiler MACT and CISWI. An amended set of Boiler MACT and CISWI rules were re-proposed in December 2011 and was opened up for comment with the intent of being finalized in April 2012. Shortly after releasing these amended rulings, a court order vacated the Delay Notice, causing the March 2011 rulings to be put into effect. The EPA then issued a “no action” letter that asserted its “enforcement discretion” to not hold industrial boiler operators to the March 2011 rules. 

Meanwhile, the EPA has continued to review industry comments and available data to yet again revise the rulings for a final time. The “final-final” rulings are expected sometime in April 2012, around press time of this Newsletter issue. Whether these rulings will be accepted by the court or be brought under further challenge through litigation remains to be seen.

The December 2011 re-proposed Boiler MACT rulings included several changes. Some of the more important changes included:

• Work practice standards in place of numerical limits for dioxins/furans.
• The addition of more boiler design and fuel subcategories that cover a wider range of conditions. For example, there is now a stoker boiler subcategory for kiln-dried biomass. 
• Alternative use of a CO CEMS (10-day rolling average) in place of annual stack tests.
• Revisions to some of the emissions limits. For example, CO emissions for existing biomass stoker boilers was raised from 490 ppm, dry @ 3% O₂, to 790 ppm, dry % 3% O₂, when tested annually; although the CO CEMS limit was set lower at 410 ppm, dry @3% O₂.
• PM CEMS is no longer required for biomass units.
• The requirement that an O₂ trim system be in service for CO control when not using a CO CEMS was added.

The CISWI rulings were also re-proposed in December 2011. In addition to limits for filterable PM, CO, Hg, and HCl, like those contained in Boiler MACT, the CISWI rules also have limits for NO_x, SO₂, Cd, Pb, and dioxins/furans. Many biomass boilers are faced with the possibility of being classified as CISWI units because they fire alternative fuels along with biomass (such as OCC rejects or construction/demolish debris that can contain plastics).

Besides the confusion generated by the changing Boiler MACT and CISWI rulings and implementation periods, boiler owners/operators have been challenged to understand their boilers’ emissions profiles and combustion characteristics. JANSEN has been assisting clients with determining how the Boiler MACT and CISWI regulations will impact their operations and provide solutions for units that would exceed the new limits.

How Jansen Can Help?

Jansen assists boiler owners/operators to determine how Boiler MACT (GACT or CISWI) regulations impact their boiler and provide an evaluation of the boiler’s combustion characteristics, including tuning options.  If operational improvements are not sufficient to meet the new emissions requirements, Jansen can provide combustion system upgrades and team with pollution control equipment providers to help comply with the new regulations.

For further information and specific inquiries, please contact John La Fond at 425.952.2832 or Arie Verloop at 425.952.2825 or by e‑mail at firstname.lastname@jansenboiler.com.

Contents:

• Upgrading RDF Boilers – by the 1/2 Dozen
• Boiler MACT Updates – Final Rulings
• Update on Biomass Boiler Combustion System Upgrades
• Jansen Technical Papers and Industry Presentations
• New Employees: Mark LeBel and Andrea Striz
• Jansen Projects in Canada
• News Briefs
• Our Website Has Been Updated
• Jansen at Pacific West Biomass Conference & Expo
• Receive Our Newsletter by E-mail
• Boiler House Cartoon
• Dates & Locations Biomass Boiler Workshops in 2011

Boiler MACT Update – Final Rulings

EPA Posted Final Ruling in February… Now What?

EPA’s efforts to establish Hazardous Air Pollutants (HAPs) emissions limits for industrial, commercial, and institutional boilers and process heaters (referred to as Boiler MACT rules) continues on its long and twisted path.

The EPA first promulgated Boiler MACT rules in 2004 in response to requirements in the 1990 Clean Air Act – and owners of industrial boilers and process heaters worked diligently to comply with the ruling within the allotted three years. However, just before the compliance period culminated in 2007, the US Court of Appeals vacated teh ruling on the basis of complaints that portions of the ruling were not stringent enough, not inclusive enough, and required better definition of fuel classifications. After a lengthy data collection period, the EPA put forth a new, more stringent, ruling in April, 2010. Limits were established for filterable particulate matter (PM), carbon monoxide (CO), hydrochloric acid (HCI), mercury, and dioxins/furans. PM, CO, and HCI emissions were to be used as surrogates for heavy metals, volatile organic compounds, and acid gases, respectively. The ruling was to be finalized in January 2011, following a comment period.

Upgrading RDF Boilers – by the 1/2 Dozen

Recently, Jansen provided mechanical design and supplied equipment for the combustion system upgrade of six RDF boilers in operation at three different E-f-W faciliites in the US.

• RDF Boilers at Facility “A”.  This E-f-W facility on the mid-Atlantic seaboard operates four identical boilers, originally supplied by Combustion Engineering in 1984 to burn RDF and a small amount of stoker coal. Each unit was designed to generate 180,000 lb/hr of steam at 750°F and 700 psig. Over the years, the coal firing capability was removed from the units.

While firing RDF, the units would typically be operated to generate approximately 150,000 lb/hr of steam. At that rate, the boilers experienced difficulties in consistently maintaining CO emissions below the permit level. In order to maintain a 24-hour CO average emission rate below permit level, the boilers would periodically be shut down. In consequence, this lowered the facility’s RDF burning capacity and also increased boiler maintenance costs arising from damage and wear of the boiler equipment due to the frequent shutdowns. The facility’s new owner wished to improve operational performance of the units, particularly by lowering CO emissions, such that sustained boiler operation could be achieved without requiring shutdowns for CO compliance. JANSEN was first contracted in the summer of 2010 to conduct a Phase I engineering evaluation of the units, including CFD modeling, to make an assessment of the overall feasibility of the owner’s goals and develop design concepts on how to proceed.

Based on the study findings, JANSEN recommended that the existing overfire air (OFA) delivery systems be replaced with modern high capacity OFA systems located on the boilers’ side walls and that the fuel distributors be replaced with “new style” RFD distributors at a lower elevation.

The recommended upgrades, along with other improvements and maintenance work, were installed during separate boiler outages between November 2010 and May 2011.

Initial operation of the units that were upgraded first has demonstrated the following results:

• Boiler steam flows can now be maintained in the 150,000 lb/hr range without requiring shutdowns to lower the average CO emissions.
• CO emissions have been reduced by more than 50%.
• NO_x emissions compliance is also being achieved.
• Sustained boiler operation, no longer requiring shutdowns, has significantly increased the facility’s RDF burning capacity.

Based on these four upgrades, the owner has been very pleased with the quality of the design/supply work by Jansen as well as the initial operational performance of the units after the upgrades.

• RDF Boiler at Facility “B”.  Jansen completed a similar project – but with entirely different initial goals – on another RDF boiler in operation in an E-f-W facility in New England. The unit was also supplied by Combustion Engineering (in 1987) for co-firing of RDF and stoker coal and was designed to generate 231,000 lb/hr of steam at 825°F and 880 psig from RDF only. The unit was typically operated below its MCR steam flow to prevent exceeding the daily CO emission limit. Jansen was first contracted to conduct a comprehensive engineering evaluation, including CFD modeling and circulation study, to evaluate the impact of permanently removing the furnace water cooled screen section on the superheater life expectancy since this screen was in need of replacement.   

Furnace CFD modeling by Jansen uncovered shortcomings of the existing OFA system. The model showed non-uniform and elevated flue gas temperatures at the superheater inlet, thereby accelerating corrosion rates in the superheater and emphasizing the need to retain the screen section.  Modeling showed that upgrading the OFA delivery system and removing the screen would result in a decrease in peak corrosion rates by over 10%, as compared to an increase by nearly 10% if the screen section were to be removed without modifying the OFA system.      

The plant moved forward by following Jansen’s recommendations and upgraded OFA delivery system components were installed during the March 2011 boiler outage.

Initial operation of the unit after the OFA system upgrade has been “…a complete success…” as quoted by plant personnel, in part due to the increase in RDF burning rate and decreased CO emission levels. The OFA upgrade also provided in improved combustion control, allowing implementation of a CO trim control loop.

Long term operation will reveal if the predicted benefits on corrosion can be quantified and that removal of the screen section is warranted.      

• RDF Boiler at Facility “C”.  The upgrades on the RDF boilers in facilities “A” and “B” came on the heels of an OFA delivery system upgrade that was supplied by Jansen to a RDF-fueled boiler in the upper mid-west several years ago. This Riley Stoker unit had been converted to burn RDF on a traveling grate in 1989 and has a design steaming capacity of 173,600 lb/hr. Prior to the OFA upgrade, at times, natural gas was co-fired with the RDF to control CO emissions. The purpose of the OFA delivery system upgrade was to lower CO emissions, reduce natural gas co-firing, and have the ability to burn additional RDF and generate more steam.

With the OFA upgrade, all of Jansen’s performance guarantees were met. Operation with the new OFA system and the implementation of an oxygen trim logic has resulted in the following demonstrated performance improvements:

• A 12% average increase in RDF firing and steam generation rates.
• Ability to operate at lower flue gas oxygen levels while maintaining CO and NO_x compliance.
• Reduced frequency and magnitude of CO emission spikes.
• Reduced need for natural gas co-firing to remain within emissions compliance.

For further information on this recent work and specific inquiries about potential future projects, please contact Arie Verloop at 425.952.2825 or by e‑mail at arie.verloop@jansenboiler.com.