Boiler MACT and Strategic Air Permitting


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Mark Wenclawiak of All4 Inc. presents "Boiler MACT and Strategic Air Permitting" at the A&WMA Southern Section annual meeting. This presentation provides insight into the boiler MACT, NSR reform rules, and how operation can be optimized to reduce operating and compliance costs. The presentation also includes a case study on a pulp mill.

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  • Thank you for the introduction and the opportunity to explore the topic of using Boiler MACT as one means for strategic NSR permitting. In this presentation we’ll give an overview of how a regulatory driver such as Boiler MACT can be used as a tool in combination with NSR permitting as a means to increase operational and permitting flexibility while decreasing actual emissions and reducing operating and compliance costs. Timing will be a critical component as part of the permitting. Can projects be implemented outside of outages? Does the permitting agency have the ability to process the application in time for boiler mact compliance? We’ll use an illustrative case study loosely based on an actual ALL4 project that involved an unnamed kraft mill that wanted to increase its pulp production and black liquor solids firing rate and was able to take advantage of a capital project to convert a multi fuel boiler (primarily coal) to a natural gas boiler with limited coal usage. Not only does this project enable the mill to increase production without triggering PSD but it also allows the mill to reduce its compliance obligations under boiler mact by changing the applicable subcategory of its boiler. First lets review some of the key drivers and tools this strategic air permitting approach.
  • A typical boiler mact permitting project will begin with establishing the boiler’s subcategory. Now that the initial notification submittals are out of the way, it is likely that we know the appropriate subcategory for our boilers. However, as a refresher, remember that the subcategory is established based on the fuels combusted and the design type of the unit (such as a stoker or fluidized bed); the unit’s design heat input capacity (based on the name plate), and the calculated annual heat input using the fuel consumed in the 12 months before a compliance demonstration). Once the subcategory is established, the applicable emission limits can be identified, from which you can evaluate how you will comply with the limits (install APC; using the total selected metals options, emissions averaging, output based standards, etc.). This early step will likely require some form of engineering testing as part of your planning – we’ll also come back to this topic on the next slide. You can then explore the types of capital projects that are worthy of consideration such as derating your boiler below 10 MMBtu/hr to avoid emission limits, or retiring units altogether. Our project took another option, which was accepting a limitation on fuel usage to change the boiler’s subcategory and generate actual emission decreases, which is where our integration with NSR comes into play.
  • The NSR reform rules allow some creative emissions accounting, particularly for existing emission units. The project begins with identifying the modified units (those that are physically modified as a part of the project) and the affected units (those that are impacted by the project through an increase in utilization). For projects involving a power boiler or other steam generating sources, the modified and affected units include boilers, the woodyard, and fuel handling equipment. Debottlenecking of upstream or downstream units, particularly as it relates to an increase in steam and allowing more production are all part of the equation. Remember our mention of engineering testing on the previous slide. Well the NSR reform baseline actual to project actual applicability test provides the potentialopportunity to re-establish baseline emissions using the results of that engineering testing for Boiler mact compliance. This is particularly useful when historical emissions were estimated on emission factors that were not representative of actual emissions, especially when the emission factors were lower that stack testing results. (Could go other way as well!)
  • Remembering that your project will involve your boiler, and that you are aiming to substantially increase production ratessuch that your project emissions are significant with respect to PSD, the boiler mact compliance project can provide the contemporaneous decreases that will allow you to net out of PSD. We’ll explore this more as part of our case study. But at this point you can explore multiple scenarios to maximize operational and permitting flexibility based on fuel mixes or production materials. And remember, the NSR reform rules allow the consideration of excludable emissions, which are often based on the historical peak monthly production levels that occurred during the baseline period. We had timing on our opening slide. A reminder here is in order because of time constraints related to outage schedules, permit preparation and agency processing time, and the capital procurement process for items like air pollution control devices. The flexibility with new units is a bit more limited because emissions are based on potential to emit. However, all is not lost because as part of the project you can consider air pollution control devices, and fuel or production limitations to reduce the PTE.
  • Boiler mact compliance projects such as the one we will describe next, can generate contemporaneous decreases that can allow facilities to avoid PSD . In particular, previously retired units, shutting down currently active but perhaps aging units, or changing the operating mode of a unit such as designated it as a backup boiler or limiting the amount and types of fuels used. As a note, the use of actual emission reductions generated by a MACT compliance project for NSR netting purposes is supported by U.S. EPA guidance. As part of the NSR reform permitting process, remember additional requirements that may be applicable as part of the project such as source obligation tracking for pollutants in which the net emission increase is at least 50% of the significance thresholds, as well as other regulations that may be triggered such as NSPS. Lastly, as with any projects nowadays, consider the impact to your facility’s naaqs compliance (and if you don’t know the status of your naaqs compliance, there is no time like the present to find out). With this theory behind us, let’s get into the case study ……
  • Our case study is based on an existingunbleached kraft pulp mill. The project consisted of debottlenecking and increasing pulp production by modifying the Recovery furnace in order to increasethe BLS firing rate. In addition to the modified recovery furnaces, the affected sources in the project consisted of the woodyard, the recovery area, pulping system, washing and paper machines. Since the project was associated with existing emission units, the NSR reform rules allow the baseline actual to projected actual emissions to estimate the project emissions increases. (Note that causticizing area and lime kiln were unaffected due to historic operations.)The project also included the conversion of a combination boiler to a natural gas power boiler. The mill considered various scenarios of coal firing for a backup fuel and ultimately elected to accept an annual capacity factor limitation as part of the permitting strategy. This conversion project, as we will see, was the key to the viability of the production increase since it served as a contemporaneous decrease in the PSD emissions inventory process. Let’s get into some of the specifics of the boiler conversion project.
  • The current combination boiler burns coal, wood, natural gas and fuel oil. As we relate back to our discussion on boiler mact and identifying your subcategory, this unit was an existing source in the coal/solid fossil fuel subcategory (based on fuel type) and stoker subcategory based on design type.Through the acceptance of an annual capacity factor on coal to less then 10%, the boiler was able to be re-categorized to a gas 2 unit. For boiler mact purposes, what is the difference? Let’s look at the emission limits to compare…..
  • Here we have a comparison of the boiler mact emission limits, and we see that the emission limits outside of CO, are higher (less restrictive) for the gas 2 subcategory. The co emission limit is slightly lower for the gas 2 subcategory. Performance testing would be required for HCl, Hg, and PM while firing coal, and for CO while firing gasFuel sampling requirements would be limited to the coal firing scenarioLets take a look at the emissions inventory and how the mill benefited from the NSR reform rules
  • Since our project consisted of existing units, we established baseline actual emissions using a consecutive 24-month period for each pollutant during a 10-year look back period. Because the historical use for this boiler was based on coal and bark, the baseline actual emissions were relatively higher than the projected actual emissions when firing predominantly or exclusively natural gas. Speaking of projected actual emissions, the mill considered scenarios in which coal usage was restricted, and bark and fuel oil were discontinued. Future production levels at the mill are directly related to it projected coal usage – in other words, the maximum amount of BLS that was proposed as an overall future mill production limit was based on the scenario with the maximum amount of natural gas firing. The mill wanted to maintain a backup fuel in some capacity so ultimately the mill accepted a coal limitation such that the annual capacity factor remains below 10%. As we mentioned previously, the nsr reform rules include the concept of excludable emissions. For our situation, we did not consider excludable emissions to conservatively estimate projected actual emissions.
  • The resulting emissions inventory for the project showed significant increases for VOC, NOX, pm, PM10, and PM2.5. Since the project related increases were significant for these pollutants, the netting provisions of PSD applicability were triggered to evaluate if a significant net emissions increase would occur. This second step invokes the consideration of contemporaneous (those within the past 5 years) increases and decreases. The boiler conversion project served as the contemporaneous decrease for the inventory, resulting in emissions after netting for all pollutants that were less than the baseline actual emissions (except for VOC, which had net emissions that exceeded baseline emissions but importantly, were less than the 40 tpy significance threshold for PSD). Therefore, PSD was avoided for this project that ultimately increased production at the Mill. Caution again with contemporaneous projects that used actual to projected actual.
  • In summary, the mill was able to achieve an approximately 15% increase in its BLS firing rate and a greater than 25% increase in pulp production all while using boiler mact and the nsr reform rules to its advantage. The mill was able to avoid PSD and will be able to simplify its boiler mact obligations (higher emissions limits, no need for add on controls, less complicated testing and fuel sampling)
  • Boiler MACT and Strategic Air Permitting

    1. 1. Boiler MACT and Strategic Air Permitting Presented to A&WMA Southern Section Annual Meeting and Technical Conference by All4 Inc. Mark Wenclawiak | | 678-460-0324 July 10, 2013 Kimberton, PA | 610.933.5246 Kennesaw, GA | 678.460.0324
    2. 2. Outline  Drivers and tools • Boiler MACT • NSR Reform rules • Improve operational flexibility while decreasing actual emissions • Reduce operating and compliance costs • Timing: Outages? Agency processing? Procurement?  2 Case study • Existing Kraft mill – increase pulp production, BLS rate • Boiler conversion – multi-fuel to gas, limited coal • PSD avoidance; reduced Boiler MACT obligations Your environmental compliance is clearly our business.
    3. 3. Boiler MACT and Strategic Air Permitting Drivers and Tools
    4. 4. Drivers and Tools – Boiler MACT  Typical Boiler MACT project begins with: • • • •  Establishing your subcategory (initial notification) Fuels combusted and design type Design heat input capacity Annual heat input basis 12-months prior to compliance event Identify applicable emission limits • Install APC; TSM option; output based standards • Engineering testing for compliance strategy   Derating < 10 MMBtu/hr or retiring units Change fuel mix or introduce new fuels (e.g., TDF) • Our project: Accept limitation on fuel usage to switch subcategory, and generate actual emission decreases 4 Your environmental compliance is clearly our business.
    5. 5. Drivers and Tools – NSR Reform  NSR reform allows creative accounting, particularly for existing emission units • Identify modified and affected units    Projects with boilers: Boilers; Woodyard; Fuel handling equipment Debottlenecking….More steam = more production? Baseline actual to projected actual test • Testing: Opportunity to re-establish baselines based on engineering testing for Boiler MACT compliance or other updated data • Historical factors < testing results = good thing 5 Your environmental compliance is clearly our business.
    6. 6. Drivers and Tools – NSR Reform   If production increase project exceeds PSD significance, Boiler MACT project can provide contemporaneous decreases to net out of PSD (case study) Projected actual emissions • Consider multiple scenarios to maximum flexibility  Changes to types and rates of fuels and/or production materials • Excludable emissions – historical peak monthly levels during baseline • Remember timing: consider outage schedules, permit preparation and processing time, capital procurement process  6 New units more limited: based on potential to emit (PTE) • Consider air pollution control devices and fuel or production Your environmental compliance is clearly our business.
    7. 7. Drivers and Tools – NSR Reform  Boiler MACT projects & contemporaneous decreases • • • •     7 Retired (past) units Shutdown currently permitted units Limited use units (e.g., change to a backup boiler) Be careful with contemporaneous PSD avoidance projects! Actual reductions to comply with MACT considered surplus for NSR netting and can be used (U.S. EPA memo) Source obligation tracking Are additional regulations triggered (e.g., NSPS)? Don’t forget about NAAQS considerations Your environmental compliance is clearly our business.
    8. 8. Boiler MACT and Strategic Air Permitting Case Study
    9. 9. Case Study  Existing unbleached Kraft pulp mill • Project to increase pulp production and BLS firing rate     Existing recovery furnace physically modified Affected sources: Recovery Area; Pulping System; Washing; Paper Machines; Woodyard Causticizing & kiln unaffected due to historical operations Baseline actual to projected actual emissions • Convert combination boiler to natural gas power boiler    9 Consider various scenarios of coal firing for backup fuel Annual capacity factor limitation Key to viability: contemporaneous decrease Your environmental compliance is clearly our business.
    10. 10. Case Study  Current combination boiler • Coal, wood, natural gas, fuel oil • Existing source with respect to Boiler MACT   Coal/solid fossil fuel, stoker subcategories Natural gas conversion project • Natural gas and coal only  Coal limited to annual capacity factor <10% • Reclassified as Gas 2 (other) unit subcategory  10 Comparison of Boiler MACT emission limits Your environmental compliance is clearly our business.
    11. 11. Case Study  Boiler MACT emission limits comparison Pollutant 1.7E-03 lb/MMBtu 5.7E-06 lb/MMBtu 7.9E-06 lb/MMBtu PM 4.0E-02 lb/MMBtu 6.7E-03 lb/MMBtu CO 11 2.2E-02 lb/MMBtu Hg  Gas 2 Subcategory HCl  Coal Subcategory 160 ppmvd @ 3% O2 130 ppmvd @ 3% O2 Testing for HCl, Hg, PM (coal); CO (gas) Fuel sampling limited to 100% coal firing scenario Your environmental compliance is clearly our business.
    12. 12. Case Study  Existing emission units so….baseline actual emissions • NSR Reform     Consecutive 24-month period in 10-year look back Average annual rate for the 24-month period Influenced by use of non-natural gas fuels Projected actual emissions • Based on reduced coal usage and elimination of fuel oil and wood waste in boiler • Mill production levels based on maximum BLS firing with the maximum amount of natural gas firing • Maintain some backup fuel capacity with coal • Excludable emissions not considered to conservatively estimate projected actual emissions 12 Your environmental compliance is clearly our business.
    13. 13. Case Study   Project related increases significant for VOC, NOX, PM, PM10, and PM2.5 Netting of contemporaneous projects • Decreases consisted of reductions attributable to boiler coal limitation • Decreases for all pollutants except VOC after netting (though VOC net increase not significant) • PSD avoided 13 Your environmental compliance is clearly our business.
    14. 14. Boiler MACT and Strategic Air Permitting Conclusions
    15. 15. Conclusions  Increase in production achieved • ~15% increase in BLS firing rate over current limit • ~25% increase in pulp production over current limit   PSD avoidance Simpler Boiler MACT obligations • No need for add-on control • Less complicated testing and fuel sampling requirements 15 Your environmental compliance is clearly our business.
    16. 16. Questions and Open Discussions Mark Wenclawiak, CCM | | 678-460-0324 Kimberton, PA | 610.933.5246 Kennesaw, GA | 678.460.0324