Document ID: EPA-HQ-OAR-2019-0373-0080
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2020-09-10T04:00Z

Date:
April 7, 2020
To:
Phil Mulrine, U.S. EPA
From:
Jeff Coburn
Subject:
Meeting Record for April 2, 2020, Teleconference Meeting between Representatives of American Foundry Society (AFS) and Representatives of U.S. Environmental Protection Agency (EPA)

Meeting Attendees:
 Chuck French, U.S. EPA, Office of Air Quality Planning and Standards (OAQPS)
 Phil Mulrine, U.S. EPA/OAQPS
 Kevin McGinn, U.S. EPA/OAQPS
 Jon Averback, U.S. EPA, Office of General Counsel
 Maria Malave, U.S. EPA, Office of Enforcement Compliance
 Jeff Coburn, RTI (contractor for U.S. EPA/OAQPS)
 Jeff Hannapel, The Policy Group (representing AFS)
 Jeet Radia, McWane (representing AFS)
 Craig Schmeisser, Mad River Strategies (representing AFS)
Purpose of Meeting:
      To discuss potential volatile organic hazardous air pollutant (VOHAP) work practice standards for cupolas during startup and shutdown. 
Background:
	On October 9, 2019, the EPA proposed amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for iron and steel foundries (40 CFR part 63 subparts EEEEE and ZZZZZ). On February 12, 2020, the EPA met with representatives of AFS to discuss two unique comments that AFS provided on the proposed rule (see meeting minutes included in Docket ID No. EPA-HQ-OAR-2019-0373). In response to that meeting, AFS provided a description of startup and shutdown (SS) procedures and suggested potential work practice standards for cupola SS (see e-mail from Jeff Hannapel to Phil Mulrine dated March 9, 2020, included in Docket ID No. EPA-HQ-OAR-2019-0373). For convenience, the document provided in the March 9 e-mail is also included as Attachment 1 to this memorandum.   
Discussion:
The EPA began the discussion with reference to the work practice standards recommended by AFS (see Attachment 1). The EPA noted that AFS had included particulate matter (PM) control equipment in the suggested work practice standards; however, the EPA believed the PM emission limit was not an issue and that the numerical PM emission limit could apply at all times, including during SS events. AFS generally agreed with this point and the remaining discussion focused on the VOHAP emission limits and potential work practice standards. 
The AFS walked through the description of the startup and shutdown procedures included with their recommended work practice standards included in Attachment 1 to this memorandum. Key points made during this discussion include:
 During the first several preparatory startup steps, the cupola is open at the bottom and the top. AFS representatives considered that there would be negligible VOHAP from this process. These steps include:
 Refractory repair
 Refractory curing
 Cupola bed preparation, also known as cupola sand bed preparation.
 The next step cupola coke bed preparation, where coke is added to the cupola and the coke bed is lit. Once the coke bed is sufficiently lit, cupola tuyere doors are closed, the cupola vent stack gas collection system fan can be started. AFS representatives did not have data on the VOHAP emissions from this process, but noted that exhaust gas during this phase does not have enough carbon monoxide content for the afterburners to maintain 1,300 °F.
 Once the coke bed is prepared, metallic materials can be added to the cupola, initiating what AFS referred to as the cupola startup phase. 
 Cupola shutdown procedures were only briefly discussed. AFS noted that the key issue during the on blast period of shutdown was too high of temperature in the exhaust gas.
 After the metal from the cupola is tapped, the cupola is cooled. No VOHAP emissions are expected from this phase.

                                 ATTACHMENT 1
                                       
           AFS Description of Startup and Shutdown (SS) Procedures 
                        and Recommended SS Provisions 
                                       

                                       
                         Cupola Operational Procedures
                                       
Below are both a simplification and a generalization of a number of complex and important tasks that are undertaken in preparation of, during, and following cupola operations.  Paramount in these tasks, are the practices and procedures that insure employee safety, prevent equipment damage, and maintain equipment integrity and performance. There will be foundry specific variations in cupola practices and naming conventions identified below.

The document also provides work practice standards from (a) the beginning of startup until normal operations begin and (b) from the beginning of shutdown until banking or bottom drop, where 1300 degree combustion temperature may not be achievable due to operational needs, employee safety concerns and to protect the cupola, ancillary equipment and pollution control equipment.

Cupolas operate over "campaigns" and may be intermittently "banked" between operating shifts, over the weekend or during an operating shift due to equipment breakdowns resulting in reduced metal demand.  As opposed to a "banked cupola", a "cupola bottom drop" would signal the end of a cupola campaign.  Cupola campaign, cupola bottom drop and cupola banking are defined below.

 A cupola campaign is the period from cupola bed installation to cupola bottom drop.  While this period was in the past measured in days, it now is likely more measured in weeks.
 Cupola bottom drop is an event during which the residual contents of the cupola shell are emptied on the floor below the cupola by opening the doors at the bottom of the cupola shell.
 The banking of the cupola means the blast air is turned off and melting is ceased. It occurs during the day when the cupola is not melting or may occur during a weekend in the middle of a campaign when casting production is discontinued.  While blast air is not being introduced into the cupola (i.e. the cupola is off-blast) during cupola banking, banking differs from routine off-blast as metal has been removed from the cupola to the extent feasible.

The above definitions are provided to facilitate the understanding of cupola operations described below and not necessarily intended to be included in the rule text.
Cupola activities can be broken down into Cupola Refractory Repair and Bed Preparation, Cupola Coke Bed Preparation, Cupola Startup, Cupola Operation, Cupola Shutdown and Cupola Banking.  A description of each period is provided below.

    Cupola Refractory Repair and Bed Preparation 
At the end of a campaign and prior to the beginning of the next campaign, the spent cupola bed material (refractory, sand, etc.) is discharged from the bottom of the cupola (known as cupola bottom drop).  The cupola is allowed to cool to ambient temperature.  After cleaning and initial inspection, the cupola bottom doors are closed.  Thorough inspection of the refractory is initiated.  As a result of the inspection and to prepare for the next campaign, refractory is repaired/replaced, and the cupola bottom is installed for the next campaign.  The cupola bottom is predominantly refractory, but may include a mix of sand and clay.  Total material installed is generally in the range of 1 ton to 5 tons, depending on the required repair and cupola size).  During this work, the cupola is usually designated as an OSHA Confined Space Entry with applicable lockout/tagout requirements and may include employee exposure air monitoring prior to employees entering the cupola shell to perform their duties.  

Bed preparation and refractory repair is critical for the safe operation of the cupola.  Without a thorough inspection and proper refractory repair, hot spots and runouts may result in life threatening conditions and additional costs due to production delays.  An improper bed may allow iron to pool at the bottom of the cupola that may result in safety issues during bottom drop.

Once the bed is prepared, the refractory must be cured over a length of time commensurate with the necessary repairs (time is in the range of a few to several hours).  To provide heat for refractory curing, fuel in the form of wood, coke and/or natural gas is used in the cupola.  To start the flame, an ignition source is usually supplied through the tuyeres (nozzles in the side of the cupola through which blast air is introduced into the cupola melting zone during operation).

During this time, tuyeres may remain uncovered and the cupola cap may remain open or partially opened to induce draft or lowered to ensure any precipitation does not extinguish the fire.  In some cases, limited coke additions may be necessary depending on the extent of refractory repairs. 
During Bed Preparation the cupola afterburners (this document refers to afterburners installed in the upper stack of the cupola but some cupolas have a separate combustion chamber where exhaust gases are burned)  may not be in operation  neither may the baghouse or wet scrubber as the concentration of any combustible gases is too low to sustain combustion.  Also, the resulting induced air draft would cool the bed down and require additional wood or coke to cure the refractory.  Given the absence of sufficient combustible gases, afterburners or combustion chambers would not be able to attain anywhere close to 1300 degrees F.

AFS Proposal:
The cupola is being prepared for the startup of operation during which time no emission limits or work practice standards are proposed. 

    Cupola Coke Bed Preparation
After the cupola bottom has been prepared and cured, the next step is to prepare the coke bed.  The coke bed supports the charge material, provides the fuel to produce heat required for melting, and provides a source of carbon for the molten metal.
To start the process several activities occur such as installing the tuyere covers, turning on the cupola water pumps for quenching/cooling and inspecting the cooling water distribution on the shell.

Over a brief interval of time, the blast air is turned on at a gradually increasing rate and the baghouse or wet scrubber airflow is gradually increased at a rate corresponding to the blast air rate.  Also, the afterburner system will be started, and the coke addition is made to initiate the coke bed.  Again, employee safety is paramount during this time requiring reduced air volumes on blast air and the baghouse or wet scrubber fans.

Both the blast air and the baghouse or wet scrubber fans are set at a reduced volume to limit initial air introduced and exhausted from the cupola.  Given there is no metallic charge to hold the coke in place blast air must be limited.  The blast air is also limited in startup to ensure gradual cupola warm up to reduce thermal stress.  Coke bed temperature may be measured to trigger additional coke additions and signal air flow increases of both the blast air and baghouse or wet scrubber air volumes.
An appropriate initial coke height and uniformity of the coke bed is a key factor in achieving desired melt temperature, melt composition, slag flow and subsequent melt rate.  At this point a final measurement of the coke bed is taken and coke is charged to meet the final coke bed height.

AFS Proposal:
Work Practice Standards:  
 Baghouse or wet scrubbers begin operation with increased air flow corresponding to increased combustion air, with operating practices consistent with ensuring safety
 There are insufficient combustion gases to maintain 1300 degrees with the afterburners at maximum capacity.  Afterburners are, therefore, started and increased with corresponding combustion air with operating practices consistent with ensuring safety.
      
    Cupola Startup
Once the appropriate coke bed height has been attained, the charging of the cupola begins with the addition of specially selected metallic charge to insure charge stability and chemistry.  The blast air is either automatically or manually increased to higher values.  Similarly, the cupola APCD air volume may be either automatically or manually increased to correspond to the blast air increases.  Oxygen injection may be turned on at this point and the plug on the tap hole removed.  

AFS Proposal:
The cupola has been started and we propose the following definition.  Cupola Startup begins when  metallics are  first introduced to a cupola that has previously been shutdown or banked and ends when molten metal is first tapped from the cupola.  Work Practice Standards
 Baghouse or wet scrubbers in operation with operating practices consistent with ensuring safety
 Afterburners in operation with operating practices consistent with ensuring safety
      
    Cupola Operation
During cupola operation metal is added with fresh coke and limestone (to act as a flux).  The cupola charge mix may be changed to correct metal chemistry, slag temperature, tapped iron temperatures or adjust for production.  During cupola operation, blast air may be decreased or stopped (off blast) to manage iron production rate versus needs.  APCD fan may be decreased or increased to correspond to the blast air changes.  The applicable emission limits and operating limits are in place.

    Cupola Shutdown (prior to Banking or at Campaign End)
At the end of the campaign or prior to banking, charge materials may be changed, and coke may be reduced or eliminated on last few charges to reduce temperature and associated system wear.  Blast air and oxygen injection may be reduced as needed to minimize gas-take off. 

To prevent damage to the baghouse or wet scrubber, heat exchanger and other equipment, afterburner heat output may be reduced to prevent high inlet temperature at the baghouse or wet scrubber that could result in overheating of the equipment.  Once molten iron flow from the cupola tap hole ceases, a secondary hole may be opened to drain the cupola of remaining iron and slag.  Afterburner/combustion chamber may cease operation at some point in time.   Baghouse or wet scrubber fans will remain on or at reduced air flow until system cools to prevent excessive heat from damaging equipment.  After the cupola is cooled to a safe temperature the baghouse or wet scrubber fan will be shutdown.

If at the end of a campaign, the cupola bottom doors will be opened and the residual contents of the cupola shell are dropped on the floor (i.e., bottom drop).  

AFS Proposal:
The cupola has been shut down and we propose the following definition. Cupola Shutdown begins when the final charge addition is made and ends when molten metal ceases to flow from the cupola tap hole preceding either cupola banking or cupola bottom drop. 

Work Practice Standards:  
 Baghouse or wet scrubber in operation with operating practices consistent with ensuring safety and preventing production and pollution control equipment damage or overheating.
 Afterburners operated as needed to comply with the 1300 degrees operating limit to the extent feasible without causing production or pollution control equipment damage or overheating.

      
    Cupola Banking
Once charging of metallics has stopped, the metallics are melted out to the extent feasible, slag holes are drained as much as possible, then the tap and slag holes are plugged, and some necessary repairs may be completed.  
Tuyere covers may be left open to sustain slow combustion of remaining coke.  If the cupola holdover is several days or weeks additional coke may be added.

AFS Proposal:
The cupola is gradually cooled with operating practices consistent with ensuring safety.

   Summary of Emission Standards and Work Practices for Startup and Shutdown
                                       
Provided below is a summary of the proposed applicable emissions standards and work practices that would apply during the process of starting and shutting down a cupola furnace.  These are based on the detailed description above of the processes and procedures for a typical cupola and the rationale for those processes and procedures for purposes of identifying NESHAP requirements for the startup and shutdown of a cupola furnace for iron and steel foundry major sources. 

1) Cupola Refractory Repair and Bed Preparation
 The cupola is being prepared for the startup of operation during which times no work practices are proposed

2) Cupola Coke Bed Preparation
Work Practice Standards
 Baghouse or wet scrubber begins operation with increased air flow corresponding to increased blast air, and operating practices consistent with ensuring safety
 There are insufficient combustion gases to maintain 1300 degrees with the afterburners at maximum capacity.  Afterburners are, therefore, started and increased with corresponding blast air with operating practices consistent with ensuring safety

3) Cupola Startup
Work Practice Standards
 Baghouse or wet scrubbers in operation with operating practices consistent with ensuring safety
 Afterburners in operation with operating practices consistent with ensuring safety

4) Cupola Operation
 The applicable emission limits and operating limits are in place

5) Cupola Shutdown
Work Practice Standards
 Baghouse or wet scrubbers in operation with operating practices consistent with ensuring safety and preventing production and pollution control equipment damage or overheating
 Afterburners operated as needed to comply with the 1300 degrees operating limit  to the extent feasible without causing production or pollution control equipment damage or overheating

6) Cupola Banking
 The cupola is gradually cooled with operating practices consistent with ensuring safety