                                                       

                                       
REVISED TECHNICAL SUPPORT DOCUMENT FOR COKE CALCINERS: SUPPLEMENTAL PROPOSED RULE FOR THE GREENHOUSE GAS REPORTING PROGRAM
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                       
                                                    Office of Air and Radiation
                                           U.S. Environmental Protection Agency
                                                                               
                                                                               
                                                                  April 1, 2023
                                   CONTENTS
                                       
1.  Industry Description	1
2.  Total Emissions	2
3.  Review of Existing Programs and Methodologies	3
3.1  Review of Existing Programs	3
3.2  Calculation Methodologies for Coke Calcining Processes	4
4.  Options for Reporting Threshold	6
5.  Options for Monitoring Methods	7
5.1  CEMS Method	7
5.2  Mass Balance and Combustion Methods	7
6.  QA/QC Requirements	8
7.  Options for Estimating Missing Data	8
8.  References	9





1.  Industry Description  

The coke calciner source category consists of processes that heat petroleum coke to high temperatures in the absence of air or oxygen for the purpose of removing impurities or volatile substances in the petroleum coke feedstock. The coke calciner source category includes, but is not limited to, rotary kilns or rotary hearth furnaces used to calcine petroleum coke.

Calcined petroleum coke is a nearly pure carbon material used primarily to make anodes for the aluminum, steel, and titanium smelting industries. The aluminum industry accounts for nearly 75 percent of the world's calcined coke consumption.  

Table 1 includes a list of the coke calcining facilities based on available information (BP, 2008; company [Oxbow and Rain Industries] websites; and Louisiana Department of Environmental Quality, Electronic Document Management System (https://edms.deq.louisiana.gov/edmsv2/quick-search). There are an estimated 5 operating coke calcining companies in the US with 15 currently operating facilities with 29 coke calcining process units. Most coke calcining facilities are located at or near a petroleum refinery. Oxbow is the largest supplier of calcined petroleum coke in the world, with worldwide production capacity of 2.34 million tons/year and US production capacity of 1.9 million tons/year (Calcining (oxbow.com)). Rain Industries is also a significant producer of calcined petroleum coke, with worldwide production capacity of 2.1 million tons/year and estimated US production capacity of approximately 1.8 million tons/yr. (Carbon | Rain Industries Limited (rain-industries.com)).   
Table 1. US Coke Calcining Facilities.
                                   Facility
                                   Location
                                   Calciner
                            Capacity[†] (tons/yr)
BP Cherry Point - #3
Blaine, WA
1 rotary hearth
                                                                               
BP Cherry Point - #1 & 2
Blaine, WA
2 rotary hearths
                                                                               
Marathon (formerly BP) Wilmington
Carson, CA
1 rotary kiln
                                                                               
RAINCII-Robinson
Robinson, IL 
2 rotary kilns
                                                                        315,000
RAINCII-Lk Charles
Lake Charles, LA
2 rotary kilns
                                                                        350,000
RAINCII (ex-CII CARBON)
Moundsville, WV
2 rotary kilns
                                                                         closed
RAINCII-Norco
Norco, LA
1 rotary kiln
                                                                        400,000
RAINCII-Gramercy
Gramercy, LA
1 rotary kiln
                                                                        400,000
RAINCII-Chalmette
Chalmette, LA
1 rotary kiln
                                                                        400,000
RAINCII-Purvis
Purvis, MS
1 rotary kiln
                                                                               
Seadrift
Port Lavaca, TX
1 rotary kiln
                                                                               
ConocoPhillips-Santa Maria
Santa Maria, CA 
1 rotary kiln
                                                                         closed
ConocoPhillips-Contra Costa 
Rodeo, CA 
2 rotary kilns
                                                                               
ConocoPhillips Lake Charles
Lake Charles, LA
1 rotary kiln
                                                                               
Oxbow-Lemont (formerly Chicago Carbon Company)
Lemont, IL
2 rotary kilns
                                                   Production suspended in 2020
Oxbow-Port Arthur A
Port Arthur, TX
3 rotary kilns
                                                                        700,000
Oxbow-Port Arthur B
Port Arthur, TX
1 rotary kiln
                                                                               
Oxbow-Enid
Enid, OK
3 rotary kilns
                                                                        500,000
Oxbow-Baton Rouge
Baton Rouge, LA
4 rotary kilns
                                                                        700,000
  [†]	Based on company website or Title V air permit.


2.  Total Emissions

Conventional fuels are generally only used during startup to get the calcining kiln (or furnace) up to the desired operating temperature. Once the desired calcining temperature is reached, process gas consisting of volatile organics and sulfur-containing compounds driven from the coke are used as the primary fuel to maintain kiln temperatures (see Figure 1). An afterburner is used to convert excess process gas to carbon dioxide (CO2) and sulfur dioxide (SO2); a waste heat boiler may be used to recover energy from this combustion process. The afterburner off-gas is emitted to the atmosphere and is the primary source of greenhouse gas (GHG) emissions from this process. The primary GHG emissions are CO2 emissions; the afterburner will also likely release trace amounts of methane (CH4) and nitrous oxide (N2O) like other stationary combustion devices. 


Figure 1. Illustration of rotary hearth coke calcining process (from BP, 2008).


Many coke calcining facilities report to the Greenhouse Gas Reporting Program (GHGRP; 40 CFR part 98). Coke calcining process units co-located at petroleum refineries must calculate and report emission from coke calciners following the methodologies specified in GHGRP Subpart Y  -  Petroleum Refineries. Other facilities either do not report or report coke calciner emissions as petroleum coke combustion under GHGRP Subpart C - Stationary Combustion Sources. Based on data reported to the GHGRP for Reporting Year (RY) 2019, the typical coke calcining facility emits 150,000 metric tons (mt) CO2 per year. With 15 operating facilities in the US, it is estimated that these facilities emit 2.2 million mt CO2 per year. As an alternative method to project national coke calcining emissions, it is estimated that coke calcining capacity in the US is about 5-million tons per year. Assuming 10 percent of the petroleum coke fed to the unit is consumed during the coke calcining process, national emissions from coke calciners are estimated to be 1.8 million mt CO2 per year.

Because coke calciners are primarily a CO2 emission source, the coke calciner source category was not significantly impacted by the revisions to the global warming potentials of CH4 and N2O, as discussed in this supplemental proposal. 

3.  Review of Existing Programs and Methodologies

3.1  Review of Existing Programs
In developing GHG monitoring and reporting options for coke calcining process units, several existing programs and guideline methodologies were reviewed.  Specifically, the following resources were examined:

 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Volume 2, Chapter 2. https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/2_Volume2/V2_2_Ch2_Stationary_Combustion.pdf.

 European Union (EU) 2021.  Commission Implementing Regulation (EU) 2018/2066 of 19 December 2018 on the Monitoring and Reporting of Greenhouse Gas Emissions Pursuant to Directive 2003/87/EC of the European Parliament and of the Council and Amending Commission Regulation (EU) No. 601/2012. January. https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02018R2066-20210101&from=EN. 
       
 International Aluminum Institute (IAI) 2006. The Aluminum Sector Greenhouse Gas Protocol. October. https://ghgprotocol.org/sites/default/files/aluminium_1.pdf.

 API (American Petroleum Institute) 2009. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Natural Gas Industry. August. https://www.api.org/~/media/Files/EHS/climate-change/2009_GHG_COMPENDIUM.pdf 

 CARB (California Air Resource Board) 2019. Unofficial Electronic Version of the Regulation for the Mandatory Reporting of Greenhouse Gas Emissions. April. https://ww2.arb.ca.gov/sites/default/files/classic/cc/reporting/ghg-rep/regulation/mrr-2018-unofficial-2019-4-3.pdf

 Environment and Climate Change Canada (ECCC) 2020. Canada's Greenhouse Gas Quantification Requirements. Version 4.0. December. http://publications.gc.ca/collections/collection_2021/eccc/En81-28-2020-eng.pdf.

Each of these sources were reviewed to determine the types of emissions to be reported, the facility reporting thresholds, the calculation methodologies, and the monitoring methodologies recommended. The remainder of this section summarizes the key calculation methodologies. The reporting and monitoring options presented in Section 4 and Section 5 are consistent with the methodologies used in these existing programs and guidelines.

3.2  Calculation Methodologies for Coke Calciners
From the review of existing programs five basic calculation methodologies were identified. The calculation methods are presented in terms of their relative accuracy, from most to least accurate.

  Method 1.	CEMS Method. Measure CO2 concentration and total exhaust gas flow rate using a continuous emission monitoring system (CEMS) and calculate CO2 concentrations from these measured values using Equation C-6 and, if necessary, Equation C-7 of 40 CFR 98.33(a)(4). 
  
  Method 2.	Carbon Balance Method. This is a mass balance method using the carbon content of the green and calcined coke. This method is based on the overall carbon balance approach in IAI (Equation 5, IAI, 2006) and is used in the ECCC requirements for petroleum refineries (Equation 11-22, ECCC, 2020). The equation as presented in ECCC is provided below. This equation is the same as Equation Y-13 of 40 CFR 98.253(g)(2) used for coke calcining process units co-located at petroleum refineries. 
           
  
  
   
  Method 3.	Methane in Green Coke Method. The methane in green coke uses a fixed methane content in the coke of 0.035 mass fraction and uses mass reduction in the quantity of coke fed to the process (corrected for moisture, volatile, and sulfur content) and the quantity of coke leaving the process (corrected for sulfur content). This method is based on the coke calcining approach in IAI (Equation 6, IAI, 2006) and is used in the ECCC requirements for aluminum production (Equation 5-6, ECCC, 2020). The equation as presented in IAI is provided below.  It is expected that coke calcine operators could just as easily determine the carbon content of the green and calcined coke and use the more direct carbon balance method. 
   
  

  Method 4.	Vapor Combustion Method. This method is recommended by API (2009) for coke calcining kilns (Table 2-9), although the method is presented specifically for incinerators, thermal oxidizers, and vapor combustion units (Section 4.7, API, 2009). The method relies on analysis of carbon content of the gas stream inlet to the vapor combustion unit. CO2 emissions are calculated assuming non-CO2 carbon is combusted and converted to CO2 at the efficiency of the combustion system, and assuming 100 percent of the CO2 in the inlet gas stream is emitted. The difficulty with applying this method for coke calciners is collecting representative samples of the process off-gas prior to the afterburner. There may be limited stack length prior to the afterburner and the process gases are very hot in a reducing atmosphere, so sampling between the process and afterburner is dangerous. Additionally, the process gas composition may be variable based on feedstock coke properties and calciner operating conditions, requiring frequent sampling to get representative concentrations. 
  
  Method 5.	Coke Combustion Method. This method is based on the method that some non-refinery facilities report emissions from coke calcining operations under 40 CFR part 98, subpart C. This method can be applied using either the default high heat values and CO2 emission factors in Table C-1 for petroleum coke (Tier 1 or 2) or measured carbon content of the green coke (Tier 3) and attribute the mass reduction of coke as petroleum coke combusted. This method does not correct for the fact that the volatile matter has a lower carbon content than the green petroleum coke and so is likely to produce CO2 emission estimates that are biased high. However, this method is simple and relatively accurate.  
  
4.  Options for Reporting Threshold

Four basic options were evaluated as potential reporting thresholds.  
   
   Option 1.	All facilities with facility-wide GHG emissions exceeding 100,000 mt CO2e must report GHG emissions from coke calciners.
   Option 2.	All facilities with facility-wide GHG emissions exceeding 25,000 mt CO2e must report GHG emissions from coke calciners ("Table A-4" subpart).
   Option 3.	All facilities with facility-wide GHG emissions exceeding 10,000 mt CO2e must report GHG emissions from coke calciners.
   Option 4.	All facilities with coke calcining process units must report their GHG emissions from coke calciners ("all-in" or "Table A-3" subpart).
   
   
Table 2 presents the number of coke calcining facilities and their GHG emissions included for each threshold option. We expect all coke calcining facilities to have combined calcining and combustion emissions exceeding the 25,000 mt CO2e threshold. With the off-ramp provision in 40 CFR 98.2(i), there is limited difference between the threshold options.    

Table 2.  Evaluation of Alternative Threshold Options (considering direct emissions only)
                            Option/Threshold Level
                               Emissions Covered
                              Facilities Covered
                                       
                                 mt CO2e/year
                                    Percent
                                    Number
                                    Percent
                                    100,000
                                   1,970,000
                                     98.5%
                                      14
                                      93%
                                    25,000
                                   2,000,000
                                     100%
                                      15
                                     100%
                                    10,000
                                   2,000,000
                                     100%
                                      15
                                     100%
                             All-in (no threshold)
                                   2,000,000
                                     100%
                                      15
                                     100%


5.  Options for Monitoring Methods 

5.1  CEMS Method 
The CEMS method uses direct measurement CO2 concentration and total exhaust gas flow rate, The CEMS monitoring requirements are outlined in 40 CFR 98.33(a)(4). 

5.2  Mass Balance and Combustion Methods 
All the non-CEMS methods require monitoring of mass quantities of green coke fed to the process, calcined coke leaving the process, and coke dust removed from the process by dust collection systems. 

The mass quantities can be determined using commercial weighing equipment meeting selected accuracy requirements or can simply use company records. Generally, most facilities would follow the Specifications, Tolerances, and Other Technical Requirements For Weighing and Measuring Devices, NIST Handbook 44 (2022). Measurements made following NIST requirements are expected to be more accurate than measurements made not following NIST requirements.

The carbon balance method requires determination of carbon content of the green and calcined coke. The Tier 3 coke combustion method also requires determination of carbon content, but only for the green coke. The carbon content of the green and calcined coke is commonly determined via ultimate analysis of the coke. Suitable methods include:

 ASTM D3176-15 Standard Practice for Ultimate Analysis of Coal and Coke 
 ASTM D5291-16 Standard Test Methods for Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants.
 ASTM D5373-21 Standard Test Methods for Determination of Carbon, Hydrogen, and Nitrogen in Analysis Samples of Coal and Carbon in Analysis Samples of Coal and Coke.

It is expected that ultimate analyses composition will be available from purchase records of green coke and from routine monitoring of feed material and product quality analyses. The carbon content is not likely to vary significantly. These routine measurements are conducted to verify that the impurities levels in the coke are less than those specified for the green coke input or calcined coke product. The rule could specify a measurement frequency (weekly, monthly, quarterly, or annually). Typically, the more measurements conducted, the more accurate the average value will be. The methane in green coke method appears to require at least monthly measurements (although focused on the content of impurities rather than the carbon content) and applies the calculation monthly. The carbon balance method as implemented in subpart Y of the GHGRP only requires that an annual average carbon content be determined. This requirement could be met by a single annual analysis; however, it is expected that the annual average would be determined based on a much greater number of measurements that are routinely determined by the process operator. 

The methane in green coke method requires proximate analysis of the coke to determine moisture, volatile matter, and ash content. This is generally accomplished using:

 ASTM D3172-13(2021): Standard Practice for Proximate Analysis of Coal and Coke. 

The percent sulfur requires additional analysis of sulfur in the ash using one of the following methods.

 ASTM D3174-12 (Reapproved 2018): Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal.  
 ASTM D5016-16: Standard Test Method for Total Sulfur in Coal and Coke Combustion Residues Using a High-Temperature Tube Furnace Combustion Method with Infrared Absorption.
 ASTM D4239-18: Standard Test Method for Sulfur in the Analysis Sample of Coal and Coke Using High-Temperature Tube Furnace Combustion 

As noted previously, the methane in green coke method requires these measurements at least monthly. It is expected that coke calcining process operators may conduct many of these analyses on a routine basis (more frequently than monthly). 

There are a number of gas composition analysis methods available, such as those listed in 40 CFR 98.254(d). However, as noted in Section 3 of this document, collecting representative vapor samples of the coke calciner process off-gas prior to the afterburner is expected to be difficult and unsafe. Therefore, further review of gas compositional methods was not conducted. 

6.  QA/QC Requirements

To ensure the quality of the reported GHG emissions, the following quality assurance/quality control (QA/QC) activities are considered important:
(1)	For coke mass measurements, calibrate the measurement device according to the procedures specified by NIST Handbook 44 or the procedures specified by the manufacturer. Recalibrate either biennially or at the minimum frequency specified by the manufacturer.
(2)	For coke carbon (or impurity) content measurements, follow approved analytical procedures and maintain and calibrate instruments used according to manufacturer's instructions. Document the procedures used to ensure the accuracy of the measurement devices used. 
(3)	All CO2 CEMS and flow rate monitors used for direct measurement of GHG emissions should comply with QA procedures for daily calibration drift checks and quarterly or annual accuracy assessments, such as those provided in Appendix F to Part 60 or similar QA procedures.  
7.  Options for Estimating Missing Data

A complete record of all measured parameters used in the GHG emissions calculations is required (e.g., concentrations and flow rates for the CEMS method and quantities of coke and carbon content values for mass balance or combustion methods). Whenever a quality-assured value of a required parameter is unavailable (e.g., if a CEMS malfunctions during unit operation or if a required fuel sample is not taken), a substitute data value for the missing parameter shall be used in the calculations. 
In general, it is recommended that the average of the data measurements before and after the missing data period be used to calculate the emissions during the missing data period. If, for a particular parameter, no quality-assured data are available prior to the missing data incident, the substitute data value should be the first quality-assured value obtained after the missing data period. Missing data procedures are applicable for CEMS measurements, mass of coke measurements, and carbon content (or coke impurity) measurements. 
 
8.  References 

   2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Volume 2, Chapter 2. https://www.ipcc-nggip.iges.or.jp/public/2006gl/pdf/2_Volume2/V2_2_Ch2_Stationary_Combustion.pdf.
   
   British Petroleum (BP). 2008. NSPS Subpart J Applicability to BP Cherry Point Coke Calciner. Presentation by BP Cherry Point Refinery to US EPA, circa 2008.
   European Union (EU) 2021.  Commission Implementing Regulation (EU) 2018/2066 of 19 December 2018 on the Monitoring and Reporting of Greenhouse Gas Emissions Pursuant to Directive 2003/87/EC of the European Parliament and of the Council and Amending Commission Regulation (EU) No. 601/2012. January. https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02018R2066-20210101&from=EN. 
       
   International Aluminum Institute (IAI) 2006. The Aluminum Sector Greenhouse Gas Protocol. October. https://ghgprotocol.org/sites/default/files/aluminium_1.pdf.

   API (American Petroleum Institute) 2009. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Natural Gas Industry. August. https://www.api.org/~/media/Files/EHS/climate-change/2009_GHG_COMPENDIUM.pdf 

   CARB (California Air Resource Board) 2019. Unofficial Electronic Version of the Regulation for the Mandatory Reporting of Greenhouse Gas Emissions. April. https://ww2.arb.ca.gov/sites/default/files/classic/cc/reporting/ghg-rep/regulation/mrr-2018-unofficial-2019-4-3.pdf

   Environment and Climate Change Canada (ECCC) 2020. Canada's Greenhouse Gas Quantification Requirements. Version 4.0. December. http://publications.gc.ca/collections/collection_2021/eccc/En81-28-2020-eng.pdf.
   
   Butcher T, Harshman R, Konijnenburg J, Lee GD, Williams J, Warfield L, Benham E, Bowers S, and Lippa K (2022) Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. (National Institute of Standards and Technology, Gaithersburg, MD), NIST Handbook (HB) NIST HB 44-2023. https://doi.org/10.6028/NIST.HB.44-2023
   

