Freeport-McMoRan Copper & Gold Inc. (FCX) Engineering Report

Miami Smelter Expansion Project Engineering Management

H377000 Extended Roofline SO2 Emissions Summary

H377000-0000-07-124-0001, Rev. 0, 

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Ver: 04.00

© Hatch 2014 All rights reserved, including all rights relating to the use of this document or its contents.

Table of Contents

1. Introduction........................................................................................................................................... 1

2. Summary and Conclusions ................................................................................................................. 1

3. Extended Roofline Study (ERS) Assessment Methodology ............................................................ 2

3.1 Sampling Locations and Areas ..................................................................................................... 2

3.2 Sampling Period............................................................................................................................ 7

3.3 Data Filters.................................................................................................................................... 7

3.4 Isa 2 Temperature Approximation ................................................................................................ 8

3.5 Gas Flow Rate .............................................................................................................................. 9

3.5.1 Anode Aisle Flow Approximation..................................................................................... 9

3.6 Throughput Adjustments – Annualized Emissions ..................................................................... 10

3.7 Weighting Factor for Unequal SO2 Concentration from Each Sample Point.............................. 11

3.7.1 Simplified vs. Concentration Weighted Approach ......................................................... 12

4. Results................................................................................................................................................. 13

4.1 SO2 Concentration ...................................................................................................................... 13

4.2 Hourly vs. Minute SO2 Data........................................................................................................ 14

4.3 Mass Emissions .......................................................................................................................... 14

List of Tables

Table 2-1: Comparison of the 2013 ERS and June 2012 SO2 Gas Sampling Campaigns .......................... 2

Table 3-1: Key Dimensions for 2013 Extended Roofline Study (ERS)......................................................... 3

Table 3-2: Sampling Period........................................................................................................................... 7

Table 3-3: Plant SO2 Emissions and Throughput during 2013 Extended Roofline Study (ERS) ...............11

Table 3-4: Annual Plant Throughput Basis ................................................................................................. 11

Table 3-5: Simplified vs. Concentration Weighted SO2 Emissions Calculation Results.............................13

Table 4-1: SO2 Concentrations from Extended Roofline Campaign...........................................................13

Table 4-2: Comparison Between Minute-by-Minute and Hourly SO2 Data.................................................14

List of Figures

Figure 3-1: Gas Sampling Locations, Converter Aisle.................................................................................. 4

Figure 3-2: Gas Sampling Locations, Anode Aisle ....................................................................................... 4

Figure 3-3: Gas Sampling Locations, IsasmeltTM Building............................................................................ 5

Figure 3-4: Gas Sampling Locations, Electric Furnace Building................................................................... 6

Figure 3-5: Monthly Average Temperature Rise for the Isa 2 Monitoring Location ...................................... 8

Figure 3-6: Monitor Mounted Wind Speed Impeller ...................................................................................... 9

Figure 3-7: Monthly Trends in Building Flow Rates .................................................................................... 10
Freeport-McMoRan Copper & Gold Inc. (FCX) Engineering Report

Miami Smelter Expansion Project Engineering Management

H377000 Extended Roofline SO2 Emissions Summary

H377000-0000-07-124-0001, Rev. 0, 

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© Hatch 2014/03 

1. Introduction

Freeport-McMoRan Copper & Gold Inc. (FCX) is undertaking a project at their Miami copper 

smelter in Arizona to increase production capacity and to ensure the smelter’s operation does 

not cause or contribute to a violation of the new National Ambient Air Quality Standard 

(NAAQS) for Sulfur Dioxide of 75 ppbv (1-h).

The Feasibility Study SO2 mitigation scope and current permit application are based on a 

3-4 day sampling campaign completed in June 2012. Results from the June 2012 Roofline 

Sampling Campaign methodology were summarized in detail in the Feasibility Study Report: 

H341001-0000-07-124-0003 (Rev. 0) Building Scrubber Sizing Study. To mitigate compliance 

and capital cost risks associated with the June 2012 roofline sampling campaign, the 

extended roofline sampling (ERS) campaign was initiated by FCX in late 2012 to provide 

more representative, long term roofline SO2 emission estimates for current operation. Gas 

flow measurements for most smelter buildings started in mid March 2013; mass emissions 

estimated for the ERS campaign in this report correspond to a period of roughly 9 months. 

This represents almost 100 times more data than the June 2012 campaign.

This report summarizes the annualized SO2 mass emissions and calculation approach for the 

current Miami smelter operation based on results obtained from the ERS campaign up to 

December 31, 2013. The annualized SO2 emissions representing current operation are 

compared to the results based on the June 2012 sampling campaign, which was used to 

establish the Feasibility Study SO2 mitigation scope. 

2. Summary and Conclusions 

Annualized SO2 emissions representing a current normalized throughput equivalent to 

roughly 689,000 dstpy of new metal bearing materials (NMBM) are summarized for the ERS 

campaign in Table 2-1. The ERS campaign involved sampling SO2, temperature and velocity 

from the following four smelter buildings; Anode Aisle (AA), Converter Aisle (CA), Isasmelt 

Building (Isa) and Electric Furnace Building (ELF). These emissions are compared directly 

with the annualized results obtained based on the June 2012 sample campaign, which were 

used to establish the Feasibility Study SO2 mitigation scope.

The results indicate generally good alignment of annualized emissions estimated based on 

the ERS campaign compared with results from June 2012. Total annualized SO2 emissions 

are lower by approximately 20%. Annualized emissions are substantially lower than June 

2012 for the Isa building (55% lower) and CA (20% lower). ELF building emissions are 

roughly 50% higher, and AA emissions are approximately 20% higher. The increase in AA 

emissions is attributed primarily to a revision in the measured roof monitor width from 4.0 ft to 

4.5 ft. The results for the other smelter buildings are consistent with SO2 concentration (only) 

data obtained from the full ERS period to date, covering a larger data period spanning almost 

13 months from December 2012 through December 2013.
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Table 2-1: Comparison of the 2013 ERS and June 2012 SO2 Gas Sampling Campaigns 

Area

Total Annualized Emissions

stpa

June 2012 Sampling 

Campaign

2013 Extended 

Roofline Campaign

Anode Aisle (AA) 160 193

Converter Aisle (CA) 425 343

Isasmelt Building (Isa) 239 106

Electric Furnace Building (ELF) 35 53

Total 859 695

The impact on expected plant emissions and the corresponding SO2 GLC for the future 

operation with the proposed mitigation scope in place is expected to be a minor reduction. An 

appropriate design factor will be included to account for sampling variability and unmeasured 

emissions from other building openings (e.g., 20% was used in the Feasibility Study).

Sampling methodologies are detailed in the report. Changes from the June 2012 sampling 

methodology are highlighted. These are generally minor.

A simplified calculation approach based on average combined SO2 concentration for each 

building was found to give similar results to a more complex approach in which the SO2

concentration from each individual sample point was estimated based on temperature relative 

to ambient. The results above are based on this simplified calculation approach, which will 

prove easier to implement automatically in the FCX Miami control system. 

3. Extended Roofline Study (ERS) Assessment Methodology

The sampling procedure for the 2013 ERS was carried out in generally the same fashion as 

the June 2012 campaign. FCX has been responsible for setting up and running the ERS 

campaign. The following sections will expand upon and identify deviations from the June 

2012 methodology. 

3.1 Sampling Locations and Areas

Figure 3-1 to Figure 3-4 illustrates the smelter building gas sampling locations, with indication 

of proximity to major process vessels. No adjustment was made in this report to account for 

unmeasured fugitive emissions. Table 3-1 and the corresponding calculations for the 2013 

ERS reflect the latest data, including several updated roof monitor dimensions. All roof 

monitors are assumed to extend the full length of each building. The width reflects the bottom

of the roof monitor opening, which is located at approximately the same location where the 

gas velocity is measured.
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Table 3-1: Key Dimensions for 2013 Extended Roofline Study (ERS)

Sample Point Length

(ft)

Width

(ft)

Height

(ft) Notes

Converter Aisle (CA)

CA 2 165 8 - Column line 20 to 26

CA 3 55 8 - Column line 26 to 28

CA 4 55 8 - Column line 28 to 30

CA 5 (high bay) 55 4.5 - Column line 30 to 32. 4.5 

ft wide roof monitor (vs. 8 

ft opening) added after 

June 2012 sampling.

Anode Aisle (AA)

AA 1 149 4.5 - AA Column Line 11 to 

AA Column Line 18

AA 2 84 4.5 - AA Column Line 7.5 to 

AA Column Line 11

AA 3 (Mold Barrel) 154 4.5 - CA Column Line 32 to 

AA Column Line 7.5

Isasmelt Building (Isa)

Isa 1 (crane bay) 45 - 8.6 -

Isa 2 (roof monitor) 53.7 1.7 - -

Isa 3 (WHB opening) 33.2 - 25.4 Assumed 10% reduction in 

area for WHB, platforms, etc.

Electric Furnace Building (ELF)

ELF 1 (long monitor) 54 8 -

ELF 2 (short monitor) 13.3 8 -

NOTE: Bold highlighted values have been updated since June 2012 sampling.

A few updates relative to the June 2012 sampling campaign are highlighted below:

• There was no AA Crane Bay sampling location since the June 2012 sampling confirmed 

this to be a negligible SO2 emission source.

• The ELF building had two total sample locations (one in the long monitor), as opposed to 

three total (two in the long monitor) in the 2012 campaign. 

• Elimination of one AA measurement location and relocation of several sampling locations 

in the CA, with the updated locations shown in Figure 3-1 and Figure 3-2. FCX is now 

measuring in the “hot spots” above each converter vessel, which could increase the 

measured SO2 concentrations and gas flows relative to the “average” locations 

established in June 2012. This is considered conservative.

• Thermocouples were located at each SO2 sample location. An assessment with the June 

2012 results confirmed negligible corrections to the estimated SO2 emissions with 

additional thermocouples mounted between sample locations. 

• There are no velocity measurements available for the AA since the high peak gas 

temperatures (well above 200°F) reportedly melted the plastic anemometer impellers 

shortly after installation. See Section 3.5.1.
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Figure 3-1: Gas Sampling Locations, Converter Aisle

Figure 3-2: Gas Sampling Locations, Anode Aisle
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Figure 3-3: Gas Sampling Locations, IsasmeltTM Building 
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Figure 3-4: Gas Sampling Locations, Electric Furnace Building 
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3.2 Sampling Period

SO2 concentrations were taken on a minute-by-minute basis starting in December 2012 and 

continued until December 2013. However, hourly average data was only available for gas 

flow (velocity) and temperature, along with SO2, beginning part way through March until 

December 31, 2013, reporting direct to the plant control system. Both flow and concentration 

are required to calculate mass emissions (e.g. stpa or lb/h SO2). In general, calculations were 

applied to the data obtained from April 1, 2013 through December 31, 2013. Refer to Table 

3-2 and the text below.

Table 3-2: Sampling Period

Building Period

Total 

Production 

Days

Valid 

Sampling 

Days*

Notes

CA Apr. 1 to Dec. 31, 2013 235 234 Excludes Oct. 10 to Nov. 19.

AA Apr. 1 to Dec. 31, 2013 275 256

Isa Apr. 1 to Dec. 31, 2013 275 256

ELF May 1 to Dec. 31, 2013 245 245 No flow data until May.

*Note: This reflects removal of invalid data points, see Section 3.3.

Data obtained during March was excluded for all buildings. This was the first (partial) month 

for which flows were measured. It took some time to get the sampling program up and 

running smoothly. 

For the ELF, data for April was excluded as well. No velocity data was available for this 

building during March and April. 

October 10th – November 19th (inclusive) was excluded from all Converter Aisle calculations. 

Several probes were moved during this period to a location directly over Converter #2 in 

order to assess performance of the new mouth cover. Towards the end of this period the

probes were returned to their original locations. 

There were also missing temperature measurements for the Isa roof line monitoring location 

for a portion of the period. See Section 3.4.

3.3 Data Filters

The methodology for treating negative SO2 concentration readings from the monitors is to 

round them up to zero, as they are assumed to be drift errors or noise. This treatment method 

is modestly more conservative than what was used in 2012, where negative concentrations 

(typically small negative values) were used directly in calculations. 

Over the extended campaign in particular, there were ranges of “invalid” sampling data that 

were filtered from the data set, as follows:

• Any data obtained during the calibration periods was eliminated from the averaging 

period (identified by the value “6999.0” in the concentration field or manually input as 

“CAL” by FCX).
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• Any data reporting orders of magnitude lower or higher flow than the remainder of the 

data set was eliminated from the averaging period. Flow changes from the roof monitors 

are typically modest.

• Any data specifically labeled by FCX or the data acquisition system as “No Data” or “No 

Good Data for Calculation” was eliminated from the averaging period.

3.4 Isa 2 Temperature Approximation

The missing temperatures for the Isa 2 location during April and May were calculated by 

assuming that the temperature rise, compared to ambient temperature, is equal to the 

average temperature rise during July-December 2013, 28.4°F, see Figure 3-5. June 2013 

was excluded from the averaging period since it was deemed non-representative due to the 

plant shutdown. This average temperature rise is consistent with the temperature rise of 27°F 

reported in the 2012 sampling campaign. The impact of temperature on estimated SO2 mass 

emissions is minor; a 5°F change in temperature impacts the mass emissions by roughly 1%. 

Figure 3-5: Monthly Average Temperature Rise for the Isa 2 Monitoring Location
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3.5 Gas Flow Rate

Actual ventilation gas velocity from the smelter buildings was estimated using a wind speed 

impeller at each sample location (as shown in Figure 3-6). The velocity for each building 

opening or section of the converter/anode aisle was multiplied by the corresponding area 

(Table 3-1), then converted to scfm using the measured temperature. The total flow per 

building (in scfm) was calculated as the total flow from all openings (2-4, depending on the 

smelter building). For the converter and anode aisle this represents a more detailed approach 

than June 2012, where average velocities calculated from 3-4 sample locations were 

multiplied by the total roof monitor open area. Unlike the June 2012 campaign, this 

modification was required for the 2013 ERS campaign in order to accurately weight the total 

flow contribution from significantly different roof monitor open areas, notably the different 

length between sample locations along the aisle. 

It has been assumed that all vertical gas velocity measurements apply to each section over 

the applicable area (length x width) of the monitor. For horizontal ventilation windows (Isa 

building only), a velocity profile was taken in June 2012 over the accessible area using a 

hand held wind speed impeller in order to correct the velocity readings. The same 62% 

correction is assumed to apply for the ERS campaign, accounting for the Isa east/WHB 

window (Isa 3) geometry and flow distribution. Per June 2012, no correction was applied to 

the Isa crane bay window (Isa 1) – this location is much closer to the centerline elevation.

Figure 3-6: Monitor Mounted Wind Speed Impeller

3.5.1 Anode Aisle Flow Approximation

There are no Anode Aisle (AA) velocity measurements available for the ERS campaign. One 

approach would be to assume the same fixed flow measured during the June 2012 

campaign. However, based on flow trends established for the other 3 smelter buildings during 

the 2013 ERS campaign (see Figure 3-7), there is a significant seasonal trend in building 

exhaust flow for the current operation, with higher flows measured in the colder months, and 

lower flows measured in the warm summer months such as June. As a result, it is desirable 

to adjust the AA flows measured in June 2012. The CA is directly connected to the AA and 

was deemed to be the most appropriate measurement to scale off, as it is impacted by similar 

factors and sources. 
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Results from June 2012 indicate that average total AA flow (in scfm) is roughly 5% lower than 

average converter aisle flow (scfm). These have been corrected to account for minor updates 

to roof monitor dimensions (see Table 3-1) and average velocities measured in June 2012. 

To follow the variation in flow measured for the CA during the ERS, this ratio was assumed to 

be fixed to estimate AA flows. 

Figure 3-7: Monthly Trends in Building Flow Rates

3.6 Throughput Adjustments – Annualized Emissions

The calculation of annual emissions for current operation requires a method to normalize 

emissions based on throughput during the applicable sampling period. Key operating 

variables impacting SO2 emissions were established for the June 2012 sample campaign. 

The same parameters were calculated for the 2013 ERS campaign period, as summarized in 

Table 3-3. To account for <100% valid SO2 mass emission sampling data within this period

for most smelter buildings (see Table 3-2), a factor was applied to represent the throughput 

corresponding to the estimated SO2 emissions during the period, in order to accurately 

estimate mass emissions of SO2 per short ton of throughput. For example, if 95% of the data 

over the 275 day full anode aisle sample period is valid, the equivalent number of good 

anodes produced is 144,779 st (152,399 x 95%). This avoids assuming that all missing data 

was 0 lb/h SO2.
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Table 3-3: Plant SO2 Emissions and Throughput during 2013 Extended Roofline Study (ERS)

Area

SO2 

Production

Sampling 

Period

Total During Sampling Period,

Throughput Scaling Parameter

ppm Days Parameter Value Unit

AA 8.59 275 Good anodes produced 152,399 st

CA 12.39 235 ELF matte 198,590 st

Isa Building 14.46 275 Isa feed (NMBM) 507,061 st

ELF Building 8.18 245 ELF matte and ELF slag 453,050 st

Over a complete year of operation, the mass emissions of SO2 are expected to scale from 

total emissions measured during the test period based on the annual throughput. For a typical 

annual throughput of 689,000 dstpy of new metal bearing materials (NMBM), consistent with 

the Feasibility project design criteria, the annual throughput of each scaling parameter is 

summarized in Table 3-4. The net adjustment factor is also shown, reflecting the annual 

throughput divided by the total throughput during the sample period and the % of data over 

this period that is valid. The same proportion is multiplied by the total SO2 measured from 

each building over the ERS to calculate annualized emissions at a plant throughput of roughly 

689,000 dstpy NMBM.

A factor of 1.0 corresponds to a full year of valid sampling data, a factor of 2.0 corresponds to 

half a year of sampling data. In general, the valid data summarized in this report represents 

7-9 months of valid sampling data, depending on the smelter building. This represents almost 

100 times more sample data than the June 2012 campaign.

Table 3-4: Annual Plant Throughput Basis

Area

Annual Throughput Net Adjustment Factor

Parameter Value Unit Annual SO2 / total 

measured SO2 (st)

AA Good anodes produced 187,365 st 1.32

CA ELF matte 322,419 st 1.63

Isa Building Isa feed (NMBM) 688,796 st 1.46

ELF Building ELF matte and ELF slag 748,399 st 1.65

3.7 Weighting Factor for Unequal SO2 Concentration from Each Sample 

Point

For each building there is only a single combined SO2 concentration measurement, reflecting 

equal flows extracted from 2 to 4 separate locations. In the absence of SO2 concentration 

measurements from each sample location, there are two possible approaches to calculate 

SO2 emissions using the single SO2 concentration measurement. 
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One approach is to ignore any differences in SO2 concentration at the individual sample 

locations and multiply the blended average concentration measured for each building by the 

calculated flow (in scfm) for each section (discharge area) of that building. This is referred to 

herein as the “simple” approach. 

The second is to estimate the different SO2 concentrations from each sample location and 

multiply by the flow measured for that section of the building. Velocity and temperature are 

the only parameters measured at each individual location. Velocity through the roof monitor is 

a possible proxy for SO2 concentration and was used to assess the June 2012 results but is 

impacted by other factors, including building height and roof monitor dimensions (i.e., 

narrower opening or higher roof monitor = increased velocity regardless of contaminant 

concentration). With dimension changes and movement of sampling locations in the 2013 

ERS, velocity was no longer deemed to be a good proxy. As a result, it is not relevant to 

compare the relative adjustment factors applied in the June 2012 and 2013 ERS sampling 

campaigns. 

Temperature rise above ambient is believed to be a more reasonable proxy for contaminant 

concentrations within a given building as most sources of SO2 also release significant heat 

into the buildings. For example, if the temperature rise is 40°F above ambient at location 1 

and 20°F above ambient at location 2, the SO2 concentration at location 1 is assumed to be 

double as well. 

Data filters were set to round up to zero for the contribution from locations where the sample 

temperature was less than ambient. This scenario would realistically correspond with little or 

no SO2 emitting activities below in the aisle so it has a small impact on the calculations. 

Another data filter was applied when the average temperature from all sources combined was 

less than ambient. For these situations, where there is typically very low SO2 as well, the 

simple calculation approach was used without any attempt to weight the relative contribution 

from each sample point. This is thought to be a more conservative approach than assuming 

no SO2 emission for the combined gas stream.

3.7.1 Simplified vs. Concentration Weighted Approach

Table 3-5 summarizes the results for each building using the Simplified and Weighted 

adjustment calculation approaches. These correspond to mass emissions over the 

approximately 9 month sample period; they have not been normalized to annual emissions. 

Over the extended sampling period, the simplified calculation approach aligns very well with 

the more complex concentration weighted calculation approach. Based on these results, the 

simple calculation methodology is the recommended basis for all SO2 results presented in 

this report and is recommended for future emission estimates. 

The design factor used in the project emission inventory (e.g. 20% used in the feasibility 

study) should be sufficient to capture minor deviations when using the simplified approach. 
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Table 3-5: Simplified vs. Concentration Weighted SO2 Emissions Calculation Results

Area Sampling Period

Total SO2 lbs Emissions During Test Period

Simplified Adjusted Deviation

AA Apr 1 - Dec 31, 2013 292,578 292,530 100%

CA Apr 1 - Dec 31, 2013 420,661 413,996 98%

Isa Building Apr 1 - Dec 31, 2013 144,790 147,683 102%

ELF Building May 1 - Dec 31, 2013 64,689 70,467 109%

Total - 922,717 924,675 100%

4. Results

4.1 SO2 Concentration 

Both minute and hourly SO2 concentrations were provided by FCX, though the valid hourly 

data covers a shorter timeframe (starting in March 2013). 

The minute-by-minute data was processed over the entire December 2012 to December 

2013 sampling period, representing almost 13 months of data. The resulting average ‘ppm’ 

concentrations are compared to the concentrations from June 2012 in Table 4-1. 

Table 4-1: SO2 Concentrations from Extended Roofline Campaign 
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On average the Dec. 2012-Dec. 2013 SO2 concentrations aligned reasonably well with the 

June 2012 concentrations, with the exception of the ELF building where the SO2

concentration appears to be high compared to June 2012. The full period average is weighted 

by the equivalent sampling days each month, which reflects the removal of invalid data, per 

Section 3.2 and 3.3 (calibrations, equipment maintenance, relocated converter aisle probes 

for testing of the mouth cover above converter #2, etc.). 

4.2 Hourly vs. Minute SO2 Data

In order to calculate SO2 mass emissions, both flow and temperature data are required but 

were only available on an hourly average basis, along with a second set of SO2 ppm data 

averaged over the same time frame. A comparison was performed between two SO2 data 

sets, with both minute and hourly concentration data available, in order to confirm whether or 

not the hourly data could be used with confidence. 

Table 4-2 provides a summary of the minute and hourly averaged SO2 data. From the 

average of the two data sets it is apparent that they correspond well to one another and 

therefore the hourly averaged SO2 ppm data can be used with confidence to accurately 

reflect the more detailed minute-by-minute data. This reduces the massive amounts of data 

that need to be processed.

Table 4-2: Comparison Between Minute-by-Minute and Hourly SO2 Data

4.3 Mass Emissions

Annualized results from the 2013 ERS for current operation were presented in Table 2-1,

along with the data based on June 2012. Total annualized SO2 emissions are lower by 

approximately 20%. Annualized emissions are substantially lower than June 2012 for the Isa 

building (55% lower) and CA (20% lower). ELF building emissions are roughly 50% higher, 

and AA emissions are approximately 20% higher. The increase in AA emissions is attributed 

primarily to a revision in the measured roof monitor width from 4.0 ft to 4.5 ft. 
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The Total Annualized Emissions (stpa) are based on the simplified calculation approach (no 

weighting was applied to account for different SO2 concentrations from each sample point). 

All results over the sample period have been scaled to annual emissions, based on 

established throughput scaling parameters for each building. The period of valid sampling 

data for the ERS campaign is almost 100 times greater than the June 2012 campaign.

There are multiple reasons why the two sampling campaigns do not correlate directly with 

one another, including:

• Updated roof monitor length and width dimensions (Section 3.1). This includes the 

calculation of gas flows for individual sections/emission areas within the converter and 

anode aisle, rather than using average velocities multiplied by the total roof monitor area.

• Changes in sampling locations (Section 3.1).

• Different data filtering methodologies (e.g., rounding up negative concentration values to 

0, see Section 3.3).

• Application of the “simple” average SO2 concentration measured for each building, rather 

than attempting to weight the SO2 concentration from each sample location based on 

indicative parameters such as temperature or velocity (Section 3.7).

The impact on expected plant emissions and the corresponding SO2 GLC for the future 

operation with the proposed mitigation scope in place is expected to be a minor reduction.