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© Hatch 2013 All rights reserved, including all rights relating to the use of this document or its contents. 

Project Memo 

H341001 

November 14, 2013 

To: C. West From: J. Nikkari 

 

cc: FCX

A. Binegar 

J. Spehar 

T. Weaver 

Hatch

I. Carruthers 

R. Sullivan 

 

Freeport-McMoRan Copper & Gold Inc. (FCX) 

Miami Smelter Expansion Feasibility Study 

SO2 Capture Efficiency - Current Operation 

1. Introduction 

Freeport-McMoRan Copper & Gold Inc. (FCX) retained Hatch to develop a Feasibility Study 

assessing expansion of the Miami Smelter throughput to a maximum permitted capacity of up 

to 1 million dry short tons per year of new metal bearing materials, while complying with the 

EPA’s revised National Ambient Air Quality Standard (NAAQS) for Sulfur Dioxide of 75 ppbv 

(1-h). The project is referred to as the Miami Smelter Expansion Project. 

During the permitting process for the project the ADEQ and/or USEPA have requested further 

support for specific aspects of FCX Miami’s emission calculations. 

This response specifically addresses an EPA request for additional details supporting 

the current operation SO2 capture efficiency to the primary and secondary systems, 

along with uncaptured smelter building (process) fugitives. 

2. Design Basis 

2.1 Emission Inventory - SO2

Per current permit requirements, average hourly operating emissions have been used for the 

purpose of assessing compliance with the new ambient SO2 GLC standard of 75 ppbv (1-h). 

Average operating emissions are used to define the inputs for dispersion modeling, which 

ultimately determines the emission reduction requirements and Miami Smelter Expansion 

Project compliance scope. 

The SO2 emission inventory presented in this section was used as the basis for the sizing, 

selection and/or design of equipment to be installed as part of the project to meet the ambient 

SO2 objective. 
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2.1.1 Annual SO2 Emissions – Current Operation 

Annual emissions for “current” operation are summarized in Table 2-1. Smelter building 

fugitive emissions are calculated based on roofline testing conducted over a 3-4 day period 

for each building in June 2012, in lieu of the prior sulfur balance approach. Further details are 

available in the FS Environmental Design Criteria (H341001-0000-07-122-0001). 

Table 2-1: Annual SO2 Emissions – Current Operation 

Source 

Current 

Emissions 

(st/y) 

Basis 

Vent Fume Scrubber Stack 331 2010 FCX Title V permit reporting 

Acid Plant Tail Gas Scrubber Stack 1,415 2010 FCX Title V permit reporting 

Smelter Building Fugitives 1,031 June 2012 gas sampling x 120% 

Acid Plant Bypass Stack 

Excluded from FS 

project scope 

98 t in 2010. Excluded from 

dispersion modeling at present. 

Miscellaneous/Other Fugitives N/A Assume negligible 

It is noted that longer term roof line SO2 measurements are currently being conducted to 

assess any potential project scope impacts ahead of the execution phase. 

2.1.2 Detailed SO2 Inventory – Smelter Building Fugitives 

The annual SO2 emissions in Table 2-1 do not provide sufficient detail to establish the 

required SO2 mitigation scope for smelter building fugitive SO2 emissions. A more detailed 

inventory for the existing smelter, by activity and/or equipment (total of 35 identified), was 

developed and summarized in the FS Environmental Design Criteria (H341001-0000-07-122-

0001). 

A high level summary by smelter building is provided in Table 2-2. 
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Table 2-2: Smelter Building (Process) Fugitive SO2 Emissions – Current Operation 

Emission Base Year:

Sampling Campaign - Building Fugitives: 2012 Gas Sampling, adjusted to 689k dstpy NMBM

Factor for Unmeasured Fugitive Emissions:

Stacks

ANNUAL 

EMISSIONS

OPERATING 

HOURS EMISSIONS

stpa hr g/s

1,415 7,610 46.9

331 8,157 10.2

Fugitive Sources

 Fugitive SO2 

Contribution

ANNUAL 

EMISSIONS

OPERATING 

HOURS EMISSIONS

% stpa hr g/s

100% 1,031 7,610 34.1

0% 0 Per Above 0

28% 287 Per Above 9.5

4% 42 Per Above 1.4

68% 702 Per Above 23.2

0% 0 Per Above 0

Base (689k)

1.2

2010 (689k dstpy NMBM)

Annual fugitive SO2 tonnage scaled from test period SO2 measured and corresponding throughput relative to annual throughput at 689k dstpy NMBM.

Background / Unaccounted Sources*

IsasmeltTM Roof Vent

Electric Furnace Roof Vent

Converter and Anode Aisle Roof Vent

Other Non-Smelter Building Fugitive Sources*

*NOTE: Excellent operating/maintenance practices are required to minimize these to achieve 75 ppbv (leakage, etc.). 

Base (689k)

ITEM

-

Total site-wide Fugitives (excluding bypass stack for 

modeling)

ITEM

-

Acid Plant Tail Gas

Vent Fume Scrubber
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3. Capture Efficiency Calculations – Existing Operation 

The calculation approach used herein is consistent with the original EPA spreadsheet, 

updated to reflect the current measured emissions, as summarized in Section 2.1. 

3.1 Primary Capture 

3.1.1 Isa (Smelting) Furnace 

Almost all SO2 generated from the Isa and electric furnaces comes from the Isa furnace. The 

electric furnace is included with the Isa furnace in these calculations to ensure full accounting 

of SO2. Primary capture is to the acid plant. Uncaptured emissions are assumed to enter the 

vent fume scrubber, though in reality they enter either the vent fume scrubber or are emitted 

from opening in the building, primarily at the roofline (see Section 4). Additional uncaptured 

fugitive emissions from either the acid plant or vent fume systems are accounted for 

separately in Section 3.2.2. 

Total vent fume scrubber emissions 

= 331 stpa (Table 2-1) 

Approximate vent fume scrubber efficiency (SO2) 

~ 80% based on reagent consumption data 

Uncaptured primary emissions from Isa and ELF to secondary (vent fume) system 

= Inlet SO2 to vent fume scrubber from Isa and ELF 

= 331 stpa emissions / (1-80% capture) 

= 1655 stpa 

Total SO2 from Isa (and ELF) 

~ 65% of total from feed 

= 65% x 689,438 stpa concentrate x 33.5% S x 64 lb SO2 / 32 lb S 

= 300,048 stpa SO2

Capture Efficiency 

= 1 – Uncaptured / Total SO2 from Isa 

= 1 – 1655 / 300,048 

= 99.45% 

Captured SO2

= Total from Isa – Uncaptured 

= (300,048 – 1655) stpa = 298,393 stpa 
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3.1.2 Hoboken Converters 

Most SO2 generated in the aisle comes from the converters and is captured in the acid plant. 

The entire aisle is included in these calculations, including the converters, anode furnaces, 

mold barrel, ladle transfer and crane activities, etc. It is not practical to accurately separate 

the converter emissions from other aisle emissions. Primary capture is to the acid plant. 

Uncaptured emissions are emitted from the roofline building ventilation monitors in the 

combined aisle. 

Total roofline emissions (converter and anode aisle roof vents) 

= 702 stpa (Table 2-2) 

Total SO2 from converters (and anode furnaces) 

~ 35% of total from feed 

= 35% x 689,438 stpa concentrate x 33.5% S x 64 lb SO2 / 32 lb S 

= 161,564 stpa SO2

Capture Efficiency 

= 1 – Uncaptured / Total SO2 from converters 

= 1 – 702 / 161,564 

= 99.57% 

Captured SO2

= Total from converters – Uncaptured 

= (161,564 – 702) stpa 

= 160,862 stpa 

3.2 Secondary Capture 

3.2.1 Electric Furnace 

Total roofline emissions 

= 42 stpa (Table 2-2) 

Capture efficiency: 

Not applicable since this was grouped as a minor contributor with the Isa furnace (primary 

gas to acid plant, secondary gas to vent fume scrubber) in Section 3.1.1. 
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3.2.2 Isa (Smelting) Furnace 

Total roofline emissions (Isa building only, ELF covered in Section 3.2.1) 

= 287 stpa (Table 2-2) 

Total SO2 to vent fume scrubber 

= 331 stpa emissions / (1-80% capture) 

= 1655 stpa 

Capture Efficiency 

= 1 – Uncaptured / Total SO2 to Vent Fume Scrubber 

= 1 – 287 / 1655 

= 82.66% 

3.3 Control Efficiency 

Control efficiency for captured SO2 is calculated individually for each of the three emission 

routes, as follows: 

Acid Plant 

= 1 - Tail Stack Emissions / Inlet SO2 

= 1 - Tail Stack Emissions / (SO2 from vessels – SO2 missed by primary system) 

= 1 - 1425 stpa (Table 2-1) / [(300,048 + 161,564) stpa SO2 from vessels – 1655 st/y SO2 to 

vent fume scrubber - 287 stpa fugitives from Isa - 42 stpa fugitives from ELF] 

= 99.69% 

Vent Fume Scrubber 

~ 80% based on reagent use 

Roofline Emissions 

= 0% (no treatment at present) 

3.4 Overall SO2 Removal Efficiency 

Overall SO2 removal efficiency (excluding minor bypass stack emissions) is calculated below: 

= 1 – Total SO2 emissions (Table 2-1)/ Total SO2 from vessels 

= 1 – (Stack Emissions + Fugitive Emissions) / Total SO2 from vessels 

= 1 – (1415 stpa from tail stack + 331 stpa from vent fume stack + 1031 stpa total fugitives) 

/ (300,048 stpa from Isa + 161,564 stpa from converters) 

= 99.40% 
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At these high % removals for SO2 from the smelter overall, estimation of residual emissions 

via mass (sulfur) balance is not inaccurate. 

4. Alternative Calculation Approach 

All calculations have been updated above to better reflect the measured emissions, in lieu of 

the prior sulfur balance approach. However, the spreadsheet provided presents a simplified 

sulfur balance for the Miami smelter. An alternate approach is presented below which would 

better reflect the capture efficiencies for the Isa (and ELF) buildings, where some gas is 

captured in the secondary system and a portion is emitted untreated from the building. The 

same discrepancy does not exist in the aisle since any emissions missed by the primary 

system are emitted to atmosphere (no secondary capture). The calculations for the Hoboken 

converters (and other aisle emissions) would remain per Section 3.1.2 (99.57%). 

The original calculations for the Isa (and ELF) building are broken down for: 

1) Primary capture to the acid plant vs. secondary capture to the vent fume system; and 

2) Vent fume capture vs. smelter building fugitive emissions. 

In reality, Isa furnace emissions which are not captured in either the primary (acid plant) 

system or secondary (vent fume) system are emitted to atmosphere untreated from the 

building. The net impact is shown below: 

Overall Isa (and ELF) primary capture efficiency to acid plant 

= 1 – total SO2 missed by primary system / total SO2 from vessels 

= 1 – (Inlet SO2 to vent fume scrubber + roofline fugitives) / total SO2 from vessels 

= 1 – (1655 stpa + 287 stpa fugitives from Isa + 42 stpa fugitives from ELF) / 300,048 stpa 

= 99.34% (vs. 99.45% in Section 3.1.1) 

The Isa secondary capture efficiency reported in Section 3.2.2 would also be modified 

slightly. In particular, the roof vent emissions are not part of the 1655 stpa captured in the 

vent fume system; they should be in addition to it. If all roofline fugitives from these buildings 

are attributed to those missed by the secondary (vent fume) system the correct capture 

efficiency for Isa (and ELF) furnace gas to the vent fume system is shown below: 

= 1 – roofline fugitives / total SO2 missed by primary system 

= 1 – roofline fugitives / (total SO2 to VFS + roofline fugitives) 

= 1 – (287 stpa fugitives from Isa + 42 stpa fugitives from ELF) / 

(1655 stpa + 287 stpa fugitives from Isa + 42 stpa fugitives from ELF) 

= 83.4% (vs. 82.66% in Section 3.2.2) 

The end result is very similar efficiencies (and no change for the converter aisle) but what 

appears to be a more logical basis for reporting of primary and secondary capture efficiency. 
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The overall capture efficiency for primary and secondary emissions from the Isa (and ELF) 

building is best reflected by the calculation below: 

= 1 – roofline fugitives / total SO2 from vessels 

= 1 – (1415 stpa from tail stack + 331 stpa from vent fume stack + 287 stpa fugitives from Isa 

+ 42 stpa fugitives from ELF + 702 stpa fugitives from aisle) / (300,048 stpa from Isa + 

161,564 stpa from converters) 

= 99.89% 

5. Conclusions 

An update of the FCX Miami annual emission spreadsheet has been provided, with updated 

numbers reflecting current operation, notably fugitive emissions based on a smelter building 

roofline sampling campaign conducted in June 2012. The resulting “capture” efficiency and 

overall SO2 removal efficiency are significantly higher than those predicted using the prior 

sulfur balance approach. 

Similar results are also presented for an alternative calculation approach that should better 

reflect the capture efficiencies for vessels which have both primary and secondary capture in 

place (i.e., Isa and ELF). 

J. Nikkari 

JJN:pp