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Acid Plant Database  July 6, 2015

Owner Freeport-McMoRan Copper & Gold Inc.

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Location Dos Pobres Copper Mine
Graham County
Safford, Arizona
Background -
Website www.fcx.com
Plant -
Coordinates 32° 55' 49" N, 109° 42' 14" W
Type of Plant Sulphur Burning
Gas Source Elemental Sulphur
Plant Capacity Original Nameplate: 1250 MTPD
Re-rated: 1550 MTPD
SA/DA 3/1 DA
Emissions SO2: < 20 ppmv
Emissions achieved using a DynaWave caustic tailgas scrubber
Status Operating
Year Built 2011
Technology MECS
Contractor Aker/Jacobs
Remarks Reported project cost US$150 million
To accelerate the project, the plant design is based on the SF Phosphates plant in Rock Springs, Wyoming

Bed 4: Cesium Catalyst
Blower: Electric Motor, Toshiba VFD

Acid Transfer: 3 mile pipe line, 500 ft elevation change, 3 in-line pumpe, 98.5% H2SO4, pump discharge pressure = 460 psi
Permits Arizona Department of Environmental Quality  www.azdeq.gov
Facility ID:
Air Quality Class I Permit
Permit No. Issue Date Expiry Date Details
- - - -
General There are plenty of aspects to consider when building a $150 million sulfuric acid plant. However, for owner Freeport-McMoRan Copper & Gold, the No. 1 priority during construction of the 50,000-square-foot production facility adjacent to its open-pit copper mine in Safford, Ariz., is the safety of the more than 800 workers who will man this job at the height of the construction schedule.  “It is a challenge trying to manage a large group like that safely and efficiently,” says David Simmons, project manager for Freeport-McMoRan.  Add a fast-track schedule and a job site with limited space to the mix and you get a project that would have most contractors scratching their heads about how to pull it off. However, with an experienced company like Jacobs Engineering on the job as the engineering, procurement and construction manager, the project was delivered within budget and on time in April 2011.  The sulfur-burning plant is a key component of the Dos Pobres copper mine in Safford. The high-efficiency facility supports the copper leach-and-recovery process; sulfuric acid is required to recover copper from raw ore.  To keep up with the 1,550 tons of copper ore per day produced by the mine, the sulfur plant has the capacity to produce approximately 500,000 tons of acid annually. The plant sits on a 10-acre site with an enclosed building that houses the control room directly behind it. The main facility contains 5,000-horsepower main compressors, a catalytic converter, gas-to-gas heat exchangers, absorber columns and associated process controls, according to Simmons. 

With so many trades involved for this project, safety was at the forefront of everyone’s minds during construction of the sulfur plant. Simmons says the leadership team hammered this point home throughout the yearlong schedule. This included hosting tailgate meetings to address potentially dangerous situations as well as detailed, site-specific procedures posted throughout the job site.  The job site also implemented a “Stop the Drop” program that kept workers out of harm’s way during the various crane lifting processes. This created a systematic way to alert all employees on the job site that cranes were in use by sounding horns, flagging areas and setting up barricades around the area.  “There was a high level of awareness for this one,” Simmons says.  Along with paying close attention to the location and operation of cranes on the job site, trades working on the sulfur plant had to make room for each other in tight conditions. With as many as eight cranes on site at any given time, the trades shared cranes as much as possible.  “The crane sharing was successful,” Simmons explains. “If you let every subcontractor have its own crane, it would have been an impossible task. We strategically located multiple cranes to be used by all the different subs instead.”

Though the capacity to produce 1,500 tons of copper makes this facility one of the most efficient in existence, it took some cajoling by Jacobs Engineering to bring the plant to this state. The original capacity for the plant was designed to top off at 1,350. However, a week before groundbreaking was set to commence, Freeport-McMoRan decided to increase capacity to 1,500.  Although this was only a 15 percent hike, the Simmons says this essentially changed the entire scope of the project. For instance, sulfur plants like this typically require cast iron pipes fabricated with silica lining for protection against erosion. These pipes – known as Mondi pipes – are cast in specific sizes and typically take four to six weeks to deliver.  With the increased capacity, the pipes originally delivered to the site did not meet the new requirements for the project. Instead of ordering new pipes and delaying work for a month or so, the construction team reached out to a job shop located in Phoenix that could retrofit the Mondi pipes in less than two days.  While the incremental cost of the increased capacity was $3 million, Simmons says the project would not have continued without a hitch without the talented EPCM team Jacobs had in place. “The fact that we had such a good engineering and procurement and construction team was key,” Simmons says. “Our mantra was, ‘Just move forward,’ so we kept moving forward while understanding we might run into issues along the way.”  For the controls of the structure, Simmons says approximately 1,200 integrated operations systems had to be coordinated with the main facility, including a Foundation Fieldbus two-way communications system and conventional analog systems. Some of the technology was new to a number of the contractors on site, so Foundation Fieldbus set up onsite training programs for the Freeport-McMoRan employees who would serve as instrument hands.  Along with the Foundation Fieldbus field team, Freeport-McMoRan also commissioned the construction of a training simulator for the facility. The company tapped SNC-Lavalin for this portion of the job.  The simulator not only helped get operators up to speed on how to run the facility, but also taught them how to handle potentially critical situations. These operators can now handle high-pressure steam in a 750-psi system, which could lead to dangerous conditions if not operated properly. Operators knew exactly how to run the highly technical facility long before it was operational.  “Our operators knew how to run this thing by startup,” Simmons says. “It provided a way to train operators with mitigated risk. It was especially useful for new processes and inexperienced operators.  “Among lessons learned, this one of the best things we’ll recommend going forward,” Simmons adds.

The 750-psi system is part of a self-sustaining power-generating plant created for the sulfur-burning facility. The superheated steam from the 17-megawatt steam generator powers plant. Gas scrubbers decrease the SO2 emissions by more than 20 percent below regulated mandates.  “Part of our recent performance test came in considerably below the recent PPO,” Simmons says. “That is a real feather in our cap. The acid plant exports power to the mine site.  “It is an island – the acid plant is part of a startup that can go into island mode,” he adds.  “Everything else around us can shut down and we can continue to operate. It provides acid to the site, but it also exports power.”  Because of the remoteness of the site, the project required a 3-mile-long pumping system to transfer its product. This system, designed by HDR Engineering of Phoenix, involves three in-line vertical pumps and stainless steel pipe fully contained in a heat deflection temperature liner.  “This pump is capable of transferring all product 3 miles with elevation changes that drop lower than 500 feet,” Simmons says. 

Freeport-McMoRan benefits from having a corporate engineering division that designs facilities like this sulfur-burning plant throughout the world. This, combined with the subcontractors hired by Jacobs Engineering, created a formidable team that could adapt to any situation created during the course of construction.  “This team was incredibly flexible and supported all aspects of the project,” Simmons says.“Our mantra was to move forward and resolve problems,” he continues. “We understood there would be obstacles and conflicts, so we had daily meetings to inform each other of what was pertinent and hot.”

Original Article
References Sulfuric Acid Today - Freeport-McMoRan Answers Call for Copper with New Acid Plant, Spring/Summer 2012

September 16, 2011 - A collision Wednesday night between a semi truck hauling molten sulphur and a pickup truck resulted in a hazmat situation and the closure of Safford/Bryce Road for nearly 13 hours.  According to a press release from the Graham County Sheriff's Office, the County Dispatch received a call regarding the collision at about 6:21 p.m. The incident occurred as both vehicles were westbound on Safford/Bryce Road just west of Branding Iron Road.  According to Sheriff P.J. Allred, the driver of the semi truck, Dwayne Elders of Thatcher, was attempting to pass the pickup truck when the collision occurred. Apparently, the driver of the pickup truck, Dana Carrasco of Safford, attempted to make a left turn into a private driveway when she was sideswiped by the semi. The semi rolled onto its side and stretched across both lanes of the road. Allred told the Courier that Elders said the pickup truck didn't have its turn signal on, but Carrasco insisted that she did.  Elders was transported to the Mt. Graham Regional Medical Center by Southwest Ambulance where he was treated and released. He suffered a head laceration and fractured collar and rib bones, according to Allred.  Carrasco had her 4-year-old daughter with her in a child safety car seat, and neither was injured.  Molten sulphur began leaking out of the top cap of the transport tanker but was quickly contained and handled by the Safford Fire Department. Hazmat teams from the Department of Public Safety traveled from Globe and Tucson and assisted with the leak as well. According to the United States government Material Safety Data Sheet, molten sulphur gives off an odor of rotten eggs and is flammable.  It can cause eye and skin irritation and should only be used with adequate ventilation.  Safford Assistant Fire Chief Tony Goodman told the Courier that the biggest issue with dealing with the molten sulphur was that it was hot. He said the department sprayed down the leak with water to cool it.  Once it was cooled, the molten sulphur solidified. Members of the Fire Department worked the scene until 4 a.m. to keep the molten sulphur contained.  "The only hazard is that it's hot. As soon as it hits air, it cools down and solidifies pretty quickly . . ." Goodman said.  Representatives from Freeport McMoRan Copper & Gold Inc. and Savage Trucking also assisted with the crash recovery. The semi is registered to Savage Trucking and was transporting molten sulphur to Freeport's Safford Operations copper mine.  Freeport representatives brought a crane to assist with the removal of the semi. Tow trucks from Barnett Towing from Willcox and Tucson were also used to set the semi upright and remove it from the road.  Personnel from the Graham County Highway Division were also on hand to assist with the cleanup and fix damage to the road. The road remained closed from Landfill Road to the Talley wash until about 7 a.m. on Thursday.  According to the Sheriff's Office, the cause of the crash is yet to be determined and is under investigation with assistance from a Graham County Attorney's office crash reconstructionist.

September 29, 2010 - The sulphur burner at the Freeport-McMoRan copper mine at Safford is approximately 35 percent complete.  The construction of the facility is on schedule, and completion is expected in the late first quarter or early in the second quarter of 2011, Freeport spokesman Richard Peterson said in an e-mail to the Courier.  Peterson also said about 170 contracted construction workers are on-site. That number is expected to increase to about 250 later this year.  “The construction crews have been very safety conscious, working 92,000 man-hours with no (time lost to injuries) and only one reportable injury,” Peterson said.  “Also, a milestone was recently achieved when the 15-megawatt steam turbine was set into place. It will drive a generator to produce electricity.”   Peterson said in April the electricity produced is more than what is needed to operate the sulphur burner. The extra wattage will be used to support part of the electricity needed for the Safford mine.  The sulphur burner will produce sulfuric acid, which is required in copper recovery from raw ore.  Until the sulphur burner is complete, trucks will still deliver sulphuric acid to the Safford mine.  Even after the sulphur burner is in operation, the mine will require delivery of sulphuric acid, although the number of deliveries will be reduced, Paul Cook of Freeport told members of the Local Emergency Planning Committee last month.

September 3, 2010 - Sulfuric acid produced at Freeport-McMoRan's Safford mine will probably remain on site and the mine will require additional acid to be shipped in, members of the Local Emergency Planning Committee recently learned.  Paul Cook of Freeport-McMoRan Copper & Gold presented information about the dangers of sulphuric acid during the Aug. 26 LEPC meeting.  According to Cook, trucks carrying concentrated sulfuric acid bear signs with the numerals 1830 on them. Some of these trucks will remain on the highways because the sulfur plant at the Safford mine will not produce enough acid for the mine and more will have to be trucked to the site. It is also unlikely that acid produced at the Safford mine will be shipped elsewhere.

April 28, 2010 - Freeport-McMoRan is ramping up activity at two Arizona mining operations.  It will begin construction on a sulphur burning plant at the Dos Pobres Copper mine in Safford. The plant will produce sulfuric acid, which is used to extract copper from ore.  The $150 million project had been delayed for 16 months.  It's expected to provide about 250 jobs during construction.  The plant should be operational in 2011.   Freeport-McMoRan is also raising production at its Morenci mine and hiring 400 workers to meet demand.  More than 1,500 jobs were cut in Morenci in 2008 and 2009 as demand for copper fell and dragged prices down from record highs.

April 25, 2010 - After a 16-month delay, Freeport-McMoRan Copper & Gold will move ahead with construction of a sulphur-burning plant at the Dos Pobres copper mine at Safford.  The sulphur burner will produce sulfuric acid, which is required in copper recovery from raw ore.  While the sulphur burner is expected to require few new permanent employees, about 250 construction employees will work on the project at its peak, according to Freeport spokesman Richard Peterson. He did not specify how long the project’s “peak” period will be.   The Arizona Department of Environmental Quality approved revisions of Freeport’s air quality permit in the fall of 2008 to allow construction of the sulphur burner. Freeport shelved the project in December 2008 in response to declining economic conditions in the copper industry and the United States economy as a whole.  The project is expected to cost approximately $150 million. Completion of the “highly automated plant” is expected in about a year, Peterson said in an e-mail response to questions from the Courier.  “The plant will burn elemental sulphur that will be brought by railcar to a transfer facility that will be built southeast of Fort Thomas. Sulphur will be transferred from the railcars to trucks for transportation to the sulphur burning plant,” Peterson said.  Although there will be an average of 18 trucks a day, the transport plan is expected to reduce overall track traffic on Highway 70 because every truck of elemental sulphur will replace two trucks of acid, according to Peterson.   He also said the plant will have a capacity of approximately 465,000 tons of sulfuric acid per year.  Waste heat from the sulphur burner will be used to produce 15 megawatts of electric power.This is 10 more than needed to operate the acid plant. The remainder will be used to support part of the electricity demand from the Safford mine.

MTPD - Metric Tonne per Day           STPD - Short Ton per Day
MTPA - Metric Tonne per Annum      STPA - Short Ton per Annum
SA - Single Absorption
DA - Double Absorption

* Coordinates can be used to locate plant on Google Earth