Design, Construction and Startup of the Ilo Smelter Modernization Project
By Walqui, Henry Noriega, Carlos
Southern Copper Corp. (SCC) is one of the world’s largest copper companies. It finished the modernization of the Ilo copper smelter. A single Isasmelt furnace started smelting 1.1 Mt/a (1.2 million stpy) of concentrate at the end of 2006. Three existing Pierce Smith converters were upgraded plus a new one for converting the matte to blister copper was installed. Two new anode furnaces and a twin anode casting wheel have been operating since January 2006. This represents one of the main changes in the process because the final product of the smelter is now anode copper instead of blister copper. A new oxygen plant, acid plant and others facilities are operating. This environmental project ensured that the new smelter complied with the environmental regulations of Peru by the end of January 2007. This article summarizes the background to the modernization project, describes the different stages of the project including engineering, procurement and construction, describes the main areas of the new copper smelter and also the pre-operational testing, commissioning and start-up of them.This is a brown field project with a target of reducing as much as possible the production losses of the previous operation.
The article also presents the details of the development of the Ilo smelter modernization project and explains the main aspects of the new facilities, the products obtained and the associated facilities for their commercialization, including a marine trestle for bulk acid exportation.
SCC is one tne world s largest copper companies. Based on 2004 sales, SCC can be consider the world’s fifth largest mining company with operations in Mexico (Cananea, Caridad and San Luis de Potosi) and Peru (Toquepala, Cuajone and Ilo).
The Ilo complex, operated by SCC subsidiary SPCC is located in southern Peru about 1,200 km (746 miles) south of Lima. It comprises the world’s sixth largest copper smelter and the eighth largest copper refinery, a precious metal refinery and a sulfuric acid plant.
Since its commissioning more than 45 years ago, the Ilo smelter has been continuously operating and processing copper concentrate from its operations at Toquepala and Cuajone. During this period, several technological changes have been implemented at the smelter, which have allowed it to remain competitive in the market despite swings in the industry, the economy, and the social events of the country and the world.
One of the main purposes for the technological changes implemented at the Ilo smelter in the last 10 years has been to improve the environmental conditions by reducing the sulfur dioxide emissions to the atmosphere.
Beginning in 1960, two reverberatory furnaces were used to smelt the concentrate. In 1975, two new reverberatory furnaces were installed and in 1995, the No. 1 reverberatory was decommissioned. In 1998, the No. 2 furnace was decommissioned. During the 1990s, aTeniente converter was installed to supplement the two remaining reverberatory furnaces.The first environmental improvement plan, implemented in 1995, enabled the Ilo smelter to capture 60 percent of the sulfur contained in the concentrate processed in the Teniente converter through the installation of an acid plant capable of producing 136 kt/a (150,000 stpy) of sulfuric acid. In 1998, after the commissioning of the expansion of the first acid plant, it was possible to capture 100 percent of the metallurgical gases produced by the Teniente converter and produce 272 kt/a (300,000 stpy) of sulfuric acid.
With the official approval of its Environmental Compliance and Management Program (PAMA: Programa de Adecuacion y Manejo Ambiental), in January 1997, SCC made a commitment to capture at least 91.7 percent of the SO, generated in the Ilo smelter by January 2007. To achieve this goal, in early 2004 Southern Peru commissioned the Ilo smelter modernization project.
This modernization project will have a positive environmental impact by not only reducing the sulfur emissions but also by significantly reducing the fuel consumption of the smelter, estimated at more than 65 percent.This modernization project is the biggest investment and environmental project developed in Peru.
History of the current modernization project
In 1999, SCC decided to evaluate the scope of the modernization plan, taking into account to the lower copper price, the future market perspectives and the high investment cost expected for the further steps contemplated in the modernization plan. Following several evaluations and studies aimed at identifying the best options to modernize the smelter, in May 2003, SCC requested bids from six international partnerships.
The basis for the technical bids were defined as follows:
* Smelting capacity: 726 kt to 1.1 Mt/a (800,000 to 1.2 million stpy) of concentrate, based on the recommendation of each technology.
* Minimum guaranteed sulfur capture: 93 percent (PAMA fulfillment).
* Final product from the smelter: copper anodes.
The technologies considered and engineering companies associated with each bid were:
* Outokumpu flash smelting.
* Mitsubishi process.
* Noranda reactor.
* Teniente converter.
* Kvaerner and Outokumpu.
* Mitsui and Chiyoda.
* SNC-Lavalin and Noranda.
* Fluor and Xstrata.
* Odebrecht and Ausmelt.
* Indec and Codelco.
The technical bids were evaluated by SCC for a treatment capacity of 1.1 Mt/a (1.2 million stpy) of copper concentrate, considering the following aspects.
The efficiency of the new technology, how it would contribute to minimizing the sulfur emissions and compatibility of the selected technology with the existing technologies operating in the smelter.
Operational aspects related to specific consumables, degree of automation, minimization of operational interference and compatibility with the existing equipment and industrial installations.
Operating Costs: Availability of the operation and reduction of specific consumables.
The potential to minimize up front capital expense, potential capital savings in future expansions, reinforcement of the position of SCC for obtaining credits and minimization of risks of payments for environmental breaches.
All of the smelting technologies proposed by the contractors have a proven track record in the worldwide copper industry. However, some technologies have significantly more experience than others, both in terms of the number of installed units and the smelting capacity of those units.
The proposed smelting technologies can be separated into three distinct groups:
Flash smelting has been extensively promoted by Outokumpu (and to a lesser extent by Inco) since its original development after World War II. There are more than 30 operating installations world wide, accounting for more than 40 percent of the world’s production of primary smelted copper. Several of the existing installations are larger (both in terms of smelting capacity and physical size of the smelting furnace) than the unit that was proposed for Ilo.
Bath smelting (stationary vessel)
Bath smelting (stationary vessel) technology has been developed by Mitsubishi (Japan), as part of its Ml-continuous smelting process, and by Isasmelt (MIM) and Ausmelt (both from Australia). The later processes use a single lance to inject oxygen-enriched blast air into the melt, while the Mitsubishi process utilizes multiple smaller lances. The Mitsubishi process has been utilized in four smelters worldwide. Between them, Isasmelt and Ausmelt technologies have been used in seven primary copper smelters.
Bath smelting (rotating vessel)
Bath smelting (rotating vessel) technology has been developed along similar lines by Noranda (Canada) and Codelco (Chile). Originally based on the concept of wet concentrate feed onto the smelting bath, recent units by both companies have utilized dry concentrate injection into the smelting vessel (by submerged tuyeres) to obtain higher production rates. Slightly more than 10 units are presently in operation worldwide.
Given that all of the technologies would fulfill the PAMA environmental requirements and that under all of the proposed scenarios it would be possible to produce anode copper, SCC focused the evaluation on technical and economic merit. As a result, on the basis of this analysis, SCC defined Isasmelt technology as the most suitable technology. A combination of factors contributed to the decision that Isasmelt was the preferred technology. One of the key reasons was its ability to surpass legal specifications requiring collection of sulfur in offgases. The relatively low capital cost was a key advantage. Its ease of operation and flexibility, as demonstrated in plants running in Australia, the U.S., India and China, further added to the convincing arguments. In addition, the technology package provided all of the ingredients that SCC believed were necessary for successful implementation, including an extensive training program in the Mount Isa copper smelter, and access to operations experience made during more than 10 years of operation at a similar scale to the plant at Ilo. Advantages of the selected technology
The main advantages of the selected technology are the following:
* Minimum feed preparation: The feed does not require special preparation or drying.
* Minimum consumable consumption: The lance used in the process can operate for longer than two weeks and then it is only necessary to replace its tip.
* Easy to operate: The process is easy to operate compared with other technologies that might require more sophisticated process control and more careful metallurgical control.
* High smelting rate capacity and excellent turn down ability.
* Low dust production: 1.5 percent dust production.
* Low amount of “in process” material due to the small reactor volume.
* Low operating cost.
* Low level of particulate material emissions.
* Minimum footprint requirement and interferences with the current operation in the construction period.
* A competitive capital expenses.
Following construction of the Isasmelt furnace at the Ilo smelter, it was possible to shutdown the two existing reverberatory furnaces and one Teniente converter. Figure 1 shows the planned Ilo smelter layout.
The main equipment to be installed under the modernization project included the following:
* Feed preparation area: bins and conveyors.
* Silica crushing plant.
* Isasmelt furnace.
* Rotary holding furnace (2 off).
* Isasmelt and Pierce Smith converter gas handling systems.
* Anode furnace (2 off).
* Twin casting wheel.
* Oxygen plant.
* Acid plant and effluent treatment plant.
* Instrumentation and control system.
* Water treatment plant.
* Sea water supply system.
* Acid loading station.
* Ancillary equipment.
* Marine trestle.
The modernized smelter will be able to process all of its concentrate through just one smelting unit with the consequent reduction in operating costs and improved environmental performance.
There are three main differences that need to be pointed out:
* Operation with only one smelting unit: The operation with the Isasmelt furnace presented a new challenge for Ilo smelter. In the previous situation the combination of the reverberatory furnace (low matte grade) and the Teniente converter (high matte grade) gave an extra degree of flexibility not only for the converting process but also for the Teniente converter operation where low grade matte could be added to re-establish any metallurgical equilibrum (slag chemistry control) if required.
* Converting process: Blowing with just two Pierce-Smith converters would require an efficient coordination between the Isasmelt furnace, the RHF’s and the converters.
* Low emission operation: The acid plant would have to receive the offgas streams from the Isasmelt furnace and the Pierce-Smith converters at all times. It would no longer be permissible to send the raw off gas to the stack.
Current status of the project
Demolition and site preparation. This is a brownfield project. For that reason, it was necessary to start the works with the demolition of some areas, where the old reverberatory furnaces were located, in order to use the area for the new Isasmelt furnace and the new anode plant.
These works started during the second half of 2004, when the engineering was developing. Also, it was necessary to prepare the areas for the new acid plant and oxygen plant. The areas for the new anode plant and for the new Isasmelt furnace were ready at the end of 2004 and the excavation for the foundations of the anode furnaces and twin-casting wheel was started.The area for the acid plant was also available at the end of 2004. The area for the oxygen plant was ready during the second quarter of 2005.
The underground works, comprising all of the HDPE, PVC pipes and duct banks, started during 2004 and were completed by the end of 2005. These required close coordination with operations to minimize disruptions of the normal access to the smelter and to try to reduce as much as possible the production losses. That was one of the challenges of this project.
A total of 10,800 m (35,400 ft) of HDPE & PVC pipes were installed.
A concrete batch plant that was used for the other contractors was installed. The largest concrete foundations were for the anode furnaces, casting wheel, Isasmelt and RHF’s furnaces.
A total of 20,000 m^sup 3^ (706,000 cu ft) of concrete were used on the project.
Oxygen plant No. 2 was constructed under a lump sum contract with Air Products. The capacity of the new plant is 948 t/d (1,045 stpd) cryogenic low-pressure oxygen with 95 percent purity. This plant included the installation of the largest component of the project, the cold box with dimensions of 5.5 x 5.5 x 55 m (18 x 18 x 180 ft) and a weight of 164 t (186 st). For its installation, it was necessary to use two heavy cranes, one of 1.1 kt (1,200 st) and the other of 453 t (500 st).
The new oxygen plant was commissioned during October 2006. This plant is the third largest in the world.
Acid plant No. 2 was constructed under a lump sum contract with Kvaerner Chemetics (Vancouver, Canada). The capacity of the new double contact, double absorption plant is 3.4 kt/d (3,750 stpd) of sulfuric acid, singletrain design. The gas feed design (Isasmelt + PSC) is 12.6 percent of SO^sub 2^.
The construction of the new acid plant was completed and the preoperational tests were completed during the beginning of December 2006. This plant is the fifth largest in the world.
Material handling and silica crushing area
Modifications to the existing plant were made in order to feed the new bins for the Isasmelt. Three 227 t (250 st) bins for concentrate, one 227 t (250 st) bin for silica, one 91 t (100 st) bin for limestone flux, one 91 t (100 st) bin for coal and one 91 t (100 st) bin for reverts had to be installed. A paddle mixer was also installed to blend the different components of the Isasmelt feed.
The feed preparation area, bins and conveyors and the silica crushing plant were commissioned during October 2006. The silica to be used at the Isasmelt furnace needs to have a size less than 6.35 mm (0.25 in.).
For the fire refining process, two new anode furnaces with a capacity of 363 t (400 st) per charge each, and a twin casting wheel with a capacity of 91 t/h (100 stph) were installed.This allows the smelter to produce copper anodes directly, rather than the prior practice of casting blister copper that had to be remelted at the refinery, which is located about 10 km (6.2 miles) away from the smelter.
The anode plant was installed during 2005 and commissioned in January 2006, with anode production now occurring at the smelter for the first time. Anode production has reached more than 222 kt (245,000 st).
Under the modernized scenario, the smelter will operate with four Pierce Smith converters (PSC), with three hot and one under maintenance. Only two converters will blow simultaneously. The project undertook the following modernization for the converting area:
* Re-utilization of three of the existing PSCs.
* Installation of one new PSC.
* Installation of new water-cooled hoods, spray cooling chambers and new balloon flue.
* New dampers for gas handling.
* Two new ESPs.
* Two new ID fans.
Three converters were upgraded and new hoods with a water cooled system were installed and operating. Also, a new converter was installed and is operating. For the transition period the four PSC are operating in conjunction with two other existing PSC.
The seawater supply system was commissioned in May 2006 and has a capacity of pump 15,000 m^sup 3^/h (529,717 cu ft/h) to be used at the various plant cooling systems and for feed to the desalination plants.
Two new 55 m^sup 3^/h (1,942 cu ft/h) desalination plants were installed and will supply the additional water necessary for operating the new smelter. The desalination plants were commissioned on August 2006, and are now in production.
Two new 70 MVA transformers were installed to supply the power for the modernized smelter. They are connected to the existing Enersur substation. Another six area substations were installed and are connected to the new main substation.
The new main substation has been operating since May 2006.
Process control system
The process control system of the Ilo smelter is a modern digital system for control and monitoring processes, based on digital networks and intelligent instrumentation.
It combines the strengths of the process control systems of the “Delta V” distributed control system (DCS), “Control Logix” programmable logic controllers (PLC) and field control networks (Foundation Fieldbus, Hart, Profibus DP, Controlnet, etc.). All are automation leaders in the market place.
The specific objectives of the PCS are:
* Execute sequential and regulatory control of the process.
* Diagnose, analyze and optimize the control loops and processes.
* Development of predictive maintenance activities and provide information to the existing preventive maintenance system.
* Integrate the existing “Infi 90″ DCS.
* Inform in real time the state of process variables to the plant information system.
Concentrates from the existing blending facilities will be conveyed to three concentrate storage bins. Five additional bins are provided for silica flux, limestone, coal, reverts and recycle dust.
The concentrate from the bins is fed to a common conveyor which also delivers reverts, lump coal and fluxes to a paddler mixer. Recycle dust is pneumatically conveyed to the dust bin, then to the mixer. Water is added directly into the mixer to produce a mixed feed containing about 9 to 10 percent water. The conditioned feed is fed by conveyors directly to the furnace through a feed port located in the roof of the furnace. The Isasmelt furnace is a vertical cylinder, supported on a concrete base.The steel shell is approximately 5.5 m (18 ft) inside diameter and 16-m (53-ft) high. It is lined with 450 mm (17.7 in) of chrome-magnesite refractory bricks plus a backing lining to give an approximate internal diameter of 4.4 m (14.4 ft). The furnace base is bricked to a dish shape. The Isasmelt furnace carries out the function of smelting the SPCC copper concentrate feed, which contains approximately 27 percent copper, to produce a molten copper matte containing approximately 62 percent copper.
Air, oxygen and distillate fuel are injected through a lance into the bath. The Isasmelt lance is manufactured from mild steel and stainless steel. It is about 18 m (59 ft) long with a nominal inside diameter of 450 mm (17.7 in.). Internal swirlers in the lance ensure that the lance tip is cooled by the process air so that a frozen layer of slag forms on the lance. This protects the lance from attack by the bath.
The oxygen in the process air is captured by the iron oxide contained in the slag (reacting with Fe2+ to form Fe3+), while the nitrogen component of the process air vigorously agitates the bath through buoyancy effects. The concentrates added to the bath are, thus, rapidly incorporated into the bath where they react with the excess Fe3+ ions present in the bath.
The matte and slag products from the Isasmelt furnace will be tapped into two rotary holding furnaces (RHFs) where the settling of the matte will occur. Each RHF is a horizontal cylindrical vessel, approximately 4.6 m diameter by 16 m (15 ft diameter by 52 ft) long. The steel shell is lined with refractory bricks to give an in diameter of approximately 3.6 m (12 ft).
The RHF’s are supplied with an entry port to receive the matte and slag from the Isasmelt furnace and separate tapping ports for matte and slag.The RHF is sized to allow sufficient residence time for matte prills to settle from the slag and also to allow sufficient matte storage to meet the needs of the Pierce Smith converters.
The RHF is capable of rotating away from the aisle to allow skimming of discard slag and towards the aisle to allow pouring of matte, the slag and matte ports being located on opposite sides of the RHF.
The temperature of the RHF are maintained by means of burners located in the end wall and roof of the furnace.
The modernization project construction was completed by January 2007, and the commissioning of the Isasmelt furnace started by February 2007. The Isasmelt furnace and RHF’s are installed along with ancillary equipment
The new gas treatment system will allow capturing 92 percent of the sulfur contained in the feed to the smelter after commissioning the new acid plant. This change along with the installation of the gas handling system in the PSC will contribute to decreasing the converter secondary emissions. The gas system handling was completed by November 2006.
A marine trestle was designed and is under construction. It will be 500 m (1,640 ft) in length and will accommodate ships with a capacity between 5,000 to 30,000 DWT. The main reason to add this facility to the modernized smelter was to reduce the train traffic through the city of Ilo arising from the increased production of sulfuric acid. The marine trestle is expected to be ready at the end of 2008.
Safety was the main concern from the beginning of this project. The target was to have zero lost time accidents, even considering that the project needed to be constructed in an operating smelter and with facilities reaching more than 75 m (246 ft) high. After 0.5 million manhours worked the first and only lost time accident was registered.
The safety meetings and training were reinforced and as product of the coordinated job of the project team a 9 million man hours worked without a lost time accident was obtained. This represents a Peruvian record for large industrial projects like this.
The modernized Ilo smelter is completed. It permits Southern Peru to comply with the commitment with the Peruvian government to capture 92 percent of the S02 generated at the Ilo smelter.
This brown field project had many challenges that were solved during its development and the production losses were reduced to the maximum possible.
A new Peruvian safety record for large projects like this was obtained with 9 million hours without a lost time accident.
The new anode plant has been operating since January 2006. It has produced 222 kt (245,000 st) of high quality anodes.
The startup of the new smelter was completed, area by area. This permitted the final commissioning of the Isasmelt area at the beginning of 2007.
The single Isasmelt furnace, pictured on a concrete pedestal, began smelting in 2006 at the Ilo complex in Peru.
Each anode casting wheel furnace has a capacity of 363 t (400 st) per charge. Twin casting wheels with a capacity of 91 t/h (100 stph) were also installed.
The Silica tertiary crushing plant was commissioned in October 2006.
The acid plant at the Ilo project is the fifth largest in the world.
The desalination plant provides water necessary for operating the smelter.
A 500 m (1,640 ft) marine trestle is expected to be completed in 2008.
1. Mariscal, Leopoldo, Bengoa, Jose and Suarez, Jorge (2005), Proyecto de Modernization de la Fundicion de Ilo, XXVII Mining Convention.
2. Walqui, Henry, Noriega, Carlos, Partington, Phil, Alvear, Gerardo and Arthur, Phillip (2006), “SPCC’s 1,200,000 tpa Copper ISASMELT”, Sohn Symposium.
3. Ilo Smelter Modernization Project Monthly Reports, (2003, 2004, 2005 and 2006).
Henry Walqui and Carlos Norieoa
Henry Walqui, projects assistant director, Southern Copper Corporation, Ilo, Peru, Carlos Noriega, Process Superintendant, Southern Copper Corporation, Southern Peru. Av. Caminos del Inca N^sup o^ 171 Chacariila del Estanque, Santiago deSurco, Lima, 33, e- mail HWalqui@SouthernPeru.com.pe, firstname.lastname@example.org
Copyright Society for Mining, Metallurgy, and Exploration, Inc. Nov 2007
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