Sargon Engineering

Molybdenum

molycommod
 
Sargon Engineering is well-experienced in simulating processes for the processing of molybdenite and the production of Ferromolybdenum, having performed numerous studies and process reviews for a client with molybdenite deposits.

Sargon Engineering offers the engineering services critical to the successful mobilisation of molybdenum projects, including process engineering, mechanical engineering, estimating, design & drafting. In addition we also offer project management and control services for our clients’ molybdenum projects, from concept to design phases.

Project Development

Sargon Engineering is expert at developing the following aspects of a molybdenum project:

  • Testwork management, interpretation, reporting & recommendations
  • Rudimentary process concept & flow diagram based on testwork and client objectives
  • Engineering scope and WBS
  • Design Criteria Document
  • A full process simulation model using SysCAD or METSIM
  • Mass Balance Spreadsheet & accompanying Proess Flow Diagrams
  • Equipment List with sizing & power draw data
  • Capital Cost Estimate (CAPEX) and Operating Cost Estimate (OPEX)
  • Plant & infrastructure general layouts
  • Simplified electrical diagrams
  • Motor list
  • Water balance and energy balance
  • Mass split diagram
  • Organisational Chart
  • Report of findings and recommendations

Technical Appreciation of Molybdenite Mining & Processing

Molybdenum is used for specialty steel alloys, nickel base alloys, lubricants, chemicals and electronics. The primary ore mineral is molybdenite (MoS2).

Molybdenite ore is mined in the USA, China, Chile, Peru, Canada and Russia, which together comprise over 90% of current production. It occurs in high temperature hydrothermal ore deposits, often in quartz veins and associated with porphyry copper sulphides. Other associated minerals include wolframite, scheelite, pyrite, anhydrite and fluorite.

The Henderson mine in the Colorado, USA contains the highest grade of molybdenum ore at 0.22% Mo. Other primary molybdenum producing mines can be economic at grades down to 0.05% Mo, and some of the larger producers extract molybdenum as a by-product of copper – such as Cerro Verde in Peru, and Bingham Canyon in Utah, with Mo grades down to 0.01%, or 100 parts per million.

Molybenite is a silvery metallic sulphide which is distinguished by its very soft and flaky nature. It is similar in feel and appearance to graphite, and like graphite is used as a dry lubricant.

The mineral molybdenite floats easily in ground slurry, with diesel and light oils used as collectors. Chalcopyrite (CuFeS2), if present, is depressed during molybdenite flotation by use of sodium cyanide (NaCN), whilst Chalcocite (Cu2S) depression requires sodium sulphide (Na2S). Nitrogen may be used during molybdenite flotation to prevent oxidative formation of elemental sulphur. Several cleaning stages of flotation, typically employing column cells, are used to reduce contaminant levels in the final molybdenum concentrate. Final concentrate grades are typically greater than 85% molybdenite, or ~50% Mo, with recoveries exceeding 90%. A typical molybdenite flotation flowsheet is shown by Figure 1.

A typical flowsheet for primary molybdenite extraction will usually utilise regrinding mills to ensure adequate liberation and final concentrate grades and recoveries.

When extracted as a copper by-product the flowsheet is more complicated due to the need for differential copper/molybdenum flotation, which may involve the use of Nokes reagent (Na3PO2S2) and heat. A high temperature ferric chloride leach for chalcopyrite removal has also been used. A relatively recent innovation for chalcopyrite removal is the use of Wet, High Intensity Magnetic Separation (WHIMS) to exploit the weak paramagnetic properties of some chalcopyrites.
Roasted molybdenite concentrate (tech oxide) is widely used as the reference price base for molybdenum products. The price was recently around US$32,000 per tonne. 

Figure 1. Recovery of molybdenite from Primary Orebody:
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Pressure oxidation (POX) at 230°C is an alternative to roasting molybdenite, and this route has synergies with leaching and purification of molybdenum trioxide (MoO3).  With the POX route the recovery of Rhenium is better than for roasting. The most commonly employed roaster type is the multiple hearth roaster. Roasting is carried out in a narrow temperature band of 500 to 600°C for conversion to molybdenum trioxide. Purification of molybdenum trioxide to 99.95% grade can be obtained by sublimation from a silica crucible and fume collection or by means of an alkali leach process.

Ferromolybdenum is obtained from Aluminothermic reduction of molybdenum trioxide.

Examples of Process Concept Diagrams: Molybdenite Roasting and Pressure Leaching

Figure 2: Multiple Hearth Molybdenite Roasting:
 
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Figure 3: Pressure Oxidation of Treated Concentrate:
 
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Previous Experience:

WorleyParsons / SMR Skopin Molybdenite Processing Plant

Sargon Engineering did process engineering for the Skopin molybdenite processing project ( for SMR ). Skopin is ~ 200 km south of Moscow, in Russia. This was a large-scale process undertaking, with the Skopin facility comprising some 274 items of major mechanical equipment through the process; the objective is to refine molybdenum concentrate to cinder, and then cinder to ferro-molybdenum. The work included:

  • Review and modeling of nitric acid catalysed pressure oxidation of molybdenite.
  • Process modeling of a molybdenite roasting and leaching facility.
  • Supply of Process Design Criteria, Process Flow Diagrams & Mass Balance Spreadsheet
  • Design and 3D modeling of a POX autoclave & ferro-molybdenum production line.
  • Preparation of a capital cost estimate (CAPEX) and operating cost estimate (OPEX).
  • Progress reporting & project management

 
Sargon Engineering modelled the molybdenum extraction process through the following areas:

  • Roaster Feed
  • Roaster 1
  • Roaster 2
  • Offgas Cleanup
  • Limestone Scrubbing
  • Limestone Milling
  • Concentrate Milling
  • Concentrate Preleach
  • NSC Pressure Oxidation
  • Pressure Letdown
  • Primary Neutralisation
  • Cinder Leach Stage 1
  • Cinder Leach Stage 2
  • Leach Residue Filtration
  • Floc Makeup Water System
  • Sodium Carbonate Production
  • Steam Distribution
  • Lime Slaking System
  • Condensate Return System
  • Plant and Instrument Air Distribution
  • Ferromolybdenum Production
  • Arsenic Removal
  • Thermite Furnace Offgas Scrubber
  • Concentrate Repulp
  • Autoclave Feed System
  • Process Water Acidification
  • Nitric Acid Catalysed POX
  • Pressure Letdown System
  • Scrub Liquor Collection
  • Flocculant Makeup
  • Autoclave Discharge Thickening
  • Water Distribution
  • Nitric Acid Storage & Distribution
  • Sulphuric Acid Storage & Distribution
  • Cooling Towers & Cooling Water System
  • Demin Water Distribution
  • Raw Water Distribution
  • HP Steam Distribution
  • Ammonia Storage & Distribution
  • Mo Sorption
  • Sorption Area Reagent Distribution
  • First Stage Filtration
  • Filtrate Collection & Distribution
  • Second Stage Filtration
  • OKM Production from Ammonia Salts
  • Rhenium Sorption
  • Technical Mo Trioxide Filter Feed
  • Technical Mo Trioxide Filter & Roaster
  • Technical Mo Trioxide Packaging & Dispatch


Conceptual 3D modeling for an expanded Ferromolybdenum plant:
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>> View the project summary for Skopin Molybdenite Processing Study (under our Projects section)

Molybdenite Processing Options Presentation, ALTA 2009

Sargon Lovkis gave a presentation at the May 2009 ALTA Conference in Perth, illustrating various options for the processing of molybdenite.

Download the 2009 ALTA slide presentation
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