Classification and Production of Non-Ferrous Metals

Posted on May 14, 2024 in Chemistry

Classification of Non-Ferrous Metals by Density

Non-ferrous metals are classified into three categories based on their density:

Heavy

Density is equal to or greater than 5 kg/dm3.

Light

Density is between 2 and 5 kg/dm3.

Ultralight

Density is less than 2 kg/dm3.

Tin

Pure tin has a very bright color. At room temperature, it oxidizes and loses its brilliance. It is very pliable and soft at room temperature, but weak and brittle when hot. Below -18°C, it begins to decompose and become gray. This is called “tin pest.” When bent, tin emits a characteristic creaking sound known as the “tin cry.”

Tin Alloys

  • Bronze: An alloy of copper and tin.
  • Soft Solder: A lead-tin alloy.
  • Low Melting Point Alloys: Darcet, Cerrolow.

Tin Procurement Process

  1. Cassiterite: Tin ore is crushed and milled.
  2. Decantation: The milled ore is placed in water. Tin ore settles to the bottom and is separated from the gangue.
  3. Reduction: The tin ore is introduced into a reverberatory furnace where reduction occurs, depositing tin at the bottom and scum at the top.
  4. Electrolytic Refining: To obtain tin with 99% purity, an electrolytic process is used.

Copper

Copper is very ductile and malleable, with high electrical and thermal conductivity.

Copper Production

Dry Method

Used when the copper content exceeds 10%.

  1. Copper ore is crushed and then pulverized in a ball mill.
  2. The mineral powder is mixed with water to separate the ore from the gangue through flotation.
  3. The concentrated ore is placed in a furnace for partial oxidation.
  4. The partially oxidized ore is transferred to a reverberatory furnace where it melts and forms slag.
  5. Flux is added to the molten mixture.
  6. The resulting copper, called “raw copper,” has a purity of around 99%.

Wet (Electrolytic Refining) Method

Used when the copper content is less than 10%.

  1. The ore is crushed and treated with sulfuric acid.
  2. Copper is extracted through electrolysis.

Copper Alloys

  • Bronze: Copper and tin.
  • Brass:
    • Regular: Copper and zinc.
    • Special: Copper, zinc, and other chemical elements.
  • Alpaca (Cuproaluminum): Copper, nickel, and aluminum.
  • Copper-Nickel: Copper and nickel.
  • Nickel Silver: Copper, zinc, and nickel.

Zinc

Zinc is highly resistant to oxidation and corrosion in air and water, but less resistant to acids and salts. It has a high coefficient of thermal expansion and is brittle at room temperature. However, between 100 and 150°C, it becomes very malleable.

Commercial Presentations of Zinc

Zinc Alloys

  • Brasses: Cheaper than tin bronzes, zinc brasses are often used as a substitute.
  • Alpaca: Used for jewelry cases.
  • Zamak: Used for parts requiring high precision and surface quality.

Pure Zinc

  • Sheets: Used for roofing, gutters, and eaves.
  • Covering of Piles: Protects piles from corrosion.

Zinc Coatings

  • Electrolytic Galvanizing: Coating parts with a very thin layer of zinc.
  • Hot-Dip Galvanizing: Immersing the piece in a bath of molten zinc. The zinc adheres to the piece as it cools, providing protection.
  • Metal Spraying: Projecting tiny metallic zinc particles mixed with paint onto the piece.
  • Sherardizing: Coating a steel piece with zinc powder and placing it in an oven. The zinc diffuses into the steel, providing protection.

Zinc Oxide

Used in sunscreens, deodorants, dyes, glues, and preservatives.

Lead

Lead is very malleable and soft, with a grayish-white color. It is very bright when freshly cut but easily oxidizes, forming a basic carbonate layer that protects it. Lead resists the attack of hydrochloric and sulfuric acid, but reacts with nitric acid, sulfur vapor, and alkalis.

Applications of Lead

Pure Lead

  • Lead oxide
  • Red lead paint
  • Pipes
  • Batteries

Lead Alloys

  • Coating for brazing
  • Lead-tin alloys

Lead Procurement and Enrichment

  1. Galena: Lead ore is crushed and ground.
  2. Flotation: The gangue is separated from the ore by flotation.
  3. Sulfide Oxidation: All lead sulfides (PbS) are roasted to convert them into oxides by adding silica and lime. This process yields lead monoxide (PbO).
  4. Reduction: Reduction is performed in a muffle furnace using coke and limestone. The resulting lead is called “bullion lead.”
  5. Refining of Lead: This process involves two phases:
    1. Separation of other metals.
    2. Electrolytic refining.

Other Heavy Non-Ferrous Metals

Chromium

Chromium is grayish, hard, and very brittle. It resists oxidation and corrosion. It is used as polished chrome for decorative objects, hard chrome for stainless steels and tool steels.

Nickel

Nickel has a bright silver color and can be polished. It is magnetic and resistant to oxidation and corrosion. It is used to make stainless steel, equipment for the chemical industry, and metal coatings.

Tungsten

Tungsten has a high melting point and is used for incandescent bulb filaments and manufacturing cutting tools for machines. It has similar properties to nickel.

Cobalt

Cobalt is magnetic and is used to harden steel for tools. It is also a component in the manufacture of hard metal cutting tools.

Aluminum

Aluminum is lightweight and resistant to air corrosion. It is a good conductor of heat and electricity, as well as malleable and ductile.

Aluminum Obtaining: Bayer Process

  1. Bauxite ore is transported from the mine to the processing plant.
  2. The ore is crushed and ground into powder.
  3. The powder is stored in silos until it is needed.
  4. Bauxite powder, caustic soda, lime, and hot water are mixed together in a mixer. The bauxite dissolves in the soda.
  5. Residues are separated in a decanter.
  6. The solution is cooled in a heat exchanger, and water is added.
  7. A filter separates the aluminum from the soda.
  8. The aluminum is heated to about 1200°C in an oven to remove moisture.
  9. The aluminum is cooled to room temperature in a refrigerator.
  10. The aluminum is dissolved in molten cryolite at a temperature of 1000°C.
  11. The material is subjected to a process that breaks it down.
  12. Electrolysis of aluminum is performed using oxygen.

Aluminum Alloys

  • Aluminum + Copper: Used for pans, car tires, and bicycle parts.
  • Aluminum + Magnesium: Used in aeronautical and automotive applications.
  • Aluminum + Copper + Silicon: Used for injection molding parts.
  • Aluminum + Nickel + Cobalt: Used for powerful permanent magnets.

Pure Aluminum

Mixed with paint, pure aluminum protects surfaces from the elements.

Titanium

Titanium has a silver-white finish and resists corrosion and oxidation better than stainless steel. It has similar mechanical properties to stainless steel, and in some cases, even higher.

Titanium Obtaining: Kroll Process

  1. Chlorination: Titanium ore is heated to red-hot. Carbon is added, and then chlorine is circulated through the entire mass. This process yields titanium tetrachloride (TiCl4).
  2. Reduction: The TiCl4 compound is introduced into a furnace at 800°C. An inert gas and magnesium are then introduced. This process forms titanium sponge.
  3. Melting: The sponge is introduced into an electric oven, and flux is added. The result is pure titanium.

Titanium Applications

Titanium is used in the manufacture of machine elements and structures in aerospace applications, including planes, rockets, missiles, space shuttles, and communication satellites.

Magnesium

Magnesium is found in carnallite, dolomite, and magnetite. It is highly flammable in liquid or powder form. It has a white color and is malleable and ductile. It is more resistant than aluminum and is used in aeronautical applications.

Magnesium Obtaining

Magnesium Electrolysis

Magnesium chloride (carnallite) is electrolyzed. Magnesium rises to the surface because it has a lower density than the electrolyte. The magnesium acts as a cathode and is reduced.

Reduction of Carbonates

Dolomite and magnetite are reduced by introducing the ore into an electric oven with added flux to eliminate oxygen.

Magnesium Applications

Magnesium Alloys

  • Magnam: Magnesium + Manganese + Zinc. Used for forging.
  • Magzine: Magnesium + Zinc. Used for casting.
  • Magal: Magnesium + Aluminum. Used for casting.
  • Fumagcin (Fumagal): Magnesium + Aluminum. Used for manufacturing.

Pure Magnesium

Used in pyrotechnics and as a flux in steel foundries.

Environmental Impact of Heavy Metals

Emissions

Heavy metal production releases carcinogenic gases, dust, and hydrogen gas. These emissions should be controlled to minimize environmental impact.

Factory Location

Factories should be located away from residential areas to reduce the impact of emissions on human health.

Personal Protective Equipment

Workers should wear masks and other protective equipment to minimize exposure to harmful substances.

Sewage

Wastewater from washing and stripping of metals should be treated to remove heavy metal sludge by neutralizing chemicals before being discharged.

Noise Pollution

controlled facilities and equipment, aislamientoexterior if the level is above 80 decivelos use protective auditiovs