Aluminum is a crucial part of modern life. Many of the products we use daily wouldn’t be possible without this lightweight, strong, corrosion-resistant, and recyclable metal.
However, aluminum can’t be made without two essential raw materials, one of which is calcined petroleum coke (CPC).
SINOMENCO: Your Reliable CPC Supplier
SINOMENCO Industrial Material Co., Ltd. is the top global supplier of CPC, which is necessary for creating the anodes used in the electrolytic process to produce primary aluminum. We recognize how important our raw materials are to aluminum production, and we work closely with smelters around the world to ensure they have a steady supply of high-quality CPC. This is crucial because any interruptions in supply or variations in quality can disrupt aluminum smelting operations. If these issues arise, they could threaten the very existence of a smelter. With our resources, diverse production facilities, expertise, and commitment, we are equipped to tackle these challenges and support aluminum producers in meeting current demands and exploring new opportunities.
The Smelting Process
Aluminum is produced through the Hall-Héroult electrolytic process. In this method, alumina (Al2O3) powder is mixed into a molten bath of sodium aluminum fluoride, known as cryolite. Modern cells operate at temperatures around 950-960˚C (about 1,740-1,760˚F). An electrical current flows between carbon anodes and a carbon cathode in the cell, reducing alumina to aluminum metal, which collects on the cathode surface. During this process, carbon anodes are consumed, producing CO2 gas. The basic chemical reaction is:
2 Al2O3+3C→4Al+3CO2
In a typical electrolysis line, or “potline,” cells are connected in series, and a high-amperage DC current drives the electrolysis reaction. Modern cells operate at currents between 200 and 500 kA, with higher amperage cells currently being developed. These cells function at voltages of 3.8 to 4.5V, and it generally takes about 12.5 to 14 DC kWh of energy to produce 1 kg of aluminum. Since aluminum smelting is energy-intensive, having access to affordable electricity is essential for cost-effective production.
Producing Carbon Anodes
Carbon anodes are vital for aluminum production. The anodes used in the Hall-Héroult process are made from CPC. Most smelters have their own carbon plants to produce anodes, while a few standalone plants supply pre-baked anodes to those without their own facilities or to those facing production shortfalls or maintenance shutdowns.
Pre-baked carbon anodes made from CPC are essential for aluminum production. Additionally, spent anodes (often called “butts”) are included in the anode recipe, which typically consists of 67% CPC, 20% butts, and 13% CTP. First, green anodes are produced and then baked in large furnaces until they reach a final temperature of about 1,150˚C (2,100˚F). After baking, they are rodded and placed in electrolysis cells. Since anodes are consumed during the smelting process, they need to be replaced every 20 to 30 days, depending on the cell size and design.
The quality of CPC directly affects the quality and performance of the anodes. Therefore, smelters set strict quality standards for factors like sulfur and trace metal impurities (including vanadium, nickel, calcium, iron, silicon, and sodium). The physical properties of CPC, such as bulk density, real density, and particle size, are also important in anode production. CPC with a sponge coke structure is preferred over one with a shot coke structure due to its lower thermal expansion coefficient.
A modern smelter that produces 300,000 metric tons of aluminum each year needs to make about 500 anodes daily. This makes consistent CPC quality from shipment to shipment extremely important. Many green petroleum cokes sold in the fuel market are not suitable for making anodes because they often have high impurity levels and undesirable structures. This version maintains the original meaning while using simpler language and a different structure for better readability.