Calcium Carbide in Industrial Desulfurization: Operational Methods

Calcium carbide (CaC₂) is an effective desulfurizing agent widely used in steel production. Excess sulfur content in molten steel can degrade the steel's ductility and durability, making sulfur control a key step in improving steel quality. Calcium carbide reacts with sulfur in the molten steel to form calcium sulfide (CaS), thereby achieving desulfurization. This article will discuss the desulfurization mechanism of calcium carbide and explain two primary operational methods: the stirring method and the blowing method.

Desulfurization Mechanism of Calcium Carbide

Calcium carbide is a highly effective desulfurizing agent, and its desulfurization mechanism is based on the following chemical reaction:

CaC₂ + S → CaS + C

At high temperatures in the molten steel, calcium carbide reacts with sulfur to form calcium sulfide (CaS). Due to its density, CaS rises to the surface of the molten steel, where it can be easily removed as slag. The high reactivity and moderate cost of calcium carbide make it a commonly used desulfurizing agent in steel plants.

Main Methods of Desulfurization Using Calcium Carbide: Stirring Method and Blowing Method

In steelmaking desulfurization processes, two common methods of using calcium carbide are the stirring method and the blowing method. Each method has its unique characteristics and is suited for different production needs.

The stirring method involves adding calcium carbide to the molten steel and mechanically or gas-agitated mixing to ensure thorough contact between calcium carbide and the steel, facilitating sulfur removal. The steps are as follows:

Calcium Carbide Addition: The appropriate amount of calcium carbide desulfurizer is directly added to the molten steel. The particle size of calcium carbide is generally between 0.5mm and 1.5mm to ensure a rapid reaction and effective desulfurization.

Stirring Method: The stirring can be achieved through mechanical stirring or gas (such as argon) agitation. Mechanical stirring uses equipment to directly agitate the molten steel, increasing the contact area between calcium carbide and sulfur. Argon gas stirring distributes calcium carbide evenly while preventing oxidation of the steel.

Reaction Time: Typically, the stirring time is between 5 to 15 minutes, depending on the sulfur content in the molten steel and the amount of desulfurizing agent used.

Advantages of the Stirring Method: This method is relatively simple to operate and is suitable for desulfurizing small to medium batches of molten steel. The cost of mechanical stirring equipment is also relatively low.

The blowing method uses high-pressure injection equipment to spray calcium carbide into the molten steel, allowing it to disperse rapidly and react fully with sulfur. The main steps are as follows:

Equipment Preparation: The blowing method requires specialized injection equipment to inject calcium carbide into the molten steel under high pressure. The equipment typically includes a blowing gun and gases such as argon or nitrogen.

Calcium Carbide Injection: Calcium carbide is evenly sprayed into the molten steel through the blowing gun, ensuring that it mixes quickly and reacts with sulfur in the steel.

Injection Depth: The blowing method is suitable for deep desulfurization of high-sulfur molten steel. The desulfurizer reaches the deeper layers of the steel, ensuring a uniform reaction.

Advantages of the Blowing Method: This method can quickly complete desulfurization and is suitable for large-scale production with high sulfur content in the steel. It offers higher reaction efficiency and is ideal for modern steel mills that require high productivity.

Calcium carbide plays a significant role in industrial desulfurization, with two primary methods: the stirring method and the blowing method, each tailored to different production requirements. The stirring method is suitable for small to medium batches of steel, while the blowing method is more appropriate for large-scale production. By choosing the appropriate desulfurization method, strictly controlling the operation steps, and complying with environmental regulations, steel plants can reduce sulfur content in molten steel and improve steel quality. The widespread use of calcium carbide desulfurization not only optimizes production processes but also meets the dual demands of environmental protection and cost control.