Calcium Carbide in Steelmaking: Enhancing Desulfurization ... - TYWH

In the steel production process, steel melts contain a certain amount of sulfur and oxygen, which can negatively affect the steel's mechanical properties, as well as its processing capabilities and service life. Desulfurization and deoxidation are two essential steps in steelmaking, and calcium carbide, as an efficient desulfurizing and deoxidizing agent, can significantly reduce the sulfur and oxygen content in molten steel, improving steel quality.

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1.1 Desulfurization: Reducing the Impact of Sulfur on Steel Properties

Sulfur is an undesirable element in steelmaking. High sulfur content can reduce the steel's ductility, weldability, and even lead to hot shortness. Therefore, desulfurization is a crucial step in ensuring steel quality during steelmaking. Calcium carbide has a strong desulfurizing effect, reacting with sulfur in the molten steel to form calcium sulfide (CaS), which is then removed from the steel.

In the desulfurization process, calcium carbide reacts with sulfur as follows:

CaC₂ + S → CaS + C

In this reaction, calcium carbide reacts with sulfur to form calcium sulfide, which is removed via slag. The high reactivity of calcium carbide makes it an extremely effective desulfurizing agent, significantly reducing the sulfur content in molten steel and improving steel properties.

1.2 Deoxidation: Reducing the Oxygen Content in Steel

Oxygen is another major impurity in molten steel. Excessive oxygen content can increase steel brittleness and reduce its ductility and fatigue resistance. Therefore, deoxidation is an essential process in steelmaking. Calcium carbide, through a reduction reaction, effectively removes oxygen from the molten steel, producing carbon dioxide (CO₂) gas, which is then separated from the steel.

The deoxidation reaction of calcium carbide is represented by the following equation:

CaC₂ + O₂ → CaO + CO₂

In this reaction, calcium carbide reacts with oxygen in the steel to form calcium oxide (CaO) and carbon dioxide (CO₂). Calcium oxide, as deoxidation slag, is removed, while carbon dioxide is released as a gas. This deoxidation reaction significantly reduces the oxygen content in the molten steel, enhancing steel purity and quality.

The application of calcium carbide in steelmaking is not limited to its desulfurizing and deoxidizing effects. It can also optimize the desulfurization and deoxidation processes through several mechanisms, improving process efficiency and steel quality.

2.1 High Reactivity and Rapid Desulfurization and Deoxidation

Calcium carbide has strong reactivity and can quickly react with sulfur and oxygen in molten steel. Therefore, the use of calcium carbide during the smelting process can significantly shorten the desulfurization and deoxidation reaction times, improving process efficiency. The rapid reaction speed helps reduce time and energy consumption during the smelting process.

2.2 Reducing the Content of Harmful Elements in Molten Steel

In addition to desulfurization and deoxidation, calcium carbide can also effectively remove other harmful elements in molten steel, such as phosphorus and nitrogen. Excessive levels of these elements can negatively affect the overall performance of steel. During the smelting process, calcium carbide can react with other impurities to reduce their content in the molten steel, further improving the steel’s comprehensive properties.

2.3 Improving the Fluidity and Stability of Molten Steel

The addition of calcium carbide can improve the fluidity and stability of molten steel, reducing uneven reactions in the steel. During the smelting process, calcium carbide reacts with components in the molten steel to form a slag with better flow properties. Compared to other desulfurizing and deoxidizing agents, calcium carbide offers better stability for molten steel, contributing to the safety and control of the smelting process.

Acetylene is a combustible gas with a distinctive odor. It is used as a raw material for the production of several organic chemicals, as well as a fuel component in metal cutting, and oxy-acetylene welding. Today, acetylene is also used in the production of several plastics. Typically acetylene is produced by either one of the following methods:

1. 1. Initiating reaction of calcium carbide with water in the acetylene generator

1. Utilizing various types of hydrocarbons

With each method having its own advantages, the choice will entirely depend on the user. In this post, we will discuss the production of acetylene using calcium carbide in the acetylene generator.

Introduction to Acetylene Generation Process Using Calcium Carbide

In various industrial environments, acetylene generation is initiated in acetylene producing generators. These equipment are sold in various capacities from 8 m3 to over 200 m3 per hour. Calcium carbide is introduced from the top of the generator shell into the water. The chemical formula of this reaction can be expressed as:

CAC2 + 2 H2O → C2H2 + CA(OH)2

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This reaction should only be conducted under controlled conditions. The process unit should be equipped with pressure and temperature sensors, as well as non-return valves for safety purposes.

Acetylene Generator and Acetylene Production Using Calcium Carbide

Components of acetylene generation plant and their individual contribution is described here:

1. 1. Generator: Here, calcium carbide is mixed with a large quantity of water to produce acetylene gas. The generator is fitted with the following accessories:

a. Automatic control sensors

b. Feeder

c. Hopper(s)

d. Agitator

e. Arrestor

1. Condenser: It helps cool down the acetylene gas produced in the generator.

2. Ammonia Scrubber: This vessel removes ammonia from the acetylene stream before purification.

3. Medium Pressure Drier: As the name suggests, the medium pressure drier helps dry the acetylene gas. It is also used to control the moisture content of the acetylene stream into the purifier. Anhydrous calcium chloride is used for the purpose.

4. Purifier: It mainly comprises of a purifying material, which helps separate phosphine and hydrogen sulphide created during the acetylene generation.

5. Purifier Scrubber: This component keeps any purifying material from entering the compressor.

6. Compressor: Acetylene is a flammable gas. It uses a compressor for acetylene that is surrounded by water, which cools the heat of compression after each stage.

Safety Guidelines for Handling Calcium Carbide during Acetylene Generation

The following are some guidelines that should be adopted while handling calcium carbide during acetylene generation.

1. The maximum permissible size and weight of the carbide for a single charge should be matched with the equipment manufacturer’s specification.

2. Calcium carbide should be kept in air and water tight metal packages, and labelled “Calcium Carbide – Dangerous If Not Dry”.

3. Calcium carbide in drums should not exceed 250 kg. It should be stored where water cannot enter. Containers should be regularly checked to see that water has not entered.

4. Calcium carbide drums shall only be opened at the time of filling carbide to hoppers.

5. Carbide with more than 15% dust concentration shouldn’t be charged in the generator.

6. The carbide-water residue should not be discharged into the environment directly.

Best Sizes for Gas Yield of Calcium Carbide

The size of the calcium carbide is an important consideration during the production of gas. The following information will give you an idea of the best grades.

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Grade Size Quantity A Gas Yield Liter Per Kg Quantity B Cu.ff per lb. Quantity A Quantity B 15-80 311 288 4.98 4.60 7-15 301 275 4.81 4.42 4-7 287 267 4.59 4.28 2-4 273 251 4.36 4.01 1-2 257 236 4.25 3.77