Meet the king of industrial chemicals: Sulphuric acid

Sulphuric acid (H₂SO₄) is the most widely produced industrial chemical, earning its title as the "king" of industrial chemicals. In 2022 alone, global production reached approximately 260 million tons.

Production  

The Contact Process is the main industrial production method today, and involves the following key steps: 

1. Burning Sulfur: Sulfur (S) or sulfide ores such as pyrite (FeS₂) are burned in the presence of oxygen to produce sulfur dioxide (SO₂). 
2. Conversion to SO₃: The sulfur dioxide is then oxidized to sulfur trioxide (SO₃) using a vanadium pentoxide (V₂O₅) catalyst at high temperatures. 
3. Absorption in Water: The sulfur trioxide is absorbed in concentrated sulfuric acid to produce oleum (H₂S₂O₇), which is then diluted with water to obtain the desired concentration of sulphuric acid. 

Sulphuric Acid Manufacturing Process

This method produces pure sulphuric acid with a concentration of around 98% and a density of 1.84 kg/L.  
 

Applications 

Sulphuric acid is one of the most widely used chemicals in the world, with applications across different sectors, including: 

• Fertilizer Production: It is a key component in manufacturing phosphoric acid, which is used to produce phosphate fertilizers essential for agriculture. 
• Chemical Manufacturing: Sulphuric acid is used in the production of numerous chemicals, including hydrochloric acid, nitric acid, and synthetic detergents. 
• Petroleum Refining: It plays a role in refining crude oil by removing impurities and aiding in the production of high-quality fuels. 
• Battery Production: Lead-acid batteries, commonly used in vehicles and backup power systems, contain sulphuric acid as an electrolyte. 
• Textile and Dye Industry: Sulphuric acid is employed in dyeing fabrics and processing textiles. 
• Wastewater Treatment: It is used to adjust pH levels and neutralize alkaline waste.  

Cargo handling 

• Safety. Sulphuric acid is non-flammable but is extremely corrosive to skin tissue. Personal protective equipment (PPE) to be used include acid resistant splash suits, boots and gloves, safety goggles and face shield.  
• Corrosion. At concentrations above 93% and ambient temperatures, sulphuric acid can safely be carried in stainless steel. At lower concentrations and at higher temperatures it becomes corrosive to 316L and duplex steel. 
• Chartering: check specifications and steel manufacturers’ guidelines or seek advice before booking! 
• Reactivity. Sulphuric acid is very reactive and is incompatible with many cargo groups. It also reacts violently with water, which creates a lot of heat that can cause discoloration of the steel.
  • ​Discoloration is caused by the progressive thickening of an iron oxide layer at the surface of the steel. The higher the temperature, the thicker the layer and the darker the color, just like the rainbow colors on your stainless steel pots and pans. 
  • Discoloration can be removed by pickling or grinding, both of which remove a few microns of the steel.  

It is good practice to apply a nitrogen blanket during voyage and discharge of sulphuric acid to avoid ingress of moisture and subsequent discoloration.