SAR Technology for a Newly Constructed Sulfuric Acid Manufacturing Plant
Date Published: December 12, 2025
Test Method and Process
The closed-loop production process for electronic-grade sulfuric acid is shown in Figure 1 and consists of the following five stages:
1. Decomposition
After receipt, sulfur and sulfuric acid are stored in separate tanks. The sulfuric acid is first routed to a closed blending tank, where its concentration is reconfirmed and the feed rate is adjusted. The two feedstocks are then conveyed by pipeline to the decomposition furnace. Natural gas is used as the fuel to heat the furnace to nearly 1,000°C, where the sulfur and sulfuric acid undergo decomposition and combustion reactions to form sulfur dioxide gas. The process gas then passes through a waste-heat boiler recovery system. Recovered process heat is used to generate steam for the sulfuric acid purification equipment and to provide pipeline heat tracing at the sulfur storage tank to prevent crystallization.
2. Purification
This stage performs two functions:
(1) Quench scrubbing:After leaving the waste-heat boiler recovery system, the process gas is saturated with weak acid and cooled from approximately 300°C to about 80°C. Water washing and condensation are used to remove impurities from the gas, including some solid contaminants.
(2) Flue-gas cooling:Excess water vapor is condensed using recirculating cooling water as the cooling medium.
3. Conversion
The purified process gas is sent to a converter containing a vanadium pentoxide catalyst, where sulfur dioxide is converted into sulfur trioxide.
4. Absorption
The sulfur trioxide-containing gas is transferred to an absorption tower, where it is absorbed by sulfuric acid and water to produce oleum. The gas is then treated in a washing absorption tower, and concentrated sulfuric acid is produced for shipment.
5. Semiconductor-Grade Production Process
The oleum produced in the absorption stage undergoes membrane distillation to generate high-purity sulfur trioxide gas free of metal ions.
The diluted sulfur trioxide gas is then mixed with high-purity dilute sulfuric acid. Solid impurities are removed by filtration to produce semiconductor-grade sulfuric acid.
Test Results
According to the design specifications, the plant has an annual production capacity of 24,000 metric tons of electronic-grade sulfuric acid and can process 35,000 metric tons of spent acid at a concentration of 70%.
Based on trial production results from the first half of 2025, the plant produced 64.7 metric tons per day of electronic-grade sulfuric acid at a concentration of 98.5%, equivalent to an annual production volume of 23,615 metric tons. The plant can process 33,230 metric tons of spent acid at a concentration of 70% per year.
The estimated design and equipment cost is approximately NT$1 billion. Operating costs vary depending on the operating mode.
