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Sulfuric Acid Production Processes

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Chemical Process Technology

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Product Description

I. Current Status of Sulfuric Acid Production Processes

At present, the contact process dominates industrial sulfuric acid production, accounting for over 95% of the total output. The raw material routes are mainly divided into three types: sulfur-based acid production, pyrite-based acid production, and smelting flue gas-based acid production.

1.Sulfur-based acid production: It features mature technology, high product purity and good environmental performance, and is the preferred choice for newly built plants; however, the raw material sulfur has a high external dependence.

2.Pyrite-based acid production: Raw materials are easily available, but the process flow is long with large discharge of three wastes and high purification cost, and is being gradually replaced.

3.Smelting flue gas-based acid production: It adopts the mode of "treating waste with waste" by utilizing SO2 flue gas from non-ferrous smelting. Supported by favorable policies, its market share has continued to rise in recent years.

Industry development trends: large-scale installation, double conversion and double absorption, waste heat recovery, ultra-low emission, and intelligent operation.

 

II. Process Description (Sulfur-based Acid Production, Double Conversion & Double Absorption)

Solid sulfur is melted and filtered to remove impurities, then combusted with dry air in a sulfur furnace at high temperature of 1000–1100 ℃ to produce SO2 furnace gas. The high-temperature furnace gas recovers heat through a waste heat boiler to generate by-product steam, and is further purified and dried to remove impurities and moisture. The purified SO2 gas enters the converter and is catalytically converted into SO3 at 420–600 ℃ via "3+1" or "3+2" conversion stages with vanadium catalyst (V2O5). By adopting the double conversion and double absorption process, the total sulfur conversion rate reaches ≥99.7%.

The SO3 gas enters the absorption tower in two stages, and is counter-currently absorbed by 98% concentrated sulfuric acid to produce 98% industrial sulfuric acid or oleum. The tail gas is treated and discharged up to standard. The waste heat recovery system produces 3.8 MPa medium-pressure steam for power generation or external supply.

 

III. Process Advantages (Sulfur-based Acid Production, Double Conversion & Double Absorption)

1.Excellent product quality: The concentration of finished sulfuric acid is ≥98% with high purity and extremely low impurities, meeting the premium product standard.

2.Superior environmental performance: The sulfur utilization rate of the double conversion and double absorption process is ≥99.7%, and the SO2 concentration in tail gas is ≤50 mg/m³, which can meet emission standards with basically no pressure of solid waste and wastewater discharge.

3.High thermal energy utilization rate: The waste heat from sulfur combustion and conversion is fully recovered to produce 3.8 MPa medium-pressure steam, realizing self-sufficiency with surplus for external supply. The waste heat recovery efficiency reaches 90%~95%, which greatly reduces energy consumption per ton of acid.

4.Low operating cost: It has low raw material consumption, long catalyst service life, low system resistance and low power consumption. With a high automation level, stable operating conditions and simple operation and maintenance, the production cost per ton of acid is lower than that of the pyrite-based process.

5.Good investment economy: The process flow is compact with large-scale equipment and small floor occupation, resulting in low unit capacity investment. The plant features high operational reliability, long maintenance cycle and long continuous operation time, delivering outstanding comprehensive economic benefits.

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