Customized EPC Solutions for Sulfur-Burning Acid Plants

At Xinshidai, we specialize in delivering sulfur-burning acid plants on an EPC (Engineering, Procurement, and Construction) basis, offering a comprehensive solution for sulfuric acid production. This method, widely recognized for its efficiency and reliability, involves the combustion of elemental sulfur to produce sulfur dioxide, which is then converted into sulfur trioxide and subsequently absorbed to form sulfuric acid. By leveraging our extensive expertise and state-of-the-art technology, we ensure the seamless integration of design, procurement, and construction phases, providing our clients with a fully operational and optimized plant tailored to their specific needs.

Elemental sulfur is used as the primary raw material.

• Sulfur Combustion to Generate SO₂

Solid sulfur is conveyed via a belt conveyor to the sulfur melting tank, where steam coils heat and melt it into liquid sulfur, which is then filtered to produce clean liquid sulfur. Liquid sulfur is then sprayed into a sulfur combustion furnace and mixed with dried air for combustion, producing SO2. The chemical reaction is represented by the following equation:

S+O₂→SO₂

• Catalytic Oxidation of SO₂ to SO₃

SO₂ is oxidized to sulfur trioxide(SO₃) in the presence of a catalyst (typically vanadium pentoxide) in a 5-pass converter. The chemical reaction is represented by the following equation:

2SO₂+O₂→2SO₃

• Absorption of SO₃ Gas

The SO₃ generated by the catalytic oxidation of SO₂ reacts with water to form sulphuric acid. This reaction (absorption) takes place in the absorption towers, where the gas comes into countercurrent contact with concentrated sulphuric acid. SO₃ reacts with the water in the circulating acid to form H₂SO₄:

SO₃+H₂O→H₂SO₄

We utilize a double conversion and double absorption (DC-DA) process, implementing a "3+2" conversion flow. Initially, the furnace gas passes through the first to the third catalyst beds, where approximately 94-96% of SO₂ is converted. This gas then enters the first absorption tower, where the produced SO₃ gas is absorbed by concentrated sulfuric acid. The gas then proceeds to the fourth pass of the converter. The removal of SO₃ facilitates further conversion of SO₂. After the second-stage conversion, the total conversion rate can reach 99.874%. By employing this design, along with high-quality catalysts, and adjusting the reaction temperature through heat exchange and waste heat recovery, we achieve a high overall conversion rate.

Cost Efficiency: The sulfur-burning acid production process features a shorter flow, lower investment, and reduced overall costs.

Reliability: Controlled combustion of elemental sulfur ensures consistent product quality and reliable operation.

Flexibility: The production capacity can be easily scaled up or down to meet varying demands.

Energy Efficiency: In a typical sulfur-burning plant, heat is generated in several process units, mainly during sulfur combustion. The recovered heat is converted into steam, which is then used to generate electrical power or for other heating purposes. This heat recovery system enhances overall energy efficiency.

Environmental Impact: Sulfuric acid production from sulfur boasts a remarkably low pollution footprint. This translates to minimal waste generation across all stages of the process, as detailed below:

• Waste Residue: The process generates very little solid and liquid waste. The primary waste product is the filter cake produced by the liquid sulfur filter. This waste residue finds new life as a raw material in pyrite roasting acid plants.

• Wastewater: The main wastewater stream originates from floor washing water that becomes slightly acidic during the cleaning process in the sulfuric acid plant. This wastewater undergoes neutralization with lime followed by solid-liquid separation in a purification sedimentation tank. The resulting solid calcium sulfate becomes a valuable component in cement production, while the treated liquid is recycled for floor washing, achieving a closed-loop system with zero wastewater discharge.

• Waste Gas: The DC-DA process boasts a high conversion rate for SO₂, significantly reducing potential air emissions. For even stricter control, additional equipment like a secondary tail gas scrubber and an electrostatic demister can be implemented to further reduce emissions. With these measures, SO₂ emissions in the tail gas can be kept as low as 200mg/Nm³, and acid mist can be minimized to ≤20mg/Nm³.

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Figure 1~3. SMCO(Shituru Mining Corporation in DRC) 100kta sulfur-burning acid Plant

Figure 4~8. Tengyuan Cobalt & Copper Resources(DRC) 160kta sulfuric acid plant

Figure 9. New Minerals Investment(DRC) 100kta sulfur-burning acid plant

Figure 10~12. CMOC Group KFM 300kta sulfur-burning acid plant