Production Technology

The plant adopts the Double Conversion Double Absorption (DCDA) process, which is based on multiple-stage catalytic conversion and absorption. During operation, solid sulfur is first melted and purified before entering the combustion furnace. The combustion reaction produces SO₂ gas, which passes through heat recovery equipment before entering the converter.

Inside the converter, SO₂ reacts with oxygen under catalyst action to form SO₃. After two conversion stages and two absorption stages, the final acid product reaches the required concentration range. The conversion process achieves an SO₂ conversion rate of ≥99.8%, while the recovered process heat is transferred into the steam generation system.

Sulfur preparation → Sulfur combustion → SO₂ catalytic oxidation → Intermediate absorption → Secondary conversion → Final absorption

Key System Components

Sulfur Preparation System

The sulfur preparation unit provides treated liquid sulfur for the combustion process. Solid sulfur is heated until it becomes liquid and then filtered to remove impurities. The purified sulfur is maintained at a controlled temperature before being delivered to the furnace. The preparation stage ensures stable sulfur feeding and reduces impurities entering the combustion section.

System integration: Sulfur melting equipment, Filtration unit, Storage tank, Transfer pumps, Steam heating system.

Typical operating conditions: Sulfur melting temperature: 135–148℃, Heating steam pressure: 0.4–0.6MPa.

Combustion and Gas Generation System

The combustion unit converts elemental sulfur into sulfur dioxide. Liquid sulfur is sprayed into the furnace through atomization equipment and reacts with dried air (S + O₂ → SO₂). The combustion process produces high-temperature SO₂ gas with an outlet temperature of approximately 1050℃. Before entering the conversion section, the gas passes through heat recovery equipment to reduce temperature and recover thermal energy.

Catalytic Conversion System

The catalytic conversion unit is responsible for transforming SO₂ into SO₃. The system consists of converter equipment, catalyst beds, gas heat exchangers, and temperature control devices. The plant uses a four-stage catalyst arrangement with a "3+1" conversion design. Temperature regulation between catalyst stages maintains suitable reaction conditions and supports stable conversion performance (SO₂ conversion rate: ≥99.8%).

Absorption and Acid Circulation System

The absorption section completes the conversion of SO₃ into sulfuric acid. The circulating acid system controls acid concentration, circulation flow, and absorption temperature. The finished product concentration is maintained tightly at 98.1%–98.5% H₂SO₄.

Main equipment: Drying tower, Absorption towers, Acid circulation tanks, Pumps, Acid coolers.

Waste Heat Recovery System

The production process releases heat during sulfur combustion and catalytic reactions. The plant uses recovery equipment to convert this heat into usable steam, which can be deployed for sulfur melting, heating systems, and other plant utilities.

System architecture: Waste heat boiler, Steam drum, Superheater, Economizer.

Reference parameters: Steam pressure: 3.82MPa, Steam production: approximately 15t/h.

Process Control and Automation

The plant integrates automatic monitoring and control systems to manage production conditions. The control system monitors gas temperature, acid concentration, pressure conditions, liquid level, and equipment operating status. Automatic regulation of pumps, valves, and process parameters helps maintain stable operation during continuous production.

The electrical and instrumentation system includes: Distributed control system (DCS), Field instruments, Motor control equipment, Safety monitoring devices.

Frequently Asked Questions

1. What raw materials are required for this plant?

The primary raw material is elemental sulfur. The recommended sulfur specification includes sulfur content ≥99.9%, ash ≤0.001%, moisture ≤0.01%, and carbon ≤0.03%.

2. What production process is used?

The plant uses the sulfur combustion route with DCDA technology, including sulfur oxidation, catalytic conversion, and two-stage absorption.

3. What capacity can the plant achieve?

The reference design provides a production capacity of 100,000 tons per year. The capacity can be adjusted according to project requirements.

4. How is energy recovered during production?

Heat generated from combustion and conversion reactions is recovered through boilers and heat exchangers to produce approximately 3.82MPa steam.

5. What systems are included in a complete project?

A complete system includes process equipment, acid circulation units, heat recovery equipment, automation systems, utilities, and environmental control facilities.