Sulfuric Acid Regeneration
Transforming Efficiency & Sustainability
A Sulfuric Acid Plant Success Story
In 2015, P&P Industries AG became the first company to successfully develop and commission a sustainable Sulfuric Acid Regeneration (SAR) plant tailored to the needs of the petroleum industry. This groundbreaking facility transforms spent alkylation acid and waste gases into high-purity, low-carbon sulfuric acid—while producing nearly no harmful emissions such as SOx, NOx, PM2.5, or acid mist. It also eliminates the environmental challenge of landfilling spent acid solutions.
The regenerated sulfuric acid is reused in refining processes to produce high-octane fuel, enhancing fuel efficiency and supporting the production of fertilizers—further extending the environmental benefits.
Since pioneering this technology, P&P has delivered dozens of SAR units worldwide. One notable example—developed for one of the world’s largest refineries—demonstrates exceptional sustainability performance by significantly reducing sulfur dioxide emissions and generating additional revenue through the elimination of hazardous waste disposal.
The Challenge
Designing a plant to operate with near-zero emissions—despite an extremely corrosive feedstock—posed one of the most demanding engineering challenges. The process had to remove over 500 ppm of toxic metallic contaminants and other chemical impurities, while maintaining continuous, maintenance-free operation across all converter towers and equipment for an impressive four consecutive years.
Additionally, the plant needed to manage wide fluctuations in feed capacity—from 40% to 120%—without relying on external energy sources such as natural gas or fuel gas. Despite these variations, the system was required to consistently deliver high-quality, low-carbon sulfuric acid with a concentration exceeding 98% by mass.
A further challenge was the continuous generation of superheated, high-pressure steam—used for power generation—without operational interruptions. In this context, plant stability and process reliability were absolutely critical.
Getting these demanding requirements, a series of innovative process enhancements have been necessary. The result: a breakthrough solution that redefined expectations and became a game changer—for P&P Industries and its customers across the petrochemical sector.
The Solution
To meet the plant's ambitious goals, several key process optimizations and high-tech components were developed, including:
- Innovative Multi-Fuel Burner System: Designed to minimize NOx emissions, ensuring efficient combustion with low environmental impact.
- Spent Acid Decomposition: Achieved at high temperatures and low oxygen levels, eliminating the side effects of thermal NOx production.
- Heat Exchanger Protection: A blast device in the incinerator prevents fouling from the high dust load in the heat recovery system.
- Ceramic Hot Gas Filtration: Removes dust and metallic contaminants at high temperatures, ensuring a cleaner, more efficient process.
- Maximized SO2 Concentration: P&P’s unique, high-temperature, low-pressure-drop SO2 Platinum (Pt) honeycomb catalyst was installed to optimize thermal efficiency and reduce pressure losses.
- DeNOx System: Implemented to achieve the lowest possible NOx emissions, further enhancing the plant’s sustainability.
- Long-Term Operational Stability: Designed to handle capacity fluctuations (40-120%) without interruption, ensuring four years of continuous operation.
To achieve zero emissions and produce high-concentration sulfuric acid, several advanced technologies were integrated:
- High-Temperature Wet Electrostatic Precipitator (WESP): Effectively removes acid mist, achieving emissions-free operation and producing acid with concentrations up to 98.3% by mass.
- Two-Stage Conversion System: A modified double-stage wet sulfuric acid process reduces SO2 emissions to near zero.
- Molten Salt Heat Transfer System (HTS): Used to remove exothermic energy, maximizing energy efficiency and increasing plant stability. The HTS system eliminates the need for a high-pressure heat exchanger, reducing both investment and operating costs.
- SO3 Hydration: Leveraged to generate up to 25% more high-pressure superheated steam for power generation compared to a standard dry acid plant.
Fossil Fuel Elimination:
The system’s design produces low-carbon sulfuric acid without relying on fossil fuels, supporting sustainability goals.
Process Description
Approximately 10% of sulfuric acid is used as an active catalyst in the production of polymers, jet fuel, and gasoline. While the acid is not consumed in the process, its effectiveness diminishes due to contamination from hydrocarbons, metals, water, and other chemicals. To maintain the catalyst’s performance, contaminated spent acid is "bled” from the system and regenerated back with our SAR into pure, strong sulfuric acid (98% by mass) for further use.
P&P Industries AG SAR regenerates the spent sulfuric acid in several stages:
1. Oxydation and Filtration: The spent acid H₂SO₄ will be decomposed into SO₂, O₂, and H₂O in a high-temperature (1050°C) decomposition chamber. The exhaust gases from the furnace are cooled in a heat recovery system, and the impurities like ash, and soot particles are removed with the hot gas filter (HGF).
2. 1st Converter SO₂ to SO₃: The SO₂ in the exhaust gas is then further cooled and oxidized into SO₃ using a unique P&P Platinum (Pt) honeycomb catalyst. SO₃ reacts with water vapor (H₂O) to form sulfuric acid (H₂SO₄) gas.
3. 1st Condenser: Finally, the process gas is cooled to condense on the P&P glass tube heat exchanger (GTHX) and collected in the sump. To finish the process of the 1 stage the WESP removes the acid mist, achieving nearly emissions-free operation. Around 95% of the SO2 is converted into sulfuric acid.
4. Optional: A 2nd converter and a 2nd condenser as well as a 3rd converter, executed as low temperature carbon catalyst (LTCC), can achieve a conversion rate of 99,98%. Depending on the emission limits only a LTCC can be installed after 1st stage.
This innovative process efficiently regenerates sulfuric acid, ensuring high purity and effectiveness for its critical role in industrial applications.
The Impact
P&P Industries AG is the first company in Asia capable of simultaneously treating multiple types of waste gases and spent acids with an efficiency exceeding 99.98%. This achievement has positioned P&P as the leading technology provider in this specialized field, surpassing larger competitors.
The project processes:
- Acid Gases: 10,000 tons per year
- Spent Acid: 25,000 tons per year
- High-Quality H₂SO₄ Production: 40,000 tons per year
- High-Pressure Steam: With zero emissions
This advanced system delivers significant economic benefits, including energy savings (OPEX reduction), a very low pressure drop (reducing the need for power from process gas fans, OPEX reduction), the elimination of spent acid disposal (OPEX reduction), and the reuse of sulfuric acid as a valuable product (CAPEX reduction).
Key Metrics:
- Acid Production: 25-500 tons per day (TPD) from acid regeneration
- Emissions:
- Acid mist: <3.4 mg/Nm³ (down to 1 ppm possible)
- SO₂: <30 mg/Nm³ (optimized plant <10 ppm)
- NOx and dust: Often below detection limits
This solution not only provides high efficiency and low environmental impact but also drives substantial cost savings for its users.
Future Outlook & Enhanced P&P-Platinum-Catalyst-System
This success has set a new standard for larger, more ambitious projects to come. The data collected throughout the process has been thoroughly analyzed to evaluate the impact of various process changes, driving continuous improvement in both; emission reduction and acid regeneration rates.
Building on these insights, P&P’s advancements in the P&P-Platinum-Catalyst-Program further enhance the efficiency of our sulfuric acid plants, making them even more energy-efficient and environmentally friendly. With these innovations, P&P in a leading position of the industry, delivering cutting-edge solutions for the future.