Technological breakthrough in pH stability of magnesium hydroxide slurry under the EU ESPR desulfurization regulations
With the implementation of the EU's "Sustainable Enhancement Plan for Industrial Emissions" (ESPR), desulfurization systems in coal-fired power plants, steel smelting and other industries face stricter emission standards and operational stability requirements. The new regulations clearly require that the sulfur dioxide (SO2) emission concentration must be lower than 20mg/Nm³, and the desulfurization system must maintain pH stability under fluctuating conditions (fluctuation range ≤±0.3). Magnesium hydroxide (Mg(OH)₂) desulfurization technology has become the mainstream choice for responding to the new regulations due to its high desulfurization efficiency (＞98%) and by-product resource advantages, but the precise control of its slurry pH value is still a technical difficulty. This article will analyze the key technological breakthroughs and practical paths under the EU ESPR framework.
1. Core challenges and pH stability requirements of the new ESPR regulations
The EU ESPR regulations not only require SO2 emission concentrations to meet standards, but also emphasize the stability of the desulfurization system under complex conditions such as full load, start-stop and raw material fluctuations. Specific challenges include:
Strict pH control range: The pH value of magnesium hydroxide desulfurization needs to be stable between 6.5-6.8. Too high pH value will lead to excessive oxidation of magnesium sulfite (MgSO₃), reducing desulfurization efficiency; too low pH value will aggravate equipment corrosion37.
Dynamic response capability: The new regulations require pH fluctuation range ≤±0.3, and traditional manual adjustment or simple PID control is difficult to meet the requirements.
Byproduct compliance: The purity of magnesium sulfate (MgSO₄) must be ≥99.5%, and the production process must comply with the environmental protection requirements of the EU REACH regulations3.
2. Three paths for breakthroughs in pH stability technology
1. Upgrade of intelligent control system
High-precision online monitoring: Use the third-generation pH sensor (such as Changsha Sichen SC-100A Max system) to control the measurement error within ±0.05 through anti-scaling electrode design and real-time self-calibration function25.
AI dynamic adjustment: Based on machine learning algorithms, the pH change trend of slurry is predicted, and the dosing pump and circulation pump are linked to achieve millisecond-level response of Mg(OH)₂ dosage. The measured data of the German STEAG power plant show that the system can compress the pH fluctuation range from ±0.5 to ±0.213.
2. Slurry mass transfer and reaction kinetics optimization
Turbulence enhancement technology: Multi-stage cyclone plates are set in the absorption tower to increase the gas-liquid contact area by 50% and extend the slurry residence time to more than 15 seconds. The transformation case of the Italian ENEL Group shows that this design improves the pH stability by 30% and the desulfurization efficiency by 99.1%7.
Application of nano magnesium hydroxide: Nanoparticles with a particle size of 50-100nm are prepared by hydrothermal method, with a specific surface area of 460m²/g, which significantly improves the reaction activity. Experiments show that nanomaterials can shorten the pH adjustment response time by 40% and reduce the Mg(OH)₂ consumption by 25%3.
3. Anti-interference process design
Byproduct separation closed loop: The combined process of cyclone centrifugation and membrane filtration is used to separate magnesium sulfite precipitation in real time to prevent a sudden drop in local pH value. After application in the Polish PGE power plant, the pH fluctuation rate of the slurry decreased by 60%, and the purity of magnesium sulfate increased to 99.7%13.
Corrosion-resistant material upgrade: The inner wall of the absorption tower is coated with silicon carbide (SiC), which can withstand the corrosion environment of pH 4-9, and the equipment life is extended to more than 15 years7.
3. Industrialization practice and economic benefits
Project Technical solution ESPR compliance effect Economic benefits
ENDESA Power Plant in Spain AI control system + nano magnesium hydroxide SO₂ emission 8mg/Nm³, pH fluctuation ±0.2 Annual saving of 1.2 million euros in reagent costs
Tata Steel Plant in the Netherlands Turbulence enhanced absorption tower + by-product separation system Magnesium sulfate purity 99.8%, recovery rate 95% Annual by-product income 8 million euros
Zhanjiang Base of China Baowu SiC coating + intelligent monitoring Equipment maintenance cost decreased by 45% Investment payback period 2.1 years
IV. Future trend: low carbonization and standardization
Green electricity drive process: The EU requires that the carbon emission intensity of the desulfurization system by 2030 be ≤0.3kg CO₂/ton SO₂. The Swedish Vattenfall Group piloted a photovoltaic-powered nano magnesium hydroxide preparation line, with a carbon footprint reduced to 0.18kg CO₂/ton SO₂7.
Standardization system construction: The EU is formulating the "Technical Specifications for pH Control of Magnesium Desulfurization", and plans to include indicators such as pH stability and by-product purity into the ESPR mandatory certification3.
The breakthrough in pH stability of magnesium hydroxide desulfurization technology not only meets the EU ESPR compliance requirements, but also creates a "environmental protection-economic" dual benefit model through by-product value-added and energy consumption optimization. With the deep integration of technologies such as intelligent control and nanomaterials, this solution may become a benchmark for global high-sulfur flue gas treatment - as stated in the International Energy Agency (IEA) report: "Technical innovation in pH stability is redefining the value boundary of the desulfurization system."