Study on humidity compensation model of magnesium hydroxide desulfurization efficiency in high humidity flue gas treatment
I. Dual action mechanism of humidity on desulfurization efficiency
In high humidity flue gas treatment scenarios such as coal-fired power plants and steel plants, flue gas relative humidity (RH) is a key factor affecting the efficiency of magnesium hydroxide desulfurizer. Studies have shown that flue gas humidity affects the desulfurization reaction through two pathways:
Molecular diffusion acceleration: Water molecules form a liquid film in the flue gas, promoting the mass transfer process of SO₂ from the gas phase to the liquid phase. When RH increases from 30% to 60%, the dissolution rate of SO₂ can be increased by 2.3 times.
Reaction interface activation: High humidity environment promotes the formation of a dynamic hydration layer on the surface of magnesium hydroxide particles, increasing the effective reaction area. Experimental data show that for every 10% increase in RH, the specific surface area utilization rate of magnesium hydroxide increases by 8%-12%.
However, excessive humidity (such as RH>70%) will cause the viscosity of the desulfurization slurry to increase, causing the risk of scaling on the inner wall of the tower. The research on web page 1 pointed out that calcium-based desulfurizers achieve optimal efficiency at RH=45%, but magnesium hydroxide can increase the critical humidity threshold to RH=60%-65%56 due to its higher solubility (more than 100 times higher than calcium-based). This feature makes magnesium-based desulfurizers more suitable for high-humidity flue gas environments.
2. Construction and verification of humidity compensation model
Based on the nonlinear relationship between flue gas humidity and desulfurization efficiency, the research team proposed a dynamic humidity compensation model (DHCM), the core formula of which is:
η = η₀ + k₁·ln(RH) - k₂·(RH/RH₀)²
where η is the real-time desulfurization efficiency, η₀ is the benchmark efficiency (efficiency at RH=40%), RH₀ is the critical humidity for scaling (set to 65%), and k₁ and k₂ are compensation coefficients.
The model achieves dynamic control through the following technologies:
Online monitoring system: high-precision temperature and humidity sensors are deployed at the inlet, reaction zone and outlet of the desulfurization tower to collect data such as RH and SO₂ concentration in real time.
Feedback adjustment module: automatically adjust two key parameters according to the model calculation results:
Slurry injection volume: when RH＞55%, the injection volume decreases by 8%-10% for every 5% increase in humidity to avoid oversaturation and scaling
pH compensation: by adjusting the amount of magnesium hydroxide slurry, the pH of the reaction zone is stabilized at 5.8-6.2 to offset the H⁺ concentration fluctuation caused by high humidity
Industrial verification data show that after applying DHCM, the desulfurization efficiency of a 600MW unit under RH=75% conditions increased from 92.3% to 96.8%, and the scaling cycle in the tower was extended to more than 1200 hours.
3. Process optimization strategy under high humidity scenario
For the flue gas characteristics in different humidity ranges, it is recommended to adopt a graded treatment scheme:
1. Medium and high humidity range (RH 40%-65%)
Enhanced mass transfer design: Use swirl atomization nozzle to control the slurry droplet size to 50-80μm and increase the gas-liquid contact area
Gradient oxidation control: Add a porous aeration device at the rear section of the desulfurization tower to increase the oxidation rate of magnesium sulfite to 99.5% and avoid product deposition
2. Ultra-high humidity range (RH＞65%)
Pre-drying module: Install a flue gas condenser at the front end of the desulfurization tower to reduce the RH to 55%-60%, and recover waste heat for slurry heating
Anti-scaling additive: Add 0.05%-0.1% sodium polyacrylate dispersant to reduce the slurry viscosity by 30%-40%
IV. Technical and economic performance and market application prospects
The application of humidity compensation model significantly reduces the treatment cost of high-humidity flue gas:
Energy consumption optimization: measured data of a steel plant It shows that when RH increases from 50% to 70%, the power consumption of the traditional process increases by 18%, while the power consumption increases by only 7% after adopting DHCM
Byproduct value-added: The compensation model makes the purity of magnesium sulfate crystals reach 98.5%, which can be directly used in the production of high-end water-soluble fertilizers, with a premium of 200-300 yuan/ton over traditional byproducts
It is predicted that by 2028, the global high-humidity flue gas treatment market will exceed US$8 billion, of which magnesium hydroxide desulfurization devices equipped with intelligent humidity compensation systems will account for 45%. This technological breakthrough not only solves the problem of efficiency attenuation caused by humidity fluctuations, but also promotes the upgrading of environmental protection equipment to intelligent and adaptive directions.
V. Future research directions
Multi-parameter coupling model: Integrate variables such as flue gas temperature, flow rate, and particle concentration to build a more accurate desulfurization efficiency prediction system
Development of nano-scale desulfurizer: Prepare 20-50nm magnesium hydroxide particles through surface modification, so that they still maintain more than 90% activity when RH＞80%
Digital twin application: Establish a virtual desulfurization tower based on the industrial Internet of Things to achieve real-time simulation and optimization of humidity compensation parameters
This series of technological innovations will promote the full popularization of magnesium hydroxide desulfurization technology in high humidity scenarios and provide better solutions for industrial flue gas treatment and resource utilization.