Particle size distribution of magnesium hydroxide desulfurizer: the efficiency code of 200 mesh sieve residue
1. Efficiency logic of particle size distribution
In the field of flue gas desulfurization, the particle size distribution of magnesium hydroxide desulfurizer directly affects its contact efficiency with pollutants, and the 200 mesh sieve residue (particle size of about 75μm) is a key control indicator that determines the exposure degree of active sites and the reaction kinetic boundary. The specific surface area and pore structure of magnesium hydroxide particles show a nonlinear relationship with particle size changes - when the 200 mesh sieve residue is too high, the proportion of coarse particles increases, resulting in a sharp decrease in the effective reaction interface; on the contrary, although too low a sieve residue increases the proportion of fine particles, it may cause systemic problems such as agglomeration and blockage.
Taking the measured data of a coking plant as an example, when the 200 mesh sieve residue dropped from 25% to 8%, the desulfurization efficiency increased by 12%, but the blockage rate of the slurry circulation pump increased by 40% at the same time. This reveals the core contradiction of particle size optimization: it is necessary to increase the reaction activity through fine particles, but also to avoid the engineering stability risks brought by micronization.
2. Triple Action Mechanism of 200-mesh Screen Residue
1. Critical Transition of Specific Surface Area
The specific surface area of magnesium hydroxide particles increases exponentially as the particle size decreases. When the 200-mesh screen residue is controlled at 10%-15%, the particle size is mainly distributed in the range of 45-75μm, and the specific surface area reaches the optimal balance point (about 15-20m²/g). Within this range, the particles can be fully dispersed to form a porous structure and avoid irreversible agglomeration of nano-particles due to van der Waals forces. A comparative test of a thermal power plant showed that the sulfur capacity in this range is 60% higher than that of the coarse particle system and 20% higher than that of the ultrafine system (screen residue <5%).
2. Dynamic Regulation of Slurry Rheology
The 200-mesh screen residue directly affects the thixotropic properties of the desulfurization slurry. When the screen residue is higher than 20%, the sedimentation rate of coarse particles accelerates, frequent stirring is required to maintain the suspension state, and energy consumption increases; when it is lower than 10%, the slurry exhibits pseudoplastic fluid characteristics, and the pipeline transportation resistance surges. The use of a laser particle size analyzer to monitor and dynamically adjust the screen residue in real time can stabilize the slurry viscosity in the optimal rheological window of 200-500mPa·s.
3. Time and space matching of reaction paths
The residence time of flue gas in the desulfurization tower is usually 3-5 seconds, and the 200-mesh screen residue determines the dissolution-reaction synergistic efficiency of magnesium hydroxide particles. Coarse particles (screen residue > 20%) have a slow dissolution rate and are prone to form unreacted core structures, resulting in a desulfurizer utilization rate of less than 60%; while the optimized particles can complete surface dissolution and ion diffusion within 2 seconds, and the utilization rate is increased to more than 85%.
3. Key technical paths for engineering optimization
1. Innovation of graded grinding process
Adopt the combined process of "vertical mill + airflow classification" to achieve precise control of particle size:
The first-level vertical mill crushes the raw materials to 15%-20% of the 200-mesh sieve residue;
The second-level airflow classifier separates ultrafine powders through a centrifugal field and stabilizes the sieve residue in the target range;
The simultaneous addition of surface modifiers (such as silane coupling agents) inhibits the agglomeration of fine particles. After the transformation of a steel enterprise, the energy consumption per ton of desulfurizer was reduced by 30%, and the fluctuation range of sieve residue was narrowed from ±5% to ±1.5%.
2. Online monitoring and intelligent control
Laser particle size analyzers are deployed at the inlet and outlet of the desulfurization tower to feed back sieve residue data to the DCS system in real time:
When the sieve residue exceeds the standard, the grinding machine speed and the opening of the grading valve are automatically adjusted;
Combined with the change of flue gas SO₂ concentration, the optimal particle size distribution curve is dynamically matched. In one case, the system reduced the standard deviation of desulfurization efficiency from 1.2% to 0.3%.
3. Design of composite particle size system
Construct a gradient structure of "coarse particle skeleton + fine particle active layer":
15% coarse particles with 200 mesh sieve residue are used as a supporting skeleton to maintain the stability of the slurry;
Add 5%-8% of 400 mesh ultrafine particles (sieve residue <5%) as a reaction enhancer;
Gradient distribution of particle size is achieved through electrostatic self-assembly technology. After the scheme is applied in the ship desulfurization system, the sieve residue is controlled within the safety threshold and the sulfur capacity is increased by 25%.
IV. Differentiation strategy for application scenarios
1. High sulfur flue gas scenario
For steel sintering flue gas with SO₂ concentration > 5000mg/Nm³:
Reduce the 200 mesh sieve residue to 8%-12% to increase the initial reaction rate;
Equipped with a high-pressure atomizing spray gun to quickly disperse fine particles. The actual sulfur capacity of a steel plant reached 1.2g/g, which is 40% higher than the traditional process.
2. Low-temperature flue gas scenario
For coke oven flue gas with a temperature of less than 80°C:
Appropriately increase the screen residue to 18%-20% to slow down the particle dissolution rate;
Add low-temperature activity promoters (such as nano cerium oxide) to compensate for the activity loss caused by the increase in particle size.
3. High-dust flue gas scenario
In coal-fired flue gas with a dust content of more than 50g/Nm³:
Control the screen residue at 12%-15%, and use the flushing effect of medium-sized particles to prevent scaling in the tower;
Use a cyclone to pre-separate large-particle fly ash to reduce interference with the magnesium hydroxide particle size system.
5. Economic and environmental benefits upgrade
Operation cost optimization: Precise particle size control reduces the unit consumption of magnesium hydroxide by 18%-25%, saving more than one million yuan in annual reagent costs;
Breakthrough in energy consumption bottleneck: slurry transportation resistance decreases by 30%, and circulating pump power consumption decreases by 20%;
By-product value enhancement: the crystallinity of magnesium sulfate generated by the optimized reaction is improved, with a purity of 98%, which can be directly sold as agricultural fertilizer;
Carbon emission reduction benefits: every 10,000 tons of SO₂ removal reduces CO₂ emissions by about 600 tons, helping enterprises to trade carbon quotas.
Conclusion: Particle size revolution drives the upgrading of the desulfurization industry
The precise control of the 200-mesh sieve residue is rewriting the application rules of magnesium hydroxide desulfurizer. This efficiency revolution, which started with micron-sized particles, not only solved the traditional contradiction between reaction activity and engineering stability, but also promoted the iteration of environmental protection processes towards refinement and intelligence. With the deepening implementation of the "Air Pollution Control Action", the particle size optimization solution that is both scientific and economical will surely become the standard technology for industrial flue gas treatment. Enterprises need to grasp the core logic of granularity control and build competitive advantages in the balance between efficient desulfurization and sustainable operations.