Improved activity of magnesium hydroxide desulfurizer: optimal solution for the amount of surface modifier added
In the field of high-sulfur flue gas treatment such as thermal power and steel, the activity of magnesium hydroxide desulfurizer directly determines the desulfurization efficiency and operating cost. In traditional processes, problems such as large agent consumption and difficult by-product treatment caused by insufficient desulfurizer activity have long existed. Through surface modification technology, the desulfurization efficiency can be increased by more than 30% without increasing the cost of raw materials.
1. The dual role of surface modification: the leap from "inert" to "superactive"
The surface of magnesium hydroxide particles has insufficient effective reaction sites due to the uneven distribution of hydroxyl groups (-OH) and the easy agglomeration characteristics. Surface modifiers solve this problem through the following mechanisms:
Dispersion and anti-agglomeration: modifier molecules wrap the particle surface to form an electrostatic repulsion layer, which reduces the particle size from micrometer level (50μm) to nanometer level (100nm), and increases the specific surface area by 4 times;
Activation of active sites: selectively etching the inert crystal plane to expose the highly active (001) crystal plane, and the surface hydroxyl density increases from 3.2/nm² to 12.5/nm².
Comparison of experimental data (taking silane coupling agent KH-550 as an example):
Modifier addition amount (wt%) Specific surface area (m²/g) SO₂ adsorption capacity (g/g) Desulfurization efficiency (%)
0 (unmodified) 15 0.8 78
1.5 85 2.1 92
3.0 (optimal) 120 3.3 97
4.5 110 3.0 95
Conclusion: When the modifier addition amount is 3%, the desulfurizer activity reaches its peak, and excessive addition will hinder mass transfer due to the thick molecular layer.
2. Three major technical adaptations in industrial applications
1. Engineering amplification of modification process
The laboratory magnetic stirrer is difficult to meet the needs of mass production, and the equipment needs to be upgraded:
High-speed shear emulsifier: speed > 3000rpm, to ensure uniform coating of the modifier, batch consistency of 98%;
Spray drying tower: inlet temperature 180℃, outlet 80℃, so that the modifier and magnesium hydroxide particles are more closely combined.
Case: Jiangsu Zehui Technology has built a 100,000 tons/year modified magnesium hydroxide production line, and the activity fluctuation rate is controlled within ±5%.
2. Adaptability to complex flue gas composition
In view of the high dust content (>10g/Nm³) and large humidity fluctuations of steel sintering flue gas, the modification strategy is adjusted:
Compound modifier formula: silane coupling agent (2%) + sodium dodecyl sulfate (1%), anti-dust adsorption capacity increased by 50%;
Gradient addition system: dynamically adjust the modifier flow rate according to the flue gas SO₂ concentration (2000-8000mg/Nm³), with an error of<0.5%.
3. Cost control and benefit balance
Cost item Unmodified process Modified process (3% addition) Optimization range
Desulfurizer unit price 900 yuan/ton 1050 yuan/ton ↑16.7%
SO₂ consumption per ton 0.65 tons 0.35 tons ↓46%
By-product purity 85% 98% ↑15%
Comprehensive cost 585 yuan/ton SO₂ 367 yuan/ton SO₂ ↓37%
Calculation case: A 600MW unit processes 30,000 tons of SO₂ annually, and the modified process saves (585-367) × 30,000 = 6.54 million yuan per year.
3. Regional practice of the optimal solution for modifiers
1. High-sulfur coal power plants: silane-based modifiers dominate
Applicable scenarios: SO₂ concentration > 4000mg/Nm³, flue gas temperature > 120℃;
Formula: KH-550 silane (3%) + nano-SiO₂ (0.5%), high-temperature sintering resistance increased by 3 times;
Case: After application in Huaneng Dezhou Power Plant, the desulfurization efficiency jumped from 88% to 96%, and the catalyst replacement cycle was extended from 3 months to 1 year.
2. Steel sintering machine: anionic surfactants are preferred
Applicable scenarios: high dust (> 5g/Nm³), large humidity fluctuations;
Formula: sodium dodecylbenzene sulfonate (2.5%) + polyvinyl alcohol (0.5%), dust adsorption reduced by 60%;
Case: The desulfurization efficiency of the sintering machine at Baosteel Zhanjiang Base is stable at 94%, reducing the annual consumption of reagents by 800 tons.
3. Small and medium-sized boilers: Breakthrough in low-cost biomass modifiers
Applicable scenarios: sulfur content<2000mg/Nm³, intermittent operation;
Formula: sodium lignin sulfonate (1.8%) + starch graft (1.2%), the cost is 40% lower than the silane system;
Case: After the transformation of 20 boilers in a printing and dyeing park in Zhejiang, the desulfurization cost dropped from 120 yuan/ton SO₂ to 75 yuan.
IV. Technical challenges and future trends
1. Improved long-term stability
Microcapsule coating technology: The modifier is encapsulated in a pH-responsive material, which is automatically released in an acidic environment, and the activity retention rate is increased from 80% to 95%;
Case: The pilot test of Tsinghua University shows that the effective period of the modifier is extended from 6 months to 18 months.
2. Modification-regeneration integration
Low-temperature desorption process: Recover the failed modifier at 150℃, with a recycling rate of ＞85%, reducing the raw material cost by 30%;
Industrial practice: Japan's JFE Steel has achieved the recycling of modifiers, and the cost of treating one ton of SO₂ has been reduced by another 12%.
3. Intelligent and precise control
Online spectral monitoring: Real-time analysis of the thickness of the modified layer through Raman spectroscopy, and the accuracy of the added amount is adjusted to ±0.1%;
Digital twin model: Simulate the optimal addition strategy under different flue gas conditions, and compress the fluctuation of desulfurization efficiency to ±1%.
The golden addition ratio of 3% of the surface modifier confirms the technical philosophy of "four ounces to move a thousand pounds" - through molecular-level structural regulation, the exponential leap in the activity of the desulfurizer is achieved. From the 96% desulfurization efficiency of Huaneng Power Plant to the cost halving of small and medium-sized boilers, industrial practice has verified its economic feasibility. With the revision of the "Technical Specifications for Industrial Flue Gas Treatment", the modified magnesium hydroxide process may become the standard for high-sulfur treatment. As experts from the Chinese Academy of Environmental Sciences said: "The value of surface modification lies in activating the maximum potential of materials with minimal intervention, which is the essence of the circular economy."