Magnesium hydroxide desulfurization tower demister transformation: efficiency comparison between cyclone plate and ridge type
I. Industry pain points and technology upgrade logic
In the magnesium hydroxide wet desulfurization system, the performance of the demister directly affects the flue gas emission quality and equipment operation stability. Traditional flat-plate demisters generally have problems such as large pressure drop and severe secondary entrainment when dealing with high-dust and high-humidity flue gas. Taking a coking plant in Liaoning as an example, the droplet concentration at the outlet of its desulfurization tower has long exceeded the standard (>75mg/m³), resulting in aggravated flue corrosion and an annual maintenance cost of more than 5 million yuan. In this context, cyclone plate demisters and ridge type demisters have become the two core directions of technology upgrades, and the efficiency difference and applicable scenarios between the two have become the key to engineering decisions.
II. Comparison of core performance parameters
1. Separation efficiency and applicable flow rate
Cyclone plate demister: gas-liquid separation is achieved through centrifugal force and inertial collision, and the capture efficiency of droplets above 10μm can reach more than 95%. It performs best in the range of flue gas velocity of 3.5-5.5m/s, and is particularly suitable for complex working conditions with dust concentration > 200mg/m³ (such as steel sintering flue gas).
Roof demister: It adopts a multi-fold corrugated plate structure, and the droplets are separated after multiple collisions and coalescence, and the capture efficiency of ultrafine droplets below 5μm reaches 98%. The design flow rate can be increased to 4.5-6m/s, which is suitable for high flow rate and low dust content scenes such as coal-fired power plants.
2. System pressure drop and energy consumption
The pressure drop of the swirl plate system is usually 800-1200Pa, and its spiral flow channel design can reduce the fan energy consumption by 30%;
The ridge pressure drop range is 1000-1500Pa, but by optimizing the blade inclination angle (15°-20°) and spacing (20-30mm), the energy consumption can be controlled within a reasonable range.
3. Anti-blocking performance and maintenance cost
Due to the forced vortex effect, the cyclone plate can reduce the risk of crystallization blockage by more than 60%. A project in Tangshan showed that its flushing frequency was reduced from twice a week to once a month;
The ridge-type blade has a smooth surface and self-cleaning grooves. With high-pressure backwashing (coverage rate of 160%), it is more corrosion-resistant in the environment of magnesium hydroxide slurry with large pH fluctuations.
III. Analysis of typical engineering cases
Case 1: Transformation of cyclone plates in Shanxi coking plant
Pain points of the original system: dust content of flue gas is 300mg/m³, droplets at the outlet of the flat-plate demister are greater than 100mg/m³, and the induced draft fan is seriously water-carrying.
Transformation plan: Install a three-stage cyclone plate + bottom guide cone, with an ultrasonic anti-blocking module.
Operation data:
The outlet droplet concentration is reduced to 35mg/m³, and the dust removal efficiency is increased to 97%;
Annual electricity saving is 420,000 kW·h, and maintenance costs are reduced by 55%.
Case 2: Upgrading the roof type of coal-fired power plant in Jiangsu
Special requirements: Flue gas flow rate of 5.8m/s, outlet droplets required to be less than 50mg/m³.
Innovative design: double-layer roof type + top tube pre-demist unit, blades are made of PPTV polymer material.
Economical efficiency:
The system pressure drop only increased by 8%, and the desulfurization efficiency was stabilized at more than 95%;
The amount of magnesium sulfate crystal attachment was reduced by 70%, saving 800,000 yuan in chemical cleaning costs annually.
IV. Transformation selection decision model
1. Flue gas characteristics adaptation
High dust and high viscosity: Cyclone plates are preferred, and their centrifugal separation mechanism can effectively handle complex slurries with a solid content of more than 20%;
High flow rate and low dust content: The ridge type has a more efficient advantage in flow rate scenarios above 4.5m/s due to its streamlined structure.
2. Space and cost constraints
The swirl plate tower body has a low height requirement, which is suitable for compact transformation of old desulfurization towers;
The ridge type needs to reserve 1.2 times the tower diameter height, but the modular design can achieve segmented replacement without stopping the machine.
3. Life cycle cost
The initial investment of the swirl plate is 15% lower, but the impeller replacement cycle is short (3-5 years);
Although the initial cost of the ridge type is higher, its service life of more than 10 years and low maintenance characteristics are more suitable for long-term operation.
V. Technology integration and future trends
1. Composite design breakthrough
Swirl-ridge series: the first-level swirl plate pre-treats high-dust flue gas, and the second-level ridge type deeply purifies, and the overall efficiency is increased to 99.5%;
Intelligent flushing system: based on the turbidity sensor, the flushing frequency is dynamically adjusted, saving 30% of water while avoiding secondary entrainment caused by excessive flushing.
2. Empowerment of material science
Silicon carbide coated swirl blades: withstand corrosion environments with Cl⁻ concentrations > 50,000 mg/L, and extend service life to 8 years;
Nano-hydrophobic ridge plate: surface contact angle > 150°, reducing 80% of magnesium sulfate crystal attachment.
3. Digital twin operation and maintenance
Three-dimensional flow field simulation technology: real-time prediction of swirl plate wear hotspots, optimize blade inclination angle and rotation speed;
AI energy efficiency algorithm: automatically switch to ridge-type working mode according to flue gas load, reducing SO₂ treatment energy consumption by 18%.
When the centrifugal force field of the swirl plate and the ridge-type collision and aggregation mechanism are intertwined in the desulfurization tower, the essence of this technical game has gone beyond simple equipment selection and directly pointed to the efficiency revolution of industrial environmental protection. From the dust vortex of the coking plant to the ultra-clean emissions of the power plant, the transformation of each demister is a precise response to the characteristics of the flue gas. In the future, only by focusing on the essence of the working conditions and breaking the technical boundaries can we write a new chapter of green transformation in the balance between efficiency and cost.