Selection Guide for Acid Mist Treatment System of Quartz Sand Purification
Equipment: 5 Core Elements for Compliant Emissions
Mandatory standards: Acid mist emission concentration ≤15mg/m³ (GB
16297-1996), fluoride ≤7mg/m³ (HJ 544-2016)
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I. Characteristics and treatment difficulties of acid mist
1. Composition of acid pickling mist from quartz sand
- Main pollutants: hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric
acid mist (H₂SO₄)
- Typical concentration: HF 80-120mg/m³ (mixed acid process), HCl
200-500mg/m³
- Temperature range: 40-65℃ (cooling measures need to be considered)
2. Addressing challenges
- Strong corrosivity: The corrosion rate of HF is three times that of HCl
(304 stainless steel can only withstand concentrations <5%)
- Dust interference: Quartz particles (with a particle size of 0.5-10μm)
floating in the acid pickling tank are prone to clogging the purification
layer
- Temperature sensitivity: The lifespan of plastic equipment decreases
sharply when the temperature exceeds 50℃
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II. Comparison of Four Major Mainstream Technology Choices
1. Three-stage spray tower (low investment, suitable for small and
medium-sized applications)
- Primary alkali wash: neutralize free acid with 20% NaOH solution (maintain
pH at 10-11)
- Secondary oxidation: decomposition of fluorosilicate with 5% sodium
hypochlorite
- Tertiary fine washing: deep defluorination of Ca(OH)₂ milk slurry (CaF₂
precipitation)
- Applicable scenario: Total acid mist volume <3000m³/h, HF concentration
<50mg/m³
2. Molecular sieve adsorption system (high-precision processing)
- Core material: aluminum-based molecular sieve (pore diameter 0.5nm)
- Adsorption capacity: HF 120mg/g (requires hot air regeneration at 200℃)
- Advantages: Emission concentration can reach ≤3mg/m³
- Limitation: dust needs to be pre-filtered to <1mg/m³
3. Wet electrostatic precipitation (WESP, collaborative treatment of dust and
acid mist)
- Plate material: lead-antimony alloy/conductive fiberglass (resistant to HF
corrosion)
- Design parameters: wind speed 0.8-1.2m/s, dwell time ≥8s
- Efficiency: Acid mist removal rate >95%, dust removal rate >99%
4. Low-temperature plasma (emerging technology)
- Reaction mechanism: High-voltage discharge generates ·OH radicals which
decompose HF
- Energy consumption cost: 35-40 kW of power consumption for processing 1000
m³/h
- Applicable scenario: Intermittent acid pickling line (fast start-stop
response)
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III. Material selection for key equipment
1. Tower structure
- Economic solution: FRP (thickness ≥10mm, Barcol hardness >45)
- Long-life solution: PPH overall winding (with UV-resistant layer, lifespan
>15 years)
- Extreme operating conditions: PVDF-lined carbon steel (thickness ≥3mm)
2. Pump valve pipeline
- Circulating pump: fluoroplastic alloy magnetic pump (with flow passage
lining thickness ≥8mm)
- Sprinkler head: spiral solid cone nozzle (material: silicon carbide, hole
diameter: Φ20mm)
- Duct: PP plate welding (flange gasket wrapped with PTFE)
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IV. Operational Cost Control Strategy
1. Optimization of reagent consumption
- Automatic alkali solution proportioning: pH probe linked dosing pump
(accuracy ±0.3)
- Recycling of calcium agent: CaF₂ precipitate is recovered by a cyclone and
then re-reacted
2. Energy conservation design
- Waste heat recovery: When the inlet temperature of acid mist exceeds 50℃, a
plate heat exchanger is added (saving 30% energy)
- Variable frequency control: The fan power is adjusted in real-time
according to the air volume (saving 25%-40% of electricity)
3. Intelligent monitoring system
- Online fluoride ion meter: automatic switch to standby tower if exceeding
the standard
- Differential pressure alarm: When the resistance of the packing layer
exceeds 800Pa, trigger cleaning
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V. Case Study of a High-Purity Sand Project in Xinjiang
Operating conditions: mixed acid (HF+H₂SO₄) pickling line, air volume
15000m³/h, initial HF concentration 85mg/m³
Scheme selection:
1. Pre-treatment: cyclone dust removal + surface cooler (cooling to 40℃)
2. Core equipment: Three-stage spray tower (PPH material)
- Level 1: 15% NaOH spray
- Level 2: NaClO oxidation
- Level 3: Fluoride removal using Ca(OH)₂ slurry
3. Post-treatment: Mist eliminator (PP baffle plate)
Operational effect:
- Emission concentration: HF 2.8mg/m³, particulate matter 6.5mg/m³
- Operating cost: 0.38 yuan/ton of sand (including chemicals, electricity
consumption, and maintenance)
- Equipment lifespan: 6 years without corrosion-induced leakage
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conclusion
The selection of quartz sand acid mist treatment equipment should closely
adhere to the iron triangle of "corrosion protection, purification efficiency,
and cost control". It is recommended that production lines with a capacity of
2000m³/h or above adopt a combination process of spray tower and wet
electrostatic precipitation to ensure stable compliance with standards for 10
years.