In chemical engineering, the scrubber definition typically includes both wet and dry units for air purification. This purification equipment is widely used in the chemical industry wherever production processes generate harmful, toxic, or simply unwanted gaseous emissions.
The selection and design of such equipment is a complex engineering task, as chemical emissions are highly toxic and pose a threat not only to personnel but also to production equipment. These emissions can quickly damage systems that lack sufficient corrosion protection. In addition, the purification technology must be capable of handling the required load.
Areas of Application
The most common types of pollutants and the industries where they are typically encountered:
Industry/Process | Typical Pollutants |
Production of mineral acids | Vapors of sulfuric acid, nitric acid, hydrochloric acid |
Fertilizer manufacturing | Ammonia, nitrogen oxides (NOx), phosphate dust |
Chlorine, caustic soda, HCl, PVC, plastics, chlorinated organics, disinfectants, bleaching agents | Hydrogen chloride (HCl), chlorine (Cl₂), organic compounds (solvents, refrigerants, pesticides) |
Dyes, pharmaceuticals, household chemicals | Organic vapors, acid fumes, ammonia, solvents |
Production of sulfates, nitrates, alkalis | Sulfur dioxide (SO₂), nitrogen oxides (NOx), ammonia (NH₃) |
Oil refineries | Hydrogen sulfide (H₂S), mercaptans |
Metallurgical and electrochemical plants | Acid vapors, metal oxides, fluoride compounds, chlorine compounds |
Waste incineration, power generation facilities | Sulfur dioxide (SO₂), nitrogen oxides (NOx), hydrogen chloride (HCl), hydrogen fluoride (HF), dioxins, furans |
Functions
The primary function is emission control—it removes harmful acidic gases (such as ammonia, acid, and alkali vapors) before they are released into the atmosphere. Additionally, a scrubber in a chemical plant performs several other tasks:
1. Removal of dust and aerosols
Captures fine particulate matter generated in various technological processes. The diameter of particles that can be removed depends on the size of the liquid droplets inside the tower: the smaller the droplets, the more effectively fine particles are captured. Modern equipment can remove dust as fine as 1–2 microns and even smaller.
2. Neutralization of toxic substances
Harmful compounds are neutralized through chemical reactions with scrubbing solutions, either dissolving them or converting them into safer substances.
3. Odor reduction
Eliminates volatile compounds that cause unpleasant odors.
4. Cooling
Reduces the temperature of streams, protecting downstream equipment (such as filters and fans) and preventing condensation and corrosion.
Design
CFD modeling methods are used to achieve uniform distribution of phases, reduce energy consumption, and increase the lifetime of chemical engineering scrubber.
Step 1: Determine the type and amount of harmful substances to be removed.
Step 2: Calculate the required capacity, flow volume, temperature, and operating conditions (such as temperature and pressure).
Step 3: Select the scrubbing liquid—water, alkali, acid, or other solutions.
Step 4: Choose the equipment configuration: wet/dry, Venturi, tray, packed bed, etc., based on the purification requirements.
Step 5: Select construction materials, taking into account the aggressiveness of the medium (stainless steel, plastic, FRP, etc.).
Step 6: Optimize flow velocity, droplet size, and ensure uniform distribution of the liquid.
Additional steps:
- Include demisters and systems to prevent liquid carryover; consider the possibility of using the equipment for gas cooling.
- Provide for access for maintenance, cleaning, and replacement of consumables.
- Arrange for collection, neutralization, or disposal of contaminated scrubbing liquids.
- Implement automatic control, monitoring, and interlock systems.
Comparison of Scrubber and Adsorber Types
Equipment Type | Purpose | Operating Principle | Efficiency | Advantages | Limitations |
Packed Bed Tower | Removal of soluble gases (HCl, SO₂, NH₃) | Gas passes through packing irrigated by cleaning liquid | High for volatile contaminants, moderate for dust >5 μm | Simple design, effective pollutant removal | Less effective for fine dust, possible packing clogging |
Venturi | Capture of fine particles and aerosols (<1 μm) | Gas accelerates in a narrowing and mixes with solution | Very high for particles <1 μm | High efficiency, compact size | High energy consumption, wastewater generation |
Tray Tower (Plate Column) | Removal of soluble gases, droplets, and coarse particles | Airstream passes through a liquid layer forming bubbles | Moderate for particles >5 μm | Good contact between phases, adjustable operation | Less effective for fine particulate matters |
Rotoclone | Air cleaning from particulate matters and gases in various industries | Gas passes through a water curtain. Particles are captured in the water. | Up to 99.9% for particles ≥0.5 μm | Compact, easy maintenance, environmentally friendly | Requires pre-cleaning at high dust loads |
Tank Vent Scrubber | Air purification from storage tank vents | Air passes through irrigated packing, removing harmful compounds | Up to 99.9% (depends on pollutants) | Compact, easy maintenance, regulatory compliance | Limited capacity (up to 3000 cfm) |
Sirocco Adsorber | Removal of CO₂ and other contaminants from tank air | Air passes through an adsorbent, removing CO₂ | Up to 99% for CO₂ | Easy maintenance, automatic control, energy efficient | Not suitable for dust and aerosol removal |
Implementation Examples and Innovations
Cost
💰 Capital Expenditures (CAPEX)
Type | Capacity (m³/h) | Approximate Cost (USD) |
Small units (plastic, standard configuration) | 1000–5000 | $20000 – $60000 |
Medium units (FRP, automation, 1–2 stages) | 10000–30000 | $70000 – $200000 |
Large industrial systems (high-resistance materials, multi-stage process) | 50000–200000 | $300000 – $1000000+ |
Expense Category | Approximate Annual Cost (USD) |
Energy consumption (pumps, fans) | $1000 – $20000 |
Maintenance and repair | $1000 – $20000 |
Consumables (reagents, water) | $1000 – $10000 |
Waste disposal | Depends on volume and local tariffs |
Monitoring and automation | Included in CAPEX or separately |
🧾 Example Calculation
For a facility with a unit capacity of about 10000 m³/h:
- Capital costs: approximately $100000 – $200000
- Annual operating costs: approximately $10000 – $30000
Investing in scrubbers requires significant initial costs, but they provide effective emission control and ensure compliance with environmental regulations. When planning, it is important to consider both capital and operating expenses, as well as potential costs for future upgrades and maintenance.
If you need more detailed calculations or assistance in selecting the right equipment, please contact us — we are here to help!
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Vladimir Nikulin
