Demister

A demister, also known as a mist eliminator or entrainment separator, is a critical component within an absorption column system. It is typically installed at the top of the column or in the vapor outlet line. Its primary function is to capture and coalesce fine liquid droplets (mist) that are carried upward by the gas/vapor stream, preventing liquid carryover into downstream equipment. This ensures product purity, protects compressors or other units, improves separation efficiency, and reduces solvent loss. The demister operates based on inertial impaction, interception, and diffusion. As the gas/vapor stream laden with liquid droplets passes through the demister pad (usually made of knitted wire mesh, vane packs, or fiber beds), the droplets collide with the surfaces of the demister elements. These collisions cause the droplets to coalesce into larger droplets. Once the droplets become sufficiently large, gravity overcomes the drag force of the gas stream, causing the liquid to drain down the demister elements and back into the column or a collection sump, while the cleaned gas/vapor exits. Materials commonly used include stainless steel (e.g. 304, 316L), polypropylene (PP), polytetrafluoroethylene (PTFE), and nickel alloys. Typical reference parameters for selection include operating pressure (1.0–1.6 MPa), operating temperature (-40–85°C), gas flow rate (1000–50000 m³/h), removal efficiency (99.5–99.9% for droplets > 5 μm), pressure drop (0.2–1.0 kPa), mist elimination capacity (0.1–10 mg/m³), material grade (304–316L per ASTM A240), vessel diameter (300–3000 mm), weight (50–500 kg), and IP rating (IP54–IP65 per IEC 60529). These values are reference ranges and must be verified for the specific model and application with the legal manufacturer or supplier. The demister is a component, not a standalone system; its performance depends on proper integration with the column design, gas velocity, and liquid load. Maintenance signals include increased pressure drop, reduced removal efficiency, or visible corrosion. Failure boundaries include exceeding temperature or pressure limits, which can cause material degradation or structural failure. Always confirm model-specific values and standards with the legal manufacturer or supplier before procurement.

The demister operates based on inertial impaction, interception, and diffusion. As the gas/vapor stream laden with liquid droplets passes through the demister pad (usually made of knitted wire mesh, vane packs, or fiber beds), the droplets collide with the surfaces of the demister elements. These collisions cause the droplets to coalesce into larger droplets. Once the droplets become sufficiently large, gravity overcomes the drag force of the gas stream, causing the liquid to drain down the demister elements and back into the column or a collection sump, while the cleaned gas/vapor exits.