Dense phase is characterized by high positive pressure conveying at low velocity. The most common positive pressure dense phase pneumatic conveying regimes are:Continuous Dense Phase High Pressure – Low Velocity Material is conveyed below the saltation velocity in a moving bed flow pattern (rolling or plowing). Velocities are 3 10/sec at the feed end, and 15 18 m/sec at the terminal end.Continuous dense phase is used to handling powders that may be easily fluidized and are able to retain air.Bed Flow Dense Phase Pneumatic Conveying Regime Discontinuous Dense Phase High Pressure – Low Velocity Material is conveyed below the saltation velocity in a slug-type flow pattern, i.e., a slug or series of slugs separated by air gaps are conveyed along the pipe. The slugs completely fill the full cross-section of the pipe. Velocities at the feed end are typically 1 -5 m /sec and 7 10 ft/sec at the discharge end.
MDSJ Dense phase pneumatic conveying is a method for moving difficult, abrasive, mixed batch, or friable materials at a low product velocity. The materials are conveyed within the pipe in slug form using small amounts of gas at a low velocity and high pressure. This type of system is favored for its low operating costs,
basic maintenance, and minimal material degregation and system wear. This method is typically selected for moving material from a single collection point to either single or multiple destination points. Common materials suitable for dense phase conveying include sand, cement, mixed batch, chemicals, limestone, pet food, and others.
Provided the material is suitable for a discontinuous flow regime, this is the best regime for most applications in which power economy, pipe erosion, and material degradation issues are important. Slug Flow Dense Phase Pneumatic Conveying Regime Solid Flow Dense Phase High Pressure – Low Velocity System Material is conveyed well below the saltation velocity with the pipe almost completely full of material. The material is virtually extruded through the pipeline. The conveying velocity is 1-3sec throughout the system. There is virtually no agitation or turbulence within the pipeline with this flow regime.
REDUCE SYSTEM WEAR AND PRODUCT DEGRADATION
WHILE IMPROVING MATERIAL TRANSFER EFFICIENCY
KEY BENEFITS
Our dense phase system offers Air BOOSTER , purge and non-purge concepts and continuous transport options. AIR BOOSTER strategically placed along the convey line to inject air, decreasing the required motive gas pressure and flow. This increases system reliability and reduces operational costs. • Non-purge concept - material can be intentionally left in the convey line, further minimizing ill effects from high velocity purges. This helps prevent material attrition and component wear, costly maintenance, and plant downtime. Continuous transporting - allows for continuous conveying of materials without a stoppage for de-pressurizing and refilling of the vessel.
Solid dense phase is best suited for fragile materials with an attractive operating economy and very low pipe erosion.Solid Flow Dense Phase Pneumatic Conveying Regime Below table provides a comparison of the four regimes. Flow Regime Average Velocity M/Second Air-to-Material Ratio Air Material Dilute Phase 28-35 20-33 Over 100:1 Continuous Dense Phase 7.5 to 22.5 5 to 15 20 to 100:1 Discontinuous Dense Phase 2.5 to 12.5 1.0 to 7.5 Below 30:1 Solid Flow Dense Phase 2.0 to 5.0 0.5 to 2.5 Below 20:1 In the above table, air to material ratio measures system efficiency. It is the ratio of weight (lbs/kg) of material conveyed per weight (lbs/kg) of conveying gas used.Due to low conveying velocity, dense phase systems are often chosen for applications where the product is friable, abrasive or smears such as sand, glass, and coke.Most applications will benefit from low velocity, if not due to reduced wear, then due to reduced air consumption. As a general rule, the best economies are achieved by using the lowest possible conveying velocity.