Transport in the dilute phase, whether by pressure or vacuum, is characterised by low or medium pressure and higher speed. (Typically high-pressure fans and pressure pumps). The transport pressure with fans is up to 100 mbar, and with pressure pumps, up to 900 mbar.
Dilute, semi-dense, and dense phase by vacuum
Characteristics:
Pressure: Vacuum (Max. -0.9 Kg/cm²)
Phase: Dilute, semi-dense, and dense
Average speed: Between (15 and 30 m/s) (5 and 15 m/s) (1 and 5 m/s)
Throughput: Continuous and irregular batches
Observations:
Normally for low-density products
Can be with or without fluidisation
With tangential V or injectors
The conveying can be continuous or batch
It is an advanced solution that uses vacuum instead of positive pressure to move bulk materials through pipelines. This system leverages the flexibility of different conveying phases (dilute, semi-dense, and dense) to adjust the flow and speed of the material based on its characteristics, ensuring efficient, safe, and controlled handling. In this system, the vacuum is generated in the part of the pipe through which the material moves, allowing the particles to be drawn into the pipelines, which can offer advantages over positive pressure systems in certain contexts.
The vacuum pneumatic conveying system works by creating a negative pressure in the conveying pipes, which generates the flow of air and material into the system. Depending on the selected phase (dilute, semi-dense, or dense), the behaviour of the air and material varies:
Dilute phase: In this phase, the air has a high ratio to the material. A stronger suction is used, which allows the particles to be quickly drawn in and suspended in the air. This type of conveying is used for light materials or when high transport speeds are required over short distances.
Semi-dense phase: In this phase, the air-to-material ratio is intermediate, allowing for more precise control of the flow. The material is not fully suspended in the air, but forms a partially fluidised "bed" inside the pipe. This is useful for materials that need to be conveyed efficiently without causing excessive turbulence.
Dense phase: Here, the air-to-material ratio is low. The material moves in a dense "bed", with a much smoother air flow. This type of conveying is ideal for heavier materials or when it is necessary to avoid excessive wear on the material or the pipes. The vacuum in this phase keeps the material flow constant without the need for large volumes of air
The combination of these three phases allows the vacuum pneumatic conveying system to adjust optimally according to the type of material and operational conditions, ensuring efficient and flexible handling.
This type of pneumatic conveying is particularly useful in industries where bulk materials have varied characteristics or require different handling methods depending on their properties. Some of the most common applications include:
Pharmaceutical industry: For the conveying of delicate pharmaceutical products such as fine powders, excipients, or active ingredients. The flexibility of the phases allows adaptation to the specific needs of each material without damaging it.
Food industry: For moving materials such as flours, sugar, salt, spices, and other powdered or granular products that require careful and efficient handling, adapting to different particle sizes and fragilities.
Chemical industry: For the conveying of powdered or granular chemicals, such as fertilisers, pigments, petrochemical products, or additives, where the adaptability of the system is essential to ensure a constant and controlled flow.
Recycling and waste management: In applications for conveying recyclable materials or waste in the form of powder or fine particles, where efficient handling is required to minimise dispersion and contact with contaminants.
Construction materials industry: For moving materials such as cement, plaster, lime, or abrasive products, where phase control and energy efficiency are key to reducing operational costs.
Greater material control: By using vacuum and adapting the conveying phases (dilute, semi-dense, and dense), the system allows precise control over the speed and flow of the material, making it ideal for materials that require delicate or controlled handling.
Lower risk of damage: The vacuum system reduces the likelihood of material damage during transport, especially for fragile products or those sensitive to abrasion. This is particularly useful in industries such as food and pharmaceuticals.
Energy efficiency: By using vacuum to generate the flow instead of positive pressure, the system can consume less energy, especially in the dense and semi-dense phases, where the air-to-material ratio is low. This can result in greater operational efficiency and lower energy costs.
Versatility: The combination of dilute, semi-dense, and dense phases allows the system to adapt to different types of materials, from fine powders to heavier or granular materials, making it a highly flexible solution suitable for various industrial applications.
Reduced material dispersion: Since the system is based on suction, the risk of material dispersion into the environment is reduced, which is particularly relevant in industries where air contamination or exposure to toxic or hazardous products must be minimised.
Transport over long distances: Vacuum is efficient for transporting materials over long distances, even in complex piping systems, enabling its use in large or intricately designed installations.
Maintenance and constant monitoring: The vacuum system requires regular maintenance, especially on the vacuum pumps and components related to suction. Additionally, it is crucial to monitor the pressure and transport phases to ensure adequate and constant flow.
Implementation cost: Although vacuum systems tend to be more costly initially due to the investment in vacuum pumps and control systems, the benefits in energy efficiency and waste reduction can offset this investment in the long term.
Requires advanced control systems: To manage the transport phases properly and ensure efficient operation, an advanced control system is needed to regulate the pressure and airflow, as well as adjustments between the different transport phases.
The combination of vacuum pneumatic conveying in dilute, semi-dense, and dense phases is an extremely flexible and efficient solution for handling bulk materials across a variety of industries. Its ability to adapt to the material characteristics and process conditions, while optimising energy use and reducing the risk of damage, makes it an ideal choice for sectors that handle sensitive materials or require precision and control.
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