{"id":7911,"date":"2025-11-06T07:29:14","date_gmt":"2025-11-06T06:29:14","guid":{"rendered":"https:\/\/recyclemachine.net\/?p=7911"},"modified":"2026-08-12T17:56:54","modified_gmt":"2026-08-12T09:56:54","slug":"la-guida-definitiva-alla-macchina-di-essiccazione-termica-nel-riciclaggio-dei-materiali-plastici","status":"publish","type":"post","link":"https:\/\/www.energycle.com\/it\/la-guida-definitiva-alla-macchina-di-essiccazione-termica-nel-riciclaggio-dei-materiali-plastici\/","title":{"rendered":"Macchina di essiccazione termica per riciclaggio plastica: Guida"},"content":{"rendered":"
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A thermal drying machine in a plastic washing line uses heated air to remove moisture that remains after mechanical dewatering. It should be selected from the polymer form, incoming moisture, required final moisture, ambient air condition and saleable throughput. A generic claim such as \u201cbelow 3%\u201d is incomplete unless the feed, sampling point and test method are defined.<\/p>\n

Thermal drying is the second drying step<\/h2>\n

Mechanical equipment should remove free water before heat is added. A centrifugal dryer is commonly used for rigid flakes, while a screw press or film squeezer can suit flexible material. Thermal air then removes the remaining surface moisture that cannot be economically separated by mechanical force.<\/p>\n

Sending unnecessarily wet material into a hot-air system increases evaporation load, air volume and energy use. Diagnose mechanical dewatering, drainage and carry-over before increasing heater output.<\/p>\n

Surface drying versus resin pre-drying<\/h2>\n

A washing-line thermal dryer is not automatically a substitute for a desiccant resin dryer at an extruder. Polyolefin flakes often need surface-water removal. Hygroscopic polymers such as PET can absorb moisture into the resin and may need controlled low-dew-point drying before melt processing according to the extruder and application specification.<\/p>\n

Define the handoff: washed flake for storage or sale, or prepared feed entering an extrusion process. The moisture limit and sampling location should come from the downstream buyer or process owner.<\/p>\n

How a pneumatic hot-air dryer works<\/h2>\n
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  1. Metered feed:<\/strong> mechanically dewatered plastic enters at a stable rate.<\/li>\n
  2. Heated air contact:<\/strong> a blower moves heated air through a duct where flakes or film are suspended and conveyed.<\/li>\n
  3. Moisture transfer:<\/strong> heat supplies evaporation energy while airflow carries water vapour away.<\/li>\n
  4. Residence:<\/strong> duct length, material velocity and recirculation determine contact time.<\/li>\n
  5. Separation:<\/strong> a cyclone or separator removes dried plastic from the air stream.<\/li>\n
  6. Exhaust or return:<\/strong> air is discharged or partly recirculated through an engineered filtration and humidity-control system.<\/li>\n<\/ol>\n

    The thermal dryer for plastic recycling<\/a> illustrates this washing-line configuration.<\/p>\n

    Five variables control drying performance<\/h2>\n
    \n\n\n\n\n\n\n\n\n\n
    Variable<\/th>\nEffect<\/th>\nWhat to measure<\/th>\n<\/tr>\n<\/thead>\n
    Incoming moisture<\/td>\nSets the water load that must be removed<\/td>\nRepresentative wet-basis moisture after mechanical dewatering<\/td>\n<\/tr>\n
    Air temperature<\/td>\nChanges heat transfer and evaporation potential<\/td>\nSupply and exhaust temperature under load<\/td>\n<\/tr>\n
    Air humidity<\/td>\nDetermines the air’s capacity to accept more water<\/td>\nAmbient or process-air humidity and dew point where relevant<\/td>\n<\/tr>\n
    Airflow<\/td>\nTransports heat, vapour and material<\/td>\nFlow or pressure, filter condition and leaks<\/td>\n<\/tr>\n
    Residence and loading<\/td>\nControls contact time and heat per unit mass<\/td>\nDry feed rate, recirculation and material holdup<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    A higher temperature cannot compensate safely for blocked airflow or unstable feed. Excess temperature can soften, deform, oxidise or discolour material and can create a fire or fume hazard.<\/p>\n

    Calculate the actual water-removal duty<\/h2>\n

    Use wet-basis moisture consistently. If the wet feed rate is W<\/em>, incoming moisture fraction is Min<\/sub><\/em> and target moisture is Mout<\/sub><\/em>, the water to remove is:<\/p>\n

    Water removal = W \u00d7 (Min<\/sub> \u2212 Mout<\/sub>) \u00f7 (1 \u2212 Mout<\/sub>)<\/strong><\/p>\n

    For example calculations, use measured values from representative production; do not substitute catalogue assumptions. Heater, blower, duct and separation capacity must all support the water load at the site’s ambient condition.<\/p>\n

    Choose equipment by material form<\/h2>\n

    Rigid PET, HDPE or PP flakes convey differently from light LDPE film. Particle size, bulk density, fines, labels and temperature sensitivity influence pickup velocity, cyclone performance and residence.<\/p>\n