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Hopper Dryer

plastic dryer is an alternative product to the standard hot air dryer. Based on the main function, it fully considers environmental protection factors and improves it. It dries raw materials that are wet due to packaging, shipping or recycling.

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The working principle of a plastic dryer

In processing raw materials, the hopper dryer blows constant high-temperature air into the drying barrel through a drying fan. After the raw materials are heated, the moisture in the barrel is removed to achieve the purpose of removing the moisture in the raw material. The wind blown by the fan is heated by electric heating into hot dry air with high temperature. Through the screen protector and the chambers, the hot air can be distributed evenly to the raw materials in the barrel drier or dryer. Dryers can also have optional hot air recovery. The exhaust air is filtered by the return air and enters the dryer fan to form a closed circulation loop and save electricity.

Concept and general information of dryer

Hopper dryers are installations that are usually placed above the loading opening of machinery. They are designed for drying polymer raw materials. Such a drying method is usually common for polymers with low moisture content.

The use of dryers aims to reduce the problems related to the possible humidity of raw materials during processing and to improve the quality of the final plastic products.

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Hopper dryer

Polymer materials with low moisture index do not need to be dried. In particular, this is the case with the most common polyolefins – polyethylene and polypropylene.

However, if the raw material is not properly stored in the warehouses of raw material sellers, the material may still contain high amounts of moisture.

In these cases, the polymer must be dried and heated briefly before being loaded into the material cylinder of the equipment. This is to increase the efficiency of processing processes, such as injection molding or extrusion blow molding.

It is for this purpose that hopper dryers or hopper dryers are common in the modern plastics processing industry.

Design and principle of operation of hopper dryer

The standard design of a modern hopper dryer, hot air passes through the polymer material in the hopper from the bottom up. Relatively dry air reduces the moisture content of the plastic and exits the drying zone and mixes with the surrounding air.

In the most advanced dryers or polymer dryers, it is common for materials that require the best drying rate. As with polyethylene terephthalate (PET), air circulates through the system and the dryer is supplied with a moisture absorption unit.

This device allows you to drastically reduce air humidity with the help of special absorbents and direct it to the drying area for effective dehumidification.

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Hopper dryer performance

The dried material is taken from the bottom of the dryer funnel. In this case, undried raw materials enter the upper area of the shelter with the help of a vacuum loader. This leads to the opposite flow of warm air and wet polymer, which moves from top to bottom, and has a positive effect on the quality of dehumidification.

Drying by hopper dryer

It is important to remove hot air from the hopper dryers where the air is taken for drying, thus increasing the humidity of the source air.

In addition, the exhaust air is quite hot, which causes additional electricity consumption and increases the temperature of the workshop. All these factors lead to relatively high costs for the drying process.

More technically advanced and efficient is the use of a hopper dryer that works not only with hot air, but also with compressed air. The nature of the process is that the more the air is compressed, the less moisture it can contain. Therefore, compressed air is, by definition, relatively drier, without the need for additional preparation such as dehumidification.

The process of drying polymer materials with a dryer

The drying process of polymer materials involves the absorption of moisture by the expansion of hot air. As the gas volume increases, the moisture content of the polymer raw materials is partially transferred to the previously compressed air, but in a larger volume than in hot air drying technology.

In this case, usually the moist air coming out of the hopper dryers is also thrown into the workshop. Without any purification and dehumidification in certain models of warehouse dryers with hot compressed air, its regional source is provided, along with polymer heating.

How does a hopper dryer work?

Warm compressed air, and compressed air in general, absorbs water from polymer materials more effectively than air at atmospheric pressure. In recent years, leading manufacturers of peripheral equipment and, in particular, dryers, have begun to take advantage of this fact and offer new solutions for drying polymeric raw materials.

Vacuum hopper dryer systems have faded somewhat into the shadows due to their high cost and technical complexity. They are designed to remove as much water as possible from plastics.

The nature of the performance of such dryers for polymers stems from the physical fact that at low pressure. For example, 0.4 bar lowers the boiling point of water to about 45°C

Advantages of hopper dryer

Dryers or polymer funnel driers are good for getting rid of surface moisture in plastic pellets. These devices have several significant advantages:

low price,

A wide range of manufacturers around the world,


Ease of operation and maintenance

Stainless steel work pieces

Detachable design

Easy to clean

Temperature control system, with automatic shutdown of heating elements

The possibility of installing a magnetic clip

The vast majority of hopper dryers are common for plastic injection and blow molding machines. A much lower amount is common for various types of blow molding machines and other plastic processing methods. For extrusion, polymer dryers with large hopper volumes are common due to their high efficiency.

The dryer bunker is installed directly on the plastic injection machine or extruder and is designed to dry wet polymer raw materials with hot air.

The polymer hopper dryer, into which the initial wet material enters before being sent to the injection molding machine, during the drying process, excess moisture is quickly removed from it by hot air flow.

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Buying hopper dryer for plastic materials

Hopper dryer is an important piece of equipment for the production of plastic products. The moisture content of the polymer granule negatively affects the quality of the final products and leads to a high level of waste.

Therefore, the moisture present in the recycled polymer aggregates can cause many problems if the raw materials are not properly prepared before casting.

These can be both residual moisture after polymer processing and moisture that hygroscopic polymers absorb during storage or transportation. As a result, not only the appearance of the products, but also their technical characteristics, strength and durability are affected.

To buy all kinds of plastic dryers and other industrial peripheral equipment, contact our experts through contact methods.

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