A large number of industrial materials and food products can be dried using microwaves. It is the fastest, effective, non-invasive, contactless technology. It can be combined with other methods, such as vacuum methods (a sample publication is available here).
Depending on the type of material or product, the water it contains can deposit only on its surface or be inside. Water is in the form of droplets, it collects in small depressions, it is between packages or grains of material and is found in capillaries.
During drying, microwaves penetrate the material or product. Hitting water particles, they heat them, causing them to evaporate. Water vapor, squeezing out, gives off some heat to the surrounding material, increasing its temperature. When drying process using microwaves, the material is not heated, but only the water contained in it. Thanks to this, during drying the material has a much lower temperature while maintaining high process efficiency.
Lack of waterproofing, damaged insulation, water supply system failures, damaged roof sheathing, leaking gutters or fire brigade activities are the most common causes of excessive moisture in foundations, walls and building structures. Most of the water in building structures (walls, partitions, foundations) is in capillaries and small depressions. 1m3 of a brick wall can absorb over 200 liters of water.
Air dryers or heaters only dry the wall surface. Water from inside must flow to the surface itself. The effectiveness of such actions depends on the room volume, climatic conditions and the amount of fresh air flowing in from outside.
The microwave method does not have these disadvantages. The microwaves penetrate deep into the wall or foundation. The evaporating water is forced out. The wall is dried in its entire volume and not only on the surface.
There are no hazards associated with damage to foundations, electrical or water installations because the wall temperature does not have to exceed 100 oC.
Plastic granules can be divided into non hygroscopic and hygroscopic. The former include, for example, PS, PVC, PE or PP. In their case, moisture mainly settles on the surface. However, most technical plastics have hygroscopic properties. Water not only stays on the surface, it is also inside the granulate.
In industrial processes, it is extremely important to ensure the quality requirements of granules, which also include maintaining humidity at the appropriate level. Drying hygroscopic materials due to their structure (fine grains) and sensitivity to higher temperatures is a difficult and energy-consuming task.
The latest methods of drying granules are based on microwave technology assisted by reduced pressure. All thermoplastic materials are virtually "transparent" for microwaves. If there is no water in the granulate, the microwaves do not cause its temperature to rise. If they penetrate the granules and get into the water, they cause it to evaporate. The type of material does not matter, the efficiency and effectiveness are always high.
Drying using microwaves can be assisted by vacuum. At reduced pressure, the evaporation temperature of water is much lower. Using this phenomenon, you can dry the material at an even lower temperature.
Drying vegetables, fruits and herbs
Food products are characterized by a high water content, and a significant reduction in moisture content is indicated in many processing operations.
Drying kinetics depend on the product and expected quality after the process. Regardless of everything, the most important thing is to preserve the nutritional value and appearance. The use of microwaves for drying meets these conditions.
Microwave technology is flexible enough to be able to precisely select technical solutions tailored to a given product and process. The process itself is also carefully controlled and regulated at many levels (speed, size, power).
There are no contraindications, and it is even recommended to combine microwave technology with other methods. A good example is puffing. It is a method of drying fruit under vacuum and low temperature. Water is removed from the fruit and vegetables, making them crunchy. At the same time, they retain their nutritional values, shape, smell and are even similar in size.