Views: 8 Author: Site Editor Publish Time: 2020-07-06 Origin: Site
Veneer dryer is an important equipment on the production line of plywood. Therefore, choosing a high-quality veneer dryer is the first job for enterprises. This article will introduce you to the types and selection techniques of veneer dryers.
Types of veneer dryer
Selection skills of veneer dryer
(1) For the common classification of veneer dryers, the heat transfer to veneer can be divided into the following types:
Air convection veneer dryer: It transfers heat to the veneer through hot air convection to dry the veneer, such as various mesh belt dryers.
Contact veneer dryer: It uses hot steel plates to contact with the veneer, and directly transfers heat to the veneer to dry the veneer. For example, the hot plate dryer that is being developed abroad has its advantages: the dried veneer is flat, the thermal efficiency is high, the drying speed is fast, and the energy saving is more than 36%.
Radiant veneer dryer: Use microwave, infrared (including far infrared) and other radiant energy as a heat source to dry the veneer.
Among them, microwave energy is a kind of electromagnetic radiation energy. The commonly used microwave frequencies for wood drying are 915 MHz and 2450 MHz, and the wavelengths are 0.328 m and 0.122 m, respectively. The microwave drying mechanism is usually explained by the microwave electric field causing the arrangement of dipolar water molecules in the veneer, which rapidly rotates with the electric field, causing friction to generate heat and evaporate water. Due to the limited technical conditions and the high cost of microwave drying, the single board drying is rarely used in microwave drying.
Infrared (including far-infrared) is also an electromagnetic wave. Their wavelength is 0.76 to 400 microns. They have the characteristics of ordinary light, and can be radiated, oriented, penetrated, and absorbed into heat. The characteristic of far infrared ray is that its wavelength is basically the same as the wavelength of the molecular movement of wood and water, both in the range of 3-16 microns, so far infrared ray can form a strong resonance with the molecular movement of wood and water. It absorbs heat radiation energy, so the far infrared ray drying board has higher thermal efficiency than ordinary infrared ray.
The use of electrical energy to generate infrared and far infrared rays consumes too much energy. Boron compounds, carbides, metal oxides, etc. are formulated into coatings according to a certain proportion, and coated on the surface of the heater to make infrared radiation elements, which can be heated by steam, direct combustion gas, etc. and this a more economical method. At present, infrared veneer drying is still in the test. Some people abroad believe that infrared dryers heated by combustion gas may be used in large quantities.
(2) The veneer dryer can be divided into two types: roller veneer dryer and mesh belt veneer dryer according to the veneer transmission method.
At present, the most common application in China is the convection heat transfer mesh belt dryer and the compound heat transfer drum dryer. Hot plate dryers with contact heat transfer are rarely used.
The mesh belt dryer has a simple structure, is easy to manufacture, and consumes less steel. The jet-type mesh belt dryer has the advantages of fast drying speed, lateral feeding into the board, and drying after shearing process. Its shortcomings are: the flatness of the veneer after drying is poor, the mesh belt is easy to run off and damage during operation, and the maintenance workload is large.
The veneer dryer has a flat veneer, good quality, reliable equipment operation and low maintenance. The disadvantage is that the equipment is more complicated to manufacture and the steel consumption is more than the existing structure of the drum dryer, which can only be longitudinal Into the board, and the thickness of the veneer must be more than 1 mm to pass smoothly.
(1) Purchase veneer drying equipment must firstly understand its own actual situation. It specifically includes the size of the lignite drying site, the number of tons of lignite dried in an ideal range, the humidity of the existing lignite, and the selling price of the lignite dried products.
(2) The lignite drying experts of regular manufacturers should be consulted seriously and asked to provide you with the most professional lignite drying cost analysis and common knowledge of veneer drying equipment.
(3) Try to go to the physical manufacturer of the veneer dryer manufacturer as much as possible. If necessary, you can bring your own raw materials. Can your material be dried to the desired level.
As we all know, the quality of the equipment will directly affect the efficiency, quality and a series of cost expenditures of the production process. Therefore, I hope that this article can bring you some help in choosing a veneer dryer. If you have other questions, you are welcome to pay attention to our website for consultation.