Dryers are intended for technological drying of material, where, in addition to water, solvent emissions may also be created.
They are used in wood processing, insulation material production, asphalt concrete base production, the concrete industry, paint industry, sintering industry, the pharmaceutical industry and others.
“Only the technologically most advanced dryers work like NATURE – strive for BALANCE. ”
Dryers are equipped with at least one air flow ventilators (a ventilation system), burner system, moisture derivation system, fresh air supply, transport system so material can be transported to and from the dryer In regards to the mode of transport of the materials, dryers can be chamber or continuous.
“Changing conditions or transport during changing conditions – CHAMBER or CONTINUOUS DRYERS.“
In a chamber dryer, the drying process occurs in the same area from start to finish, whereas in the chamber dryer products are transported in different stages of drying. Chamber dryers are well-suited for the production of a large selection of products in smaller series, that do not call for a continuous production process. Continuous dryers, on the other hand, guarantee continuous production and are intended for drying larger series of products. Continuous devices are more energy efficient.
The drying process
- Drying is the process in which moisture exists products, mainly water at first and finally other particles (should they exist).
- The water evaporates from the surface, during which there needs to be a difference in the air and surface moisture for the moisture to transition from the surface and be released into the air.
- As nature always strives for balance, humidity transitions from the area with higher humidity to the area with lower humidity. This is why with our technical dryers we make use of the fact that the air will allow for different humidity levels depending on the temperature. Thus, for example, the air is saturated with 49.52g at 40°C (X absolute moisture), with 87.52g at 50°C and with 1459g at 90°C.
“Do you know the processes behind successful drying? EVENNESS and ACCELERATION.”
- The drying process is made up of two complementing processes: water vapour from the surface and the transition of water from the inner towards the outer surface
- Drying is successful only when the two processes take place uniformly
- The allowed speed of drying is based on the structure of substances being dried
- With certain non-sensitive materials drying can take place faster, whereas others may take longer to dry
- Once we are conscious of the importance of both processes, drying itself can be accelerated (especially with the material that takes longer to dry)!
Diffusion
The image shows diffusion (the “water bubble” path) towards the surface of the plate. Using the entire surface of the plate we blow the hot air and so the “water bubbles” are released into it the air
“Will you avoid the most common drying mistakes?”
When drying raw products, unwanted, usually wide, cracks may appear on a rough surface.
Such mistakes occur as a result of unsuitable conditions and an incorrect drying regime. Products may shrink during drying, caused by pressure created due to the differences in shrinking between the inner and outer mass of the product, which leads to cracks.
Cracks can be avoided by ensuring minimal differences in moisture along the depth product. Balance is maintained by the changing temperature and relative moisture in the chamber.
We can begin the drying process by increasing the temperature and lowering the relative moisture in the chamber; as the shrinking process and the capillary transfer of moisture slows down, the moisture level on the product will drop bellow the critical limit. The speed, however, will depend on the available time and the optimal energy use of the warm air.
The increased speed of drying can lead to products drying too fast around the edges, leading to further deformations of product surfaces. The intervals between the products on the drying shelves can also lead to such mistakes. As a result, there are differences in the level of dryness between the products from the edge of the shelf and those in the middle. This can be solved by increasing the air supply along the entire surface of the drying shelf.
Cracks an also occur in areas where the products and the drying shelf come into contact. This can be avoided by ensuring that the products are placed as closely together on the shelf as possible.
“Ensuring maximum operational safety with dryers using paints and other materials producing solvents DRYING-CURING CHAMBER”
Dryers in which moisture and parts of solvents are released into the air are usually called drying-curing chambers. In addition to fulfilling drying criteria, they also need to adhere to safety regulations.
Should they not fulfil operational safety criteria, such chambers become a safety hazard with a risk of explosion occurring. This is why special attention needs to be given to the fulfilling the guidelines set out by the SIST EN 1539 standard.
“We are now safe from explosions. Standard SIST EN 1539 – Drying chambers and ovens in which flammable compounds are released into the air: safety requirements.”
With special technical measures we can ensure that the concentration of flammable explosive compounds in the drying chamber is at most 25 % MEC (min. explosive concentration).
Special attention is also given to measures guaranteeing that the said limit is not exceeded in states of emergency–e.g. when electrical supply is halted, production stopped, the allowed temperature is exceeded etc.
All these are reason why, as part of monitored security measures, a programmable controller needs to be carefully selected, in combination with other security elements reaching the SIL standards, set on the basis of a security analysis.
Chamber dryer
“For your smaller series. For your limited edition products, tests or individual production. For a better quality, control and your smaller scraps. CHAMBER DRYER”
In a chamber dryer we dry either smaller, limited edition products that differ from others in the large-scale production or pieces from individual production. They are also used to dry concrete products and can be used as lab dryers in tests prior to serial production. A chamber dryer is made up of a chamber entailing an air duct channel with an air flow vent, gas burner, door, outlet channel, fresh air supply, moisture inlet and an electrical enclosure with a panel.
“Solution to dealing with sensitive products.”
Products can be loaded onto a cart that is then pushed into dryer either manually or with the help of an engine. The doors can either be one or two-wing and can be closed manually or automatically. The temperature and moisture curve adapts to the product in the dryer. With sensitive products we offer the possibility of blowing moisture into the chamber or a very gradual increase in temperature to prevent crusts on products.
“What can you gain by investing in a chamber dryer?”
- Improving the quality of products and reducing the amount of scraps.
- The drying process is more constant can be controlled more easily.
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Continuous dryer
“Conveyor dryers, rotary dryers, dryers with transport chains, and transport carts.”
In continuous dryers the material travels through the dryers made up of several zones; in each zone several different physical and chemical processes take place. The dryers differ with regard to the manner the products are transported through the dryer: conveyor belt, transport chains, transport carts or rotary pumps.
“Achieving even material dryness through strict parameter control in the dryer.”
As the goal in the initial zones of the dryer is to raise the product temperature, a high level of moisture of the air circulating around the product is necessary. This increases the diffusion in the product interior onto the surface. In the further zones, the level of moisture in the circulating air increases – as a result the diffusion from the product surface into the air increases as well.
Through proper moisture and temperature parameter control we can achieve the even dryness of materials throughout and prevent the surface of materials from overbaking. Where the goal is the binder polymerization of products, the temperature at which the binder polymerizes and the product takes shape also changes.
To achieve the evenness of products, a powerful, forceful mixing of particles in the atmosphere takes place, with the help of an appropriately powerful air flow vent.
“Saving on the invested energy.”
With continuous dryers smaller energy investments are required per material unit as the dryers do not need to be cooled down and reheated when a new batch is introduced. As the products travel against the current, against the air flow, the products of lower temperature can make use of the higher temperatures in the dryer.
“Technically superior dryer equipment.”
To achieve the required parameters the dryer is equipped with:
- the needed number of gas burners
- temperature and moisture monitors in different zones
- with a moisture outlet system
- built-in recuperative burner to maximize the use of the energy source
- Scada steering system and user panel.
Rotary Dryer
“Going with or against the flow. You can count on the detail and quality production. ROTARY DRYER”
Intended to dry fine material such as balls, chippings, mulch, pallets etc. The materials enter the drum in the front part, they are then heated and finally exits the drum heated through an opening.
The heating can be executed directly – with the burner in the centre of the drum – or indirectly with burners in the jacket.
The air flow travels from the air outlet to the air inlet–contraflow. With non-sensitive drying material such as steel and other metals often times also in the opposite direction. The later dryer can be shorter, however attention needs to be given to the temperature of the end-products, which do not exceed the oven temperature (e.g. the temperature of the conveyor).
Dryer temperature:
od 100-250°C
Nominal material flow:
1500 kg/h, 4000 kg/h, ….
Drying capacity:
800kg/h
Technical data:
Intended for drying aluminium chips
Dryer with Carts
“Prices are in line with the optimal physical process.
DRYER WITH TRANSPORT CARTS”
Drying material moves through the dryer on plates or trays placed on the carts.
Materials travel through several zones adapted to physical processes taking place in the zones. The emphasis in the first zone lies on heating entire products (including their interior), which enables the moisture to move onto the surface.
The surface should maintain the right amount moisture so the capillary transport of moisture remains possible – crusts must be avoided at all cost. In the succeeding zones the level of moisture is controlled and the temperature is raised.
If the products require polymerization, reaction networks or some other chemical process, the temperature in the final zones of the dryer remains constant – allowing for optimal reactions.
The length of the dryer can be determined by the so-called “gentle” method of drying. Thus you will not regret this investment opportunity, as with a slightly increased drying (select: accelerated drying) you can increase the drying capacity by 20 %.
Chain Dryer
“Vertical. With strong air flow vents. Without uncontrolled air inlets. CHAIN DRYER”
Knauf vertical plate dryer
Do to the lack of ground plan surface the plates move through the dryer vertically.
The first and the second zone have lower temperatures.
Strong air flow vents ensure precise drying.
Temperature and moisture control are performed in each zone. We control the inlet and outlet temperature.
By controlling the pressure in the dryer we ensure there is no unregulated entry of outside air.
Due to the lack of space the recuperative process involving the entering of air fresh air is not possible.
Thermal processing ovens
“Industrial ovens constructed according to your wishes, implementing efficient technological solutions with high energy standards.”
Industrial ovens are used in high-temperature processing of raw material that may be in the liquid or solid state of aggregation. They are used in different industries: steel, glass, ceramics, chemical, brick, tyre, metallurgy, sintering etc.
They are used in different heat treatment processes: tempering, normalization, annealing, sintering, nitriding, carbonitriding, baking, tempering, or for heating prior to smithing, pulling, improving the structure of products and altering their physical properties.
Industrial ovens can be classified based on several different criteria, most commonly based on:
- technological purpose (melting, heating, heat processing, sintering, drying)
- heat source (gas, mazut, coal, electricity, no external heat source)
- chamber design (cave, line, rotary, tunnel, chamber)
- based on how the heat from gas emissions is utilized (recuperative, regenerative, without heat exchangers).
However, there are also additional classifications of industrial ovens – e.g.: based on heat transfer, how the oven is loaded, how the heat is re-used etc.
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