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Main Advantages of the Microwave Heating

  • Speeding up: minutes instead of hours!!
  • Volume Energy transmission - cold vessel
  • ENERGY Savings, Room Savings
  • Efficiency 70%
  • Automatization
  • Safety *
  • Environment *

Comparing to the processes using the combustion


REFERENCES

  • PRODUCTION FLOW
  • MINIMUM SPACE
  • ELIMINATION OF DEFECTS
  • SHORTER TIME - TENS OF MINS, NOT DAYS
  • ENERGY IS USED EXCLUSIVELY FOR THE REMOVAL OF MOISTURE  

Drying of technical and handmade ceramics


For technical and handmade ceramics

SILICATE SLURRIES CONTAIN UP TO 25% OF H2O
After forming of half-finished products by casting, soaking, pressing, turning and pulling, the mentioned volume of water must be reduced to the values which allow firing. A properly and efficiently dried body does not feature any impermissible geometric deviations or cracks and the applied method does not require any unnecessary ancillary expenses.



PROGRESSIVE MICROWAVE DRYING
Unlike ceramic material, water absorbs electromagnetic radiation. It is heated evenly in each depth of the product wall. Pressure grows with temperature; the pressure displaces water molecules to the surface, where the pressure is lower. Microwave power can be controlled precisely and appropriately with regard to the kind of raw material, the size, shape and thickness of walls and the current water content. Therefore rapid evaporation is sufficiently gentle, even at risky places and stages. The stress between the surface and the inside is none; no deformations occur and energy consumption is optimal at each moment.


TRADITIONAL OPEN AIR DRYING
Resting of formed intermediate products in adjacent racks is time-consuming. In addition, it it safe mostly for small products and products with low plasticity. Delicate half-finished products are put to rooms with lower temperature and high relative humidity. Packing into vapour-permeable membranes causes condensation on the inner side of the package, therefore water running down must be controlled because of macerating and collapsing. After moulding, the process on the respective item is interrupted for a long time. The in-process store is not desirable because of the occupation of production area which can be used more effectively or which did not have to be built at all. The costs of ventilation, humidification, cooling and heating are related to storage. Under primitive manufacturing conditions without systems of air conditioning, the weather, direct sun, the distance from the source of heat and airflow play a significant role. In manufactories, residual moisture, which can occur in unacceptably high values for firing at critical places of bodies, is not usually determined precisely. For acceleration, a part of moisture is removed in the burning oven. There is a risk of destruction after the conversion to steam, whose volume is 1000-times larger than the volume of liquid water. Careful and gradual start-up to the firing temperature is necessary. This stage must be verified experimentally for products with different thickness of the wall, raw material used, and so on. From a certain amount and complexity of production, the optimum combination of low costs and high quality of ceramics production cannot be achieved.

DISADVANTAGES OF OPEN AIR DRYING
  • Interruptions in production flow
  • Spatial demands on the in-process store
  • Non-productive utilization of capacities    
 
CONVENTIONAL HOT-AIR DRYING
At first, the air, then the actual material and eventually the target water are heated. The surface is heated up as the first and it shrinks before the cooler inside. The resulting tensile stress on the surface causes cracks. Heat does not act deeply as it does with microwaves; the pores inside the wall do not open, thus they fail to facilitate the diffusion. The porosity of technical ceramics reaches very low values, for example if it does not exceed 5%, it is vacuum-tight ceramics. The surface pores narrow upon over-drying, or they close and the moisture cannot leave. In hot-air chambers, there can also be a one-directional airflow to the body, resulting in uneven shrinkage. Unacceptable stress can be shown on the example of a plate with already shrunk particles of a dried thin disc on the edge. Since they do not move, they cannot equalize pressures at shrinkage of the still damp centre. After crossing the critical stress, the brittle dry disc cracks. The detection of optimum drying modes for specific shapes is demanding with the convection systems. Temperatures, delays, moisture and airflow are affected by complexity, dimensions, material and the immediate moisture of bodies. The increase in productivity hits the physical limits accompanying the heat passage and transfer to the flowing medium. The solution is the dielectric heating principle, which is used by microwave technologies.


DISADVANTAGES OF HOT-AIR DRYING
  • Long production times
  • Higher occurrence of deformations and destructions
  • Only a part of energy for heating of the air
  • Is used for reduction in moisture  
 
MICROWAVE CHAMBERS TAILORED TO THE SPECIFIC RANGE OF TECHNICAL CERAMICS
The industrial, precision and engineering ceramics are alternative terms for specialized products with unique mechanical, electrical, thermal and biochemical properties and their combinations. Thanks to their resistance to heat, wear and tear, abrasion, corrosion, etc., they withstand considerable loads and they maintain their functions with long-term durability. They are applied in a number of industries: mechanical engineering, metallurgy, forming and moulding, electrical engineering, chemical industry, energetics, paper industry, automotive, aviation, health care and measuring technology. They include various shaped pieces, such as filters, sieves, linings, heating elements, insulators, casting equipment, supports, casings, sleeves, tubes, nozzles, probes, terminal blocks, plates, rings, bushings, laboratory equipment and others. Silicates, mainly the ones based on natural raw materials, are the oldest and still widely used materials in technical applications. In this category with traditional production procedures, the drying operation is often the key to the successful result. The optimum is to achieve water removal in a short time for the smooth transition from the previous forming to the subsequent firing. For large and highly plastic materials, the reduction in the production time, which prolongs the lengthy common drying, is desirable. The efficient lot production requires low costs, out of which the operating costs are heavily influenced by energy consumption. With new construction, the investment demands for the production area are also decisive. Small and precise range places demands upon the compliance with the dimensional tolerances. For top delicate products with a high added value, it is desirable to prevent defects. The microwave technology, from the actual physical nature of the dielectric method of heating, is destined to meet the mentioned set of requirements. The efficiency of the microwave chamber located in a small area consists in the speed of drying with low energy demands and/or in labour savings. This principle is also friendly to quality assurance.

TYPE MICROWAVE DRYING CHAMBERS FOR INDUSTRIAL AND DECORATIVE CERAMICS
Low-capacity drying ovens are applied mainly in workshops with a high proportion of manual craftsmanships in the manufacture of ceramics: art, figurative, decorative, stove, garden, stoneware, pottery and china. In addition to the acceleration and improvement of the production before firing, the immediate microwave heating, which usually does not exceed 10 minutes, is used for pre-drying. Thus the required “coriaceous” consistency is reached; the consistency, unlike the surface “crust” made by the hot air, maintains opened pores and mainly more passable capillaries inside the wall. This is the optimum condition allowing also intermediate operations, such as retouching, gluing of handles and so on, and the acceleration of the ongoing drying to the firing moisture. In manufactories, if they have not invested in drying ovens, the shaped half-finished products rest on shelves and their drying is finished in the burning oven. From a certain amount of pieces, a number of staff and at the parallel work on more varied assortment, there is a need to decide whether to develop the business. It is just the absence of a drying chamber which is a bottleneck for productivity increasing. Its acquisition is a matter of quite a simple calculation of return. The point is that ceramists assess the fact that microwaves allow them to put the already dried half-products to the firing oven within one hour according to their situation. The matter becomes clearer if there are spatial limits for the expansion of production or if there are non-productive times and the workload of the staff can be more efficient.

PARAMETRES
ROmiLL BATCH DRYCER
small
medium
large
Length
600 mm 800 mm 1300 mm
Width
600 800 1300
Inner height
700 700 900
Total height
1800 mm 2000 mm
Design
stainless steel
Input power
1.5 kW 3 kW 6 kW
Weight
160 kg 210 kg 420 kg
Certification
 (or according to local legislation)
Control system
control of manual settings of parameters*)

*)PLC on request