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The drying specialists GMF-Gouda manufactures drum dryers in a wide range of test models, even up to 6 metres long. The applications for this technology are divided between two large industries: the food industry and the chemical industry. |
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Realising the future vision Our technology is developing further and further: our third generation of drum dryers has been realised.
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How does the GMF-Gouda drum dryer work? The drum body of the drum dryer is heated on the inside by steam. A special composition of cast iron gives the drum a combination of favourable properties: very accurate shape retention even at high steam pressure and temperature, and excellent "scraping properties", which are utilised by the scraping knife. Steam heating gives a uniform temperature distribution over the drum surface and this results in consistent product quality. The steam condenses on the inside of the drying drum. The condensate is continuously removed from the drum, so that the largest possible surface area remains available on the inside of the drum for condensation of the steam. The steam system is a closed system, which means that the product cannot come into contact with the steam or condensate. |
 Design of the drum dryer with underlying application roll |
Depending on the design of the drum dryer, the product is applied continuously as a thin film on the underside or top of the main drum. As the drum turns and is heated on the inside, the product dries on the outside of the drum dryer. The short exposure to a high temperature reduces the risk of damage to the product. The water or solvent evaporates and leaves the process at the top. If necessary, the vapour can also be suctioned off locally around the drum. The dried product layer finally reaches the knife and is scraped off. |
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Indirect (drum drying) is more economical Efficiency In contrast with indirect drying on a drum dryer, a large quantity of hot air is necessary for "direct drying" in order to achieve evaporation. In indirect drying, heat is transferred by, for instance, steam to the (metal) wall, which in turn transfers it to the product on the other side of the wall. All the heat transferred by the wall is also used to dry the product and does not leave the machine or chimney unused. This makes indirect drying a much more efficient process. An extra advantage is that large dust recovery systems (such as filters) are no longer necessary due to the absence of drying gas. |
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Drying drum According to our experience, only specially-composed cast iron can lead to high-quality drum drying. The graphite particles in cast iron ensure for a "lubricating" course of the knife on the drum surface as the product is scraped off. The uniform hardness and homogeneous structure ensure that the drum retains its shape under high temperatures and high internal pressures. An extremely accurate roundness and wall thickness guarantee very even heat transfer. Chromed drying drums can also be supplied in order to meet the demands on hygiene or corrosion for specific applications. |
 Extremely accurate roundness and wall thickness for the most uniform heat transfer |
 Special knife holder for optimum scraping properties |
Knife holder The well-thought-out construction of the knife holder guarantees an even pressure over the total length of the drum. The use of specific materials prevents vibrations as a result of scraping and guarantees uniform product removal. The pressure of the knife can be controlled simply and this is done outside the process area. |
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Separate process area In the design, a clear distinction is made between the process section of the dryer and the mechanical parts. This, for instance, prevents the risk of contamination by lubricants (or contamination of the lubricants due to leakage of the product). It also improves the accessibility of parts for adjustment, inspection and maintenance. |
 Separation between the process section and mechanical parts |
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The unique advantages of a single drum dryer ...with overhead application drums With the system of application drums, the product supply can be controlled simply. Furthermore, the application drums create a kneading effect that prevents the formation of lumps in sticky products. A perfect distribution over the entire length of the drum makes the system ideal for processing doughy or pasty products. |
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...with an underlying application drum A model developed for targeted applications and chemicals. In this machine, the application drum is under the main drum. It picks up a fluid layer of product and brings it onto the main drum. This process is characterised by short drying time and minimum product heating. |
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...with a front-mounted application drum For processing certain heat-sensitive products, a front-mounted application drum is often the most obvious solution. |
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The extra capacity of a double drum dryer |
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A double drum dryer, also called dual drum, is often used for products with low to medium viscosity. In this system, the product is fed into a pool between the two drums (which always turn in opposite directions). The small space between the drums can be set accurately so that a desired film layer can be obtained. |
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Drum drying under vacuum A drum dryer that operates under vacuum allows the product to be dried at lower temperatures. There is a wide range of applications, including damage prevention to heat-sensitive product components or evaporation of solvents at low temperatures (the vapours are collected and can be condensed elsewhere). |
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Independence from atmospheric pollution and climate conditions ensures for a reproduceable product quality. Foods can benefit from such careful treatment. Evaporation takes place within a few seconds without risk of oxidation. In this way, the enzymes and proteins in the food are preserved and blockage of proteins prevented. The end product can be dissolved easily into a liquid. Chemical products, too, can go into the dryer from a vacuum process and undergo the drying treatment. It goes without saying that, if necessary, a protective gas such as nitrogen can be used to keep the environment inert. |
 vacuum with a fully heated casing |
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Dual drum vacuum dryers These drum dryers provide a higher capacity and less product loss under vacuum. Two steam-heated drums turn in an air-tight casing under high vacuum. The liquid is fed between the drums from the top, dried and scraped off before the drums have fully rotated. In the GMF-Gouda vacuum drum dryer there is no accumulation of product residues and no recirculation of the material. The drum dryer can be easily accessed for inspection and maintenance. Most important applications for vacuum drum drying: |
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Pilot plant ensures process data GMF-Gouda has an extended database containing knowledge and experience of a large number of products. The pilot plant can be used for products that have not been tested before or for existing processes that need further improvement. All processes can be simulated in our laboratory. The reliability of the simulations is proven by the success of hundreds of installations worldwide. In certain cases, tests can be done at the customer's site. Mobile test machines can be leased for that purpose. |
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Test facilities Feasibility test We need a small amount of product in order to determine whether it can be drum dried. Manual test For the manual test, we need about 1 kg of product in order to determine its behaviour on a test drying drum and to produce a small sample. Guarantee test To perform a guarantee test, we need between 50 and 100 kg of product in order to determine the capacity and the process parameters. On that basis, process guarantees are granted and a comprehensive report is made. |
 Section of the pilot plant where products are tested |