GMF-Gouda drying equipment for the Potato and Starch industry
Product quality and shelf life
Removal of water is a method to increase the shelf life of food-products. Depending on the composition, the final moisture in the product has to be reduced to different levels.
Products with components having polymer-like structures as proteins and carbohydrates (starch) do not have to be dried to low levels for a good shelf life in the same extent as products which mainly consist of smaller molecules (i.e. sugars), that are often thermoplastic and / or hygroscopic.
Drying methods have been developed taking the special behaviours of the various products into account. Examples are: sun drying, hot air drying, drying on hot surfaces. For a more economical drying process, products are sometimes partly dewatered by filtration, pressing or evaporation prior to the final drying stage.
For more than a century, food products have been dried commercially. In the beginning, the systems were quite simple and adapted to just one type of product. Most of these drying systems did not generate products of good quality and required a high energy consumption, as well as much manual labour.
During the years, the various systems and installations have been improved, resulting in products with better quality and a longer shelf life in combination with less energy consumption. Simultaneously the equipment-capacities have been increased.
Product categories
Liquid:
Certain products become available as a liquid. Pre-concentrated products in the low viscosity ranges are often treated in a spray dryer, whereas (next to low viscous products) the more viscous products like pre-gel starches and gelatines are dried on drum dryers. Both spray dryers and drum dryers have their specific advantages and product-applications. In this field the well known GMF-Gouda Drum Dryers are applied. An important application on drum dryers is, although it is not liquid in this case, also the drying of potato mash to instant potato flakes.
Paste:
Other products are becoming available as a paste which are too viscous for spray-drying and sometimes not suitable for drum drying in case of non adhesion to the drum surface. This category of products is processed via direct or indirect dryers which are equipped with agitators to refresh the drying surface. The drying time for these products can vary a lot in dependence of the composition and the design of the equipment.
For these products GMF-Gouda offer their Paddle Dryers.
Cakes:
The third category is the group of products available in the form of cakes, where the majority of the water is present on the surface of the small particles. Typical examples of this category are filter cakes of starches and slurries of crystals. In this case the drying time can vary from a few seconds to some few minutes. Depending on the product either the GMF-Gouda Paddle Dryer or the GMF-Gouda Flash Dryer can handle the product.
Particulates:
A special category is formed by particulates of natural products as, for example, peanuts, soy beans, cereals ( rice, wheat, corn ) and vegetables ( onions). These products do contain often sheets, that are more or less impermeable for water, or in which the water is strongly bound. In order to maintain the quality, the temperatures for heat treatment should be kept low. As a consequence, the drying must be very moderate and therefore low temperatures are applied during long periods.
The GMF-Gouda Spiral Flash Dryer
GMF-Gouda developed an extensive experience in the field of drying in its more than ninety years existence as supplier of process-equipment. Thousands of their drum dryers are in use all over the world. In the food industry they are applied with great success for, among others, drying of dairy products like milk for the chocolate industry, cereal based baby foods and pre-gel starches from various sources.
GMF-Gouda extended its program in dryers by the introduction of the GMF-Gouda Paddle Dryer in the 1970's. This indirect dryer is especially suited for the treatment of the above described products in the paste and cake-categories. Its application is not only in drying or cooling of products, but also in heat-treatment for thermal modification of dry material such as flours and starches.
In more recent years, GMF-Gouda introduced a very flexible direct type fluid bed / flash dryer for the starch industry. This air dryer has, compared to existing fluid bed and flash dryers, a unique design resulting in special flow of air and product described hereafter:
THE TOROIDAL MOTION
The flow of air through a fixed blade-ring
gives a toroïdal particle motion
Air flows through the slots between the blades
making the product particles move as a spiral
The special designed blade-ring
located in the cylindrical process chamber
The unique toroïdal motion realises an intensive mixing with air, guaranteeing homogeneous product-treatment and fast processing. Product, e.g. starch filter-cake coming from a vacuum filter, that is dosed continuously from above, falls onto fast circulating product already present in the process chamber. In the case of flash drying, the dry product will leave as a fine powder through a central opening in the top section of the process chamber and is separated from the air in via a cyclone.
This GMF-Gouda dryer has the following characteristics and advantages :
CHARACTERISTICS
ADVANTAGES
High inlet-velocities
Able to fluïdise even large particles
Low final velocities
Controlled fines-elutriation
Adjustable airflow
Able to handle a large "Particle-size-distribution"
Toroïdal motion
Even product-treatment
Densely packed bed through rotational forces
Excellent heat & mass transfer
Cyclone action
Controlled particle flow
No moving parts
Safe in operation; wide temperature-range can be applied
Compact in size
Can be placed in a building; easy to insulate; little thermallosses, little need for construction steelwork and civil work
A maximum air velocity around the product particles is guaranteed, as during the rotational motion in the process chamber the product is continuously accelerated in different directions. This motion results in excellent transfer of heat and fast processing (both in drying and cooling). In consequence of this phenomena, higher inlet temperatures, lower outlet temperatures and bigger temperature-differences can be realised than conventional air dryers. Lower product temperatures are an advantage for heat sensitive products.
Installations, with in essence the same design, can, next to drying and cooling in a continuous downward flow of the product, also be applied for ultra flash drying.
The flow-sheet below shows the set-up of the installation with the combination of drying and cooling.
TWO - STAGE SYSTEM CONTINUOUS DRYING AND COOLING
The installation has no moving parts, is very compact, maintenance and inspection-friendly, and is a sanitary design suitable for CIP ( cleaning in place).
Due to its flexibility regarding temperature, many different heat-treatments can be applied for food products, such as inactivation of enzymes, sterilisation of spices and herbs, toasting of breadcrumbs and cereals and drying of rice, filter-cakes (starches), potato granules and slurries (sugars).
For filter-cakes, like in the production of native starch, GMF-Gouda offers the Spiral Flash Dryer concept.
The filter-cake continuously drops in a rotational airflow above the blade-ring in the bottom of the process chamber.
GMF-GOUDA SPIRAL FLASH DRYER
Dry, light product particles release from the wet product rotating above the blade ring in the process chamber. The dry product particles exit the chamber with the process-air in a spiral flow upwards through a central opening in the top section of the process chamber. Next, product particles and air are separated in a powder-air separation unit, i.e. cyclones.
GMF-Gouda has its own technical centre to test on its pilot-equipment the various product of their clients. Next to the food-industry the different dryers GMF-Gouda offers, are also applied in the chemical, the pharmaceutical and the environmental industry.
