FLUID PROCESSES AND ROTOFLUID® SYSTEMS
With respect to the processing of loose material blown-through by gases from below the fluid processes enable the layer of loose material to expand and act as a boiling liquid (it holds the level, flows, and each particle of the solid material exercises free motion limited only by the walls and bottom of the equipment, and by the system level). Visually, the fluid process reminds a system of constantly emerging and perishing fountains. The processes feature such advantages resulting from perfect and uniform contact of the gas with all particles of the loose material that the fluid technique is more and more used in all industries, and new possibilities of its application have been arising.
ROTOFLUID® I - A FLUID SYSTEM WITH ROTATING CHAMBERS - Fig. 1 (59 kB), Fig. 2 (46 kB)
The system of chambers rotating inside the vessel, having the shape of vertical cylinder or cone, controls the holding time of the material being processed. The system operation is continual and ensures the same holding time for all particles of the material being processed. The holding time can be controlled within a great range. ROTOFLUID® I is successfully used for a wide range of processes applied in the chemical, pharmaceutical, and food industries, and other branches where lightly fluidised materials are required.
ROTOFLUID® II - A FLUID SYSTEM WITH ROTATING STIRRER - Fig. 3 (58 kB), Fig. 4 (76 kB)
The ROTOFLUID® II system does not have standard geometrical arrangement like other types of fluid equipment; its working space is formed by a horizontal half-cylinder, and the free motion of particles of the material being processed is ensured by action of combined forces of the flowing gas and rotating mechanisms. The gas flow velocity can be lower than the threshold velocity of fluidisation, which provides for a longer time of phase contact and reduces small particles outlet.
The first advantage of ROTOFLUID® II is that it enables to process such a material that cannot be processed in another type of equipment (both fluid and non-fluid) at all, or only with difficulties. ROTOFLUID® II can process sticky materials, sludge, solutions with low content of dry matter, crystalline material the crystals of which have a shape of long needles, and heterogeneous mixtures of particles (e.g. a mixture formed by wooden dust and chips).
The second advantage of ROTOFLUID® II is the already mentioned longer time of contact of the flowing gas with the material being processed, which considerably increases heat exchange, or chemical conversion. In several cases we have reached a power saving of up to 30% when compared with other types of fluid equipment. This advantage is also evident at processing of lightly fluidised materials.
The ROTOFLUID® II systems can be operated in both batch and continuous mode.
ROTOFLUID® II TWIN - A ROTOFLUID® II SYSTEM WITH DOUBLE WORKING SPACE - Fig. 5 (56 kB)
The operating mode of ROTOFLUID® II TWIN can be described as a two-floor fluidisation featuring many advantages and with the possibility to accomplish the operations that have not been mastered yet. ROTOFLUID® II TWIN is the latest achievement of our development in the area of fluid technology.
AN EXAMPLE OF THE USE OF ROTOFLUID® II AS A DRIER
The basic principle of fluid drying is the following: in the fluid system the wet material is blown-through by hot air or another gas flowing from below through the perforated bottom of the working space of the system. The contact of the particles of wet material with hot drying fluid is perfect, which facilitates and accelerates heat transfer and increases the utilization of enthalpy of the drying fluid for evaporation of the liquid creating the moisture of the material being dried. This is evidenced by the fact that the prevailing part of water is evaporated at a temperature of 35 - 45°C even though the drying air inlet temperature is 130 - 150°C or even higher.
The working space of ROTOFLUID® II is formed by a horizontal half-cylinder with perforated bottom part that is equipped with a stirrer installed along the axis of the half-cylinder. This design enables to work at velocity of the drying air that is lower than the threshold velocity of fluidisation, and to dry materials that do not fluid at high flow velocities of the drying air (e.g. sludge, pastes, etc.).
In addition, it is possible to dry in a very careful way at a temperature of the drying air of 40 - 45°C, if required for preserving the high activity of the material being processed (typically in pharmaceutical industry).
APPLICATION POSSIBILITIES OF THE ROTOFLUID® SYSTEMS
Driers of powder and crystalline materials, granulates, extruded substances, pastes, sticky substances, sludge, solutions with low content of dry matter; it is possible to use air, overheated vapours of a solvent moistening the dry matter, or inert gas (in circulating atmosphere) as drying fluids. Examples: sugar drying, soup mixtures and meat mash drying, drying and sterilization of mill products (e.g. children's semolina), casein and whey drying, malt husks and siliceous earth drying, drying of stillage, drying of waste from fish processing, poultry processing and from slaughterhouses (including blood drying), placenta drying, eggs blend drying, drying of sludge from waste water treatment plants, drying and sorting of coal and anthracite slurries.
Coolers and freezers, e.g. for the freezing of vegetables mixes, while preserving their loose condition.
System for production of instant granules by spraying water into a layer of freely moving particles, e.g. for the production of instant cocoa drink.
System for treatment of particles by spraying of fat, chocolate, etc., e.g. for the production of muesli.
Reactors for chemical processes up to a temperature of 600°C (also in the circulating atmosphere of water steam, nitrogen, hydrogen or another gas), e.g. for debittering of soya, for hydrothermal starch breakdown in cereals and legumes, for partial reduction of iron oxides.
The ROTOFLUID® systems are available in 19 sizes, with an active area ranging from 0.04 m2 to 12 m2. Larger systems can be manufactured upon request.
LOW-TEMPERATURE DRIERS OF CEREAL SEEDS, SEEDS, SEED CORN, SPICES AND MEDICAL HERBS
LINE FOR AFTER-CROPS TREATMENT OF CEREAL SEEDS IN A LOW-TEMPERATURE DRIER WITH HYDRAULICALLY TILTING GRATES - Fig. 6 (61 kB)
The line is intended for after-crops treatment of cereal seeds, including malting barley. In addition to cereals, it can process (without an additional modification of the system) grass seeds, flax, cucumber and tomato seeds, chamomile, peas, beans, soya and other similar agricultural products.
The basic requirement is to preserve nearly 100% germinating capacity. This is ensured by a low, accurately controllable drying temperature (typically 40 - 50°C). The drying fluid consists of a compound of flue gases and air. The technological regime is adapted to the product being processed. For instance, grass or rape seeds, which are relatively small and thus have a great specific area, are dried in a continuously flowing heat transfer fluid. However, legumes have quite a different drying regime; with respect to the size of their beans it is necessary to enable the moisture to penetrate from the bean centre to its surface that is dried relatively fast. This is achieved by interrupting the heat transfer fluid flow for a certain period of time, or by a simple removal of the heat source.
The line consists of two independent parts, which enables a simultaneous treatment of two different products. The products to be processed are transported by vehicles and unloaded into two separate receiving tanks made of concrete which are located under the ground level. These receiving tanks are designed so as to avoid mixing of different kinds of cereal seeds. From the tanks the products are transported using two elevators into four overhead steel tanks with a size of 4 m x 4 m, and a volume of 45 m3; the total capacity of these tanks is 180 m3. From the steel tanks the products are fed to pre-cleaning machines, and using two other elevators they are transported into four tanks located above the tilting grates of the drier. The volume of each tank is 25 m3, so it is possible to store 100 m3 of wet products. All tanks are sized so that the products transported in the afternoon may be processed during the night shift, and all the storage facilities should be empty and ready for the receipt of new products in the morning.
The core of the line is a low-temperature drier with four hydraulically tilting grates, with a size of 4 m x 4 m, and potential product charging up to a height of 50 cm. (This refers to a typical system. The number of grates can vary depending on the capacity requirements of the customer). The drier grates are charged by direct falling down from the tanks with a volume of 25 m3. They are discharged by tilting that is controlled hydraulically like the opening of front walls. Charging and discharging of the grates is accomplished very fast, so there are no time losses during drying.
The heat carrier is produced in two heat units. The liquid fuel burners are installed tangentially to the shells of combustion chambers. Their fireclay lining that is subject to fire impingement in helices provides for catalytic combustion. Before the odourless flue gases enter the fans, they are mixed with air in such a ratio that is required by the respective drying mode. The heat carrier is supplied by a distribution system under individual drying grates.
After the grates have tilted, the dried out product falls down into two concrete tanks located under the ground level. From these tanks it is transported using two elevators to other cleaning and sorting machines. Then, it is supplied to the shipping containers and to the packing equipment to be packed as requested by the customer. The line can be equipped with store-rooms, containers, high-lift trucks, etc.
The described line is especially intended for treatment of cereal seeds. It is possible to deliver both larger and smaller lines, and lines specifically designed for selected kinds of seeds, as well. These feature adapted air supply and feeding systems. As an example we can mention the line for wet treatment of pre-treated tomato and cucumber seeds with an inlet moisture of approx. 60%, sugar beet and radish seeds, seed onion, gladioli bulbs and the other assortment of seed growing. The products can be dried either in bulk on individual grates or on pallets with specially designed bottoms.
LINE FOR AFTER-CROPS TREATMENT OF SEED CORN AND OTHER CEREAL SEEDS, AND SEEDS - Fig. 7 (72 kB)
Seed corn is of special importance in the wide range of seed growing products. Its physical properties are only little suitable for the process of drying (the seed weight to whole cob weight ratio as well as the cob surface to cob weight ratio are small); the moisture from the cob centre does not penetrate fast to the surface. The limit temperature of drying is about 42°C; higher temperatures have a harmful effect on germinating capacity. The corn layer puts a relatively small resistance to the flow of drying fluid, which is much smaller than that of the layer of other seed growing products of the same height. The equipment for after-crops treatment of seed corn has to pay attention to these unusual properties, and at the same time it has to ensure both a high germinating capacity of the product and an economic efficiency of the drying process.
The basic feature of the line for after-crops treatment of seed corn is a special construction of the low-temperature drier. Seed corn is dried in 3 meters high layers inside the system of chambers. The chambers are interconnected using air piping so that the layers of corn are blown-through by the heat carrier alternately from below upwards and from above downwards, i.e. in suitable cycles corresponding to the optimum conditions of heat and material transfer. In addition, the heat carrier flows though more than one chamber of the drier. Besides, the chambers can be put out of the drying process in suitable technological intervals for a time period required to compensate the reduced moisture of grains to the higher moisture of cob inside. In addition to the seed corn, the line can process practically an unlimited range of cereal seeds and seeds (rape, cucumber, radish and grass seeds, cereal seeds, and legumes). These seeds are dried in layers with a height of 30 - 150 cm (depending on the respective kind). The drying temperature is precisely controlled; in most cases it falls within the range of 40 - 45°C. The level of germinating capacity is high. The line operation is fully mechanized, charging and discharging of chambers is done hydraulically by tilting of chambers.
The line is usually installed in a steel structure workshop with a size of 72 m x 18 m x 10 m. The workshop has 12 fields, and is divided into three working areas; in the first area there is a receiving part of the line, the second one comprises the technological centre - a low-temperature drier (with adjacent machine rooms - heat stations, switch room and central fuel store-room). The third working area is the pre-shipping facility of the line. The workshop is connected with a storage and shipping area to ensure dispatch according to the specific requirements of customers.
The line consists of two independent parts located along the longitudinal axis of the plant, which enables simultaneous treatment of two different products. The seed corn to be processed is transported by vehicles to the receiving part of the line and unloaded into two separate receiving tanks made of concrete and located under the ground level, or onto feeding tables. Then, the seed corn is supplied using belt conveyers to automated leaf stripping units. The removed leaves are transported using belt conveyers out of the workshop. The cobs intended for further processing are transported using wide belt conveyers to horizontal belt conveyers supported by a steel structure. Individual chambers are charged using travelling regulators from a height of approx. 5 m (always four chambers from one belt).
The technological centre - a low-temperature drier - consists of two independent systems of chambers, each of them has four chambers with a size of 4 m x 4 m x 3 m. Hydraulically tilting drying chambers are made as frame structures welded from rolled profiles and covered with two layers of plates with an insulation layer from foam polystyrene between them. The inside surface of these sandwich structures is covered with sheet foil to ensure perfect air-tightness of the chambers operating under a minor overpressure. The chambers are charged from above, and discharged from below by both gradually opening the hydraulically controlled front faces in the lower parts of the structures and tilting the whole chambers around pairs of pins using the same hydraulic system as front faces. The chambers are equipped with horizontal grates. The layer being dried has the same height in all parts of the chamber, and the heat carrier flow is uniform. The grate structure is statically sized for loadings by a 3-meter high layer. As for the air supply, the chambers are interconnected so that the heat carrier may flow alternately from below upwards and from above downwards. They can also be connected in series to ensure perfect use of the drying fluid enthalpy. The used fluid is transported through outlet channels outside the workshop. This prevents from water steam condensation on the inside walls of the workshop, and corrosion of the steel structure of the workshop and its plate shell.
The heat carrier is prepared for each of the two parts of the line separately in special areas adjacent to the longer sides of the workshop. At one side of the workshop, there are a switch room and an oil system. Thus, each part of the line has its own machine room - a heat station with two medium-pressure fans and two combustion chambers. The flames of the burners connected to the central storeroom of liquid fuel are led tangentially to the hot fireclay linings of the combustion chambers where catalytic cracking and complete combustion of the fuel take place. This process of combustion, which has been showing satisfactory operational results for a long time, provides for odourless flue gases. The flue gases are mixed with atmospheric air in a ratio of approx. 1:15. After the flue gases are mixed with air, the line will only operate in the range of low temperatures with high operational safety. Temperatures and automated cut-off of the burners are controlled using sensors installed in suitable locations of the low-temperature system.
The dried corn is transported from discharging chambers by belts located at a height of about 1 meter to the pre-shipping part of the line. This third working area of the workshop is equipped with two shellers where the last phase of cob treatment takes place. Corn cobs that have fallen down are transported using horizontal belt conveyers out of the workshop. The dry corn grains pass through a cleaning system, and are stored inside four underpass containers. Other packing and shipping machines and storerooms can be delivered and provided according to specific conditions and requests of the customer.
The line equipment is controlled from a central control room. The receiving and pre-shipping parts of the line are operated according to the operators conditions, one or two shifts daily; in every case the drier is in permanent operation. Three persons ensure the line operation, besides there are personnel who operate sorting tables.
The considerable advantage of the line for after-crops treatment of seed corn is its full utilization for practically unlimited assortment of other seeds, which increases the time utilization of the line. In addition, it is possible to use the drier chambers as a blowing force during the time when the line is not used for drying.