Continuous fluidised bed processes

Picture: Continuous fluidised bed plants for curry powder

In the food industry as well as in the fine chemical and pharmaceutical industry, powdery substances serve both as raw materials and as intermediate and final products. Fluidised bed processes can be used in a variety of applications. They reduce the dust content, improve the flow properties and tabletability, and create additional product properties such as rapid solubility in instant drinks or stability of the mixing ratio for maintaining an accurate proportioning.

In bulk production, particularly the continuous fluidised bed processes provide a higher increase in value by reducing operating and production costs. Furthermore, they offer possibilities for developing new products with innovative application properties.

Process optimisation and cost reduction
Powdery substances have to be easy to transport and proportion and have to provide absolute safety in processing.

A very dusty product may lead to high environmental stress and may cause health problems for employees or consumers.

Products made of complex compounds have to remain homogeneously mixed and must not segregate.

Picture: Continuous fluidised bed plant with open exhaust air hood

Therefore a trouble-free and safe production process increases the economic efficiency of the plant and is a decisive factor for the profitability especially in bulk production.

Convenience and product confidence
Functional properties not only simplify the production process, but are also often requested by consumers. For example, granulated or compressed - and thus dust-free - detergent or dishwasher tabs have nowadays practically become standard. In the food industry, additional health benefits as in probiotic foods or convenience products such as instant preparations make products more attractive to customers. The value of final products is also increased by processes such as aromatisation or taste masking.

Furthermore, compliance with the highest sanitary standards plays an important role. On the one hand, national and international regulations require increasingly strictly defined hygiene certificates. On the other hand, in times of transparent and highly linked consumer markets, customers are more and more sensitive to shortcomings in the production process. Within a very short time, the economic survival of a company is at risk if impurities or contamination through microbial growth occur in a product due to insufficient hygiene.

Technology of fluidised bed processes
Fluidised bed processes are highly efficient.

Due to the intensive exchange of heat and material they are ideally suited for the thermal treatment of bulk products (drying and cooling) as well as for the formation of particles from powders (agglomeration) or liquids (spray granulation). The fluidised bed technology has gained acceptance for the production of instant products and of granulates for subsequent compaction.

Picture: Fluidised powder in a continuous fluidised bed plant

Fluidised bed processes can be performed either batchwise or continuously. Fluidised bed plants for batch processing are usually designed cylindrically and vertically.

Their volumetric capacity is limited.

Continuously operating fluidised bed plants are constructed rectangularly and horizontally. They provide a steady material flow, with the powdery starting material being fed in on the face side and finally discharged for example as a dried or agglomerated product with the desired product specification. Due to the horizontal continuous processing, the capacity and the performance of continuously operating plants are virtually unlimited.

Constantly high economic efficiency
Continuously operating fluidised bed plants are ideal for medium to high production volumes. Owing to the high degree of automation, the plants can be operated by a single operator. The application possibilities are numerous: 

• instant drinks
• baby food
• soup and sauce powders
• mixtures for vending machines
• nutraceuticals

The continuous fluidised bed process ensures a very uniform and reproducible product quality. The layer level, which is lower than that in batch processes due to permanent product feeding, provides a more uniform and intensive liquid distribution and thus optimal properties of agglomerates and granulates are achieved.

For this reason, the continuous process is increasingly used even for smaller capacities.

Continuous plants should be designed as a closed system and in compliance with GMP standards in order to ensure optimum sanitary conditions.

They can be integrated into a diving wall, so that a separation of the control room and the installations room is possible.

WIP systems provide almost fully automated plant cleaning.

Picture: Continuous fluidised bed plant integrated into the wall

If a rear section is separated, also smaller batches - for example for testing new recipes or for sample productions - can be efficiently processed in a large-volume plant.

Innovations create new sales opportunities
The fluidised bed agglomeration is a shaping process during which the spraying of liquid components on the powdery starting material causes a change in the fine structure and improved physical properties. During this process, loose, highly porous and therefore easily soluble agglomerates are produced which are required for example for the production of instant products. Fluidised bed granulates are also particularly well suited for subsequent compaction as they ensure a relatively high solidity at relatively low compaction pressures on account of their porous structure.

  Picture: Scheme of agglomeration                             Picture: Scheme of Spray Granulation

The fluidised bed spray granulation represents a variant of the agglomeration process. It is an innovative process for the production of free-flowing, low-dust, compact and almost round granulates with low abrasion from originally liquid products such as solutions, suspensions, melts and emulsions. The liquids are atomised in the fluidised bed and the obtained drops hit the granulation seeds. In the process, the liquid evaporates and the solid builds up in shells around the granulation seed. On account of this layered structure, compact and nearly round granulates are produced.

In the fluidised bed technology there are a variety of intermediate stages between agglomeration and spray granulation in which liquid and solid substances are processed and combined simultaneously in one device. This allows the encapsulation of a liquid or solid matrix as well as the coating of a sensitive core. Especially this option of processing solid and liquid substances simultaneously offers new approaches to innovative product developments. 

Simulation under real process conditions
The efficiency of a fluidised bed plant depends very much on the interaction of different parameters such as process temperatures, air quantities, product layer levels, position of spraying nozzles and binders. Therefore, the product behaviour should be simulated under realistic laboratory conditions with variable process parameters before the plant is designed. In a well-equipped pilot plant the product quality can be optimised and the ideal operating point can be determined for the future production plant.

Neuhaus Neotec
Neuhaus-Neotec Maschinen- und Anlagenbau GmbH is a globally active company specialising in process engineering. With the brand Heinen Drying, Neuhaus Neotec is highly competent in fluidised bed technology. In the new pilot plant, Neuhaus Neotec uses state-of-the-art machines and plants to develop customised fluidised bed processes and recipes for the efficient production of powdery substances in the fine chemical, food and pharmaceutical industries.

© Neuhaus Neotec GmbH / BulkInside