Fluidized bed dryers are industrial dryer equipment that is used for drying of accumulated granules and particles employing a fluidized bed of particles that are in a gas or air stream. Drying process takes place when heated air or gas is passed through the material in question; the material behaves like a fluid. It provides quick heat and mass transfer and has fewer drawbacks of spoiling the end products during the drying process as well. This type of equipment is wide spread in such industries as pharmaceuticals, food processing and chemical production because of good results when has to do with the handling of the materials and the control on the temperature and humidity of the air.
What is a Fluidized Bed Dryer?
A fluidized bed dryer is an equipment used in industries for drying of solid particles, which are in a granular form. It works by heating air and passing this through a layer of matter where they get picked up and start acting like a fluid. It has the overall effect of extending the number of surfaces which the drying air comes into contact with, thus improving heat and mass transfer. Applications of fluidized bed dryers can be observed in many industries like pharmaceuticals, food processing and chemicals because of the efficiency, uniformity in drying and versatility of the equipment to handle both large and small materials and moisture content.
Mechanism of Fluidization
Fluidization is the process of converting a packed mass of solid particles in to a fluid like structure by passing a fluid whether it is in the liquid or gas phase through it. The upward flow of the fluid applies a drag force on the particles to counter act the force of gravity in an economy. At a particular velocity of the fluid called the minimum fluidization velocity, the particles are lifted of the bottom and start to flow like a fluid.
This leads to increased flow energization, augmentation of the interfacial area for the chemical reactions, and an improvement in heat and mass transfers, thus making fluidized beds to be applied in several chemical processes, combustion and material handling procedures.
Types of Fluidized Bed Dryers
There are several types of fluidized bed dryers, each designed for specific applications and materials:
1. Batch Fluidized Bed Dryers:
These dryers are used where small amounts of material are to be processed at one time, and where some variation in performance is permissible. They are best suited for pilot plants as well as laboratory facilities.
2. Continuous Fluidized Bed Dryers:
These dryers are ideal in applications that may require a vast batch of materials to be processed simultaneously through continuous features. It is used in all industries that demand high production rates.
Drying Process and Techniques
Fluidization of a solid material can be done using fluidized bed dryer as a means of drying granular or particulate materials. In this technique the material is heated and the hot air or gas is passed through it in the upward direction and the particle behaves as fluid. This fluidization helps in easy heat and mass transfer, minimizing area of contact of the product with the hot air and thereby avoiding thermal injury to the product.
Since the air temperature and air flow rate can be set variably, the characteristic features of the drying process depending on the type of material can be controlled. Depending on volumetric or cubical production, different varieties of fluidized bed dryer can be used, whether batch or continuous. Further enhancements of the basic concept include in-line sieving or recirculation of the air within the conveyed material flow. In general, it may be said that fluidized bed drying is most appropriate for uses that require delicate treatment of the material, short drying time, and uniformity of the final product.
Uses of Fluidized Bed Dryers
Pharmaceutical Industry
Pharmaceutical industry employs fluidized bed dryers in their processes of drying various products such as granules, powders and pellets. These characteristics make them suitable for the processing of delicate materials such as the active pharmaceutical ingredients or APIs since they allow uniform drying of the particles while preventing particle agglomeration and heat damage. They maintain the quality of the products and also improve the dissolution of drugs by obtaining the correct degree of moisture content.
Food Industry
In the food industry, fluidized bed dryers are used for drying fruits, vegetables and grains, nuts and seeds as well as granules, powders and mists. They contribute to maintaining the nutrient content, taste, and appearance of food products while being efficient in eliminating moisture. The quick drying cycle reduces the chances of bacterial development thus enhancing the shelf life of the processed food, making the fluidized bed technology widely applied in food industries.
Chemical Industry
These are used in the chemical industry to dry large volumes of powders, catalysts, and even chemical intermediates. Its heat transfer properties allow for fast drying which is important since chemicals are more effective in their original state. Since the heat is uniformly distributed within a fluidized bed, there are minimal chances of localized areas heating up or hot spots hence minimizing product degradation.
Agricultural Products
In agriculture value, the fluidized bed dryers apply on seeds, grains, and some other agricultural products to be dried. This technology ensures fragile nature of the products are not damaged while ensuring optimum removal of moisture. The outcome is improved quality and improved stability of storage of coffee that in turn can meet the market demands as desired by the farmers and processors.
Biomass Processing
Fluidized bed dryers are also used for drying materials in biomass operations like drying of wooden chips, saw dust and agricultural products. This application is vital in the enhancement of energy content of biomass fuel, and thereby increasing its utility in energy generation. The uniform drying contributes to achieving the required combustion parameters of biomass fuels and satisfies the requirements of current legislation.
Mining and Minerals
In the mining and minerals sectors, the application of fluidized bed dryer consists in drying ores and mineral concentrates. This enhances the efficiency of downstream processing and transportation as most of the moisture content packed materials have reduced weight and size. This also helps to reduce clumping of the minerals and to maintain all the desired properties of the mineral that the controlled drying climate provides.
Fluidized bed dryers are among the most efficient and elaborate types of dryers used in several industries for drying particulate materials. Kerone, is a leading manufacturer and supplier, has a great deal of responsibilities in besting these systems. An improved comprehension of the concepts and methods required for its operation will allow companies to optimize the drying process and thus maintain product quality while keeping energy expenditure to a minimum. More capabilities and better performance in Kerone’s fluidized bed dryers will be achievable in the future with addition of automation and control strategies to advancing technology in the future.