Avantika Dhadwal*, Chandani Thakur, Aniket, Shikha, Priyanka Kumari, Madhu Bala
Department of Pharmaceutics, Himachal Institute of Pharmaceutical Education and Research, Nadaun.
*Corresponding Author E-mail: ranaavantika270@gmail.com
ABSTRACT:
In this review paper we study about the working, construction, applications, types, principle, etc. It is the unit operation which is mostly used in the pharmaceutical industries for the reduction of the moisture content of powdered drug and granules. It is also known as fluid bed dryer. The two situations which carried out in bed dryer are: Spherical and Non spherical particles. The design of Fluidized bed dryer was carried out to diffusivity of the material. The fluidized bed dryer are diverse types due to the flexible nature of the bed which includes well – mixed, plug flow, agitated etc. This equipment is based on fluidization of the feed materials.
KEYWORDS: FBD, Dryer, Fluidization, Moisture, Granulation, Drying.
INTRODUCTION:
In the modern era, there is a lot of equipment utilized for the granulation and drying processes in the pharmaceutical companies. Utilizing such machinery shortens the time, money, and processing procedures required to produce a good1. The working principle of the fluidized bed dryer states that when a gas is passed through a layer of particles on a grid in an upward direction, it will simply percolate through a fixed bed of particles at low flow rates. Once the pressure drop over the particle layer reaches the weight of the particles per area of the bed, the gas velocity increases2 Due to the fluidized particles' enormous surface area, the distributor is the only place where extremely effective heat and mass transfer between the fluidized particles and the fluidizing gas occurs. The fluidized layer and the heating or cooling surfaces can transmit heat well through the gas fluid bed. A barrier that let the dry material to freely flow across it regulates the fluidized layer's height. The fluid bed receives the fluidizing air, which is then sent there to be heated and filled.
An air distributor for fluidizing ensures that the air velocity is distributed uniformly throughout the fluidized layer and that the entire substance has been suitably fluidized3. The most recent technique, known as fluid bed processing, aids in the granulation, coating, and drying of a product so that uniform coating and drying occur. These approaches use a bottom spray, top spray, or tangential spray process as their basic premise. These guidelines are based on where the spray gun is placed within the apparatus. The top spray method aids in attaining uniform palletization or granulation. A Wurster coating device is used in the bottom spray method (Leuenberger) 19901. To optimize the process by learning how the phases are distributed and what sorts are involved, a hydrodynamic analysis of the fluidized bed is essential. In a fluidized bed, a two-phase model consisting of a dense phase and a dilute phase is typically used for gas solid interphase models. Solid motions happen as a result of the emulsion's ability to pass through bubbles and the thermal effects that are reduced. High heat and mass transfer, as well as sufficient mixing of the particles and gases inside the bed, are all attributed to the high turbulence created in the bed. Low-rank coals' high moisture content is a widespread issue that raises transportation costs, could pose safety issues while being transported and stored, and results in sub thermal efficiency when converting in fuels3. It is essential to lower this moisture content to permissible values in order to reduce energy losses, transportation costs, and to improve product quality. The drying characteristics, chemical structure modification, energy requirements, and affecting variables of low-rank coals are investigated. The conventional fluidized bed drying techniques as well as alternative field-assisted techniques, such as microwave, vibration, agitation etc. These dryer are used in powder layer coating using tangential rot granulator to mini tablets and capsules. Bed dryer is useful in the chemicals, pharmaceutical, food dyestuff, industries for several processes. It is based on the drying process to remove the excess amount of the moisture to make a material dry. Particle size is greater than 100 microns for the fluidized and dried. it is also known as FBD because a high pressure hot air passed through the perforated container which contain wet granules to suspending in the air to become dry which is called fluidization or fluidized state. It operate a temperature ranging from: 150C to +6000C (50to 11120F) with gas speed varying from 0.2 to 3 m/sec 5.
Dryers: It is a process of removal of water or other liquids in a formulation with application of heat is known as dryers 6.
1. Tray dryers: It is a dryer used to dry powders, granules by the hot air for the removal of moisture from the materials. (used the material drying in pharmaceutical manufacturing) 6.
2. Drum dryer: It is also known as film dryer. The solution to be dried is conveyed as a film on the surface of the dryer and is then dried to create a layer inside a heated hollow metal drum that spins on its longitudnal axis6.
3. Spray dryer: Using a liquid stream, a spray dryer seperates the solute or suspension into solid from and the solvent into vapour is known as dpray dryer6.
4. Fluidized bed dryer: To lower the moisture level of raw components such as powders or granules, the pharmaceutical industries frequently use fluidized bed dryers6.
5. Vaccum dryers: It is a drying process that encloses the item to be dried in a container, vents the air within and uses a vaccum pump to lower the pressure to artificially raise the water vapour partial pressure difference6.
6. Freeze dryer: Frequently known as lyophilization, this low-temperature dehydration method comprises freezing the product, lowering the pressure, and causing the ice to sublimate. In contrast to dehydration brought on by most conventional techniques, which rely on heat to evaporate water6
Fluidized Bed Dryer: It is defined as the lowering the moisture content of raw components like a powder and granules. It is a type of machinery that is widely employed in the Pharmaceutical industry. Fluidization, which is the process of creating tiny, solid particles that behave like fluids and can freely travel above, slide past, and collide with other molecules, it is done by suspending solid particles in a stream of fast -moving air. D means Dryer: It is the equipment where wet substances are dried.
Types of FBD: There are two types of FBD as follows:
Horizontal FBD: It is also known as the continuous type of Fluidized-Bed Dryer due to the continuous process of drying. The trays containing the material to be dried are loaded onto a moving bed in this dryer. The trays' bases are perforated, allowing hot air to pass through them with ease. These trays move around various chamber surrounded by a planet. There is an air input at the bottom and an air outlet at the top of each chamber. In the pipe that exhausts the air, every outlet is open. Each room receives air supply; however the temperature of the hot air entering each chamber gradually raises basic air in the first chamber, and compressed air in the second chamber. It contain different chamber in which each chamber has air inlet and air outlet at the base and the top respectively. 1st chamber to the 4th chamber in which each chamber have different air like simple air, slight hot air, more hot air or the hottest air. The material is passes from perforation and pushes it like a fluid and after that air is vaporized and granules become dry.
Vertical FBD: It is also known as the batch fluid bed dryer because the whole product is dried in a batch. The fan are present in upper side to initiate the air stream from start to finish material in drying chamber the heat in air heater to rise air in material for the drying. The wire mesh support is installed and bags gather fitted so that all the material are lifted and only air is passes 10.
Fig 2: Vertical FBD
(A)
(B)
1. Hybrid fluid bed dryers: To completely dry the materials, these modified fluid bed dryers use a heat pump mechanism. The mixture aids in accelerating the drying process for the granules. Additionally, it aids in maintaining the quality of the materials.
2. Pulsating fluid bed dryer: When wet, some materials have a tendency to stay together. It will be challenging to separate them since they combine to form a solid mass. The fluidization method is difficult to apply to such materials. In such situations, a modified fluid bed drier is employed.
3. Vibrated fluid bed dryer: It is also known as vibrating fluid dryer, they are designed for materials with long particles that allow a stream of hot air to penetrate through the dryer.
4. Spouted bed dryer: These fluid bed dryers were created to lessen material loss, which is typically noted during the drying phase of production. It mostly utilizes coarse grains.
5. Fluidized bed freeze dryer: It works on a fluidization of the materials.
1. Batch fluidized bed dryer: It is suitable for the material which requires drying in the decreasing rate drying zone.
2. Continuous fluidized dryer: A continuous flow of "wet" powder, granular, or flakes material is carried over a perforated bed in a continuous fluid-bed system. A perforated plate has holes that are filled with hot drying air. Wet solids are elevated from the bottom and begin to behave like fluids as a result.
3. Semi continuous bed dryer: It is common used for material processing. This method of drying involves simultaneously charging and releasing the material from the fluid bed dryer. However, the drying procedure goes on for a predetermined amount of time. When you want to change the volume of the materials to be dried, these machines are perfect.
4. Plug flow fluidized dryer: One of the earliest varieties of fluid bed dryers, it has long dominated the pharmaceutical and chemical sectors. Both grains and soluble goods like salts and ions are treated with it. Particularly in instances where there isn't an ideal material flow, the approach makes use of the dispersion theory. It is known as plug and flow because it can forecast both the size of the finished products as well as the appropriate degree of moisture content that the final materials should have. Then, in order to follow the forecasts, it will operate within certain temperature ranges.
5. Well mixed fluidized bed dryer: These continuous fluid bed dryers frequently feature unique designs to support particular material kinds. For drying hygroscopic materials, they are mostly utilized. Materials like this collect moisture from the air and condense 7.
The principle is based on the Fluidization in which air is flow through a bed of solid material in the upward direction with the velocity is greater than the settling rate of the particles and this is due to the particles to blow up and become suspended in the air steam. The solid bed look the boiling liquid and hence known as fluidized. It is a granular material which is converted from a static solid state to a dynamic state, the centrifugal force to produce granules.
It contains a stainless steel chamber which have removable underside which is known as bowl. It contains air handling unit, product vessel, control panel, air distribution, exhaust filter, blower, spray nozzle, and solution delivery. The dryer's removable bowl, which is used for charging and discharging, is located at the bottom. The upper section has a fan to circulate heated air. The dryer's bottom is perforated, allowing hot air to pass through the granules throughout the drying process. The granules rise to the top of the air stream and suspend there. Another name for it is fluidization. The material is dried consistently by surrounding the granules with hot air once they have reached their full drying temperature. The fresh air input, pre-filter, and heat exchanger are gradually connected to heat the air to the proper temperature after the hot air and exit air temperatures are monitored.. The bag filters used for the recovery of fines which is set down above the drying bowl, the air flow is modify through recirculation control and fabric bags equipped to prevent the progress of fine particles. During fluidization the pharmaceutical powder produce electrostatic charges during the end of drying process. The different ranges are: 5 kg to 200kg with average drying time are accessible: 20 to 40 minute. It operate at temperatures ranging from= -150C to +6000C (50 to 11120F) with gas speeds varying from 0.2 to 3m/sec4.
Fig.3. FBD
WORKING:
After the material is put within the bowl vessel to dry, the heaters start the air from the top and heat it to the lowest possible temperature. Between the particles and the densely packed bed of immobilized cells, air will rise. When on high, it passes through a prefilter that the heat exchanger heats up. Hot air flows through the bowl's bottom while a fan rotates at the same time. As a result of the fan's rotation, the air velocity increases somewhat, settling the granules and keeping them partially suspended in the gas stream. Granules then rise in the container due to their rapid velocity following a drop back in a fluidized or boiling state. The dryer's gas surrounds the granules for drying, and air exits via a bag filter's end. The bags shake to release the particles that have adhered to their interior surfaces. For the purpose of drying, the residency period is 40 minutes. The item is removed from the dryer to reach room temperature. Granules rise and then return to their fluidized state. Gas surrounds the drying granules and escapes through the bag filter. The particles are stuck together, and they need forty minutes to dry. Following, the bowl is pulled out for discharge.5
1. It is used for drying materials such as granules, tablets, powders etc.
2. It is used in production industry such as chemical, pharmaceutical, food, dairy, dyes etc.
3. Mixing, granulation, and drying are three operations which can be used for fluidized bed dryer.
4. It is altered for coating of granules.
1. It requires less time to complete drying (20 to 40 minutes).
2. Thermal efficiency of fluidized bed dryer is 2 to 6 times greater than tray dryer.
3. No hot spot on the product is observed.
4. The handling of fluidized bed dryer is easy.
5. The minimum fine drying is 0 to 4mm and maximum is 0to 6 mm.
6. The fluid bed dryer are cooled at 40 to 450 C.
7. The length of dryer /cooler is 8mm and volume of exhaust air is 34000m^3/h.
8. It gives high output from a small floor space.
9. There are different sizes of FBD are available according to their drying capacity ranges from 5 to 200 kg per hour.
10. They reduce the employee cost due to their simple use.
1. Pipes and vessels walls are grind down due to collisions of particles.
2. Particle disintegrate is common.
3. It causes attrition in some materials of fluidized state of granules because of turbulence.
4. The main disadvantage is possibility of product loss.
5. The size of particle is moderately large.
6. It is difficult to predict a non –uniform flow pattern.
7. It is difficult to predict the bubbling bed if fine particles and are less efficient.
8. The organic powders develop electrostatic charges during drying.
9. Fine particles may turn into entrained and should be composed by bag filters.
10. Sticky material is quite difficult 8.
1. It is used for dry the material such as: Granules, tablets, fertilizers, powders etc and used in production of chemical, food industry, diary industries, pharmaceutical and nutraceutical industry etc.
2. Production of multi –particulate systems (solids or liquids) and for the small particles to fabricate.
3. For require heat and mass transfer to the food material which rapidly reaches to fluidization.
4. Remove moisture in many different sizes and capacities.
5. Pharmaceutical powders are granulated using this method.
6. Fluidized bed coaters are frequently used to coat powders, grains, tablets, pellets, and beads suspended in air.
7. Collision between particles and against particle walls on regular basis.
8. High level of intermixing of the particulate phase.
9. High relative velocities between the fluid and the dispersed solid phase 9.
SCOPES:
FOOD INDUSRTRY: It is used to lower the moisture content of products and granules for food processing, preservation, and dehydration. It is utilized by the fertilizer industry to dry inorganic fertilizers, like those with a calcium base.12
NUTRACEUTICAL INDUSTRY: In order to get appropriate moisture content in the tablet formulation granules needed for ideal tablet compression, it is utilized in the granulation process to dry the material.13
METALLURGICAL INDUSTRY: By enabling the drying materials whole surface to be suspended and thus exposed to the air,dryers with FBDtechnology boost efficiency.If required, this procedure may also be coupled with heating or cooling, contigent upon the applications requirements.14
Creation of accurate mathematical models to represent continuous fluidized bed dryer for drying.
Offer a multivariable control system that can effectively handle drying operations.
Create a state observer to calculate the essential controlled variable or solid moisture content.
The moisture content of food products is greatly reduced by fluidized bed drying, which also increases energy and energy efficiency, has a hydrodynamic impact, and uses less energy throughout the drying process. The main implication of FBD over the traditional dryer for drying of food agro –product. Fluidization improves quality, efficacy and texture of food products with a major decrease in moisture content. The product is fine and uniformly dried where the product is hygienic and the operation method is easy and simple to production of boosting the food. It is most attractive dryer with their beneficial result and their advantages. The temperature is uniform and controlled precisely12.
1. Pusapati RT, Rao TV. Fluidized bed processing: A review. Indian Journal of Research in Pharmacy and Biotechnology. 2014 Jul 1 ; 2(4): 1360.
2. Joshi S, Kamat R, Bk L. To study and understand the process of wet granulation by fluidized bed granulation technique. International Journal of Research in Pharmacy and Chemistry. 2017; 7(3): 232-8.
3. Si C, Wu J, Wang Y, Zhang Y, Shang X. Drying of low-rank coals: A review of fluidized bed technologies. Drying Technology. 2015 Feb 17; 33(3): 277-87.
4. Dawange BS, Pawar SS, Surawase RK, Maru AD. Applications of fluidized bed processing: a review. World Journal of Pharmaceutical Research. 2018 May 27: 414-20.
5. Bodhanwalla H, Ramachandran M. Parameters affecting the Fluidized bed performance: A review. REST Journal on Emerging Trends in Modeling and Manufacturing. 2017; 3(1): 17-21.
6. Subrahmanyam C.V.S, Thimmasetty J Mrs. Suresh sarasija, Mrs.. Devi Kusum V, 2nd edition (pharmaceutical engineering) Page no: 286-31
7. Soponronnarit S, Pongtornkulpanich A, Prachayawarakorn S. Drying characteristics of corn in fluidized bed dryer. Drying Technology. 1997 May 1; 15(5): 1603-15.
8. Bizmark, N., Mostoufi, N. Fluidized bed drying, In Drying of Foods, Vegetables and Fruits – Volume 3, Ed. Jangam, S.V., Law, C.L., and Mujumdar, A.S., 2011, ISBN- 978-981-08-9426-9, published in Singapore, pp. -63-88.
9. Mukesh Gohel, Rajesh Pankh, Amiral Poput, Ashutosh Mohapatra, Bhavesh Barot, Chetan Patel, Hardik Joshi, Krishnakant Saevaiya, Pritesh Mistry, Punit Parejiya, Ramesh Parmar, Stavan Nagori, Tushar Patel. Fluidized bed system review or the pharmaceutical articles.
10. Jordan University of Science and Technology Chemical Engineering Department “Modeling and control of continuous fluidized bed dryers “By Mohammad AL-HAj
11. Haque N, Jangam SV, Mujumdar AS. Life cycle assessment of drying systems. In Handbook of Industrial Drying. 2015 (pp. 1229- 1238). CRC Press New York, USA.
12. www.nupharmamachine.com/types of fluidized-bed-dryer-application uses features-advantages-disadvantages.
13. https://www.lodhapharma.com/important-application-fluidized bed dryer in various industries.phpp.
14. http:// en.m.wikipedia. org/wiki/fluidized –bed.
Received on 22.11.2023 Modified on 27.12.2023
Accepted on 20.02.2024 ©Asian Pharma Press All Right Reserved
Asian J. Pharm. Tech. 2024; 14(2):147-152.
DOI: 10.52711/2231-5713.2024.00026