spray Drier with fluidized bed drier

specifications and working of two stage spray drier with fluidized bed drier installed in experimental dairy,national dairy research institute,karnal,haryana

1. PRACTICAL ASSIGNMENT PRESENTATION TOPIC:- TWO STAGE SPRAY DRIER WITH FLUIDIZED BED DRIER DE-221 DAIRY PROCESS ENGINEERING COMPILED AND SUBMITTED BY:- SUBMITTED TO:- BISHAL BARMAN ER ANKIT DEEP 17-B-DT-10

2. The removal of nearly all the water through vaporization is known as drying or dehydration . Although these terms are used inter-changeably, drying is removal of moisture to a moisture content in equilibrium with normal atmospheric air. Dehydration is the removal of moisture to a very low moisture content, nearly bone dry condition. WHAT IS DRYING ?

3. SPRAY DRYING Transformation of feed from a fluid state into a dried particle. By spraying the feed into a hot drying medium. Considered to be one of the best methods . Applied to fluids of high moisture content and high viscosity. Short drying period.

4. BASIC WORKING PRINCIPLE First milk is pumped through atomizer. Milk is split into fine droplets. Droplets are subjected to a stream of hot air flowing Dry powder particles fall down towards the bottom of the chamber from where it is removed. Large liquid surface is created by atomization so evaporation takes place very quickly at a low temperature. Hot air supplied to the feed heat the droplets and carry away the vapors' evolved .

5. METHOD FOR ATOMIZING SPRAY MATERIAL   1. Hydraulic pressure jet 2. Pneumatic 3.Centrifugal disc METHOD OF FURNISHING HEAT: 1.Steam 2.Gas 3.Fuel 4.Electricity METHOD OF HEATING AIR 1. Direct (gas or fuel oil) 2. Indirect (utilizing heat exchanger plate or coils. DIRECTION OF AIR FLOW IN RELATION TO PRODUCT FLOW 1. Counter current 2. Parallel 3. Mixed PRESSURE IN DRIER 1. Atmospheric 2. Vacuum SHAPE OF DRYING CHAMBER 1. Flat bottom 2 Conical bottom  CLASSIFICATION

6. CONSTRUCTION & WORKING Air filter : Incoming air is washed by drawing it through a spray of water or through a series of screens of wire mesh. Air heating : Steam/oil/electricity is used for heating air. Saturated steam of 10-12 bar gives an air temperature of 170-180° C. Atomization :-   Hydraulic Pressure Jet Type :- In this type, the original form of atomizer forces the milk at a high pressure ~ 141­211kg/cm2 through a very small orifice, which may be only 0.125 mm in diameter, in hard steel disk. Drop size is not uniform, Drop size reduced by increasing the pressure, reducing the nozzle diameter, or reducing the liquid, but this type of atomizer is unsuitable for producing a large proportion of drops below 30µ  diameter.

7. Pneumatic Type stream of compressed air is used to disintegrate a jet of  milk. - air impinges at high velocity onto a film of liquid at right angle. - more concentrated liquid can be processed. - not used for size range exceeding 50 µm. Centrifugal Type - No pressure is applied to the milk, - velocity is imparted by centrifugal force in rotating device. - feed breaks up into umbrella like spray

8. Drying chamber : Drying chambers are designed to discharge the majority of the product at the base or to convey all the product with the exhaust air to a product separation and recovery unit. Rotary valve: It is a pump like assembly located at the bottom of cone of the spray drier or the cyclone. It helps in maintaining vacuum inside drier and conveys the dried powder downward with each rotation. Manhole : It is a type of door which allows a person to go inside the drying chamber. Hammer : Hammers have been provided at the cone wall outside the spray drier. The hammer strikes the powder deposited on cone wall. fig: Drying chamber fig: Rotary valve fig: Hammer fig: Manhole

9. 1 st stage drying Air at temperature ( 180-220 C ) moves into and through the drier at a velocity from 360 to 600 m per min. The greater the velocity, the more likely the product will be carried from the dryer. Residence time is 10-30 seconds . 2 nd stage drying:(static fluidized bed dryer) The second stage is a fluid bed built into the cone of the spray drying chamber. This fluid bed is called the integrated fluid bed. Here drying occur for 2-3 minutes and hot air upto 90 C is used for drying.

10. 3 rd Stage Drying(VFBD) The powdered products are made to flow through a permeable support on which material, when gas is passed through grid. At greater velocities the particles in the bed will begin to be in turbulent motion. A further increase in the stream of gas finally leads to a velocity at which the particles float, which occurs when the upward force equals the force of gravity acting on the particles. In the first section, the powder is dried to its final moisture content by air at 60-90 C and in the second section, the powder is cooled by air at approximately 30 C. Here chilled water is used for cooling air(4-10˙C) and air should be dehumidified before using otherwise it will give its moisture to powder. Then steam is further used for heating at desired temperature. Time for drying is 10-12 min . Powder dried to 6-9 % moisture in main drying chamber is taken to <4% moisture in vibro fluid bed

11. Cyclone separator: Cyclones are centrifugal Particle separators. It employs centrifugal force rather than gravitational force to remove the particles. In cyclone separator air at high velocity is introduced tangentially into a cylindrical vessel which has a much larger cross section than the entering duct. Instantizaion : In experimental dairy 3 stage spray dryer has a blower and heater for air supply present at bottom of cyclone separator so that fines that we have collected can either be used for agglomeration or when there is no need of agglomeration then they are supplied to heating chamber of vibro fluidized bed dryer. Fan requirements for spray dryer: - Air supply fan - Exhaust air fan - Transport air fan (agglomeration) - Cooling fan - Air heater fan

12. Moisture content after final drying: Powder dried to 6-9 % moisture in main drying chamber is taken to <4% moisture in vibro fluid bed. This reduction in main drying chamber outlet air temperature of 10-15 C giving an outlet temperature of 80-85 C compared with 95 C in two stage drying. Results of multistage drying: Higher quality powders with much better rehydrating properties directly from the drier Lower energy consumption Increased range of products which can be spray dried Smaller space requirements

13. SEPARATION OF POWDER FROM AIR As the product is dried, it is necessary to separate the dried product from the air. Without special design features, the  product will be carried by the moist air from the drier. It is necessary to remove the particles (a) To get a maximum yield from the dryer by saving all  powder product. (b) To avoid air pollution surrounding the drying plant.

14. Fig:- Cyclone Separator Fig:- air supply fan

15. Fig:- vibro fluidized bed drier

16. LINE DIAGRAM OF TWO STAGE SPRAY DRYER WITH FLUIDIZED BED DRYER

17. Care and maintenance All gaskets must be changed periodically. Avoid the use of high pressure steam . Ensure heating surfaces are clean and free from deposits. Condensate must be removed properly from the heating surface. Check the air leaks which may develop around valves,joints,cover.

18. ADVANTAGES OF SPRAY DRYER The whole process proceeds very rapidly and the air residence time in the chamber is up to 30 s . And drying is accomplished at low temperatures. There is no oxidation, loss of vitamins, denaturation of proteins, lactose transformation and other adverse effects of heat. For these reasons, spray drying is also used for drying of different pharmaceuticals, biological substances and thermo sensitive materials. The product obtained by spray drying is similar in quality to the product obtained by freeze drying . During spray drying, it is possible to automatically control the drying parameters and by this, to control the properties of the final product such as final moisture and temperature, bulk density and powder particle size. The process is fully automated , so that even high capacities with high productivity require minimal labor. Since the product comes into contact with the wall of the closed chamber only in the powder form, there is neither a problem of equipment maintenance or corrosion nor a problem with the microbiological quality of the final product.

19. DISADVANTAGES Very large dimensions of the drying chamber. Expensive equipment. High electricity usage. Steam consumption. High installation cost

20. CONCLUSION Effective process control is essential if dairy powders and concentrated products are to be manufactured safely, in compliance with regulatory requirements, with acceptable product quality and low manufacturing costs. The key to success is the elimination of external disturbances. This can best be accomplished by careful design of the services infrastructure. Particular attention should be directed to steam, hot, cold and chilled water, compressed air and condenser cooling towers.

21. Sources: E-course (NDRI) Dairy plant engineering and management by TUFAIL AHMAD Internet Class notes