FLASH DRYING PLANT

Exhaust Air

Cyclone

Drying Duct

Cold Process Air

EXCLUSIVE FEATURES OF FLASH DRYING PLAN

• Reduced running cost.

• Continuous production machine without human touch.

• Ideal replacement for tray drying of wet cakes.

• Extremely sticky /pasty wet cake can be handled.

• Particle size as fine as 500 mesh is achievable.

• Low residence time – minimum exposure to heat – retains original pquality.

• On line particle size reduction-eliminating need of separate pulveriz

• No product degradation or charring.

• Proprietary design of disintegrator ensures uniform mixing of wet cagiving consistent and homogeneous powder quality.

Wet Cake In

Product Outlet

Exhaust Air

Bag Filter

Schematic Diagram of Flash Dryer

Hot Air Generator

T

roduct

er.

ke and hot air

• Fully Automatic – needs little running attention.

• Negligible material dusting.

• High volume processing.

• Large filtering area of Bag filter – reduced pressure drop – large savings in power consumption of blower.

• Measurement of pressure drops at various places facilitates easy trouble shooting and maintenance.

APPLICATIONS:

Our Flash Dryer is a versatile machine and ideal for wet / pasty press cakes. We list below industries where it can be used. Chemicals - Inorganic & Organic

Pesticides and Agricultural Chemicals

Dyestuff and Pigments – Organic & Inorganic

Fertilizers

Mineral Ore Concentrates

Technical Ceramics

Food Industry

Pharmaceutical Industry

Agricultural extracts

TYPICAL PRODUCT LIST OF FLASH DRYER APPLICATIONS Irish Potato Starch B.H.C. Rubber Chloride Powerful Bleaching Powder Ammonium Chloride Clay Magnesium Hydroxide P.V.C. Sugar Beer Yeast Coal White Lead Potassium Chloride Melamine Dicyandiamide Gypsum Clay for Tiles Wheat Starch Sweet Potato Starch Medicines Diatom Earth Fish Meal Fire Clay Materials Benzol Peroxide Bean Curd Refuse Silica Powder D.A.P. Silica Terra Alba White Kaolin Rayon Sulphate of Soda A.B.S. Resin Ammonium Sulphate Clay & Sand Rubber Lignin Ammonium Phosphate Vinyliden Chloride Vinyl Chloride Sodium Sulphate Calcium Carbonate Calcium Formate Polycarbonate Copolymer Polypropylene Synthetic Resin Terra Alba Nissil Sodium Bicarbonate Activated Terra Alba Polyethylene Powder Extinguisher Sodium Cyanide Chemicals Acrylic Resin Flour Rubber Aging Preventive Sulphate of Soda Chrome Ore Polypropylene Baking Powder Potassium Nitrate Glutem Corn Skin Manganese Dioxide By-product Sulphate Ammonia Potassium Bicarbonate Rayon Sulphate of Soda.

WORKING PRINCIPLE OF FLASH DRYER Flash dryer is a continuous drying plant used for drying variety of wet cakes by disintegrating wet cake into fine powder and dried by hot air to form powder. The whole process is fully automatic requiring no handling or human involvement. The feed rate is adjusted automatically as per the variation in moisture content in wet cake thereby achieving consistent product quality. The principle of Flash Drying is to evaporate surface moisture instantaneously. The word “flash” is used, as the drying time is very less from milli to few seconds. It is well known fact that the surface area of wet lump increases as the size of lump decreases. The wet cake is disintegrated into fines to increase the surface area. The drying is instantaneous and the material remains at wet bulb temperature of air. Hence it is also called as "wet bulb drying". The air velocities are similar to that of pneumatic conveying. The powder remains suspended in air and gets conveyed while drying. Hence it is also called as pneumatic dryer. The retention of a given solids particles in the system is very short, typically in seconds. These make it ideal for drying heat sensitive, easily oxidized, materials that cannot be exposed to process conditions for extended periods. Our flash dryer is energy efficient, requiring no intermediate material handling. It is a continuous production machine suitable for pasty / sticky wet cakes. These unique features make it ideal replacement for conventional tray and rotary drying.

• Wet cake is fed in feed mechanism. The feed mechanism consists of balance

tank, stirrer and screw feeder. • The stirrer feeds the screw feeder. The screw feeder gives controlled feed at

rated capacity to disintegrator. • The air after passing through Air Filter is heated in Oil fired hot air generator or

steam / thermic fluid based radiator. • Hot air and wet cake get thoroughly mixed in the cage mill type disintegrator.

Disintegration and drying of wet cake takes place in disintegrator. • Wet cake is rapidly dried and about 50% drying take place in the disintegrator. • Drying duct conveys the pulverized material to cyclone. Drying gets completed in

conveying duct. • The time taken by disintegrated powder to travel through drying duct is called

residence time of drying. • The material looses moisture that is absorbed by hot air. The temperature of air

reduces while its humidity increases.

• Powder is further dried in cyclone. Separation of dried powder and air takes place in cyclone. Powder is discharged from cyclone through powder discharge valves.

• Fine particles escaped from cyclone are conveyed to bag filter. • Bag filter recovers the fine particles. The air coming out of bag filter is dust free

and confirms to pollution control norms. • Two blowers, one at inlet & other at outlet, working on Push-Pull principle

maintain the airflow in the system. • Push-Pull principle ensures that the ambient pressure is maintained at feeding

system to avoid dusting of material. Also it avoids extreme pressures (either positive or negative) in the system.

• The powder collected from cyclone and bag filter can be pneumatically conveyed to storage bin or bagging section.

MAIN COMPONENTS OF FLASH DRYER 1. Feeding Mechanism:

The Feeding Mechanism feeds the wet cake steadily in metered quantity. The entire feeding mechanism as depicted in figure 2 it consists of following-

• Balance Tank

The Balance Tank holds the wet cake and acts as a buffer tank. • Stirrer

Many materials are sticky / pasty having tendency of forming bridge if not kept agitated. Stirrer has special contour to keep the material agitated and force the wet cake positively on screw feeder. This guarantees continuous flow of wet cake to dryer as shown in Figure 3. It homogenizes the wet cake and increases uniformity of constituents in dry

powder. Stirrer speed and blades are designed to suit wet cake properties. The agitation increases the flowability of wet cake. This reduces the power

required for screw feeder to push the material.

• Screw Feeder The screw feeder has pipe type construction with minimum gaps between

screw and pipe. This ensures that there is no void space for material accumulation and material move ahead positively as shown in Figure 4. The screw feeder remains clean avoiding drying of material in voids. This

avoids charring of material in screw feeder due to hot air and subsequent contamination of dried product. Angular contact bearings are used to reduce friction, wear & tear, thereby

increasing life and reducing power requirement. Further, it eliminates need of thrust bearing making the assembly compact.

• Distributor

The material is discharged from screw feeder on rotating cage of disintegrator. If the pigment is very pasty / sticky the material falls as a lump on disintegrator rotating cage. The disintegrator will not be able to disintegrate this lump fast, and layer of wet cake will form on disintegrator cages and subsequently chock it. To avoid this, distributor is provided to distribute the material and feed it in small nodule shapes. Figure 5 further explains the distributor function.

2. Cage Mill Disintegrator

The principle of Flash Drying is to evaporate surface moisture instantaneously. The material has to be disintegrated into fine particulate to increase the surface area for heat and mass transfer. Cage Mill Disintegrator does this and hence is the heart of Flash Dryer. Figure 2 shows the assembly of disintegrator along with feeding system. The construction and working of Cage Mill Disintegrator is depicted in Figure 6.

It consists of alternate rotating and stationary cages. The cages have close

pitched, large number of rods. The material and hot air are fed at center of rotating cage. It instantaneously disintegrates wet lump in fine agglomerates exposing very high

surface area for drying. Presence of highly turbulent hot air and intimate mixing of hot air with finely

divided agglomerates results reduction of moisture very rapidly. The material looses its stickiness. Also strong centrifugal force totally prevents the material from sticking to the

rods. The mixture of hot air and agglomerates move with high turbulence to the

stationary cage. The agglomerates hit the rods of stationary cage with very high velocities and further disintegrate exposing their core to rapid drying. Hitting agglomerates dislodge any agglomerate sticking to stationary rods. The mixture of hot air and agglomerates undergo similar severe action of

disintegration and drying in subsequent rotating and stationary cages.

At the outlet of last rotating cage material is substantially dried and about 70% moisture is evaporated. Both the material and hot air move in radial outward direction. This avoids back

mixing of semi-dry material with fresh material. The hot air and material moves co-current. The hottest air comes in contact with

material having highest moisture. This avoids charring of material. These make it possible to use high inlet temperature of air making the plant

energy efficient. Further it makes the plant size small reducing the capital cost of equipment, civil cost and so on. The rotating cages are dynamically balanced as per IS 1940 for smooth vibration

free performance. The disintegration action depend upon rod gaps and impeller speed. To obtain

powders of various mesh sizes and thus to increase flexibility of operation, the speed of disintegrator can be changed by variable speed drive or by changing pulleys if made belt driven. To avoid dusting of powder from gap between shaft and casing, air sealing is

provided. The bearing block is robust, fabricated single piece assembly with single setting

machining. This ensures prolong life of bearings avoiding maintenance and production loss. Cleaning windows are provided on casing that facilitates washing of disintegrator

reducing down time.

Combination of cage mill disintegrator with secondary disintegrator make the plant ideal for fine powder applications in organic / inorganic pigments and dyestuff.

3. F. D. Fan and I. D. Fan Blowers are designed for the required duty point. This reduces the power

requirement of blower. The blowers have high efficiency up to 80%. The blowers are tested for following parameters-

- Performance - Vibrations as per IS 1940. - Rise in bearing temperature. This increases the reliability of blowers reducing maintenance and down time of dryer. The bearing block is robust, fabricated single piece assembly with single setting

machining. This ensures prolong life of bearings avoiding maintenance and production loss. Access door for inspection / cleaning facilitates maintenance / washing. Drain plug is provided for removal of condensate while the blower is running.

This avoids plant stoppage increasing productivity. The flow rate of air is an important parameter for proper drying. To control the

quantity of air, damper is provided at outlet of blower. To monitor the performance of blower and in turn that of dryer; manometer

tappings at inlet and outlet are provided. The blowers are either belt driven or direct driven depending upon blower size

and customer requirements. Guard is provided at air inlet and on belt to make the installation safe.

The blower is mounted on rigid base frame and supports for vibration free performance.

4. Drying cum Conveying Duct

The drying cum conveying duct provides necessary residence time for particulate to dry. Moist, disintegrated material from disintegrator enters the duct at one end while dried powder is discharged into cyclone at other end as depicted in figure 1. The bends provided are smooth and curved –

- To reduce pressure drop in the system thereby saving power required for blower

- To avoid settling of powder as depicted in figure 7. On smooth surface powder does not get deposited easily than that on a rough surface. For heat sensitive materials this is very important as deposited material gets charred with time.

Horizontal run of drying duct is averted to avoid settling of powder as depicted in figure 7. The drying duct also functions as conveying duct. The air velocities are similar to

that for pneumatic conveying. This ensures that powder get conveyed properly without chocking the duct. Dryer runs continuously at rated capacity. Manholes / hand holes are provided for ease of cleaning reducing cleaning and

down time of machine.

5. Control Panel & Instrumentation

The dryer is supplied along with a factory pre-wired and tested control panel through which the entire dryer can be operated in automatic as well as manual mode. The control panel has following instruments: • All motors have starters, overload protection relays and necessary fuses / circuit

breakers. • Digital temperature indicators and controllers for air are provided at various

points in the air circuit to indicate drying condition in the plant. • Hot air generator burner is provided with its starter sequence programmer, flame

monitoring and failure safety instruments. • A variable speed drive is provided for material screw feeder that automatically

adjusts feeding rate whenever moisture in feed material varies. This is done by a PID temperature controller which senses outlet air temperature at inlet of cyclone and gives signal to variable speed drive controller for increasing or decreasing the feed rate so that set outlet temperature of air is maintained.

The control panel is provided with various indicating lamps and rotary switches for convenient operation and trouble shooting. Voltmeter and Ammeter are provided on panel for monitoring proper electrical supply conditions.

OTHER COMPONENTS OF FLASH DRYER 1. AIR FILTER

• Air filter – HDPE, 3ply of sufficient area for minimum pressure drop.

• Flanged type construction for ease of removal for cleaning.

• Material selected for filter is water washable.

• Manometer is provided on filter for checking of blockage. 2. HOT AIR GENERATOR

Hot air generator is designed and manufactured Transparent Energy Systems Pvt. Ltd. and have High Thermal efficiency of 93% on NCV & 87% on GCV that gives large saving in fuel cost.

3. CYCLONE • Optimally sized for the desired airflow rate.

• Low pressure drop.

• Settling vessel is provided to have highest powder separation efficiency.

• Cleaning window is provided with hinged door. • Air purging system is provided to prevent bridging. 4. SECONDARY DISINTEGRATOR. • Secondary disintegrator is provided on-line for further disintegrating the dried

powder. • It is belt driven to adjust the speed, which will control the powder fineness. • It is an add-on type assembly. Hence can be used whenever required. 5. BAG FILTER • Large filtering area of Bag filter – reduced pressure drop – large savings in power

consumption of blower.

• Anti-stick coat on bags – reduced chocking. • Low CAN velocity – low powder entrainment – reduce chocking.

• Bustle type construction – low powder entrainment – reduced chocking.

• Automatic air pulse jet system – clean filter bags on-line.

• Designed, manufactured & tested for - Material. - Airflow rate. - Pressure drop at no dusting. - Workmanship.

• Bag removal from top – maintenance in dust free atmosphere.

• Full SS construction (even on exhaust side).

• Bottom cone angle of drying chamber is 45° - powder slides. • Air bleeding system linked with air temperature at inlet to bag filter for protecting the

bags. 6. ROTARY AIR VALVE • Rotary air valves have very less gap between rotors and stators. This reduces

infiltration of air thereby maintaining high powder-separating efficiencies.

• The rotary air valves has back pull type construction. This facilitates easy and quick removal of rotor without necessity of removing drive end.

• Rotary air valves are provided with compressed air purging system. This eliminates chocking of rotary air valve rotor by moist and hygroscopic powders.

• Rotary air valves are provided with oil seals and double Z ball bearings to avoid powder entering in bearings. This increases bearing life and reliability of rotary air valve.

• All Stainless steel construction instead of cast aluminum giving high abrasion resistance and long life.

• Safety grill at outlet is provided for safe operation.

HOW TRANSPARENT FLASH DRYING PLANT IS HIGHLY ENERGY EFFICIENT We ensure lowest drying cost by designing and manufacturing energy efficient Flash Drying Plant. Our Flash Drying plant is highly Energy Efficient due to following-

• Fuel cost is dominant in drying cost. We use 93% efficient Hot Air Generator manufactured by our associate company. This reduces the fuel consumption thereby reducing drying cost.

• The unique cage mill disintegrator with feeding system allows high inlet air temperature without charring the material. This increases the thermal efficiency of dryer decreasing drying cost.

• The use of high inlet air temperature reduces the plant size thereby reducing the capital and civil cost.

• The individual components and sub-assemblies are tested as per “Quality Assurance Plan” and then send to site. This reduces possibility of malfunction of components and sub-assemblies thereby reducing downtime of Plant. Typical Quality Assurance Plan is enclosed for reference.

• We use high efficiency blowers having efficiency up to 80%. This reduces power consumption and drying cost.

• We design and select following components for low air pressure drops- a. Air filter. b. Cage Mill Disintegrator. c. Duct and bends. d. Cyclone. e. Bag filter. f. Hot air generator.

Reduced pressure drop reduces the total head requirement for the blower. This reduces the electrical power consumption of the blowers thereby reducing drying cost.

• Provision of on-line secondary disintegrator eliminates the need of separate pulverizer. This eliminates wastage of material and manpower required for intermediate handling. This increases production and reduces drying cost.

• The plant is fully automatic requiring minimum manpower.

• On-line cleaning system like pulse-jet for filter bags cleaning and knockers minimize the down time. This increases productivity reducing drying cost.

There are many minute aspects to reduce the power consumption, increase production yield, and reduce down time. These aspects are explained in detail under the head – “Main Components of Flash Dryer” and “Other Components of Flash Dryer”.

HOW TRANSPARENT FLASH DRYING PLANT IS EASY TO OPERATE AND DIAGNOSE PROBLEMS Easy to Operate

1. Fully automatic machine consisting of following

• Appropriate safety interlocks.

• PID temperature controller for ensuring constant air inlet temperature. Steady state of burner giving minimum maintenance of burner.

• PID temperature controller with variable speed drive for screw feeder ensuring constant air outlet temperature.

• Audio alarms for any deviation from the set parameter.

• Continuous monitoring / recording of vital parameters. 2. Parameters like airflow rate, fuel firing rate, temperatures and so on, are set

once for all for a given material properties at the time of commissioning. Hence it is easy to operate in subsequent runs.

Easy to diagnose problems 1. The dryer is easy to diagnose for problems due to following facilities-

• Continuous visual indication.

• Manometers for pressure drops of critical components.

• Viewing windows at strategic locations.

2. In our service manual exhaustive troubleshooting chart is given. Prior to handing over the dryer our service engineer educates the operators by simulating various operating conditions.

This makes the Flash Dryer user friendly.

COMPARISON OF TRANSPARENT FLASH DRYER AND SPIN FLASH DRYER

TRANSPARENT FLASH DRYER SPIN FLASH DRYER 1. No back mixing of dry material with

wet material takes place. 1. Back mixing of dry material with

wet material takes place. 2. Only fresh material comes in

contact with incoming hot air blast. This avoids charring of material.

2. Both fresh and back mixed dry material comes in contact with incoming hot air blast. This chars the material

3. No classification of material occurs.

3. Classification of material occurs due to cyclonic motion of air.

4. No sticking of material to walls and no prolonged exposure to heat occurs, hence no degradation of product.

4. Sticking of material to walls and prolonged exposure to heat degrades the product.

FLASH DRYER FOR PIGMENTS

The wet cake of pigments are generally pasty and sticky, hence are very difficult to handle in conventional dryers. Moreover, the tone of pigment is very important parameter along with its particulate size. The powder size varies, as per its application viz. very fine powder (even upto 500 mesh) is required for paint industry. The dryer should be capable of producing these different sized powders easily. In addition to the above heat sensitive nature of pigments makes the drying process a challenging task. We have designed, developed, and successfully commissioned flash dryers for variety of applications. Repeat orders from our customers are the testimony to our capabilities. Following has contributed to our success- The feeding mechanism is critical component for proper working of Flash Dryer.

Following care is taken while designing the feeding system. ⇒ Stirrer is provided in feed tank for following reasons as depicted in figure 3

- It keeps the material in agitated condition avoiding bridge formation. - It positively pushes material in screw conveyor to fill it completely. - It homogenizes the wet cake and increases its flowability.

⇒ Screw feeder has pipe type construction to move the material ahead positively. A ‘U’ trough screw feeder is not able to convey the wet cake ahead due to pasty / sticky nature of wet cake.

⇒ A minimum gap between screw and pipe minimizes dead volume. This avoids dead volume of material. If material accumulates in dead volume, it will get charred due to hot air and damage the tone of pigment.

⇒ If the pigment is very pasty / sticky the material falls as a lump on disintegrator rotating cage. The disintegrator will not be able to disintegrate this lump fast, and layer of wet cake will form on disintegrator cages and subsequently chock it. To avoid this, distributor is provided to distribute the material and feed it in small nodule shapes. This improves particle size, final moisture and tone of pigment.

The cage mill disintegrator is critical component for proper working of Flash Dryer. Following care is taken while designing the cage mill disintegrator. ⇒ As depicted in figure 6 the material and hot air move in radial outward direction

avoiding back mixing of semi-dried material with fresh material. This avoids degradation and retains colour tone.

⇒ The hot air and material moves co-current. The hottest air comes in contact with material having highest moisture. This avoids charring of material and maintains colour tone.

⇒ The gaps between rods of rotating and stationary cages are designed as per the product characteristics.

⇒ The rotational speed of disintegrator is adjusted to achieve the desired powder fineness. Higher the speed finer the powder.

⇒ To achieve required residence time and airflow passages, the cage mill disintegrator size required is bigger than that required for non-sticky / non-pasty wet cakes.

On-line secondary disintegrator is provided to achieve required powder size. The secondary disintegrator is belt driven to adjust the speed of rotation thereby changing disintegration level.

FLASH DRYER FOR PHARMACEUTICAL PRODUCTS MEETING GMP

The wet cake of pharmaceutical products are generally moderately sticky / pasty. Generally the wet cakes are very heat sensitive and degrade even at 100°C. The process air required should be contamination free. The whole plant especially feeding area and powder collection area should be enclosed. In pharmaceutical industry, each batch is to be processed separately to meet tracability requirements. No intermixing of batches is allowed. Fulfilling the above requirements at high production level economically is a challenging task. We have designed, developed and successfully commissioned flash dryers for variety of applications. Repeat orders from our customers are the testimony to our capabilities. Following has contributed to our success- To avoid contamination all components should be rusting free, hence are made of

stainless steel. Following items are fabricated in stainless steel- ⇒ Stool & base frame for disintegrators. ⇒ Frame for feed tank. ⇒ Rail & trolley arrangement for the feed system. ⇒ Belt drive consisting of bearing & pulleys is replaced with drive. To adjust the

speed, frequency inverter is incorporated. ⇒ All stiffener sections. All supports and components are in circular shapes (wherever possible) instead of

flat surfaces to avoid dust settling and corresponding contamination. The process is cleaned using HEPA filter to remove particles upto 5 microns. The feeding mechanism is critical component for proper working of Flash Dryer.

Following care is taken while designing the feeding system. ⇒ Stirrer is provided in feed tank for sticky / pasty wet cakes for following reasons

as depicted in figure 3 - It keeps the material in agitated condition avoiding bridge formation. - It positively pushes material in screw conveyor to fill it completely. - It homogenizes the wet cake and increases its flowability.

⇒ Screw feeder has pipe type construction to move the material ahead positively. A U trough screw feeder is not able to convey the wet cake ahead due to pasty / sticky nature of wet cake. Figure 4 explains this pictorially.

⇒ A minimum gap between screw and pipe minimizes dead volume. This avoids dead volume of material. If material accumulates in dead volume, it will get charred due to hot air and damage the final product. This dead volume will also cause intermixing of two batches, which is not allowed.

The cage mill disintegrator is critical component for proper working of Flash Dryer. Following care is taken while designing the cage mill disintegrator. ⇒ As depicted in figure 6 the material and hot air move in radial outward direction

avoiding back mixing of semi-dried material with fresh material. This avoids degradation of product.

⇒ The hot air and material moves co-current. The hottest air comes in contact with material having highest moisture. This avoids charring / melting of material.

⇒ The gaps between rods of rotating and stationary cages are designed as per the product characteristics.

On-line secondary disintegrator can be provided to achieve fine powder size. Horizontal construction facilitates easy flow of feed powder avoiding need of special feeding arrangement.

COMPARISON BETWEEN TRAY DRYER & TRANSPARENT FLASH DRYER

Tray Dryer Flash Dryer 1. Batch Type Operation equipment. 1. Continuous operation equipment.

2. Extensively labour oriented, as

labour is required for charging, arranging trays, pulverizing etc.

2. No manual handling involved hence substantial saving in labour cost.

3. Separate pulverizing operation needed.

3. Pulverizing and drying operation takes place simultaneously.

4. Due to considerable manual handling lot of material wastage and dusting takes place.

4. Negligible material wastage and dusting takes place. � �

5. The material being stacked in layers in the tray, uniform heating is not guaranteed and hence variation in product quality, moisture content or the possibility of material in top layer getting charred exists.

5. Material being disintegrated uniformly and thorough mixing of hot air & feed in disintegrator, consistent product quality is ensured

6. System efficiency is low due to : - Low inlet air temperature is

required to avoid charring of material, hence low thermal efficiency.

- Drying time is very high and much heat is wasted in the exhaust.

6. High system efficiency due to: - High inlet air temperature can

be used due to unique design of cage mill type disintegrator.

- Low pressure drops in various components, requiring less power for blowers.

- High efficiency Hot Air Generator.

- Fully automatic plant. 7. Material has to be conveyed from

dryer to pulverizer, pulverizer to bagging plant. This results in more manpower requirement and higher material wastage.

7. No material conveying needed. Bagging plant can be installed directly below bag filter of flash dryer.