Knowledge of the hardest spray drying tower

Spray drying tower is a device that can complete drying and granulation at the same time.It is a common device in the fields of biological pesticides，medicine，food microorganisms，etc.

Today，we will introduce the working principle，characteristics，operating procedures，common fault repair methods and operating precautions of the spray drying tower in detail，so that you can have a deep understanding of the spray drying tower in a short time!

Main functions:

The materials in solution state can be sprayed into the spray drying tower，and the materials will be discharged in solid powder state after drying.The pressure，flow and orifice size of the feed pump can be adjusted according to the process requirements，

The required spherical particles with a certain size ratio are obtained.Most of them are used for drying biological pesticides，medicines and food microorganisms.

Working principle:

After being filtered and heated，the air enters the air distributor at the top of the dryer，and the hot air enters the drying chamber in a spiral shape.

The feed liquid passes through the high-speed centrifugal atomizer or high-pressure atomizer on the top of the tower body，and the spray becomes a very fine atomized liquid bead，which can be dried into a finished product in a very short time in parallel with the air.

The finished products are continuously output from the bottom of the drying tower and the cyclone separator，the micro dust materials are collected by the pulse bag collector，and the waste gas is discharged by the fan.

Features of spray drying tower

1.Fast drying speed，it only takes a few seconds to complete;

2.Suitable for drying heat sensitive materials;

3.Wide application range:according to the characteristics of materials，it can be used for hot air drying，centrifugal granulation and cold air granulation.Most products with very different characteristics can be produced with this machine;

4.Because the drying process is completed in an instant，the particles of the finished product can basically keep the approximate spherical shape of the liquid drop，and the product has good dispersion，liquidity and solubility;

5.The production process is simplified and the operation control is convenient.Spray drying is usually used for solutions with a solid content of less than 60%.After drying，there is no need to crush and screen，which reduces the production process and simplifies the production process.

For the particle size，bulk density and water content of the product，within a certain range，the operating conditions can be changed for adjustment，which is very convenient for control and management;

6.In order to prevent materials from being polluted and prolong the service life of the equipment，all parts in contact with materials can be made of stainless steel.

Main types

1.Centrifugal spray

High speed centrifugal spray drying is the most widely used process in liquid forming and drying industry.

It is most suitable for generating powder and granular solid products from solution，lotion，suspension and paste liquid raw materials.Therefore，spray drying is a very ideal process when the particle size distribution，residual moisture content，bulk density and particle shape of the finished product must meet accurate standards.

Performance characteristics:

1)The drying speed is fast，and the surface area of the material liquid is greatly increased after atomization.In the hot air flow，95%-98%of the water can be evaporated instantly，and the drying time is only a few seconds.It is especially suitable for drying heat sensitive materials.

2)The product has good uniformity，fluidity and solubility，high purity and good quality.

3)The production process is simplified and the operation control is convenient.For the liquid with a moisture content of 40-60%(up to 90%for special materials)，it can be dried into powder products at one time，which is very convenient for control and management.

Applicable materials:

Chemical industry:sodium fluoride(potassium)，basic dye pigments，dye intermediates，compound fertilizers，formaldehyde silicic acid，catalysts，sulfuric acid agents，amino acids，white carbon black，etc.

Plastic resin:AB，ABS lotion，urea formaldehyde resin，phenolic resin，sealant(urea)formaldehyde resin，polyethylene，PVC，etc.

Food industry:rich milk powder，lecithin，cocoa milk powder，milk replacer，blood hunting powder，egg white(yellow)，etc.

Food and plants:oats，chicken juice，coffee，instant tea，spice meat，protein，soybean，peanut protein，hydrolysate，etc.

Sugar:corn syrup，corn starch，glucose，pectin，maltose，potassium sorbate，etc.

Ceramics:alumina，ceramic tile materials，magnesium oxide，talcum powder，etc.

2.Pressure spray

working principle:

The working process of the unit is that the feed liquid is input through the diaphragm pump at high pressure，and the atomized liquid drops are sprayed out，and then flow down together with the hot air.Most of the powder particles are collected by the tower bottom discharge port.The waste gas and its tiny powder are separated by the cyclone separator.The waste gas is discharged by the exhaust fan.The powder is collected by the pollinator at the lower end of the cyclone separator.The fan outlet can also be equipped with a secondary dedusting device，with a recovery rate of more than 96-98%.

Performance characteristics:

1)The drying speed is fast，and the surface area of the material liquid is greatly increased after atomization.In the hot air flow，95%-98%of the water can be evaporated instantly，and the drying time is only ten seconds to tens of seconds，which is especially suitable for the drying of heat sensitive materials.

2)All products are spherical particles with uniform particle size，good fluidity，good solubility，high purity and good quality.

3)It is widely used.According to the characteristics of materials，it can be dried with hot air or granulated with cold air.It has strong adaptability to materials.

4)Simple and stable operation，convenient control，easy to realize automatic operation.

Applicable materials:

Spray drying granules:

Chemical industry:catalyst，resin，synthetic detergent，grease，ammonium sulfate，dye，dye intermediate，white carbon black，graphite，ammonium phosphate，etc.

Food:amino acids and analogues，condiments，protein，starch，dairy products，coffee extracts，fish meal，meat essence，etc.

Pharmaceutical:Chinese patent medicine，pesticide，antibiotic，pharmaceutical granules，etc.

Ceramics:magnesium oxide，porcelain clay，various metal oxides，dolomite，etc.

Spray granulation:various fertilizers，alumina，ceramic powder，pharmaceuticals，heavy metal superhard steel，fertilizer，granular laundry powder，Chinese patent medicine.

Spray cooling granulation:amino fatty acid，paraffin，glyceride，tallow，etc.

Spray crystallization，spray concentration，spray reaction and other aspects are often used.

3.Traditional Chinese medicine spray

The machine is fully enclosed，and all parts are made of stainless steel.It is equipped with a three-stage purification device，and the filtered air reaches the requirements of 100000.The cylinder and the top are equipped with cold wall devices to keep the wall temperature<At 80℃，the drying tower is equipped with air brush tower cleaning device.

The traditional Chinese medicine extract powder dried by the machine will not appear coking and deterioration，greatly increasing the powder collection rate(more than 95%)，and will not produce drug mixing and wall sticking.

working principle:

The high-speed centrifugal spray device for Chinese herbal extracts is the application of centrifugal spray drying technology in the drying of specific materials.It is also a drying device that uses high-speed centrifugal atomizers to disperse materials into mist，fully contact with hot air，complete instant drying，and form powder finished products.

Performance characteristics:

1)The tower body is provided with a cold air jacket;

2)The tower body is equipped with an automatic rapping device;

3)The tower body and pipeline are equipped with quick opening cleaning holes and blowdown holes;

4)Can be equipped with automatic control constant temperature charging tank;

5)It can be equipped with manual high-pressure washing tower accessories;

6)The part in contact with the material is made of stainless steel;(or made of stainless steel)

7)Two pole cyclone dust remover or primary cyclone dust remover and wet dust remover are used for material collection;

8)Automatic control and continuous device for inlet air temperature.

9)Can be equipped with air sweeper

4.Airflow spray

working principle:

It is mainly to spray air or steam from the nozzle at high speed，separate the feed liquid into small droplets by friction，and make it fully contact with hot air to form heat exchange.The whole process takes less than half a minute.The effect on viscous materials is very good，which is incomparable with other spray dryers.And it is easy to operate.

Product application:

The main applications are chemical industry:latex，dye，resin，etc;Food industry includes maltose，dextrin，starch，etc;Dairy industry and building materials industry are also frequently used.

Operation process

The operation procedure of the spray drying system is to define the technical characteristics of the equipment→check and confirm the equipment→production operation→shutdown operation→clean the system.Specific procedures are as follows:

1.Clarify the technical characteristics of the equipment(spray drying tower)

Liquid processing capacity:270-400kg/h;Evaporated water volume:170-250kg/h;Finished product output:100-150kg/h;

Inlet air temperature≥185-240℃;Air outlet temperature≤95℃

2.Equipment inspection and confirmation

Check whether the production water，electricity and steam are normal;Check whether the voltage and current instrument signals are normal.

Check the oil level of the tundish agitator and add lubricating oil in time;If the mixing paddle falls off，fasten it in time;Start the agitator and observe whether it rotates normally and whether there is noise.

Whether the sealing materials are installed at the pipe joints and then connected to ensure that unheated air is not allowed to enter the drying chamber.

Before the operation，the drying chamber，material pipeline，tundish，receiving cylinder and other devices and components in contact with materials shall be cleaned to meet the sanitary requirements of product quality.(90℃hot water tank washing and high-pressure pipe before start-up)

Add lubricating oil to each lubricating point of the equipment as required.

Check whether the transmission equipment operates flexibly and the steering is correct by inching.

Close the observation window，install the receiving cylinder，and check whether the sealing condition of each pipe contact，valve，etc.is good

Whether the process parameters and operating procedures are clear.

Completely drain the steam condensate in the branch cylinder and pipeline，and slowly open the steam valve.

3.Production operation

1)First start the forced draft fan→start the exhaust fan→start the electric heating make-up→start the atomizer→maintain the negative pressure of 100-200 Pa，and drain the steam condensate in the drum cylinder and steam pipe，

Slowly open the steam valve and preheat the drying tower for about 0.5-1 hour(start the material pump for feeding only after the condensed water in the air duct and tower has become steam and discharged).

2)After feeding，the normal negative pressure is maintained at 50-150Pa，the feeding amount is adjusted，the tower temperature is controlled at 75-90℃，and the water content is less than 5%;Pay attention to the material level in the material tank at any time during the drying process.

3)Finished product packaging:After the seasoning(powder)products dried by spray and cooled to room temperature are inspected as per the standard，they are bagged and weighed according to the quality requirements，and then put into the inspection certificate，

The sealing seam bag shall be put into the warehouse(the warehouse shall be kept well ventilated and dry).

4.Shutdown operation

1)After the drying of each batch of materials is completed，the hot water switch added to the tundish shall be turned on to clean the atomizer，atomizing disc，material pipe，pump，etc.

2)The shutdown sequence is as follows:stop steam→feed pump→electric heater→atomizer(adjust the air outlet temperature to make the feeding speed between 15-20，and turn off the atomizer when the inlet air temperature drops to 150℃)→turn off the rapping→dry the exhaust fan→air supply mechanism(the inlet air temperature drops to 110℃)→turn off the power supply.

5.Cleaning system

1)In order to ensure the cleanness of the drying tower body，its pipes and all parts contacting the finished product，it is necessary to obtain first-class products and regular cleaning equipment.

2)When the product is replaced，or the equipment has been stopped for more than 24 hours without cleaning，a thorough cleaning shall be conducted.

Dry cleaning:clean with brush，broom and vacuum cleaner.Wet washing:Clean with hot water at 60-80℃.

Pickling:prepare nitric acid(HNO3)into a solution with a concentration of 1-2%，wash it at a temperature not exceeding 95℃，and then wash it with water.

Alkali washing:sodium hydroxide(NaOH)is prepared into a solution with a concentration of 0.5-1%，heated to 60-80℃for washing，and then washed with water.

3)After wet washing and chemical washing，the equipment and components shall be installed and sterilized at high temperature for 15-30 minutes.

4)When cleaning the equipment，it should be noted that chlorine and its compounds should not be used.

5)The air filter shall be cleaned according to the ambient conditions，i.e.the dust content in the air.Generally，it shall be cleaned once every 3-6 weeks if the content is high，and once every 6-8 weeks if the content is low.

Common troubleshooting methods

1.Wall sticking

(1)The feeding amount is too large to fully evaporate;

(2)Insufficient heating of drying chamber before spray;

(3)When starting spray，the blanking flow is adjusted too much;

(4)The feed liquid added is unstable.

Repair method:

Properly reduce the feeding amount;

Properly increase the inlet and outlet temperature of hot air;

At the beginning of spray，the flow should be small，gradually increased，and adjusted to an appropriate time;

Check whether the pipe is blocked，adjust the solid content of the material，and ensure the fluidity of the material liquid.

2.High moisture content

Generally，the exhaust temperature is too low.Reduce the feeding amount appropriately to increase the exhaust temperature.

3.Low purity

(1)Poor air filtration effect;

(2)The accumulated powder is mixed into the finished product;

(3)Raw material purity is not high;

(4)The equipment is not cleaned thoroughly.

Repair method:

Check whether the filter material in the air filter is laid evenly and whether the filter has been used for too long.If yes，replace it immediately;

Check the coke powder at the hot air inlet to overcome eddy current;

The feed liquid shall be filtered before spraying;Re clean the equipment.

4.The powder particles are too fine

The solid content is too low or the feeding amount is too small.Increase the solid content of the feed liquid，increase the feed volume and increase the air inlet temperature.

5.Powder loss

The separation effect of cyclone separator is poor.

Repair method:

(1)Check whether the cyclone separator is deformed due to knocking and collision;

(2)Improve the air tightness of the inlet and outlet of the cyclone separator;

(3)Check whether the inner wall and outlet are blocked by accumulated materials.

6.The rotation speed of the nozzle is low

The components of the centrifugal nozzle have failed.Check the components inside the nozzle.

7.Low evaporation

(1)The air volume of the whole system decreases;

(2)The inlet temperature of hot air is low;

(3)The equipment has air leakage and cold air enters the drying room.

Repair method:

(1)Check whether the rotating speed of the centrifuge is normal;

(2)Check whether the position of the regulating valve of the centrifuge is correct;

(3)Check whether the air filter and air heater pipes are blocked;

(4)Check whether the grid voltage is normal;

(5)Check whether the electric heater works normally;

(6)Check whether the connection of each component of the equipment is sealed.

8.Nozzle vibration

Failure cause:

(1)Residual substances in the spray plate or bending and deformation of the main shaft caused by improper cleaning and maintenance of the nozzle;

(2)The dynamic balance of the centrifugal disc is poor.

Repair method:

(1)Check whether there is any residual substance in the spray tray，and clean it in time if there is;

(2)Replace the spindle if it is abnormal;

(3)Re adjust or replace the dynamic balance of the centrifugal disc.

Operation precautions

1.First turn on the centrifugal fan，then turn on the heater，and check whether there is air leakage.If it is normal，preheat it.Since the evaporation capacity of the drying equipment is determined by the preheating of hot air，the inlet air temperature should be increased as much as possible without affecting the quality of the dried materials.

2.During preheating，the atomizer is placed at the top of the drying chamber，and the drying chamber and the discharge port of the cyclone separator must be sealed to prevent cold air from entering the drying chamber and reducing the preheating efficiency.

3.When the inlet temperature of the drying chamber reaches the set temperature，turn on the centrifugal nozzle.When the spray nozzle reaches the maximum speed，turn on the feed pump，add clean water and spray for 10 minutes，and then replace it with liquid feed.The feed volume should be increased from small to large，or wall sticking will occur until it is adjusted to appropriate requirements.The concentration of the feed liquid shall be prepared according to the drying property of the material to ensure good fluidity of the finished product after drying.

4.The temperature and humidity of the dried finished product depend on the exhaust temperature.During operation，it is extremely important to keep the exhaust temperature constant，which depends on the size of the feeding amount.The feeding amount is stable，and the outlet temperature is relatively stable.If the solid content and flow rate of the feed liquid change，the outlet temperature will also change.

5.If the product temperature is too high，the feeding amount can be reduced to increase the outlet temperature.If the product temperature is too low，the opposite is true.For heat sensitive materials with low product temperature，the feeding amount can be increased to reduce the exhaust temperature，but the product temperature will be increased accordingly.

6.Collect the dried finished products.In the pollinator at the lower part of the cyclone separator，the pollinator shall be replaced before being filled.When replacing the pollinator，the butterfly valve above must be closed first.

7.If the dried finished product is hygroscopic，the cyclone separator and its pipes and pollinators shall be wrapped with thermal insulation materials to avoid moisture regain and absorption of the dried finished product.