Spray dryer cleaning is very important in production. If the spray dryer is not cleaned well, it can cause many problems. In this article, you can learn some common spray dryer cleaning methods, steps, and notes to help you reduce pollution risks.
Why Is It Necessary to Clean Spray Dryers Well?
During the production process, the spray dryer will touch the materials directly. If the spray dryer is not cleaned properly, residual materials may remain inside the spray dryer. This may not meet the industry standards, such as GMP, FDA, and HACCP. Over time, it can cause product contamination, high microbial levels, and nozzle blockage. In serious cases, it may affect product quality, even stop the production line.
Three Basic Spray Dryer Cleaning Methods
Spray dryers usually use three basic cleaning methods: dry cleaning, wet cleaning, and chemical cleaning. You can choose the suitable methods according to materials and production needs.
Dry Cleaning
Dry cleaning is one of the most basic cleaning methods and is usually used for daily cleaning. Before and after each production, you can use a vacuum cleaner and a brush to remove powder inside the equipment. This helps reduce the load of later cleaning. However, dry cleaning is not strong enough to clean deeply, so you’d better use it together with other cleaning methods.
Wet Cleaning
Wet cleaning often uses hot water at 60–80℃ to flush the tower body, nozzles, and pipes. The water pressure can quickly wash away the residual materials and help reduce microbial contamination. As a result, wet cleaning is the most common method for daily cleaning.
Chemical Cleaning
Chemical cleaning means adding special cleaning liquids during cleaning, such as alkaline cleaning liquids (NaOH cleaning liquid) and acidic cleaning liquids(nitric acid cleaning liquids, citric acid cleaning liquids). These liquids react with stubborn residues, break them down, and soften them. Then washing them away with water.
Steps for Spray Dryers Cleaning
Preparation Work
Be Familiar With Spray Dryer Systems
You should read the equipment manual carefully before you begin cleaning operations to understand the structure of the spray dryer, the functions of its components, and the notes for cleaning with safe operation.
Prepare Cleaning Tools
Based on the type of equipment and the requirements of cleaning, prepare proper cleaning tools, such as soft-bristled brushes, cloths, cleaning agents (such as alkaline cleaners, acidic cleaners, neutral cleaners), disinfectants (such as 75% alcohol), lubricating oil, etc.
Safety Protection
During the cleaning process, cleaners should wear necessary protective equipment, such as protective gloves and masks, to avoid irritation from cleaning agents and dust.
Before cleaning, it is also necessary to turn off the system’s power, make sure that the equipment has completely stopped running, and perform safety locks to prevent accidental startup.
Cleaning Procedures
External Cleaning
Keeping the surface of the machine clean is the basic respect for the materials and equipment.
Before finishing production every time, you can spend a few minutes cleaning the machine surface and wiping the machine body, control panel, and pipes to remove dust, oil, and dirt.
For hard stains, you can use a soft brush to clean gently. Do not use hard tools or steel wool, because they will scratch the machine’s surface.
You can do rust protection once a week. Use a soft cloth with food-grade anti-rust oil and wipe the stainless steel surface gently. This forms a protective layer and helps keep moisture away.
Do not spray alcohol on the control panel or wash the machine with a water gun. These are incorrect operations.
Feeding System Cleaning
The cleaning quality of the feeding system directly affects the atomization effect and the purity of the products.
You can remove parts, including nozzles, the feeding pipes, etc., and clean them with water or detergent to remove leftover material and dirt. For parts that are hard to clean, an ultrasonic cleaner can also be used.
Rinse all parts well with clean water. Then use high-pressure air to dry them. Finally, you should make sure every part is fully dry before putting them back.
Drying Tower Cleaning
The drying tower is the main working area of the spray dryer. If it is not cleaned well, it will affect the quality of the next batch of products.
First, you should open the discharge outlet of the drying tower. Use steam or high-pressure water to rinse the inside.
Use a vacuum cleaner and a soft brush to remove dust and material left on the tower wall, the top of the tower, and the bottom of the tower.
For hard dirt stuck to the tower wall, carefully control the water pressure and temperature to avoid damaging the equipment.
After all cleaning is finished, close the tower body and start the hot air system. Use hot air to dry the inner wall and pipes for 15 to 30 minutes.
Make sure the whole system is completely dry, then start the next production batch.
Cyclone Separator & Bag Filter Cleaning
First, open the discharge valve and inspection port at the bottom of the separator. Use high-pressure water to clean the inner wall from top to bottom. Pay special attention to the material collected in the cone-shaped section.
Remove the filter bags or filter elements from the cyclone separator and bag filter. Use a vacuum cleaner to remove dust from the surface.
For material stuck on the filter bags or filter elements, you can use a cleaning solution to soak and gently clean them.
After cleaning, rinse them well with clean water. Then dry them to make sure the filter bags or filter elements are completely dry before putting them back.
Exhaust System Cleaning
If the exhaust system of the spray dryer runs for a long time, dust will build up inside. This can reduce exhaust efficiency and create safety risks.
First, open the inspection port of the pipe. Use a vacuum cleaner or a brush to remove the powder on the pipe wall. Then clean the pipe with high-pressure water until the waste water becomes clear.
Then, clean the fan housing and blades in place when possible. Do not wash the motor parts directly with water.
After cleaning, reinstall all parts and run a test to make sure there are no unusual noises.
Then, the whole cleaning process is complete.
Disinfection & Maintenance
Disinfection and maintenance are the final cleaning steps to keep the equipment clean and running well.
Disinfection
After cleaning, use 75% alcohol to disinfect the inner wall of the spray dryer and the parts that directly touch the material, like pipes and nozzles.
Then, leave it for 10 to 15 minutes. Do not rinse with water here. After the alcohol fully evaporates, the disinfection is finished.
Maintenance
Regular maintenance of the spray dryer is very important. You should check the sealing rings, filter screens, and nozzles once every month. If they are old or damaged, replace them in time. Also, you need to regularly apply food-grade lubricating oil to the bearings and transmission parts.
If the machine will not be used for a long time, fully clean and dry the whole system first. Then cover the equipment to keep dust away.
Notes On Cleaning Spray Dryer
Choose Proper Cleaners
- For materials that can dissolve in water, you can use hot water at 60–80℃ for cleaning.
- For oil, fat, or protein residue, you can use a weak alkaline cleaner, such as 1–2% NaOH solution.
- For mineral residue, use a weak acidic cleaner, such as 1–2% nitric acid solution, and keep the temperature below 65℃.
Don’t use cleaners that contain chlorine. They will damage the stainless steel surface and shorten the life of the equipment.
Food-grade cleaners are needed. For food or pharmaceutical production equipment particularly, the cleaner should be non-toxic, easy to rinse away, and leave no residue. After rinsing, you should also check the pH value and residue level.
Clean Regularly
Cleaning the spray dryer regularly is very important. During production, regular inspection and daily cleaning plans should be made and followed strictly.
After every cleaning, you should record the cleaning time, the cleaner used, and the cleaning details for management and tracking.
Pay Attention to the Cleaning Order
When cleaning the spray dryer, you should follow the order from top to bottom, and from outside to inside. In this way, secondary pollution can be avoided during the cleaning process.
FAQ
What is the Right Cleaning Frequency For Spray Dryers?
- Nozzle: Clean once every shift
- Drying Chamber: Clean once every week
- Filter Bags: Clean or replace once every month
Regular cleaning can help keep the spray dryer clean, stable, and safe during production.
What Is Spray Dryer SIP (Sterilization In Place) Cleaning？
SIP means sterilization in place. It is usually done after CIP cleaning. The main purpose of SIP is to kill the remaining microorganisms inside the spray dryer. This helps meet the clean production standards in industries such as food and pharmaceuticals.
There are three main SIP sterilization methods:
- Steam sterilization
- Dry heat sterilization
- Chemical sterilization
What is Spray Dryer CIP (Clean-In-Place) Cleaning?
CIP (Cleaning-In-Place) means the equipment can be cleaned inside without removing the parts. The cleaning is done inside the spray drying system. During the cleaning process, cleaning liquid and water flow through the pipes, nozzles, and cleaning system, and wash the inside of the tower, pipes, and nozzles.
You will need CIP in many situations, such as:
- The end of a batch production
- Changing product types
- The machine stops running for a long time
- High-standard inspection standards (like food and medicine)
- Cleaning stubborn stains
- Cleaning before resuming production, etc.
What Are the Differences Between Acid and Alkali Chemical Cleaning Solutions to Spray Dryer?
Alkali solution (NaOH): Mainly used to clean organic substances, such as proteins, oils, and polysaccharides.
Acid solution (HNO₃/citric acid): Mainly used to clean inorganic substances, such as scale, mineral deposits, and rust.
Generally, you can first use an alkali solution chemical cleaner to remove oil stains inside the spray dryer, then you can use an acid solution chemical cleaner to remove scale, and finally rinse with clean water.
Why Does Powder Still Stick to The Drying Chamber After Cleaning?
There is some powder still stuck in the drying chamber after cleaning, mainly caused by three aspects:
Sticky materials that contain sugar, oil, or protein can easily stick to the inner walls of the spray dryer. Over time, they can build up and form hard dirt that cannot be fully removed by water alone.
If daily cleaning only uses water rinsing simply, and acid or alkaline cleaners are not used regularly, the cleaning result may become poor. Hard-to-reach areas also need to be cleaned carefully.
If the cleaning water temperature is too low, the cleaning efficiency will also decrease. After cleaning, the drying chamber should be dried with hot air as soon as possible. Otherwise, the remaining powder may become wet and stick together again.
What Tests and Checks Are Needed After Cleaning (GMP Requirements)?
Visual inspection: No leftover dirt and no odor.
Chemical residue test: pH value close to neutral, and no cleaning agent should remain.
TOC test (used in some pharmaceutical production): Check if there is organic residue left.
Microbial test: Check total bacteria, yeast, mold, and other safety indicators.
Cleanliness check: Must meet GMP and HACCP standards.
Final Thoughts
Proper cleaning of spray dryers is an important step in keeping product quality and production safety. Pilotech is a manufacturer specializing in the production of spray dryers and providing drying spray solutions. If you have any questions, please feel free to contact us. We look forward to cooperating with you!