Features of Pilotech Closed-Loop Spray Dryer
- Integrated oxygen sensor with auto-purging
- Equipped with condensation temperature protection
- Low-temperature drying down to 40°C for heat-sensitive samples
- Ultra-compact models occupy less than 1 square meter
- Built-in air compressor features shock-absorption technology and operates quietly
Your Leading Closed-Loop Spray Dryer Manufacturer
A closed-loop spray dryer is a system specifically designed to meet the drying needs of materials containing organic solvents or those prone to oxidation. The system uses an inert gas like nitrogen instead of air as the drying medium. Within this closed loop, the gas and organic solvents can be recycled, helping you save costs.
Pilotech has 21 years of experience in the R&D and manufacturing of lab spray dryers. Our products have been exported to more than 70 countries and regions, including the United States, Germany, the United Kingdom, France, and Australia. We offer a wide range of closed-loop spray dryers, including laboratory-scale batches, pilot-scale, and different nozzles, providing you with flexible options. We also operate a process validation laboratory capable of delivering advanced and comprehensive spray drying validation services for a variety of materials. You can send your specific requirements to us, and we will design customized closed-loop spray drying solutions for you.
Compact and flexible, designed for small-batch trials, with a 10 mL minimum sample volume. Controlled drying atmosphere helps protect heat- or oxygen-sensitive materials while minimizing valuable sample consumption.
Higher processing capacity supports process development and scale-up studies. Stable gas circulation and controlled drying conditions help evaluate particle properties, powder recovery, and production feasibility before industrial manufacturing.
Uses compressed gas to atomize feed liquid into fine droplets, offering particle sizes as small as the micrometer range. Suitable for inhaled medications, food ingredients, and chemicals.
Using the centrifugal shear force generated by a high-speed rotating disc to atomize the feed liquid. Without narrow orifices, it easily handles high-viscosity materials. Well suited for continuous powder production.
High-pressure feed is forced through a small nozzle orifice to generate droplets without atomizing gas. Provides extremely uniform particle size distribution. Suitable for liquids with low viscosity and low solids content.
Closed-Loop Spray Dryer Specifications
The parameters in the table below cover various spray dryer models. Specifications vary by model and configuration.
| Parameter | Specification |
| Equipment Type | Laboratory / Pilot-Scale Closed-Loop Spray Dryer |
| Application | R&D, formulation development, process optimization, solvent-based and oxygen-sensitive materials |
| Feed Capacity | 500–1,500 mL/h for laboratory models |
| Minimum Sample Volume | Approx. 10–30 mL, depending on configuration |
| Drying Gas | Nitrogen / Inert Gas |
| Gas Circulation | Closed-Loop Inert Gas Circulation |
| Max. Inlet Temperature | Up to 200°C |
| Outlet Temperature | Adjustable according to feed and solvent properties |
| Temperature Precision | ±1°C |
| Rated Airflow | Approx. 1.0–1.5 m³/min |
| Atomization Method | Two-Fluid Nozzle |
| Standard Nozzle Size | 1.0 mm |
| Optional Nozzle Sizes | 0.5 / 0.8 / 1.5 / 2.0 mm |
| Particle Size Range | Approx. 1–25 μm |
| Oxygen Monitoring | Integrated oxygen concentration monitoring |
| Solvent Handling | Closed-loop processing with solvent recovery |
| Condensation System | Condensation system for solvent vapor handling |
| Powder Separation | Cyclone separator and powder collection |
| Feed System | Adjustable peristaltic feed pump |
| Control System | PLC control with LCD touchscreen |
| Safety Functions | Oxygen monitoring, temperature protection, system interlocks |
Why Is a Closed-Loop Spray Dryer Important?
Improving Operational Safety
The vapors of many organic solvents are highly prone to explosion when exposed to heat. A closed-loop spray dryer can maintain the oxygen concentration within the system at an extremely low level, thereby fundamentally reducing the risk of fire and explosion. This helps ensure the safety of the laboratory and its personnel.
Protect the Environment
The closed-loop system enables the internal, closed-loop treatment of volatile organic compounds (VOCs). Gases are not directly released to the outside, thereby reducing the pollution of the laboratory and the atmosphere by toxic volatile gases, and complying with strict environmental regulations.
Protecting Sensitive Ingredients
A closed-loop spray dryer can block out most oxygen, effectively preventing the degradation of easily oxidizable active ingredients during the high-temperature drying process.
Cost Savings
Exhaust gas containing organic solvents is not discharged directly but is instead routed to a condensing system for recovery and reuse. The solvent recovery rate typically reaches 95%–99% or higher, significantly reducing your procurement costs of expensive organic solvents.
Are Closed-Loop Spray Dryers More Expensive?
Yes. To achieve a gas-tight closed-loop system, solvent condensation and recovery, and explosion-proof safety, closed-loop spray dryers incorporate a significant number of high-cost, specialized designs in both their hardware and control systems. As a result, the equipment cost and initial purchase price are significantly higher than those of open-loop spray dryers with equivalent specifications.
The following are the specific additional technical and hardware designs.
Condensing System
A closed-loop spray dryer requires additional equipment including a condenser, a low-temperature refrigerant circulation unit (chiller), and a solvent collection tank. This system requires precise temperature control to condense high-temperature solvent vapor into a liquid for easy recovery.
Online Oxygen Monitoring and Control
This device is equipped with a high-precision oxygen sensor and an automatic nitrogen replenishment/self-cleaning valve, enabling real-time monitoring of oxygen levels in the circuit. When oxygen levels exceed the safety threshold, it automatically shuts off the heating and injects nitrogen to help ensure safe operation.
Explosion-Proof Design
All electrical components of the closed-loop spray dryer, including motors, heaters, solenoid valves, sensors, and PLCs, must feature an explosion-proof design. They must comply with standards such as Ex d, Ex px, or Class I Division 1/2. The cost of explosion-proof electrical equipment is several times that of standard electrical equipment.
Seal Design
The tower, piping, and connections of a closed-loop spray dryer require an extremely high-precision airtight design. They are typically equipped with special seals made of materials such as Teflon (PTFE) and FKM. These materials are resistant to corrosion by organic solvents and can withstand high temperatures. These seals can provide long-term, effective protection against leaks of nitrogen or other inert gases, as well as solvent seepage.
Safety Pressure Control and Explosion Relief Design
The closed-loop spray dryer is equipped with explosion vents, differential pressure sensors, and an automated safety interlock system. This design enables the dryer to conduct a safe shutdown in the event of extreme pressure.
Applications of Closed-Loop Spray Dryer
| Application Field | Why Closed-Loop Spray Dryer Suitable | Specific Applications |
| Pharmaceuticals | Many APIs are extremely poorly soluble in water and must be dissolved in organic solvents. Open-air drying poses an explosion risk, and the active ingredients are prone to oxidation. Nitrogen gas as the drying medium to achieve explosion-proof operation while preventing oxidation. | Solid dispersions, dry powder inhalers (DPI), liposome nanoparticles, inhalable microspheres. |
| Advanced Ceramics and Battery Materials | During the granulation of silicon carbide, silicon nitride, and lithium-ion battery cathode materials, some water-based slurries can easily cause oxidation or hydrolysis of the materials. Inert nitrogen gas provides a closed-loop protective environment to prevent material surface oxidation and condenses to recover solvents, ensuring micro-granulation purity and powder fluidity. | Lithium battery anode/cathode materials, silicon nitride/silicon carbide structural ceramic slurry granulation. |
| Polymers and Encapsulation | Low-temperature closed-loop drying precisely controls the solvent evaporation rate, preserving polymer molecular weight integrity and achieving high solvent encapsulation efficiency. | PLGA sustained-release microspheres, polymeric biodegradable materials, high-end organic pigments and dyes. |
| Toxic and Highly Potent Compounds | The closed-loop spray dryer operates with a fully sealed gas circulation system, ensuring that no harmful gases or fine powders are released into the laboratory environment. This significantly enhances operator safety. | Cytotoxic/anti-tumor drugs, pesticide active ingredients/reagents, highly active intermediates. |
Closed-Loop Spray Dryers with Different Atomization Methods
Two-Fluid Nozzle Closed-Loop Spray Dryer
Working Principle
The feed liquid and compressed nitrogen collide in a mixing chamber located either outside or inside the nozzle, generating high gas flow shear forces. These shear forces break up the continuous liquid stream into extremely fine droplets, which are then dried to form powders.
Particle Adjustment Method
The primary method is to adjust the ALR. You can increase the compressed gas pressure to enhance shear force, resulting in smaller droplets and finer powder particle sizes. Conversely, lowering the gas pressure increases particle size.
In addition, reducing the concentration or viscosity of the feed solution also helps produce finer particles. You can also adjust the target particle size by replacing the cap with different orifice sizes.
Purchasing Recommendations
Two-fluid nozzle closed-loop spray dryers do not rely on the high pressure of the liquid itself for atomization and do not require a large feed rate. This makes them well-suited for small-scale R&D materials in the range of several dozen milliliters.
Furthermore, the high shear force of a two-fluid nozzle can atomize droplets as small as a few micrometers. This shear force is also effective for processing materials of medium viscosity. If your material has a certain degree of viscosity or if you wish to produce extremely fine powders, you may want to consider two-fluid nozzle closed-loop spray dryers.
Rotary Atomizer Closed-Loop Spray Dryer
Working Principle
The rotary atomizer closed-loop spray dryer features high-speed rotating disks, typically operating at speeds ranging from 10,000 to 50,000 RPM. Under centrifugal force, the feed liquid spreads into a thin film. Then it is broken up into tiny droplets as it leaves the edge of the disk and then dried to form a powder.
Particle Adjustment Method
If you want to reduce particle size, you can increase the rotational speed to enhance the centrifugal shear force, resulting in smaller droplets. Reducing the rotational speed increases particle size.
If you need to keep the rotational speed constant, you can also reduce the feed rate to thin the liquid film on the rotary disc, thereby reducing particle size. In addition, you can use different types of discs like grooved, flat, or perforated discs to accommodate the characteristics of various materials.
Purchasing Recommendations
If you need to process high-viscosity, high-solids slurries, a rotary atomizer closed-loop spray dryer is definitely an excellent choice. Free from narrow nozzle orifices, rotary atomizer closed-loop spray dryers reduce clogging risks and are suitable for uninterrupted continuous production for high-viscosity slurries.
They are also well-suited for pilot-scale projects involving large processing volumes that require continuous, stable production.
Pressure Nozzle Closed-Loop Spray Dryer
Working Principle
The pressure nozzle closed-loop spray dryer uses a high-pressure pump to force the feed liquid directly into the nozzle. The feed liquid is then sprayed out through the nozzle’s tiny orifices and dispersed into droplets. Then the droplets are dried into powder.
Particle Adjustment Method
To adjust the particle size, you need to replace the orifice or swirl core with ones that have different pore sizes.
If replacement is not possible at the moment, you can also adjust the pumping pressure to change the particle size. Increasing the feed pressure accelerates the ejection velocity, causing the droplets to break into finer particles and resulting in a smaller particle size. Conversely, lowering the pressure increases the particle size.
Purchasing Recommendations
If you need coarse particles with good flowability, a pressure nozzle closed-loop spray dryer is an excellent choice. It can produce spherical particles ranging from 50 to 200 μm with an extremely uniform particle size distribution.
However, this type of equipment is only suitable for processing low-viscosity solutions free of particulate impurities. Otherwise, clogging is likely, resulting in wasted time and costs.
Closed-Loop Spray Dryer Maintenance
| Maintenance Interval | Maintenance Item | Detailed Requirements |
| Daily / Per-Batch | Airtightness Test | Perform a nitrogen pressure drop test before starting operation to ensure no gas leakage in the system. |
| Nozzle / Atomizer Cleaning | Immediately flush the atomizer and feed pipelines with pure solvent after each batch to prevent residues from drying and clogging the nozzle. | |
| Check Sensors and Alarms | Verify that the oxygen monitor, pressure gauges, and inlet/outlet temperature sensors display normal values, and confirm that safety interlocks are responsive. | |
| Monthly | Seal Inspection and Replacement | Inspect O-rings and gaskets on the drying chamber door, flange connections, and sight glasses for aging, hardening, or swelling. Replace if necessary. |
| Condenser Cleaning | Inspect the condenser fins or tube bundles and clean accumulated fine powders and dirt to ensure heat exchange efficiency. | |
| Filter and Separator Inspection | Clean or replace HEPA filters and bag filter cartridges to prevent dust clogging that causes high backpressure in the recycling loop. | |
| Blower Maintenance | Check the operation sound and vibration level of the nitrogen recirculating fan, and clean any residual build-up on the fan impeller. | |
| Quarterly | Sensor Calibration | Calibrate the oxygen sensor, pressure sensors, and temperature probes using standard gases or reference samples to ensure explosion-proof safety system accuracy. |
| Annually | Safety and Pressure Relief Servicing | Inspect the condition of explosion relief vents/rupture discs, and test the operational performance of safety shut-off valves and pressure relief valves. |
| Chiller Unit Servicing | Check refrigerant pressure, top up refrigeration oil, and clean the condenser radiator to ensure efficient cooling and solvent recovery. | |
| Electrical and PLC Inspection | Inspect the electrical cabinet wiring for tightness and insulation performance; perform a comprehensive functional test of PLC safety interlock programs. |
After leaving the drying tower, the nitrogen mixed with solvent vapor first passes through a cyclone separator to remove fine particles. Then it enters the integrated condensing system. The condenser uses a low-temperature refrigerant to rapidly cool the carrier gas to below the solvent’s dew point, causing the gaseous solvent to efficiently condense into liquid droplets that are collected in a receiving tank. The dried nitrogen is reheated and recirculated for reuse. Solvent recovery rates typically exceed 95%.
Typical yields for lab-scale batches range from 70% to 90%, depending on the material’s viscosity and particle size. To reduce powder retention, the inner walls of our drying towers are often mirror-polished or coated with a micro-fluorine coating to reduce adhesion. If needed, you can also integrate air hammers or static eliminators. Additionally, optimizing the distribution of the inlet airflow and implementing anti-adhesion designs can effectively prevent undried droplets from adhering to the chamber.
Yes, our equipment comes standard with an electrochemical or zirconia oxygen sensor, capable of continuously monitoring the oxygen concentration in the circuit in real time. The system incorporates a PLC. It can automatically open the nitrogen valve to perform pulsed purging when the oxygen concentration exceeds the limit, continuing until the oxygen level drops to a safe level. The entire process requires no manual operation and includes automatic shutdown and audible and visual alarms in the event of a limit violation, guaranteeing safe, explosion-proof operation.
Yes. Our system offers excellent co-solvent compatibility. Mixtures of water and organic solvents can also be safely dried in a closed-loop, inert-gas circulation system. The condensation system is designed with sufficient cooling capacity to condense both water vapor and organic solvent vapors at the same time. As long as the oxygen content in the nitrogen atmosphere is controlled and the condensation temperature is adjusted according to the boiling and freezing points of the mixed solvents, there is no need to modify the hardware circuit.
Yes. The closed-loop spray dryer enables low-temperature drying with inlet air temperatures as low as 40°C to 60°C by optimizing hot air circulation and inlet air temperature control. Combined with efficient dehumidification and condensation within the closed-loop system and high negative-pressure assistance, organic solvents can evaporate rapidly at lower temperatures. It is particularly well-suited for drying heat-sensitive materials prone to thermal degradation, such as proteins, enzyme preparations, liposomes, and active pharmaceutical ingredients (APIs).
Every closed-loop spray dryer undergoes a 24-hour nitrogen pressure retention test before shipment. Test certificates, motor/PLC explosion-proof compliance certificates, and CE documentation are included in the shipment.
Our system is optimized for micro-scale lab trials, requiring a minimum sample volume of as little as 10 to 50 mL. Moreover, our closed-loop spray dryer can achieve high product recovery (typically 70%–90%) through a high-efficiency cyclone separator combined with mirror-polished internal chamber walls and a static-eliminating design, guaranteeing minimal powder adhesion during low-volume batch runs.