This not only results in the waste of precious samples, but also affects the accuracy of experimental data and the continuity of the research process. This article will delve into the reasons behind these issues and provide practical solutions.

What is the reason for the low sample recovery rate of 01?

Open the dryer collector and find that the sample volume obtained is much lower than expected? This low recycling rate is usually caused by several factors.

The issue of equipment sealing is the primary factor leading to a decrease in recovery rate. The sealing rubber rings, gaskets, and other components of the equipment will age and lose their elasticity after prolonged use, making it difficult to fit tightly and resulting in gaps.

External air enters the interior of the equipment through these gaps, causing turbulence in the airflow inside the drying room. Some of the already dried finished powder will escape with the turbulent airflow, resulting in a decrease in collection rate.

The fault of spray system cannot be ignored. During long-term use, the inner wall and nozzle holes of the nozzle will gradually wear out due to material erosion and high-speed spraying.

After the nozzle wears out, its size and shape will change, resulting in uneven size of the sprayed droplets. Larger droplets are not fully dried and cannot be effectively collected; Smaller droplets may be directly expelled with the airflow.

Improper setting of drying parameters is also a common reason. When the inlet temperature is set too low, the moisture in the material cannot evaporate quickly, and some materials may not dry into powder form, but instead form wet particles or lumps.

These materials are prone to adhere to the inner walls of the equipment during the collection process, making it difficult for them to enter the collection device smoothly.

Excessive air volume can cause the airflow in the drying room to be too fast, and the dried finished powder cannot settle into the collection device before being carried out by high-speed airflow, resulting in a low collection rate.

02 Wall sticking phenomenon, a tricky problem

Wall sticking is one of the most common problems in the spray drying process. It not only affects the product recovery, but also may lead to sample deterioration.

The most common situation for semi wet materials to stick to the wall is that the sprayed droplets come into contact with the wall before reaching the surface dry state, thus sticking to the wall.

The position of sticking to the wall is usually on the plane facing the trajectory of the mist droplets sprayed by the atomizer.

The hot melt adhesion of low melting point materials is related to their properties. The reason is that the material reaches its melting point at a certain temperature and begins to melt, becoming sticky and adhering to the wall of the vessel.

Although surface adhesion of dry powder is inevitable, its impact is usually minimal. Dry powder always hits the wall of the container when moving in a limited space, but this kind of sticky wall is generally not thick and can be shaken off by blowing air or gently tapping.

The phenomenon of sticking to the wall can bring a series of problems: the material stuck to the wall for a long time may be burnt or deteriorated, affecting product quality; The material sticking to the wall may block the bottom of the product falling into the dryer, making it impossible for the product to reach the required moisture content; In order to remove wall sticking materials, additional cleaning operations may be required to shorten the effective operation time.

03 Practical solutions to enhance experimental effectiveness

Faced with the above problems, experimenters can take the following measures to significantly improve the effectiveness of equipment use.

Optimizing drying parameters is the foundation. Appropriately increasing the inlet air temperature can accelerate the evaporation of moisture on the surface of fog droplets and reduce the chance of wet fog droplet contactor walls. Monitor and calibrate temperature sensors to maintain stable exhaust temperature.

Using a frequency converter to control the feed pump, ensuring uniform flow and avoiding excessive feed speed.

Strengthening equipment maintenance is key. Regularly clean the nozzle and use specialized tools to remove clumps; Filter the material before feeding to ensure the purity of the liquid; Check the balance of the atomizing disc and replace worn nozzles in a timely manner.

Clean the drying room after each batch and use a soft scraper to avoid damage to the inner wall; Regularly check the airtightness of the cyclone separator and clean the internal powder accumulation (must be cleaned after continuous operation for 72 hours).

Improving device configuration can fundamentally solve the problem. For the problem of wall sticking, a sandwich wall drying tower can be used, in which air cooling is used to maintain the wall temperature below 50 ℃.

Introduce secondary air cooling tower wall through tower wall rotating blades in a tangential direction; Install an air broom consisting of a row of nozzles near the tower wall and slowly rotate it along the tower wall.

To improve separation efficiency, the cyclone separator can be checked for any deformation; Improve the airtightness of the discharge port of the cyclone separator; Consider adding secondary dust removal (such as bag filters).

04 Daily maintenance, prevention in advance

Establishing regular maintenance habits is the key to preventing problems.

Test the emergency stop button and overload protection function before starting up daily; Check the clearance between the atomizer bearings every month; Add high-temperature lubricating grease periodically; Establish and maintain archives to record the trend of changes in key parameters such as temperature and pressure.

Pay attention to equipment abnormal signals: When the equipment experiences abnormal vibration or noise, check whether the atomizing disc is in a balanced state, whether the bearings are working properly, and whether the lubricating oil is added correctly.

In case of overheating fault, abnormal feeding system, blocked spray head, poor exhaust or alarm of safety device, the operation shall be stopped immediately and necessary inspection and maintenance shall be carried out.

Optimization of process parameters and regular maintenance of equipment are double guarantees for improving the performance of small experimental spray dryer. When the sample recovery rate is low or wall sticking problems are troubling your experiment, you may start by investigating the three most common factors: inlet air temperature, material flow rate, and equipment sealing.