Spray Drying: Its Uses, Process And Important Factors To Be Aware Of!!

Spray drying can be defined as the transformation of feed from a fluid state into a dried state by spraying the feed or the substance into a hot medium. The feed used in the process can be a solution, paste or suspension which can easily be transformed into agglomerates, powders, and granules. The form that the final or finished product takes is dependent on various factors including the chemical and physical properties of the substance as well as the operation and design of the spray dryer.

The basic idea of the overall spray drying process is the production of highly dispersed dried powders from a fluid or liquid feed by evaporating the solvent. The finished product is achieved by mixing a heated gas with a sprayed fluid of high mass to surface ratio droplets, within a drying chamber or vessel. This causes the liquid solvent to evaporate quickly and uniformly through direct contact.

Uses of the spray drying process

The process of spray drying can be used in a wide variety of applications where the production of a free-flowing dried form of powder is required. But, this method of drying has become the most preferred in the following areas:

-    Tooth and bone amalgams

-    Pharmaceuticals

-    Egg and milk products

-    Textiles

-    Beverages

-    Resins, plastics, and polymers

-    Detergents and soaps

-    Plant extracts, flavors and colorings and many more.

Spray drying is a very flexible process that can easily meet the necessary product requirements of the above-given area's products, offering an inexpensive solution to many drying problems. It can solve drying problems concerning thermally sensitive materials including food ingredients and flavors. The products which are spray dried retain their nutritional value of the ingredients, while providing with a material that can further be used directly in a final composition, and even can be readily mixed or reconstituted.

Phases or methods of the spray drying process

The process of spray drying consists of the following steps:

1.    Feed preparation

The feed used in the process can be a homogenous and free from impurities suspension, paste or solution.

2.    Atomization

Atomization is the most important and critical step in the entire process of spray drying. It is the method of transforming the feed into small liquid droplets. The degree of atomization controls the drying level of the feed as well as of the dryer size.

3.    Drying

This phase of the spray drying process ensures that moisture evaporates quickly from the surface of the feed. This is then followed by a failing rate period where the drying level is controlled by diffusion of the liquid to the surface of the particle.

4.    Removal of powder from moist gas

The separation of powder from the gas needs to be carried out in an economical medium as well as in a pollutant-free manner. The particles are generally removed with bag filters, scrubbers, precipitators or cyclones.

5.    Packaging and cooling

The last step in the spray drying process is the cooling and packaging of the final product.

All these steps are very important to undertake if you want to get perfect spray drying results. However, to ensure that you get powder particles that are free from any impurities, you need to have proper information on drying kinetics as well as a good collection of solid ingredients. Keeping all these will surely provide you with the desired results.

Spray Drying: What Are The Benefits Of Spraying And How Does It Work?

A spray dryer is something that converts a liquid into a solid powder. It is used in several areas such as food processing, pharmaceutical industry, etc. The some spray dried products include instant coffee, milk powder, paint powder, egg powders, resins and detergents.

To say in simple words, spray drying system is what undertakes the complete process – right from receiving liquid feed at an end and packing into a container at the other end from where it is ready to transport.

However, sometimes, mainly in larger plants, a few other processes are added as to make the processing cost as much affordable as possible. Take for example milk processing plant where evaporation technologies are used to raise the feed solids as much as possible.

What are the advantages of spray drying?

Most industries where drying is required, use the spray drying method for its several incredible benefits. In addition to the benefits for mil processing plants, spray drying also has many benefits for pharmaceutical industry, such as:

·         Spray-drying is a scalable process for the production of dry pharmaceutical powders.

·         New devices enable pure drug nanonization and production of submicron drug carriers.

·         Controlling particle properties during process allows specific therapy applications.

·         Spray-drying is an effective means to overcome biopharmaceutical drawbacks of drugs.

·         This technology has become a key player for the production of inhalable drugs.

How does spray drying work?

There are different types of spray drying systems, and spray dryers come in various shapes and sizes but the way they work remains the same.

Spray drying is an evaporation process –widely used method to producing powder from liquids.

Basically, spray drying system has three main parts: a large chamber through which extremely hot air (or a different gas) is passed, a feed pump to supply raw liquid, and an atomizer that helps the formation of droplets.

In addition, there is a drum of cyclone which is used to collect the resulting products.

The solution is fed into spray dryer using a nozzle called atomizing device – which breaks down the feed solution into individual spheres. The work of nozzle is to make the droplets as small as possible and maximize the heat transfer and vaporization rate. The size of droplets varies, depending on the size of nozzles used.

Drying chambers is like a storage silos. The volume of the chamber depends on the heath exposure time required for the feed materials being dried. A burner heats the gas (often air) to force it into the main chamber where feed solution is atomized to develop into small droplets.

On contact with the hot gas the visible powder particles are case hardened, but the core is still in molten state.  The particles then are made to get into contact with hot air that strips remaining moisture from the rest of particles. And thus come out solid particles which are easily made into powder.

Spray Drying Process: Its Method, Uses, And Scope!!

Spray drying is basically a dehydration method that pharmaceuticals and food industries use for drying some of the liquid products into a completely dry state. Unlike other drying methods that form particles which further require grinding and sizing, a spray drying method easily makes free-flowing particles with narrow size distributions. It is mainly used in the manufacturing of products that are very sensitive to changes in temperature including some of the food materials and various pharmaceutical items.

The process of spray drying

The process of spray drying starts with the process of atomization where a nozzle transforms the liquid into droplets. This process also includes a quick drying of liquid materials by the usage of hot gases. These dryer’s nozzle work to distribute the liquid into regulated and even amounts. They further turn liquid substance into dry powders and the swiftness of the entire method offers various advantages to companies as compared to techniques including freeze and other types of drying.

Benefits of spray drying

1.    Spray drying process has adaptability and speed:

Spray drying method’s ability to complete the drying process within seconds is a major advantage over other industrial drying techniques which are slow and are also expensive. In the food industry specifically, fast drying plays an important role in ensuring a minimum loss. The process of spray drying, on the other hand, is adaptable to a huge range of industries and their product feedstock.

2.    The process has quality control:

Spray drying process creates powders of even particle size and overall quality. Being able to control the parameters makes the spray drying process more desirable and reliable for industries like pharmaceuticals, where the absorption of drugs mainly depends on its particle size.

3.    The method is cost-effective:

The entire spray drying method is reasonable and inexpensive. Unlike other drying methods, spray drying is much easier and is relatively cost-effective. One of the reasons why this method is being utilized so rapidly is because of its inexpensive and cost-effective nature.

So, these are some of the benefits that industries gain by utilizing spray drying methods for their products. However, to ensure that the method takes place smoothly and without any issue, it is important to use high-quality spray dryers. Top quality spray dryers are more likely to give excellent and fast results as compared to dryers which are not that good in quality. Therefore, it is crucial to use only good machines for drying the products in order to get excellent and accurate results.

The scope of spray drying

The spray drying method has been used for generating powdered items from fluid feed streams primarily with the use of motor-driven machines from a long time and since then; this process has become very famous particularly in food and pharmaceutical industries. Besides, with the above-given advantages, you can make out the importance of spray drying and its uses in several major industries.

Spray Patternation – The spray pattern is providing an automatic measurement

Patternation is the specialized technical art of performing quantitative measurements of properties within a spray and then the patterns with the spray are visualized. The process is used for nozzle testing. For smaller sprays, OP-200 patternator is used and for bigger ones OP-660 is used. It is the common measurement that is providing maximum output resulting in better resolution. The tests are done in the laboratory and many types of nozzles & injectors are included in the testing. Drop size refers to the size of the individual drops that comprises a nozzle’s spray pattern USA.

Spray patterns are providing a range of liquid drop sizes there are several factors which affect the drop size. It includes liquid properties, nozzle capacity, spray pressure and spray angle. The small drop size is produced for dust suppression between 20 and 200 μm airborne dust particles are required of the same range. A high degree of atomization is used for producing very small drop size and that is achieved by pumping water through nozzles at high pressure. Air atomization is the better choice if compressed air is available and economically feasible.

Information obtained through spray patterns are –

• Patternator number
• Asymmetry ratio
• Local surface area of drops per unit volume
• Cone angle
• Presence of streaks and voids

Here is the detail of some of the characteristics –

Spray Angle: The range gets determined by the spray patterns, the number of nozzles and the nozzle. It is ranging from 0° to 175°.

Operating Pressure: The moisture need defines the operating pressure and flow rate. The nozzle operating should be placed close to the dust source and it is best suited for enclosed areas.

Surface Wetting: The nozzle is used to increase the surface wetting and any impact can also increase surface wetting. The drops are traveling through the turbulent air before they hit the material.

Air atomization is a better choice if compressed air is available and is generally a better choice. They have a large flow passage than hydraulic fine spray nozzles that are reducing clogging. The specific operating conditions determine the nozzle style and spray patterns. It verifies flow rates and drops size at the operating pressures.