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 Drift and Drop Size Characterization

Agricultural formulations require precise droplet size and spray drift potential. The classification of the droplet size straightly defines the characterization of the agricultural pesticide, herbicide, etc which affects the crops and even the other living being around it if not spray down properly. Reputed companies are now focusing on manufacture spray nozzle and buffer zones of appropriate sizes. Generally, companies follow special rules and follow up to manufacture the equipment in an appropriate way.

All big companies in this market have their unique recipe to deal with characterizing synthetic liquid and biologically active ingredient mixture. In the USA, the environmental protection agency protocols are very much strict. Companies working in agricultural formulations need to obey such protocols. Such protocol governs the droplet size particle spray characterization. The droplet size of the formulation is crafted during designing state and often undergoes several levels of testing to ensure accurate spray characterization.

There are many parameters that can be used to characterize a spray like a droplet size, volume flux, spray angle, flow rate, operating pressure, etc. Many of these are highly critical in order to optimize a spray solution. The effectiveness of the nozzle and other sorts of material to be sprayed is greatly improved by complete acknowledge of the characteristic of the spray. Spray drift is dependent upon drop size characterization. Agricultural formulation once sprayed may diffuse to off-target location due to spray drift as well as runoff from the plants and soil. This has a severe effect on human health and environmental damage. Herbicide volatilization is one of the cases that are highly affected due to spray drift it happens due to evaporation of volatile herbicide and generally loses its intended target.

The impact of the spray drift is highly catastrophic to lives and environment. The farmers and kids playing around are the more targeted victim while wildlife and natural habitat are affected due to wind movement and soil contamination. To defend such calamity USDA and EPA are working together to make use of appropriate technology and chemical processes such as turbulence, droplet formation, droplet evaporation and soot generation by the companies. Typically, a variety of measurement techniques are employed to calculate parameters laid spray angle, spray thickness, droplet velocity, etc. Many companies operate on the principle of phase Doppler interferometry for measuring the size of the drop.

If you are unaware of the causes and proper measure spray drift, you would simply be giving rise to a cage for yourself and putting your life at stake. Research the market well and testify the spray nozzle before experimenting spray characterization. It is advisable to purchase only appropriate size spraying hydraulic nozzle. Keeping the EPA guideline in mind, companies are now more attentive in producing unified equipment for safer and healthy environment. Don’t invest money in local agricultural equipment. However, safety is in your hand don’t compromise with it. Remember you are also playing an important role in habitat so as rest of the being.