Spray dryer comprising a drying cylinder provided at one end with a spray nozzle and hot primary air injecting tube surrounding said nozzle has been known.
  In such a drying equipment, the products tend to deposit on the cylinder wall and recycle into the high temperature zone. In order to do away with such defects, various methods have been devised, but they all failed. One of the most commonly employed methods is the introduction of the hot secondary air concurrently to the main flow, but it is not so successful as expected.
  According to this, the above mentioned defects may be effectively overcome by introducing tangential air currents from the inlets arranged arround the discharge end of the cylinder. Within the cylinder, said air currents spirally flow along the cylinder wall and envelope completely the main flow consisting of the particles and hot primary air whereby the deposit of the products on the cylinder wall may be completely avoided. As said air currents fill the vacant space adjacent the spray zone the back eddying of the particle may also be effectively avoided.
  Finally, said spiral air currents turn their courses and flow back to the discharge end of the cylinder together with the main flow.
  The above mentioned function of the spiral air currents were observed through peep holes provided in the cylinder wall with the introduction of paper strips.
  It is to be noted that not whole of the said countercurrents follow the above mentioned courses, but small portion of said countercurrents flows back to the discharge end of the cylinder together with the main flow before reaching the spray zone.

Nano spray dryers refer to using spray drying to create particles in the nanometer range. Spray drying is a gentle method for producing powders with a defined particle size out of solutions, dispersions, and emulsions which is widely used for pharmaceuticals, food, biotechnology, and other industrial materials synthesis.

In the past, the limitations of spray drying were the particle size (minimum 2 microns), the yield (maximum around 70%), and the sample volume (minimum 50 ml for devices in lab scale). Recently, minimum particle sizes have been reduced to 300 nm, yields up to 90% are possible, and the sample amount can be as small as 1 ml. These expanded limits are possible due to new technological developments to the spray head, the heating system, and the electrostatic particle collector. To emphasize the small particle sizes possible with this new technology, it has been described as "nano" spray drying. However, the smallest particles produced are in the submicron range common to fine particles rather than the nanometer scale of ultrafine particles.

The functional principle is basically the same as with normal drying equipment. There are just different technologies that are used to do similar things.

The drying gas enters the system via the heater. A new kind of heater system allows for laminar air flow. The spray head sprays the fine droplets with a narrow size distribution into the drying chamber. The droplets dry and become solid particles. The solid particles are separated in the electrostatic particle collector. The exhaust gas is filtered and sent to a fume hood or the environment. The inlet temperature is controlled by a temperature sensor.

Painting and coating machine operators control the machinery and equipment that applies these paints and coatings to a wide range of manufactured products. These workers use several basic methods to apply paints and coatings to manufactured articles. For example, dippers immerse racks or baskets of articles in vats of paint, liquid plastic, or other solutions using a power hoist. Tumbling barrel painters deposit articles of porous materials in a barrel of paint, varnish, or other coating, which is then rotated to insure thorough coverage.

Commonly, paints and coatings are applied by spraying the article with a solution. Spray-machine operators use spray guns to coat metal, wood, ceramic, fabric, paper, and food products with paint and other coating solutions. Following a formula, operators fill the equipment's tanks with a mixture of paints or chemicals, adding prescribed amounts or proportions. They screw nozzles onto the spray guns and adjust them to obtain the proper dispersion of the spray, and hold or position the guns to direct the spray onto the article. The pressure of the spray is regulated by adjusting valves. Operators check the flow and viscosity of the paint or solution and visually inspect the quality of the coating. They may also regulate the temperature and air circulation in drying ovens.

In response to concerns about air pollution and worker safety, manufacturers are increasingly using new types of paints and coatings on their products instead of high-solvent paints. Water-based paints and powder coatings are two of the most common. These compounds do not emit as many volatile organic compounds into the air and can be applied to a wide variety of products. Powder coatings are sprayed much like liquid paints and heated to melt and cure the coating.

The switch to new types of paints is often accompanied by a conversion to newer, more automated painting equipment that the operator sets and monitors. Operators position the automatic spray guns, set the nozzles, and synchronize the action of the guns with the speed of the conveyor carrying articles through the machine and drying ovens. The operator may also add solvents or water to the paint vessel that prepares the paint for application. During operation, the operator attends the painting machine, observes gauges on the control panel and randomly checks articles for evidence of any variation of the coating from specifications. The operator then "touches up" spots where necessary, using a spray gun.

Painting and coating machine operators use various types of spray machines to coat a wide range of products. Often their job title reflects the specialized nature of the machine or the coating being applied. For example, paper coating machine operators spray "size" on rolls of paper to give it its gloss or finish. Silvering applicators spray silver, tin, and copper solutions on glass in the manufacture of mirrors. Enrobing machine operators coat, or "enrobe," confectionery, bakery, and other food products with melted chocolate, cheese, oils, sugar, or other substances.