The formal mechanisms for monitoring or even controlling greenhouse gases (GHGs) in the United States have not been defined. The EPA and the government have not yet implemented any meaningful legislation. But now is the time to start preparing, nonetheless.

Protection of the environment is a reality that we are going to have to deal with. We can run but we cannot hide: the United States houses approximately 5 percent of the world population, yet we are responsible for more than 25 percent of the world's pollution.

Plastic processing is a major part of the process heating world. Among the process methods for plastics are thermoforming, compression molding and roto-molding.

In injection-molding, plastic pellets are introduced -- with or without other additives such as color, mold release agents and lubricants -- from a hopper into the molding machine. This feeding system is common to most plastic-forming processes.

By special request, the "What's That Process?" file is being extended to include other process heating topics that do not specifically relate to drying. This month, I’ll begin a look at extrusion.

Distillation involves the separation of components of a mixture, most commonly a liquid, by producing a gas or a vapor and then condensing the so-formed vapor. Distillation is used extensively in the fractionation of volatiles and other organic compounds. Multistage distillation is common to achieve the final or various intermediate fractions. How is this different than dehumidification?

Drying is just one of a myriad of industrial heat and mass transfer operations. I am frequently asked questions such as "What is the difference between drying and evaporating?", or "drying and curing," or "What is roasting and what is calcining?" These processes are related but distinct enough to be characterized.

Condensation problems frequently occur during or soon after a plant shutdown. This is because exhaust air is allowed to cool down inside the dust collector, which permits moisture to condense, forming moisture droplets on the surfaces. To avoid this potential trouble spot, be sure that the dryer goes through a shutdown cycle that will stop the feed, purge the moisture-laden process gas and allow the gas to slowly cool under atmospheric humidity conditions.

Implicitly, exhaust streams in dryers contain moisture. If this moisture is permitted to condense, it will create a "sticky situation" and lead to blinding, buildup and bridging. So, how do you deal with these evils?

Many drying systems employ reverse-pulsing dust collectors to control the solid particulate emission and recover the final product. The physical action of reverse pulsing releases a volume of compressed air at a substantially higher pressure than the operating or atmospheric pressures. On expanding, the air "shocks" the bag, effectively shaking the media and, together with certain inducing devices, forces air in the opposite direction, the reverse of the exhaust airflow.