In this series, I am going to talk a little about dryer selection. Selecting a dryer that is "optimal" for your application goes beyond recommendations. There is a lot involved in making this selection.
Let me first confer my definition of the optimal process or application. In-so-much as there is a fundamental difference between normal and average pertaining to statistics, there is a fundamental difference between "optimal" and "traditional" with regard to process applications. The traditional solution would be the most historically correct implementation of equipment for the specific process, without any consideration of the continuity of the operation and the overall application. Conversely, the optimal solution would be the most appropriate equipment installation, taking into account all associated circumstances for the entire process. The difference between optimal and traditional in an industrial sense is noncommercial; however, it cannot be totally divorced from dollars and cents.
Confusion AboundsGetting information to assist in this selection can be confusing. Most process heating equipment suppliers have a specialized and limited range of machinery that they supply. Their truly noble intent is to assist you in getting the optimal process for your application. However, their primary purpose, as it rightly should be, is to sell you their particular type of equipment. The problem here is that their brand range may not include the equipment that is truly optimal for your application. Often, this results in some unique and novel solutions - frequently, untried.
For example, a foreign company that specializes in fluid bed dryers received an inquiry for drying of wet dog food pellets. Clearly, fluid bed drying of wet agglomerated, extruded or pelletized feed solids is not optimal. The company cleverly devised a host bed technology to dry the product in a fluid bed dryer. The results were outstanding. Unfortunately, they are not always, and this can be considered more the exception than the rule. A large portion of any drying expert's or consultant's business is trying to remedy ill-conceived processes.
Thus, the onus is placed on you to source multiple vendors, at your cost if necessary, and to decide what the best process drying equipment is for your application. Often, you rely on the traditional option because it works and that is the way it has always been done. When the capital investment is high and there is demand from the market, the significance of this decision becomes far more critical.
Consider the Search ProgressionOne must first consider that a dryer is only one discrete component in a system. Even if the dryer works to specification, if it does not integrate with the system, your manufacturing and production can be seriously impeded. Many factors influence the selection of the optimal dryer for each application. Almost every process is unique. There are no standards. Even identical plants in different geographical areas can have environmental or handling considerations that would necessitate different types of dryers to dry the same end product.
The technology behind drying is as much art as science. The science would be the media the artist would use. The style of the artwork would be analogous with the art of conceiving the process of drying, taking every possible influence into account. A defined and tangible boundary to the types of drying equipment commercially available exists; this is the science. Again, the art is the perception and experience possessed to visualize and conceive the most elegant method of presenting the feed material to the heat source. You always want to expose as much surface area as possible: This is art.