When excess humidity levels threatened to force one peanut processor to reprocess its warehoused product, an effective means of quickly reducing relative humidity levels was sought.
Clint Williams Co., Madill, OK, can grade, process and store up to 18 million lb of unshelled peanuts or 36 million lb of shelled peanuts. Peanuts arrive at the plant with a moisture content of 10%. While warehoused, moisture content is further reduced to 7% to maximize grade rating at sale.
After processing, the peanuts are kept in cold storage (38 to 42oF [3 to 5.5oC]) until shipped to market. During this period, moisture content is carefully monitored. Peanuts that become too dry lose weight; consequently, the sale value drops. Peanuts with greater than 9% moisture content exceed grading standards and lose value as well. Should moisture content reach 12%, the inventory becomes threatened by the likelihood of mold and mildew formation -- a catastrophic and costly occurrence.
Summer Humidity Creates Crisis
High summer humidity was threatening the peanut stores at Clint Williams Co. Shipping activity had been constant during the humid summer months, allowing outside air to regularly infiltrate the plant. As a result, humidity readings inside the cold storage areas climbed to 80 to 90% relative humidity."If moisture content continued to climb, we would have been forced to reprocess the inventories using heat," explained Ollie Hall, Clint Williams' plant manager. "This type of reprocessing would have kept us from shipping peanuts for three months and would have cost $800,000 to $1 million."
With the threat of a processing crisis days away, Hall sought the counsel of Larry Wickline, sales representative for Munters Corp., DH Div. Wickline informed Hall that due to his immediate needs, it was too late to purchase dehumidification equipment. However, Wickline offered another solution: emergency dehumidification services. These services provide temporary humidity control equipment to industry in short-term and crisis situations.
Within days, eight dehumidifiers were configured into a temporary dehumidification system. Testing showed falling humidity levels in the cold storage areas. The dry air produced by the dehumidifiers replaced the humid air inside the facility, drawing the moisture out of the peanuts.
The Results
Three weeks after the peanuts' moisture content had returned to desired levels, the fleet of eight rental dehumidifiers was reduced to two. The two remaining units controlled humidity levels in the plant, preventing moisture from being reabsorbed by the peanuts.The total cost of the equipment rental over a four-month period was $75,000. Compared to the prospect of $800,000 to $1 million in reprocessing and associated business delays, the rentals proved cost-effective.
"There is no doubt that without this equipment, we would have had to reprocess 11 million lb of shelled and 5.5 million lb of unshelled peanuts," said Hall. "The significant change in the conditions achieved within a few days was extremely important to proving how effective the long-term use of desiccant dehumidification would be." PCE
Sidebar: Desiccants Growing in Popularity
Using dry air in engineering applications is not a new idea. However, using desiccant dehumidification to extract moisture only has been employed in industrial applications during the last two decades. Years ago, engineers were not educated about desiccants. Only the few engineers who realized the benefits of desiccant technology used it in processing applications. Additionally, worker comfort was not the issue it is today, so using desiccants to control humidity for the sake of workers was not considered by management.
Due to their reliable nature, desiccants have grown in popularity in a number of industrial applications. Compared to refrigeration, desiccants are effective in removing moisture from air at a condition far from saturation or at extremely low temperatures.
Applications of Desiccant Dehumidification
Stringent indoor air-quality standards affect industrial applications in food, pharmaceutical and biomedical processing. Desiccant dehumidifiers offer a viable solution for controlling humidity and protecting product.Moisture Regain Prevention. Virtually every substance has some affinity for moisture. Moisture can make products stick together or affect critical dimensions. Because desiccant dehumidifiers are effective in controlling humidity and are efficient at low temperatures, they are used to prevent moisture regain in food and pharmaceutical processing operations; pharmaceutical, biomedical and semiconductor clean rooms; advanced composite materials handling and manufacturing; and safety glass laminating.
Corrosion Prevention. Ferrous metals such as iron and steel are known to corrode. Yet all materials corrode. Glass and pure crystals such as sodium iodide and lithium fluoride also can disintegrate quickly. Desiccant dehumidifiers can protect such materials from subtle, expensive forms of corrosion. Common applications include: lithium battery production, electronics protection and power plant lay-ups.
Condensation Prevention. When cold surfaces are surrounded by moist air, water vapor will condense on the surface. Desiccants are used to prevent condensation in injection of blow-molding processes, water treatment plants, cold product receiving rooms and optical polishing applications.
Mold and Fungus Prevention. Mold and fungus, present in most materials, can survive without moisture and remain dormant for decades. However, when moisture and a food source become available, mold and fungus can multiply rapidly. Moisture does not have to be in liquid form or on wet surfaces. For this reason, dehumidifiers are used in breweries, seed protection, cargo protection and storage of photographic film.
Product Drying. Most products are dried using hot air to vaporize moisture and carry it away. Often, however, hot air is either too slow or can damage the product. Desiccants can be used to dry temperature-sensitive products such as pharmaceutical powders, fish and other food products.
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