Bringing production lines up to full speed after a shutdown can cause off-spec product until processing parameters level off. Purina Mills' St. Joseph, MO, plant produces more than 150,000 tons per year of cattle, horse, chicken, hog and dairy feed. In an adjacent building, it also produces 4,000 tons per month of dairy pre-mix nuggets.

"We ship the 'nuggets,' or pellets, to other plants where they are used as part of a more complex feed," says Ed Cooper, maintenance manager at the plant.

While the nugget plant runs on a 24 hour, seven day a week schedule, processing lines periodically shut down for maintenance or changeover. "Restarting the processing lines invariably produces off-spec product until the hoppers and extrusion dies are full, and the dryers equilibrate at the appropriate temperature," notes Cooper. "During production some of the high fat/high protein product clings to the sides of the extruder, and comes off the fluidized dryer or cooler beds. The product is not contaminated, it is just not the right consistency or proper finished moisture." Under-processed product has the consistency of peanut butter, while semi-dried pellets are as low as 8 percent moisture.

Purina Mills was discarding almost five tons of product a day, sending it directly to a landfill, according to Cooper. "Our waste collection costs, reaching $4,000 per month, along with the lost product cost -- in excess of $100,000 -- was just unacceptable," Cooper says. The plant needed a way to liquefy the unusable product before portioning it back into the process. Cooper turned to Breddo-Likwifier for a solution.

A 300-gal. steam-jacketed mixer was installed on load cells and tied into the plant's PLC (programmable logic controller) system. "We start with 1,000 lb. of water in the mixer, heat it with steam then add about one ton of the off-spec batter and pellets," says Cooper.

Process-line PLCs were reprogrammed to automatically reduce water being added into a new batch, adjusting for addition of a portion of the reconstituted mass. Normal water quantities resume when rework addition is complete.

"We have had total success with the new system," says Cooper. "It is low maintenance, simple to operate and easily tied into current automation systems. As a result, we are reclaiming 80 percent of our waste as well as reducing landfill use."

Breddo-Likwifier Div., American Ingredients Co., 3947 Broadway, Kansas City, MO 64111. Tel.: (816) 561-9050; Fax: (816) 561-7778.