Thermal Drying Helps Producer Meet Quality Standards

BY PIERLUIGI PIACENTINI AND RUDOLF BOGNER

Italcanditi, a producer of candied fruit, jams, and preserves located in Pedrengo, Italy, needed to treat biological waste-activated sludge to reduce sludge volume and contain disposal costs. The candied fruit producer decided on a thermal drying system from Siemens Water Technologies. Italcanditi selected the dryer because of the technology’s high reliability and safety, small footprint, low maintenance, and minimal operator attention required.

Since the dryer started up in early 2010, it has helped reduce the facility’s biosolids disposal costs by 80%. Prior to installing the dryer, the facility sent its sludge to landfill. Drying the sludge onsite has helped to lower the volume of the final dry product, reducing landfill disposal costs by five-fold. The dryer also allows the candied fruit producer to recover approximately 40% of heat from existing cogeneration, resulting in energy savings.

The 250 kg/hr evaporation capacity drying system operates 16 hr/day and has a flow rate of 300 kg/hr. The dry solids content in the dewatered sludge ranges from 15 – 20%, and in the dried sludge, from 85 – 90%. The end-product is dust-free and stabilized. Its dry granular form also simplifies storage, delivery, use, or disposal and makes it suitable for agricultural reuse.

Additionally, energy recovery from cogeneration makes the thermal energy requirement particularly low. Other advantages include high energy efficiency, minimal environmental impact, and agriculture-grade pathogen reduction.

How It Works

The high thermal efficiency, low emissions sludge belt dryer from Siemens Water Technologies is suitable for heat recovery from low temperature waste energy sources. The process is flexible enough to face great changes in the inlet product, as it can regulate both the process air temperature and the belt speed – the latter to provide varying residence times.

The sludge belt dryer is a convective dryer, with evaporation taking place when the biosolids come in contact with the heated air. Capacity for a single dry-ing line ranges from 250 to 6,000 kg/h of evaporated water, with biosolids evenly distributed on the entire belt width to cause uniform evaporation. The heat requirement is around 800 kcal/kg of evaporated water.

Quality Is Key

Italcanditi offers a wide range of products, a few of which include candied fruit; fruit preparations for yogurt and ice cream; jams and marmalades; cream fillings for bakery products; and ready-to-eat vegetables.

About the Authors: PierLuigi Piacentini is marketing director for Siemens S.p.A’s Water Technologies Business Unit. He is located in Casteggio, Italy and can be reached at [email protected]. Rudolf (Rudi) Bogner is biosolids business development director for Siemens Water Technologies. He is located in Erlangen, Germany, and can be reached at [email protected].

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