Process of drying and pelletizing sludge in indirect dryer having recycled sweep air

Patent · Tue Jun 01 00:00:00 EDT 1993

OSTI ID:6528877

Girovich, M J

A process for treating liquid sludge obtained from a waste water treatment plant is described, comprising the steps of: dewatering the liquid sludge to obtain a dewatered sludge product, mixing a pellet forming nuclei substance into the dewatered sludge to produce a mixture, inputting the mixture into a dryer that performs indirect heat drying and simultaneous pelletizing of the mixture by coating the nuclei with the dewatered sludge during mixing and drying to build up the pellets layer by layer to a predetermined size; supplying sweep-air to the dryer for removing an air and water vapor mixture from the dryer; extracting a dried product and the air and water vapor mixture from the dryer separately from one another; cleaning and condensing the air and water vapor mixture to obtain a noncondensible gas; recycling the noncondensible gas to the dryer for use as said sweep air; classifying the product exiting the dryer into on-spec and fines fractions, wherein the fines fraction is smaller in size than the on-spec fraction; and recycling the fines fraction for use in said mixing step, wherein said pellet forming nuclei substance consists essentially of the fines fraction.

• Assignee: Bio Gro Systems, Inc., Annapolis, MD (United States)
• Patent Number(s): US 5215670; A
• Application Number: PPN: US 7-801656
• OSTI ID: 6528877
• Resource Relation: Patent File Date: 2 Dec 1991
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
SLUDGES
WASTE PROCESSING
DRYING
LIQUID WASTES
MIXTURES
PELLETIZING
WASTE PROCESSING PLANTS
WASTE WATER
WATER REMOVAL
DISPERSIONS
FABRICATION
HYDROGEN COMPOUNDS
INDUSTRIAL PLANTS
MANAGEMENT
MOLDING
OXYGEN COMPOUNDS
PROCESSING
REMOVAL
WASTE MANAGEMENT
WASTES
WATER
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)