- Biosolids Dryer System for Biosolids and Biological Sludge Drying



The Komline-Sanderson Biosolids Drying System uses indirect drying technology to convert municipal and industrial biological sludge into a sterile, free flowing granular product. The dried biosolids can be beneficially reused as a slow release nitrogen fertilizer, soil amendment additive or as a green fuel in a boiler and cement kiln. The K-S Biosolids Drying System produces an EPA classified Class A Biosolids.

The K-S Paddle Dryer is used worldwide for the drying of biosolids and biological sludges. The first Komline-Sanderson United States municipal biosolids installation was commissioned in 1991. Since the early 90's Komline-Sanderson has also sold and commissioned many industrial biological sludge dryers.

Biological sludges (primary solids, secondary sludge, waste activated sludge (WAS), digested sludge) generated in the biological processing of wastewater to reduce BOD and COD can be dried in the K-S Paddle Dryer to reduce disposal cost and produce marketable by-products such as fertilizer and fuel.

  • Achieve 90+% dry solids
  • Produce Exceptional Quality Class A sludge
  • Achieve intermediate dryness for composting or incineration
  • Reduce disposal cost
  • Produce stable and marketable products
  • Increase fuel value

  • High thermal efficiency
  • Low quantity of odorous off-gas, easy permitting
  • Cost effective and environmentally sound
  • Easy to operate, requires minimal attention
  • Continuous process, no recycle required, no pre-conditioning of the feed
  • Safer than direct drying
  • Durable design results in low maintenance
  • Can be operated 24 hours per day or for a portion of a day
  • Enclosed process eliminates fugitive emissions
  • Low overall temperature results in a safer operation

  • Heat transfer areas from 60 to over 3300 square feet (5.6 to over 305 square metres) per dryer
  • Large capacity systems
  • Indirectly heated with steam or thermal fluid (hot oil)
  • Designed, constructed, and stamped per ASME Code or PED
  • Stainless steel process surfaces with abrasion-resistant coatings on selected areas
  • Inherently safe due to low oxygen levels during operation
  • Robust design, designed for high torque and low operating speed
  • No internal parts to adjust or maintain
  • Shafts, bearings, and drive components are designed for long life under adverse conditions, insuring long-term mechanical integrity


The K-S Paddle Dryer provides a reliable and efficient method for drying filter cakes and centrifuge concentrates. The K-S Paddle Dryer is indirectly heated with steam or thermal fluid (hot oil). High-energy efficiencies and low off-gas quantities are characteristics of a K-S System.

The K-S Paddle Dryer is an indirect heat transfer device that utilizes mechanical agitation to enhance contact with the product being dried. Dual counter-rotating shafts with unique intermeshing wedge-shaped paddles produce intimate mixing, optimize heat transfer, and provide a self-cleaning effect.

A large heat transfer area to volume ratio is achieved by the use of hollow paddles and a jacketed vessel, through which the heating medium flows. The result is an efficient, compact machine with less space requirements and lower installation cost.

Indirect dryers have a metal wall that separates the process mass from the heat source. High thermal efficiency is obtained because the heat from the thermal medium goes directly into the process mass. As the material comes into contact with the heated trough and agitators, the process mass is heated via conduction. The insulated dryer has very little heat loss.

The K-S Paddle Dryer transports material, regardless of its handling characteristics. Pre-conditioning the feed by mixing with recycled dried product, to make it conveyable, is not required. This results in a safer operation and lower capital, operating, and maintenance cost.

As sludges dry they go through a number of transitions in handling characteristics. These changes are directly related to the solids content. For example, extremely wet sludges and extremely dry sludges require substantially less torque than sludges in the plastic-sticky-phase, when high torque is required. The K-S Paddle Dryer is designed with high torque capabilities to increase its process flexibility. Extra torque keeps you on-line, even during upset conditions.

Material is conveyed through the K-S Paddle Dryer by displacement. As material is added to the dryer, it is assimilated into the bed by the mixing action of the agitators. Hydraulic head pressure, combined with the action of the wedge-shaped paddles, pushes material around and through the paddles.

No external sweep gas is required. Exhaust gas is minimal and at a low temperature. Therefore, the volume of non-condensable gas from the dryer, which requires treatment for odors, is minimal.

K-S process and project engineers provide assistance at all phases of the project. Depending on your specific requirements, K-S can provide you with a dryer, or a complete system.

A successful plant depends on the integration of the key process units with properly selected ancillary equipment and the right facility design. Reliability, ease of operation, rugged construction, proven performance, and superior customer service are all trademarks of a K-S installation.

A K-S Biosolids Drying System includes a feed storage bin or silo and metering pumps (or conveyors). Dry product is cooled prior to storage or transport. When desired the final dry granular product can be screened to remove fines.

The off-gas volume is very low and at a low temperature. Odor treatment options include: direct injection into the aeration basin, bio-filters, scrubbers, absorbers, and thermal destruction.

Safety features must be part of the system design. The indirectly heated K-S Paddle Dryer operates with an inert low temperature environment. Air is not used to convey a hot product in the dryer.

Low temperature operation creates a safer operation:

  • Heating medium less than 400 °F (205 °C)
  • Vapor temperature less than 210 °F (99 °C)
  • Product temperature after dryer less than 260 °F (127 °C)
  • Product temperature after cooler less than 120 °F (50 °C)

Deflagration vent panels are incorporated into the dryers cover. These are ducted outside of the building. An automatic water deluge system is incorporated into the dryer to cool the biosolids in the event of a high temperature condition.

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