Sludge Dryer

K-S Paddle Dryer for Sludge and By-products Drying

The K-S Paddle Dryer is used worldwide for drying a variety of sludges and by-products, generating dry stable products reducing disposal cost and converting waste into marketable by-products. Drying also allows some wastes to be used as fuel.

Dual counter rotating shafts with unique intermeshing wedge shaped paddles produce uniform heating and high heat transfer rates. The use of hollow paddles for heat transfer results in a compact machine. Indirectly heated with steam or recirculated thermal fluid (hot oil) the K-S Paddle Dryer has a thermal efficiency of approximately 98%. Non-condensable gas from the indirect dryer that might require treatment for odors is minimal.

For the indirect drying of biosolids and biological sludge visit K-S Biosolids Dryer

For process/production applications visit K-S Paddle Dryer & Processor

Sludge Dryer Top View Sludge Dryer Large SludgeDishes


After mechanical dewatering, further weight reduction and stable products can be obtained by thermal processing (drying) sludges, biosolids, and by-products. K-S has experience in chemical plants, petrochemical plants, refineries, pharmaceutical plants, food processing plants, corn wet milling plants, ethanol facilities, metal processing/finishing plants, mineral processing plants, and pulp & paper mills.

  • Achieve 90+% dry solids (99+% if desired)
  • Achieve intermediate dryness for composting or incineration
  • Produce stable and marketable products
  • Reduce disposal cost
  • Increase fuel value
  • Re-process residuals and tailings
  • Removal of hazardous volatile organic compounds (thermal desorption)

Biological sludge (secondary sludge, waste activated sludge (WAS) or biosolids)

Biological sludge is difficult to dewater, creating disposal problems at landfills. Thermal drying the sludge to 90+% is possible. For details on this application go to K-S Biosolids Dryer

Primary clarifier sludge and blended sludge

Many industrial plants produce primary sludge from a settling process. These sludges may be the result of chemical reactions that produce precipitates. This sludge may be blended with a smaller portion of secondary biological sludge. Chances are Komline-Sanderson has experience with your sludge

Meat/poultry processing, Gelatin plant waste can be dried to produce stable by-products.

Metal Hydroxide filter cakes, metal sulfide filter cakes, oxides and tailings from metal processing/finishing plants and mineral processing plants can be dried with the K-S Paddle Dryer. If reclamation of the metal is to be done then drying to very low moistures <1% (99+% dry solids) is desired. If land filling is being considered dryness of 80 to 85 % is suggested, as dryer material might be dusty

Soil remediation processes benefit from the removal of water and volatile organic material prior to more costly high temperature processes. This is referred to as thermal desorption

Pulp and paper mill sludge

Most mills blend the primary and secondary sludge. K-S recommends segregation of the sludges so the hard to dewater secondary sludge is dewatered separately and dried in the K-S Paddle Dryer. This allows dewatering of the primary fibrous sludge to a high solids concentration with a screw press. This approach also results in greatly reduced chemical conditioning cost. Blending 90+% dry solids secondary sludge with the primary sludge cake produces a high quality fuel for the boilers

De-inking mill sludges containing fine fiber, fillers and ink are ideal for the K-S Paddle Dryer. Dried to 60 to 70 % ds this material is an excellent landfill capping material


  • High thermal efficiency
  • Low off-gas quantity resulting in simplified air permitting
  • Cost effective and environmentally sound
  • Continuous process can be operated 24 hours per day or for a portion of a day
  • Easy to operate, requires minimal attention
  • Accepts a wide variety of feeds: slurry, paste, cake, granular, or powder
  • Safer than direct drying
  • Durable design results in low maintenance
  • Enclosed process eliminates fugitive emissions


  • Heat transfer areas from 60 to over 3000 square feet (5.6 to over 305 square metres) per dryer
  • System capacities for small, medium and large plants
  • Indirectly heated using steam or thermal fluid (hot oil)
  • Designed, constructed, and stamped per ASME Code or PED
  • Carbon steel, stainless steel, or alloy construction
  • Abrasion-resistant hard-surface coatings are available
  • Inert process during operation
  • Robust design, designed with 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 using steam or thermal fluid (hot oil). High-energy efficiencies and low off-gas volumes are characteristics of a K-S Drying 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 costs.

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.

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.


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 drying system. K-S can also supply an entire sludge processing plant, including equipment for pumping, thickening, dewatering, drying, and off-gas processing.


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, performance, and the superior customer service are all trademarks of a K-S installation.

Safety features must be part of the system design. The indirectly heated K-S Paddle Dryer operates with an inert low temperature environment. Gas (air) is not used to convey a hot product in the dryer. The totally enclosed process eliminates fugitive emissions.

Low temperature operation creates a safer operation when processing combustible materials. When very low residual moistures are needed (99 + % ds) or when non-heat sensitive materials are being processed high temperature heating can be used.

Typically 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 may require treatment for odors, is minimal.

When needed deflagration vent panels are incorporated into the dryer cover. These are ducted outside of the building. An automatic water deluge system can be incorporated into the dryer to cool combustible material, in the event of a high temperature condition. Inerting the dryer with inert gas is also an option.


  1. What are the energy requirements for drying?

    The energy requirements vary depending on the feed moisture content, the final dryness desired and the choice of heating mediums (steam or thermal fluid).

    Example: Our dryer needs 1155 BTU per pound of water removed to dry material from 20 % ds to 90 % ds. If a steam boiler is used the boilers efficiency is typically 80 %. Thermal fluid heaters can have thermal efficiencies of 80 % to 88 % depending on design. Energy recovery should be considered if the plant has hot stack gases.

  2. How is the dryer sized?

    The hourly feed rate is determined and the total heat load calculated (Q). The heating medium temperature establishes the temperature differential (driving force, dT). The heat transfer coefficient (U) is dependent on the material being dried. This is established by using data from prior experience and test data. With these variable established the heat transfer area (A) is calculated by:

    A = Q/(U x dT)

  3. What steam pressure is required? What thermal fluid temperature is used?

    For drying of most materials we limit the heating medium temperature to 380 to 400 °F. For heat sensitive materials much lower temperatures are used. When low heating temperatures are used a larger dryer is required. For drying of inert materials much higher heating mediums temperatures can be used (up to 750 °F).

  4. Does K-S offer lab and pilot testing?

    Yes, K-S can provide pilot testing at our Technical Center or at your plant. Information on our test programs is provided in “References”.