A textile processing unit ends up with sludge from dyeing, washing and finishing. Much of it is collected through an ETP or a common effluent treatment plant, dewatered in a filter press and then stored as wet cake. It is heavy, coloured, often sticky and expensive to move.
Why textile sludge is difficult
- High moisture. Filter press cake is mostly water, so most of what you pay to haul is water.
- Stickiness. Dye and chemical content can make the cake tacky in the middle of drying.
- Variable composition. The mix changes with dye lots and process changes.
- Odour. Wet sludge smells, especially while stored.
- Disposal rules. The classification and disposal route depend on the sludge and on your state pollution control board conditions.
What drying changes
Take 1,000 kg of cake at 80% moisture. It holds 200 kg of dry solids. Dried to 20% moisture, the same solids become 250 kg. You remove 750 kg of water and cut the weight you handle and haul by 75%.
Dried sludge is also easier to store, and AS Engineers lists several uses for it: alternative fuel where the calorific value is high enough, bricks, cement production and agriculture. Whether any of these is permitted for your sludge must be checked against your local rules.
How a paddle dryer handles this duty
Heat goes through the jacket and hollow shafts, and two counter-rotating shafts with wedge-shaped paddles mix the cake continuously. The paddles intermesh without touching and clean the heated surfaces as they turn, which helps where the cake turns sticky. The plug flow carries the material from the feed end to the discharge end. The enclosed machine sends vapour to a condenser or scrubber.
The heating medium can be steam, thermic fluid or hot water, and the fuel behind it can be gas, wood, coal, LDO, electricity or briquettes. AS Engineers’ own fuel reference for 80% to 20% drying is 1 kg of wood for about 5 kg of sludge and 1 kg of coal for about 8.25 kg.
What to prepare before asking for a quote
- Cake quantity per day and operating hours
- Current moisture and target moisture
- Colour, stickiness and any abrasive or corrosive content
- Boiler or thermic fluid heater availability, and your fuel
- Where the dried product will go
- Space available for the dryer and exhaust equipment
Where it fits in the plant
The dryer sits after the filter press. A conveyor or sludge pump feeds it from a wet material silo, and a screw conveyor or bagging system takes the product away. Exhaust treatment, which may include a cyclone, scrubber and bag filter, finishes the line.
Test your sludge first
Textile sludge varies so much between units that a sample test is the safest first step. AS Engineers runs pilot trials on a 25 kg/hr paddle dryer, at its works or at your site, for a nominal fee that is waived on order. Request a pilot trial.
Related guides: sludge drying with a paddle dryer, sludge volume reduction and disposal cost and ETP sludge dryer.
Related reading
- Sludge dryer manufacturer
- Materials we dry
- Textile industry applications
- Paddle Dryer for Food, Starch and Agro Residue
- Pharma Paddle Dryer: Intermediates and Wet Cake
- Paddle Dryer for Chemical Wet Cake and Sludge
- Industries we serve
More from AS Engineers
See the full range on AS Engineers sludge dryers at theasengineers.com.
For wider sludge background, read the industrial sludge management guide on sludgedryer.in, AS Engineers’ sludge drying resource.
- B.E. Mechanical · GTU (2018)
- PGDBA, Operations · Symbiosis
- With AS Engineers since 2019
- Writes on paddle dryers, sludge drying & blowers
Karan Dargode leads operations and environmental health & safety at AS Engineers, an Ahmedabad-based manufacturer with over 25 years of experience in centrifugal blowers, industrial fans, paddle dryers, sludge dryers, and air pollution control equipment. He joined AS Engineers in July 2019 and has spent over six years building operational systems that support the company's engineering and manufacturing work.
