Chemical plants end up with wet solids in many forms: filter cake from a reactor, salt from a crystalliser, sludge from the effluent plant. Each has a different problem. One is corrosive, another is sticky, a third gives off solvent. A paddle dryer can handle many of these, but only when it is built for the specific material.
Why chemical drying is different from sludge drying
Effluent sludge is mostly a disposal problem. Chemical wet cake is often a product, so purity, final moisture and what leaves the machine all matter. You also have to deal with what comes out as vapour, which may be water, solvent or both.
The questions that decide the design are:
- Is the material corrosive, toxic or reactive?
- How sensitive is it to heat, and at what temperature does it change?
- Does the vapour contain solvent that must be recovered or scrubbed?
- Must the product stay free of contamination from the machine?
- How sticky is the cake in the middle of drying?
How a paddle dryer suits chemical duty
- Indirect heating. The heating medium never touches the product. Steam, thermic fluid and hot water are all options, and AS Engineers states a thermic fluid range up to 400°C and steam up to 14.06 kg/cm².
- Enclosed operation. The machine is closed and can be purged, which helps with solvents and with dust.
- Pressure options. It can run at atmospheric pressure, under vacuum or pressurised. Vacuum lowers the drying temperature for heat-sensitive material.
- Solvent recovery. Vapour can go to a condenser and solvent tank, with a scrubber for what remains.
- Materials of construction. Carbon steel, SS304, SS316, duplex steel and other alloys, with surface finish options including buffing, hard facing and electropolishing.
- Self-cleaning paddles. Intermeshing paddles keep heated surfaces clear and run without metal-to-metal contact.
Materials in AS Engineers’ application list
AS Engineers lists these chemical and petrochemical materials among its paddle dryer applications: aluminium hydroxide, sodium chloride, ammonium nitrate, PTBBA powder, sodium cyanide and ammonium or sodium sulphate. In mining and metals it lists gypsum, manganese dioxide, copper concentrate, coal and lithium hydroxide.
Some of these need extra care. Materials that are toxic or thermally unstable require an enclosed design, controlled temperatures and a safe vapour route, and the right design only comes from a review of the actual material and a trial.
What to prepare before asking for a quote
- Material name, hazards and safety data sheet
- Current moisture and required final moisture
- Throughput in kg per hour
- Maximum safe product temperature
- Whether the vapour contains solvent and how much
- Any limit on contamination or metal pickup
Beyond drying
The same machine can also heat, calcine, strip solvents, crystallise, react or cool, as AS Engineers notes in its paddle dryer FAQ. If your process needs a heating or reaction step on a wet solid, ask whether one machine can do both.
Test your material first
Chemical materials rarely behave like the textbook example. 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: vacuum paddle dryer, filter cake dryer and how a paddle dryer works.
Related reading
- Sludge dryer manufacturer
- Materials we dry
- Pharma Paddle Dryer: Intermediates and Wet Cake
- Paddle Dryer for PET Chips, Polymers and Resins
- Paddle Dryer for Textile Sludge and ETP Cake
- Industries we serve
More from AS Engineers
See the full range on paddle dryers for the chemical industry at theasengineers.com.
For wider sludge background, read the chemical sludge treatment and reuse 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.
