Sewage sludge contains a large amount of water but, after drying, a considerable amount of combustible material and ash remains.
The cement industry can dispose of this harmlessly and safely using high temperature waste heat and simultaneously utilize not only the combustible material as fuel, but also the ash as raw material.
For the efficient utilization of sewage sludge, Taiheiyo Engineering Corporation and Taiheiyo Cement Corporation have developed a breakthrough drying technology using the preheated raw meal.

Features

  1. Low investment cost / Less installation space

    • Compact system can be made thanks to the high performance heat transfer (by the contact of high temperature raw meal and sludge with big surface area per unit volume).
    • This system can be installed with low investment cost, less space and short time, so it enables quick cost recovery.
  2. Stable kiln operation / Least impact to clinker production

    • From this system, dried powder is fed to the kiln.No adhesion or volume increase from moisture happens. This helps maintain the stable kiln operation. Comparing with direct (wet) sludge utilization system, clinker production reduction is almost eliminated.
  3. Less energy consumption

    • Since no moisture is fed to calciner (de-carbonation part), additional fuel consumption can be avoided. Also, heat value from sludge can be fully utilized.
  4. Denitrification (De NOx) effect (Conversion to low cost fuel)

    • The exhaust from sludge drying is brought to the outlet of bottom cyclone. Ammonia contained in sludge is utilized there as de-nitration agent. Further denitrification can be achieved by adding urea to the Reactor.
  5. Safety

    • The Reactor is designed not to introduce air (oxygen). Without concern for explosion, safe operation is secured.

Example of Flow

Performance Results for Taiheiyo Thermal Reactor (TTR)

No sewage sludge
(Benchmark)
Raw sewage sludge
(Direct feeding)
Taiheiyo Thermal Reactor (TTR)
Sewage sludge feeding rate (t/d) 0 90 172 200
Clinker production (t/d) 4370 4141 4370 41621)
Increase in heat consumption
(KJ/kg clinker)
148 98 138
1) unadjusted value

Technology comparison for sewage sludge in a cement kiln

System for utilization of sewage sludge
Taiheiyo Thermal Reactor (TTR) Direct feeding to preheater Direct heating by hot gas Indirect heating by hot gas, etc.
Maximum feed rate of sewage sludge ×
Water content after drying
Clinker production ×
Energy saving for clinker production ×
Capex for sewage sludge utilization ×
Opex for sewage sludge utilization × ×
Construction period × ×
Effect on kiln operation ×
Safety
Heat transfer efficiency × ×
Controllability
Key:  ◎ = Very good    ○ = Good    △ = A little poor    × = Poor