污泥处理技术

REDOXAN SLUDGE REDUCTION
HARDPELLETIZER SLUDGE DRYER | ZEROFUEL® SLUDGE COMBUSTION

Keppel Seghers offers several sludge treatment solutions. The REDOXAN is an integrated, activated sludge technology. Both HARDPELLETIZER and ZEROFUEL® are stand-alone installations, for treatment of typcially larger volumes of wastewater treatment sludge.

Applications
Integrated solution for wastewater treatment plants working with activated sludge.

Advantages

• Enhanced digestion process for organic sludge from domestic or industrial origin
• Excessive destruction of sludge by intelligent combination of fermentation processes with cracking/disintegration techniques
• Superior energy recovery by extreme conversion of organic material into biogas
  

Description
This extended high performance sludge treatment process treats primary and secondary sludge, as well as grease and fat, in a sequence of an anaerobic digestion followed by thermophilic aerobic treatment. A physical or (bio)chemical cracking of the remaining fraction increases the overall biodegradability and results in sludge removal efficiencies up to 99 %.

As a by-product, the methane gas is transformed into power production and makes the process extremely valuable.

This technology is suitable for municipal and industrial sludge in case alternatives as land filling, use as fertilizer and incineration are prohibited or too expensive.

Applications
Keppel Seghers HARDpelletiser sludge drying technology has been proven to handle successfully biosolids, municipal sludge and industrial sludge of varying types and origins (primary and secondary, raw and digested, physico-chemical, etc.).

Advantages

• Indirect dryer
• One step sludge drying and sludge pelletising
• Dust-free pellets
• Best thermal efficiency
• Highly reliable and maintenance free
• Minimal electric power consumption
• Safe operation

Description
In the 80's Seghers proactively developed its unique HARDpelletising process with evaporation. A vertical, multi-stage, indirect convective unit produces hard, round and dust-free pellets with more than 90% dry solids content in a single and safe operation.

Similar to the pearl formation process in an oyster, biosolids particles grow layer by layer and become hard pellets. This gentle process with efficient heat exchange and gravitation-aided biosolids movements results in low electricity consumption and reduction in operation and maintenance costs. The Keppel Seghers HARDpelletiser is available for all kinds of sludge and other biosolids with variable composition and for an evaporation capacity ranging from 50 to 15,000 kg H2O/h.

Integration of water evaporation and biosolids granulation into a single piece of equipment reduces investment costs for treatment of sludge. The vertical and compact design minimises the footprint, which is very important for high density areas.

The HARDpelletising process, with water evaporation, is strictly indirect and no oxygen is allowed into the system. Dust production is prevented through a straightforward and gentle process, and the operating temperatures are kept low. Fire and explosion risks are therefore totally eliminated.

Pellets produced by the HARDpelletiser are naturally round, hard, dust-free and with a narrow size distribution. The process ensures the stability and pasteurisation of the pellets. HARDpellets are of high hygienic quality and are easily handled, transported and stored for long periods of time. Hence, the HARDpellets can be used for many applications, ranging from soil improver and fertiliser to green fuel, depending on the sludge characteristics and the local environmental legislation.

Applications
Keppel Seghers' fluidised beds have proven to be an innovative solution for the efficient and complete combustion of

• mechanically dewatered sludge from wastewater treatment plants
• dried sludge
• sludge pellets

All types of low-caloric biosolids and sludges (up to 6 MJ/kg) can be incinerated in the ZEROFUEL®.

Advantages

• Easy and highly flexible operation
• High availability (>90%)
• Long lifetime of installations
• Advanced automated process control system
• Very low process emissions (CO, NOx)
• Staged combustion: secondary air injection optimised by CFD simulations
• Maximal volume and weight reduction of the waste with complete inertisation of the residues
• Efficient energy recovery by producing heat, steam or electricity
• Integrated flue gas cleaning

Description
The Keppel Seghers' fluidised bed combustion technology consists of a turbulent fluidized bed furnace with heat recovery. The proprietary air distribution system combined with a shallow bed ensures homogeneous, stable fluidisation at a wide range of operating conditions. The use of a shallow bed avoids formation of hot and cold spots, and prevents the occurrence of dead zones.

The ZEROFUEL® fluidized bed features an efficient internal energy recovery system, allowing for auto-thermal combustion of low-calorific sludge, i.e. the combustion air is pre-heated up to 650°C by internal heat recovery, resulting in a drastic reduction of the consumption of auxiliary fuel. In addition, the size of the furnace is significantly smaller than in conventional fluidised bed systems, and an innovative feed system distributes the sludge in small particles evenly across the entire surface of the bed.

The ZEROFUEL® sludge incineration process fulfils the three conditions (the 3 "T"s) to reach a perfect combustion:

• optimum temperature of 850°C,
• long residence time (> 2 s) and
• maximum turbulence.

The staged and controlled combustion process guarantees low CO and NOx emissions, and allows for operation at low excess oxygen levels.