Updated: July 2002
Pneumatic Dryer on Vehicle (PDV)1. Introduction
In municipals, an efficient treatment and disposal of dewatered sludge (DWS) is immediately needed because of the tendency that the disposal fee in the maintenance fee is increasing from year to year. The sludge treatment (SLT) at medium-sized and small-sized sewage plant is usually ineffective at the initial stage in the process, taking account of the operating ratio of equipment and maintenance fee.
For the municipalities which have small-sized sewage plants, it is effective to share the SLT equipment over administrative district. So PDV was developed with Nanao City and Japan Institute of Wastewater Engineering Technology as a model enterprise as safe and economical SLT system.
Drying system is to utilize the heated air of the exhaust gas (EG) from GT generator and small-sized stand-alone drying system that need not the external power supply source. By mean that the overall equipment is loaded on a vehicle, PDV carried out the SLT to make rounds of small-sized sewage plants.
2. General Outline of PDV
To use the dried sludge for the multipurpose, PDV in the picture is planned to decrease the volume of DWS by the heated air of the EG. PDV is the high-efficiency system because it needs not an air-heating furnace, which is applied in conventional dryers. It is easy handling and safety equipment.
To size down and load the equipment up a vehicle, the drying system is a pneumatic drying system at low temperature, and dried sludge is mixed with DWS to keep free-water content (FCW) low.
The process flow sheet of PDV is shown as figure. PDV is composed of the field-proven pneumatic drying system, GT generator, WG treatment system with scrubber, dry powder supply system. DWS that is transferred to PDV in pressurized piping is pulverized to granular powder and dried with heated air of WG at Mixing Machine and Pulverizer. Dried sludge and EG is separated at Cyclone Separator. Dried sludge is stored in Hopper and discharged to the flexible container. To suppress the foul odor, an activated carbon (AC) is added from Activated Carbon Feeder. After EG is removed the odor and the dust at Scrubber, it discharged from chimney.
[Spec. of PDV]
Capacity: 400 [kg-dried sludge/h]
FWC of DWS: about 85%
FWC of dried sludge: about 20%
Added ratio of AC: 2% vs. DS
Power supply source: GT Generator, 60[kj/s]
Total Weight: about 25[ton]
3. Characteristics
1) One PDV carries out the SLT of some sewage plants.
2) High efficiency energy system is achieved because of drying process by heated air of EG from GT generator.
3) Effective utilization of dried sludge.
4) Decrease of carbon dioxide
5) Reduce the concentration of the foul odor because of low temp. drying system.
6) Reduction of the initial cost as compared with conventional systems.
4. Performance
PDV has been operated in Nanao-Kashima district since 1999.
