|
ITEM
|
ROTARY
PRESS
|
THE
CENTRIFUGE
|
| 1. |
Simple
: |
More
complex : |
| |
A
single drive driving a single rotor. |
Two
(2) drives - A main drive and a back drive driving two (2) rotors, the bowl
and the scroll. |
| |
Low
maintenance. |
High
maintenance. |
| |
|
|
| 2. |
Low
speed: 0,5 to 2,5 RPM max. |
High
speed: 1500 to 3500 RPM |
|
|
No
(or very low) live floor loads. Nothing special is required. |
High
live floor loads. Building needs to be designed especially to deal with
these loads. |
| |
Reduced
noise: Nothing special is required. Acoustic protection is not required.
|
High
noise: Noise attenuation is required as part of the building construction. |
| |
Vibration
and temperature: Monitoring is not required for the Rotary Press. |
Vibration
and temperature: Monitoring of the electric motor, bowl and scroll is very
critical. |
| |
|
|
| 3. |
Low
Power Consumption : |
High
Power Consumption : |
| |
Low
installed HP and reduced power consumption: 10 kW-hr/dry ton. |
High
installed HP and high power consumption estimated at 171 kW?hr/dry ton*
. The additional power cost over the life of equipment is very significant. |
| |
No
consideration for power factor. |
Consideration
for power factor. |
| |
Reduced
installation costs for the electrical connection. |
High
installation costs for the electrical connection. |
| |
|
|
| 4. |
Simple
and short start-up and shut down procedures. |
More
complex and lengthy start-up and shut down procedures. Bowl may continue
to rotate for a while after shut down. |
| |
Frequent
stops and starts are possible. |
Frequent
starts and stops are not possible. |
| |
|
|
| 5. |
In
the event of an eventual shut down, repairs can be completed at the waste
water treatment plant by regular mechanics. |
In
the event of a shut down, the centrifuge may have to be shipped to the manufacturing
plant for specialized repairs. The centrifuge may require visits from specialty
mechanics. |
| |
|
|
| 6. |
For
a multi-channel machine, one or more channel(s) may be removed for maintenance
purposes, while the machine with the remaining channel(s) may still be operated. |
The
whole machine is in operation or it is shut down. |
| |
|
|
| 7. |
Vibration
analysis and preventative maintenance are not critical. |
Vibration
analysis and preventative maintenance are very critical. Additional
training of plant personnel may be required. |
| |
|
|
| 8. |
The
Rotary Press includes a flocculator with a variable speed agitator to optimize
flocculation and polymer dosage, which most likely results in a reduced
polymer consumption. |
Flocculation
takes place inside the centrifuge and cannot easily be controlled, and may
result in a higher polymer consumption and higher annual expenditures. |
| |
|
|
| 9. |
More
reliable: |
Less
reliable: |
| |
Very
few components of the Rotary Press may cause catastrophic shut down
of the equipment due to its low speed and simple design. |
Many
more components may cause a shut down due to the high speed and high
power. |
| |
|
|
| 10. |
A
high capture rate is intrinsic in the Rotary Press design giving a reasonable
flocculation. |
The
centrifuge will operate at a lower capture rate, which will reduce further
if left unattended. |
| |
|
|
| 11. |
The
effects of grit are greatly reduced in the slow-moving Rotary Press. |
The
centrifuge may be affected by the presence of grit in the sludge in the
form of unpredictable premature abrasion wear. |
| |
|
|
| 12. |
With
the Rotary Press, it is possible to obtain very high cake dryness at reduced
flow. |
The
same cake dryness may not be possible with the centrifuge. |
| |
|
|
| 13. |
No
external lube system is required. |
External
lubrication system is usually required. |
| |
|
|
| 14. |
Low
maintenance cost. |
High
maintenance cost. |
| |
|
|
| 15. |
Generally,
no shredder is required upstream. |
May
require a shredder upstream. |
| |
|
|
| *
According to an article written by Mr. Chuzo Nishizaki in the "The
Proceedings of the Management of Water and Waste Water Solids
for the 21st Century June 19-22, 1994" published by the Water Environment
Federation, U.S.A. (p 7?35). |
