| 1. Labour costs |
The Rotary Press requires little attention. |
To properly operate the BFP, it requires constant adjustment and attention. |
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2. Airborne contamination
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Totally enclosed process. |
Open process with frequent spills and sprays. |
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Sludge will not run on the floor. |
Large air handling system is required to eliminate airborne contamination, corrosion and airborne pathogens. |
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3. Spare
requirements |
Less |
More - Higher initial investment in building space. |
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| 4. Maintenance costs |
Maintenance is less frequent, simple and easy. |
Many parts (bearings, belts, doctor blades, shafts, etc) require frequent maintenance and adjustment, and can cause shut down of the machine. |
| Most maintenance can be performed by one person. |
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Equipment is very simple and reliable. |
The complex equipment can easily become unreliable. |
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| 5. Wash water |
No continuous wash water is required. |
The requirement for wash water is substantial 40 to 110 USGPM at 80 to 130 PSI (60,000 - 160,000 USG/day). |
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25 USGPM/Channel for 5 minutes per day for a system flush. |
Equipment to pretreat this water may be required. |
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(500 USG/day for a 4-channel unit). |
This wash water supply consumes power at a rate of 5-14 HP and needs to be considered in the overall analysis.
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This wash water poses an additional load on the plant since it is sent to the head works. |
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| 6. Capture Rate |
A high capture rate is intrinsic in the Rotary Press design and frequent adjustment is not required to maintain it high: 95% av. |
The capture rate may not be very good (less than 90%), and sometimes less than 65%.
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It depends how close the BFP is being operated to the optimum conditions. |
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Analysis of the capture rate needs to take into account both filtrate and wash water. |
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The solids from the filtrate and the solids from the wash water pose additional substantial loads on the plant. |
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| 7. Cake dryness |
High
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Lower |
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8. Operation
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Simple and adjustments to the cake dryness are very easy. |
Not so easy especially for inexperienced operators. |
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Normally a PLC is included for easy control.
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The BFP requires continuous adjustment. |
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The control loops will allow for some variation of sludge. |
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| 9. Partial operations |
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. |
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10. Shut-down procedure
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5-min system flush.Frequent shut-down and start-ups are possible. |
Thirty (30) minutes to one (1) hour plus time to wash down the belts and structural components of as required for a hygienic environment.
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| 11. Total maintenance and operation costs |
LOW |
HIGH |