ITEM | ROTARY PRESS | BELT FILTER PRESS |
1. | Labour costs | Labour costs |
---|---|---|
The Rotary Press requires little attention. | To properly operate the BFP, it requires constant adjustment and attention. | |
2. | Airborne contamination | Airborne contamination |
Totally enclosed process. | Open process with frequent spills and sprays. | |
Sludge will not run on the floor. | Large air handling system is required to eliminate airborne contamination, corrosion and airborne pathogens. | |
3. | Spare requirements | Spare requirements |
Less | More – Higher initial investment in building space. | |
4. | Maintenance costs | Maintenance costs |
Maintenance is less frequent, simple and easy. | ||
Most maintenance can be performed by one person. | Many parts (bearings, belts, doctor blades, shafts, etc) require frequent maintenance and adjustment, and can cause shut down of the machine. | |
Equipment is very simple and reliable. | The complex equipment can easily become unreliable. | |
5. | Wash Water | 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). | |
52 USGPM/Channel for 5 minutes per day for a system flush. | Equipment to pretreat this water may be required. | |
(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. | |
This wash water poses an additional load on the plant since it is sent to the head works. | ||
6. | Capture Rate | 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%. | |
It depends how close the BFP is being operated to the optimum conditions. | ||
Analysis of the capture rate needs to take into account both filtrate and wash water. | ||
The solids from the filtrate and the solids from the wash water pose additional substantial loads on the plant. | ||
7. | Cake dryness | Cake dryness |
High | Lower | |
8. | Operation | Operation |
Simple and adjustments to the cake dryness are very easy. | Not so easy especially for inexperienced operators. | |
Normally a PLC is included for easy control. | The BFP requires continuous adjustment. | |
The control loops will allow for some variation of sludge. | ||
9. | Partial operations | 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. | |
10. | Shut-down procedure | Shut-down procedure |
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. | |
11. | Total maintenance and operation costs | Total maintenance and operation costs |
LOW | HIGH |