2
TESTING AND FILTER SIZING
The plant operator typically sets a maximum permitted
moisture. Accordingly, the first step is the selection and
sizing of the filter which has to consider the major proj-
ect parameters. In the project described here these are as
follows:
• Plant location: Eastern Europe
• Kind of plant: Gold and copper mine
• Plant elevation: about 500 masl
• Ambient pressure: about 95 kPa
• Total solids throughput: 170 t/h
• Max permitted moisture: 23 w/w-%
Test Sample
The key for a proper sizing of the filtration equipment is
a representative sample of the tailings. In many cases the
operations are taking samples over a period of several weeks
or months and pick three samples:
a. a sample representing the best case for filtration,
b. a sample representing the nominal case for filtration.
c. a sample representing the worst case for filtration
Other plants are taking samples already from areas that will
be mined in the next few years and simulate the processing
in the lab. This is a good way to get prepared for the condi-
tions of tailing filtration in the next few years.
The gold and copper plant provided two samples, the
nominal case and the worst case. But the worst case was
expected during about 25 %of the time. Therefore, the
decision was made to do the filter sizing on the worst case
scenario. If the time for worst case filter feed would be 5 %
or less, it would be valuable to discuss the opportunity of
accepting higher moisture, less solids throughput or higher
amount of flocculant dosage during this limited period of
time. But with 25 %of the operation time such a discus-
sion did not made any sense.
The properties of the sample representing the worst
case scenario was as follows:
• d20 =3,6 µm
• d50 =23,1 µm
• d20 =92,4 µm
• solids density: 3,1 t/m3
• pH =9 …10
• solids content: 50 w/w-%
• Temperature: ambient
Now all data was available for lab testing.
Moisture content
The first step in the lab is to check whether the target mois-
ture, which was 23 wt% in this case, can be reached with
vacuum or does it require pressure filtration.
Figure 2 shows the moisture of the filter cake plotted
versus the filtration pressure difference. Already, 40 kPa are
enough to get a moisture better than the maximum permit-
ted moisture of 23 w/w%. Therefore, vacuum filtration is
a suitable method to filter the tailings prior to mixing with
cement as the following calculation shows:
• The ambient pressure at the plant site is:
95 kPa
• The suction pressure of a standard vacuum pump is:
20 kPa
• This results in a maximum pressure difference of:
75 kPa
• The pressure loss of a modern vacuum disc filter is:
10–20 kPa
• This results in an available pressure difference of:
55–65 kPa
Figure 1. Filter building options for mine backfill and for
TSF
TESTING AND FILTER SIZING
The plant operator typically sets a maximum permitted
moisture. Accordingly, the first step is the selection and
sizing of the filter which has to consider the major proj-
ect parameters. In the project described here these are as
follows:
• Plant location: Eastern Europe
• Kind of plant: Gold and copper mine
• Plant elevation: about 500 masl
• Ambient pressure: about 95 kPa
• Total solids throughput: 170 t/h
• Max permitted moisture: 23 w/w-%
Test Sample
The key for a proper sizing of the filtration equipment is
a representative sample of the tailings. In many cases the
operations are taking samples over a period of several weeks
or months and pick three samples:
a. a sample representing the best case for filtration,
b. a sample representing the nominal case for filtration.
c. a sample representing the worst case for filtration
Other plants are taking samples already from areas that will
be mined in the next few years and simulate the processing
in the lab. This is a good way to get prepared for the condi-
tions of tailing filtration in the next few years.
The gold and copper plant provided two samples, the
nominal case and the worst case. But the worst case was
expected during about 25 %of the time. Therefore, the
decision was made to do the filter sizing on the worst case
scenario. If the time for worst case filter feed would be 5 %
or less, it would be valuable to discuss the opportunity of
accepting higher moisture, less solids throughput or higher
amount of flocculant dosage during this limited period of
time. But with 25 %of the operation time such a discus-
sion did not made any sense.
The properties of the sample representing the worst
case scenario was as follows:
• d20 =3,6 µm
• d50 =23,1 µm
• d20 =92,4 µm
• solids density: 3,1 t/m3
• pH =9 …10
• solids content: 50 w/w-%
• Temperature: ambient
Now all data was available for lab testing.
Moisture content
The first step in the lab is to check whether the target mois-
ture, which was 23 wt% in this case, can be reached with
vacuum or does it require pressure filtration.
Figure 2 shows the moisture of the filter cake plotted
versus the filtration pressure difference. Already, 40 kPa are
enough to get a moisture better than the maximum permit-
ted moisture of 23 w/w%. Therefore, vacuum filtration is
a suitable method to filter the tailings prior to mixing with
cement as the following calculation shows:
• The ambient pressure at the plant site is:
95 kPa
• The suction pressure of a standard vacuum pump is:
20 kPa
• This results in a maximum pressure difference of:
75 kPa
• The pressure loss of a modern vacuum disc filter is:
10–20 kPa
• This results in an available pressure difference of:
55–65 kPa
Figure 1. Filter building options for mine backfill and for
TSF