CFID tank with 1 reaction phase and point-settling solid separation
ClassName
“CFIDPointsettler1PhaseReact”
Icon
“cfid”
Categories
all
Description
The model describes a continuous flow (and intermittent decanting, CFID) batch process, consisting of 3 phases:
· 1-step reaction phase
· settling phase, described by a point-settler model
· withdrawal (of the clarified water)
The water stream flows through the system and the sludge can be withdrawn continuously, during all three phases.
A ‘launch’ phase allows for accounting for multiple units operated in sequence.
The effluent flow rate, when the tank is full, is regulated by the weirs:
where:
· 
and 
are empirical factors (-), function of the type or width and of the design of the weirs respectively (see Annex)
· 
is the number of weirs (-)
· 
is the volume (m3) of the tank under the weirs
· 
and 
denote the volume (m3) and the surface area (m2) of the tank, respectively
During the reaction phase, the tank is assumed to be ideally mixed: the concentration of both the effluent- and the sludge stream therefore equals the concentration of the mixed liquor in the tank.
During the settling phase, no conversion process takes place and the point-settler model governs the solid/liquid separation process.
During the draw phase, the clarified water is withdrawn from the tank, at a constant flow rate (Q_Draw) until the volume reaches V_Min.
When water is withdrawn, the effluent contains only the non-settleable fraction of the particulate matter:
where:
· 
and 
denote the concentration (g/m3) of the generic i-th particulate component in the outflow and in the tank respectively
· 
is the fraction (-) of non-settleable suspended solids
Sludge can be wasted during all three phases and the concentration of particulate matter in the sludge stream is therefore:
where:
· denotes the concentration (g/m3) of the generic i-th particulate component in the tank
· 
represents a thickening factor (-)for the suspended solids
The specific Instance defines the Conversion Model that is in place and therefore the processes taking place inside the tank.
Energy consumption for aeration, mixing and pumping is estimated as follows:
where:
· 
is the oxygen concentration at saturation (g/m3)
· 
is the oxygen transfer coefficient (1/d)
· 
, 
and 
indicate the Oxygen Transfer Rate (g/kWh), the mixing energy per unit volume (kWh/m3/d) and the pumping energy per unit flow rate (kWh/m3) respectively
· and 
denote the tank volume (m3) and the effluent flow rate (m3/d)
Parameters
|
Name |
Description |
Value |
Units |
|
Q_Waste |
Desired waste flow |
240.0 |
m3/d |
|
f_ns |
Non-settleable fraction of the suspended solids |
0.005 |
--- |
|
F_Th |
Thickening factor |
2.0 |
--- |
|
V_Min |
Minimum volume of the tank |
0.0 |
m3 |
|
V_Max |
Maximum volume of the tank |
2000.0 |
m3 |
|
A |
Surface area of the tank below the weirs |
200.0 |
m2 |
|
N |
Number of weirs |
100 |
--- |
|
alfa |
Empirical factor function of weir type or width |
1 |
--- |
|
beta |
Empirical factor function of weir design |
1 |
--- |
|
F_Energy_FlowRate |
Energy per unit flow rate |
0.04 |
kWh/m3 |
|
OTR_Energy |
Oxygen Transfer Rate per unit energy inputted |
1800.0 |
g/kWh |
|
ME_unit |
Mixing energy per unit volume |
0.005 |
kWh/m3/d |
|
Kla_Min |
Lowest kLa that ensures adequate mixing |
20.0 |
1/d |
|
Mixing_When_Aerated |
Mixing is guaranteed while aerating? (0=yes, 1=no) |
0 |
--- |
|
Period |
Period (to compute periodic costs) |
1 |
d |
|
Parameters of the Category-specific Conversion Model |
|||
State Variables
|
Name |
Description |
Units |
|
C |
Concentration of the state components (vector) |
g/m3 |
|
V |
Volume of the tank |
m3 |
|
Q_In |
Influent flow rate |
m3/d |
|
Q_Out |
Effluent flow rate |
m3/d |
|
Q_Under |
Sludge withdrawal flow rate |
m3/d |
|
T |
Total duration of 1 cycle |
d |
|
T1 |
Total duration of the reaction phase |
d |
|
Kla_Actual |
Oxygen Transfer Coefficient |
1/d |
|
Temp_Actual |
Temperature |
°C |
|
State variables of the Category-specific Conversion Model |
||
Derived State Variables
|
Name |
Description |
Units |
|
M |
Mass of the state components (vector) |
--- |
Interface Variables
|
Name |
Terminal |
Description |
Value |
Units |
|
Inflow |
in_1 |
Inflow vector |
--- |
n/a |
|
Outflow |
out_1 |
Outflow vector |
--- |
n/a |
|
Underflow |
out_1 |
Underflow vector |
--- |
n/a |
|
AerationEnergy |
out_2 |
Energy for aeration |
--- |
kWh |
|
AerationPower |
out_2 |
Power consumption for aeration |
--- |
W |
|
MixingEnergy |
out_2 |
Energy for mixing |
--- |
kWh |
|
MixingPower |
out_2 |
Power consumption for mixing |
--- |
W |
|
PumpingEnergy |
out_2 |
Energy for pumping |
--- |
kWh |
|
PumpingPower |
out_2 |
Power consumption for pumping |
--- |
W |
|
Temp |
in_2 |
Temperature |
15.0 |
°C |
|
Kla_Launch |
in_2 |
kLa of the launch period |
50.0 |
1/d |
|
Kla_React1 |
in_2 |
kLa (of the 1st period) of the reaction phase |
50.0 |
1/d |
|
T_Launch |
in_2 |
Delay in the start-up |
0.0 |
d |
|
T1R1 |
in_2 |
Duration (of the 1st period) of the reaction phase |
0.075 |
d |
|
T2 |
in_2 |
Duration of the settling phase |
0.1 |
d |
|
T3 |
in_2 |
Duration of the draw phase |
0.025 |
d |
|
Q_Draw |
in_2 |
Desired withdrawal flow rate |
24,000 |
m3/d |
|
Interface variables (sensors) of the Category-specific Conversion Model |
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