Chemical Dose Controller Design Program
This program will code for a general dose controller design and will incorporate the design into the Automated Design Tool. The doser design will be for a triple scale (three different orifices). See the CDC research team page for a more detailed explanation of this.
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Equations:
Target Alum Concentration:
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\large
$$
Q_
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= {{Q_P \times C_T } \over {C_C }} $$
Where,
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\large$$Q_
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$$
= Flow Rate of Alum Solution
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\large$$Q_
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$$
= Plant Flow Rate
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\large$$C_
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$$
= Target Alum Concentration
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\large$$C_
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$$
= Alum Concentration in the Stock Tank
Orifice Equation:
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\large $$ Q = K_
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A_
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\sqrt
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$$
Where,
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\large$$Q $$
= Flow Rate
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\large$$h $$
= Head Loss
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\large$$A_
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$$
= Area of the Orifice
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\large$$K_
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$$
= Orifice Constant
Rearranging the orifice equation,
Orifice Head Loss:
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$$
h_
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= K_
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{Q\ over A_{or^2 } \over {2g}}
$$
Major Head Loss:
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$$
h_
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= f {L\over {D}}V^2} \over {2g
$$
Where,
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\large$$f$$
= friction factor (dependent on Reynold's number)
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\large$$D$$
= diameter
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\large$$V$$
= velocity (Q/A)
Design Process:
Expert Inputs:
HL.ChemDoserMin = Minimum head loss required to have good control of the doser
User Inputs:
Q.Plant (HL.Plant) = Plant Flow Rate
Current set values:
C.DoserScaleAlumMax = Matrix of maximum plant alum concentrations for the doser at the highest plant flow rate
Code Calculations:
Constant head tank orifice size
Dosing tubes size to ensure orifice head loss is much greater than major loss in tubing
1. Calculate the position of the scale by calculating the lever arm length for the dosing side and the float side.
2. Calculate the head loss at each point of the scale.
3. Translate the vertical head loss into a horizontal distance along the scale from the pivot point.
4. Use the alum flow rates to calculate the dosing orifice diameters.
5. Calculate the minimum dosing tube diameters so that the major head losses in the dosing tubes (from constant head tank to the dosing orifice) can be neglected.
6.