Nonlinear Chemical Dose Controller
Abstract
Figure 1: Nonlinear CD Design
The nonlinear chemical doser (CD) is designed for turbulent chemical does flow rates. The previous CD design for a linear CD requires that the chemical flow in the dosing tube beis laminar. This The linear CD-design- uses the relationship between laminar flow and major losses in the doser tube to maintain a constant chemical dose with varying plant flow rates. However, when the flow in the dosing tube is turbulent, the linear relationship no logner longer exists. In this case, a nonlinear CD, one that uses minor losses to control flow rates, is necessary can be used to maintain a constant chemical dose with the varying plant flow rates.
Add a description of how the plant flow measurement device must be matched to the CDC. Include the equations that show that the relationship between flow and height must have the same power relationship.
The advantage to designing a nonlinear CD is that higher chemical flow rates can be used. In larger water treatment plants larger chemical flow rates are necessary to dose alum and chlorine. The limit of the currentlinear flow control module is 400 ml/min. This maximum flow has been adequate for the plants currently in operation (La 34, Ojojona, Tamara, Marcala and Four communities) given their flow rates.
It was necessary to use two flow controllers at Marcala.
The link to the flow controller doesn't discuss the orifice issue. Define this problem clearly. What orifice causes the problem and why can't that problem be solved? Are you sure this is a constraint?
Methods
The nonlinear doser uses a dose control orifice (minor losses) instead of a dosing tube (major losses) to control the relationship between changing plant flow rates and chemical dose. The entrance to the rapid mix tank is also an orifice. Therefore, the relationship the total plant flow rate and the height of water in the entrance tank and the relationship between the chemical flow rateboth plant and chemical flow rates are dominantly controlled by an orifice. The CD uses a lever arm to increase head in the flow control module when the plant flow rate increase. The increase in head driveslinks the chemical flow rate to increase with the plant flow rate. The relationship between chemical dose and turbidity is changed manually in the same fashion as for the linear CD.
A lever arm similar to the linear CD lever arm will be used to relate plant flow rate to alum flow rate. A larger dosing tube is required to minimize major losses. This tube must be flexible to accommodate lever arm motion. Flow will be channeled through the dose control orifice into a channel. This channel will deposit chemical flow into the appropriate
What is the �appropriate� location?
Figure 2: Flow Controller for Nonlinear module
To reduce head loss through the flow control module orifice, a new flow controller is being used in the design. The module being used is a PT 75 LS Kerick Valve. This valve was chosen to minimize flow control module size and maximize orifice area. The flow controller will be housed mounted in a square tub.
Document the design of the panel valve. Distinguish clearly between the three orifices that are used (plant flow leaving the entrance tank, chemical flow leaving the dosing tube, and chemical panel valve). Is it important that the constant head tank be square? The tank in the image is rectangular.