Chemical Feeder System Feedback Control for Vacuum Metering
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Solution Overview
Problem
Existing vacuum chemical metering systems face inaccuracies due to variations in chemical properties, instability of chemicals like sodium hypochlorite, and issues with debris or entrained gases, which can lead to uncontrolled chemical flow rates and unnoticed failures.
Innovation Solution
A chemical feeder system with a flow rate sensor and controller that adjusts the metering device to maintain a desired application flow rate, ensuring accurate chemical dosing based on actual flowing conditions, using a magnetic flow meter and processor to monitor and control the chemical flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a venturi with calibrated glass tube and V-notch is used to create vacuum and meter chemical flow, then the system can provide chemical feeding under vacuum conditions, but the metering accuracy deteriorates when chemical properties vary from calibration conditions
Solution Approach 1:
The patent implements a feedback control system where a flow rate sensor continuously monitors the actual chemical flow rate and sends signals to a controller. The controller compares the measured flow rate with the target flow rate and automatically adjusts the metering device (such as a variable geometry metering orifice or peristaltic pump) to maintain accurate dosing despite variations in chemical properties, specific gravity, or temperature. This closed-loop feedback eliminates the need for manual calibration adjustments and ensures consistent metering accuracy across different operating conditions.
2Ease of operation
If a V-notch device is used for metering, then the system can control chemical flow rate, but gas breakout or trapped gas prevents proper operation
Solution Approach 1:
The patent extracts and removes the problematic V-notch geometry that traps gas, replacing it with a streamlined metering device design that allows gas to pass through freely. The metering device uses a variable geometry orifice or peristaltic pumping mechanism that does not create dead zones where gas can become trapped. Gas breakout is accommodated by designing the flow path to allow gas-liquid separation and continuous operation even when gas is present in the chemical stream.
Solution Approach 2:
The patent employs dynamic metering devices such as variable geometry orifices or peristaltic pumps that can adapt their geometry in real-time based on flow conditions. These dynamic devices can adjust their opening size or compression ratio to compensate for gas breakout, ensuring continuous and reliable metering operation without the static limitations of fixed V-notch designs.
3Reliability
If vacuum metering systems are used, then chemical flow can be controlled under vacuum, but differential suction head changes cause chemical flow rate variations
Solution Approach 1:
The patent uses a flow rate sensor to continuously monitor the actual chemical flow rate and feeds this information back to the controller. The controller automatically adjusts the metering device to compensate for changes in differential suction head caused by varying chemical levels in the storage tank. This feedback mechanism maintains consistent flow rate despite changes in vacuum pressure or chemical density.
Solution Approach 2:
The patent dynamically changes the geometric parameters of the metering device (such as orifice diameter, angle, or pump compression ratio) in response to detected flow rate deviations. By continuously adjusting these parameters, the system compensates for variations in differential suction head and maintains stable chemical flow rate throughout the operating range.
4Ease of operation
If glass tube and V-notch devices are used for metering, then chemical flow can be indicated visually, but failures go unnoticed until visual inspection or downstream issues are detected
Solution Approach 1:
The patent implements electronic feedback through flow rate sensors that continuously monitor chemical flow and provide real-time data to the controller and display. This electronic monitoring system detects failures or deviations from normal operation immediately, providing early warning before downstream issues occur. The system can detect blocked flow, gas breakout, or improper dosing and alert the operator before these conditions cause problems in the fluid treatment system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides precise control over chemical dosing, addressing inaccuracies and operational issues by continuously monitoring and adjusting the flow rate, ensuring reliable operation even with varying chemical properties and conditions.
Implementation Method 1
using a magnetic flow meter and microprocessor-controlled motor to manage the chemical flow
Implementation Method 2
Commonly, these prior art systems utilize a venturi to create a vacuum. The vacuum draws a neat chemical through a calibrated glass tube and V-notch.
Data Source
AI summary
A chemical feeder system includes an aqueous chemical contained in a chemical source, the chemical source connected with a fluid stock through a chemical flow conduit and a feeder assembly connected within the chemical flow conduit that includes a metering device, a flow rate sensor and a controller operationally connected between the flow rate sensor and the metering device. A method of controlling the flow rate a treating chemical is applied to a fluid stock includes the steps of positioning a flow sensor upstream of a chemical metering device in a chemical flow conduit between a chemical source and fluid stock, flowing a treating chemical from the source through the chemical flow conduit, determining a desired application flow rate of the treating chemical and adjusting the metering device in response to a flow rate reading at the flow rate sensor to achieve the desired application flow rate.