COD (chemical oxygen demand) online monitoring instrument

Abstract

The invention relates to a COD (chemical oxygen demand) online monitoring instrument. The COD online monitoring instrument comprises a control pipeline of a PLC (programmable logic controller) control system, a sample and reagent storage device and a reaction device which are controlled to be communicated, and a photoelectric metering tube, wherein a piston pump for sample injection is arranged on the outer side of the pipeline, the sample and reagent storage device comprises a water sample bottle, a zero-point standard solution bottle, a COD standard solution bottle, a masking agent solution bottle, an oxidant solution bottle and a catalyst solution bottle which are selected by a multi-way valve to open and close, and the multi-way valve can selectively open and close a water sample or reagent pipeline for controlling sample injection. The reaction device comprises heating wires, a digestion colorimetric tube, a fan, a colorimetric light source and an upper electromagnetic valve, wherein the photoelectric metering tube is linked with the control pipeline, an upper light source and a photoelectric detector thereof as well as a lower light source and a photoelectric detector thereof are arranged outside the photoelectric metering tube, and the photoelectric metering tube is connected with the PLC control system through a photoelectric conversion circuit. The COD online monitoring instrument disclosed by the invention adopts a PLC control technology to realize optical-mechanical-electrical integration, can realize complete and through automation, and has the advantages of low failure rate, low maintenance quantity, low reagent consumption and higher performance-price ratio.

Description

technical field [0001] The invention relates to a water quality automatic monitoring device, in particular to an online COD monitor. technical background [0002] The COD online monitoring instrument can heat the mixture of water samples, potassium dichromate digestion solution, silver sulfate solution (silver sulfate can be added as a catalyst to more effectively oxidize straight-chain fatty compounds), and concentrated sulfuric acid to 175°C. The color will change after the ion oxidizes the organic matter in the solution, and the analyzer detects the color change, and converts this change into a COD value and outputs it. The amount of dichromate ions consumed is equivalent to the amount of oxidizable organic matter. [0003] Most of the existing COD on-line monitoring instruments require manual intervention to prepare and prepare reagents, and in the prior art, solenoid valves are used to control the delivery of reagents and samples for reaction. Although the diaphragm s...

AI Technical Summary

Problems solved by technology

Although the diaphragm solenoid valve has high anti-corrosion performance, it has high requirements on the cleanliness of the reagent. When the reagent is dirty, backflow often occurs, and this type of solenoid valve has a pump that sucks or discharges the fluid as it opens and closes. function, so higher requirements are put forward for the accuracy of analysis and sampling, especially when the dose taken is very small, the error is more serious, and more serious is the need for frequent maintenance, resulting in the existing The accuracy of instrument monitoring in technology is relatively low

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