The Prospect of Automatic Detection Instruments in Sewage Treatment

The automatic detection instrument is one of the most critical subsystems in the control system. The general automatic detection instrument is mainly composed of three parts: a sensor, a device that converts a non-electrical signal into an electrical signal, and a transmitter that converts an electrical signal converted by the sensor into an easily-processable 4-20 mA current signal or 0- The 5V voltage signal is sent to the programmable controller for analysis and calculation and processing. The display shows the measurement result visually. These three parts are organically combined and lacking any part of them cannot be called a complete instrument.

The automatic detection instrument has been widely used in industrial production because of its precise measurement, clear display, and simple operation. Furthermore, the automatic detection instrument has an interface with a microcomputer and is an important part of the automatic control system. "The eyes of an automated control system." With the development of science and technology, automated detection technology has also been greatly developed. Automated detection instruments have also been widely used in sewage treatment, making sewage treatment plants not only save a lot of manpower and material resources, but more importantly, can be timely. Adjust the wastewater treatment process. This article will take the wastewater treatment of the chemical production plant of Hongfa Coking Plant in Jiangsu Shagang Group as an example to introduce the application of automatic detection instruments in the sewage treatment system.

Sewage treatment process

The wastewater treatment section of the chemical production plant of the Hongfa coking plant of Jiangsu Shagang Group mainly accepts ammonia-steamed waste water and gas water seal water from other sections. First, the wastewater is pretreated, the wastewater enters the deoiling tank, and the oil impurities in the sewage are initially removed under the action of the two batch oil installation machines; the surface sludge is removed by the two sludge scrapers of the air floatation device. Smaller floaters removed; followed by biochemical treatment. A series of chemical reactions are mainly carried out through anaerobic, anoxic and aerobic ponds. After simple pretreatment, the denitrification reaction, carbonization reaction and nitrification reaction are performed in the anaerobic tank, anoxic tank and aerobic tank to reduce the contents of cod and ammonia bile and dissolved oxygen in the sewage; The suspended impurities in the precipitated sewage are finally purified and filtered, and the treated water is discharged after the index reaches the standard. The treated sludge can be used as a renewable resource after being pressed by a belt filter press. The process flow is shown in the figure.

Sewage treatment instrument

Ultrasonic level gauge

One ultrasonic level gauge was installed on each of the water lifting wells and the anaerobic water supply wells, and the level of the gas sealing water coming from other sections was reflected by the difference in level between the front and the back of the wells, and the situation of the wastewater in the anaerobic tank was eliminated. And transmitted to plc controller for analysis and calculation. When the liquid level exceeds the set value, the pump of the automatic control well can be automatically started and stopped when the on-site pump's operation column switch is turned on in the automatic position. This can accurately and timely adjust the operating status of the pump according to the amount of foreign water and reduce equipment fatigue; at the same time, it can eliminate the three-shift manpower cost of the traditional pumping station.

Flowmeters and Transmitters

Real-time monitoring of flow and throughput. For the management of the operation of the sewage treatment section, the amount of water is an important control parameter. Accurately and promptly grasping the influent water volume plays an important role in controlling the process and improving the ability of the wastewater section to withstand the impact of hydraulic loading. The traditional water measurement uses a seesaw or Venturi flow cell, which has the disadvantage of being unable to monitor in real time and display in real time. Jiangsu Shagang Group Co., Ltd. Hongfa Coking Plant Wastewater Treatment In the return sludge pipe and surplus sludge pipe and anaerobic tank, 5 sets of imported electromagnetic flowmeter with measuring range 0~1200m3/h were used to measure return sludge and remaining The flow of sludge. Electromagnetic flowmeter not only can display the flow of water in the field, but also through the transmission of plc in the upper computer real-time display of flow and total processing capacity, to achieve accurate measurement of water treatment, and provide real-time traffic management purposes. After the electromagnetic flowmeter is installed, the on-duty personnel can determine whether the return sludge pump and the excess sludge pump work properly according to whether the displayed flow is correct, and solve the problem that the submersible pump cannot simply determine whether the work is normal, and the electromagnetic flowmeter also has Easy installation and simple maintenance. Wastewater Phenol-Cyanide Blower When we blow to the aerobic tank, we directly install 4 gas flowmeters with measuring range of 0～4000m3/h on the air pipe between the two, and then pass the 4-20ma signal of the eja transmitter. Conversion to obtain the amount of wind in the pipeline, and through the plc system real-time display and monitoring in the host computer.

Dissolved oxygen meter and ph meter

The workshop process section uses the traditional activated sludge process. Biological treatment of aerobic tanks is undoubtedly the most important part of sewage treatment. Through biological treatment in aerobic tanks, various organic pollution components in the sewage can be effectively removed. The phenol-cyanogen blower used for oxygenating the aerobic tank is the main equipment for the power consumption of the sewage treatment section. The consumed electrical energy accounts for approximately the entire amount of power consumed in the entire section, in order to reduce the power caused by excessive unnecessary oxygenation. waste. A dissolved oxygen meter with a measuring range of 0.05 to 10 mg/l was installed in the biochemical treatment area of ​​the sewage treatment section. The dissolved oxygen concentration was detected on-line in real time. The detected concentration was converted into a standard current signal and transmitted to the plc in a timely manner. machine. When the detected concentration is less than or greater than the specified range, plc immediately issued a control instruction to regulate the outlet valve of the phenol-cyanogen blower of the sewage, thereby ensuring good biochemical ability of the aerobic tank bacteria, enhancing the decomposition ability of the aerobic flora, and reducing the sewage Processing section of the power consumption. In order to have a good effect on the treatment of sewage, we must effectively control the acid-base concentration of the incoming water in the biochemical pool. The general requirements for acid and alkali concentration are controlled between 7-8. In order to reduce the labor intensity of the operator, a pH meter on-line detection device is installed in the biochemical treatment area to measure the acid-base concentration of the influent water in the biochemical pool in real time. And through the organic combination with the plc control system, the on-site detected data is transmitted to the plc and the host computer. The acidity and alkalinity of the water in the influent and biochemical pool can be observed at any time directly on the computer screen, which is convenient for its timely Make adjustments.

Sludge concentration meter

Sludge concentration control in the sludge thickening tank. Sludge concentration in the sludge thickening tank is an important process parameter in the sewage treatment process. In the traditional sewage treatment plant, the concentration of sludge depends on the laboratory's use of the old test method for monitoring. There is a great deal of deficiencies in the timeliness and accuracy of data provision, and it is difficult to timely perform the return sludge and the amount of excess sludge. Process adjustments cause errors in time and accuracy. The wastewater treatment section of the Jiangsu Shagang Group Hongfa Coking Plant chemical plant has installed an on-line sludge concentration meter with a measurement range of 0.5 to 10 g/l on each sludge concentration tank and converted the detected concentration signal to 4 -20ma standard electric signal and timely transmission to the plc and the host computer and the system set the parameters compared, according to the results of the comparison to make the appropriate control, a good solution to this problem. The installation of the sludge concentration meter can timely adjust the sludge thickening tank process according to the accurately measured sludge concentration, and at the same time reduce the labor intensity of the laboratory staff.

Sewage Plant Instrument Management

Jiangsu Shagang Group Co., Ltd. Hongfa Coking Plant Wastewater Treatment Plant has been in operation since October 2003. During more than two years of operation and management, we have summarized several experiences in ensuring the normal operation of automated inspection instruments.

Probe cleaning

Maintain the cleanliness of the sensors in the automated tester. Regularly clean the probes to ensure the accuracy of data collection. Because the instrument works in the sewage environment, the cleaning of the instrument is particularly important, especially the analysis instruments such as the dissolved oxygen meter, the redox potentiometer and the sludge concentration meter directly contacting with the sewage. In order to ensure the normal operation of the instrument, we Regularly arrange the special person to clean the instrument probe and clean the instrument once every 7 days. When cleaning, use soft materials to avoid damage to the instrument.

Instrument calibration

Calibrate various instruments regularly. In the long-term operation of the instrument will inevitably produce measurement error, which requires regular calibration of the instrument to ensure the accuracy of the instrument measurement, the analysis instrument we have established a regular correction every two months; and requires the laboratory to work The personnel use the analysis method to analyze the corresponding test items, and compare it with the on-site instrument monitoring results. If the deviation is too large, the instrument should be corrected in time to ensure the accuracy of the test data.

Power protection

Ensure the stability of the instrument power supply voltage and extend the life of the instrument. Instant high-voltage shocks often make the meter burn out easily. During the operation of the sewage treatment plant in the chemical plant of Hongfa coking plant of Jiangsu Shagang Group Co., Ltd., due to the instability of the power supply voltage, the transmitters of the ultrasonic liquid level gauge and the ultrasonic level gauge were damaged, which affected the automatic control system. The normal working situation. Jiangsu Shagang Group Co., Ltd. Hongfa Coking Plant Wastewater treatment plant is undergoing technical transformation to avoid damage to the instrument caused by unstable power supply voltage, reduce operating costs, and increase economic efficiency.

Conclusion

Automated detection instruments greatly reduce labor intensity while increasing productivity in the application of sewage treatment sections. It is believed that with the continuous development of science and technology, automated measuring instruments in the future will play a greater role in sewage treatment and other environmental protection work.