Application of frequency converter in sewage treatment
1、 Overview
Water resource is an important factor of economic development and social sustainable development. Urban sewage treatment rate has become an important symbol of regional civilization. Sewage treatment has developed from the original natural treatment, simple primary treatment to the use of various advanced technologies, advanced treatment of sewage and reuse. The treatment process has also developed from traditional activated sludge process and oxidation ditch process to various processes to meet different effluent requirements.
2、 Sewage treatment process
The general sewage treatment mainly adopts two-stage treatment: the first stage is mechanical treatment, which generally uses the grille and other mechanical equipment to filter the floating objects or larger particles in the sewage; the second stage is biochemical treatment. According to different treatment requirements, the sewage contains a variety of silicon substances or metal elements exceeding the standard, so that the treated water can meet the requirements of subsequent water equipment, such as raw water Use purified water, industrial boiler softening and desalting water.
3、 Site conditions
The sewage in the sewage collection tank is sent to the sedimentation tank by two sewage pumps 1 and 2. In order to prevent the water overflow accident of the sedimentation tank, the water level detection device is set in the sedimentation tank. When the actual water level exceeds the alarm level, the control system automatically closes the electric butterfly valve in front of the grid to prevent the overflow accident. The sewage in the sedimentation tank is then sent to the biochemical treatment tank by the biochemical pump. The biochemical treatment tank is also equipped with a water level upper limit detection. The water level of the biochemical treatment tank is controlled by controlling the biochemical water pump.
4、 Transformation plan
1. The two water pumps in the sedimentation tank are controlled by one inverter with one driving two;
2. PLC + inverter with high reliability is adopted;
The sedimentation tank is equipped with upper and lower limit water level and upper and lower limit alarm water level detection. The control process is that when the water level reaches the lower limit, the water level detection will send the signal to the PLC, and the PLC will start the frequency converter and output the frequency rise signal to the frequency converter. When the frequency of the frequency converter reaches 50 Hz, if the water level is still at the lower limit position, the PLC will send a switching signal to switch the sewage pump 1 to the power frequency operation, and the frequency converter will start the sewage pump 2 after a period of delay. On the contrary, when the water level reaches the upper limit, the sewage pump 1 will be stopped, and the PLC will send the frequency drop signal of the frequency converter. If the water level is lower than the lower limit or the upper limit due to the water pump or other reasons, the water level detector will send the alarm signal to the PLC, and the PLC will output the alarm circuit (alarm indicator and Bell) to prompt the operator to check the reasons.
Aerator and submersible pump are the core equipment of sewage treatment. Frequency converter is used to control the speed of blower (roots blower) and submersible pump, Frequency conversion control of blower: the concentration of dissolved oxygen in aerobic part of sewage treatment has a great influence on the treatment result. If the concentration of dissolved oxygen is too low, the sewage can not meet the standard; if the dissolved concentration is too high, it will not only waste electric energy, but also make the activated sludge float up and make the effluent water not up to the standard. The purpose of adding frequency converter to the blower is to control the concentration of dissolved oxygen in CASS tank to be stable at a constant value.
5、 Conclusion
After the frequency conversion transformation, the sewage treatment plant not only improves the degree of automation and control accuracy, but also benefits greatly in energy saving and consumption reduction. The comprehensive power saving rate reaches 35%, and the enterprise and social benefits are greatly improved
Water resource is an important factor of economic development and social sustainable development. Urban sewage treatment rate has become an important symbol of regional civilization. Sewage treatment has developed from the original natural treatment, simple primary treatment to the use of various advanced technologies, advanced treatment of sewage and reuse. The treatment process has also developed from traditional activated sludge process and oxidation ditch process to various processes to meet different effluent requirements.
2、 Sewage treatment process
The general sewage treatment mainly adopts two-stage treatment: the first stage is mechanical treatment, which generally uses the grille and other mechanical equipment to filter the floating objects or larger particles in the sewage; the second stage is biochemical treatment. According to different treatment requirements, the sewage contains a variety of silicon substances or metal elements exceeding the standard, so that the treated water can meet the requirements of subsequent water equipment, such as raw water Use purified water, industrial boiler softening and desalting water.
3、 Site conditions
The sewage in the sewage collection tank is sent to the sedimentation tank by two sewage pumps 1 and 2. In order to prevent the water overflow accident of the sedimentation tank, the water level detection device is set in the sedimentation tank. When the actual water level exceeds the alarm level, the control system automatically closes the electric butterfly valve in front of the grid to prevent the overflow accident. The sewage in the sedimentation tank is then sent to the biochemical treatment tank by the biochemical pump. The biochemical treatment tank is also equipped with a water level upper limit detection. The water level of the biochemical treatment tank is controlled by controlling the biochemical water pump.
4、 Transformation plan
1. The two water pumps in the sedimentation tank are controlled by one inverter with one driving two;
2. PLC + inverter with high reliability is adopted;
The sedimentation tank is equipped with upper and lower limit water level and upper and lower limit alarm water level detection. The control process is that when the water level reaches the lower limit, the water level detection will send the signal to the PLC, and the PLC will start the frequency converter and output the frequency rise signal to the frequency converter. When the frequency of the frequency converter reaches 50 Hz, if the water level is still at the lower limit position, the PLC will send a switching signal to switch the sewage pump 1 to the power frequency operation, and the frequency converter will start the sewage pump 2 after a period of delay. On the contrary, when the water level reaches the upper limit, the sewage pump 1 will be stopped, and the PLC will send the frequency drop signal of the frequency converter. If the water level is lower than the lower limit or the upper limit due to the water pump or other reasons, the water level detector will send the alarm signal to the PLC, and the PLC will output the alarm circuit (alarm indicator and Bell) to prompt the operator to check the reasons.
Aerator and submersible pump are the core equipment of sewage treatment. Frequency converter is used to control the speed of blower (roots blower) and submersible pump, Frequency conversion control of blower: the concentration of dissolved oxygen in aerobic part of sewage treatment has a great influence on the treatment result. If the concentration of dissolved oxygen is too low, the sewage can not meet the standard; if the dissolved concentration is too high, it will not only waste electric energy, but also make the activated sludge float up and make the effluent water not up to the standard. The purpose of adding frequency converter to the blower is to control the concentration of dissolved oxygen in CASS tank to be stable at a constant value.
5、 Conclusion
After the frequency conversion transformation, the sewage treatment plant not only improves the degree of automation and control accuracy, but also benefits greatly in energy saving and consumption reduction. The comprehensive power saving rate reaches 35%, and the enterprise and social benefits are greatly improved
