A digital variable frequency metering controller for flow of strong corrosive liquid medium

Abstract

The invention discloses a digital frequency conversion metering controller of a highly corrosive liquid medium. The function of an anti-corrosion flow meter, the function of a frequency converter andthe function of a PLC are integrated, local autonomous measurement and control can be carried out on the highly corrosive liquid medium, remote control instructions can also be received through a network interface, and remote control based on optimization is implemented. A PI adjustment and fuzzy logic adjustment algorithm is embedded in the controller, the analog quantity input function is achieved, closed-loop control can be carried out according to signals fed back by a detection instrument, for example, the pH value can be adjusted according to a pH value detection signal. Of course, othercomponents can be automatically adjusted by utilizing other component detectors.

Description

technical field [0001] The invention relates to the detection and control technology of the flow rate of strong corrosive liquid medium, especially the highly integrated functions of PLC controller, anti-corrosion flow meter and frequency converter to form a digital frequency conversion metering controller capable of detecting flow rate and controlling flow rate at the same time. Background technique [0002] The liquid medium dosing device takes industrial metering pumps as the core, and is widely used in petroleum, chemical, water treatment, thermal power generation, pharmaceutical, food, papermaking and other process industries. It is a key production process link to add various chemicals in precise proportions to ensure product quality. Most of the liquids conveyed and fed in the process industry are corrosive media such as strong acids and alkalis, and are usually transported and fed by diaphragm metering pumps with anti-corrosion functions. Such as figure 1 As shown,...

AI Technical Summary

Problems solved by technology

The main problems existing in the existing diaphragm metering pumps are as follows: firstly, the flow rate can be roughly adjusted offline through the handwheel, which cannot realize accurate online adjustment and real flow metering, which is not conducive to energy saving and consumption reduction, and it is difficult to ensure product quality; The second is that there are strong acids, strong alkalis and toxic gases on the job site, and the environment is harsh, which is inconvenient for manual operation.

The disadvantages are: (1) the transmission mechanism is complicated, the reliability is poor, the volume is large, the installation is inconvenient, and the cost is high; (2) for a pump with a large flow rate, if the stroke is adjusted small, for example, when it is close to zero, the flow rate is also close to zero, but the driving motor is still running at the rated speed, which is similar to doing useless work, which is not conducive to energy saving; (3) Although the electric stroke regulator can estimate the flow rate under the condition of constant speed, but the flow rate accuracy is high and the speed If it is not constant, in order to improve the accuracy of flow detection, it is necessary to configure an anti-corrosion flowmeter, which will further increase the cost; (4) its adjustment accuracy depends on the constant speed, and the metering pump usually uses a three-phase asynchronous motor in order to reduce the cost Drive, when the load is not stable, the speed of the three-phase asynchronous motor cannot be constant, so the adjustment accuracy is difficult to guarantee; (5) In order to ensure the adjustment accuracy, the adjustment speed of the stroke regulator is very slow, so the dynamic response performance is poor

[0006] In terms of frequency automatic adjustment, the combination of general frequency converter, PLC and anti-corrosion flowmeter is used, as shown in Figure 3. Although it can form a closed-loop adjustment, it is not restricted by patent protection, but the main problem is that it is expensive and difficult to promote in large quantities. It can only be used in some occasions with high requirements. Secondly, the general-purpose inverter adopts vector control to maintain a constant speed with large electromagnetic torque changes. For the impact load borne by the metering pump, the electric impact is large, which affects the three-phase asynchronous The insulation and service life of the motor, and the energy saving effect is also poor

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