SU858883A1 - Method of automatic control of ionite exchanger desorption process - Google Patents

Description

I

The invention relates to methods for automatically controlling the desorption processes of ion-exchange filters for chemical purification of natural and waste waters and can be used in non-ferrous metallurgy and power engineering.

There is a known method for determining the end point of the regeneration and washing operations using laboratory chemical analyzes performed manually.

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In automating the desorption processes, these operations are performed according to a time program, and the time is determined from the worst conditions. However, the time estimate, as shown by operating experience, in spite of fairly tight tolerances, is not optimal. The time of the operation, from the point of view of the quality of the operation, must be variable, otherwise it will lead to unnecessary waste of washing water and reagents, or to

deterioration in the quality of the operation.

There is a known method for automatically controlling the desorption process, in which the moment of the end of the washing operation is determined by the difference in electrical conductivity of the source and wash water 2.

However, with this method, the electrical conductivity of the source water at various stages of washing influences the change in the conductivity of the wash water, and also requires the introduction of temperature compensation and, due to the large

15 the effect of temperature on the electrical conductivity of the wash water (even with clean water and a temperature change of 20 ° C, the electrical conductivity changes 3.5 times) 5 however it is difficult

Claims (3)

20 to realize due to the large signal lag in the conductivity of the wash water (20-25 min) and the different dependencies of the conductivity of the wash water at different stages of washing and initial water: F1 at different pH The closest to the proposed invention in technical essence and the achieved result is A method for automatically controlling the process of desorption of ion exchange filters by adjusting the duration of the regeneration and washing operations and measuring the electrical conductivity of the medium at the exit of the ion exchange filter. The end of the washing with this method is carried out according to the rate of change of the electrical conductivity of the wash water at the outlet of the ion exchange filter 3 1. However, this method is approximate; as a result, there is an excess consumption of water and reagents. The purpose of the invention is to reduce the consumption of water and reagents by improving control accuracy. This goal is achieved by determining the time of completion of the regeneration and washing operations to accelerate the change in the electrical conductivity of the medium at the output of the ion exchange filter, taking into account the sign of the rate of change of this electrical conductivity. FIG. Figure 1 shows the dependence of the change in the electrical conductivity of the medium (x) on the time (t) at the outlet of the filter (section 1 — regeneration operation, section 2 — washing operation); in fig. 2 - additional curves of the first derivative of the change in conductivity (the rate of change of conductivity) and the second derivative of the change in conductivity (acceleration of change in conductivity); in fig. 3 is a basic scheme of a system implementing the proposed automatic control method. The method is carried out as follows. The rate of change of electrical conductivity dKJd: t3a operation time varies from 0 to a maximum and then returns to a zero value of FIG. 2, i.e., it has one extremum (for regeneration - for washing - maximum). During the same operation, the acceleration of the change in electrical conductivity (3 X / cit (° P derivative of the change in electrical conductivity over time) has two extremes: one minimum and a second maximum. The curve of change in the electrical conductivity of the medium has a very prolonged character at the end of the process. The speed curve has It is also a very lengthy character. At a definite moment of the end of the operation, this leads to an inadvertent fy consumption of reactants and washing or dilution water. From the acceleration curve} 1 or 1 of the change in conductivity I of Fig. 2, it can be seen that t be completed when the extremum of the corresponding Zachak is reached (for the regeneration operation - the maximum, for the washing operation - the minimum). To determine the desired type of extremum for each operation (minimum or maximum), the following characteristic pattern can be used; the first signs (speed and second ( the acceleration of derivatives of a change in electrical conductivity at the time points of the end of operations is opposite. Therefore, it is possible to determine the moment of the end of an operation after the acceleration changes extremum at corresponding speed mark (opposite signs), i.e. using the sign of speed (first derivative) as a means of controlling the achievement of the required extremum corresponding to the moment of the end of the operation. On the signal of the end of the operation, checking the reliability of this signal by the sign of the first derivative (speed) of the conductivity change, the valves are closed at the inlet and outlet of the reagents and water. At the outlet of the ion exchange filter 1, the conductometric sensors 2 and 3 are installed, measuring the conductivity of the wash water (Fig. 3). The conductometric sensors 2 and 3 are located at a distance that is chosen in such a way that the medium transport time is 10-20 seconds, thereby choosing a time interval for differentiation. The signals of conductometric sensors 2 and 3 with different signs are fed to an algebraic summing device 4, which calculates the first derivative of the change in electrical conductivity. A speed signal of varying electrical conductivity is applied to differentiation device 5 and reliability control device 6. After the trimming device, the signal is fed to the comparison node 7 through the signal reliability monitoring device 6, which is an electronic key controlled by an appropriate sign of the signal of the change rate of the electrical conductivity of the medium. At the comparison node 7, a reference signal from the command device 8 and a signal from the differentiation device 5 are compared. The difference of these signals controls the regulating device 9. From the output of the regulating device 9, the control signal passes to the actuating mechanisms of the control valve 10 and 11 l of the operating valve supplying the washing of cold water and bottom drainage, the regeneration operation is the valve on the reagent supply line, diluted water and drainage). Opening the valve at the beginning of the operation can be done either by the operator or automatically at the end of the previous operation signal. After opening the valve, the command device 8 is automatically put into operation. The command device continues to give a control signal to open the valve. The need for different signs of speed and acceleration is used to control the accuracy of the change in the electrical conductivity of the signal of the end of the operation. After the signal about the end of the operation at the output of the signal control device 6, the regulating device 9 issues a control command 34 to close the corresponding valve and 10 and 1 1. The second derivative significantly reduces the operation time: the washing operation is reduced by 25-30 %, regeneration operation by 15-20%. The combined use of the first and second derivatives increases the noise immunity of the signal at the end of the operation. The method of automatic control of the desorption process of ion-exchange filters by adjusting the duration of the regeneration and washing operations and measuring the conductivity of the medium at the output of the ion-exchange filter, so that, in order to reduce water consumption and rvag; enta due to control accuracy, the moment of completion of the regeneration and washing operations to accelerate the change in the electrical conductivity of the medium at the output of the ion exchange filter, taking into account the sign of the rate of change of this electro conduction. Sources of information taken into account in the examination 1.L.M.Zhivilova and others. Automation of water-conditioning computational installations of thermal power plants. M., Energie, 1976, p. 49-50. 2. USSR author's certificate number 399460, cl. C 02 B 1/18, 1976. 3. USSR author's certificate number 724171, CP ,. B 01 D 37/04, 1978.