RU2744346C1 - Method for monitoring the operation of the na-cationization plant - Google Patents

Abstract

FIELD: water softening.

SUBSTANCE: invention relates to a method for monitoring the operation of an installation for Na-cationization of water. The method consists in the fact that the initial hard water is supplied to the Na-cationization unit, while the hardness of the softened water obtained at the outlet is maintained within 0.02-0.2 mg-eq / l, the quality of the operation of the Na-cationization unit is monitored continuously by two measured parameters, which are used as the specific electrical conductivity (SEC) of the source water and the SEC of softened water, and one calculated parameter, which is used as the difference between the SEC of softened and source water, and during operation, the value of the SEC of softened water is constantly measured using a conductivity sensor with a transmitter and the measured values of the SEC are transmitted using a programmable logic controller (PLC) to a remote server for subsequent control, while the transmitter converts the measured value of the SEC into a 4-20 mA current signal, which is fed to the PLC, then at least one once a day, the value of the SEC of the source water is measured about with the same conductivity sensor, controlling the direction of the water flow using solenoid valves, while the value of the SEC of the source water is also transmitted to the remote server, then the difference between the values of the SEC of softened and source water is constantly determined, while the constancy of the values of the SEC of softened water and constancy the difference between the SEC of softened water and the source water will make it possible to judge the quality of the operation of the Na-cationization unit.

EFFECT: increased efficiency of quality control of the process of Na-cationization of water by continuously monitoring the value of the SEC of the initial and softened water, as well as the difference between the SEC of the softened and original water.

1 cl, 1 tbl, 1 ex, 3 dwg

Description

Technology area

The invention relates to the field of water treatment and concerns issues of monitoring the operation of Na-cation exchange water softening systems by continuously measuring the specific electrical conductivity (EEC) of the source and softened water and monitoring the difference in their values.

Prior art

A known method of operating a water treatment plant with a softening device including an ion-exchange resin, a conductivity sensor, an electronic control device and an automatically adjustable dilution device for mixing a mixed water flow V (t) verschnitt from the first softened partial flow V (t) teil1weich, and the second derived from the raw water of the partial flow V (t) teil2roh, and experimentally determine the conductivity LFweich of softened water or the conductivity LFverschnitt of mixed water, while from the experimentally determined conductivity LFweich of softened water or LFverschnitt of mixed water, the conductivity LFroh of raw water and / or the total hardness of raw water, and when deriving the conductivity LFroh of the raw water and / or the total hardness of the raw water from the experimentally determined conductivity LFweich of softened water or LFverschnitt of mixed water, a correction is made for the ra the excellent conductivity of a calcium or magnesium ion on the one hand and two sodium ions on the other, and that the derived conductivity LFroh of the raw water and / or the total hardness of the raw water is used to adjust the flow hardness V (t) verschnitt of the mixed water by appropriate adjustment of the mixing ratio of both partial flows V (t) teil1weich and V (t) teil2roh to a predetermined value (SW) (see. RF patent for invention No. 2569094, IPC C02F05 / 00; C02F01 / 42, B01J47 / 14; C02F103 / 04, publ. November 20, 2015).

The disadvantage of this method is to measure only the UEP of softened or mixed water. As a result, in fact, control of the operation of the softener is not performed. It is assumed that water softening is carried out completely and a decrease or increase in the UEP of softened water is used to calculate the UEP and, accordingly, the hardness of the source water in order to correct the filter cycle.

исходной воды, моментальной жесткости

смешанной воды, расходов моментальных частичных потоков

и

, моментального общего потока

исходной воды, моментального потока

смешанной воды, для подстройки положения регулирования смесительного устройства, и вместо этого исходит из последней значащей соответствующей измерительной величины при последней подстройке перед возникновением заданной рабочей ситуации или хранящегося в памяти электронного управляющего устройства стандартного значения для соответствующей измерительной величины (см. патент РФ на изобретение №2516159, МПК C02F01/42, C02F05/00, G05D 21/02, опубл. 20.05.2014 г.).There is a method of operation of a water softener containing an automatically adjustable mixing device for regulating mixing of the flow V (t) verschnitt of mixed water from the first softened partial flow V (t) teil1weicn and the second partial flow V (t) teil2roh containing raw water, and an electronic control device , the control device adjusts the control position of the mixing device with the help of one or several experimentally determined instantaneous measuring values so that the water hardness of the mixed flow V (t) verschnitt is set to a predetermined nominal value (SW), while the control device in one or more predetermined operating situations of the water softener related to the design and function of the operating water softener ignores at least one of one or more untrustworthy or insignificant changes from the last adjustment of the mixing valve control position o device of instantaneous measuring values selected from instantaneous stiffness

initial water, instant hardness

mixed water, flow rates of instant partial flows

and

, instant general flow

initial water, instant flow

mixed water, to fine-tune the control position of the mixing device, and instead proceeds from the last significant corresponding measurement value at the last adjustment before the specified operating situation or from the stored in the memory of the electronic control device standard value for the corresponding measurement value (see RF patent for invention No. 2516159 , IPC C02F01 / 42, C02F05 / 00, G05D 21/02, publ. 20.05.2014).

The disadvantage of this method is the measurement of the UEP of the source water and, based on the measured value, the determination of the hardness of the source water. Depending on the hardness of the source water, a filter cycle of the softening unit is installed. This makes sense only if the ionic composition of the initial water remains unchanged, which practically does not occur in real conditions. The actual control of the softening unit is not carried out, since the difference in UEP of the source and softened water is not measured, but calculated.

A known method of operation of a water softener with an ion-exchange device containing an ion-exchange resin, a supply tank for supplying a solution of a regenerating agent for regenerating an ion-exchange resin, a mixing device, and at least one flow meter, and the volume flow V (t) ref source water is divided into a first partial volumetric flow and a second partial volumetric flow in the water softener or before it, and the first partial volumetric flow is directed through the ion-exchange resin, and this softened partial volumetric flow V (t) part1 of the soft is mixed with the second partial volumetric flow flow V (t) part2rex, as a result of which an outgoing volumetric flow V (t) of mixed mixed water is formed in the water softener or after it, while using the mixing device, the ratio between the first and second partial volumetric flows in the outgoing volumetric flow V (t) mixed mixed water, pr and this method includes the following steps:

- determination of the conductivity of the source water by means of a conductivity sensor and, based on it, determination of the total hardness of the source water using the calibration characteristic stored in the electronic control unit,

- direct or indirect determination of the first partial volumetric flow V (t) part1 of the pulp using the said at least one flow meter, while the total hardness I of the source water, which is used to control the regeneration process of the ion exchange resin, is derived from the measured conductivity by means of the first calibration characteristic (F1 ),

moreover, the total hardness I corresponds at least to a good approximation to the maximum water hardness occurring at a given conductivity, and the total hardness II of the source water, which is used to control the mixing device, is derived from the measured conductivity by means of the second calibration characteristic (F2), and the total hardness II corresponds at least to a good approximation to the average water hardness occurring at a given conductivity, wherein the second calibration characteristic (F2) differs from the first calibration characteristic (F1), and the total hardness I derived from the first calibration characteristic (F1) is at least partly more than the total hardness II derived from the second calibration characteristic (F2) (see RF patent for invention No. 2478579, IPC C02F01 / 42, G05D21 / 02, B01J49 / 00, publ. 10.04.2013).

The disadvantage of this method is the measurement of the UEP of the source water and, based on the measured value, the determination of the hardness of the source water. Depending on the calculated hardness of the source water, a filter cycle of the softening unit is installed. Moreover, it is assumed that the hardness of water, determined using the calibration characteristic, has a maximum value for a given value of the SEC of the source water. This can lead to a significant waste of salt for regeneration of the softener and an increased amount of waste water.

The closest in technical essence to the proposed invention is a known method of operation of a water softener with an automatic dilution device, and the incoming raw water stream Vroh is divided into the first partial stream Vteil1, which is softened, and the second partial stream Vteil2, which is not softened, and both partial streams Vteil1 , Vteil2 are combined into a mixed water stream Vverschnitt, and the proportions Ateil1, Ateil2 of both partial streams in the mixed water stream Vverschnitt are so regulated by an automatic dilution device that a given hardness SW is obtained in the mixed water stream Vverschnitt, and the adjustable proportions Ateil1, Ateil2 of both partial streams are calculated from the hardness Hroh of the raw water and the hardness Hweich of the softened water, and the value of the hardness Hroh of the raw water is derived from the conductivity LFroh of the raw water, while the conductivity LFweich of the softened water is measured with a conductivity sensor in the softened first partial flow Vteil 1, and the conductivity LFverschnitt of mixed water is measured with a conductivity sensor in the mixed water flow Vverschnitt, and the fractions Ateil1, Ateil2 of partial flows in the mixed water flow Vverschnitt are determined, and the conductivity LFroh of raw water is calculated from the measured conductivity LFweich of softened water, measured conductivity LFverschnitt of mixed water and calculated shares Ateil1, Ateil2 partial flows (see. RF patent for invention No. 2643554, IPC C02F01 / 42, C02F05 / 00, publ. 02.02.2018 g.).

The disadvantage of the known method for monitoring the operation of the installation of Na-cation-exchange water softening is the production of measurement of UEP only softened water. SEC of source water is calculated based on a certain ratio. This circumstance does not allow to reliably control the operation of the softening plant, since the real difference between the value of the UEP of the initial and softened water is not clear.

In fact, the control of the operation of the softening plant is carried out only by the water meter. This control method does not imply control of water softening, but only control of the subsequent mixing of softened and non-softened water to obtain partially softened water. It is also a disadvantage that the control of softened and partially softened water is carried out by two conductivity sensors. The SEC value of softened water has an average value of only 2.5-5% more than the SEC value of the source water. At the same time, the error in measuring the UEP is on average 1.5-2%, which significantly complicates the ability to accurately control the operation of the water softening plant according to the proposed method.

Disclosure of invention

The objective of the present invention is to improve the control efficiency of the Na-cation exchange water softening process.

The technical result achieved when solving this problem is to increase the efficiency of the quality control of the process of Na-cationization of water by continuously monitoring the value of the AEC of the initial and softened water, as well as the difference between the AEC of the softened and initial water.

The specified technical result is achieved by the fact that the method for controlling the operation of the Na-cationization unit of water consists in the fact that the initial hard water is supplied to the Na-cationization unit, while the hardness obtained at the outlet of the softened water is maintained within the range of 0.02-0.2 mg-eq / l, monitoring of the quality of the operation of the Na-cationization unit of water is carried out continuously according to two measured parameters, which are used as the specific electrical conductivity (SEC) of the source water and the SEC of softened water, and one calculated parameter, which is used as the difference between the SEC softened and raw water, and in the process of operation, the SEC value of softened water is constantly measured using a conductivity sensor with a transmitter and the measured SEC values are transmitted using a programmable logic controller (PLC) to a remote server for subsequent control, while the transmitter converts the measured SEC value into current signal 4-20 mA, which enters the PLC, then at least once a day the value of the UEP of the source water is measured with the same conductivity sensor, controlling the direction of the water flow using solenoid valves, while the value of the UEP of the source water is also transmitted to the remote server, then the difference is constantly determined between the SEC values of softened and initial water, while the constancy of the SEC values of softened water and the constancy of the difference between the SEC values of the softened water and the source water will make it possible to judge the quality of the operation of the Na-cationization unit.

The hardness obtained at the outlet of softened water is maintained in the range of 0.02-0.2 mg-eq / l, since the value of this limit of the hardness of softened water is provided in the volume of the filter cycle of the Na-cationization unit and an increase in the hardness value is more than 0.2 mg- eq / l indicates the depletion of the cation exchanger of the Na - cationization unit,

Continuous measurement during operation of the SEC value of softened water using a conductivity sensor with a transmitter and transferring the measured SEC values to a remote server using a PLC, as well as measuring the SEC value of the source water with the same conductivity sensor and transmitting the measured values to a remote server, allows you to constantly determine the differences between the values of the UEP of the softened and source water. This makes it possible to control the quality of softened water by measuring the SEP values of softened water and source water with the subsequent determination of the difference between the ECE of softened water and source water and, accordingly, increase the efficiency of the quality control of the Na-cationization process of water.

Brief Description of Drawings

The essence of the invention is illustrated by drawings, which show: Fig. 1 - flow diagram of the control system for the installation of Na - water cationization; in fig. 2 -. a graph of the change in the values of the UEP of the initial and softened water versus the operating time of the Na unit - water cationization; in fig. 3 - the dependence of the hardness of softened water on the volume of water that has passed the installation of Na - water cationization.

The designations in the drawing (Fig. 1) show the following: Na-cat - water softener; EK1, EK2, EK3, EK4 - solenoid valves; PC - flow cell; DP - conductivity sensor; T - transmitter; PLC is a programmable logic controller.

Detailed description of the invention

Detailed description of the invention

The proposed method for monitoring the operation of the installation of Na-cationization of water is carried out as follows.

The source water containing increased hardness (calcium and magnesium ions) is sent to the unit for Na-cationization of water, in which the source water is filtered through a cation-exchange resin. As a result, calcium and magnesium ions contained in the original water are replaced by sodium ions. Thus, softened water practically does not contain calcium and magnesium ions and contains an equivalent amount of sodium ions. As a result, softened water has a SEC value different from the SEC value of the source water. This is due to the fact that hardness salts, with an increase in their concentration in water, have a lower value of the UEP than sodium salts at the same concentration. Thus, almost all surface and artesian waters after softening have a SEC value slightly higher than the SEC value of the initial water. The SEC value of softened water has an average value of only 2.5-5% more than the SEC value of the source water. In this case, the measurement of the SEC of the initial and softened water by two different sensors can give insufficiently accurate results, by which it will be difficult to judge the quality of the operation of the Na-cationization unit. The error in measuring the UEP value is on average about 2% of the measured value. To exclude the influence of the relative measurement error of the UEP of the source and softened water, it is proposed to use one electrical conductivity sensor. In this case, the measurement error will be the same for the initial and softened water and, accordingly, since the control of the operation of the water softening plant is carried out not according to the absolutely measured values of the SEC, but according to the difference of the SEC of the softened and the initial water, the influence of the relative error on the measurement of the difference value of the SEC will be excluded ...

The following scheme is proposed for measuring the SEC of the initial and softened water. Sample lines cut into the pipelines of the source and softened water. A solenoid valve (EK1, EK2, EK3, EK4) and a check valve are installed on each line. After the solenoid valves, the sampling lines of the initial and softened water are brought together into one line, which is connected to a flow cell (PC), into which a conductivity sensor (DP) is hermetically screwed. Water from the flow cell is either discharged into the drain or directed to a tank or softened water line.

The system works in the following way. The SEC of the softened water is constantly measured. To do this, at the command of the controller, the solenoid valves have the following configuration: EK1 and EK2 are open; EC3 and EC4 are closed. Thus, the softened water through the sampling line enters the flow cell, where its SEC is measured taking into account the water temperature. The measured value is transmitted via the transmitter (T) to the programmable logic controller (PLC). The conductivity value is transmitted from the controller to the remote server. Then, one or more times a day, the programmable logic controller switches the solenoid valves to the following configuration: EC1 and EC2 are closed; EC3 and EC4 are open. Thus, the source water enters the flow cell for measuring the SEC of the source water taking into account the water temperature. SEC of source water has a stable constant value for surface and groundwater. Change in SEC of source water for surface sources depends on the season. At the same time, the change is very slow. Therefore, for sources of source water, it is sufficient to measure the SEC value once a day. It can be assumed that during one day the SEC of the source water has a constant fixed value. If a mixture of water from different sources is used as the initial water for softening, then the measurement of the SEC of such initial water must be performed more often than once a day. Then the value of the difference between the UEP of softened water and source water is calculated according to the formula

– разница между УЭП умягченной и исходной воды;Where

- the difference between the UEP of softened and source water;

UEP _um - UEP of softened water, μS / cm;

UEP _out - UEP of source water, μS / cm.

, УЭП_ум и УЭП_исх постоянно фиксируют. Затем, основываясь на постоянстве значений

и УЭП_ум, делают вывод о качестве умягченной воды и, соответственно, о качестве работы установки Na-катионирования. Уменьшение

и УЭП_ум в процессе работы установки умягчения говорит о том, что в умягченной воде появляются соли жесткости и необходимо произвести регенерацию установки умягчения или выявить иные причины появления солей жесткости в умягченной воде.The values

, UEP _mind and UEP _{ref are} constantly fixed. Then, based on the constancy of the values

and UEP _um , conclude about the quality of softened water and, accordingly, about the quality of the Na-cationization unit. Decrease

and UEP _um during the operation of the softener indicates that hardness salts appear in the softened water and it is necessary to regenerate the softener or identify other reasons for the appearance of hardness salts in the softened water.

The invention is illustrated by the following example.

Example. Application of the control system for the installation of Na - water cationization according to the proposed method for fresh water from a drinking water supply. Water is prepared (softened) for technical use. The composition of the source water is presented in the table.

Table Indicator unit of measurement Value Total hardness meq / l 2.8 Total alkalinity meq / l 1.8 Chlorides mg / l 14 Sulfates mg / l 67 Sodium + potassium mg / l eighteen UEP μS / cm 354 Silicon (as H ₄ SiO ₄ ) mg / l absent Iron, dissolved mg / l 0.1 PH value Unit pH 6.8-7.2

The flow diagram of the system for monitoring the operation of the Na-cationization plant is shown in Fig. 1. Continuous measurement of the UEP of water is carried out using a conductivity sensor installed in the measuring cuvette. The measured value of the SEC is converted into a 4-20 mA current signal using a transmitter. The signal is transmitted to the PLC. The measured UEP values are transmitted by the PLC to a remote server for visual control. With the help of solenoid valves, the water flows are switched for sequential measurement of the UEP of the softened and initial water. To measure the UEP of softened water using a PLC automatically by timer, once a day, the following positions of the solenoid valves are set: EK1 and EK2 are open; EC3 and EC4 are closed. Every 23 hours, the UEP of the source water is measured for 1 hour. To do this, using the PLC, the following positions of the solenoid valves are automatically set: EK1 and EK2 are closed, and EK3 and EK4 are open. The valves are switched by a timer using a PLC. The obtained values of the SEC of the softened and source water are transmitted to a remote server for visual control.

The graph of the change in the values of the SEC of the initial and softened water from the time of operation of the softening unit is shown in Fig. 2 (the graph was experimentally obtained in the period from 03.03.2020 at 11:30:00 to 03.03.2020 at 21:50:59). From the graph in FIG. 2, it can be seen that the SEC of the initial water practically did not change during the entire observation period and was at the level of 354 μS / cm and corresponded to the value of the initial water hardness - 2.8 mg-eq / l. The SEC value of softened water practically did not change during operation in the volume of the filter cycle of the softening unit and was at the level of 372-373 μS / cm. This suggests that water softening was carried out constantly to a hardness level of no more than 0.1 mg-eq / l. From FIG. 2 it can also be seen that the difference between the AEC values of the softened and the initial water ΔUEP during the operation of the softening unit in the volume of the filter cycle was constant and amounted to 18 μS / cm. The constancy of the UEP values of softened water and the constancy of the difference between the UEP of softened water and the source water allows us to judge the quality of the operation of the Na-cationization unit and indicates that the installation softens water in the volume of the installed filter cycle. After the hardness of the softened water began to exceed 0.1 mg-eq / l, the value of ΔUEP also began to decrease. After the breakthrough of hardness salts into softened water, the value of ΔUEP began to fall and after 3.5 hours it reached the value 0. That is, the softening unit has exhausted its ion-exchange capacity, the hardness of the softened water has become equal to the hardness of the source water.

Tracking the values of SEC of softened water and ΔUEP during the operation of the softener, in this example, made it possible to clearly determine the moment of breakthrough of hardness into softened water without performing chemical analyzes.

Using the data obtained, it is possible to construct a dependence on which it will be clearly seen what volume of the exchange capacity of the cation exchanger is provided by the filter cycle, and what is the quality of the softened water obtained in the volume of this filter cycle. FIG. 3 shows the dependence of the hardness of softened water on the volume of water that has passed the softening installation. As seen in FIG. 3, the hardness of softened water no more than 0.1 mg-eq / l was provided in the volume of the filter cycle 180 l. At the same time, the hardness of softened water equal to 0.2 mg-eq / l was provided in a volume of 250 liters. Only after 300 l of water softened, the hardness of the filtrate was slightly more than 0.5 mg-eq / l. The recommended filter cycle for a given amount of cation exchanger was 240 liters. In this case, the water hardness was no more than 0.2 mg-eq / l.

As you can see, a sharp increase in the hardness of the filtrate occurs after the hardness of the filtrate is 0.5 mg-eq / l. Therefore, when the softening unit is operating as the first stage, it is recommended to put the unit into regeneration at a filtrate hardness of 0.5 mg-eq / l, and calculate the filter cycle for a filtrate hardness of 0.1 mg-eq / l.

Obviously, when using the proposed system for monitoring the operation of the softening plant, it is easy, without carrying out chemical analyzes, to determine the optimal filter cycle for the operation of the softening plant, thereby reducing the amount of wastewater and salt consumption, while ensuring a constant standard quality of softened water.

The present invention is not limited to the example described above, given only as an illustration of a specific embodiment.

The use of the proposed method for monitoring the installation of Na-cationization of water allows real-time and remote control over the operation of the installation due to the digitalization of key performance indicators of the installation, which makes it possible to quickly identify problems during the operation of the installation. Chemical analyzes are not required during the operation of the installation and the accuracy of the measured UEP indicators is significantly increased. It makes it relatively easy to determine the optimal filter cycle for the operation of the installation, which greatly simplifies and at the same time improves the quality of commissioning and operational commissioning, carried out at start-up and during operation of the softener. With a change in the ionic composition of the source water (an increase or decrease in hardness associated with fluctuations depending on the season), the proposed control system allows you to determine the optimal filter cycle, thereby significantly saving table salt used to regenerate the softener, optimizing the consumption of saline wastewater.

Claims (1)

A method for controlling the operation of the Na-cationization unit of water, which consists in the fact that the initial hard water is supplied to the Na-cationization unit, while the hardness of the softened water obtained at the outlet is maintained within the range of 0.02-0.2 mg-eq / l, quality monitoring the operation of the installation of Na-cationization of water is carried out continuously according to two measured parameters, which are used as the specific electrical conductivity (EEC) of the source water and the ECD of softened water, and one design parameter, which is used as the difference between the ECD of softened and source water, and in the process During operation, the SEC value of softened water is constantly measured using a conductivity sensor with a transmitter and the measured SEC values are transmitted using a programmable logic controller (PLC) to a remote server for subsequent monitoring, while the transmitter converts the measured SEC value into a 4-20 mA current signal, which enters the PLC, then at least once a day the value of the SEC of the source water is measured with the same conductivity sensor, controlling the direction of the water flow using solenoid valves, while the value of the SEC of the source water is also transmitted to a remote server, then the difference between the values of the SEC of the softened and the source water is constantly determined, while the constancy the values of the UEP of softened water and the constancy of the difference between the UEP of softened water and the source water will make it possible to judge the quality of operation of the Na-cationization plant

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