RU2768440C1 - Water softening method - Google Patents

Abstract

FIELD: water Na-cationization.

SUBSTANCE: invention relates to technological processes of Na-cationization of water containing hardness ions, which are the cause of sludge and sedimentation in the main and auxiliary heat engineering and heat power equipment and technological pipelines, and can be used to obtain deeply softened water for use in various technological processes. The method consists in that the original hard water is preliminarily clarified, then sent to a block of Na-cation exchange filters, which consists of two filters. The source water is ensured to pass successively through two filters, as a result, the first N1 filter in the water direction works as the first softening stage, and the second N2 filter in the water direction works as the second softening stage. The hardness of softened water after the second filter is maintained at no more than 0.02 meq/l. After the end of the filter cycle of the N1 filter, the water flow is switched using solenoid valves and the N2 filter starts working as a first stage filter. In this case, the N1 filter is put into regeneration. During regeneration, only one filter is in operation. Due to the fact that the working filter, saturated with sodium salts, is at the beginning of the filter cycle, the hardness of softened water is maintained within 0.02 meq/l. Then, after the completion of the regeneration of the N1 filter, it is put into operation as the second stage of softening and provides deep water softening in case of depletion of the N2 filter to sodium salts. After the exhaustion of the N2 filter, which currently operates as the first stage, it goes into regeneration and the N1 filter becomes the first stage filter. Then the cycle repeats.

EFFECT: obtaining deeply softened water in a continuous mode of softening, using only two softening filters, as well as increasing the specific exchange capacity of the cation-exchange resin in the Na-form.

2 cl, 2 tbl, 1 ex, 2 dwg

Description

Technical field

The invention relates to technological processes of Na-cation exchange water softening, and can be used to obtain deeply softened water, according to the principle of two-stage Na-cation exchange water softening, for its subsequent use in various technological processes.

Prior Art

A known method of water desalination (option), which consists in the fact that the water is pre-clarified, sent to Na-cationite filters, while the hardness of the softened water is set in the range of 0.02-0.1 mg-eq / l, then the softened water is dosed hydrochloric acid solution, the amount of acid is chosen equivalent to the amount of sodium bicarbonate, then free carbon dioxide is removed from the water in the calciner, then the water is sequentially sent to the stages of the reverse osmosis desalination system, and the process of reverse osmosis desalination is carried out at least two stages along the line of the working concentrate, at the first stage reverse osmosis desalination system, the ratio of the initial flow to the working concentrate is set within 70-75%, then the working concentrate is sent to the second stage of the reverse osmosis desalination system, after the second stage the working concentrate is used as source water for the third stage of the reverse osmosis demineralization system pouring, while the operating pressure of the reverse osmosis desalination process is increased from the first stage to the last, from 10 to 50 bar, the working concentrate after the last stage of the reverse osmosis desalination system is sent to the brine tank, where sodium chloride is added, while the salinity is sufficient for regeneration of the Na filter the volume of the working concentrate after the last stage of the reverse osmosis desalination system is set within 30-50 g/l, from the saline tank the regeneration brine is pumped sequentially through the anion exchanger, and then through the cation exchanger from the bottom up with the waste regeneration solution drained after the filter for disposal (see Fig. RF patent for invention No. 2655995, IPC C02F 9/08; C02F 1/42, C02F 1/44; B01D61/12; C02F 103/04, publ. May 30, 2018).

The disadvantage of the known method of water desalination is that water softening is assumed in one stage, with water hardness of 0.1 mg-eq/l, which reduces the efficiency of the process of Na-cationic water softening in continuous softening mode.

A known method of degassing water, which consists in the fact that the water is pre-clarified, sent to Na-cation exchange filters, while the hardness of the softened water is maintained within the range of 0.02-0.1 mg-eq / l, then a solution of caustic soda is dosed into the softened water , while the amount of caustic soda is chosen no more than 10-15% of the amount of carbon dioxide in the water, then a solution of sodium sulfite is dosed into the water, while the amount of sodium sulfite is chosen based on the concentration of dissolved oxygen in the prepared water, then the water is sent to the reverse osmosis water desalination unit, at the same time, the ratio of permeate to the initial flow is set within 75-90%, then the resulting partially desalted and degassed permeate is sent to the consumer, and the concentrate is poured into the sewer (see RF patent for invention No. 2686146, IPC C02F 1/20; C02F 9/02 ; C02F 1/42; C02F 1/44; B01D 19/00; C02F 103/04, published 04/24/2019).

The disadvantage of the known method of water degassing is that water softening is assumed in one stage, with water hardness of 0.1 mg-eq/l, which reduces the efficiency of the process of deep Na-cationic water softening in continuous softening mode.

The closest in technical essence to the proposed invention is a well-known method for controlling the operation of the Na-cationization of water, which consists in the fact that the original hard water is supplied to the Na-cationization, while the hardness of the softened water obtained at the outlet is maintained within 0.02-0 ,2 mg-eq/l, monitoring of the quality of operation of the Na-cationization of water is carried out continuously according to two measured parameters, which use 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 raw water, and in the process of operation, the value of the SEC of softened water is constantly measured using an electrical 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 UE P into the current signal of 4-20 mA, which is fed to the PLC, then at least once a day the value of the SEC of the source water is measured with the same electrical conductivity sensor, controlling the direction of the water flow using electromagnetic valves, while the value of the SEC of the source water is also is transmitted to a remote server, then a constant determination of the difference between the SEC values of softened and source water is made, while the constancy of the values of the SEC of softened water and the constancy of the difference between the SEC of soft water and source water will make it possible to judge the quality of the Na-cationization unit (see Fig. RF patent for invention No. 2744346, IPC C02F 1/42, C02F 5/00, C02F 103/04, publ. 03/05/2021).

The disadvantage of the known method for controlling the operation of the installation for the preparation of softened water is that according to this scheme it is inefficient to obtain deeply softened water, since the softening process is supposed to be carried out in only one stage.

Disclosure of invention

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

The technical result achieved in solving this problem is the production of deeply softened water in a continuous mode of softening, using only two softening filters, as well as an increase in the specific exchange capacity of the cation-exchange resin in the Na-form.

This technical result is achieved by the fact that the water softening method, including preliminary clarification of the source hard water and direction to the block of Na-cation exchange filters, characterized in that the block of Na-cation exchange filters consists of two filters, while ensuring the passage of the source water sequentially through two filters , as a result, the first filter N1 along the water flow works as the first stage of softening, and the second filter N2 works as the second stage of softening, and the hardness of the softened water after the N2 filter is maintained at no more than 0.02 mg-eq / l, after the end of the filter cycle filter N1 with the help of electromagnetic valves, the water flow is switched and the filter N2 starts working as the first stage, while the filter N1 is put into regeneration, during regeneration only one filter is in operation, and due to the fact that the working filter saturated with sodium salts , is at the beginning of the filter cycle, maintaining the hardness of the softened water they are within 0.02 mg-eq/l, then after the completion of the regeneration of the N1 filter, it is put into operation as the second stage of softening and provides deep water softening in case of depletion of the N2 filter, which is currently operating as the first stage, in terms of salts sodium, after the depletion of the N2 filter, it goes into regeneration and the N1 filter, currently operating as the second stage, becomes operational as the first stage, then the cycle repeats.

It is advisable to determine the filter cycle using a meter installed on the softened water line.

Using this scheme, it is possible to obtain deeply softened water with a hardness of not more than 0.02 mg-eq / l. in continuous operation using only two Na-cationite filters. By not having a second separate softening stage, less cation exchange resin is needed to produce the same amount of deeply softened water compared to a traditional two-stage softening system. Due to this, there is a decrease in the amount of sodium chloride for the process of regeneration of the cation exchanger and, accordingly, a decrease in the amount of highly mineralized wastewater, as well as a decrease in water consumption for the regeneration of the cation exchange resin.

Brief description of the drawings

The essence of the invention is illustrated by drawings, which show: in Fig. 1 - technological scheme of the Na-cationic water softening system; in fig. 2 - graph of the dependence of the residual hardness of water after the first stage of softening, depending on the amount of water that has passed through the softening filter.

The designations in the drawing (Fig. 1) show the following: 1 - softening filter N1; 2 - softening filter N2; 1-1, 2-1, 3-1 - assembly consisting of electromagnetic and non-return valves, related to softening filter N1; 1-2, 2-2, 3-2 - assembly consisting of solenoid and non-return valves, related to the N2 softening filter. The black arrow shows the direction of water flow when the N1 filter is used as the second stage filter. The white arrow indicates the direction of water flow when the second stage is the N2 filter.

Detailed description of the invention

The proposed method of Na-cationite water softening is carried out as follows.

The water softening method contains the following technological stages (Fig. 1). The pre-clarified hard water is fed to the Na-cationite water softening plant. Water softening takes place in two stages. At the first stage, the main softening of water takes place. The second stage is softening. The result is deeply softened water with a residual hardness of not more than 0.02 mg-eq/l.

The system operates continuously. The fundamental possibility to organize continuous deep water softening in two successive stages using only two rather than four filters can be realized based on the operation of the Na-cationite water softening filter.

The filter of Na-cationic water softening consists of a hollow body filled with cation-exchange resin in Na-form. The height of the cation-exchange resin is chosen in such a way that water, passing through the cation exchanger from top to bottom, exchanges the divalent metal ions contained in it for monovalent sodium ions. As a result, the water leaving the filter contains mainly sodium ions. Nevertheless, multivalent calcium and magnesium ions (water hardness) remain in softened water in small concentrations. Therefore, to obtain deeply softened water with a concentration of hardness salts of not more than 0.02 mg-eq/l, two-stage softening is traditionally used. At the first stage of softening, water with a hardness of 0.1 meq/l is obtained, at the second stage, installed after the first stage, 0.02 meq/l or less.

In FIG. 2 shows a graph of the dependence of the residual hardness of water after the first stage of softening, depending on the amount of water that has passed through the softening filter. As can be seen from the graph, the first third of the resulting softened water has a hardness of not more than 0.02 mg-eq / l. Then the cation exchanger begins to deplete in sodium ions and the hardness of the softened water begins to increase. In order to use the full potential of the cation exchanger for hardness ions and at the same time obtain water with a residual hardness of not more than 0.02 mg-eq / l, the second stage of softening is used. At the first stage of softening, the process is carried out to a hardness of 0.5 meq/l. Then water with a hardness of not more than 0.5 meq/l is sent to the second stage and softened to a hardness of less than 0.02 meq/l.

After the depletion of the cation exchanger by sodium ions, it is regenerated with a concentrated solution of sodium chloride 6-8%. For regeneration, the filter is taken out of service.

In order for the water softening process to take place in a continuous mode, it is necessary to install two filters at the first stage of softening and two filters at the second stage of softening (one in regeneration, the second in operation for each stage). As a result, in order to obtain deeply softened water in continuous mode, it is required to install four softening filters.

This invention makes it possible to obtain deeply softened water using only two softening filters.

In FIG. 1 shows a schematic diagram of a water softening process using only two filters. In this case, the hardness of the resulting water will not exceed 0.02 mg-eq/l, which will allow it to be used, for example, for heat and power purposes.

The source water flow is divided into two lines. One softening filter is installed on each line. At the beginning, the original hard water is directed to filter N1 (1) by means of a system of solenoid valves (numbers in brackets indicate the number of the softening filter). Valve 1-1 is open, valve 1-2 is closed. The water then passes through the N1 softening filter and is directed to the N2 softening filter (2). Valve 3-1 is closed, valve 2-2 is open. In this case, the N2 filter acts as the second softening stage. Then the water goes to the consumer. Valve 3-2 is open, valve 3-1 is closed. The flow rate of softened water is determined using a pulse flow meter installed on the common softened water pipeline.

After the amount of water that has passed through the N1 filter becomes equal to the filter cycle set in advance, this filter will go into regeneration. Filter regeneration, depending on the size, can take up to 2 hours. Since the N1 filter cannot produce softened water when it is in the process of regeneration, the raw water is immediately sent to the N2 filter. Valves 1-1, 2-1, 3-1 are closed. Valves 1-2, 3-2 are open. During the regeneration of the N1 filter, the water is softened only in one step through the N2 filter.

Since the N2 filter is located at the very beginning of its filter cycle, even in one softening stage, water with a hardness of no more than 0.02 mg-eq / l is obtained. After the completion of the regeneration process, the N1 filter becomes operational as the second softening stage, thereby allowing the full use of the potential of the cation exchanger in terms of sodium ions of the N2 filter. For this mode, valves 1-2, 2-1, 3-1 are open and valves 1-1, 2-2, 3-2 are closed.

After the filter cycle for the N2 filter is completed, the cycle will repeat. Only the N2 filter will be put into regeneration, and the N1 filter will produce softened water at the beginning of its filter cycle, since working as a second stage already on softened water will practically not consume the ion exchange capacity of the cation exchanger. After completion of the regeneration of the N2 filter, it becomes operational as the second stage. Etc.

The process algorithm is organized in such a way that when only one filter is operating (the second is in regeneration), this filter is always at the beginning of its filter cycle and allows you to get deeply softened water.

As a result, it is possible to obtain deeply softened water by Na-cationization in continuous mode, using two rather than four filters. The use of salt is reduced due to a more complete use of the exchange capacity of the cation exchanger. The system begins to work more efficiently, due to the fact that only two filters are required to regenerate, rather than four filters. Moreover, source water is used for regeneration. Traditional schemes regenerate the second stage using water that has passed through the first stage, which reduces the useful filter cycle of the first stage. If the water has increased turbidity and color, it is recommended to make a partial loosening of the cation exchanger. In two-stage schemes with four filters, the second stage is regenerated relatively rarely, and the shelf life of the cation exchanger in such stages can be significantly lower than in the first stage, which is constantly loosened. This scheme is easily automated.

The invention is illustrated by the following example.

Example. Application of the system of Na-cationization of water according to the proposed method of water treatment for deep softening of water in domestic and drinking water supply. Softened water is prepared for use in a low pressure steam boiler. The composition of the source water is presented in table 1.

Table 1 Indicator unit of measurement Meaning General hardness mg-eq/l 4.2 total alkalinity mg-eq/l 2.5 chlorides mg/l 48 sulfates mg/l fifty sodium+potassium mg/l 16 Salinity mg/l 341 iron dissolved mg/l 0.1 Oxidability mg O ₂ /l 4.8 pH value units pH 6.8-7.0

The technological scheme of the water treatment system is shown in Fig. 1. The source water of this composition, after the installation of water clarification, enters the installation of deep Na-cationic water softening, consisting of two filters. The system ensures the passage of water through two filters in series. At the beginning, the source water enters the softening filter N1, which works as a softening filter of the first stage. Then, the water after the softening filter N1 enters the softening filter N2, which currently works as a softening filter of the second stage. Solenoid valve positions: 1-1, 2-2, 3-2 open, 1-2, 2-1, 3-1 closed. After the end of the filter cycle of the N1 filter, the N1 filter is regenerated. The N2 filter starts working as the first softening stage. After the completion of the regeneration of the N1 filter, the water flow is switched using solenoid valves and the N1 filter starts to work as the second softening stage. Valve positions: 1-2, 2-1, 3-1 open, 1-1, 2-2, 3-2 closed. After the end of the filter cycle of the N2 filter, the N2 filter goes into regeneration and the cycle repeats.

The softening filter columns are filled with ion-exchange resin by 70% of their volume. The ion exchange resin is initially in the Na ⁺ -form. The calcium and magnesium ions contained in the source water are exchanged in the column in the volume of the cation exchanger for sodium ions.

Table 2 shows the composition of deeply softened water.

table 2 Indicator unit of measurement Meaning General hardness mg-eq/l 0.02 total alkalinity mg-eq/l 2.5 chlorides mg/l 48 sulfates mg/l fifty sodium+potassium mg/l 112 Salinity mg/l 363 iron dissolved mg/l less than 0.1 Oxidability mg O ₂ /l 4.8 pH value units pH 6.8-7.0

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

The proposed simple technology of deep Na-cationite softening of the original natural water allows you to get a significant reduction in the cost of water treatment equipment, increase the reliability of the softening system, and also significantly more fully use the potential of the ion-exchange capacity of the cationite, respectively, with a decrease in the consumption of table salt for regeneration and a decrease in the amount of wastewater generated. .

Claims (2)

1. Method of water softening, including preliminary clarification of the source hard water and direction to the block of Na-cation exchange filters, characterized in that the block of Na-cation exchange filters consists of two filters, while ensuring the passage of the source water sequentially through two filters, as a result, the first filter N1 works as the first stage of softening, and the second filter N2 works as the second stage of softening, and the hardness of the softened water after the N2 filter is maintained at no more than 0.02 mg-eq / l, after the end of the filter cycle of the N1 filter using electromagnetic valves, the water flow is switched and the N2 filter starts to work as the first stage, while the N1 filter is put into regeneration, during regeneration only one filter is in operation, and due to the fact that the working filter saturated with sodium salts is at the beginning of the filter cycle , the hardness of softened water is maintained within 0.02 mg-eq / l, then after I regenerate the N1 filter, it is included in the work as the second stage of softening and provides deep water softening in case of depletion of the N2 filter, which currently operates as the first stage, by sodium salts, after the depletion of the N2 filter, it goes into regeneration and the N1 filter , which is currently operating as the second stage, becomes operational as the first stage, then the cycle repeats. 2. The method of softening water according to claim 1, characterized in that the filter cycle is determined using a meter installed on the softened water line.

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