JP2014014743A - Method and apparatus for treating salt waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert sodium chloride into an effectively utilizable material with high yield and high efficiency both inexpensively and with a low environmental load.SOLUTION: In a method for treating salt waster water, when assuming that the temperature of an aeration tank is T1(°C), for generating sodium carbonate and/or sodium hydrogen carbonate by bringing sodium hydroxide generated in a negative electrode inserted into a negative electrode room of an electrolytic tank into contact with carbon dioxide, and that the temperature of a precipitation tank is T2(°C), for crystallizing the sodium carbonate and/or the sodium hydrogen carbonate generated in the aeration tank, and recovering the crystal of the sodium carbonate and/or the sodium hydrogen carbonate and aqueous solution after being separated by solid-liquid separation, and that the temperature of a heat exchanger is T3(°C), for heating and supplying the aqueous solution of the sodium carbonate and/or the sodium hydrogen carbonate separated in the precipitation tank, into the negative electrode room of the electrolytic tank, following inequalities are satisfied simultaneously: T2<T1, T2<40.0(°C), and T2<T3<100.3(°C).

Description

  The present invention relates to a salt wastewater treatment method and a treatment apparatus therefor, and more particularly to a salt wastewater treatment method and a treatment apparatus suitable for volume reduction treatment of wastewater containing sodium chloride.

  In the mining of oil and gas fields, accompanying water containing salt is generated along with oil and natural gas. The accompanying water is usually returned to the wells of oil and gas fields in order to suppress land subsidence. However, with the increase in steam injection, etc. used for mining, in the case where an excessive amount of accompanying water is generated compared to the amount returned to the well, in recent years, the amount of generated accompanying water is not limited by treatment of the accompanying water from the viewpoint of environmental protection. There may be a need to approach zero. Also in seawater desalination, there is a case where the concentrated salt water is returned to the sea, which may cause a change in the environment, and it is desirable to reduce waste water containing salt as much as possible.

  Conventionally, there is a technique for reducing the amount of waste water (salt waste water) containing salt such as sodium chloride by concentration treatment by RO (Reverse Osmosis) membrane or heating.

  For example, Patent Document 1 adopts a method in which electricity, steam, and the like necessary for concentration of wastewater are covered by supply of power by an internal combustion engine such as a gas turbine and a generator, and supply of steam by a steam generator by heat of combustion exhaust gas. ing. This method has problems associated with improvement in energy use efficiency and reduction in the generation amount of exhaust gas such as carbon dioxide. Further, Patent Document 1 describes a method of further reducing the volume to a salt solid centered on NaCl by evaporating and drying the salt drainage.

  In order to reduce waste as much as possible, not only volume reduction, but also a device that converts waste into valuable resources and makes it easy to pick up in society, or if it can be used effectively, it can be digested. It is desirable to be added.

  From such a point of view, it is one promising means to reduce the volume to a solid salt and then purify and convert to salt. However, it is economically disadvantageous to produce sodium chloride from wastewater in that it requires various impurity removal steps as compared with the production cost of ordinary sodium chloride.

  In addition, from the viewpoint of physiological rejection of using products collected from waste, it is used in a manner that is as close to the normal manufacturing process as possible and has a low environmental impact including human health. It would be desirable to be able to convert to a product with high efficiency, and a technique to achieve this was desired with high yield.

  One example of a conventional method for converting water containing sodium chloride into other valuable resources is the production of caustic soda and liquefied chlorine by electrolysis.

In this method, manufacturing is performed using an electrochemical reaction represented by the following formula.
[Chemical 1]
2NaCl → 2Na ⁺ + 2Cl ⁻ → 2Na ⁺ + Cl ₂ + 2e ⁻
[Chemical formula 2]
2H ₂ O + 2e ⁻ → 2OH ⁺ + H ₂
In this reaction, an amount of charge equivalent to the amount of caustic soda produced is required, and therefore a large amount of direct current is required when carried out continuously on a large scale. The sodium chloride concentration is preferably lower from the viewpoint of current utilization efficiency, but is preferably higher from the viewpoint of facility scale. Considering these balances, when the sodium chloride concentration is adjusted to about 15% by weight, it is possible to reduce the equipment scale while maintaining the current utilization efficiency at a high level.

  In addition, chlorine ions are oxidized at the positive electrode and volatilized as chlorine gas, and the remaining sodium ions move to the negative electrode side. On the other hand, on the negative electrode side, hydrogen ions are reduced and the generated hydrogen gas is volatilized, and the remaining hydroxide ions generate sodium hydroxide (caustic soda) together with sodium ions.

  As for chlorine gas, it is usually by condensation of impurities centering on moisture by cooling to 0 to 15 ° C. (coarse purification), drying by aeration to concentrated sulfuric acid, compression and cooling to a chlorine boiling point (−34 ° C.) or lower. Through the liquefaction process, it is converted to liquefied chlorine. Liquefied chlorine is used as a raw material for synthesizing hydrochloric acid, vinyl chloride, hypochlorite and the like.

  Since chlorine gas is corrosive and harmful, it is necessary to select equipment for handling the gas before drying, selection of piping materials (glass lining material, Teflon (registered trademark) seal, etc.), detection of gas leaks, and the like. As hydrogen gas is a flammable gas, it is necessary to ensure sufficient exhaust and safety so that it does not remain in the electrolytic cell.

  Thus, in order to perform efficient electrolysis, it is necessary to secure a power source, concentrate salt water, and treat hydrogen gas. In addition, when applying the production technology of caustic soda and liquefied chlorine by electrolysis to salt wastewater treatment, in addition to the above, improvement in energy use efficiency necessary for utilities such as electricity and steam, and exhaust of carbon dioxide etc. A technique for solving the reduction in gas generation was required.

International Publication No. 2012/008013

  However, in the above-described conventional technology for producing caustic soda and liquefied chlorine by electrolysis, it is necessary to secure a power source, concentrate salt water, and treat hydrogen gas in order to perform efficient electrolysis. In addition, when applying the production technology of caustic soda and liquefied chlorine by electrolysis to the treatment of salt effluent, in addition to securing the power source, concentrating the salt water and treating the hydrogen gas, for the utilities such as electricity and steam described above A technique for solving the need for improving the required energy use efficiency and reducing the generation amount of exhaust gas such as carbon dioxide was necessary.

  The present invention has been made in view of the above points, and the object of the present invention is not only low cost, but also high yield and high efficiency in a substance that can effectively use sodium chloride with low environmental load. An object of the present invention is to provide a salt effluent treatment method and a treatment apparatus that can be converted.

  In order to solve the above problems, the salt drainage treatment method of the present invention is necessary for concentrating salt drainage containing sodium chloride to produce high-concentration salt drainage, and for concentrating the salt drainage. A high-concentration salt drainage is injected into an electrolytic cell composed of a positive electrode chamber, a negative electrode chamber and an ion exchange membrane separating the high-concentration salt drainage, and electrolysis is performed using the electrode to form water. A third step of generating sodium oxide, and a fourth step of obtaining sodium carbonate and / or sodium hydrogen carbonate by contacting carbon dioxide contained in the exhaust gas generated in the second step with the sodium hydroxide. And a fifth step of crystallizing the produced sodium carbonate and / or sodium hydrogen carbonate in a precipitation tank, and the crystallized sodium carbonate and / or sodium hydrogen carbonate as a solid-liquid fraction. A sixth step of separating and recovering the sodium carbonate and / or sodium hydrogen carbonate crystals and the aqueous solution by means of, and recovering the separated aqueous solution and supplying the separated aqueous solution to the negative electrode chamber of the electrolytic cell through a heat exchanger The temperature of the aeration tank for performing the fourth step is T1 (° C.), the temperature of the precipitation tank for performing the fifth step is T2 (° C.), and the seventh step. The following (Formula 1), (Formula 2), and (Formula 3) are satisfied at the same time when the temperature of the heat exchanger for performing is T3 (° C.).

(Formula 1): T2 <T1
(Formula 2): T2 <40.0 (° C.)
(Formula 3): T2 <T3 <100.3 (° C.)
Further, in order to solve the above problems, the salt wastewater treatment apparatus of the present invention is formed of a concentrating device for concentrating salt wastewater containing sodium chloride, a positive electrode chamber, a negative electrode chamber, and an ion exchange membrane separating the positive electrode chamber, An electrolyzer that electrolyzes salt wastewater concentrated by a concentrator, and a generator that generates electrical energy necessary for concentrating salt wastewater in the concentrator and electrolyzing salt wastewater in the decomposition layer An aeration tank for producing sodium carbonate and / or sodium hydrogen carbonate by contacting sodium hydroxide and carbon dioxide produced in the negative electrode inserted in the negative electrode chamber of the electrolytic cell, and produced in the aeration tank A precipitation tank for crystallizing the sodium carbonate and / or sodium bicarbonate and separating and recovering the sodium carbonate and / or sodium bicarbonate crystals and the aqueous solution by solid-liquid separation; The sodium carbonate was separated by the precipitation bath and / or by heating the aqueous solution of sodium hydrogen carbonate and a heat exchanger for supplying the anode chamber of the electrolytic cell,
When the temperature of the aeration tank is T1 (° C.), the temperature of the precipitation tank is T2 (° C.), and the temperature of the heat exchanger is T3 (° C.), the aeration tank, the precipitation tank, and the heat exchanger are as follows. (Formula 1), (Formula 2), and (Formula 3) are satisfied simultaneously.

(Formula 1): T2 <T1
(Formula 2): T2 <40.0 (° C.)
(Formula 3): T2 <T3 <100.3 (° C.)

  According to the present invention, it is possible to obtain an effect that can be converted into a substance capable of effectively using sodium chloride with a low environmental load in a high yield and with high efficiency as well as low cost.

It is a system configuration | structure which shows Example 1 of the processing apparatus of the salt waste water of this invention. It is a system configuration | structure which shows Example 2 of the processing apparatus of the salt waste_water | drain of this invention. It is a perspective view which shows the example of the electrolytic vessel employ | adopted as Example 1 and 2 of the processing apparatus of the salt waste water of this invention. FIG. 4 is a plan view of FIG. 3. It is a perspective view which shows the other example of the electrolytic vessel employ | adopted as Example 1 and 2 of the processing apparatus of the salt waste water of this invention. It is a perspective view which shows the further another example of the electrolytic cell employ | adopted as Example 1 and 2 of the processing apparatus of the salt waste water of this invention. It is a perspective view which shows the further another example of the electrolytic cell employ | adopted as Example 1 and 2 of the processing apparatus of the salt waste water of this invention. It is a characteristic view which shows the collection amount of sodium carbonate accompanying the temperature difference of an aeration tank and a precipitation tank. It is a characteristic view which shows the temperature dependence of the solubility to the water of sodium carbonate in this invention. It is a characteristic view which shows the temperature dependence of the solubility to the water of the carbon dioxide in this invention. It is a figure which shows the example which applies the processing apparatus of the salt waste_water | drain of this invention to an actual coal gas field.

As a result of intensive studies by the present inventors on the means for solving the above-mentioned problems, salt drainage containing sodium chloride discharged from the concentrator is electrolyzed in an electrolytic cell to obtain sodium hydroxide, which is then burned. By aeration of exhaust gas, carbon dioxide contained in the combustion gas is absorbed and reacted with sodium hydroxide to produce sodium hydrogen carbonate (sodium bicarbonate, NaHCO ₃ ) and / or sodium carbonate (Na ₂ CO ₃ ). The present invention has led to the invention of a salt effluent treatment method and a treatment device for fixing carbon dioxide and recovering these products efficiently.

  In particular, in the present invention, it is important to provide a precipitation tank for crystallizing the generated sodium hydrogen carbonate and / or sodium carbonate, and a system for re-feeding the aqueous solution separated after the precipitation to the electrolytic cell through a heat exchanger. Furthermore, the point is to efficiently recover sodium bicarbonate and sodium carbonate by controlling the temperature of the aeration tank (electrolysis tank depending on the configuration), precipitation tank, and heat exchanger.

  FIG. 11 shows an example in which the salt drainage treatment apparatus is applied to an actual coal gas field. The salt effluent treatment system shown in the figure includes an RO membrane system for treating salt effluent associated with a coal gas field, a system for obtaining clean water by a MED (Multi Effect Distillation) system, and a power / heat supply system for driving the system. And an electrolysis / volume-reduction system that treats high-concentration salt wastewater generated in the MED system to obtain valuable salts such as sodium carbonate and sodium hydrogencarbonate, and a chlorine purification / liquefaction system that treats chlorine gas generated by electrolysis Is done.

In FIG. 11, 101 is a gas field, 102 is a gas treatment device, 103 is a water absorption pump, 104 is a strainer, 105 is a pretreatment device such as an MF membrane or UF membrane, 106 is a pressurized air tank, 107 is an alkali supply tank, 108 is an acid supply tank, 109 is a neutralization tank, 110 is a high-pressure water pump, 111 is a RO membrane desalination device, 112 is a chemical cleaning / drainage treatment device, 113 is a pressure energy recovery device, and 114 is a backwashing device (blower). , 115 is a product gas supply blower, 116 is an MED device, 117 is a heat exchanger, 118 is a heat dissipation unit, 119 and 120 are ejectors, 121 is a gas turbine, 122 and 148 are generators, 123 is an exhaust heat recovery boiler, 124 , 125 and 126 are liquid feed pumps, 127 is a transformer, 128 is an electrolytic cell, 129 is a scrubber, 130 and 134 are powder separators, 131 132 liquid feed pump, 133 CO ₂ absorber, 135 sodium carbonate bath, 136 heat exchanger cooler, 137 gas-liquid separator, 138 is a dryer, 139 is concentrated sulfuric acid bath, 140, 141, 142 145, 152 are liquid feed pumps, 143 is a sulfuric acid concentration tank, 144 is a chlorine gas liquefying device, 146 is a liquefied chlorine tank, and 147 is a steam turbine.

By aeration of combustion exhaust gas to sodium hydroxide obtained by electrolysis, carbon dioxide contained in the combustion exhaust gas is absorbed and reacted with caustic soda to react with sodium bicarbonate (sodium bicarbonate, NaHCO ₃ ) and / or sodium carbonate (Na ₂ CO ₃ ) is generated to fix carbon dioxide, and when this is recovered, it is converted into an aqueous solution of caustic soda to increase the amount of dissolved and absorbed carbon dioxide as compared with an aqueous solution of sodium chloride.

  As a method of aeration, there are a method of performing aeration directly on the electrolytic cell, a method of aerating the alkaline solution discharged from the electrolytic cell to the aeration tank, and the like. In the method of performing aeration directly on the electrolytic cell, for example, the aeration cell is the same as the negative electrode chamber of the electrolytic cell.

When aerated directly in an electrolytic cell or when aerated with an alkaline solution discharged from the electrolytic cell, the temperature of the reaction solution is increased by the heat of electrolysis or combustion exhaust gas, so the solubility of NaHCO ₃ or Na ₂ CO ₃ increases There is a merit that can be recovered as. As a method for aeration of the alkaline solution discharged from the electrolytic cell, for example, there is a method of using an ejector to draw and dissolve the exhaust gas by the negative pressure accompanying the flow rate of the solution and the narrowing of the flow path.

Moreover, when aerated with an alkaline solution, it is usually necessary to lower the temperature of a certain combustion exhaust gas in advance at about 150 to 200 ° C. From the viewpoint of effectively using this thermal energy, the present inventors have come up with the idea of evaporating and removing moisture in the liquid by exhaust gas exhaust heat and drying NaHCO ₃ and Na ₂ CO ₃ .

Thereby, the final product can be recovered as a solid using the heat of the exhaust gas. At that time, not only the free water but also the crystallization water of NaHCO ₃ and Na ₂ CO ₃ can be devolatilized. Moreover, when assuming NaHCO ₃ which is a glass raw material as a final product, it is desirable that crystallization water is removed from the viewpoint of safety in a high-temperature process during glass production.

  In particular, according to the present invention, sodium hydroxide is produced from salt effluent by electrolysis, and sodium chloride and carbon dioxide are reacted to increase the efficiency of producing sodium bicarbonate and / or sodium carbonate. The details will be described below.

  Embodiment 1 of the salt wastewater treatment apparatus of the present invention will be described.

  FIG. 1 shows Example 1 of the apparatus for treating salt waste water of the present invention. As shown in the figure, the salt effluent treatment apparatus of the present embodiment includes an electrolysis mechanism such as an electrolyzer 14, a MED (evaporation concentration apparatus) 2, a power generation mechanism including a generator 24, and a control mechanism including an arithmetic unit 1. ing.

  Then, as shown in FIG. 1, the high concentration salt water 29 from the salt drain 41 and the electrolytic cell 14 is supplied to the MED 2 by the pump 7 or the like, where it is concentrated and purified into the clean water 30 and the high concentration salt drain 28. To be separated. The separated clean water 30 can also be supplied to the negative electrode side.

  The separated high-concentration salt drainage 28 is supplied to the electrolytic cell 14. At this time, the electric power for operating the MED 2 is electric energy 23 supplied from the generator 24 driven by the gas turbine 12. The number of the gas turbines 12 and the generators 24 may be increased to two or more as necessary when the power is insufficient. Moreover, by providing a plurality of gas turbines in this way, it can be used as a backup in case of failure.

  As described above, the high-concentration salt drain 28 supplied from the MED 2 to the electrolytic cell 14 is in the positive electrode chamber of the electrolytic cell 14, and the sodium carbonate aqueous solution 34 heated by the heat exchanger 13 is in the negative electrode chamber of the electrolytic cell 14. Supplied respectively.

  In the electrolytic cell 14, the high-concentration salt drainage 28 in the positive electrode chamber and the sodium carbonate aqueous solution 34 in the negative electrode chamber are electrolyzed by the current flowing from the electrodes inserted in the positive electrode chamber and the negative electrode chamber, respectively. It is converted into an aqueous sodium solution 26. In the positive electrode chamber and the negative electrode chamber, there are a water level meter (+) 3 and a water level meter (−) 4 for measuring the water level, a salt concentration meter (+) 5 and a salt concentration meter (−) 6 for measuring the salt concentration. The measured values measured by the water level meter (+) 3, the water level meter (−) 4, the salt concentration meter (+) 5, and the salt concentration meter (−) 6 are input to the arithmetic unit 1. ing. Furthermore, in this embodiment, a chlorine ion concentration meter (+) 31 for measuring the chlorine ion concentration in the positive electrode chamber of the electrolytic cell 14 is provided, and the measured chlorine ion concentration data in the positive electrode chamber is input to the arithmetic unit 1. It has become.

  The chlorine gas 18 generated in the positive electrode chamber during the electrolysis in the electrolytic cell 14 is supplied to the cooler 8, cooled by the cooler 8, and then separated and washed into water vapor and salts by the mist separator 9. The Then, after drying with the drying tower 10 to which the concentrated sulfuric acid 19 is supplied, it is cooled and pressurized by the cooler 11 and stored as liquid chlorine 21 in the tank. The generated hydrogen is supplied to the gas turbine 12 as fuel. The high-concentration salt water 29 discharged from the positive electrode chamber of the electrolytic cell 14 is supplied again to the MED 2 and concentrated. Reference numeral 20 denotes a route of waste sulfuric acid from the drying tower 10.

On the other hand, in the negative electrode chamber of the electrolytic cell 14, a sodium hydroxide aqueous solution 26 is formed by the above reaction, and is introduced into the aeration tank 15 through the pump 7. In this aeration tank 15, the sodium hydroxide aqueous solution 26 and the carbon dioxide in the exhaust gas 25 react with each other by bringing the sodium hydroxide aqueous solution 26 into contact with the exhaust gas 25 containing carbon dioxide introduced from the CO ₂ blowing section 16. , Conversion to sodium bicarbonate 27 and / or sodium carbonate. Sodium hydrogen carbonate 27 and / or an aqueous sodium carbonate solution generated in the aeration tank 15 is introduced into the precipitation tank 42.

  In the precipitation tank 42, the sodium hydrogen carbonate 27 and / or sodium carbonate is precipitated by setting the temperature different from that of the aeration tank 15 and utilizing the temperature dependency of the solubility of the substance in water. For example, as shown in FIG. 8, by setting the temperature of the aeration tank 15 to T1 and the temperature of the precipitation tank 42 to T2, an amount corresponding to the solubility difference W1-W2 can be recovered.

  In this embodiment, the centrifugal separation mechanism 17 is used as a means for collecting the precipitate in the precipitation tank 42. The centrifugal separation mechanism 17 can efficiently separate and collect the precipitate and the aqueous solution from the solid-liquid material.

  Next, hydrogen gas 22 is supplied as fuel from the positive electrode chamber of the electrolytic cell 14 to the gas turbine 12, and the generator 24 is driven by the gas turbine 12 to generate power. The electric energy 23 generated by the generator 24 is used for the operation of the MED 2 and the electrolytic cell 14.

  In the present embodiment, by using such electrical energy 23 from the generator 24, exhaust heat from the gas turbine 12, high-concentration salt waste water 28 from the MED 2, etc., hydrogen carbonate can be converted from energy that has been wasted conventionally. The purpose is to produce valuables such as sodium 27 and / or sodium carbonate.

  An important point for efficiently recovering the target sodium hydrogen carbonate 27 and / or sodium carbonate solids of the present embodiment is that the temperatures of the aeration tank 15, the precipitation tank 42, and the heat exchanger 13 are set to T1 respectively. , T2, and T3, the following relationship is satisfied at the same time.

(Formula 1): T2 <T1
(Formula 2): T2 <40 ° C.
(Formula 3): T2 <T3 <100.3 (° C.)
Here, the target product is precipitated and recovered using the temperature dependence of the solubility in water. In general, the higher the temperature of the aqueous solution, the higher the solubility, and the lower the temperature, the lower the solubility.

  Therefore, in order to precipitate the target efficiently, it is necessary to set the temperature (T2) of the precipitation tank 42 lower than the temperature (T1) of the aeration tank 15 (T2 <T1). This condition corresponds to (Equation 1).

  FIG. 9 shows the temperature dependence of the solubility of sodium carbonate in water in this example. The difference in solubility at the temperature shown in FIG. 9 can be collected. From the solubility curve of sodium carbonate, it can be seen that it has a maximum value in the vicinity of 40 ° C., and the solubility hardly changes at a temperature higher than that.

  That is, even if the condition of (Equation 1) is satisfied, when T2 is 40 ° C. or higher, there is almost no difference in solubility due to the temperature difference between T1 and T2, and thus precipitation in the precipitation tank 42 is difficult. When T2 is lower than 40 ° C., precipitation of the target product due to solubility difference can be expected. From this, the above (Formula 2) can be derived.

  Furthermore, the temperature (T3) of the heat converter 13 needs to be higher than at least the temperature (T2) of the precipitation tank 42. Under conditions where T3 is lower than T2, sodium bicarbonate 27 and sodium carbonate are deposited in the heat exchanger 13. In this case, for example, the piping in the vicinity of the heat exchanger 13 is clogged, causing a problem as a continuous system.

  On the other hand, the upper limit of T3 is 100.3 ° C. This is a temperature at which the aqueous solution passing through the heat exchanger 13 is not boiled. In general, the boiling point of water is 100 ° C., but since the sodium carbonate remains slightly dissolved in the aqueous solution here, the boiling point can be increased.

  From the solubility curve of sodium carbonate shown in FIG. 9, even if the temperature T2 of the precipitation tank 42 is set to 0 ° C., 6 g of sodium carbonate is dissolved in 100 g of water. If the boiling point rise is calculated using this value, the degree of boiling point rise ΔT = 0.34 ° C. (= 0.515 K kg / mol × 0.66 mol / kg) can be calculated.

  Therefore, if at least T3 is 100.3 ° C. or lower, the aqueous solution can pass through the heat exchanger 13 without boiling. From these, the above (Formula 3) is derived.

  From the above, in this example, in order to efficiently precipitate and recover sodium bicarbonate 27 and / or sodium carbonate, at least the above (Formula 1), (Formula 2), and (Formula 3) are used. It is necessary to satisfy at the same time.

  Further, in order to efficiently recover sodium carbonate and the like, it is desirable to satisfy the following (Formula 4).

(Formula 4): 35.0 <T1 <45.0 (° C.)
In the present embodiment, as described above, the temperature T1 of the aeration tank 15 is preferably higher as long as it is at least higher than the temperature T2 of the precipitation tank 42 from the viewpoint of solubility. However, in consideration of the formation of sodium bicarbonate 27 and sodium carbonate, the condition of (Equation 4) is required.

  In this embodiment, sodium hydrogen carbonate 27 and / or sodium carbonate is generated by blowing exhaust gas 25 containing carbon dioxide into the aeration tank 15. The solubility of carbon dioxide in water is as shown in the temperature dependence shown in FIG. That is, the lower the temperature, the higher the solubility of carbon dioxide. For example, the solubility of carbon dioxide at 0 ° C. is about 4 times that at 60 ° C. That is, by increasing the solubility of carbon dioxide, the production of sodium hydrogen carbonate 27 and sodium carbonate in the aeration tank 15 can be promoted.

  For this reason, the temperature T1 of the aeration tank 15 is preferably in a temperature range in which both (1) increasing the solubility of carbon dioxide and (2) increasing the solubility of sodium hydrogen carbonate 27 are compatible. In the temperature range of (Formula 4), (1) and (2) can be satisfied simultaneously. Furthermore, the temperature T1 of the aeration tank 15 is desirably around 40 ° C. at which the solubility is maximum.

  Further, the lower limit value of the temperature T2 of the precipitation tank 42 is considered as follows. Considering precipitation of sodium carbonate or the like, it is preferable that the difference from the temperature T1 of the aeration tank 15 is large. That is, the lower the temperature T2 of the precipitation tank 42, the better. However, it is necessary to consider a lower limit for the temperature T2 of the precipitation tank 42 as well. When the temperature is set to an extremely low temperature, there is a concern that the aqueous solution itself may solidify in addition to the intended precipitation of sodium carbonate.

  In the present embodiment, in consideration of this point, the lower limit value of the temperature T2 of the precipitation tank 42 is set as follows. That is, the temperature at which the aqueous solution itself solidifies was set as the lower limit. In the aqueous solution in which the target sodium carbonate is precipitated by lowering the temperature T2 of the precipitation tank 42 to 0 ° C., about 6 g of sodium carbonate is dissolved (FIG. 9).

  In such an aqueous solution, sodium carbonate is an impurity and causes a freezing point depression, so the aqueous solution does not solidify at normal 0 ° C. When the freezing point depression of this aqueous solution is calculated, it can be calculated as follows.

ΔT = Kf × m = 1.86 × 0.66 = 1.2 (K)
Here, ΔT is the freezing point depression (K), Kf is the freezing point depression coefficient, and m is the molar concentration of sodium carbonate.

  This shows that the aqueous solution does not solidify up to -1.2 ° C. Therefore, it is better that the temperature is lower than the temperature T2 of the precipitation tank 42 and the temperature T1 of the aeration tank 15, but the lower limit is −1.2 ° C. at which the aqueous solution does not solidify.

  From this, (Equation 5) was determined.

(Formula 5): -1.2 <T2 (° C)
Further, when the present system is operated, the temperature T1 of the aeration tank 15 may be in an environment as shown in (Expression 6). That is, the temperature T1 of the aeration tank 15 is lower than 40 ° C. In such a case, the conditions described in (Equation 7) are particularly essential. That is, it is necessary to set the temperature T3 of the heat exchanger 13 to a temperature higher than the temperature T1 of the aeration tank 15.

(Formula 6): T1 <40 (° C.)
(Formula 7): T1 <T3
For example, as shown in FIG. 1, the recovered aqueous solution is re-supplied to the aeration tank 15 via the heat exchanger 13. Therefore, the aqueous solution temperature from the heat exchanger 13 affects the aqueous solution temperature in the aeration tank 15. In the temperature range in which the temperature T1 of the aeration tank 15 is higher than 40 ° C., precipitation of sodium carbonate in the aeration tank 15 hardly occurs even if the temperature slightly changes due to the inflow of the aqueous solution from the heat exchanger 13. . This is because the solubility hardly changes when the temperature T1 of the aeration tank 15 is 40 ° C. or higher as shown in the solubility curve of sodium carbonate in FIG.

  However, when the temperature T1 of the aeration tank 15 is 40 ° C. or less, the solubility greatly depends on the temperature. Therefore, if the temperature in the aeration tank 15 is lowered by the inflow from the heat exchanger 13, the inside of the aeration tank 15 This causes the problem of precipitation of sodium carbonate. In order to solve this, it is necessary to set the temperature of the heat exchanger 13 higher than at least the temperature of the aeration tank 15. For these reasons, in the case of the environment of (Expression 6), it is necessary to satisfy (Expression 7).

  Note that the aqueous solution separated in the precipitation tank 42 may be supplied again to the negative electrode chamber of the electrolytic tank 14 via the heat exchanger 13. In the separated aqueous solution, sodium hydrogen carbonate 27 and sodium carbonate partially remain and dissolve, and are returned again to the negative electrode chamber of the electrolytic cell 14 and passed through the precipitation step, so that sodium hydrogen carbonate is more efficiently obtained. 27 and sodium carbonate can be recovered.

  Further, the temperature T2 of the precipitation tank 42 needs to be adjusted as described above, and for example, needs to be set lower than that of the aeration tank 15. When a temperature higher than room temperature is required, the aqueous solution can be heated using the electrical energy 23 from the generator 24. On the other hand, in order to lower the temperature from room temperature, a cooling function like a refrigerator is required. In the case of a general refrigerator, the electric energy 23 from the generator 24 may be used. Moreover, when utilizing the following absorption refrigerators, the exhaust heat from the gas turbine 12 can also be utilized, for example.

  The absorption refrigerator is a refrigerator that absorbs a refrigerant in a liquid having a high absorption capacity and vaporizes the refrigerant by a low pressure generated at that time to obtain a low temperature. For example, water having high absorption power uses water and the refrigerant uses ammonia, for example. In such a refrigerator, cold water can be obtained by putting the exhaust heat into the refrigeration apparatus. The precipitation tank 42 can be cooled by using the exhaust water from the gas turbine 12 or the like and using the cold water obtained by the absorption refrigerator.

  By adopting such a configuration of the present embodiment, sodium hydroxide is generated by electrolysis of the salt effluent, and this sodium hydroxide and carbon dioxide are reacted so that sodium bicarbonate (sodium bicarbonate) 27 and / or carbonate The efficiency of producing sodium can be increased.

  Therefore, according to the present example, not only the cost is low, but also an effect that the sodium chloride can be effectively used with a low environmental load can be converted with high yield and high efficiency. Further, in salt wastewater treatment, it becomes possible to preferentially produce a more valuable salt, and to minimize the salt concentration in the salt wastewater. Furthermore, in addition to reducing the amount of carbon dioxide emitted from the generator driven by the fossil-derived fuel turbine installed to cover the power used for this facility, the temperature of the wastewater can be lowered, which has an impact on the environment. Can be reduced.

  Next, a second embodiment of the salt wastewater treatment apparatus of the present invention will be described.

  FIG. 2 shows a second embodiment of the apparatus for treating salt water of the present invention.

  In the first embodiment described above, the negative electrode chamber of the electrolytic cell 14 and the aeration tank 15 are different, but in this example shown in FIG. 2, the negative electrode chamber of the electrolytic cell 14 also serves as the aeration tank 15. ing.

  In this embodiment, exhaust gas 25 containing carbon dioxide is introduced into the negative electrode chamber of the electrolytic cell 14, and carbon dioxide is brought into contact with sodium hydroxide in the negative electrode chamber, so that sodium hydrogen carbonate and / or sodium carbonate is obtained. Convert to Sodium hydrogen carbonate 27 and / or sodium carbonate aqueous solution generated in the negative electrode chamber of the electrolytic cell 14 is introduced into the precipitation tank 42, and the precipitation tank 42 is set to a temperature different from that of the negative electrode chamber of the electrolytic cell 14 which also serves as an aeration tank, By utilizing the temperature dependence of the solubility of the substance in water, sodium bicarbonate 27 and / or sodium carbonate is precipitated.

  In this embodiment, since the centrifugal separation mechanism 17 is used as a means for collecting the precipitate in the precipitation tank 42, the centrifugal separation mechanism 17 can efficiently separate and collect the precipitate and the aqueous solution from the solid-liquid material. And sodium bicarbonate 27 and / or sodium carbonate can be obtained.

  In this embodiment, since the negative electrode chamber of the electrolytic cell 14 is also used as the aeration tank, the temperature T1 is the temperature of the negative electrode chamber of the electrolytic cell 14.

  Even in the configuration of the present embodiment, the same effects as those of the first embodiment can be obtained, and there is an advantage that the configuration is simplified and the cost is reduced because there is no aeration tank.

  3 and 4 show an example of an electrolytic cell employed in Examples 1 and 2 of the present invention. In the figure, 200 is an electrolytic cell constituting an electrolytic cell, 201 is a positive electrode chamber, 202 is a negative electrode chamber, 203 is high-concentration salt water filled in the positive electrode chamber 201, 204 is negative electrode electrolyzed water filled in the negative electrode chamber 202, 205 is a positive electrode, 206 is a negative electrode, 207 is a temperature sensor of the positive electrode chamber 201, 207 'is a temperature sensor of the negative electrode chamber 202, 208 is a salt concentration sensor of the positive electrode chamber 201, 208' is a salt concentration sensor of the negative electrode chamber 202, and 209 is Chlorine gas, 210 is a chlorine gas recovery port, 211 is a hydrogen gas discharge port, 212 is a negative electrode electrolyzed water 204 inlet, 213 is a high-concentration salt water inlet, 214 is hydrogen gas, and 215 is a negative electrode electrolyzed water 204 A discharge port, 216 is a positive electrode high-concentration salt water discharge port, 217 is a water level meter in the positive electrode chamber, 218 is a water level meter in the negative electrode chamber, 219 is a positive electrode terminal, 220 is a negative electrode terminal, and 221 is an ion exchange membrane.

  The positive electrode chamber 201 and the negative electrode chamber 202 are installed adjacent to each other only through the ion exchange membrane 221, and the positive electrode 205 and the negative electrode 206 are adjacent to the ion exchange membrane 221 in the positive electrode chamber 201 and the negative electrode chamber 202, respectively. The ion exchange membrane 221 is laid in parallel. The positive electrode 205 and the negative electrode 206 are provided with a positive electrode terminal 219 and a negative electrode terminal 220, respectively. The positive electrode 205 and the negative electrode 206 are preferably made of a plate made of copper, platinum, gold, iridium oxide, or the like, and these may have a mesh shape installed on a current collector. Further, the positive electrode 205 and the negative electrode 206 are preferably arranged as close to the ion exchange membrane 221 as possible in order to minimize loss due to resistance during electrolysis.

  As the ion exchange membrane 221, a semi-permeable membrane that selectively transmits cations such as sodium is used. Although this film moves sodium ions from the positive electrode to the negative electrode side, chloride ions and hydroxide ions cannot permeate the film, so that chlorine is contained in the positive electrode chamber 201 and sodium hydroxide is contained in the negative electrode chamber 202. Accumulated. If the ion exchange membrane 221 is not provided, it is not preferable because chloride ions, hydroxide ions, and sodium ions react with each other to form sodium hypochlorite and the like.

  The positive electrode chamber 201 is provided with an introduction port 213 and a discharge port 216 for introducing the high-concentration salt water 203, and the high-concentration salt water 203 is input and drained. Further, the negative electrode chamber 202 is provided with an inlet 212 and a discharge port 215 for introducing the negative electrode electrolyzed water 204, and the negative electrode electrolyzed water 204 is input and discharged. Here, the negative electrode electrolyzed water 204 is introduced in order to perform electrolysis with low resistance, and is salt water containing a large amount of sodium ions and the like.

  Furthermore, the positive electrode chamber 201 is provided with a recovery port 210 for recovering chlorine gas 209 generated by electrolysis, and the negative electrode chamber 202 is provided with a recovery port 211 for recovering hydrogen gas 214 generated by electrolysis. Yes.

  The positive electrode chamber 201 and the negative electrode chamber 202 are provided with temperature sensors 207 and 207 ′, salt concentration sensors 208 and 208 ′, and water level meters 217 and 218, respectively. The temperature, salt concentration, and water level measured by these are transferred as data to the arithmetic device 1 shown in the first and second embodiments.

  In the electrolytic cell 14 configured in this manner, when an electric field is generated between the positive electrode 205 and the negative electrode 206, a current is generated across the ion exchange membrane 221, and sodium ions flow from the positive electrode 205 side to the negative electrode 206 side. The above-described electrochemical reaction of Chemical Formula 1 and Chemical Formula 2 occurs at the electrode, and chlorine is generated on the positive electrode 205 side and hydrogen is generated on the negative electrode 206 side. At the same time, sodium hydroxide is formed. It is accumulated in the negative electrode electrolyzed water 204.

  The electrolytic cell 200 is preferably provided with a small volume with respect to the electrode in order to efficiently electrolyze the high-concentration salt water 203 that has passed therethrough. In order to increase the amount of the treatment liquid, a plurality of the electrolytic cells 200 are installed in parallel. Thus, it is preferable to perform an electric field.

  In FIG. 5, the other example of the electrolytic cell employ | adopted as Example 1 and 2 of this invention is shown. In the example shown in the drawing, the exhaust gas 25 containing carbon dioxide from the generator 24 is aerated in the negative electrode chamber 202, and sodium hydroxide and carbon dioxide generated in the negative electrode electrolyzed water 204 in the negative electrode chamber 202 are aerated in the negative electrode chamber 202. This is an electrolytic cell for obtaining sodium bicarbonate 27 and / or sodium carbonate. In FIG. 5, 222 is a carbon dioxide inlet, and 223 is a carbon dioxide outlet.

  By using the electrolytic cell 200 shown in FIG. 5, it is possible to react sodium carbonate produced on the negative electrode side directly with carbon dioxide to produce sodium bicarbonate 27 and / or sodium carbonate.

  FIG. 6 shows still another example of the electrolytic cell employed in Examples 1 and 2 of the present invention. The example shown in the figure shows an electrolytic cell in which a plurality of electrolytic cells 200 shown in FIGS. 3 and 4 are arranged in parallel.

  In FIG. 6, 200 is an electrolysis cell, 224 is a recovery tube for recovering hydrogen generated in the negative electrode chamber of each electrolysis cell, 225 is a recovery tube for recovering chlorine generated in the positive electrode chamber of each electrolysis cell 200, and 226 is negative electrode electrolysis An introduction pipe for water 204, 227 is an introduction pipe for high-concentration waste water introduced into the positive electrode chamber, 228 is a discharge pipe for negative electrode electrolyzed water 204, and 229 is a discharge pipe for high-concentration salt drainage in the positive electrode chamber.

  FIG. 6 shows an example in which the electrolysis cells 200 shown in FIG. 3 are connected in parallel, but the number of cells in parallel is not particularly limited to this, and a large-capacity electrolyzer such as 80 to 100 cells is used. It is also possible to form.

  In the example shown in FIG. 6, the hydrogen recovery pipe 224 is a pipe that connects the recovery port 211 provided in the negative electrode chamber of each electrolysis cell 200 in parallel, and is supplied again as fuel for the gas turbine 12, and if necessary. Exhaust by power from a blower (not shown).

  The chlorine recovery pipe 225 is a pipe connecting the chlorine gas recovery port 210 provided in the positive electrode chamber of each electrolysis cell 200 in parallel, and the coolers 8 and 11, the mist separator 9, the drying tower of FIGS. 1 and 2. 10 is introduced into a chlorination section composed of 10 to form liquid chlorine 21 and finally carried out as a valuable resource. Exhaust by power such as a blower (not shown) if necessary.

  Further, these liquids are supplied to the electrolysis cell 200 by power of a liquid feed pump or the like separately provided through the introduction pipe 226 for the negative electrode electrolyzed water 204 and the introduction pipe 227 for the high-concentration salt drain to be introduced into the positive electrode. Further, the negative electrode electrolyzed water 204 is fed to a sodium carbonate or sodium hydrogen carbonate recovery unit by power of a liquid feed pump or the like separately provided through the discharge pipe 228 of the negative electrode electrolyzed water 204, and the high-concentration salt water 203 filled in the positive electrode chamber. Is introduced into the MED 2 or the negative electrode chamber 202 through the discharge pipe 229 of the high concentration salt drainage of the positive electrode.

  FIG. 7 shows still another example of the electrolytic cell employed in each embodiment of the present invention. The example shown in the figure shows an electrolytic cell in which a plurality of electrolytic cells 200 having a mechanism for aeration of carbon dioxide shown in FIG. 5 are arranged in parallel.

  In FIG. 7, reference numeral 230 denotes an introduction pipe for the exhaust gas 25 containing carbon dioxide. The introduction pipe 230 is a pipe for connecting the carbon dioxide introduction ports 222 of the electrolysis cells 200 in parallel, and is introduced using power such as a blower (not shown) as necessary.

  When aeration of carbon dioxide shown in FIGS. 5 and 7 is performed in the negative electrode chamber, nitrogen, oxygen, moisture, and unreacted carbon dioxide contained in the exhaust gas 25 are introduced into the negative electrode, and are supplied from the hydrogen exhaust pipe 224. Although it is sent to the gas turbine 12 together with hydrogen as a fuel, there is no problem in the combustion of the gas turbine 12 even if these gases are mixed.

  Hereinafter, application examples by the present inventors will be described.

In the application example shown below, the salt drainage treatment apparatus of Example 2 shown in FIG. 2 is used. In the salt effluent treatment apparatus of Example 2, the aeration tank also serves as the negative electrode chamber of the electrolytic tank. In these salt wastewater treatment apparatuses, the setting of the temperature T1 of the aeration tank, the temperature T2 of the precipitation tank, and the temperature T3 of the heat converter differs for each application example.
Application example 1
The application example which processes the accompanying water discharged | emitted from a gas field with the system shown in FIG.2 and FIG.11 is demonstrated.

  In this application example, carbon dioxide gas is introduced in the negative electrode chamber of the electrolytic cell. That is, since the aeration tank is also used as the negative electrode chamber of the electrolytic cell, the aeration tank and the negative electrode chamber of the electrolytic cell are the same.

  The temperature T1 of the aeration tank, the temperature T2 of the precipitation tank, and the temperature T3 of the heat exchanger are set to 80 ° C., 20 ° C., and 40 ° C., respectively. This is a condition that satisfies the above (Formula 1), (Formula 2) and (Formula 3) simultaneously.

  Concentrated high-concentration salt drainage is obtained by passing the accompanying water through the RO system and MED. When this high-concentration salt drainage was analyzed, the concentrations of cation species and anion species were as follows.

Cationic species:
Na 59,000 mg / L,
Other cations 700 mg / L or less.

Anionic species:
Cl 77, 200 mg / L,
CO ₃ 181 mg / L,
HCO ₃ 23,000 mg / L,
Other anions 700 mg / L or less.
Moreover, COD is 300 mg / L or less.

  From the above, in the high-concentration salt drainage, except for water, sodium chloride (12.8 g (2.2 mol) in 12 000 mg / L: 1 L), sodium carbonate (247 mg / L: 0.247 g in 1 L) (0.0033 mol)), a substance consisting mainly of sodium hydrogen carbonate (32,000 mg / L: 32 g (0.38 mol) in 1 L). Therefore, this application example is a case where the sodium chloride concentration exceeds 10%.

  This salt drainage is put into the positive electrode chamber 201 of the electrolytic cell 200 shown in FIG. The negative electrode chamber 202 is charged with 60,000 mg / L sodium carbonate aqueous solution. This is the electrolyzed water concentration after passing through the centrifugal separation mechanism 17 shown in FIG. The internal methods of the positive electrode side and the negative electrode side of the electrolysis cell 200 are both 1 m × 1 m × 0.01 m, and the volume is 10 L. The water temperature at the time of introduction of both is 70 ° C.

  Here, a voltage of 3 V and a current of 60 A are energized. Then, bubbles of chlorine gas are generated from the positive electrode, and electrolysis proceeds. As the electrolysis progresses, sodium ions in the positive electrode chamber 201 move to the negative electrode chamber 202 and the sodium ion concentration in the positive electrode chamber 201 decreases. However, the sodium concentration in the positive electrode chamber 201 and the negative electrode chamber 202 is reduced by the sodium ion concentration adjusting mechanism. Since the difference is 3% or more, this state is set as a steady state, and high-concentration salt drainage is allowed to flow into a stable operation state.

  At this time, 90,000 mg / L high-concentration salt water of sodium chloride is discharged from the discharge port from the positive electrode chamber 201 and is again charged into the MED 2. This shows that an amount of sodium corresponding to 38,000 mg / L of sodium chloride moves to the negative electrode chamber 202.

  Along with this, the sodium ion concentration in the negative electrode chamber 202 becomes 72,000 mg / L. This indicates an increase of 12,000 mg / L sodium ion compared to the initial 60,000 mg / L. This shows that 21,000 mg / L of sodium hydroxide is generated in the negative electrode chamber 202.

  The exhaust gas 25 of the gas turbine 12 is blown into this to perform sodium carbonate conversion of sodium hydroxide, and it is crystallized and collected as a powder (sodium bicarbonate 27) in a tank.

The exhaust gas composition used in this application example is shown below.
(Exhaust gas composition)
N ₂ : 70.0%
O ₂ : 13.0%
CO ₂ : 3.4%
H ₂ O: 11.0%
Ar: 0.9%
Other: 11.7%
The gas temperature immediately after being discharged from the gas turbine 12 is 330 ° C. This gas is sent to the negative electrode chamber of the electrolytic cell 14 through the heat exchanger 13, and the temperature after passing through the heat exchanger 13 is 180 ° C. Since the carbon dioxide concentration is 0.01% or more, it becomes a normal operating condition. The sodium carbonate recovered at this time becomes 5.5 kg when the flow rate of the high-concentration salt water passing through the electrolytic cell 14 is 100 L.

As shown in FIG. 7, when 86 cells are juxtaposed in parallel as shown in FIG. 7 and processing of 8600 L is performed, 473 kg of sodium carbonate can be recovered.
Application example 2
In this application example, as compared with the application example 1, only the settings of the temperature T1 of the aeration tank, the temperature T2 of the precipitation tank, and the temperature T3 of the heat exchanger are different, and the other systems are the same as those of the application example 1.

  In this application example, the temperature settings are T1 = 40 ° C., T2 = 20 ° C., and T3 = 40 ° C., respectively. This condition satisfies (Expression 4) in addition to (Expression 1), (Expression 2), and (Expression 3).

  The drainage composition, gas composition, and electrolysis conditions are the same as in Application Example 1.

  The sodium carbonate recovered at this time becomes 6.0 kg when the flow rate of the high-concentration salt water passing through the electrolytic cell 14 is 100 L.

As shown in FIG. 7, when 86 cells are juxtaposed in parallel as shown in FIG. 7 and processing of 8600 L is performed, 516 kg of sodium carbonate can be recovered.
Application Example 3
In this application example, as compared with the application example 1, only the settings of the temperature T1 of the aeration tank, the temperature T2 of the precipitation tank, and the temperature T3 of the heat exchanger are different, and the other systems are the same as those of the application example 1.

  In this application example, the temperature settings are T1 = 80 ° C., T2 = 0 ° C., and T3 = 40 ° C., respectively. This condition satisfies (Expression 4) and (Expression 5) in addition to (Expression 1), (Expression 2), and (Expression 3).

  The sodium carbonate recovered at this time becomes 11.0 kg when the flow rate of the high-concentration salt water passing through the electrolytic cell 14 is 100 L.

As shown in FIG. 7, when 86 cells are juxtaposed in parallel as shown in FIG. 7 and processing of 8,600 L is performed, 950 kg of sodium carbonate can be recovered.
Application Example 4
In this application example, as compared with the application example 1, only the settings of the temperature T1 of the aeration tank, the temperature T2 of the precipitation tank, and the temperature T3 of the heat exchanger are different, and the other systems are the same as those of the application example 1.

  In this application example, the temperature settings are T1 = 35 ° C., T2 = 0 ° C., and T3 = 40 ° C., respectively. This condition satisfies (Expression 6) and (Expression 7).

  The sodium carbonate recovered at this time becomes 11.0 kg when the flow rate of the high-concentration salt water passing through the electrolytic cell 14 is 100 L.

  As shown in FIG. 7, when 86 cells are juxtaposed in parallel as shown in FIG. 7 and processing of 8,600 L is performed, 960 kg of sodium carbonate can be recovered.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Operation apparatus, 2 ... MED (evaporation concentration apparatus), 3 ... Water level meter (+), 4 ... Water level meter (-), 5 ... Salt concentration meter (+), 6 ... Salt concentration meter (-), 7 ... pumps, 8,11 ... cooler, 9 ... mist separator, 10 ... drying tower, 12,121 ... a gas turbine, 13,208 ... heat exchanger, 14,128 ... electrolyzer, 15 ... aeration tank, 16 ... CO ₂ Blowing unit, 17 ... centrifugation mechanism, 18,209 ... chlorine gas, 19 ... concentrated sulfuric acid, 20 ... waste sulfuric acid, 21 ... liquid chlorine, 22 ... hydrogen gas, 23 ... electric energy, 24, 122,148 ... generator, 25 ... exhaust gas, 26 ... sodium hydroxide aqueous solution, 27 ... sodium bicarbonate, 28 ... high-concentration salt water, 29 ... high-concentration salt water, 30 ... water, 31 ... chlorine ion concentration meter (+), 33 ... blower, 34 ... Sodium carbonate aqueous solution, 41 ... Salt drainage, 42 ... Precipitation DESCRIPTION OF SYMBOLS 101 ... Gas field, 102 ... Gas processing apparatus, 103 ... Water absorption pump, 104 ... Strainer, 105 ... Pretreatment apparatus, 106 ... Pressurized air tank, 107 ... Alkali supply tank, 108 ... Acid supply tank, 109 ... Neutralization Tank, 110 ... High pressure water pump, 111 ... RO membrane desalination device, 112 ... Chemical cleaning / wastewater treatment device, 113 ... Pressure energy recovery device, 114 ... Backwash device, 115 ... Product gas supply blower, 116 ... MED device, 118 ... Radiating section, 119, 120 ... Ejector, 123 ... Waste heat recovery boiler, 124, 125, 126, 131, 132, 140, 141, 142, 145, 152 ... Liquid feed pump, 127 ... Transformer, 129 ... Scrubber , 130, 134 ... powder separator, 133 ... CO ₂ absorber, 135 ... soda bath, 136 ... heat exchange type condenser, 1 37 ... Gas-liquid separator, 138 ... Dryer, 139 ... Concentrated sulfuric acid tank, 143 ... Sulfuric acid concentration tank, 144 ... Chlorine gas liquefier, 146 ... Liquefied chlorine tank, 147 ... Steam turbine, 200 ... Electrolytic cell, 201 ... Positive electrode 202, negative electrode chamber, 203 ... high-concentration salt water filled in the positive electrode chamber, 204 ... negative electrode electrolyzed water, 205 ... positive electrode, 206 ... negative electrode, 207 ... temperature sensor in the positive electrode chamber, 207 '... temperature sensor in the negative electrode chamber, DESCRIPTION OF SYMBOLS 208 ... Salt concentration sensor of positive electrode chamber, 208 '... Salt concentration sensor of negative electrode chamber, 210 ... Chlorine gas recovery port, 211 ... Hydrogen gas discharge port, 212 ... Negative electrode electrolyzed water inlet, 213 ... High concentration salt water Inlet, 214 ... Hydrogen gas, 215 ... Negative electrode electrolyzed water outlet, 216 ... Positive electrode high-concentration salt water outlet, 217 ... Positive electrode chamber water level meter, 218 ... Negative electrode chamber water level meter, 219 ... Positive electrode terminal, 220 ... Negative terminal, 2 21 ... ion exchange membrane, 222 ... carbon dioxide inlet, 223 ... carbon dioxide outlet, 224 ... recovery tube for recovering hydrogen generated in the negative electrode chamber, 225 ... recovery tube for recovering chlorine generated in the positive electrode chamber, 226 ... Negative electrode electrolyzed water introduction pipe, 227 ... High concentration salt drainage introduction pipe introduced into the positive electrode chamber, 228 ... Negative electrode electrolysis water discharge pipe, 229 ... High concentration salt drainage discharge pipe in the positive electrode chamber, 230 ... Exhaust gas Introduction tube.

Claims (12)

A first step of producing high-concentration salt drainage by concentrating salt drainage containing sodium chloride, a second step of generating electrical energy necessary for concentrating the salt drainage, and the high-concentration salt drainage A third step of injecting into an electrolytic cell composed of a positive electrode chamber, a negative electrode chamber and an ion exchange membrane separating the positive electrode chamber, and electrolyzing with an electrode to generate sodium hydroxide; A fourth step of obtaining sodium carbonate and / or sodium bicarbonate by contacting carbon dioxide contained in the exhaust gas generated in step 2, and crystallization of the produced sodium carbonate and / or sodium bicarbonate in a precipitation tank And the crystallized sodium carbonate and / or sodium hydrogen carbonate is combined with sodium carbonate and / or sodium hydrogen carbonate by solid-liquid separation. Includes a sixth step of separating and recovering an aqueous solution, through the heat exchanger to recover an aqueous solution prepared by the separation, and a seventh step of supplying the separated aqueous solution in the anode chamber of the electrolytic cell and,
The temperature of the aeration tank for performing the fourth step is T1 (° C.), the temperature of the precipitation tank for performing the fifth step is T2 (° C.), and the temperature of the heat exchanger for performing the seventh step is T3. A salt effluent treatment method characterized by satisfying the following (formula 1), (formula 2) and (formula 3) at the same time as (° C).
(Formula 1): T2 <T1
(Formula 2): T2 <40.0 (° C.)
(Formula 3): T2 <T3 <100.3 (° C.) In the salt effluent treatment method according to claim 1,
The aeration tank in which the fourth step is performed is the same as the negative electrode chamber of the electrolytic tank. In the processing method of the salt drainage of Claim 1 or 2,
The salt drainage processing method characterized by satisfying the following (formula 4).
(Formula 4): 35.0 <T1 <45.0 (° C.) In the processing method of the salt drainage of Claim 1 or 2,
The salt drainage processing method characterized by satisfying the following (Formula 5).
(Formula 5): -1.2 <T2 (° C) In the processing method of the salt drainage of Claim 1 or 2,
A salt effluent treatment method characterized by satisfying the following (Equation 7) under the conditions of the following (Equation 6).
(Formula 6): T1 <40.0 (° C.)
(Formula 7): T1 <T3 (° C.) In the processing method of the salt waste_water | drain of any one of Claims 1 thru | or 5,
The salt effluent treatment method, wherein electricity and steam generated in the second step are used in the fifth step. In the processing method of the salt waste_water | drain of any one of Claims 1 thru | or 5,
The salt effluent treatment method, wherein electricity and steam generated in the second step are used in the seventh step. A concentration device for concentrating salt wastewater containing sodium chloride, an electrolytic cell for electrolyzing the salt wastewater formed by the concentration device and formed by a positive electrode chamber, a negative electrode chamber and an ion exchange membrane separating the positive electrode chamber, and the concentration device; A generator for generating electrical energy necessary for concentrating salt effluent and electrolyzing salt effluent in the decomposition layer, and hydroxylation generated in the negative electrode inserted in the negative electrode chamber of the electrolytic cell An aeration tank in which sodium and carbon dioxide are brought into contact to produce sodium carbonate and / or sodium hydrogen carbonate, and the sodium carbonate and / or sodium hydrogen carbonate produced in the aeration tank is crystallized, and sodium carbonate is obtained by solid-liquid separation. And / or a precipitation tank that separates and recovers the sodium hydrogen carbonate crystals and the aqueous solution, and the sodium carbonate and / or sodium hydrogen carbonate separated in the precipitation tank. And a heat exchanger for supplying the anode chamber of the electrolytic cell by heating an aqueous solution of um,
When the temperature of the aeration tank is T1 (° C.), the temperature of the precipitation tank is T2 (° C.), and the temperature of the heat exchanger is T3 (° C.), the aeration tank, the precipitation tank, and the heat exchanger are as follows. A salt effluent treatment apparatus characterized by satisfying (Formula 1), (Formula 2) and (Formula 3) simultaneously.
(Formula 1): T2 <T1
(Formula 2): T2 <40.0 (° C.)
(Formula 3): T2 <T3 <100.3 (° C.) In the processing apparatus of the salt drainage of Claim 8,
The aeration tank also serves as a negative electrode chamber of the electrolytic tank. In the saltwater treatment apparatus according to claim 8 or 9,
The aeration tank satisfies a condition of 35.0 <T1 <45.0 (° C.). In the saltwater treatment apparatus according to claim 8 or 9,
The precipitation tank satisfies -1.2 <T2 (° C.). In the saltwater treatment apparatus according to claim 8 or 9,
The aeration tank satisfies T1 <T3 (° C.) when T1 <40.0 (° C.).

Images