JP4592555B2 - Concentration treatment apparatus and neutralization treatment method - Google Patents

Description

  The present invention relates to a concentration treatment apparatus and a neutralization treatment method for concentrating an aqueous solution containing a volatile acid solution such as hydrochloric acid or phosphoric acid.

  Conventionally, as an apparatus for concentrating an aqueous solution containing a volatile acid solution such as hydrochloric acid or phosphoric acid, a concentration processing apparatus as disclosed in Patent Document 1 is known.

  The concentration processing apparatus disclosed in Patent Document 1 includes an evaporator 110, a steam duct 120, and a condenser 130 as shown in the schematic configuration diagram of FIG. The evaporator 110 contains a concentrated acid solution and an acidic gas by spraying and evaporating an aqueous solution containing a volatile acid solution stored at the bottom on the surface of the indirect heating tube 107 through the pipe 103 and the spray nozzle 105. It is a device that generates steam. The steam duct 120 is a flow path that guides the acidic gas-containing steam generated by the evaporator 110 to the condenser 130, and an alkaline liquid spray nozzle 125 that sprays the alkaline liquid supplied from the alkaline liquid supply pipe 140 therein. It has. The condenser 130 is a device that generates condensed water by condensing the steam that has passed through the steam duct 120.

The concentration processing apparatus 100 configured in this manner neutralizes and removes the acidic gas generated together with the water vapor in the evaporator 110 by bringing the acidic gas into contact with the alkaline liquid sprayed from the alkaline liquid spray nozzle 125 in the steam duct 120. It is to do.
Japanese Patent Laid-Open No. 7-24202

  However, when the aqueous solution containing the volatile acid solution is concentrated by the concentration treatment device disclosed in Patent Document 1, it is difficult to perform a sufficient neutralization reaction, and the condensed water generated in the steam duct or the condenser is There was a problem that acid gas melts and corrosion due to acidic condensate occurs in the steam duct and condenser.

  In addition, in order to perform a sufficient neutralization reaction, it is necessary to lengthen the contact time between the acid gas and the alkali liquid, so that the duct becomes larger and the equipment cost increases, and an apparatus for performing the concentration treatment is installed. There was a problem that the place was restricted.

  The present invention has been made to solve such a problem, and it is an object of the concentration treatment apparatus and the neutralization treatment method capable of concentrating a volatile acid solution with a compact configuration while preventing internal corrosion. For the purpose of provision.

The above-mentioned object of the present invention is to produce a condensed acid solution and an acid gas-containing vapor by evaporating and concentrating an aqueous solution containing a volatile acid solution, and producing condensed water by condensing the introduced vapor. A condensing device configured to guide the acid gas-containing vapor generated by the evaporator to the condenser through a flow path, and the flow path sprays an alkaline liquid. This is achieved by a concentration treatment apparatus comprising: an alkaline liquid spraying apparatus that performs the above-described process, and an auxiliary spraying apparatus that recirculates and sprays the condensed water generated by the condenser on the downstream side of the alkaline liquid spraying apparatus.

The condenser includes a condenser main body having an opening to which the flow path is connected, and a heat transfer tube installed inside the condenser main body, and the opening and the heat transfer tube In the meantime, it is preferable that a buffer member that prevents the condensed water sprayed from the auxiliary spraying device and flowing from the opening toward the heat transfer tube from directly colliding with the heat transfer tube is provided.

Further, the above object of the present invention is to evaporate and concentrate an aqueous solution containing a volatile acid solution to produce a concentrated acid solution and an acid gas-containing vapor, and to condense condensed water by condensing the introduced vapor. An acid gas-containing vapor flowing in the flow path in a concentration processing apparatus configured to guide the acid gas-containing vapor generated in the evaporator to the condenser via a flow path. A neutralization treatment method for neutralizing an alkaline gas spraying step in which an alkaline liquid is sprayed onto the acidic gas-containing vapor flowing through the flow path, and the condenser at a downstream side of the alkaline liquid spraying area of the flow path . And an auxiliary spraying step of refluxing and spraying the condensed water produced in step (ii).

  ADVANTAGE OF THE INVENTION According to this invention, the concentration processing apparatus and neutralization processing method which can concentrate a volatile acid liquid with a compact structure can be provided, preventing internal corrosion.

  An apparatus for concentrating an aqueous solution containing a volatile acid solution according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a concentration processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the concentration treatment apparatus 1 includes an evaporator 10, a steam duct 21, and a condenser 30.

  The evaporator 10 includes a sealed evaporation chamber 11, a stock solution spray nozzle 12, and an indirect heater 13. The evaporation chamber 11 is connected to a stock solution supply pipe 61 extending from a stock solution tank (not shown) at the bottom thereof, and can store an aqueous solution containing a volatile acid solution supplied from the stock solution tank at the bottom of the evaporation chamber 11. It is configured to be able to. Further, a vapor duct 21, which is a flow path for guiding acidic gas-containing vapor generated in the evaporator 10 to the condenser 30, is connected to the upper portion of the evaporation chamber 11.

  As will be described later, the stock solution spray nozzle 12 is a supply unit that supplies an aqueous solution containing a volatile acid solution stored at the bottom of the evaporation chamber 11 toward the outer surfaces of the plurality of heating tubes 14. 11 is provided in the upper part. The stock solution spray nozzle 12 and the bottom of the evaporation chamber 11 are connected by a circulation line 62 having a circulation pump, and the aqueous solution stored in the bottom of the evaporation chamber 11 is dispersed through the circulation line 62. It is configured to be supplied to the nozzle 12. Further, in the middle of the circulation pipe 62, there is a concentrated acid solution discharge pipe 63 for discharging the concentrated acid solution accumulated at the bottom of the evaporation chamber 11 to the outside at the end of the concentration treatment of the aqueous solution containing the volatile acid solution. It is connected.

  The indirect heater 13 includes a plurality of heating tubes 14 provided in the evaporation chamber 11, and a first header 15 and a second header 16 connected to both ends of the plurality of heating tubes 14, respectively. The plurality of heating tubes 14 are arranged along the vertical direction. A heating steam supply pipe 64 to which heating steam is supplied is connected to the lower part of the first header 15, and the upper part of the connection part between the heating steam supply pipe 64 and the first header 15 is the first header 15. The 1st partition member 15a which partitions off the inside of 1 header 15 is provided. A heating steam discharge pipe 65 for discharging the heating steam flowing in the heating pipe 14 to the outside is connected to the upper portion of the second header 16, and a connection portion between the heating steam discharge pipe 65 and the second header 16. A second partition 16a member for partitioning the inside of the second header 16 is provided below. The second partition 16a member is configured so that the heating steam introduced into the first header 15 from the heating steam supply pipe 64 is guided to the second header 16 through the heating pipes 14a and 14a, and then the heating pipe 14b is connected. In the second header 16 so as to be discharged to the outside via the heating steam discharge pipe 65 after being led to the second header 16 via the heating pipe 14c. Is provided.

  The steam duct 21 is a flow path that guides the acidic gas-containing steam generated in the evaporator 10 to the condenser 30, and includes an alkaline liquid spraying device 22 and an auxiliary spraying device 23 therein.

  The alkaline liquid spraying device 22 is connected to an alkaline liquid storage tank (not shown) via an alkaline liquid supply pipe 66. Examples of the alkaline liquid sprayed from the alkaline liquid spraying device 22 include a sodium hydroxide aqueous solution and a calcium hydroxide aqueous solution.

  The auxiliary spraying device 23 is arranged on the downstream side (condenser 30 side) of the alkaline liquid spraying device 22, and is connected to the condensed water storage unit 33 of the condenser 30 through the condensed water circulation pipe 67. It is comprised so that the condensed water produced | generated by 30 can be recirculated and sprinkled.

  The condenser 30 is a device that generates condensed water by condensing the steam generated by the evaporator 10 and guided through the steam duct 21. The condenser body 31, the heat transfer pipe 32, the condensed water storage section 33, and A buffer member 34 is provided. An opening 35 to which the steam duct 21 is connected is formed in the upper part of the condenser body 31.

  A plurality of heat transfer tubes 32 are provided inside the condenser main body 31, and industrial water cooled by a cooling tower (not shown) or cold water (chiller water) cooled by a refrigeration apparatus is supplied via a cooling water pipe 68. The heat transfer tube 32 is configured to flow inside. The steam guided from the evaporator 10 exchanges heat with the cooling water flowing inside the heat transfer tubes 32 on the outer surfaces of the plurality of heat transfer tubes 32, and is deprived of heat and converted into condensed water.

  The condensed water storage unit 33 is a member that stores condensed water that is condensed by the heat exchange action of the heat transfer tube 32, and is provided in the lower part of the condenser body 31. A condensed water circulation pipe 67 for guiding the stored condensed water to the auxiliary spraying device 23 is connected to the condensed water storage unit 33. A condensed water discharge pipe 69 for discharging condensed water to the outside is connected to the condensed water circulation pipe 67.

  The buffer member 34 is a flat plate-like member, and is installed in the condenser main body 31 by a support member (not shown). The shape of the buffer member 34 in plan view is not particularly limited, and may be, for example, a circular shape or a rectangular shape. Further, the buffer member 34 is disposed immediately below the opening 35 of the condenser body 31 and between the opening 35 and the heat transfer tube 32. The size of the flat buffer member 34 is such that the condensed water sprayed from the auxiliary spraying device 23 and passing through the steam duct 21 and flowing from the opening 35 toward the heat transfer tube 32 does not directly collide with the heat transfer tube 32. It is formed in a size that can be done. Further, in order to prevent the condensed water colliding with the buffer member 34 from collecting on the upper surface of the buffer member 34 and smoothly flow downward, each of the flat buffer members 34 as shown in the sectional view of FIG. It is preferable to bend the sides obliquely downward.

  A method of concentrating an aqueous solution containing a volatile acid solution typified by hydrochloric acid or phosphoric acid using the concentration processing apparatus 1 configured as described above will be described below.

  The aqueous solution containing the volatile acid solution stored at the bottom in the evaporation chamber 11 is supplied to the stock solution spray nozzle 12 through the circulation pipe 62 by the action of the circulation pump. The aqueous solution supplied to the stock solution spray nozzle 12 is sprayed on the outer surface of each heating tube 14 in the indirect heater 13 by the stock solution spray nozzle 12, and a part of the water in the aqueous solution evaporates by heating here. As a result, water vapor is generated. At this time, a part of the volatile acid liquid is also vaporized together with the evaporation of water to generate an acidic gas.

  The aqueous solution that has not evaporated on the outer surface of each heating tube 14 flows down along the outer surface of each heating tube 14, returns to the aqueous solution stored at the bottom of the evaporation chamber 11, and passes through the circulation line 62 again. Then, it is supplied to the stock solution spray nozzle 12. The aqueous solution at the bottom in the evaporation chamber 11 is circulated through the circulation line 62 until the processing by evaporation and concentration is completed. Note that the concentrated acid solution generated by evaporating and concentrating the aqueous solution at the bottom in the evaporation chamber 11 is discharged to the outside through the concentrated acid solution discharge pipe 63 at the end of the concentration process.

  The acidic gas-containing vapor generated in the evaporation chamber 11 by the heating action of each heating pipe 14 of the indirect heater 13 is guided to a vapor duct 21 connected to the upper portion of the evaporation chamber 11.

  The acidic gas-containing steam guided to the steam duct 21 passes through the alkaline liquid spraying area by the alkaline liquid spraying device 22 and then passes through the condensed water spraying area by the auxiliary spraying device 23 to remove the acidic gas and the condenser. 30. The flow rate and alkali concentration of the alkaline liquid sprayed from the alkaline liquid spraying device 22 is such that the PH value of the condensed water discharged from the condenser 30 to the outside via the condensed water discharge pipe 69 is, for example, the water pollution prevention method. It is calculated by calculation based on the acid concentration of the aqueous solution containing the volatile acid solution so that it is within the range of the regulated wastewater regulation value. In particular, from the viewpoint of preventing acid dew point corrosion, it is preferable that the PH value is set to 7 or more and less than or equal to the upper limit value of the drainage regulation value. Further, the flow rate of the condensed water sprayed from the auxiliary spraying device 23 depends on the condensing capacity of the condenser 30. For example, the flow rate of the condensed water discharged from the condenser 30 through the condensed water discharge line 69 is 50. % Or more is preferable.

  A part of the acidic gas-containing steam guided to the steam duct 21 is cooled by heat exchange with the outside air while passing through the steam duct 21, and is condensed as acidic condensed water in the steam duct 21. Since the alkaline liquid is sprayed from the alkaline liquid spraying device 22, the acidic condensed water generated in the steam duct 21 is neutralized by the alkaline liquid to become a neutralized liquid. Thereby, acid dew point corrosion in the steam duct 21 can be prevented. The neutralized condensed water is guided to the condenser 30 along with the flow of the acidic gas-containing steam and stored in the condensed water storage portion 33.

  Further, part of the acidic gas constituting the acidic gas-containing vapor is directly dissolved in the alkaline liquid and neutralized when passing through the alkaline liquid spraying area.

  The alkaline liquid sprayed from the alkaline liquid spraying device 22 is guided to the condensed water spraying area together with water vapor containing acid gas remaining without being neutralized by the alkaline liquid. In this condensed water spraying area, the condensed water is sprayed from the auxiliary spraying device 23 to the alkaline liquid sprayed from the alkaline liquid spraying device 22 and the water vapor containing the acid gas remaining without being neutralized by the alkaline liquid. As a result, the reaction area of the neutralization reaction between the acid gas and the alkali liquid increases due to the dispersion of the condensed water. As a result, the neutralization reaction is promoted, the contact time between the alkaline liquid and the acidic gas is shortened, and the acidic gas can be efficiently removed from the water vapor containing the acidic gas.

  Next, the water vapor from which the acid gas has been removed is introduced into the condenser 30 from the opening 35 of the condenser body 31, and is converted into condensed water on the outer surface of the heat transfer tube 32 by the heat exchange action of the heat transfer tube 32. It is stored in the condensed water storage part 33. A part of the condensed water stored in the condensed water storage unit 33 is guided to the auxiliary spraying device 23 via the condensed water circulation pipe 67 and sprayed in the steam duct 21. The remaining condensed water is discharged to the outside through the condensed water discharge pipe 69.

  In addition, temporarily, the acidic gas that has not been neutralized by the action of the alkaline liquid spraying device 22 and the auxiliary spraying device 23 flows into the condenser 30 together with water vapor, and acidic condensed water is generated on the outer surface of the heat transfer tube 32. Even so, a large amount of condensed water sprayed from the auxiliary spraying device 23 adheres to the outer surface of the heat transfer tube 32 and forms a liquid film covering the surface, so that the acid that condenses on the surface of the heat transfer tube 32. The acid concentration of the condensed water can be kept low. Further, since the liquid film covering the outer surface of the heat transfer tube 32 contains the alkaline liquid sprayed from the alkaline liquid spraying device 22, a neutralization reaction is also performed on the surface of the heat transfer tube 32, and the heat transfer tube 32. It is possible to effectively prevent acid dew point corrosion.

  Since the buffer member 34 is provided inside the condenser 30, it is possible to receive the impact of water sprayed from the auxiliary spraying device 23 and flowing from the opening 35 of the condenser body 31 toward the heat transfer tube 32. . As a result, it is possible to prevent the heat transfer tube 32 from being damaged by the impact of water flowing from the opening 35. Furthermore, since the condensed water sprayed from the auxiliary spraying device 23 collides with the buffer member 34 and then is dispersed inside the condenser main body 31, each heat transfer tube 32 installed inside the condenser 30. It is possible to form a liquid film of condensed water containing an alkaline liquid over a wide range of the outer surface. As a result, the acidic gas that has not been neutralized by the action of the alkaline liquid spraying device 22 and the auxiliary spraying device 23 flows into the condenser 30 together with water vapor, and acidic condensed water is generated on the outer surface of the heat transfer tube 32. However, since this acidic condensed water is neutralized over a wide range of the heat transfer tube 32, it is possible to more effectively prevent acid dew point corrosion from occurring in the heat transfer tube 32.

  Thus, according to the concentration processing apparatus 1 which concerns on this embodiment, it can prevent that the steam duct 21, the heat exchanger tube 32 of the condenser 30, etc. are damaged by acid dew point corrosion. As a result, an inexpensive material such as stainless steel (SUS316), for example, can be used without using a high-grade material such as titanium having corrosion resistance as a material for the steam duct 21 or the heat transfer tube 32. Reduction can also be achieved.

  Further, by spraying water from the auxiliary spraying device 23 to the alkaline liquid sprayed from the alkaline liquid spraying device 22 and the water vapor containing the acidic gas remaining without being neutralized by the alkaline liquid, As a result of increasing the reaction area of the neutralization reaction, accelerating the neutralization reaction, and shortening the contact time between the acid gas and the alkaline liquid, the volatile acid liquid can be efficiently concentrated. At the same time, the steam duct can be miniaturized and the concentration processing apparatus can be made compact.

  Further, the flow rate and the alkali concentration of the alkaline liquid sprayed from the alkaline liquid spraying device 22 is such that the PH value of the condensed water discharged from the condenser 30 is defined as 7 or more in the Water Pollution Control Law, for example. Since the amount is set to be within the upper limit value of the regulation value, it can be discharged as it is from the condensed water discharge line 69 without adjusting the PH value of the condensed water generated in the condenser 30. Thus, it is possible to efficiently perform the concentration treatment of the aqueous solution containing the volatile acid solution. Moreover, since an excessive alkaline liquid is not sprayed from the alkaline liquid spraying device 22, the amount of the alkaline liquid used can be reduced, and the cost required for the neutralization process can be reduced.

  Moreover, in this embodiment, since the condensed water produced | generated by the condenser 30 is recirculated and reused as the water sprayed from the auxiliary spraying device 23, the cost required for the neutralization process is reduced. It is possible to simplify and downsize the water spraying system.

  The inventors perform concentration processing of an aqueous solution containing phosphoric acid using the concentration processing apparatus 1 including the condenser 30 having the heat transfer tube 32 formed of stainless steel (SUS316), and the steam duct 21 and the condenser 30. An experiment was conducted to confirm whether or not acid dew point corrosion occurred. An aqueous sodium hydroxide solution is used as the alkaline liquid, and an alkaline liquid spraying device 22 sprays an amount such that the PH value of the condensed water discharged from the condenser 30 is 7.6 based on the phosphoric acid concentration of the stock solution. did. In addition, the flow rate of the condensed water sprayed from the auxiliary spraying device 23 was set to 50% of the flow rate discharged to the outside from the condenser 30 via the condensed water discharge pipe 69.

  As a result, it was confirmed that the occurrence of acid dew point corrosion was effectively prevented in the steam duct 21 and the condenser 30. Moreover, the PH value of the condensed water produced | generated by the condenser 30 and stored in the condensed water storage part 33 was 7.2, and was the value which can be discharged | emitted outside without adjusting PH at the time of drainage. The PH value of the condensed water stored in the condensed water storage unit 33 does not coincide with the calculated value (PH value = 7.6) because the raw solution supplied from the raw solution supply pipe 61 to the bottom of the evaporation chamber 11 This seems to be because the phosphoric acid concentration of is not constant.

  As mentioned above, although one Embodiment of this invention was described, the specific aspect of this invention is not limited to the said embodiment. For example, in the present embodiment, the auxiliary spraying device 23 is configured to recirculate and spray the condensed water generated by the condenser 30. For example, fresh water supplied from a water tank (not shown) provided separately. May be configured to spray. The fresh water is water such as tap water or industrial water and has a PH value of about 7.

  Moreover, you may comprise so that alkali liquid may be spread | dispersed from the auxiliary | assistant spraying apparatus 23. When such a configuration is employed, acid dew point corrosion occurs in the steam duct 21 and the condenser 30 by appropriately adjusting the flow rate and concentration of the alkaline liquid sprayed from the alkaline liquid sprayer 22 and the auxiliary sprayer 23, respectively. Furthermore, the PH value of the condensed water discharged from the condenser 30 to the outside via the condensed water discharge pipe 69 is, for example, not less than the upper limit value of the drainage regulation value stipulated in the Water Pollution Control Law of 7 or more. Set to be. Moreover, it is preferable that the flow rate of the alkaline liquid sprayed from the auxiliary spraying device 23 is approximately the same as that when the condensed water is sprayed from the auxiliary spraying device 23.

  In the present embodiment, a flat plate-like member is employed as the buffer member 34 provided inside the condenser main body 31. However, the present invention is not particularly limited to such a configuration. For example, in the cross-sectional view, the condenser main body A curved member or a V-shaped member that protrudes toward the opening 35 formed in 31 may be employed.

It is a schematic block diagram which shows the concentration processing apparatus which concerns on this invention. It is AA sectional drawing of the condenser which comprises the concentration processing apparatus shown in FIG. It is a schematic block diagram which shows the conventional concentration processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concentration processing apparatus 10 Evaporator 21 Steam duct 22 Alkaline liquid spraying apparatus 23 Auxiliary spraying apparatus 30 Condenser 31 Condenser main body 32 Heat transfer pipe 33 Condensate water storage part 34 Buffer member

Claims (3)

An evaporator that generates a concentrated acid solution and an acid gas-containing vapor by evaporating and concentrating an aqueous solution containing a volatile acid solution, and a condenser that generates condensed water by condensing the introduced steam. A concentration treatment device configured to guide the acidic gas-containing vapor generated in the evaporator to a condenser through a channel,
The said flow path is a concentration processing apparatus provided with the alkaline liquid spraying apparatus which spreads an alkaline liquid, and the auxiliary spraying apparatus which recirculates and sprays the condensed water produced | generated with the said condenser at the downstream of the said alkaline liquid spraying apparatus. The condenser includes a condenser main body having an opening to which the flow path is connected, and a heat transfer tube installed inside the condenser main body,
A buffer member is provided between the opening and the heat transfer tube to prevent condensed water sprayed from the auxiliary spray device and flowing from the opening toward the heat transfer tube from directly colliding with the heat transfer tube. The concentration processing apparatus according to claim 1 . An evaporator that generates a concentrated acid solution and an acid gas-containing vapor by evaporating and concentrating an aqueous solution containing a volatile acid solution, and a condenser that generates condensed water by condensing the introduced steam. In the concentration processing apparatus configured to guide the acidic gas-containing vapor generated by the evaporator to the condenser through a channel, a neutralization method for neutralizing the acidic gas-containing vapor flowing through the flow path There,
An alkaline liquid spraying step of spraying an alkaline liquid on the acidic gas-containing steam flowing through the flow path;
A neutralization treatment method comprising: an auxiliary spraying step of refluxing and spraying the condensed water generated by the condenser at a downstream side of the alkaline liquid spraying area of the flow path .

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