JP4219319B2 - Waste liquid treatment method - Google Patents

Description

  The present invention relates to a waste liquid treatment method, and more particularly, to a waste liquid treatment method for separating a high boiling point substance and a low boiling point substance from a waste liquid containing a high boiling point substance and a low boiling point substance.

  Conventionally, in order to separate the high boiling point substance contained in the waste liquid, as shown in FIG. 3, the waste liquid W is heated by the evaporator 4 to evaporate liquids other than the high boiling point substance as the separated vapor S, thereby increasing the high boiling point. A distillation method for separating a high-boiling substance from the waste liquid W in the form of a concentrated residue L containing the substance in a concentrated state is generally known (for example, see Patent Document 1 below).

  Further, when the waste liquid W contains a low-boiling substance (highly volatile substance) together with a high-boiling substance, a neutralizing agent Z is added to the waste liquid W as shown by a broken line in FIG. By fixing the low-boiling substance and heating (distilling) the waste liquid W thereon, the low-boiling substance is prevented from being contained in the separated steam S and the separation efficiency as a whole is increased. A method for separating high-boiling substances in the form of concentrated residual liquid L is also known (see also Patent Document 1 below).

Japanese Patent Laid-Open No. 1-262981

  However, in the conventional waste liquid treatment method described above, a high boiling point substance is mixed into the separated steam S obtained by heating the waste liquid W (that is, separated steam in the distillation process) due to liquid droplets or partial evaporation. In addition, the high boiling point substance is still likely to remain at a considerable concentration in the condensate Ws of the separated steam S as the treated liquid. For this reason, the treated liquid Ws can be discharged to the outside as it is from the viewpoint of environmental conservation. However, there is a problem that a large cost is required for the post-processing (for example, industrial waste processing) of the processed liquid Ws.

  Further, in the above-described conventional method, when the low-boiling substance is contained in the waste liquid W together with the high-boiling substance, the low-boiling substance is fixed in salt to fix the low-boiling substance as a salt. There is also a problem that the necessary cost is further increased.

  In view of this situation, the main problem of the present invention is to effectively solve the above-described problems in the conventional waste liquid treatment method by adopting a rational treatment form.

[1] A first characteristic configuration of the present invention relates to a waste liquid treatment method for separating the high-boiling substance and the low-boiling substance from a waste liquid containing a high-boiling substance and a low-boiling substance.
A pre-stage distillation step for separating the waste liquid by heating into a pre-stage separation vapor containing the low-boiling substance and a pre-stage residual liquid containing the high-boiling substance in a concentrated state;
Neutralizing step of adding a neutralizing agent to the condensate of the pre-stage separation vapor obtained in this pre-stage distillation step, and converting the low boiling point substance contained in the condensate into a salt;
A second-stage distillation step in which the condensate charged with the neutralizing agent in this neutralization step is separated into a second-stage separated vapor and a second-stage residual liquid containing the residue of the high-boiling substances in the condensate in a concentrated state by heating. It is in point to include.

  That is, in the waste liquid treatment method according to the first characteristic configuration, in order to separate the high boiling point substance and the low boiling point substance from the waste liquid containing the high boiling point substance and the low boiling point substance, the waste liquid is heated in the previous distillation step. The waste liquid is separated into a first-stage separation vapor containing low-boiling substances and a first-stage residual liquid containing high-boiling substances in a concentrated state.

  In the neutralization step, the low-boiling substance contained in the condensate is fixed as a salt by introducing a neutralizing agent into the condensate of the pre-stage separation vapor obtained in the previous pre-stage distillation step. The condensed steam condensate is greatly reduced in the content of high-boiling substances by evaporative separation in the previous distillation process compared to the waste liquid before the previous distillation process. Therefore, if the method in which a neutralizing agent is added to the condensate of the first-stage separation vapor to form a low-boiling substance into a salt, the content of the waste liquid before distillation as in the conventional method is reduced. Compared to adding low-boiling substances to salt by adding a hydrating agent, the neutralizing agent prevents the reaction with high-boiling substances and reactions with other substances in the waste liquid in addition to the reaction with low-boiling substances. This effectively reduces the required amount of neutralizer. It is possible.

  In addition, high-boiling substances in the waste liquid may still remain in the condensate of the pre-separated steam because high-boiling substances in the waste liquid are mixed with the pre-separated steam due to liquid droplets or partial evaporation in the pre-stage distillation process. On the other hand, in the latter stage distillation process, the condensate into which the neutralizing agent has been added in the previous neutralization process is heated to prevent the low-boiling substances from being mixed into the separated vapor with the fixation in the previous neutralization process. The condensate is separated into a post-separation vapor and a post-stage residual liquid containing a high-boiling substance residue in the condensate in a concentrated state.

  That is, according to this method, high-boiling substances are separated by separating high-boiling substances in the former distillation process, separating high-boiling substances in the latter distillation process, and fixing low-boiling substances in the neutralization process. Both low-boiling substances and low-boiling substances can be effectively separated from the waste liquid, and the high-boiling substances and low-boiling substances are effective for the post-separation steam (or the treated liquid condensed from it) as a treated product. It is separated and removed. As described above, the required amount of neutralizing agent can also be effectively reduced, and the high-boiling substances and low-boiling substances to be separated are separated by a small amount of concentrated evaporation separation residue as in the conventional method. It can be recovered in the form of a liquid, and it is necessary for the post-treatment of the treated product (treated liquid) and the required amount of neutralizing agent compared to the conventional waste liquid treatment method. Expenses can be effectively reduced.

[2] The second characteristic configuration of the present invention specifies an embodiment suitable for the implementation of the first characteristic configuration.
The high-boiling substance and the low-boiling substance are both alkaline substances or acidic substances.

  In other words, in the conventional method of adding a neutralizing agent to the waste liquid before distillation to salt the low-boiling substance, when both the high-boiling substance and the low-boiling substance contained in the waste liquid are alkaline substances or acidic substances, Since the neutralizing agent added to fix the salt to the salt is also used for neutralizing the high boiling point substance, the necessary amount of the neutralizing agent becomes considerably large. In the waste liquid treatment method according to the characteristic configuration, the low boiling point substance is fixed by introducing the neutralizing agent into the condensate of the pre-stage separation steam in which the content of the high boiling point substance is greatly reduced. Thus, especially when both the high-boiling substance and the low-boiling substance are alkaline substances or acidic substances, the required amount of neutralizing agent can be effectively reduced as compared with the conventional method. Low boiling point substances are acidic substances Some cases or can be high boilers conversely than in a case the low boiling substance in the acidic substance is an alkaline substance, to obtain a more remarkable effect in terms of reducing the required dosage of neutralizing agent.

[3] The third characteristic configuration of the present invention specifies an embodiment suitable for the implementation of the first or second characteristic configuration.
According to the residual amount of the low boiling point substance in the post-separated steam obtained in the post-stage distillation step, the amount of the neutralizing agent input into the condensate in the neutralization step is adjusted.

  In other words, according to the third feature configuration, the amount of neutralizing agent charged is adjusted according to the residual amount of low-boiling substances in the post-separation steam, so that more neutralizer than necessary is added to the condensate in the neutralization step. Low boiling point in post-separated steam (or processed liquid condensed from it) as a processed product due to wasteful input or, conversely, the amount of neutralizing agent input to the condensate is insufficient in the neutralization process It is possible to effectively avoid the increase in the residual amount of the substance by the above adjustment, and in this respect, the waste liquid treatment is more advantageous in terms of separation of low boiling point substances and reduction of the amount of the neutralizing agent. Can be in the way.

  By the way, in order to adjust the amount of neutralizing agent to be fed to the condensate of the pre-stage separation steam in the neutralization step, the pH value of the condensate is detected and neutralized so that the detected pH value becomes a predetermined value. Although it is conceivable to adjust the input amount of the agent, compared with this, according to the above method of adjusting the input amount of the neutralizing agent according to the residual amount of the low boiling point substance in the post-separation steam, The post-separated vapor (or the processed liquid obtained by condensing it) can be more accurately brought into a desired processed state.

  In the implementation of the third characteristic configuration, in order to adjust the input amount of the neutralizing agent according to the residual amount of the low boiling point substance in the downstream separation steam, specifically, the concentration of the low boiling point substance in the downstream separation steam, etc. This method is not limited to the method of adjusting the amount of neutralizing agent input based on the detection information, but detects the low boiling point substance concentration, pH value, etc. in the condensate of the post-separation vapor, and detects the medium based on the detection information. It is also possible to adjust the amount of the additive added.

  FIG. 1 shows a waste liquid treatment apparatus according to the present invention. In this embodiment, a case where waste water W (waste liquid) discharged from equipment using hydrazine as a reducing agent is treated by a waste liquid treatment apparatus is illustrated.

Reference numeral 1 denotes a waste liquid path that guides the waste water W, and reference numeral 2 denotes a receiving tank that receives the waste water W guided by the waste liquid path 1, and this waste water W is unreacted by using hydrazine (N ₂ H ₄ ) as a reducing agent. The hydrazine discharged as it is and ammonia (NH ₃ ) generated from hydrazine by acting as a reducing agent are included.

  Hydrazine is a strong alkaline high-boiling substance having a boiling point of 113.5 ° C., whereas ammonia is an alkaline low-boiling substance having a boiling point of −33.4 ° C., but hydrazine contains hydrazine because it has strong toxicity. The waste water W is difficult to be treated by biological treatment, and as shown in FIG. 3, hydrazine as a high boiling point substance is separated from the waste water W in the form of a concentrated residual liquid L by distillation treatment of the waste water W. In the distillation treatment of the waste water W containing ammonia together with hydrazine, the low boiling point ammonia in the waste water W is sent out together with the separated steam S by evaporation, and the condensed steam W of the separated steam S (that is, treated water) For this reason, it is difficult to obtain treated water that can be discharged to satisfy the drainage standard.

  Moreover, as shown by the broken line in FIG. 3, the neutralization agent Z such as sulfuric acid is added to the waste water W to make ammonia into salt by fixing the ammonia, and then the waste water W is distilled to separate it. It is conceivable to separate the high boiling point substance hydrazine from the waste water W in the form of the concentrated residual liquid L in a state in which the low boiling point ammonia is prevented from being contained in the steam S. In the distillation process, hydrazine in the waste water W is mixed into the separated steam S due to the entrainment of liquid droplets or partial evaporation, so that a considerable amount of hydrazine is still contained in the condensed water Ws (treated water) of the separated steam S. In this respect, it is difficult to obtain treated water that can be discharged (or biologically treated), and the content of ammonia in the wastewater W is divided in order to fix ammonia as a salt. Large It was also a problem requiring a neutralizing agent Z.

  On the other hand, in this embodiment, in the waste liquid treatment apparatus shown in FIG. 1, the waste water W is made treated water that can be discharged by passing through the following treatment steps (a) to (c).

(A) Pre-stage distillation process Waste water W received in the receiving tank 2 is transferred to the pre-stage evaporator 4 by the pump P1 through the first passage 3, and the waste water W is heated to a required temperature by the heating steam H in the pre-stage evaporator 4. By heating, the waste water W is separated into a first-stage separation steam S1 containing ammonia as a low-boiling substance and a first-stage residual liquid L1 containing hydrazine as a high-boiling substance in a concentrated state.

  Then, the pre-stage separated steam S <b> 1 sent from the pre-stage evaporator 4 to the steam take-out path 5 is condensed by being cooled by the cooling water C in the pre-stage condenser 6.

  Reference numeral 7 denotes a front-stage residual liquid tank that stores the front-stage residual liquid L1 taken out from the front-stage evaporator 4 through the residual liquid take-out path 8, and the front-stage residual liquid L1 stored in the front-stage residual liquid tank 7 (in other words, a hydrazine concentrate). ) Is collected periodically and processed by industrial waste treatment.

(B) Neutralization process Condensate water Ws1 of the pre-stage separation steam S1 condensed in the pre-stage condenser 6 is received and stored in the neutralization tank 10 through the pre-stage condensate liquid path 9, and under the stirring by the stirrer 11 in the neutralization tank 10 Then, by supplying a required amount of neutralizing agent Z from the neutralizing agent tank 12 to the condensed water Ws1 of the upstream separation steam S1, the low boiling point ammonia contained in the condensed water Ws1 is fixed as a salt.

(C) Second-stage distillation step The condensed water Ws1 of the first-stage separation steam S1 charged with the neutralizing agent Z in the neutralization tank 10 is transferred from the neutralization tank 10 to the second-stage evaporator 14 by the pump P2 through the second passage 13. In the evaporator 14, the condensed water Ws 1 after charging the neutralizing agent is heated to a required temperature by the heating steam H, so that the ammonia mixture into the separated steam S 2 is prevented by fixing in the previous neutralization step. Then, the condensed water Ws1 is converted into the post-separation steam S2 and the hydrazine residue in the condensate Ws1 (that is, hydrazine mixed in the pre-separation steam S1 due to the entrainment or partial evaporation of the liquid in the pre-stage distillation step). Is separated into the latter residual liquid L2 which is contained in a concentrated state.

  Then, the latter-stage separated steam S2 sent from the latter-stage evaporator 14 to the steam extraction path 15 is condensed by cooling with the cooling water C in the latter-stage condenser 16, and the condensed water Ws2 of the latter-stage separated steam S2 is condensed to the latter-stage condensate liquid path. After being received and stored in the storage tank 18 through 17, the treated water is discharged from the storage tank 18 to the sewage.

  Reference numeral 19 denotes a rear-stage residual liquid tank that stores the rear-stage residual liquid L2 that is taken out from the rear-stage evaporator 14 through the residual liquid take-out path 20, and the rear-stage residual liquid L2 that is stored in the rear-stage residual liquid tank 19 is It is periodically collected together with the remaining liquid L1 and processed by industrial waste processing.

  That is, according to the waste liquid treatment method of the present embodiment that undergoes the treatment steps (i) to (iii) above, separation of hydrazine in the previous distillation step, separation of hydrazine residue in the subsequent distillation step, and neutralization By fixing ammonia in the process, both hydrazine, which is a high-boiling substance, and ammonia, which is a low-boiling substance, can be effectively separated from the wastewater W, and the wastewater W containing hydrazine and ammonia can be discharged with high treatment performance. Treated water Ws2.

  In addition, in order to fix ammonia, which is an alkaline low-boiling substance, as a salt, the content of strong alkaline hydrazine is greatly reduced in the condensed water Ws1 of the first-stage separated steam S1 in which the content of strong alkaline hydrazine is greatly reduced by the evaporation separation in the first-stage distillation process. Compared to adding neutralizer to waste water W before distillation to make low-boiling substance ammonia into salt, neutralizer Z is a strongly alkaline hydrazine. The necessary input amount of the neutralizing agent Z can be effectively reduced by the amount that can be spent on the reaction.

  Regarding the adjustment of the amount of the neutralizing agent Z to be introduced into the condensed water Ws1 of the preceding separation steam S1 in the neutralization step, for example, the pH value of the condensed water Ws1 is detected, and the detected pH value is a predetermined value. The amount of the neutralizing agent Z is adjusted so as to become, or the pH value in the condensed water Ws2 of the post-stage separation steam S2 as treated water is detected, and the detected pH value becomes a predetermined value. An adjustment method such as adjusting the amount of the additive Z added is adopted.

  FIG. 2 shows the treatment stages when waste water W containing hydrazine and ammonia is treated by the treatment method of the present embodiment (waste water W, condensed water Ws1 of the pre-stage separation steam S1, condensed water Ws1, charged with neutralizing agent Z, An example of pH value, BOD value, and total nitrogen in the condensed water Ws2) of the post-separation steam S2 is shown. In this example, the condensed water Ws2 of the post-separation steam S2 as treated water also has the pH value, BOD value, total It turns out that the drainage standard is fully satisfied for all of nitrogen.

[Another embodiment]
In the implementation of the waste liquid treatment method according to the first characteristic configuration of the present invention, the high boiling point substance to be separated and the low boiling point substance to be separated in the waste liquid W to be treated are not limited to hydrazine and ammonia. The waste liquid treatment method according to the first characteristic configuration can be applied to the treatment of waste liquid containing various high-boiling substances and low-boiling substances.

  Further, the waste liquid treatment method according to the first characteristic configuration of the present invention is particularly effective when both the high-boiling substance to be separated and the low-boiling substance contained in the waste liquid W to be treated are alkaline substances, or both are acidic substances. Although useful, the high-boiling substance to be separated is an alkaline substance, whereas the low-boiling substance to be separated is an acidic substance, and the high-boiling substance and the low-boiling substance react with each other. In contrast, the high boiling point substance to be separated is an acidic substance, whereas the low boiling point substance to be separated is an alkaline substance, and the high boiling point substance and the low boiling point substance are medium. It can be applied to a case where a low-boiling substance is stronger and shows alkalinity as a whole although it is a sum reaction.

  In the implementation of the waste liquid treatment method according to the first characteristic configuration of the present invention, the low-boiling substance to be separated may be any substance that forms a salt by adding the neutralizing agent Z, and the high-boiling substance to be separated is an alkaline substance. Or it may be not only an acidic substance but a neutral substance.

  The specific apparatus configuration for separating the waste liquid W into the pre-stage separation vapor S1 containing the low-boiling substances and the pre-stage residual liquid L1 containing the high-boiling substances in a concentrated state by heating in the pre-stage distillation step is the same as in the above-described embodiment. Not only the apparatus configuration shown but various configuration changes are possible.

  Further, a specific apparatus configuration for introducing the neutralizing agent Z into the condensate Ws1 of the upstream separation steam S1 in the neutralization step, and the condensate Ws1 after charging the neutralizing agent by heating in the downstream distillation step The specific apparatus configuration for separating S2 and the residual liquid L2 containing the high-boiling substance residue in the condensate in a concentrated state is not limited to the apparatus configuration shown in the above-described embodiment, but various configurations. It can be changed.

  The present invention is not limited to the treatment of wastewater containing hydrazine and ammonia, but can be applied to the treatment of various waste liquids containing high-boiling substances and low-boiling substances.

Configuration diagram of waste liquid treatment apparatus showing an embodiment Chart showing an example of each value at each processing stage Configuration diagram of waste liquid treatment equipment showing a conventional example

Explanation of symbols

W Waste liquid S1 First-stage separated steam L1 First-stage remaining liquid Ws1 First-stage separated steam condensate Z Neutralizer S2 Second-stage separated steam L2 Second-stage remaining liquid

Claims (3)

A waste liquid treatment method for separating the high boiling point substance and the low boiling point substance from a waste liquid containing a high boiling point substance and a low boiling point substance,
A pre-stage distillation step for separating the waste liquid by heating into a pre-stage separation vapor containing the low-boiling substance and a pre-stage residual liquid containing the high-boiling substance in a concentrated state;
Neutralizing step of adding a neutralizing agent to the condensate of the pre-stage separation vapor obtained in this pre-stage distillation step, and converting the low boiling point substance contained in the condensate into a salt;
A second-stage distillation step in which the condensate charged with the neutralizing agent in this neutralization step is separated into a second-stage separated vapor and a second-stage residual liquid containing the residue of the high-boiling substances in the condensate in a concentrated state by heating. Waste liquid treatment method including.   The waste liquid treatment method according to claim 1, wherein the high-boiling substance and the low-boiling substance are both alkaline substances or acidic substances. The amount of the neutralizing agent charged in the condensate in the neutralization step is adjusted according to the residual amount of the low boiling point substance in the post-separated steam obtained in the post-stage distillation step. Waste liquid treatment method.

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