JP5213699B2 - Wastewater treatment method - Google Patents

Description

  The present invention relates to a wastewater treatment method.

  Conventionally, wastewater containing organic substances such as alcohols, carboxylic acids, aldehydes and the like has been treated by a technique corresponding to each characteristic.

  In recent years, the amount of liquid organic waste, including waste water containing organic matter, has increased, and at the same time, regulations on waste are being strengthened. ing.

  In addition, from the viewpoint of “effective use of limited resources”, which is a major technical issue now, it is also necessary to reuse these wastes as resources.

  For example, as a conventional method, a method of treating organic matter-containing wastewater using ozone and hydrogen peroxide has also been proposed (Patent Document 1).

  However, this method cannot sufficiently decompose organic substances in wastewater. There is also a problem from the viewpoint of reuse of organic matter contained in wastewater as a resource.

  Therefore, a technique for purifying wastewater while adding fuel to organic matter-containing wastewater and decomposing organic matter in the wastewater to produce fuel gas has attracted attention.

  For example, in Patent Document 2, when a fuel gas is produced by hydrothermal reaction of a liquid organic substance under supercritical conditions or subcritical conditions, a reducing gas is added to the liquid organic substance and then a hydrothermal reaction is performed. A method for producing fuel gas is disclosed.

However, although the technique can prevent clogging in the treatment facility due to the polymerization and / or carbonization of organic substances in the wastewater to some extent, in order to continuously treat the wastewater for a long time, It is required to prevent blockage and the like.
JP 2003-285084 A JP 2004-352756 A

  Therefore, the present invention provides a wastewater treatment method capable of continuously treating wastewater for a long time by effectively preventing clogging and the like inside the treatment facility due to polymerization and / or carbonization of organic substances in the wastewater. The main purpose is to do.

  As a result of intensive research to achieve the above object, the present inventor has set the hydrogen addition amount within a specific range and previously mixed the organic substance-containing wastewater with hydrogen under specific conditions in the heating unit. It has been found that the above object can be achieved by heating the fluid, and the present invention has been completed.

That is, the present invention relates to the following wastewater treatment method.
1. A wastewater treatment method for converting organic matter in the wastewater into gas by reacting the wastewater containing organic matter with hydrogen in the presence of a catalyst,
The amount of hydrogen added to the organic matter-containing wastewater is 45 Nl or more per 1 mol of total organic carbon in the wastewater,
In advance, in the heating unit, in the presence of the catalyst, the mixed fluid of the organic matter-containing wastewater and hydrogen is heated,
A wastewater treatment method in which an organic substance-containing wastewater and hydrogen in the mixed fluid after heating are reacted at 215 to 370 ° C. in a hydrothermal reaction section in the presence of a catalyst.
2. Item 2. The wastewater treatment method according to Item 1, wherein the heating unit is configured to heat the mixed fluid such that the temperature of the mixed fluid exceeds 200 ° C.
3. Item 2. The wastewater treatment method according to Item 1, wherein the hydrogen partial pressure in the hydrothermal reaction section is 2.5 MPa or more.
4). Item 2. The wastewater treatment method according to Item 1, wherein the heating unit is a heat exchanger having a catalyst in the flow path of the mixed fluid.
5. Item 5. The wastewater treatment method according to Item 4, wherein heat exchange is performed between 1) the mixed fluid and 2) a gas-liquid mixed phase obtained after the reaction between the organic substance-containing wastewater and hydrogen by the heat exchanger.
6). Item 2. The wastewater treatment method according to Item 1, wherein the heating unit and the hydrothermal reaction unit constitute an integrated reactor.

According to the processing method of the present invention,
(1) The amount of organic compound deposited on the inner wall of the reactor can be reduced. As a result, according to the treatment method of the present invention, wastewater treatment can be performed continuously.
(2) The carbon dioxide concentration in the gas obtained by decomposing organic substances can be reduced. As a result, according to the treatment method of the present invention, fuel gas can be produced.

The wastewater treatment method of the present invention is a wastewater treatment method for converting organic matter in the wastewater into gas by reacting organic matter-containing wastewater with hydrogen in the presence of a catalyst,
The amount of hydrogen added to the organic matter-containing wastewater is 45 Nl or more per 1 mol of total organic carbon in the wastewater,
In advance, in the heating unit, in the presence of the catalyst, the mixed fluid of the organic matter-containing wastewater and hydrogen is heated,
In the hydrothermal reaction section, the organic substance-containing wastewater in the mixed fluid after heating and hydrogen are reacted at 215 to 370 ° C. in the presence of a catalyst.

  In the present invention, “organic matter-containing wastewater” means wastewater in which organic matter is dissolved in water or water and liquid organic matter are mixed.

  The organic matter-containing wastewater (hereinafter sometimes simply referred to as “wastewater”) is not particularly limited, and chemical factory wastewater containing organic compounds (alcohols, carboxylic acids, aldehydes, etc.), food factory wastewater, paper mill wastewater, Contains dissolved organic matter such as pharmaceutical factory wastewater, photographic wastewater, printing wastewater, agricultural chemical-related wastewater, dyeing wastewater, semiconductor manufacturing factory wastewater, wastewater generated by liquefaction or gasification of coal, and wastewater generated by thermal decomposition of municipal waste The waste water etc. which are performed are illustrated. The treatment method of the present invention can also be applied to wastewater having a high total organic carbon concentration (hereinafter abbreviated as “TOC concentration”).

  The concentration of suspended solids (hereinafter abbreviated as “SS concentration”) is not particularly limited, but is preferably 1000 mg / l or less, and more preferably 100 mg / l or less. The treatment method of the present invention is particularly effective for wastewater having an SS concentration of 100 mg / l or less.

  The waste water may contain an inorganic substance. As an inorganic substance, metals, such as Mg, Al, Si, P, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and these metal compounds are mentioned, for example.

  Although the density | concentration of the inorganic substance in the said wastewater is not specifically limited, 50 mg / l or less is preferable. If the concentration of the inorganic substance in the wastewater exceeds 50 mg / l, the catalyst used tends to deteriorate.

  As the catalyst, a catalyst having a catalyst active component supported on a carrier is preferably used. The catalytically active component is at least one selected from the group consisting of Ru, Pd, Rh, Pt, Au, Ir, Os, Fe, Cu, Zn, Ni, Co, Mn and Ce and their water-insoluble or poorly water-soluble compounds. The carrier includes at least one metal oxide selected from the group consisting of titania, zirconia, titania-zirconia, alumina, silica, alumina-silica, and activated carbon. Preferred metal active components include Ru, Pt and Ni, with Ru being particularly preferred. Preferred carriers include titania and activated carbon, with titania being particularly preferred.

  The amount of the catalytically active component supported on the carrier is usually about 0.01 to 10% by weight, more preferably about 0.1 to 3% by weight.

As a method of supporting a metal which is a catalytically active component on a support, a known method is adopted, and for example, impregnation, alkali treatment, reduction and the like can be performed in combination.
The amount of hydrogen added to the organic matter-containing wastewater is 45 Nl or more, preferably 48.5 Nl or more, more preferably 50 Nl or more, and most preferably 55 to 120 Nl with respect to 1 mol of total organic carbon in the wastewater. When the hydrogenation amount is 45 Nl or more, the wastewater treatment can be continuously performed over a long time. Moreover, since the carbon dioxide concentration of the gas finally obtained is low, the said gas can be utilized as fuel gas.

  When the amount of hydrogenation is less than 45 Nl with respect to 1 mol of total organic carbon in wastewater, the following problems (1) to (3) mainly occur.

  (1) The organic matter in the wastewater cannot be sufficiently decomposed and the wastewater cannot be purified effectively.

  (2) Since a large amount of organic compound is deposited on the inner wall of the reaction apparatus, the wastewater treatment cannot be performed continuously.

  (3) The carbon dioxide concentration of the finally obtained gas is high, and the gas cannot be effectively used as a fuel gas.

  Moreover, when the amount of hydrogen addition exceeds 120 Nl with respect to 1 mol of total organic carbon in wastewater, the TOC decomposition rate reaches almost 100%. Therefore, wasteful hydrogenation can be avoided by suppressing the hydrogenation amount to 120 Nl or less.

  In the treatment method of the present invention, the waste water and hydrogen are reacted in the presence of the catalyst in a hydrothermal reaction section.

  The reaction temperature between the wastewater and hydrogen in the hydrothermal reaction section is preferably 215 to 370 ° C, more preferably 215 to 300 ° C.

  The hydrothermal reaction section may be an apparatus, a container, or the like that suitably reacts organic substances in the wastewater with hydrogen at the reaction temperature.

  The hydrogen partial pressure in the hydrothermal reaction section is 2.5 MPa or more, preferably 3 MPa or more, more preferably 4 to 22 MPa. When the hydrogen partial pressure is 2.5 MPa or more, blockage or the like inside the processing facility can be effectively prevented. Moreover, since the carbon dioxide concentration of the gas finally obtained is low, the said gas can be utilized as fuel gas.

  Even when the hydrogen partial pressure is less than 2.5 MPa, the above problems (1) to (3) may occur.

  If the hydrogen partial pressure exceeds 22 MPa, the TOC decomposition rate reaches almost 100%. Therefore, wastewater treatment can be performed at low cost by suppressing the hydrogen partial pressure to 22 MPa or less.

  In the treatment method of the present invention, the amount of hydrogen added is 45 Nl or more with respect to 1 mol of all organic carbon in the wastewater, and the hydrogen partial pressure is 2.5 MPa or more, thereby enabling continuous wastewater treatment over a long period of time. It can be suitably performed.

  This is apparent from FIGS. 3 and 6, for example. FIG. 3 shows that the carbon deposition rate can be suppressed to 15% or less when the hydrogenation amount is 45 Nl or more with respect to 1 mol of total organic carbon in the wastewater. Further, FIG. 6 shows that when the hydrogen partial pressure is 2.5 MPa or more, the carbon deposition rate can be suppressed to 15% or less.

  Moreover, the treatment method of the present invention can maintain such suppression of the carbon deposition rate for a long time. This is apparent from FIG. 4, for example. FIG. 4 shows that the TOC decomposition rate obtained from the TOC concentration of the obtained treated water can be maintained at 98% or more even when the wastewater treatment is continuously performed for a long time.

  In the present specification, the carbon deposition ratio means the carbon ratio of the organic compound that deposits on the inner wall of the reaction apparatus based on the total amount of organic carbon in the wastewater.

  The carbon deposition ratio is derived from the carbon concentration in the gas obtained by the treatment method of the present invention from the value of the TOC decomposition rate obtained from the TOC concentration derived from the carbon concentration in the treated water obtained by the treatment method of the present invention. It can be obtained by dividing the value of the TOC decomposition rate obtained from the TOC concentration.

  In the treatment method of the present invention, the amount of hydrogen added is 45 Nl or more with respect to 1 mol of total organic carbon in the wastewater, and the hydrogen partial pressure is 2.5 MPa or more, so that the organic matter in the wastewater is carbon dioxide. It can be converted to gas with low concentration.

  In the wastewater treatment method of the present invention, prior to reacting the wastewater and hydrogen in the hydrothermal reaction section, the mixed fluid of organic matter-containing wastewater and hydrogen is heated in the presence of a catalyst in advance in the heating section. In particular, in the heating unit, the mixed fluid is heated so that the temperature of the mixed fluid exceeds 200 ° C., preferably 205 ° C. or higher. By heating so that the temperature of the mixed fluid exceeds 200 ° C., the reaction in the hydrothermal reaction section can be performed efficiently. In the treatment method of the present invention, it is desirable that the temperature of the mixed fluid when discharged from the outlet of the flow path of the mixed fluid in the heating unit is in the above range.

  The mixed fluid is heated in the heating section in the presence of a catalyst. By heating in the presence of a catalyst, organic compounds such as olefin compounds and aromatic compounds can be newly generated and effectively prevented from adhering to the inner wall of the heating part, hydrothermal reaction part or the like. In particular, in the treatment method of the present invention, in the heating unit, when the mixed fluid is heated to exceed 200 ° C., the formation of the organic compound becomes remarkable, but by providing a catalyst in the heating unit, Generation of organic compounds can be effectively suppressed. As the catalyst used in the heating section, the same catalyst as the above catalyst can be used.

  Examples of the heating unit include a heat exchanger provided with the catalyst in the flow path of the mixed fluid. A heat exchanger is a device that efficiently transfers heat from a high temperature fluid to a low temperature fluid. Examples of the heat exchanger include a multi-tube cylindrical heat exchanger, a double tube heat exchanger, and a plate heat exchanger. In particular, a double tube heat exchanger is preferable. When a double tube heat exchanger is used, the catalyst is filled on the inner tube side of the heat exchanger.

  Further, in the treatment method of the present invention, instead of using the heat exchanger, a catalyst may be filled in a line before the hydrothermal reaction section, and a coil may be wound around the outside of the line. In this case, the mixed fluid can be heated by passing an electric current through the coil.

  In addition, in the treatment method of the present invention, the heating unit and the hydrothermal reaction unit may constitute an integrated reactor. Examples of the reactor include a reactor comprising a reaction device and a tube (spiral tube) formed by spirally winding the periphery of the reaction device. The spiral tube winds all or part of the periphery of the reactor. In this case, the mixed fluid introduced into the reactor can be heated by passing the high-temperature gas-liquid mixed phase through the spiral tube. Specifically, the reactor is divided into a region for preheating the mixed fluid (heating unit) and a region for reacting the wastewater and hydrogen (hydrothermal reaction unit). The spiral tube may be used as a heating unit in the heating unit, or may be used as a heating unit in the hydrothermal reaction unit. In addition to the spiral tube, known heating means such as a heater can be used alone or in combination with the spiral tube.

  When the reactor is used, for example, the treatment method of the present invention is performed as follows. First, the mixed fluid of 200 ° C. or less is introduced from the inlet of the reactor. The mixed fluid that has passed in the vicinity of the entrance is heated by the heating unit, and the temperature thereof exceeds 200 ° C. The mixed fluid exceeding 200 ° C. is further heated in the hydrothermal reaction section, so that the temperature becomes 215 to 370 ° C., and the waste water and hydrogen are reacted.

  In the treatment method of the present invention, prior to heating by the heating unit, the mixed fluid may be heated to 100 to 200 ° C. under non-catalytic conditions. By heating the mixed fluid to 100 to 200 ° C., heating by the heating unit can be efficiently performed. Even under non-catalytic conditions, if the temperature of the mixed fluid is suppressed to 200 ° C. or lower, the formation of the organic compound can be suitably prevented. For example, the heat exchanger can be used for the heating.

  Hereinafter, the present invention will be described in detail with reference to FIG.

  FIG. 1 is a flow sheet showing an outline of an example of the method of the present invention.

  As shown in FIG. 1, the waste water stored in the storage tank 1 is sent to the reaction apparatus 10 (the hydrothermal reaction section) via the line 2, the pump 3 and the line 4. The amount of wastewater supplied is not particularly limited, and may be set as appropriate according to the scale of the treatment facility.

  The hydrogen is compressed and pressurized by the compressor 6 via the line 5 and then supplied to the waste water via the line 7. As a result, a mixed fluid containing waste water and hydrogen is obtained. The hydrogen addition amount and the hydrogen partial pressure are adjusted using the pump 3 and the compressor 6. Further, the amount of hydrogen addition can be adjusted by using a flow meter (not shown) after mixing with the compressor 6 and before mixing with waste water.

  The obtained mixed fluid is introduced through a line 8 into a heat exchanger 9 (the heating unit) in which an inner tube is filled with the catalyst. The temperature of the mixed fluid is adjusted to exceed 200 ° C. by introduction into the heat exchanger 9.

  The heat source of the heat exchanger 9 is not particularly limited, and a known heating means may be used. For example, a high-temperature gas-liquid mixed phase from the reactor 10 may be circulated and used, or a heater (not shown) may be used. In particular, it is preferable to use the high-temperature gas-liquid mixed phase from the reaction apparatus 10 as a heat source in terms of reducing wastewater treatment costs.

  The mixed fluid introduced into the heat exchanger 9 is sent to the reaction apparatus 10. In the reaction apparatus 10, the organic matter-containing wastewater in the mixed fluid sent is reacted with hydrogen in the presence of the catalyst. In particular, it is preferable that at least half of the waste water maintain a liquid phase. Thereby, waste water treatment can be performed stably. Here, “at least half of the liquid phase is maintained” is synonymous with the amount of water vapor evaporated becomes half or less of the amount of waste water. Specifically, the internal pressure at the reaction temperature, the temperature This means that the weight of water vapor determined by the relationship between the vapor pressure of water and the amount of hydrogen to be mixed does not exceed half the weight of waste water. When the water evaporates, the concentration of the components dissolved in the wastewater increases, and the components exceeding the solubility precipitate, causing problems such as clogging and catalyst poisoning. It is preferred that the proportion of water that evaporates does not exceed 50% by weight.

The reaction is preferably a hydrothermal reaction.
The hydrogen partial pressure in the reaction between the waste water and hydrogen can be confirmed by removing the water vapor pressure from the gas phase pressure in the reaction apparatus 10.

  Although reaction temperature is not specifically limited, The temperature which can perform a hydrothermal reaction efficiently, ie, 215-370 degreeC, is preferable. The reaction temperature is adjusted by using a heater (on the right side of the reaction apparatus in FIG. 1).

  The reaction time may be appropriately set according to the amount of catalyst packed, the amount of waste water to be treated, etc., but is preferably about 1 to 120 minutes, more preferably about 1 to 60 minutes.

  Although the liquid linear velocity in the reaction apparatus 10 is not specifically limited, 0.05-10 cm / sec is preferable. The liquid linear velocity is determined by the flow velocity of the liquid flowing through the reaction apparatus 10 and the dimensional diameter of the reaction apparatus 10.

  The gas-liquid mixed phase obtained by reacting the organic substance-containing wastewater with hydrogen in the reactor 10 is sent to the gas-liquid separator 14 via the line 11, the heat exchanger 9, the line 12, and the cooler 13, It separates into a gas phase (gas) and a liquid phase (treated water). In addition, what is necessary is just to provide the cooler 13 as needed.

  After separation, the gas is recovered through the pressure control valve 15. Further, the processing liquid is recovered through the liquid level control valve 16.

  Examples and Comparative Examples are shown below to further clarify the features of the present invention.

According to the flow shown in FIG. 1, waste water having a TOC concentration of 11500 mg / l (main components are shown in Table 1) was treated. The pressure in the system was set to 8.83 MPa.
Further, as the catalyst, a spherical catalyst (diameter 4 to 6 mm) formed by supporting 2% of ruthenium on the weight of the carrier on a titania carrier was used.

Example 1
Hydrogen was mixed with waste water from the storage tank 1 through a line 7. The obtained mixed fluid was introduced into the inner tube of the heat exchanger 9 filled with the catalyst and discharged from the outlet of the inner tube. At this time, the mixed fluid discharged from the outlet of the inner tube of the heat exchanger 9 by sending the gas-liquid mixed phase obtained by the hydrothermal reaction described later from the reactor 10 to the outer shell side of the heat exchanger 9. The temperature was adjusted to 205 ° C.

  While introducing the discharged mixed fluid into the reaction apparatus 10 filled with the catalyst, the reaction apparatus 10 was heated using a heater to cause a hydrothermal reaction between waste water and hydrogen at 215 ° C.

The reaction between the wastewater and hydrogen in the reactor 10 is carried out by adding a hydrogen addition amount of 58.7 Nl, a hydrogen partial pressure of 6.5 MPa, and a superficial velocity of 3.5 hr ⁻¹ (superficial volume). Standard), reaction time 17 minutes (= catalyst filling amount (m ³ ) ÷ waste water treatment amount (m ³ / hr) × 60), liquid linear velocity 0.11 cm / sec.

  The gas-liquid mixed phase after the hydrothermal reaction was sent to the gas-liquid separator 14 via the heat exchanger 9 and the cooler 13, and separated into a gas phase (gas) and a liquid phase (treated water). The obtained treated water was sampled and the TOC concentration was measured to determine the total organic carbon decomposition rate (TOC decomposition rate). The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was CH ₄ 43.8%, H ₂ 51.5%, CO ₂ 0.13% and others 4.57%.

Example 2
The temperature of the mixed fluid discharged from the outlet of the inner tube of the heat exchanger 9 is adjusted to 150 ° C. without filling the inner tube of the heat exchanger 9 with the catalyst, and the reactor 10 of FIG. Instead, waste water was produced in the same manner as in Example 1 except that a reactor and a reactor comprising a tube (spiral tube) wound around the inlet of the mixed fluid in the reactor were spirally wound. Processed.

In the reactor, the temperature of the mixed fluid is adjusted to 205 ° C. by sending the gas-liquid mixed phase to the spiral tube, and then the reactor is heated using a heater. Thus, the waste water and hydrogen were reacted hydrothermally at 215 ° C.
The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate. The same values as in Example 1 were obtained for the TOC decomposition rate obtained from the treated water and the TOC decomposition rate obtained from the gas.

  Moreover, the same result as Example 1 was obtained also about the composition of the obtained gas.

Example 3
Wastewater treatment was performed in the same manner as in Example 2 except that the amount of hydrogen added to 1 mol of total organic carbon in the wastewater was 73 Nl.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the resulting _{gas, CH 4 32.0%, H 2} 64.5%, was CO 2 0.03% and other 3.47%.

Example 4
Wastewater treatment was performed in the same manner as in Example 2 except that the amount of hydrogen added to 1 mol of total organic carbon in the wastewater was 104.3 Nl.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the resulting _{gas, CH 4 20.0%, H 2} 76.9%, was CO 2 0.03% and other 3.07%.

Example 5
Wastewater treatment was performed in the same manner as in Example 2 except that the amount of hydrogen added to 1 mol of total organic carbon in the wastewater was 48.5 Nl.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was 49.5% CH ₄ , 45.6% H ₂ , 0.23% CO ₂ and 4.7% other.

Comparative Example 1
Wastewater treatment was performed in the same manner as in Example 2 except that the amount of hydrogen added to 1 mol of total organic carbon in the wastewater was 11.7 Nl.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was 33.3% CH ₄ , 2.15% H ₂ , 60.1% CO ₂ and 4.45% other.

  FIG. 2 shows the relationship between the TOC decomposition rate determined in Examples 2 to 5 and Comparative Example 1 and the amount of hydrogen added.

  In addition, FIG. 3 shows the relationship between the carbon deposition rate and the hydrogenation amount derived by dividing the TOC decomposition rate value obtained from the gas from the TOC decomposition rate value obtained from the treated water. FIG. 3 shows that the carbon deposition rate decreases as the hydrogen addition amount increases. In particular, it can be seen that if the amount of hydrogen added to 1 mol of total organic carbon in the wastewater is 45 Nl or more, the carbon deposition rate is 15% or less.

Example 6
The same process as in Example 2 was performed except that the wastewater treatment was continuously performed for about 200 hours.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration.

  FIG. 4 shows the relationship between the TOC decomposition rate obtained from the treated water and the extended operation time.

  FIG. 4 shows that when the amount of hydrogen added to 1 mol of total organic carbon in the wastewater is 58.7 Nl, the degradation rate is hardly lowered even after 200 hours, and the wastewater can be treated continuously.

  3 and 4 show that when the amount of hydrogen added to 1 mol of total organic carbon is 58.7 Nl, the carbon deposition rate is 15% or less, and the wastewater can be treated continuously.

Comparative Example 2
It was carried out by the same method as in Comparative Example 1 except that the wastewater treatment was continuously performed for about 200 hours.

  FIG. 4 shows the relationship between the TOC decomposition rate obtained from the obtained treated water and the extended operation time.

  From FIG. 4, when the amount of hydrogen added to 1 mol of total organic carbon in the wastewater is 11.7 Nl, the decomposition rate decreases with the passage of time, so that it is difficult to continuously treat the wastewater. Recognize.

Example 7
Waste water treatment was performed in the same manner as in Example 2 except that the hydrogen partial pressure was 6.8 MPa.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was CH ₄ 45.3%, H ₂ 48.8%, CO ₂ 0.4% and others 5.5%.

Comparative Example 3
Wastewater treatment was performed in the same manner as in Example 2 except that the hydrogen partial pressure was 2.0 MPa.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was 13.3% CH ₄ , 82.3% H ₂ , 2.3% CO ₂ and 2.1% other.

Example 8
Wastewater treatment was performed in the same manner as in Example 2 except that the hydrogen partial pressure was 3.3 MPa and the hydrothermal reaction was performed at 230 ° C.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was 30.8% for CH ₄ , 61.4% for H ₂ , 3.2% for CO ₂ and 4.6% for others.

Comparative Example 4
Wastewater treatment was performed in the same manner as in Example 8 except that the hydrogen partial pressure was 0.6 MPa.

  The obtained treated water was sampled, and the TOC decomposition rate was determined by measuring the TOC concentration. The obtained gas was sampled, and the concentration of each component in the gas was measured to obtain the TOC decomposition rate.

The composition of the obtained gas was CH ₄ 6.7%, H ₂ 88.6%, CO ₂ 3.3% and others 1.4%.

  FIG. 5 shows the relationship between the TOC decomposition rate and the hydrogen partial pressure obtained in Examples 7-8 and Comparative Examples 3-4.

  FIG. 6 shows the relationship between the carbon deposition rate and the hydrogen partial pressure derived by dividing the TOC decomposition rate value obtained from the gas from the TOC decomposition rate value obtained from the treated water.

  FIG. 6 shows that if the hydrogen partial pressure is 2.5 MPa or more, the carbon deposition rate can be suppressed to 15% or less, and the wastewater can be treated continuously.

Example 9
In Example 2, the mixed fluid discharged from the outlet of the inner tube of the heat exchanger 9 was observed and analyzed.

  The mixed fluid did not appear to change in appearance compared to the waste water before treatment (hereinafter abbreviated as “raw water”).

  Moreover, the raw water and the components contained in the mixed fluid were analyzed by an infrared spectrophotometer (FT-IR). The result is shown in FIG. From FIG. 7, it can be seen that there is almost no difference in content components between the raw water and the mixed fluid.

  Further, when the mixed fluid was supplied to the reactor, a hydrothermal reaction could be performed in the reactor without any particular problem.

Comparative Example 5
Except that the temperature of the mixed fluid discharged from the outlet of the inner pipe of the heat exchanger 9 was 250 ° C. (that is, waste water and hydrogen were reacted in the absence of a catalyst), the same method as in Example 2 was used. Wastewater treatment was performed. At that time, the mixed fluid discharged from the heat exchanger 9 was observed and analyzed.

  The appearance of the mixed fluid is shown in FIG. FIG. 8 shows that the mixed fluid contains a large amount of precipitates. The components contained in the mixed fluid were analyzed by FT-IR. The result is shown in FIG. FIG. 7 shows that the mixed fluid contains an olefin compound and an aromatic compound. Further, the IR spectrum is broad as a whole, and it is considered that the IR spectrum is multi-component or contains a polymer compound. Further, the mixed fluid was analyzed by a gas chromatograph mass spectrometer (GC / MS). The result is shown in FIG. From FIG. 9, it can be seen that the mixed fluid contains a large number of aliphatic hydrocarbons and aromatic compounds.

  When the wastewater treatment was continued, the precipitates blocked the inlet portion and the outlet portion of the reactor 10, and the wastewater treatment could not be continued.

Test Example 1 (TOC concentration)
The TOC concentration was measured using TOC-V CPN (manufactured by Shimadzu Corporation).

Test Example 2 (TOC decomposition rate)
The TOC decomposition rate obtained from the treated water and the TOC decomposition rate obtained from the gas were obtained by the following formula.

TOC decomposition rate obtained from treated water = (raw water TOC concentration−treated water TOC concentration) ÷ raw water TOC concentration TOC decomposition rate obtained from gas = (raw water TOC concentration− (predicted value of treated water TOC concentration obtained by gas analysis) )) ÷ Concentration of raw water TOC Note that the “predicted value of TOC concentration of treated water obtained by gas analysis” is calculated by dividing the amount of carbon (mg) obtained from the amount of gas and the composition of the gas by the amount of treated water (l) Asked.

It is a flow sheet which shows the outline of the present invention. It is a figure which shows the relationship between the TOC decomposition | disassembly rate calculated | required in Examples 2-5 and the comparative example 1, and the amount of hydrogenation. It is a figure which shows the relationship between the carbon deposition rate derived from the TOC decomposition rate calculated | required in Examples 2-5 and Comparative Example 1, and the amount of hydrogenation. It is a figure which shows the relationship between the TOC decomposition | disassembly rate calculated | required from the treated water in Example 6 and Comparative Example 2, and total operation time. It is a figure which shows the relationship between the TOC decomposition | disassembly rate calculated | required in Examples 7-8 and Comparative Examples 3-4, and hydrogen partial pressure. It is a figure which shows the relationship between the carbon deposition rate and hydrogen partial pressure which were derived from the TOC decomposition rate calculated | required in Examples 7-8 and Comparative Examples 3-4. It is a figure which shows the FT-IR analysis result in Example 9 and Comparative Example 5. 10 is a photograph showing an appearance of a mixed fluid in Comparative Example 5. It is a figure which shows the GC / MS analysis result in the comparative example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Storage tank 2 ... Line 3 ... Pump 4 ... Line 5 ... Line 6 ... Compressor 7 ... Line 8 ... Line 9 ... Heat exchanger 10 ... Reactor 11 ... Line 12 ... Line 13 ... Cooler 14 ... Gas-liquid separation 15 ... Pressure control valve 16 ... Liquid level control valve

Claims (4)

A wastewater treatment method for converting organic matter in the wastewater into gas by reacting the wastewater containing organic matter with hydrogen in the presence of a catalyst,
The amount of hydrogen added to the organic matter-containing wastewater is 45 Nl or more per 1 mol of total organic carbon in the wastewater,
In advance, in the heating section that is a heat exchanger provided with a catalyst in the flow path of the mixed fluid of organic matter-containing wastewater and hydrogen, the mixed fluid of organic matter-containing wastewater and hydrogen is heated in the presence of the catalyst,
In the hydrothermal reaction section, in the presence of a catalyst, the organic substance-containing wastewater in the mixed fluid after heating and hydrogen are reacted at 215 to 370 ° C. ,
A wastewater treatment method in which heat exchange is performed between 1) the mixed fluid and 2) a gas-liquid mixed phase obtained after the reaction between the organic substance-containing wastewater and hydrogen by the heat exchanger . The wastewater treatment method according to claim 1, wherein the mixed fluid is heated by the heating unit such that a temperature of the mixed fluid exceeds 200 ° C. The wastewater treatment method according to claim 1, wherein a hydrogen partial pressure in the hydrothermal reaction section is 2.5 MPa or more. The wastewater treatment method according to claim 1, wherein the heating unit and the hydrothermal reaction unit constitute an integrated reactor.

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