JP2007296440A - Organic waste treatment method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an organic waste treatment method which enables a reduction in the volume of organic waste at lower temperature, and efficiently recover useful substances. <P>SOLUTION: Organic waste-containing water to be treated is supplied to a reaction tank 2 by a water to be treated supply means I. Hydrogen peroxide is supplied to the reaction tank 2 by a hydrogen peroxide supply means II to add the hydrogen peroxide to the organic waste. A heating means 14, the water to be treated supply means I, and discharge means III are controlled by using a control means 18 to regulate temperature and pressure in the reaction tank 2 so that hydrothermal reaction of the water to be treated is carried out. The reacted water is discharged from the reaction tank 2 by the discharge means III to recover the useful substances, such as acetic acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an energy resource recovery type and energy saving type organic waste processing method and an organic waste processing apparatus.

As a processing method with relatively low energy required for processing organic waste, there is a method of processing using subcritical water (300 ° C., 10 MPa) after mixing a chemical solution such as caustic soda with organic waste ( For example, see Patent Document 1).
Further, from the viewpoint of utilizing unused biomass, as a processing method for recovering useful materials in the process of treating organic waste, in the first step, the organic waste is treated at 250 ° C. under a condition in which supply of oxygen is limited. It is hydrothermally reacted at ˜350 ° C. to produce an intermediate of acetic acid, and in the second step, the intermediate of acetic acid is supplied with oxygen and hydrothermally reacted at 250 ° C. to 350 ° C. to produce acetic acid. There is a method of generating (see, for example, Patent Document 2).

JP 2002-113348 A (page 2) Japanese Patent Laying-Open No. 2003-145090 (first page)

  The conventional treatment method using hydrothermal reaction is a lower temperature than the case of using supercritical water and the energy required for heating is small, but still a lot of energy from a practical point of view. There was a problem that it was necessary.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain a method for treating organic waste capable of recovering useful substances while reducing the volume of organic waste at a lower temperature. And Moreover, it aims at obtaining the processing apparatus of organic waste.

  The organic waste processing method according to the present invention is a method in which hydrogen peroxide is added to the organic waste and a hydrothermal reaction is performed.

  By adding hydrogen peroxide to the organic waste and causing a hydrothermal reaction, the decomposition of the organic waste is promoted and not only can be decomposed at a lower temperature than before, but also the recovery rate of useful acetic acid and the like is improved.

Embodiment 1 FIG.
Conventionally, the volume of organic waste has been reduced by dissolving it in supercritical water or subcritical water and subjecting it to a reaction treatment. Increasing the treatment temperature improves the dissolution rate of organic waste and increases the volume reduction effect. However, when recovering useful materials from organic waste, the useful materials to be recovered react when the treatment temperature is high. As a result, the recovery rate of useful substances decreases.
Therefore, in the method for treating organic waste according to the embodiment of the present invention, in the treatment step, the treatment temperature is lowered by promoting a reaction involving radical species such as OH radical and O radical. Then, hydrogen peroxide, which is a generation source of the above radical species, is added to the organic waste to cause a hydrothermal reaction.

In the first embodiment of the present invention, sewage sludge that is organic waste {concentration of solids is 20000 mg / l, and the proportion of organic component (VSS) in the solids is 80%} is treated water. In a reaction tank, 0.1 to 3.5 g of hydrogen peroxide is added per 1 g of the solid matter of the sewage sludge, and in the reaction tank at 100 ° C., 200 ° C., 250 ° C. or 300 ° C., Treated by hydrothermal reaction for 30 minutes. The predetermined amount of hydrogen peroxide was added using a 35% strength aqueous hydrogen peroxide solution.
Further, the ratio of the gas phase space in the reaction tank (ratio of the gas phase space volume to the reaction tank volume in the reaction tank in which the water to be treated was sealed) was set to 50%.

FIG. 1 shows the amount of hydrogen peroxide added per gram of the solid matter (g) and the organic components in the solid matter at each treatment temperature in the organic waste treatment method of Embodiment 1 of the present invention. (VSS) The characteristic figure which shows the correlation with the ratio (VSS dissolution rate) (%) of the amount of dissolved organic components with respect to the amount, and the VSS dissolution rate is an index for reducing the volume of organic waste. Among them, a1, b1, c1, and d1 are characteristics when the processing temperatures are 100 ° C., 200 ° C., 250 ° C., and 300 ° C., respectively. In FIG. 1, the treatment at a treatment temperature of 300 ° C. and the addition amount of hydrogen peroxide of zero corresponds to a conventional hydrothermal reaction treatment using subcritical water.
As shown in FIG. 1, at each treatment temperature, by adding hydrogen peroxide to the water to be treated, the VSS dissolution rate increases, and the VSS dissolution rate increases as the amount of hydrogen peroxide added increases. The amount of hydrogen peroxide added per 1 g of the solid is saturated at 2.5 g (at 200 ° C., the VSS dissolution rate is about 80%).
In addition, when treated at 300 ° C. without adding hydrogen peroxide, which corresponds to a conventional hydrothermal reaction treatment using subcritical water, the VSS dissolution rate is about 40%, whereas the solids If the hydrogen peroxide per gram is 0.1 g, even at 100 ° C., the same VSS dissolution rate can be obtained as above, so even at a treatment temperature of 100 ° C., which is significantly lower than the conventional temperature. It can be seen that the effect of hydrogen peroxide addition is great. On the other hand, when the processing temperature exceeds 100 ° C., the VSS dissolution rate is greatly increased, and the effect of volume reduction is increased.

FIG. 2 is a graph showing the correlation between the amount of hydrogen peroxide added per gram of the solid matter (g) and the amount of acetic acid produced per gram of the solid matter (mg) at each processing temperature in the present embodiment. In FIG. 2, a <b> 2 to d <b> 2 are characteristics when the processing temperatures are 100 ° C., 200 ° C., 250 ° C., and 300 ° C., respectively.
As shown in FIG. 2, at each treatment temperature, the amount of acetic acid increased by adding hydrogen peroxide to the water to be treated, and the amount of acetic acid increased as the amount of hydrogen peroxide added increased. To do. That is, even when 0.1 g of hydrogen peroxide is added per 1 g of the above solid matter, 18 to 40 mg of acetic acid is produced per 1 g of the above solid matter at each processing temperature. When 1.5 to 2.5 g of hydrogen oxide is added, about 40 to 60 mg of acetic acid is produced, and it can be seen that the addition of hydrogen peroxide promotes the production of acetic acid by dissolving solids of sewage sludge. . On the other hand, when the amount of hydrogen peroxide added per gram of the solid exceeds 2.5 g, the tendency of the amount of acetic acid to decrease becomes remarkable, suggesting that the decomposition of the generated acetic acid becomes dominant.
In addition, when treated at 300 ° C. without adding hydrogen peroxide, which corresponds to the conventional hydrothermal reaction treatment using subcritical water, the amount of acetic acid produced per gram of the solid is about 20 mg. On the other hand, by adding 0.1 to 3 g of hydrogen peroxide per 1 g of the above-mentioned solid matter, the amount of acetic acid produced can be obtained by the treatment at 100 ° C., and the treatment temperature is much higher than before. It can be seen that the effect of hydrogen peroxide addition is large even at a low temperature of 100 ° C. In addition, when the treatment temperature exceeds 100 ° C., the amount of acetic acid produced is greatly increased.
As described above, in the present embodiment, by adding 0.1 to 3 g of hydrogen peroxide per 1 g of sewage sludge solids, at a treatment temperature lower than that of the conventional method, There is an effect that the amount of acetic acid produced can be obtained.

Embodiment 2. FIG.
In Embodiment 2 of the present invention, treated water containing sewage sludge similar to that in Embodiment 1 is sealed in a reaction tank, and 1 g of the sewage sludge solids (hereinafter simply referred to as solids) 1 g. The hydrogen peroxide was treated by hydrothermal reaction for 30 minutes at a predetermined temperature between room temperature and 360 ° C. with 0.1 g, 1.5 g or 2.5 g of hydrogen peroxide added or without hydrogen peroxide. The ratio of the gas phase space in the reaction tank (the ratio of the gas phase space volume to the volume of the reaction tank in the reaction tank in which the water to be treated was sealed) was 50%.
FIG. 3 is a characteristic diagram showing the correlation between the treatment temperature and the VSS dissolution rate (%) at the added amount of each hydrogen peroxide in the present embodiment. In the figure, e1, f1, g1, and h1 are: The characteristics are as follows: no addition of hydrogen peroxide, and addition of 0.1 g, 1.5 g, and 2.5 g. In FIG. 3, the treatment temperature of 300 ° C. and the addition amount of hydrogen peroxide of zero correspond to the conventional hydrothermal reaction treatment using subcritical water.
As shown in FIG. 3, when the treatment temperature reaches 100 ° C., the VSS dissolution rate increases abruptly with the addition amount of each hydrogen peroxide. In this case, a high dissolution rate (VSS dissolution rate is about 80% when the amount of hydrogen peroxide added per 1 g of the above solids is 2.4 g) is obtained, which is higher than that in the case where hydrogen peroxide is not added. The increase is about 2-3 times, and the effect of hydrogen peroxide addition is remarkable.
In addition, when treated at 300 ° C. without adding hydrogen peroxide, which corresponds to a hydrothermal reaction treatment using conventional subcritical water, the VSS dissolution rate is about 40%, whereas the solid solution When the hydrogen peroxide per gram of the substance is 0.1 g, even at the treatment at 100 ° C., the VSS dissolution rate similar to the conventional one can be obtained. Therefore, at 100 ° C., the treatment temperature is significantly lower than the conventional one. It can also be seen that the effect of hydrogen peroxide addition is great. On the other hand, when the processing temperature exceeds 100 ° C., the VSS dissolution rate is greatly increased, and the effect of volume reduction is increased.

FIG. 4 is a characteristic diagram showing the correlation between the treatment temperature and the amount of acetic acid produced (g) per gram of the solid matter in the amount of hydrogen peroxide added in the present embodiment. In the figure, e2, f2, g2 , H2 are characteristics in which hydrogen peroxide is not added and hydrogen peroxide is added in amounts of 0.1 g, 1.5 g, and 2.5 g, respectively.
As shown in FIG. 4, in the amount of each hydrogen peroxide added, the amount of acetic acid generated increased as the processing temperature increased. When the processing temperature was 100 to 250 ° C., the amount of each hydrogen peroxide added was 20-60 mg of acetic acid is produced per gram of the solid. In addition, as described above, acetic acid production increases with increasing processing temperature, but at any hydrogen peroxide addition amount, it shows a peak at 200 ° C., and acetic acid generation is achieved even when the processing temperature is further increased. The amount does not increase any more, and conversely, the tendency to decrease is remarkable, suggesting that the decomposition reaction of acetic acid produced by the treatment at high temperature becomes dominant.
In addition, when treated at 300 ° C. without adding hydrogen peroxide, which corresponds to a conventional hydrothermal reaction process using subcritical water, the amount of acetic acid produced is about 20 mg per 1 g of the solid. On the other hand, by setting the treatment temperature to 100 to 250 ° C., it is possible to obtain acetic acid production more than conventional by adding 0.1 g of hydrogen peroxide per 1 g of the solid matter, and the effect of hydrogen peroxide addition. It can be seen that is large. Further, as the amount of hydrogen peroxide added increases, the VSS dissolution rate increases significantly, and the effect of volume reduction increases.
As described above, in the present embodiment, in the hydrothermal reaction in which hydrogen peroxide is added, the temperature range is set to 100 ° C. to 250 ° C., which is lower than the conventional one, so There is an effect that the amount is obtained.

Embodiment 3 FIG.
In Embodiment 3 of the present invention, the water to be treated containing sewage sludge similar to that in Embodiment 1 is such that the ratio of the gas phase space in the reaction tank is a predetermined ratio between 5 and 95%. In a reaction vessel, 1.5 g of hydrogen peroxide is added per gram of the sewage sludge solid matter (hereinafter simply referred to as “solid matter”) or at 200 ° C. without adding hydrogen peroxide. For 30 minutes. Since water to be treated is introduced into the reaction tank, the gas phase space ratio does not become 100%.
FIG. 5 is a characteristic diagram showing the correlation between the ratio of the gas phase space in the reaction tank and the VSS dissolution rate of the solid matter in the present embodiment, where j1 is the hydrogen peroxide addition characteristic and k1 is This is a characteristic without hydrogen peroxide.
As shown in the characteristic j1 when hydrogen peroxide is added in FIG. 5, the VSS dissolution rate when the ratio of the gas phase space is 5% is about 10%, whereas the ratio of the gas phase space is 20%. %, The VSS dissolution rate becomes 50%, which is a much larger value than k1 when hydrogen peroxide is not added at the same gas phase space ratio, and the gas phase space ratio is 20%. By the extent, the effect on the dissolution rate of the solid matter by adding hydrogen peroxide becomes remarkable.
Furthermore, as the proportion of the gas phase space increases, the amount of oxygen and the pressure increase, so that the dissolution rate also increases. When the ratio of the gas phase space is 80%, a high dissolution rate exceeding 80% was obtained. Even if the ratio of the gas phase space was increased to 95%, no further increase in the dissolution rate was observed. In addition, the same tendency was seen when the addition amount of hydrogen peroxide was 0.1 to 3 g and the treatment temperature was 100 to 250 ° C. per 1 g of the solid matter of the sewage sludge.

FIG. 6 is a characteristic diagram showing the correlation between the gas phase space ratio and the amount of acetic acid produced (g) per gram of the solid matter in the amount of hydrogen peroxide added in the present embodiment. The characteristic k2 is a characteristic without addition of hydrogen peroxide.
As shown in FIG. 6, when hydrogen peroxide was added, the amount of acetic acid produced was about 40 mg per 1 g of the solid matter in the treatment at j2 when the ratio of the gas phase space was 20%. In addition, acetic acid production increases with an increase in the gas phase space ratio, but when the gas phase space ratio is increased to 80%, the absolute amount of water to be treated in the reaction tank decreases, resulting in an acetic acid production amount. It has been shown that the decrease in is significant.
From the above results, by making the ratio of the gas phase space 20% to 80% in the hydrothermal reaction in which hydrogen peroxide is added, a high sludge dissolution rate can be secured and the production of acetic acid can be promoted.

  About the said Embodiment 1-3, as an organic waste, the density | concentration of a solid substance is 20000 mg / l, and the experiment result which made the ratio of the organic component (VSS) in the said solid substance target 80% In the case of sewage sludge in which the solid concentration is 10,000 to 50,000 mg / l and the organic component (VSS) ratio in the solid is 70 to 100%, animal waste, food waste, etc. The same results as in the above embodiment were obtained for other organic wastes.

Embodiment 4 FIG.
FIG. 7: is a schematic block diagram of the organic waste processing apparatus of Embodiment 4 of this invention, and is an apparatus used for the processing method of Embodiment 1-3.
Water to be treated containing organic waste is stored in the waste storage tank 1, and the waste storage tank 1 and the reaction tank 2 are connected by a waste input pipe 3. The hydrogen peroxide storage tank 11 and the reaction tank 2 are connected by a hydrogen peroxide charging pipe 12, and the reaction tank 2 includes a heating device 14, a temperature measuring device 15, a pressure measuring device 16, and a water level measuring device 17. The tank 2 and the post-treatment waste storage tank 7 are connected by a waste discharge pipe 8.
The waste input pipe 3 is provided with a waste input pump 5 and a waste input valve 6, and the waste discharge pipe 8 is provided with a waste discharge pump 9 and a waste discharge valve 10. A heat exchanger 4 is provided in the waste discharge pipe 8.
By opening the waste input valve 6 and the waste discharge valve 10 and operating the waste input pump 5 and the waste discharge pump 9, the water to be treated in the waste storage tank 1 is passed through the waste input pipe 3. The treated water supply means (I) to be fed into the reaction tank 2 is processed by discharging the treated water after the reaction treatment through the waste discharge pipe 8 by the waste discharge pump 9 with the waste discharge valve 10 opened. It becomes the discharge means (III) for discharging to the post-waste storage tank 7. In this process, heat is generated between the treated water discharged from the reaction tank 2 in the heat exchanger 4 and the treated water to be charged into the reaction tank 2. Exchange.
The hydrogen peroxide supply pipe 12 is provided with a hydrogen peroxide input pump 13, and hydrogen peroxide supply means for supplying the hydrogen peroxide solution in the hydrogen peroxide storage tank 11 to the reaction tank 2 through the hydrogen peroxide input pipe 12. (II).
In the reaction tank 2, hydrogen peroxide is added to the water to be treated, heated by a heating device and retained in the reaction tank 2 for a predetermined time to cause a hydrothermal reaction.
The heating device 14, the temperature measuring device 15, the pressure measuring device 16 and the water level measuring device 17 are connected to the control device 18 by signal lines, and the temperature measuring device 15, the pressure measuring device 16 and the water level measuring device 17 are connected by the control device 18. The temperature of the water to be treated in the reaction tank 2 is adjusted by adjusting the transfer flow rate of the heating device 14, the waste input pump 5, the hydrogen peroxide input pump 13, and the waste discharge pump 9 based on the measurement value measured by The water level and pressure are adjusted to control the hydrothermal reaction conditions in the reaction tank 2.

Embodiment 5 FIG.
FIG. 8 is a schematic configuration diagram of a processing apparatus used in the organic waste processing method according to the fifth embodiment of the present invention. Solid-liquid separation is performed instead of the post-treatment waste storage tank 7 in the processing apparatus according to the fourth embodiment. Except that the device 19 is provided, the fourth embodiment is the same as the fourth embodiment.
That is, since the solid-liquid separation device 19 is provided in the processing apparatus of the present embodiment, the processed liquid can be divided into concentrated waste that is a solid component and separated liquid that is a liquid component.
The separation liquid is introduced into the separation liquid tank 20 through the separation liquid pipe 21, and a liquid component containing a large amount of valuable materials such as acetic acid obtained by hydrothermal treatment can be separated as a separation liquid, thereby efficiently collecting valuable materials. Can be done.
A part of the concentrated waste is introduced into the waste storage tank 1 through the concentrated waste pipe 22, and the remaining concentrated waste is supplied into the post-treatment waste storage tank 7 through the concentrated waste pipe 23, respectively. Decomposing organic waste can be further promoted by solid-liquid separation of the waste and hydrothermal reaction of a part of the concentrated waste again.

In Embodiment 1 of this invention, the correlation between the hydrogen peroxide addition amount (g) per gram of sewage sludge solids and the VSS dissolution rate (%) of sewage sludge solids at each treatment temperature is shown. FIG. In Embodiment 1 of the present invention, the correlation between the amount of hydrogen peroxide added per gram of sewage sludge solids (g) and the amount of acetic acid produced per gram of sewage sludge solids (mg) at each treatment temperature. FIG. In Embodiment 2 of this invention, in the addition amount of each hydrogen peroxide, it is a characteristic view which shows the correlation with the processing temperature and VSS melt | dissolution rate (%) of the solid substance of a sewage sludge. In Embodiment 2 of this invention, it is a characteristic view which shows the correlation of the acetic acid production amount (mg) per 1g of solids of a sewage sludge in the addition amount of each hydrogen peroxide. In Embodiment 3 of this invention, in the addition amount of each hydrogen peroxide, it is a characteristic view which shows the correlation with the ratio of the gaseous-phase space in a reaction tank, and the VSS dissolution rate (%) of the solid substance of a sewage sludge. In Embodiment 3 of this invention, it is a characteristic view which shows the correlation with the ratio of the gaseous-phase space in the reaction tank in the addition amount of each hydrogen peroxide, and the absolute amount of the produced | generated acetic acid. It is a schematic block diagram of the organic waste processing apparatus of Embodiment 4 of this invention. It is a schematic block diagram of the organic waste processing apparatus of Embodiment 5 of this invention.

Explanation of symbols

1 waste storage tank, 2 reaction tank, 3 waste input pipe, 5 waste input pump, 6 waste input valve, I treated water supply means, 11 hydrogen peroxide storage tank, 12 hydrogen peroxide input pipe, 13 Hydrogen peroxide charging pump, II Hydrogen peroxide supply means, 7 Waste storage tank after treatment, 8 Waste discharge piping, 9 Waste discharge pump, 10 Waste discharge valve, III Discharge means, 14 Heating device (heating means) , 15 Temperature measuring device, 16 Pressure measuring device, 17 Water level measuring device, 18 Control device (control means), 19 Solid-liquid separation device.

Claims (7)

A method for treating organic waste, in which hydrogen peroxide is added to organic waste and subjected to hydrothermal reaction. The method for treating organic waste according to claim 1, wherein 0.1 to 3 g of hydrogen peroxide is added per 1 g of solid matter of the organic waste. The method for treating organic waste according to claim 1 or 2, wherein a hydrothermal reaction is performed at 100 to 250 ° C. The gas phase space in the reaction tank in which the water to be treated containing organic waste and hydrogen peroxide is enclosed is 20 to 80%. The organic waste disposal method as described. In an organic waste treatment apparatus that hydrothermally reacts water to be treated containing organic waste in a reaction tank and collects the reaction-treated water, the water to be treated is supplied to the reaction tank. A supply means; a hydrogen peroxide supply means for supplying hydrogen peroxide to the reaction tank; a heating means for heating the reaction tank; and a discharge means for discharging the treated water or the reaction-treated water from the reaction tank. And a control means for controlling the temperature and pressure in the reaction tank by the heating means, the treated water supply means and the discharge means so that the water to be treated is hydrothermally reacted in the reaction tank. Organic waste processing equipment. 6. The organic waste treatment according to claim 5, wherein the control means controls the ratio of the gas phase space in the reaction tank in which the water to be treated is sealed by the water to be treated supply means and the discharging means. apparatus. 6. The organic waste treatment apparatus according to claim 5, further comprising solid-liquid separation means for separating the discharged reaction-treated liquid into a solid component and a liquid component.

Images