Sludge treatment system

Abstract

In a sludge treatment system that obtains carbonized sludge by carbonizing organic matter contained in fermented sludge through a hydrothermal reaction, the amount of carbonization accelerator added is appropriately controlled to improve the pH of the fermented sludge's response to the target pH and to ensure that the hydrothermal reaction proceeds appropriately. [Solution] The system includes a hydrothermal carbonization section 24 to which a carbonization accelerator A24 is added to fermented sludge S20 to carbonize the organic matter contained in the fermented sludge S20 by a hydrothermal reaction to obtain carbonized sludge S24, and a carbonization accelerator addition amount control means 50 that controls the amount of carbonization accelerator A24 added to the hydrothermal carbonization section 24 to a target amount. The carbonization accelerator addition amount control means 50 acquires measured values ​​of the state of the fermented sludge S20 and S22 before they are supplied to the hydrothermal carbonization section 24, such as a measured pH or alkalinity, a measured water content, and a measured amount of the amount supplied to the hydrothermal carbonization section, and determines the target amount to add at the time the fermented sludge S20 is supplied to the hydrothermal carbonization section 24 based on the acquired measured values.

Description

Technical Field

[0001] The present invention relates to a sludge treatment system in which fermented sludge obtained by anaerobically fermenting sludge containing organic matter in a fermentation tank is appropriately separated into a fermented sludge separation liquid in a fermented sludge solid-liquid separation section, and then the organic matter contained in the fermented sludge is carbonized by a hydrothermal reaction with the addition of a carbonization accelerator which is an acid in a hydrothermal carbonization section to obtain carbonized sludge.

Background Art

[0002] As a conventional sludge treatment system, in order to adjust the pH of the fermented sludge supplied to the hydrothermal carbonization section to a target pH suitable for the hydrothermal reaction, there is known one provided with a carbonization accelerator addition amount control means for controlling the addition amount of the carbonization accelerator in the hydrothermal carbonization section to a target addition amount (see, for example, Patent Document 1). Specifically, in the sludge treatment system described in Patent Document 1, the carbonization accelerator addition amount control means determines the target addition amount of the carbonization accelerator in the hydrothermal carbonization section at the measurement time point of the pH of the carbonized sludge based on the measured value of the pH of the carbonized sludge discharged from the hydrothermal carbonization section.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in such conventional sludge treatment systems, the residence time of the carbonized sludge from the hydrothermal carbonization section to the pH measurement point is long, for example, around 4 to 6 hours, which makes it difficult to say that the responsiveness of controlling the amount of carbonization accelerator added is high. For example, when there are changes in the properties of the fermented sludge supplied to the hydrothermal carbonization section or changes in the conditions of the hydrothermal reaction in the hydrothermal carbonization section, it is not possible to instantly adjust the amount of carbonization accelerator added to respond to these changes, which could cause the pH of the fermented sludge in the hydrothermal carbonization section to temporarily deviate from the target pH suitable for the hydrothermal reaction.

[0005] In view of these circumstances, the main objective of the present invention is to provide a technology that, in a sludge treatment system in which sludge containing organic matter generated in a water treatment facility is anaerobically fermented in a fermentation tank to obtain fermented sludge, and then in a hydrothermal carbonization section, carbonizes the organic matter contained in the fermented sludge by a hydrothermal reaction with the addition of a carbonization accelerator, which is an acid, to obtain carbonized sludge, thereby appropriately controlling the amount of carbonization accelerator added in the hydrothermal carbonization section to improve the pH of the fermented sludge to follow the target pH and to appropriately carry out the hydrothermal reaction. [Means for solving the problem]

[0006] The first characteristic configuration of the present invention is a fermentation tank to which sludge containing organic matter is supplied and the sludge is subjected to anaerobic fermentation to obtain fermented sludge, A hydrothermal carbonization section is provided in which fermented sludge obtained in the aforementioned fermentation tank is supplied, and a carbonization accelerator, which is an acid, is added to the fermented sludge to carbonize the organic matter contained in the fermented sludge by a hydrothermal reaction to obtain carbonized sludge. A sludge treatment system comprising a carbonization accelerator addition amount control means for controlling the amount of carbonization accelerator added to the hydrothermal carbonization section to a target amount, The carbonization accelerator addition amount control means acquires pH or alkalinity measurements, moisture content measurements, and supply amount measurements to the hydrothermal carbonization section as measurements of the state of the fermented sludge before it is supplied to the hydrothermal carbonization section, and determines the target addition amount at the time the fermented sludge is supplied to the hydrothermal carbonization section based on the acquired measurements.

[0007] According to this configuration, the carbonization accelerator addition amount control means, which controls the amount of carbonization accelerator added in the hydrothermal carbonization section, does not use the pH measurement of the carbonized sludge after it has been discharged from the hydrothermal carbonization section, but rather uses the pH or alkalinity measurement of the fermented sludge before it is supplied to the hydrothermal carbonization section, the water content measurement of the fermented sludge, and the amount of the fermented sludge supplied to the hydrothermal carbonization section. Based on these measurements, the target amount of additive at the time the fermented sludge is supplied to the hydrothermal carbonization section can be determined. As a result, the pH of the fermented sludge in the hydrothermal carbonization section is maintained at a target pH suitable for the hydrothermal reaction, allowing the hydrothermal reaction to proceed appropriately. Accordingly, the present invention provides a sludge treatment system in which fermented sludge obtained by anaerobic fermentation of sludge containing organic matter in a fermentation tank is carbonized by a hydrothermal reaction in a hydrothermal carbonization section with the addition of a carbonization accelerator, which is an acid, to obtain carbonized sludge. In this system, the amount of carbonization accelerator added in the hydrothermal carbonization section can be appropriately controlled to improve the pH of the fermented sludge's response to the target pH and to ensure that the hydrothermal reaction proceeds appropriately.

[0008] A second characteristic configuration of the present invention is a fermented sludge solid-liquid separation unit to which fermented sludge obtained in the fermentation tank is supplied, and fermented sludge separation liquid is separated from the fermented sludge to obtain dewatered fermented sludge, which is the fermented sludge after separation, The hydrothermal carbonization section is supplied with dewatered fermented sludge obtained in the fermented sludge solid-liquid separation section, and a carbonization accelerator, which is an acid, is added to the dewatered fermented sludge to carbonize the organic matter contained in the dewatered fermented sludge by a hydrothermal reaction. A fermented sludge state measuring unit that measures the pH or alkalinity of the fermented sludge supplied from the fermentation tank to the fermented sludge solid-liquid separation unit, The system includes a dewatered fermented sludge state measuring unit that measures the water content and supply amount of dewatered fermented sludge supplied from the fermented sludge solid-liquid separation unit to the hydrothermal carbonization unit, The carbonization accelerator addition amount control means determines the target addition amount based on the measurement results from the fermentation sludge state measurement unit and the dewatered fermentation sludge state measurement unit.

[0009] In this configuration, the liquid fermented sludge supplied from the fermentation tank to the solid-liquid separation section is not supplied directly to the hydrothermal carbonization section. Instead, the fermented sludge separation liquid is separated in the solid-liquid separation section to form a cake-like dewatered fermented sludge before it is supplied to the hydrothermal carbonization section. Therefore, in the fermented sludge state measurement section, which measures the state of the fermented sludge supplied from the fermentation tank to the solid-liquid separation section, it is not easy to measure the moisture content and supply amount of the fermented sludge supplied to the hydrothermal carbonization section because the fermented sludge is not supplied directly to the hydrothermal carbonization section. However, the pH or alkalinity of the fermented sludge can be measured easily and accurately. On the other hand, in the dewatered fermented sludge state measurement section, which measures the state of the dewatered fermented sludge supplied from the solid-liquid separation section to the hydrothermal carbonization section, it is not easy to measure the pH or alkalinity of the dewatered fermented sludge because it is cake-like. However, the moisture content and supply amount of the dewatered fermented sludge can be measured easily and accurately. Furthermore, the carbonization accelerator addition amount control means can more accurately determine the target amount of dewatered fermented sludge to be added at the time the fermented sludge and dewatered fermented sludge are supplied to the hydrothermal carbonization section, based on the pH or alkalinity of the fermented sludge and the water content and supply amount of the dewatered fermented sludge, which have been accurately measured in this manner. [Brief explanation of the drawing]

[0010] [Figure 1] Diagram showing the configuration of the sludge treatment system of this embodiment. [Modes for carrying out the invention]

[0011] An embodiment of the sludge treatment system according to the present invention will be described with reference to the drawings. The sludge treatment system 2 of this embodiment, shown in Figure 1, is configured to receive sludge S10 and S14 containing organic matter as the target for treatment, and to perform treatment on the supplied sludge S10 and S14 for volume reduction and reuse. The sludge treatment system 2 is installed in relation to a water treatment facility 1 that produces treated water X1 for treating sewage X0 and discharging it into rivers, etc., and the sewage sludge S10 and S14 produced in the water treatment facility 1 is supplied to the sludge treatment system 2 as the target for treatment.

[0012] In this embodiment, the sludge treatment system 2 treats sludge S10 and S14 originating from the water treatment facility 1. However, the sludge to be treated can be any sludge containing organic matter, and other forms of sludge may also be treated. For example, sewage sludge, agricultural community wastewater sludge, septic tank sludge, food waste such as kitchen waste (food-related biomass), lignocellulose waste such as recycled paper and waste paper, agricultural residues, and sludge containing livestock manure can be treated.

[0013] Water treatment facility 1 comprises, in order from upstream, a primary sedimentation tank 10, a biological treatment tank 12, and a final sedimentation tank 14. Specifically, incoming sewage X0 flows into the primary sedimentation tank 10, where easily sedimentable solids are settled and removed. Next, in the biological treatment tank 12, organic matter in the sewage X0 is decomposed and removed by the action of microorganisms. Finally, in the final sedimentation tank 14, activated sludge contained in the sewage X0 is settled and removed, and the purified supernatant is discharged as treated water X1. Then, the primary sludge S10, which is the sediment removed in the primary sedimentation tank 10, and the excess sludge S14, which is the sediment removed in the final sedimentation tank 14, are supplied to the sludge treatment system 2 for treatment. In addition, some of the excess sludge S14 may be returned to the biological treatment tank 12.

[0014] The sludge treatment system 2 is configured, in order from upstream, as follows: fermentation tank 20, fermentation sludge solid-liquid separation unit 22, hydrothermal carbonization unit 24, carbonized sludge solid-liquid separation unit 26, and curing tank 28.

[0015] The fermentation tank 20 is configured to receive the primary sedimentation sludge S10 and excess sludge S14 generated in the aforementioned water treatment facility 1 as the materials to be processed, and to perform a fermentation process in which the sludge S10 and S14 are subjected to anaerobic fermentation to obtain liquid fermented sludge S20, which is the residue after anaerobic fermentation of the sludge S10 and S14. Such a fermentation tank 20 is sometimes called a digester. In this fermentation tank 20, anaerobic fermentation of sludge S10 and S14 generates digester gas containing a large amount of methane, which is then used as fuel, etc. Then, the liquid fermented sludge S20 obtained in the fermentation tank 20 is discharged from the fermentation tank 20 and supplied to the fermented sludge solid-liquid separation unit 22, which will be described later. Furthermore, sludge S10 and S14 may be supplied to the fermentation tank 20 after their concentration has been increased by a concentration treatment. For the concentration treatment, known concentration devices such as gravity-type or mechanical devices such as centrifugal concentrators, atmospheric pressure flotation concentrators, and belt-type filtration concentrators may be used.

[0016] The fermented sludge solid-liquid separation unit 22 is configured to perform a fermented sludge solid-liquid separation process in which liquid fermented sludge S20 is supplied from the fermentation tank 20, and a known flocculant (not shown), such as a polymer flocculant or an iron-based inorganic flocculant, is appropriately added to separate the fermented sludge separation liquid L22 from the fermented sludge S20. As a result, the fermented sludge solid-liquid separation unit 22 yields dewatered fermented sludge S22, which is, for example, fermented sludge S20 that has been dewatered to a moisture content of about 80% by mass and has become cake-like. The fermented sludge solid-liquid separation unit 22 can be configured with various dewatering machines, such as a belt press dewatering machine, a centrifugal dewatering machine, a screw press dewatering machine, or a filter press dewatering machine. Then, the dewatered fermented sludge S22 discharged from the fermented sludge solid-liquid separation section 22 is supplied to the hydrothermal carbonization section 24, which will be described later.

[0017] The hydrothermal carbonization unit 24 is configured to perform a hydrothermal carbonization process in which the cake-like dehydrated fermented sludge S22 is supplied from the fermented sludge solid-liquid separation unit 22, and a carbonization accelerator A24, which is an acid such as sulfuric acid, hydrochloric acid, nitric acid, or organic acid, is added to carbonize the dehydrated fermented sludge S22 by a hydrothermal reaction to obtain a slurry-like carbonized sludge S24. Note that hydrothermal carbonization is a process of carbonizing a treatment object containing water (dehydrated fermented sludge S22) by performing high-temperature and high-pressure treatment in an oxygen-free atmosphere or a low-oxygen atmosphere. Then, the slurry-like carbonized sludge S24 obtained in the hydrothermal carbonization unit 24 is discharged from the hydrothermal carbonization unit 24 and supplied to a carbonized sludge solid-liquid separation unit 26 described later. The carbonization accelerator A24 is supplied by a metering pump 23 whose supply amount can be adjusted by changing the rotation speed and added to the dehydrated fermented sludge S22. The control device 50 that controls the operation of the sludge treatment system 2 functions as a carbonization accelerator addition amount control means for controlling the addition amount of the carbonization accelerator A24 in the hydrothermal carbonization unit 24 to a desired target addition amount in such a manner that the rotation speed of the metering pump 23 is controlled based on the measurement result while measuring the addition amount of the carbonization accelerator A24 to the dehydrated fermented sludge S22 by a carbonization accelerator addition amount measurement unit 56 composed of a flow meter or the like.

[0018] The carbonized sludge solid-liquid separation unit 26 is configured to perform a carbonized sludge solid-liquid separation process in which the slurry-like carbonized sludge S24 is supplied from the hydrothermal carbonization unit 24 and a carbonized sludge separation liquid L26 is separated from the carbonized sludge S24. Then, in this carbonized sludge solid-liquid separation unit 26, a dehydrated carbonized sludge S26, which is the carbonized sludge S24 dehydrated into a solid or cake shape, is obtained. Note that the carbonized sludge solid-liquid separation unit 26 can be configured by various dehydrators such as a belt press dehydrator, a centrifugal dehydrator, a screw press dehydrator, or a filter press dehydrator. Then, the solid or cake-like dehydrated carbonized sludge S26 discharged from the carbonized sludge solid-liquid separation unit 26 is supplied to a curing tank 28 described later. In addition, the carbonized sludge separation liquid L26 separated in the carbonized sludge solid-liquid separation section 26 has a high COD because the microbial cells are destroyed and the contents are eluted, so it is supplied again to the fermentation tank 20. For example, as shown by the broken line portion in FIG. 1, at least a part of the carbonized sludge separation liquid L26 may be supplied to the separation liquid settling tank 30 together with the fermentation sludge separation liquid L22 described later, or separately from the fermentation sludge separation liquid L22, or may be refluxed directly to the water treatment facility 1 or to another water treatment facility or the like.

[0019] The curing tank 28 is configured to perform a curing process in which solid or cake-like dehydrated carbonized sludge S26 is supplied from the carbonized sludge solid-liquid separation section 26, brought into contact with a curing gas containing oxygen, and the self-heat generation property is reduced to obtain stabilized carbide S28. Then, the carbide S28 obtained in the curing tank 28 is reused as a recycled fuel or the like.

[0020] In the sludge treatment system 2, when the fermentation sludge separation liquid L22 separated in the fermentation sludge solid-liquid separation section 22 is refluxed to the water treatment facility 1, a separation liquid settling tank 30 is provided to suppress an increase in COD in the water treatment facility 1. That is, the separation liquid settling tank 30 is configured to perform a separation liquid settling process in which the fermentation sludge separation liquid L22 is supplied from the fermentation sludge solid-liquid separation section 22, and a known flocculant A30 such as an iron-based inorganic flocculant is added to the fermentation sludge separation liquid L22 to perform acidic flocculation precipitation of the organic substances contained in the fermentation sludge separation liquid L22. Then, in this separation liquid settling tank 30, a supernatant liquid L30 and a precipitate S30 are obtained. The supernatant liquid L30 discharged from the separation liquid settling tank 30 is refluxed to the sewage X0 on the upstream side of the water treatment facility 1, for example, and the precipitate S30 discharged from the separation liquid settling tank 30 is returned to the fermentation tank 20, for example. Incidentally, acidic flocculation precipitation is a treatment in which the pH of the water to be treated (fermentation sludge separation liquid L22) is adjusted as necessary, an iron-based inorganic flocculant A30 is injected, and flocculation separation is performed under acidic conditions. In the separation liquid sedimentation tank 30, when adding the iron-based inorganic flocculant A30 to the fermented sludge separation liquid L22, it is desirable to also add an appropriate amount of polymer flocculant to the iron-based inorganic flocculant A30. That is, because polymer flocculants carry a negative charge in the liquid, they have the property of easily binding with particles whose charge has been neutralized by the iron-based inorganic flocculant, and can form strong flocs through cross-linking action, thus improving dewatering efficiency and flocculation treatment efficiency. Furthermore, in this embodiment, polyferric sulfate is used as the flocculant A30, but other iron-based inorganic flocculants such as ferric chloride or ferrous sulfate may also be used.

[0021] Furthermore, although this embodiment describes a configuration in which the fermented sludge separation liquid L22 returned to the water treatment facility 1 is treated in the separation liquid sedimentation tank 30, for example, as shown by the dashed line in Figure 1, at least a portion of the fermented sludge separation liquid L22 returned to the water treatment facility 1 may be returned directly to the water treatment facility 1 without being treated in the separation liquid sedimentation tank 30. Also, in this embodiment, the destination of the supernatant liquid L30 and the fermented sludge separation liquid L22 is the water treatment facility 1, which is the source of the sludge S10 and S14 that are to be treated by the sludge treatment system 2, but they may be returned to another water treatment facility or the like.

[0022] The sludge treatment system 2 of this embodiment, configured as described above, employs a configuration that appropriately controls the amount of carbonization accelerator A24 added in the hydrothermal carbonization section 24 by means of a control device 50 that functions as a means for controlling the amount of carbonization accelerator added, thereby improving the pH of the fermented sludge S20 to follow the target pH and ensuring that the hydrothermal reaction proceeds appropriately. Details of this configuration are explained below.

[0023] The control device 50 is configured to acquire measured values ​​of the state of the fermented sludge S20 and S22 before they are supplied to the hydrothermal carbonization unit 24, such as pH or alkalinity, moisture content, and the amount supplied to the hydrothermal carbonization unit 24, and to determine the target amount to be added at the time the fermented sludge S22 is supplied to the hydrothermal carbonization unit 24 based on these acquired measurements. In other words, the control device 50, which functions as a carbonization accelerator addition amount control means for controlling the amount of carbonization accelerator A24 added in the hydrothermal carbonization unit 24, does not use the pH measurement of the carbonized sludge S24 after it has been discharged from the hydrothermal carbonization unit 24, but rather uses the measured values ​​of pH or alkalinity, moisture content, and the amount supplied to the hydrothermal carbonization unit 24 of the fermented sludge S20 and S22 before they are supplied to the hydrothermal carbonization unit 24, and can determine the target amount of carbonization accelerator A24 to be added at the time the fermented sludge S22 is supplied to the hydrothermal carbonization unit 24 based on these measurements. As a result, the pH of the fermented sludge S22 in the hydrothermal carbonization section 24 is maintained at a target pH suitable for the hydrothermal reaction, allowing the hydrothermal reaction to proceed appropriately.

[0024] Specifically, the sludge treatment system 2 is equipped with a fermented sludge state measuring unit 52 that measures the pH or alkalinity of the liquid fermented sludge S20 supplied from the fermentation tank 20 to the fermented sludge solid-liquid separation unit 22, and a dewatered fermented sludge state measuring unit 54 that measures the water content and supply amount of the cake-like dewatered fermented sludge S22 supplied from the fermented sludge solid-liquid separation unit 22 to the hydrothermal carbonization unit 24.

[0025] The fermented sludge state measuring unit 52 is installed in a passage through which liquid fermented sludge S20 supplied from the fermentation tank 20 to the fermented sludge solid-liquid separation unit 22 flows, and is configured as a pH measuring device (e.g., a glass electrode pH meter) for measuring the pH of the fermented sludge S20, or as an alkalinity measuring device (e.g., a neutralization titration gravimetric alkalinity meter) for measuring the alkalinity of the fermented sludge S20. In other words, in the fermented sludge state measuring unit 52, which measures the state of the liquid fermented sludge S20 supplied from the fermentation tank 20 to the fermented sludge solid-liquid separation unit 22, the fermented sludge S20 is not supplied directly to the hydrothermal carbonization unit 24. Therefore, measuring the moisture content and supply amount of the dewatered fermented sludge S22 supplied to the hydrothermal carbonization unit 24 is not easy. However, the pH or alkalinity of the liquid fermented sludge S20 can be easily and accurately measured using the fermented sludge state measuring unit 52. In this embodiment, when measuring the pH or alkalinity of the fermented sludge S20 and S22 before they are supplied to the hydrothermal carbonization section 24, the pH or alkalinity of the liquid fermented sludge S20 is measured by a fermented sludge state measuring unit 52 installed in the passage through which the liquid fermented sludge S20 supplied from the fermentation tank 20 to the fermented sludge solid-liquid separation section 22 flows. However, the pH or alkalinity of the cake-like dewatered fermented sludge S22 supplied from the fermented sludge solid-liquid separation section 22 to the hydrothermal carbonization section 24 may also be measured.

[0026] On the other hand, the dewatered fermented sludge state measuring unit 54 is installed in a passage through which the cake-like dewatered fermented sludge S22 supplied from the fermented sludge solid-liquid separation unit 22 to the hydrothermal carbonization unit 24 flows, and is configured as a moisture content measuring device (for example, a heating-drying type or infrared type moisture meter) for measuring the moisture content of the dewatered fermented sludge S22, and a flow rate measuring device (for example, an electromagnetic type or Coriolis type flow meter, or a weight meter (load cell)) for measuring the supply amount (flow rate) of the dewatered fermented sludge S22. In other words, in the dewatered fermented sludge state measuring unit 54, which measures the state of the dewatered fermented sludge S22 supplied from the fermented sludge solid-liquid separation unit 22 to the hydrothermal carbonization unit 24, it is not easy to measure the pH and alkalinity of the dewatered fermented sludge S22 because the dewatered fermented sludge S22 is in a cake-like form, but it is possible to easily and accurately measure the water content and supply amount of the dewatered fermented sludge S22. Furthermore, although the dewatered fermented sludge state measurement unit 54 shown in Figure 1 measures the supply amount of dewatered fermented sludge S22 before the addition of carbonization accelerator A24, it is also acceptable to measure the supply amount of dewatered fermented sludge S22 after the addition of carbonization accelerator A24. Moreover, even with the configuration shown in Figure 1, the amount of carbonization accelerator A24 added is at most about 10% of the amount of solids in the dewatered fermented sludge S22. For example, if the water content of the dewatered fermented sludge S22 before the addition of carbonization accelerator A24 is 80%, the ratio of the amount of carbonization accelerator A24 added to the supply amount of dewatered fermented sludge S22 after the addition of carbonization accelerator A24 is less than 2%, so it is acceptable to ignore the amount of carbonization accelerator A24 added and consider the measured value as the supply amount of dewatered fermented sludge S22.

[0027] The measurement results from the fermentation sludge state measurement unit 52 and the dewatered fermentation sludge state measurement unit 54 are then input to the control device 50. The control device 50 functions as a carbonization accelerator addition amount control means, for example, by estimating the pH or alkalinity of the dewatered fermentation sludge S22 at the time it is supplied to the hydrothermal carbonization unit 24 from the pH or alkalinity of the fermentation sludge S20 measured by the fermentation sludge state measurement unit 52, and then more accurately determining the target amount of carbonization accelerator A24 to be added at the time the dewatered fermentation sludge S22 is supplied to the hydrothermal carbonization unit 24, based on the pH or alkalinity, water content, and supply amount of the dewatered fermentation sludge S22 to the hydrothermal carbonization unit 24.

[0028] In the above embodiment, a fermented sludge solid-liquid separation unit 22 and a carbonized sludge solid-liquid separation unit 26 are provided separately, and a configuration has been described in which solid-liquid separation of fermented sludge S20 and solid-liquid separation of carbonized sludge S24 are performed separately. However, for example, a single solid-liquid separation unit may be configured to alternately perform solid-liquid separation of fermented sludge S20 and solid-liquid separation of carbonized sludge S24. [Explanation of Symbols]

[0029] 2. Sludge Treatment System 20 fermentation tanks 22 Fermentation sludge solid-liquid separation section 24 Hydrothermal carbonization section 50 Control device (means for controlling the amount of carbonization accelerator added) 52 Fermentation sludge condition measurement unit 54 Dewatered Fermented Sludge Condition Measurement Unit A24 Carbonization accelerator L22 Fermented sludge separation liquid S10, S14 Sludge S20 Fermented Sludge S22 Dewatered fermented sludge (fermented sludge) S24 Carbonized Sludge

Claims

1. A fermentation tank is supplied with sludge containing organic matter, and the sludge is subjected to anaerobic fermentation to obtain fermented sludge. A hydrothermal carbonization section is provided in which fermented sludge obtained in the aforementioned fermentation tank is supplied, and a carbonization accelerator, which is an acid, is added to the fermented sludge to carbonize the organic matter contained in the fermented sludge by a hydrothermal reaction to obtain carbonized sludge. A sludge treatment system comprising a carbonization accelerator addition amount control means for controlling the amount of carbonization accelerator added to the hydrothermal carbonization section to a target amount, The carbonization accelerator addition amount control means acquires the pH or alkalinity, moisture content, and supply amount to the hydrothermal carbonization section as measurements of the state of the fermented sludge before it is supplied to the hydrothermal carbonization section, and determines the target addition amount at the time the fermented sludge is supplied to the hydrothermal carbonization section based on the acquired measurements. The fermented sludge obtained in the fermentation tank is supplied, and the fermented sludge solid-liquid separation unit is provided to separate the fermented sludge separation liquid from the fermented sludge to obtain dewatered fermented sludge, which is the fermented sludge after separation. The hydrothermal carbonization section is supplied with dewatered fermented sludge obtained in the fermented sludge solid-liquid separation section, and a carbonization accelerator, which is an acid, is added to the dewatered fermented sludge to carbonize the organic matter contained in the dewatered fermented sludge by a hydrothermal reaction. The system includes a dewatered fermented sludge state measuring unit that measures the water content and supply amount of dewatered fermented sludge supplied from the fermented sludge solid-liquid separation unit to the hydrothermal carbonization unit, A sludge treatment system in which the carbonization accelerator addition amount control means determines the target addition amount based on the measurement results of the dewatered fermented sludge state measurement unit.

2. The fermented sludge state measuring unit is provided for measuring the pH or alkalinity of the fermented sludge supplied from the fermentation tank to the fermented sludge solid-liquid separation unit, The sludge treatment system according to claim 1, wherein the carbonization accelerator addition amount control means determines the target addition amount based on the measurement results of the fermentation sludge state measurement unit.

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