Sludge incineration method and mixed sludge incineration system

Abstract

To provide a sludge combustion method for combusting mixed sludge in which a plurality of sludges having different properties are mixed at minimum running cost.SOLUTION: A sludge mixing and charging method for converting mixed sludge in which sludges that are combusted by an incinerator 30 and have different properties are mixed into mixed sludge that can reduce or dispense with supplementary fuel and cooling water, and charging the converted mixed sludge into the incinerator includes: determining the mixed sludge supplied to the incinerator from flow rates and pressures of the respective sludges to be mixed from a flow meter and a pressure gauge; calculating the determined flow rate values and pressure values by a calculator; determining an index of a moisture percentage; and deciding a mixed ratio of the sludges to be mixed on the basis of the index of the moisture percentage. The method includes: supplying and combusting the mixed sludge to an incinerator; and changing the mixed ratio of the sludges to be transferred to a mixer 20 and supplying the sludges to the incinerator, on the basis of a temperature in the incinerator during combustion of the mixed sludge, and minimizing supplementary fuel cost and cooling water cost required for sludge incineration.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This invention relates to a method for controlling the ratio of sludge with different properties (moisture content, heat value, etc.) when sludge with different properties (moisture content, heat value, etc.) generated during the sewage treatment process at a sewage treatment plant is mixed and incinerated in an incinerator, and to a sludge incineration system. [Background technology]

[0002] During the sewage treatment process, the solids that are separated and settled are concentrated and dehydrated, generating dehydrated sludge. Dehydrated sludge is usually incinerated, but there are two ways to incinerate it: either directly or by reducing its volume through anaerobic digestion. The latter method utilizes the methane fermentation reaction, which leads to the effective use of methane gas as an energy resource. However, digestion increases the affinity of the decomposed solid matter in the sludge with water, resulting in sludge with a high water content that is difficult to dehydrate. In large cities, there are facilities that collect sludge from each sewage treatment plant using vehicles and transport pipes, and the sludge is transported in a mixed state of high water content sludge such as digested sludge after digestion reaction and sludge with a relatively low water content that does not contain digested sludge. Therefore, in the incinerator of the collection facility, sludge with different water contents piles up in layers in the hopper that supplies the sludge to be incinerated. In addition, incinerators are equipped with multiple sludge supply pipes, and depending on the system of the sludge supply pipes, sludge that is difficult to burn and has a high moisture content and low heat value is supplied to the supply hopper, or sludge with a low moisture content and high heat value is supplied to the supply hopper.Over time, sludge with these properties mixes together, resulting in layers of sludge with different moisture contents and heat values ​​being piled up in the supply hopper. Even in sewage treatment plants that do not have centralized facilities, there is raw sludge with a high solids concentration (low moisture content, high heat generation) in the primary settling tank and excess sludge derived from microorganisms (high moisture content, low heat generation) in the final settling tank.In addition, there may be sludge that has undergone a sludge digestion process and sludge that has not, which can result in a situation where sludge with different moisture contents is piled up in layers in the incineration supply hopper. Summary of the Invention [Problem to be solved by the invention]

[0003] When sludge with different moisture contents is piled up in layers in the incineration supply hopper, combustible and non-combustible sludge are supplied to the incinerator, causing fluctuations in the combustion temperature in the incinerator. The combustion temperature is controlled by adjusting the amount of auxiliary fuel such as heavy oil or city gas supplied and by injecting cooling water into the furnace, but these must be finely adjusted to match fluctuations in the combustion temperature. If the fluctuations in the combustion temperature become too great, it can lead to unnecessary consumption of auxiliary fuel by operating the incinerator at a high combustion temperature, or to unnecessary consumption of auxiliary fuel by injecting cooling water without effectively utilizing the heat generated by the sludge.

[0004] In order to solve the above problem, the inventors have come up with a method of solving the above problem without using a moisture content meter, which involves determining whether the moisture content of multiple sludge flow paths (for example, two systems of sludge A and sludge B) is high or low by using the "relationship between sludge flow rate, sludge pressure, and moisture content" and controlling the mixing ratio of sludge A and sludge B. Figure 6 is a diagram showing the relationship between sludge flow rate and pressure value (for each moisture content), with the vertical axis representing the sludge pressure value and the horizontal axis representing the sludge flow rate value. The flow rate and pressure values ​​of six different types of sludge were measured using a flow meter and a pressure meter, and the slope (pressure ÷ flow rate) of the line connecting the minimum and maximum measured pressure values ​​is shown. Dewatered sludge is highly viscous, and its pressure changes due to frictional resistance when the sludge moves along the inner wall of the pipe through which the sludge is supplied.As shown in Figure 6, for sludge with the same moisture content, the higher the flow rate, the greater the resistance and the greater the pressure. Conversely, for sludge with the same flow rate, the lower the moisture content, the greater the resistance and the greater the pressure. Figure 7 is a diagram showing the relationship between the moisture content of sludge and the pressure gradient (slope) versus flow rate, with the vertical axis representing the slope (pressure ÷ flow rate) and the horizontal axis representing the moisture content of the sludge. As shown in FIG. 7, the larger the slope (pressure ÷ flow rate), the lower the moisture content, and the smaller the slope (pressure ÷ flow rate), the higher the moisture content. The object of the present invention is to minimize the consumption of auxiliary fuel and cooling water by utilizing the above-mentioned "relationship between sludge flow rate, sludge pressure, and moisture content" to mix sludge with different properties in a mixer, feed the mixed sludge (hereinafter, mixed sludge K) into an incinerator, and adjust the amount of sludge with different properties transferred to the mixer based on the internal temperature of the incinerator. [Means for solving the problem]

[0005] In order to achieve the above object, the present inventors have solved the above problems by the following means. [1] A sludge incineration method in which mixed sludge K, which is a mixture of sludges with different properties, is converted into mixed sludge that can reduce or does not require auxiliary fuel and cooling water, and is then put into an incinerator and incinerated, a furnace temperature control step of supplying the mixed sludge to an incinerator and burning the mixed sludge, and controlling the furnace temperature by adjusting the supply amount of auxiliary fuel and cooling water based on the furnace temperature in the incinerator during the combustion of the mixed sludge; a sludge mixing ratio control step of determining the flow rate and pressure of each sludge from a flow meter and a pressure meter, calculating the determined flow rate and pressure values ​​with a calculator to determine an index of moisture content, determining a mixing ratio of the sludge to be mixed using the determined index, and mixing the sludge based on the determined mixing ratio; A sludge flow rate control step for adjusting the mixing ratio of the mixed sludge supplied to the incinerator in response to the sludge mixing ratio control step; A sludge incineration method comprising the steps of:

[0006] [2] A plurality of storage hoppers for storing a plurality of sludges having different properties, a plurality of transfer pumps for transferring the sludge to a mixer (20), a flow meter for measuring the flow rate of the sludge and a pressure meter for measuring the pressure of the sludge, which are provided in the middle of a pipe connected to the transfer pumps and the mixer (20), at least one or more supply hoppers (21) for storing mixed sludge K obtained by mixing the sludges by the mixer (20) and supplying the mixed sludge K to an incinerator (30), and a transfer pump (23) provided in the supply hopper (21); an incinerator (30) provided with an incinerator thermometer (31); a cooling water supply device (32) for supplying cooling water into the incinerator (30); and a cooling water flow meter (34) and a cooling water regulating valve (35) provided midway in a pipe (33) connected between the cooling water supply device (32) and the incinerator (30); an auxiliary fuel supply device (42) for supplying auxiliary fuel into the incinerator (30), an auxiliary fuel flow meter (44) and an auxiliary fuel regulating valve (45) provided midway through a pipe (43) connected between the auxiliary fuel supply device (42) and the incinerator (30); a calculator (50) for calculating a water content index by calculating values ​​measured by a flowmeter for measuring a flow rate of the sludge and a pressure gauge for measuring a pressure of the sludge, the flowmeter and the pressure gauge being provided in a pipe connected to the mixer (20); a control device (60) for adjusting the supply amount by the sludge transfer pumps provided at the plurality of storage hoppers using an index of moisture content from a calculator (50), and for adjusting the supply amount of cooling water and auxiliary fuel by the cooling water regulating valve (35) and the auxiliary fuel regulating valve (45) based on the in-furnace temperature measured by the in-furnace thermometer (31).

[0007] [3] A plurality of storage hoppers for storing a plurality of sludges having different properties, a plurality of transfer pumps for transferring the sludge to a mixer (20), a flow meter for measuring the flow rate of the sludge and a pressure meter for measuring the pressure of the sludge, which are provided in the middle of the pipes connected to the transfer pumps and the mixer (20), an in-furnace thermometer (31) provided in the incinerator (30), a cooling water supply device (32) for supplying cooling water into the incinerator (30), a cooling water flow meter (34) and a cooling water regulating valve (35) provided in the middle of the pipes (33) connected to the cooling water supply device (32) and the incinerator (30), an auxiliary fuel supply device (42) for supplying auxiliary fuel into the incinerator (30), an auxiliary fuel flow meter (44) and an auxiliary fuel regulating valve (45) provided midway through a pipe (43) connected between the auxiliary fuel supply device (42) and the incinerator (30); a calculator (50) for calculating a water content index by calculating measured values ​​of a flowmeter for measuring a flow rate of the sludge and a pressure gauge for measuring a pressure of the sludge, the flowmeter and the pressure gauge being provided in a pipe connected to the mixer (20); a control device (60) for adjusting the supply amount by the sludge transfer pumps provided in the plurality of storage hoppers based on the moisture content from a calculator (50), and for adjusting the supply amount of cooling water and auxiliary fuel by the cooling water regulating valve (35) and the auxiliary fuel regulating valve (45) based on the in-furnace temperature measured by the in-furnace thermometer (31). Effect of the Invention

[0008] According to the present invention, the mixing ratio of mixed sludge can be appropriately controlled, so that sludge with different properties can be burned while minimizing the consumption of auxiliary fuel and cooling water. [Brief description of the drawings]

[0009] [Figure 1] A schematic diagram showing a first embodiment of the present invention. [Diagram 2] Flowchart of furnace temperature control in the first embodiment [Diagram 3] Flowchart of sludge mixing ratio control in the first embodiment [Figure 4] Flowchart of sludge mixing ratio control in the first embodiment [Diagram 5] FIG. 2 is a schematic diagram showing a second embodiment of the present invention. [Figure 6] A diagram showing the relationship between sludge flow rate and pressure (for each moisture content) [Figure 7] A diagram showing the relationship between the moisture content of sludge and the pressure gradient (inclination) versus the flow rate DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0011] FIG. 1 is a schematic diagram showing a first embodiment of the present invention. The first embodiment includes a first storage hopper 1 for storing sludge A, a sludge discharger 2 for discharging the sludge A in the first storage hopper 1, a transfer pump 3 for supplying the sludge A, a second storage hopper 11 for storing sludge B having properties different from the sludge A, a sludge discharger 12 for discharging the sludge B in the second storage hopper 11, and a transfer pump 13 for supplying the sludge B. The incinerator is equipped with a mixer 20 that mixes sludge A and sludge B supplied by the transfer pump 3 and transfer pump 13, a supply hopper 21 that stores the mixed sludge K supplied from the mixer 20 and supplies it to the incinerator, a sludge discharger 22 that discharges the mixed sludge K in the supply hopper 21, and a transfer pump 23 that supplies the mixed sludge K. In this embodiment, the sludge A and B with different properties are respectively supplied through the routes, but in reality, the sludge properties such as the water content and heat generation amount change over time in each supply route, and it should be noted that the properties of the sludge supplied through each supply route are not necessarily different. A flowmeter 5 for measuring the sludge flow rate and a pressure gauge 6 for measuring the sludge pressure are provided in the middle of the pipe 4 connected to the transfer pump 3 and the mixer 20, and a flowmeter 15 for measuring the sludge flow rate and a pressure gauge 16 for measuring the sludge pressure are provided in the middle of the pipe 14 connected to the transfer pump 13 and the mixer 20. Even for sludge with the same properties, the pressure value varies due to differences in pressure loss depending on the installation position of the pressure gauge. Therefore, in this example, it is desirable to install the pressure gauges in the supply routes of sludge A and sludge B at positions where the pressure loss values ​​of the supply routes are equal. The above constitutes a sludge flow rate control system that supplies mixed sludge K to the incinerator 30.

[0012] The incinerator 30 is provided with an in-furnace thermometer 31 for measuring the temperature inside the furnace. In addition, a cooling water supply system for cooling the inside of the furnace according to the temperature inside the furnace where the sludge is burned, and an auxiliary fuel supply system for adjusting the temperature inside the furnace are provided. The cooling water supply system includes a cooling water supply device 32 that supplies cooling water into the incinerator 30, and a cooling water flow meter 34 and a cooling water adjustment valve 35 are provided in the middle of piping 33 connected between the cooling water supply device 32 and the incinerator 30. The auxiliary fuel supply system includes an auxiliary fuel supply device 42 that supplies auxiliary fuel into the incinerator 30, and an auxiliary fuel flow meter 44 and an auxiliary fuel regulating valve 45 provided in the middle of piping 43 that connects the auxiliary fuel supply device 42 to the incinerator 30.

[0013] In the schematic configuration diagram showing the first embodiment of the present invention, a control device 60 and a computing unit 50 are provided. The calculator 50 receives the flow rate and pressure values ​​of sludge A (sludge B) measured by the flow meter 5 (15) and pressure gauge 6 (16), and uses the flow rate and pressure values ​​to calculate an index of the moisture content of sludge A (sludge B). In the present invention, the moisture content index is a value obtained by calculating the flow rate and pressure of the sludge measured by a flowmeter and a pressure gauge using calculator 50 (pressure value÷flow rate value). The control device 60 is, for example, a PLC (Programmable Logic Controller) and operates based on a control program executed by the PLC. The control device 60 receives signals from various in-furnace sensors (furnace thermometer, cooling water flow meter, auxiliary fuel flow meter) and the calculator 50, and sends control signals corresponding to the received signals to various devices (cooling water regulating valve, auxiliary fuel regulating valve, inverter drive motors 7 and 17 (hereinafter referred to as motors) according to a built-in control program to control the various devices. In FIG. 1, dashed lines with arrows indicate signal lines for transmitting control signals from the control device 60 to the cooling water regulating valve 35, the auxiliary fuel regulating valve 45 and the motors 7 and 17. For example, the control device 60 receives the furnace temperature value from the furnace thermometer 31, and sends an opening command signal to the cooling water regulating valve 35 based on the furnace temperature value to adjust the opening of the cooling water regulating valve 35. Alternatively, the control circuit 30 receives a temperature value from the furnace thermometer 31 and sends an opening command signal to the auxiliary fuel regulating valve 45 based on the furnace temperature value, thereby adjusting the opening of the auxiliary fuel regulating valve 45 .

[0014] A method of supplying mixed sludge K to an incinerator according to the first embodiment will be described. The dewatered sludge A generated in the sewage treatment process of a sewage treatment plant is transferred from a first storage hopper 1 in which the sludge A is stored to a mixer 20 by a sludge discharger 2 and a transfer pump 3 . At this time, the flow rate and pressure of sludge A are measured by a flowmeter 5 for measuring the sludge flow rate and a pressure gauge 6 for measuring the pressure, which are installed in the piping 4 connected to the transfer pump 3 and the mixer 20, and each measurement value is sent to the calculation device 50, where an indicator of the moisture content of sludge A is calculated. Meanwhile, the dewatered sludge B generated in the sewage treatment process of the sewage treatment plant is transferred from a second storage hopper 11 in which the sludge B is stored to a mixer 20 by a sludge discharger 12 and a transfer pump 13 . At this time, the flow rate and pressure of sludge B are measured by a flowmeter 15 for measuring the sludge flow rate and a pressure gauge 16 for measuring the pressure, which are installed in a pipe 14 connected to the transfer pump 13 and the mixer 20, and the respective measured values ​​are sent to a calculation device 50, where an indicator of the moisture content of sludge B is calculated. At this time, the flow rate and pressure of sludge A and sludge B are measured using the flow meters (5, 15) and pressure gauges (6, 16), and the measured values ​​are output to calculator 50, which performs a calculation (pressure value ÷ flow rate value).Using the obtained moisture content index, sludge A and sludge B are mixed without taking into account the moisture content of the sludge to produce mixed sludge K.In contrast to the conventional method, in which sludge A and sludge B are mixed to produce mixed sludge K without taking into account the moisture content of the sludge, sludge A and sludge B are transported to mixer 20 in a ratio of A to B to produce mixed sludge K, and sludge A and sludge B are mixed in mixer 20 to homogenize the mixed sludge K. Then, the mixed sludge K is transferred from the mixer 20 to a supply hopper 21 where it is stored, and is then supplied from the supply hopper 21 to an incinerator 30.

[0015] In explaining the method of transporting sludge A and sludge B to mixer 20 in a ratio of sludge A and sludge B to produce a mixed sludge that does not require auxiliary fuel and cooling water, and mixing sludge A and sludge B in mixer 20 to homogenize the mixed sludge K, first, the control of the incinerator temperature will be explained using Figure 2, which is a control flowchart for controlling the incinerator temperature due to the incineration of mixed sludge K supplied to incinerator 30. Step 1 (S1) It is judged whether the furnace temperature (Ti) is lower than the set temperature value (TiSV). Step 2 (S2) If the furnace temperature (Ti) is lower than the set temperature value (TiSV), it is decided to increase Ti. Step 3 (S3) In order to raise the incinerator temperature (Ti), the opening of the auxiliary fuel regulating valve 45 is increased to increase the amount of auxiliary fuel supplied to the incinerator, and the opening of the cooling water regulating valve 35 is reduced to decrease the amount of cooling water sprayed into the incinerator. Step 4 (S4) When the furnace temperature (Ti) is higher than the set temperature value (TiSV), it is determined that Ti should be decreased. Step 5 (S5) In order to lower the incinerator temperature (Ti), the opening of the auxiliary fuel regulating valve 45 is reduced to reduce the amount of auxiliary fuel supplied to the incinerator, and the opening of the cooling water regulating valve 35 is increased to increase the amount of cooling water sprayed into the incinerator. The above is the basic control of the furnace temperature according to the present invention, which is performed by adjusting the amount of auxiliary fuel and the amount of cooling water.

[0016] Next, using Figure 3, which is a sludge mixing ratio control flowchart for controlling the sludge mixing ratio of sludge A and sludge B when the mixed sludge K supplied to the incinerator 30 is incinerated and the temperature inside the furnace is controlled by using auxiliary fuel and cooling water, we will explain the control of the flow rate (supply amount) of sludge A or sludge B that constitutes the mixed sludge K supplied into the furnace. Step 1 (S1) The measurement value of the auxiliary fuel supply amount Ff is checked to determine whether auxiliary fuel is being supplied within the incinerator. Step 2 (S2) When auxiliary fuel is used in the incinerator, it is determined whether the moisture content index of sludge A calculated by the calculator 50 (measurement value Pa of the pressure gauge 6 ÷ measurement value Fa of the flow meter 5) is smaller than the moisture content index of sludge B also calculated by the calculator 50 (measurement value Pb of the pressure gauge 16 ÷ measurement value Fb of the flow meter 15). Step 3 (S3) If the moisture content index of sludge A is small in S2, reduce the set value of the flow rate of sludge A and proceed to *1A. S6 is also performed at the same time. Step 4 (S4) If auxiliary fuel is not being used in the incinerator, check the measured value of the cooling water supply amount Fc to determine whether cooling water is being used. Step 5 (S5) When cooling water is used in the incinerator, it is determined whether the moisture content index of sludge A calculated by the calculator 50 (Pa÷Fa) is greater than the moisture content index of sludge B (Pb÷Fb). Step 6 (S6) If the moisture content index of sludge B is small in S5, increase the set value of the flow rate of sludge B and proceed to *1B. Also perform S3 at the same time. Step 7 (S7) In S2, if the moisture content index of sludge A is large, increase the set value of the flow rate of sludge A and proceed to *1A. Also perform S8 at the same time. Step 8 (S8) In S5, if the moisture content index of sludge B is large, the set value of the flow rate of sludge B is reduced and proceed to *1B. S7 is also performed at the same time. Step 9 (S9) If cooling water is not being used in the incinerator, the control ends.

[0017] The above describes how the temperature inside the furnace is controlled by controlling the amount of sludge A and sludge B supplied to the furnace depending on the usage of cooling water and auxiliary fuel inside the furnace.The basic idea behind this invention is as follows. 1) Compare the calculated values ​​of "Pressure gauge A measurement value ÷ Flow meter A measurement value (excluding)" and "Pressure gauge B measurement value ÷ Flow meter B measurement value (excluding)" to determine which system, A or B, has a larger or smaller moisture content index per hour, [1] If the incinerator uses auxiliary fuel Reduce the amount of sludge in systems with a small "pressure gauge measurement value ÷ flow meter measurement value (excluding)" (i.e., systems with a high moisture content), and increase the amount of sludge in systems with a large "moisture content index" (i.e., systems with a low moisture content). [2] If the incinerator uses cooling water Reduce the amount of sludge in systems with a large "pressure gauge measurement value ÷ flow meter measurement value (excluding)" (an index of moisture content), i.e., systems with a low moisture content, and increase the amount of sludge in systems with a small moisture content (small index of moisture content), i.e., systems with a high moisture content. The amount of operation for changing the mixture ratio at this time is determined according to the usage status of the cooling water or auxiliary fuel.

[0018] Next, using Figure 4, which is a control flowchart of the sludge flow rate (1A, 1B) obtained by controlling the sludge mixing ratio of sludge A and sludge B, we will explain the control of the supply amount (flow rate) of the flow rate (Fa) of sludge A and the flow rate (Fb) of sludge B. Step 1 (S1) Following *1A from the sludge mixing ratio control, the increased or decreased sludge flow rate setting value FaSV value is input. Step 2 (S2) It is determined whether the flow rate Fa of sludge A is less than the flow rate set value FaSV. Step 3 (S3) When the flow rate Fa of the sludge A is less than the flow rate set value FaSV, the rotation speed of the motor 7 of the transfer pump 3 is increased to increase the sludge flow rate Fa. Step 4 (S4) When the flow rate Fa of the sludge A is greater than the flow rate set value FaSV, the rotation speed of the motor 7 of the transfer pump 3 is reduced to decrease the sludge flow rate Fa. Step 5 (S5) Following *1B from the sludge mixing ratio control, the increased or decreased sludge flow rate set value FbSV value is input. Step 6 (S6) It is determined whether the flow rate Fb of sludge B is less than the flow rate set value FbSV. Step 7 (S7) When the flow rate Fb of the sludge B is less than the flow rate set value FbSV, the rotation speed of the motor 17 of the transfer pump 13 is increased to increase the sludge flow rate Fb. Step 8 (S8) When the flow rate Fb of the sludge B is greater than the flow rate set value FbSV, the rotation speed of the motor 17 of the transfer pump 13 is reduced to decrease the sludge flow rate Fb.

[0019] Based on the above-mentioned controls, a method for incinerating sludge (mixed sludge K) will be described. As described above, sludge A and sludge B are transported to the mixer 20 at a mixing ratio (the ratio of sludge A to sludge B that results in a mixed sludge that does not use auxiliary fuel and cooling water) set based on the respective "pressure gauge measurement value ÷ flow meter measurement value (removed)" (an index of moisture content), and the mixed mixed sludge K is transported to and stored in the supply hopper 21. The stored mixed sludge K is supplied from the supply hopper 21 to the incinerator and incinerated. Here, the incinerator temperature in which the mixed sludge K is burned is measured by an incinerator thermometer 31, and as necessary, cooling water is sprayed into the incinerator to adjust the incinerator temperature, or auxiliary fuel is supplied into the incinerator to adjust the temperature, thereby controlling the incinerator temperature to be maintained at the set value. In addition to the above temperature control, based on the cooling water and auxiliary fuel supplied into the furnace, when the temperature inside the furnace is high, a large amount of sludge with a high moisture content (i.e., a large amount of moisture) is supplied, and when the temperature inside the furnace is low, a large amount of sludge with a low moisture content (i.e., a small amount of moisture) is supplied, thereby controlling the use of auxiliary fuel and cooling water as much as possible to maintain the set furnace temperature. [Table 1]

[0020] Table 1 shows an example of the daily costs for incinerating sludge A, which has a high percentage of sludge that does not go through the digestion process, followed by sludge B, which has a high percentage of sludge that goes through the digestion process, or vice versa, and for supplying sludge A and sludge B to the incinerator at the same time and incinerating them. As an example, the costs of incinerating 30 tons of sludge A and 20 tons of sludge B per day, totaling 50 tons, are compared. This explains the cost required to incinerate 30 tons of sludge A when sludge A and sludge B are incinerated in that order. Since sludge A has not undergone a digestion process, the organic matter has not been broken down through anaerobic digestion reactions, and it generates a lot of heat, requiring cooling water to raise the temperature inside the incinerator. If treated water from a sewage treatment plant is used as the cooling water, the cooling water cost will be 71 yen. If tap water is used as the cooling water, the cooling water cost will be 2,848 yen. The cost of incinerating 20 tons of sludge B will be 71,506 yen in supplementary fuel (city gas) costs. In this way, the cost required to incinerate a total of 50 tons of sludge A and 50 tons of sludge B separately in sequence is 71,577 yen if treated water is used as cooling water, and 74,354 yen if tap water is used as cooling water. In contrast, the cost required to incinerate 50 tons of mixed sludge made by mixing sludge A and sludge B can be reduced by reducing the amount of auxiliary fuel and cooling water used (no cooling water is required), and the cost of auxiliary fuel (city gas) will be 6,632 yen. In this way, mixing sludge A and sludge B and incinerating the mixed sludge while taking into account the influence of the moisture content of each sludge reduces the amount of cooling water and auxiliary fuel used and is by far less costly than incinerating sludge A and sludge B separately. Note that while the above explanation has been given as an example of a case in which sludge A and sludge B are supplied to the incinerator, the present invention is not limited to this and can be applied to a case in which there are multiple supply paths.

[0021] FIG. 5 is a schematic diagram showing a second embodiment of the present invention. The second embodiment will be described with reference to FIG. In this embodiment, only the differences from the first embodiment will be explained. The flow rate and moisture content of dewatered sludge A and sludge B generated from the sewage treatment process at a sewage treatment plant are measured, and the measured values ​​are output to a calculator 50, which performs a calculation (pressure value ÷ flow rate value) and transfers the sludge A and sludge B to a mixer 20 in a ratio such that a mixed sludge that does not use auxiliary fuel and cooling water is produced. Sludge A and sludge B are mixed in the mixer 20 to homogenize the mixed sludge K. Then, the mixed sludge K is supplied from the mixer 20 to the incinerator 30. Thereafter, basic control of the temperature inside the furnace, control of the sludge mixing ratio, and control of the sludge flow rate determined by the sludge mixing ratio control are performed. This embodiment is different in that no supply hopper is provided and mixed sludge K is supplied from a mixer 20 to an incinerator 30. In the first embodiment, the amount of moisture supplied to the incinerator can be adjusted by adjusting the supply amount by the transfer pump 23 in addition to adjusting the supply amount by the transfer pumps 3 and 13. As in the second embodiment, it is sufficient to tolerate temperature fluctuations in the furnace only by adjusting the supply amount by the transfer pumps 3 and 13, but the heat generation amount of the sludge may vary, which may lead to fluctuations in the temperature in the furnace. In that case, as in the first embodiment, the supply amount can be adjusted by the sludge transfer pump 23 according to the temperature fluctuation in the furnace by the amount stored in the supply hopper 21. In the above explanation, a case where sludge A and sludge B are supplied to the incinerator is exemplified, but the present invention is not limited to this and can be applied to a case where there are multiple supply paths.

[0022] Up to this point, the moisture content index values ​​of a plurality of supply paths are relatively compared using the moisture content index calculated by dividing the pressure value by the flow rate value, and the application of sludge flow rate control for each supply path has been shown. However, the embodiment is not limited to the moisture content index. In Figure 7, the moisture content index is nothing but the expected moisture content. In other words, the product of the sludge flow rate and the moisture content index (expected moisture content) can be calculated as the expected moisture content per unit time, and can be applied as the expected moisture content for each supply route, just like the moisture content for each supply route. Moisture content meters used in the sludge incineration process are expensive and require sufficient maintenance to ensure measurement accuracy. In contrast, stable combustion operation of the sludge incinerator can be expected by adopting a pressure gauge that is inexpensive, has stable measurement accuracy, and requires relatively little maintenance. The moisture amounts of sludge A and sludge B collected in the control device (60) can also be used to adjust the moisture content in a dehydration facility that precedes the incineration process. By adjusting the dehydration capacity of the dehydration facility according to the moisture amount and adjusting the total moisture amount (the sum of the estimated moisture amounts for each supply route) within a predetermined range, it is possible to suppress fluctuations in the temperature inside the incineration furnace. [Explanation of symbols]

[0023] 1: First storage hopper 11: Second storage hopper 2, 12, 22: Sludge discharger 3, 13, 23: Transfer pump 4, 14: Piping 5, 15: Flowmeter 6, 16: Pressure gauge 20: Mixer 21: Supply hopper 30: Incinerator 31:Furnace thermometer 32: Cooling water supply device 33: Piping 34: Cooling water flow meter 35: Cooling water regulating valve 42:Auxiliary fuel supply device 43: Piping 44: Auxiliary fuel flow meter 45: Auxiliary fuel control valve 50: Arithmetic unit 60: Control device

Claims

1. A sludge incineration method in which mixed sludge K, which is a mixture of sludges with different properties, is converted into mixed sludge that can reduce or does not require auxiliary fuel and cooling water, and is then put into an incinerator and incinerated, a furnace temperature control step of supplying the mixed sludge to an incinerator and burning the mixed sludge, and controlling the furnace temperature by adjusting the supply amount of auxiliary fuel and cooling water based on the furnace temperature in the incinerator during the combustion of the mixed sludge; a sludge mixing ratio control step of determining the flow rate and pressure of each sludge from a flow meter and a pressure meter, calculating the determined flow rate and pressure values ​​with a calculator to determine an index of moisture content, determining a mixing ratio of the sludge to be mixed using the determined index, and mixing the sludge based on the determined mixing ratio; A sludge flow rate control step for adjusting the mixing ratio of the mixed sludge supplied to the incinerator in response to the sludge mixing ratio control step; A sludge incineration method comprising the steps of:

2. a plurality of storage hoppers for storing a plurality of sludges having different properties; a plurality of transfer pumps for transferring the sludge to a mixer (20); a flow meter for measuring the flow rate of the sludge and a pressure meter for measuring the pressure of the sludge, which are provided in the middle of a pipe connected to the transfer pumps and the mixer (20); at least one or more supply hoppers (21) for storing mixed sludge K obtained by mixing the sludges by the mixer (20) and supplying the mixed sludge K to an incinerator (30), and a transfer pump (23) provided in the supply hopper (21); An incinerator (30) is provided with an in-furnace thermometer (31), a cooling water supply device (32) that supplies cooling water into the incinerator (30), and a cooling water flow meter (34) and a cooling water adjustment valve (35) that are provided midway in a pipe (33) that is connected between the cooling water supply device (32) and the incinerator (30); an auxiliary fuel supply device (42) for supplying auxiliary fuel into the incinerator (30), an auxiliary fuel flow meter (44) and an auxiliary fuel adjustment valve (45) provided midway through a pipe (43) connected between the auxiliary fuel supply device (42) and the incinerator (30); a calculator (50) for calculating values ​​measured by a flowmeter for measuring the flow rate of the sludge and a pressure gauge for measuring the pressure of the sludge, the flowmeter and the pressure gauge being provided in a pipe connected to the mixer (20), and determining an index of the water content; a control device (60) for adjusting the supply amount by the sludge transfer pumps provided in the plurality of storage hoppers using an index of moisture content from a calculator (50), and for adjusting the supply amount of cooling water and auxiliary fuel by the cooling water regulating valve (35) and the auxiliary fuel regulating valve (45) based on the furnace temperature measured by the furnace thermometer (31).

3. a plurality of storage hoppers for storing a plurality of sludges having different properties; a plurality of transfer pumps for transferring the sludge to a mixer (20); a flow meter for measuring the flow rate of the sludge and a pressure gauge for measuring the pressure of the sludge, which are provided in the middle of the piping connected to the transfer pumps and the mixer (20); an in-furnace thermometer (31) provided in the incinerator (30); a cooling water supply device (32) for supplying cooling water into the incinerator (30); and a cooling water flow meter (34) and a cooling water adjustment valve (35) provided in the middle of the piping (33) connected to the cooling water supply device (32) and the incinerator (30); an auxiliary fuel supply device (42) for supplying auxiliary fuel into the incinerator (30), an auxiliary fuel flow meter (44) and an auxiliary fuel adjustment valve (45) provided midway through a pipe (43) connected between the auxiliary fuel supply device (42) and the incinerator (30); a calculator (50) for calculating a water content index by calculating measured values ​​of a flow meter for measuring a flow rate of the sludge and a pressure meter for measuring a pressure of the sludge, the flow meter and the pressure meter being provided in a pipe connected to the mixer (20); a control device (60) for adjusting the supply amount by the sludge transfer pumps provided in the plurality of storage hoppers based on the moisture content from a calculator (50), and for adjusting the supply amount of cooling water and auxiliary fuel by the cooling water regulating valve (35) and the auxiliary fuel regulating valve (45) based on the furnace temperature measured by the furnace thermometer (31).

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