Sludge incineration method and sludge incineration system

Abstract

To provide a sludge combustion method for supplying each of a plurality of sludge having different properties into a fluid bed type incinerator, mixing and incinerating the supplied sludge in the fluid bed type incinerator, and minimizing consumption of supplementary fuel and cooling water and mixing and incinerating the sludge.SOLUTION: A sludge incineration method includes: determining a flow rate and a pressures of each sludge with different properties (sludge A and sludge B) which is supplied to a fluid bed type incinerator 30 from a flow meter and a pressure gauge; calculating the determined flow rate values and pressure values by a calculator and determining an index (per flow rate unit time) of a moisture percentage; and determining a supply ratio of the sludge with different properties which is supplied to the fluid bed type incinerator on the basis of the index of the percentage moisture. The method includes: supplying sludge with different properties to the fluid bed type incinerator on the basis of the supply ratio; mixing and incinerating the supplied sludge in the fluid bed type incinerator; and changing a supply ratio of the sludge A and the sludge B supplied to the fluid bed type incinerator on the basis of a temperature in the fluid bed type incinerator during combustion, and minimizing fuel cost and cooling water cost required for sludge incineration.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and a system for incinerating sludge, in which sludge with different properties (moisture content, heat value) generated during the sewage treatment process at a sewage treatment plant is fed into a fluidized bed incinerator and mixed and incinerated in the fluidized bed incinerator, to control the supply ratio of sludge with different properties (moisture content, heat value) fed into the fluidized bed incinerator. [Background technology]

[0002] A fluidized bed incinerator is an incinerator that creates a fluidized bed by fluidizing a fluidizing medium such as sand placed in the furnace using air pumped in from the bottom of the furnace, and then incinerates the materials to be incinerated, such as sewage sludge or municipal waste, that are placed in the heated fluidized bed by stirring them together with the fluidized medium. During the sewage treatment process, the solids that have been separated and precipitated are concentrated and dehydrated, producing dehydrated sludge. Dehydrated sludge is usually incinerated, but it can be incinerated as is or after being reduced in volume by anaerobic digestion. The latter method utilizes methane fermentation, which leads to the effective use of methane gas as an energy resource. However, digestion increases the affinity between the decomposition products of solids in the sludge and water, producing 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 or 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 sludge incinerator at the collection facility, sludge with different water content and heat value is supplied to the fluidized bed incinerator that supplies the sludge to be incinerated.

[0003] Even in sewage treatment plants that do not have centralized facilities, there is raw sludge with a high solids concentration in the primary settling tank (low moisture content, high heat value) and excess sludge derived from microorganisms in the final settling tank (high moisture content, low heat value).In addition, there may be sludge that has undergone a sludge digestion process and sludge that has not.These sludges with different properties are supplied to a fluidized bed incinerator, resulting in sludge with different moisture contents and heat values. Summary of the Invention [Problem to be solved by the invention]

[0004] When sludge with different moisture contents is fed into a fluidized bed incinerator, the combustion temperature is controlled by adjusting the amount of auxiliary fuel such as heavy oil or city gas supplied or by injecting cooling water into the furnace. Therefore, when difficult-to-burn sludge is continuously supplied, a lot of auxiliary fuel will be consumed for a long time to operate the incinerator at a high combustion temperature, and when highly combustible sludge is continuously supplied, cooling water will be injected without effectively utilizing the heat value that the sludge actually possesses.

[0005] In order to solve the above problem, the inventors have determined 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" without using a moisture content meter, and controlled the supply ratio of sludge A and sludge B. Figure 5 is a diagram showing the relationship between sludge flow rate and pressure value (for each moisture content), with the vertical axis showing the sludge pressure value and the horizontal axis showing 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) is shown by the line connecting the minimum and maximum measured pressure values. 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 5, 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 6 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. 6, 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 utilize the above-mentioned "relationship between sludge flow rate, sludge pressure, and moisture content" to supply sludge with different properties to a fluidized bed incinerator, and to minimize consumption of auxiliary fuel and cooling water by adjusting the amount of sludge with different properties supplied to the fluidized bed incinerator based on the internal temperature of the fluidized bed incinerator. [Means for solving the problem]

[0006] 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 a plurality of sludges having different characteristics are supplied to a fluidized bed incinerator from different supply routes, and the sludge is incinerated in the fluidized bed incinerator at a sludge supply ratio that can reduce or eliminate the need for auxiliary fuel and cooling water, a furnace temperature control step of burning the sludge that meets the sludge supply ratio in a fluidized bed incinerator and controlling the furnace temperature by adjusting the supply amount of auxiliary fuel and cooling water based on the furnace temperature in the fluidized bed incinerator; a sludge supply rate 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 supply rate of sludge having different properties to be supplied to the fluidized bed incinerator based on the determined index, and supplying sludge based on the determined sludge supply rate; a sludge flow rate control step for adjusting the amount of sludge having different properties to be supplied to the fluidized bed incinerator in response to the sludge supply rate control step; A sludge incineration method comprising the steps of:

[0007] [2] A plurality of storage hoppers for storing a plurality of sludges having different properties, a plurality of transfer pumps for supplying the sludge to the fluidized bed incinerator (30), 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 fluidized bed incinerator (30), A furnace thermometer (31) provided in the fluidized bed incinerator (30), a cooling water supply device (32) that supplies cooling water into the incinerator (30), a cooling water flow meter (34) and a cooling water regulating valve (35) provided in the middle of 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 fluidized bed 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 fluidized bed incinerator (30); a calculator (50) for calculating a water content index by calculating values ​​measured by a flowmeter for measuring the flow rate of 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 fluidized bed incinerator (30); a control device (60) for adjusting the supply amount by the sludge transfer pumps provided at the multiple storage hoppers based on 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). Effect of the Invention

[0008] According to the present invention, the supply ratio of sludge with different properties to be supplied to a fluidized bed incinerator 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] 1 is a schematic diagram showing an embodiment of the present invention; [Diagram 2] Flowchart of furnace temperature control in the embodiment [Diagram 3] Flowchart of sludge supply rate control in the embodiment [Figure 4] Flowchart of sludge flow rate control in the embodiment [Diagram 5] A diagram showing the relationship between sludge flow rate and pressure (for each moisture content) [Figure 6]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. FIG. 1 is a schematic diagram showing an embodiment of the present invention. This embodiment includes a first storage hopper 1 for storing sludge A, a sludge discharger 2 for discharging the sludge A from the first storage hopper 1, and a transfer pump 3 for supplying the sludge A. The system includes a second storage hopper 11 for storing sludge B having properties different from those of 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. In this embodiment, sludge A and B with different properties are respectively supplied to the routes; however, in reality, the properties of the sludge change over time in each route, and it should be noted that the properties of the sludge supplied in each route are not necessarily different. A flow meter 5 for measuring the sludge flow rate and a pressure gauge 6 for measuring the sludge pressure are provided in the middle of the piping 4 connected to the transfer pump 3 and the fluidized bed incinerator 30, and a flow meter 15 for measuring the sludge flow rate and a pressure gauge 16 for measuring the sludge pressure are provided in the middle of the piping 14 connected to the transfer pump 13 and the fluidized bed incinerator 30. 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 each sludge to the fluidized bed incinerator 30.

[0011] The fluidized bed incinerator 30 is provided with an in-furnace thermometer 31 for measuring the in-furnace temperature. In addition, a cooling water supply system for cooling the inside of the fluidized bed incinerator according to the temperature inside the furnace where 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 fluidized bed incinerator 30, and a cooling water flow meter 34 and a cooling water adjustment valve 35 are provided in the middle of a pipe 33 connected between the cooling water supply device 32 and the fluidized bed incinerator 30. The auxiliary fuel supply system includes an auxiliary fuel supply device 42 that supplies auxiliary fuel into the fluidized bed incinerator 30, and an auxiliary fuel flow meter 44 and an auxiliary fuel adjustment valve 45 are provided in the middle of a pipe 43 that connects the auxiliary fuel supply device 42 to the fluidized bed incinerator 30.

[0012] In the schematic diagram showing the present embodiment, 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 using a calculator 50 based on the flow rate and pressure values ​​obtained from a flow meter and a pressure gauge (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) to control the various devices, based on the built-in control program.

[0013] 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 sludge to the fluidized bed incinerator 30 according to this embodiment will be described. Dewatered sludge A generated in the water treatment process of a sewage treatment plant is stored in a first storage hopper 1, and the sludge A is transferred to a fluidized bed incinerator 30 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 and a pressure gauge 6 which are installed in a pipe 4 connected to the transfer pump 3 and the fluidized bed incinerator 30 and measure the sludge flow rate, and the respective measured values ​​are sent to a calculation device 50, where an indicator of the moisture content of sludge A is calculated.

[0015] Meanwhile, dewatered sludge B generated in the water treatment process of the sewage treatment plant is stored in a second storage hopper 11, where the sludge B is transferred to a fluidized bed incinerator 30 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 and a pressure gauge 16 which are installed in a pipe 14 connected to the transfer pump 13 and the fluidized bed incinerator 30 and measure the sludge flow rate, 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 value of sludge A and sludge B are measured by the flowmeters (5, 15) and pressure gauges (6, 16), and the measured values ​​are output to the calculator 50, which performs a calculation (pressure value ÷ flow rate value). Using the obtained moisture content index, the sludge A and sludge B are transported to the fluidized bed incinerator 30, mixed, and incinerated in a supply ratio that results in sludge that does not require auxiliary fuel and cooling water, as compared to the conventional method in which sludge A and sludge B are supplied to the incinerator without taking into account the moisture content in the sludge.

[0016] A method of supplying sludge A and sludge B, which have different properties, to the fluidized bed incinerator 30 according to this embodiment will be described. Dewatered sludge A generated in the water treatment process of a sewage treatment plant is stored in a first storage hopper 1, and the sludge A is supplied to a fluidized bed incinerator 30 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 and a pressure gauge 6 which are installed in a pipe 4 connected to the transfer pump 3 and the fluidized bed incinerator 30, and the respective measured values ​​are sent to a calculation device 50, where an indicator of the moisture content of sludge A is calculated.

[0017] Meanwhile, dewatered sludge B generated in the water treatment process of a sewage treatment plant is stored in a second storage hopper 11, where the sludge B is supplied to a fluidized bed incinerator 30 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 and a pressure gauge 16 that measure the sludge flow rate and are installed in a pipe 14 connected to the transfer pump 13 and the fluidized bed incinerator 30, 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 by the flowmeters (5, 15) and pressure gauges (6, 16), and the measured values ​​are output to the calculator 50, which performs a calculation (pressure value ÷ flow rate value).The sludge A and sludge B are then transported to the fluidized bed incinerator 30 in a ratio of A and B so that the sludge does not require as much auxiliary fuel and cooling water, and are mixed and incinerated.

[0018] In explaining a method of transferring sludge A and sludge B to a fluidized bed incinerator 30 in a ratio of A and B so that the sludge does not require auxiliary fuel and cooling water, and then mixing and incinerating the sludge A and sludge B in the fluidized bed of the fluidized bed incinerator 30, first, the control of the in-furnace temperature due to the incineration of the sludge supplied to the fluidized bed incinerator 30 will be explained using FIG. 2 which shows a control flowchart for controlling the in-furnace temperature. 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 in-furnace temperature (Ti), the opening of the auxiliary fuel regulating valve 45 is increased to increase the amount of auxiliary fuel supplied to the fluidized bed incinerator, and the opening of the cooling water regulating valve 35 is reduced to decrease the amount of cooling water injected into the fluidized bed 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 in-furnace temperature (Ti), the opening of the auxiliary fuel regulating valve 45 is reduced to reduce the amount of auxiliary fuel supplied to the fluidized bed incinerator, and the opening of the cooling water regulating valve 35 is increased to increase the amount of cooling water injected into the fluidized bed 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.

[0019] Next, using Figure 3, which is a sludge supply ratio control flowchart for controlling the sludge supply ratio of sludge A and sludge B when incinerating sludge A and sludge B supplied to the fluidized bed incinerator 30 and controlling the temperature inside the furnace by using auxiliary fuel and cooling water, we will explain the control of the flow rate (supply amount) of sludge A or sludge B supplied into the furnace. Step 1 (S1) The measurement value of the auxiliary fuel supply amount Ff is used to determine whether auxiliary fuel is being supplied in the fluidized bed incinerator. Step 2 (S2) When auxiliary fuel is used in a fluidized bed 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 fluidized bed 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 fluidized bed incinerator, it is judged whether the moisture content index of sludge A (Pa÷Fa) calculated by the calculator 50 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, reduce the set value of the flow rate of sludge B and proceed to *1B. S7 is also performed at the same time. Step 9 (S9) If cooling water is not being used in the fluidized bed incinerator, the control ends.

[0020] 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] When auxiliary fuel is used in a fluidized bed incinerator 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] When cooling water is used in a fluidized bed incinerator 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 supply ratio at this time is determined based on the usage status of the cooling water or auxiliary fuel.

[0021] Next, using Figure 4, which is a control flowchart of the sludge flow rates (1A, 1B) obtained by controlling the sludge supply ratio of sludge A and sludge B, we will explain the control of the supply rates (flow rates) of the flow rate (Fa) of sludge A and the flow rate (Fb) of sludge B. Step 1 (S1) Following *1A from the sludge supply rate control, the increased or decreased sludge flow rate set 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 supply rate 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.

[0022] Based on the above-mentioned controls, the sludge incineration method will be described. As described above, sludge A and sludge B are supplied to the fluidized bed incinerator 30 at a sludge supply ratio (the ratio of sludge A and sludge B that does not use auxiliary fuel and cooling water) of sludge A and sludge B that is set based on their respective "pressure gauge measurement value ÷ flow meter measurement value (excluding)" (an index of moisture content), and are mixed and incinerated in the fluidized bed of the fluidized bed incinerator 30. Here, the temperature inside the fluidized bed incinerator 30 in which the sludge is being burned is measured by the in-furnace thermometer 31, and as necessary, cooling water is injected into the incinerator 30 to adjust the in-furnace temperature, or auxiliary fuel is supplied into the incinerator to adjust the temperature, thereby controlling the in-furnace 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 fluidized bed incinerator 30 is high, a large amount of sludge with a high moisture content, i.e., a large amount of water, 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 water, is supplied, thereby controlling the use of fuel and cooling water as much as possible to maintain the set furnace temperature.

[0023] [Table 1] Table 1 shows an example of the daily costs for incinerating sludge A, which has a high proportion of sludge that does not go through the digestion process, followed by sludge B, which has a high proportion of sludge that goes through the digestion process, or vice versa, and for supplying sludge A and sludge B to a fluidized bed 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 large amount of heat, requiring cooling water to raise the temperature inside the fluidized bed 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, if the supply ratio of sludge A and sludge B is controlled and they are supplied simultaneously, the cost required to incinerate 50 tons of sludge 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.

[0024] In this way, it is clear that incinerating sludge by controlling the supply ratio of sludge A and sludge B and taking into consideration the effect of the moisture content of each sludge can reduce 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, although the above explanation has been given as an example of a case in which sludge A and sludge B are supplied to a fluidized bed incinerator, the present invention is not limited to this and can also be applied to a case in which there are multiple supply routes.

[0025] 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 6, 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]

[0026] 1: First storage hopper 11: Second storage hopper 2, 12: Sludge discharger 3, 13: Transfer pump 4, 14: Piping 5, 15: Flowmeter 6, 16: Pressure gauge 30: Fluidized bed incinerator 31:Furnace thermometer 32: Cooling water supply device 33:Plumbing 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 a plurality of sludges having different properties are supplied to a fluidized bed incinerator from different supply routes, and incinerated in the fluidized bed incinerator at a sludge supply ratio that can reduce or eliminate the need for auxiliary fuel and cooling water, comprising: a furnace temperature control step of burning the sludge that meets the sludge supply ratio in a fluidized bed incinerator and controlling the furnace temperature by adjusting the supply amount of auxiliary fuel and cooling water based on the furnace temperature in the fluidized bed incinerator; a sludge supply rate 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 supply rate of sludge having different properties to be supplied to the fluidized bed incinerator based on the determined index, and supplying sludge based on the determined sludge supply rate; a sludge flow rate control step for adjusting the amount of sludge having different properties to be supplied to the fluidized bed incinerator in response to the sludge supply rate 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 supplying the sludge to a fluidized bed incinerator (30), 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 midway in the pipes connected to the transfer pumps and the fluidized bed incinerator (30), A furnace thermometer (31) provided in the fluidized bed incinerator (30), a cooling water supply device (32) that supplies cooling water into the fluidized bed incinerator (30), a cooling water flow meter (34) and a cooling water adjustment valve (35) provided midway in a pipe (33) that is connected between the cooling water supply device (32) and the fluidized bed incinerator (30), an auxiliary fuel supply device (42) for supplying auxiliary fuel into the fluidized bed incinerator (30); and 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 fluidized bed incinerator (30); a calculator (50) for calculating the measured values ​​of a flowmeter for measuring the flow rate of sludge and a pressure gauge for measuring the pressure of the sludge, the flowmeter and the pressure gauge being provided in the middle of a pipe connected to the fluidized bed incinerator (30), and determining an index of the moisture content; a control device (60) for adjusting the supply amount by the sludge transfer pumps provided on a plurality of storage hoppers based on a moisture content index 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).

Images