Method for incinerating oily waste

Abstract

To provide a method of incinerating oily waste, capable of improving incineration efficiency of oily waste.SOLUTION: The method of incinerating oily waste includes: a control temperature setting step of setting a control temperature of a rotary kiln; a mixing step of preparing oily waste obtained by mixing first oil-containing sludge stored in a first oil-containing sludge storage tank and oil-component sludge stored in an oil-component sludge storage tank and generating a smaller amount of clinker generated when it is incinerated alone, than that generated when it is incinerated by the first oil-containing sludge alone; an incineration step of incinerating the oily waste in the rotary kiln and measuring a temperature in the rotary kiln; and a mixing-ratio setting step of setting a mixing ratio of the first oil-containing sludge and the oil-component sludge based on the temperature measured by the incineration step by referring to the control temperature, wherein mixed oily waste is prepared by adjusting so as to be the mixing ratio set by the mixing-ratio setting step, and is incinerated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for incinerating oily waste. [Background technology]

[0002] When oil-containing sludge is incinerated in an incinerator, if the combustion temperature becomes too high, clinker, which is the burned and hardened combustion residue (iron-based sludge), may adhere to the furnace walls. The adhesion of clinker reduces the incinerator's volume, reducing the amount of oil-containing sludge that can be processed and lowering incineration efficiency. Furthermore, the adhesion of clinker may cause the oil-containing sludge to flow back toward the incinerator's feed port, which, in the worst case scenario, could lead to equipment failure or a fire. Therefore, if clinker adheres, it is necessary to stop the incinerator's operation and remove the adhered clinker.

[0003] Conventionally, Patent Documents 1 to 4 have disclosed techniques relating to methods for incinerating oil-containing sludge.

[0004] Patent Document 1 discloses a method for operating an oily waste incinerator in which high-calorie fuel oil is produced by adding and mixing highly volatile waste oil with an oil for adjusting calorie or viscosity depending on the properties of the waste oil, and this high-calorie fuel oil is used as an auxiliary fuel to incinerate oily waste including oil-containing sludge and waste oil.

[0005] Patent Document 2 discloses a method for incinerating oil-containing sludge in a rotary kiln incinerator, in which the oil-containing sludge is attached to miscellaneous waste such as wood chips and paper waste, and then the sludge is loaded into the rotary kiln incinerator and incinerated.

[0006] Patent Document 3 discloses a method for incinerating oil-containing sludge in an incinerator that incinerates general miscellaneous garbage, waste oil, etc., and oil-containing sludge whose main component is iron or iron oxide, in which a main combustion chamber that incinerates general miscellaneous garbage, waste oil, etc. at high temperatures is connected to a secondary combustion chamber that incinerates oil-containing sludge at low temperatures, a sludge separation chamber is located at the connection between this secondary combustion chamber and the main combustion chamber, and a secondary combustion chamber is located in the exhaust gas flow path where exhaust gases from the main combustion chamber and the secondary combustion chamber join.

[0007] Patent Document 4 discloses a method for incinerating oil-containing sludge in a rotary kiln incinerator, in which the oil-containing sludge is dispersed in the form of small nodules of 1 to 10 mm on the inner wall surface of the kiln heated to a high temperature and then incinerated. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-44956 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-323213 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-317717 [Patent Document 4] Japanese Patent Application Laid-Open No. 1996-121736 Summary of the Invention [Problem to be solved by the invention]

[0009] In the techniques disclosed in Patent Documents 1 to 4, auxiliary fuels such as high-calorie auxiliary fuels or miscellaneous garbage are added to oily waste such as oil-containing sludge. This increases the overall calorie content of the waste to be incinerated and raises the temperature inside the rotary kiln. In this way, conventional techniques have adopted a method of promoting incineration by adding auxiliary fuels.

[0010] On the other hand, the amount of auxiliary fuel to be added is determined based on the calorie content, etc., of the oil-containing sludge. However, since the oil content, moisture content, ash content, etc. of the oil-containing sludge fluctuate, it is necessary to measure the calorie content, oil content, moisture content, etc., of the oil-containing sludge to determine the amount of auxiliary fuel to be added. However, because this measurement takes time, even if auxiliary fuel is added based on the measurement results, the properties of the oil-containing sludge used for the measurement may differ from the properties of the oil-containing sludge actually incinerated in the incinerator. This makes it difficult to take flexible measures on-site to adjust the temperature inside the rotary kiln to an appropriate level, and there is a risk, for example, that the temperature inside the rotary kiln may rise excessively, causing clinker to adhere to the rotary kiln furnace wall. In particular, among the various types of oil-containing sludge generated in the steel manufacturing process, there are some that exhibit particularly large fluctuations in oil content, and this tendency becomes more pronounced when such oil-containing sludge is incinerated. When clinker adheres to the furnace walls of a rotary kiln, the operation of the rotary kiln must be stopped to remove the clinker, which reduces the efficiency of incineration of oily waste.

[0011] Therefore, the present invention has been devised in consideration of the above circumstances, and its object is to provide a method for incinerating oily waste that can improve the efficiency of incineration of oily waste. [Means for solving the problem]

[0012] The method for incinerating oily waste according to the present invention is a method for incinerating oily waste using a rotary kiln, and includes a control temperature setting step of setting a control temperature for the rotary kiln based on a previously obtained relationship between the temperature inside the rotary kiln and the generation of clinker, and a mixing step of generating oily waste by mixing first oil-containing sludge stored in a first oil-containing sludge storage tank with oil-containing sludge stored in the oil sludge storage tank and which generates less clinker when incinerated alone than when the first oil-containing sludge is incinerated alone. The method comprises an incineration process in which the oily waste is incinerated in the rotary kiln and the temperature inside the rotary kiln is measured, and a mixing ratio setting process in which the mixing ratio of the first oil-containing sludge and the oil-content sludge is set based on the temperature measured in the incineration process by referring to the control temperature, wherein in the mixing process, the first oil-containing sludge and the oil-content sludge are adjusted to the mixing ratio set in the mixing ratio setting process to produce mixed oily waste, and in the incineration process, the oily waste after the mixing ratio has been adjusted is incinerated. [Effects of the Invention]

[0013] According to the present invention, it is possible to improve the efficiency of incineration of oily waste. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of an incineration system for oily waste according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram mainly showing a charging device and a rotary kiln in an example of an oily waste incineration system according to an embodiment. [Figure 3] FIG. 3 is a perspective view mainly showing an input pipe in an example of an incineration system for oily waste according to an embodiment. [Figure 4] FIG. 4 is a graph in Example 1, with the horizontal axis representing the number of days of operation and the vertical axis representing the furnace wall temperature and the ratio of the first oil-containing sludge to the oil-containing sludge. [Figure 5]FIG. 5 is a graph in Example 1, in which the horizontal axis represents the ratio of the first oil-containing sludge to the sum of the first oil-containing sludge and the oil sludge, and the vertical axis represents the furnace wall temperature. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the oily waste incineration method according to the embodiment will be described in detail with reference to the drawings.

[0016] The method for incinerating oily waste uses an oily waste incineration system 100. Hereinafter, the oily waste incineration system 100 will be simply referred to as the incineration system 100.

[0017] The incineration system 100 comprises a first oil-containing sludge storage tank 1, an oil-containing sludge storage tank 2, a mixing tank 4, a waste oil storage tank 5, a transfer pipe 6, a charging device 7, a rotary kiln 8, and a gas treatment facility 9.

[0018] The first oil-containing sludge is stored in the first oil-containing sludge storage tank 1. The first oil-containing sludge is oil-containing sludge that has a different origin (generation process) from the oil-containing sludge. For example, the first oil-containing sludge has a higher oil concentration than the oil-containing sludge, or the oil concentration is unknown. For example, the first oil-containing sludge has a greater variability in oil concentration than the oil-containing sludge. Due to the greater variability of the first oil-containing sludge, the oil concentration of the first oil-containing sludge may be lower than that of the oil-containing sludge. Therefore, when the first oil-containing sludge is incinerated alone in the rotary kiln 8, clinker may or may not be generated. The first oil-containing sludge may be, for example, a mixture composed of multiple oil-containing sludges. The first oil-containing sludge may be, for example, a single type of oil-containing sludge whose oil concentration has a greater variability than the oil-containing sludge. The first oil-containing sludge may have a higher calorie content than the oil-containing sludge. The first oil-containing sludge is primarily composed of iron and iron oxide, and further contains oil and water. The first oil-containing sludge may include, for example, sludge containing oil generated by recovering and filtering used rolling oil generated in a rolling process. The first oil-containing sludge may include, for example, grinding sludge containing oil generated in a rolling process. The first oil-containing sludge may include, for example, sludge containing oil generated during dredging and cleaning of a factory that uses oil.

[0019] The oily sludge is stored in the oily sludge storage tank 2. The oily sludge is collected from a known source (generation process) with a low oil content and little fluctuation in oil content. Therefore, when the oily sludge is incinerated alone in the rotary kiln 8, no or very little clinker is generated, and the amount of clinker generated is less than when the first oily sludge is incinerated alone. The oily sludge has the property of lowering the temperature inside the rotary kiln 8 when the furnace wall temperature rises to the control temperature due to fluctuations in the oil content of the first oily sludge. By incinerating the oily waste mixed with the first oily sludge, the oily sludge adjusts the temperature inside the rotary kiln 8 to below the control temperature.

[0020] The oil-containing sludge is composed of at least one of a second oil-containing sludge having a different origin from the first oil-containing sludge and a dehydrated scum cake. The oil-containing sludge storage tank 2 has a second oil-containing sludge storage tank 21 in which the second oil-containing sludge is stored and a dehydrated scum cake storage tank 22 in which the dehydrated scum cake is stored.

[0021] The second oil-containing sludge is stored in the second oil-containing sludge storage tank 21. The second oil-containing sludge has a lower oil concentration than the first oil-containing sludge, and the variability of the oil concentration is smaller than that of the first oil-containing sludge. Therefore, when the second oil-containing sludge is incinerated alone in the rotary kiln 8, no or very little clinker is generated, and the amount of clinker generated is less than when the first oil-containing sludge is incinerated alone. The second oil-containing sludge may have a lower calorie content than the first oil-containing sludge. The second oil-containing sludge is an oil-containing sludge whose main components are iron and iron oxide, and further contains oil and moisture. The second oil-containing sludge is generated through a different process than the first oil-containing sludge, and may include oil-containing sludge recovered during the treatment of wastewater generated during the rolling process, such as settling tank sludge and filter backwash sludge.

[0022] The dewatered scum cake is stored in the dewatered scum cake storage tank 22. The dewatered scum cake has a lower oil concentration than, for example, the first oil-containing sludge, and the variability of the oil concentration is smaller than that of the first oil-containing sludge. Therefore, when the dewatered scum cake is incinerated alone in the rotary kiln 8, no or very little clinker is generated, and the amount of clinker generated is less than when the first oil-containing sludge is incinerated alone. The dewatered scum cake may have a lower calorie content than the first oil-containing sludge. The dewatered scum cake is primarily composed of iron and iron oxide, and also contains oil and moisture. The dewatered scum cake is generated through a different process than the first oil-containing sludge. For example, the dewatered scum cake is a sludge-like substance remaining after flocculation and dehydration of scum recovered during the treatment of oil-containing wastewater from the steel manufacturing process.

[0023] The oil-containing sludge of the present invention is not limited to sludge recovered by solid-liquid separation in wastewater treatment processes, and sludge from other processes may be used as the oil-containing sludge as long as the sludge has a low oil concentration and little variability.

[0024] The variability is evaluated, for example, by the fluctuation range, which is the difference between the maximum and minimum values ​​measured multiple times. Note that the variability may also be evaluated by the standard deviation, relative standard deviation, or the like.

[0025] The mixing tank 4 mixes the first oil-containing sludge stored in the first oil-containing sludge storage tank 1 with an oil sludge composed of the second oil-containing sludge stored in the second oil-containing sludge storage tank 21 and the dewatered scum cake stored in the dewatered scum cake storage tank 22 to produce oily waste. The mixing ratio of the oily waste is, for example, the volume ratio of the first oil-containing sludge to the oily sludge. Note that the mixing ratio of the oily waste may also be the weight ratio of the first oil-containing sludge to the oily sludge.

[0026] The mixing ratio of the second oil-containing sludge to the dehydrated scum cake in the oil-containing sludge is, for example, 1:1 by volume, but may be any ratio. That is, the oil-containing sludge may be composed of only the second oil-containing sludge or only the dehydrated scum cake. The mixing ratio of the second oil-containing sludge to the dehydrated scum cake in the oil-containing sludge may also be a weight ratio. The oil concentration of the oil-containing sludge is, for example, lower than that of the first oil-containing sludge. Furthermore, the oil-containing sludge has smaller variability in oil concentration than the first oil-containing sludge. The oil-containing sludge may have a lower calorie content than the first oil-containing sludge.

[0027] Waste oil used as auxiliary fuel is stored in the waste oil storage tank 5. The waste oil may be, for example, hydraulic oil, tar sludge, or oil-containing waste liquid. The waste oil is sprayed into the rotary kiln 8 from a transfer pipe and an inlet separate from the oily waste, and is mixed at, for example, 8% to 10% by volume with respect to the total oily waste, but this ratio is optional and may be omitted.

[0028] The transfer pipe 6 is a pipe that transfers the oily waste produced in the mixing tank 4 to the input device 7. The transfer pipe 6 can pressure-feed the oily waste to the input device 7 using a pressure-feeding device such as a piston pump (not shown).

[0029] The charging device 7 charges oily waste into the rotary kiln 8. The charging device 7 has a charging pipe 71 connected to the waste oil storage tank 5 and a charging pipe 72 connected to the transfer pipe 6. The charging pipe 71 charges the waste oil stored in the waste oil storage tank 5 into the rotary kiln 8. The charging pipe 72 charges the oily waste transferred from the transfer pipe 6 into the rotary kiln 8.

[0030] As shown in Fig. 3, the input pipe 72 has a tray 73 and an injection unit 74. The tray 73 is provided at the outlet of the input pipe 72 and receives the oily waste discharged from the outlet of the input pipe 72. The injection unit 74 injects a high-pressure fluid such as pressurized air or steam toward the oily waste in the tray 73. By injecting the high-pressure fluid from the injection unit 74 at the oily waste in the tray 73, the oily waste can be dispersed within the rotary kiln 8. Note that the input pipe 72 may be provided without the tray 73 and the injection unit 74.

[0031] The rotary kiln 8 is an incinerator that incinerates oily waste. The rotary kiln 8 has a rotary drum 81, a burner 82, an observation window 83, an incineration ash outlet 84, and a gas outlet 85.

[0032] The rotary drum 81 is formed in a cylindrical shape and configured to be rotatable. The rotary drum 81 has the input pipe 72 and the burner 82 disposed on the base end side of the rotary drum 81.

[0033] Burner 82 is a burner that increases the temperature inside rotary drum 81 and is used to incinerate oily waste inside rotary drum 81.

[0034] The sight glass 83 is for observing the inside of the rotating drum 81. The thermometer 86 measures the oven wall temperature through the sight glass 83 of the rotating drum 81 in a non-contact manner, and is, for example, an infrared radiation thermometer. The oven wall temperature can also be measured by a CCD camera, an infrared thermo camera, or the like, as long as it can investigate the relationship between the oven wall temperature and clinker generation.

[0035] The incineration ash outlet 84 is for discharging the incineration ash generated by the incineration of oily waste, and the gas outlet 85 is for discharging the gas generated by the incineration of oily waste.

[0036] The gas treatment equipment 9 is a well-known equipment that treats the gas discharged from the gas outlet 85 of the rotary kiln 8. The gas treatment equipment 9 is composed of, for example, a secondary combustion chamber, a boiler, a stabilizer, an electrostatic precipitator, a chimney, etc., and can appropriately treat the gas discharged from the gas outlet 85 so that it can be discharged into the atmosphere.

[0037] Next, an example of a method for incinerating oily waste will be described. The method for incinerating oily waste includes a controlled temperature setting step, a mixing step, an incineration step, and a mixing ratio setting step.

[0038] In the method for incinerating oily waste, first oil-containing sludge is stored in first oil-containing sludge storage tank 1, and oil-containing sludge that produces less clinker when incinerated alone than when the first oil-containing sludge is incinerated alone is stored in oil-containing sludge storage tank 2. At this time, second oil-containing sludge is stored in second oil-containing sludge storage tank 21. Also, dehydrated scum cake is stored in dehydrated scum cake storage tank 22. In this way, sludge is separated by generation process, and oil-containing sludge with a low oil concentration and little variability in oil concentration (second oil-containing sludge and dehydrated scum cake) and first oil-containing sludge, which is generated in a different process from the oil-containing sludge, are stored separately.

[0039] In the control temperature setting process, the temperature when the oily waste is incinerated in the rotary kiln 8 is measured, and the relationship between the temperature inside the rotary kiln 8 and the generation of clinker is obtained in advance. In the control temperature setting process, the control temperature of the rotary kiln 8 is set based on the previously obtained relationship between the temperature inside the rotary kiln 8 and the generation of clinker.

[0040] The temperature measurement points for the furnace wall temperature of the rotary kiln 8 are determined in advance, and the relationship between the temperature measured at the measurement points and the generation of clinker in the furnace is investigated in advance, and the temperature at which clinker is generated is set as the control temperature. The control temperature is set to, for example, 1000°C.

[0041] In the mixing process, the first oil-impregnated sludge stored in the first oil-impregnated sludge storage tank 1, the second oil-impregnated sludge stored in the second oil-impregnated sludge storage tank 21, and the dewatered cake stored in the dewatered scum cake storage tank 22 are loaded into the mixing tank 4 using a backhoe or other device. In the mixing process, the first oil-impregnated sludge and an oil sludge composed of the second oil-impregnated sludge and the dewatered scum cake are mixed in the mixing tank 4 using a mixing device such as a backhoe to generate oily waste. In the mixing process, the first oil-impregnated sludge and the oil sludge are mixed at a first mixing ratio r1 to form the oily waste to be incinerated first. For example, the first oil-impregnated sludge and the oil sludge are mixed at a volume ratio of 2:1 as the first mixing ratio r1.

[0042] Then, in the mixing step, the oily waste mixed in the mixing tank 4 is transferred to the input device 7 through the transfer pipe 6.

[0043] Next, in the incineration process, the oily waste is fed into the rotating drum 81 of the rotary kiln 8 via the feed pipe 72, and the oily waste is incinerated. At this time, the waste oil stored in the waste oil storage tank 5 is also fed into the rotating drum 81 of the rotary kiln 8 via the feed pipe 71. Also, in the incineration process, the furnace wall temperature inside the rotating drum 81 is measured by a thermometer 86.

[0044] Then, in the mixing ratio setting step, a preset control temperature is referenced and the mixing ratio of the first oil-containing sludge to the oil-containing sludge is set based on the temperature measured in the incineration step.

[0045] After the mixing ratio setting step, the mixing step is carried out again, in which new oily waste is produced at the mixing ratio set in the mixing ratio setting step.

[0046] For example, when oily waste is incinerated at a first mixing ratio r1, if the temperature measured in the incineration process is less than the preset control temperature of 1000°C, the mixing ratio setting process continues to set the first mixing ratio r1. Then, in the mixing process, the first oil-containing sludge and oil sludge are mixed to adjust the first mixing ratio r1. Then, the oily waste produced by mixing at the first mixing ratio r1 is sequentially transferred to the charging device 7 via the transfer pipe 6. Note that if the temperature measured in the incineration process is less than the preset control temperature, the mixing ratio setting process may set the first mixing ratio r1 to a second mixing ratio r2 in which the oil sludge is reduced relative to the first oil-containing sludge. Then, in the mixing process, the first oil-containing sludge and oil sludge may be mixed at the second mixing ratio r2 in which the oil sludge is reduced. Then, in the incineration process, the oily waste after adjusting the mixing ratio is incinerated, and the temperature inside the rotary kiln 8 is adjusted.

[0047] For example, when oily waste is incinerated at a first mixing ratio r1, if the temperature measured during the incineration process exceeds the control temperature of 1000°C for a predetermined period of time, the mixing ratio setting process sets the first mixing ratio r1 to a second mixing ratio r2, which increases the amount of oil sludge. Then, in the mixing process, the first oil-containing sludge and oil sludge are mixed at the second mixing ratio r2, which increases the amount of oil sludge, to generate new oily waste. For example, at the second mixing ratio r2, the first oil-containing sludge and oil sludge are mixed at a volume ratio of 1:1, so that the amount of oil sludge is increased relative to the first oil-containing sludge from the first mixing ratio r1. Then, the oily waste mixed at the second mixing ratio r2 is sequentially transferred to the input device 7 via the transfer pipe 6.

[0048] Then, in the incineration process, the oily waste produced by mixing the first oil-containing sludge and the oil-content sludge at a second mixing ratio r2 of 1:1 by volume is incinerated. This adjusts the temperature inside the rotary kiln 8 to decrease. When the oily waste produced by incinerating the oily waste produced by mixing the first oil-containing sludge and the oil-content sludge at the second mixing ratio r2 of 1:1 by volume is incinerated, if the temperature measured in the incineration process is below the control temperature, the oily waste is continuously mixed at this second mixing ratio r2 and incinerated.

[0049] For example, in the incineration process, if the temperature measured when incinerating the generated oily waste mixed at the second mixing ratio r2 exceeds the control temperature, the mixing ratio setting process sets the mixing ratio to a third mixing ratio r3, which further increases the oil sludge from the second mixing ratio r2. Then, in the mixing process, the first oil-containing sludge and the oil sludge are mixed to achieve the third mixing ratio r3. To achieve the third mixing ratio r3, for example, the first oil-containing sludge and the oil sludge are mixed at a volume ratio of 1:2 so that the oil sludge is increased relative to the first oil-containing sludge from the second mixing ratio r2. Then, the oily waste mixed at the third mixing ratio r3 is sequentially transferred to the input device 7 via the transfer pipe 6, and the incineration process is subsequently carried out.

[0050] In this way, in the method for incinerating oily waste, the mixing step, the incineration step, and the mixing ratio setting step are repeated.

[0051] The ash generated by the incineration of oily waste is discharged from an incineration ash outlet 84. The gas generated by the incineration of oily waste is discharged from a gas outlet 85 and is appropriately treated in gas treatment equipment 9.

[0052] Here, the first oil-bearing sludge, for example, has a relatively high variability in oil concentration or an unknown oil concentration, and generates a relatively large amount of clinker. Therefore, in the conventional method of incinerating only the first oil-bearing sludge, it is difficult to stabilize the temperature inside the rotary kiln, and if the temperature inside the rotary kiln suddenly drops or rises, the incineration efficiency of the oily waste may decrease. In particular, if the combustion temperature becomes too high, the clinker formed by burning the combustion residue may adhere to the furnace wall.

[0053] In this regard, according to this embodiment, the system includes a control temperature setting step of setting the control temperature of the rotary kiln 8 based on the relationship between the temperature of the rotary kiln 8 and the generation of clinker, which has been obtained in advance; a mixing step of generating oily waste by mixing the first oil-containing sludge stored in the first oil-containing sludge storage tank 1 with the oil-containing sludge stored in the oil-containing sludge storage tank 2, which generates less clinker when incinerated alone than when the first oil-containing sludge is incinerated alone; an incineration step of incinerating the oily waste in the rotary kiln 8 and measuring the temperature inside the rotary kiln 8; and a mixing ratio setting step of setting the mixing ratio of the first oil-containing sludge and the oil-containing sludge based on the temperature measured in the incineration step, with reference to the control temperature. In the mixing step, the first oil-containing sludge and the oil-containing sludge are adjusted to the mixing ratio set in the mixing ratio setting step to generate oily waste, and in the incineration step, the oily waste after the mixing ratio has been adjusted is incinerated.

[0054] In this way, the amount of oil-containing sludge mixed is adjusted based on the temperature measured during the incineration process, referring to a preset control temperature. The oil-containing sludge and oil sludge separated in advance are used to adjust the amount of oil-containing sludge mixed in response to fluctuations in the first oil-containing sludge. Then, oily waste with an adjusted mixture ratio is produced, and the oily waste after the adjusted mixture ratio is incinerated, thereby performing a feedback operation to adjust the temperature inside the rotary kiln 8. This allows immediate on-site response to sudden increases or decreases in the temperature inside the rotary kiln, even for first oil-containing sludge whose oil concentration is unknown. Therefore, simply by separating the first oil-containing sludge and oil sludge in advance, clinker adhesion can be suppressed without installing new equipment. As a result, the incineration efficiency of oily waste can be improved.

[0055] According to this embodiment, in the mixing ratio setting process, a mixing ratio is set that increases the amount of oily sludge compared to the mixing ratio of the oily waste incinerated in the incineration process, based on the temperature measured in the incineration process. This makes it easy to adjust the temperature inside the rotary kiln 8 to be lower than the temperature measured when the oily waste was incinerated before the oily sludge mixing ratio was increased. This prevents clinker from adhering to the furnace wall, and eliminates the need to stop the operation of the rotary kiln 8 to remove the adhering clinker. As a result, the incineration efficiency of oily waste can be improved.

[0056] According to this embodiment, in the mixing process, oil-containing sludge with a lower oil content than the first oil-containing sludge is mixed. This allows the oil content of the entire oily waste to be reduced by increasing the amount of oil-containing sludge, and the oil content of the entire oily waste to be increased by reducing the amount of oil-containing sludge. This allows the temperature inside the rotary kiln 8 to be more reliably adjusted. As a result, the efficiency of incineration of oily waste can be improved.

[0057] According to this embodiment, in the mixing process, oily sludge with a lower calorie content than the first oil-containing sludge is mixed. This allows the calorie content of the oily waste as a whole to be reduced by increasing the oily sludge content, and the calorie content of the oily waste as a whole to be increased by reducing the oily sludge content. This allows the temperature inside the rotary kiln 8 to be more reliably adjusted. As a result, the efficiency of incineration of oily waste can be improved.

[0058] According to this embodiment, in the mixing step, at least one of the second oil-containing sludge stored in the second oil-containing sludge storage tank 21 and the dewatered scum cake stored in the dewatered scum cake storage tank 22 is used as oil sludge and mixed with the first oil-containing sludge to produce oily waste. This ensures the amount of oily sludge necessary to adjust the mixing ratio. This makes it possible to further improve the efficiency of incineration of oily waste.

[0059] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Furthermore, the present invention can be embodied in various novel forms in addition to the above-described embodiments. Therefore, various omissions, substitutions, and modifications are possible in the above-described embodiments without departing from the spirit and scope of the present invention. Such novel forms and modifications are included within the scope and spirit of the present invention, as well as within the scope of the inventions set forth in the claims and equivalents of the inventions set forth in the claims. [Example]

[0060] In Example 1, when oily waste was incinerated, the relationship between the mixing ratio r of the oily sludge and the first oil-containing sludge of the oily waste and the furnace wall temperature of the rotary kiln was examined.

[0061] Table 1 shows the average values ​​and fluctuation ranges of the oil content of the first oil-containing sludge and oil sludge used in Example 1. The oil content was measured by the Soxhlet extraction / gravimetric method using hexane as a solvent for the dried samples. The oil sludge of the present invention is not limited to sludge recovered by solid-liquid separation in wastewater treatment, and sludge from other generation processes may be used as the oil sludge as long as it generates less clinker when incinerated alone than when the first oil-containing sludge is incinerated alone.

[0062] [Table 1]

[0063] 4 is a graph in Example 1, with the horizontal axis representing the number of days of operation and the vertical axis representing the furnace wall temperature and the ratio of first oil-containing sludge to oil sludge. The vertical axis on the left represents the furnace wall temperature, shown as a line graph. The vertical axis on the right represents the ratio of first oil-containing sludge to oil sludge, shown as a bar graph. The furnace wall temperature was measured at two points: one 4 m away from the burner of the rotary kiln (4 m point) and the other 7 m away from the burner (7 m point).

[0064] As shown in Figure 4, in the first period from the first day to the eighth day of operation, the mixing ratio r1 of the first oil-containing sludge to the oil sludge was 1:2, in the second period from the 9th day to the 28th day of operation, the mixing ratio r of the first oil-containing sludge to the oil sludge was 1:1, in the third period from the 29th day to the 38th day of operation, the mixing ratio r of the first oil-containing sludge to the oil sludge was 2:1, and in the fourth period from the 39th day to the 47th day of operation, the mixing ratio r of the first oil-containing sludge to the oil sludge was 1:1.

[0065] Table 2 shows the clinker generation status for each period. The clinker generation status was measured by measuring the thickness of the clinker accumulated on the furnace wall.

[0066] [Table 2]

[0067] As shown in Figure 4 and Table 2, during the first period when the mixing ratio r of the first oil-containing sludge to the oil-containing sludge was 1:2, the furnace wall temperature was maintained at less than 1000°C. No clinker deposition was observed during the first period. Also, during the first period, the average furnace wall temperature at the 4 m point was 586°C, and the average furnace wall temperature at the 7 m point was 603°C.

[0068] During the second period, when the mixing ratio r of the first oil-containing sludge to the oil-containing sludge was 1:1, the furnace wall temperature remained below 1000°C. No clinker accumulation was observed during the second period. Also, during the second period, the average furnace wall temperature at the 4m point was 777°C, and the average furnace wall temperature at the 7m point was 816°C.

[0069] During the third period, when the mixing ratio r of the first oil-containing sludge to the oil-containing sludge was 2:1, the furnace wall temperature was confirmed to be over 1000°C. During the third period, clinker had accumulated to a depth of 7 cm on the furnace wall. Also during the third period, the average furnace wall temperature at the 4 m point was 918°C, and the average furnace wall temperature at the 7 m point was 922°C.

[0070] In the fourth period, when the mixing ratio r of the oil sludge to the first oil-containing sludge was 1:1, it was confirmed that the furnace wall temperature was below 1000°C. Furthermore, in the fourth period, the clinker deposition situation was similar to that in the third period, and no new clinker deposition was confirmed. Furthermore, in the fourth period, the average furnace wall temperature at the 4 m point was 891°C, and the average furnace wall temperature at the 7 m point was 879°C.

[0071] Fig. 5 is a graph in which the horizontal axis represents the ratio of the first oil-containing sludge to the sum of the first oil-containing sludge and the oil sludge, and the vertical axis represents the furnace wall temperature in Example 1. As shown in Fig. 5, it was confirmed that the furnace wall temperature tended to increase as the amount of the first oil-containing sludge increased.

[0072] From the above results, when incinerating oily waste, it is possible to adjust the furnace wall temperature by changing the mixing ratio r of the first oil-containing sludge and the oil sludge. In particular, as shown in the results for periods 1 to 3, it is possible to increase the average furnace wall temperature by reducing the oil sludge. Furthermore, as shown in the results for periods 3 and 4, it is possible to decrease the average furnace wall temperature by increasing the oil sludge.

[0073] In this example, since clinker accumulation was confirmed during the third period when the furnace wall temperature was confirmed to be 1000°C or higher, the control temperature was set to 1000°C. The control temperature may be set based on a predetermined threshold for the amount of clinker accumulation. The control temperature may be set based on the relationship between the temperature inside the rotary kiln and clinker generation, in accordance with the respective operating conditions. The mixing ratio may be changed when the furnace wall temperature is measured to exceed the control temperature once, when the furnace wall temperature is measured to exceed the control temperature multiple times, or when the average furnace wall temperature exceeds the control temperature. [Example]

[0074] In Example 2, the number of times the rotary kiln was shut down to remove clinker generated during the incineration of oily waste containing first oil-containing sludge and oil sludge was evaluated for a comparative example and an example of the present invention. The rotary kiln was operated for three years, and the number of times the rotary kiln was shut down to remove clinker generated during the incineration of oily waste containing first oil-containing sludge and oil sludge was evaluated. In the comparative example, the mixing ratio r of the first oil-containing sludge to the oil sludge of the oily waste was kept constant at 2:1, regardless of the rotary kiln wall temperature, and feedback operation was not performed. In the example of the present invention, the mixing ratio r of the first oil-containing sludge to the oil sludge was adjusted and mixed based on the rotary kiln wall temperature, with reference to the control temperature, and feedback operation was performed. In particular, when the rotary kiln wall temperature exceeded 1000°C, the mixing ratio r was adjusted to increase the amount of oil sludge relative to the first oil-containing sludge, and the temperature inside the rotary kiln was adjusted. Table 3 shows the results of the number of times the rotary kiln was shut down. The number of times the flame was extinguished shown in the table does not include times when the rotary kiln was stopped (extinguished) for regular maintenance.

[0075] [Table 3]

[0076] As shown in Table 3, the number of times flame extinction occurred was 0 in the inventive examples, while it was 2 or 3 in the comparative examples, meaning that the number of times flame extinction occurred was reduced in the inventive examples. In the inventive examples, there was almost no clinker accumulation, whereas in the comparative examples, clinker accumulated to a depth of 15 cm to 20 cm on the furnace wall of the rotary kiln in all three years from the first to the third.

[0077] In this example, the amount of oil-containing sludge mixed with the first oil-containing sludge was adjusted based on the temperature measured during the incineration process, referring to a preset control temperature. The oil-containing sludge and oil-containing sludge were separated in advance, and the amount of oil-containing sludge mixed was adjusted in response to fluctuations in the first oil-containing sludge. Then, feedback operation was performed to adjust the temperature inside the rotary kiln by incinerating the oily waste after adjusting the mixture ratio. This allows immediate on-site response to sudden increases or decreases in the temperature inside the rotary kiln, even for first oil-containing sludge whose oil concentration is unknown. Therefore, simply by separating the first oil-containing sludge and oil-containing sludge in advance, clinker adhesion can be suppressed without installing new equipment. As a result, the incineration efficiency of oily waste can be improved. [Explanation of symbols]

[0078] 100: Oily waste incineration system 1: First oil-containing sludge storage tank 2: Oil sludge storage tank 21: Second oil-containing sludge storage tank 22: Dewatered scum cake storage tank 4: Mixing tank 5: Waste oil storage tank 6:Transfer pipe 7: Feeding device 71: Input pipe 72: Input pipe 73: Saucer 74: Injection part 8: Rotary kiln 81: Rotating drum 82: Burner 83: Peephole 84: Ash discharge outlet 85: Gas outlet 86:Thermometer 9: Gas processing equipment

Claims

1. A method for incinerating oily waste using a rotary kiln, comprising: a control temperature setting step of setting a control temperature of the rotary kiln based on a previously acquired relationship between the temperature in the rotary kiln and the generation of clinker; a mixing step of generating oily waste by mixing first oil-containing sludge stored in a first oil-containing sludge storage tank with oil-containing sludge stored in the oil-containing sludge storage tank and generating less clinker when incinerated alone than when the first oil-containing sludge is incinerated alone; an incineration step of incinerating the oily waste in the rotary kiln and measuring the temperature inside the rotary kiln; a mixing ratio setting step of setting a mixing ratio of the first oil-containing sludge and the oil-containing sludge based on the temperature measured in the incineration step with reference to the control temperature, In the mixing step, the first oil-containing sludge and the oil-containing sludge are mixed to have a mixing ratio set in the mixing ratio setting step, thereby generating oily waste; In the incineration process, the oily waste is incinerated after adjusting the mixture ratio. A method for incinerating oily waste, comprising:

2. In the mixing ratio setting step, when the temperature measured in the incineration step is equal to or higher than the control temperature, the mixing ratio of the oily waste incinerated in the incineration step is set to a mixing ratio in which the oily sludge is increased more than the mixing ratio of the oily waste incinerated in the incineration step.

2. The method for incinerating oily waste according to claim 1, wherein:

3. In the mixing step, the oil-containing sludge having a lower oil content than the first oil-containing sludge is mixed.

3. The method for incinerating oily waste according to claim 1 or 2, wherein:

4. In the mixing step, at least one of the second oil-containing sludge stored in the second oil-containing sludge storage tank and the dehydrated scum cake stored in the dehydrated scum cake storage tank is used as the oil sludge, and is mixed with the first oil-containing sludge to generate oily waste. The method for incinerating oily waste according to any one of claims 1 to 3, characterized in that:

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