Operating method for combustion treatment facility

Abstract

To provide an operating method for a combustion treatment facility capable of continuously treating floating matters and having high removal efficiency.SOLUTION: An operating method is for a combustion treatment facility. The combustion treatment facility includes: a combustion facility for incinerating treated objects; a transportation facility for carrying out generated combustion ash from the combustion facility; and an exhaust gas treatment facility for removing dust and soot included in exhaust gas generated from the combustion facility by using cleaning water. The transportation facility includes a water tank for storing water and a conveyor disposed while partially submerged in the water in the water tank. The method includes: a first step of sending part or all of exhaust gas treatment water including floating matters generated from the exhaust gas treatment facility to the transportation facility; and a second step of precipitating the floating matters in the conveyor and carrying out them from the water in the water tank together with the combustion ash.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for operating a combustion treatment facility, and more particularly to an operating method for efficiently treating suspended solids generated in the process of treating exhaust gas from a combustion facility. [Background technology]

[0002] Waste electronic and electrical product parts, general household garbage, shredder dust, waste plastics, wood waste, paper waste, rubber waste, fiber waste, animal and plant residues, infectious waste, waste acid, waste alkali, waste oil, mud, industrial waste, etc. have traditionally been incinerated in combustion equipment consisting of a rotary kiln furnace, a stoker furnace, a secondary combustion furnace, etc. The soot and dust (also called "dust") contained in the exhaust gas generated by combustion can be removed by filters or with wash water in the exhaust gas treatment equipment.

[0003] When dust is removed using wash water, the wash water can be recycled and is therefore recovered as circulating process water. The dust is recovered as suspended solids (SS) contained in the circulating process water, and some of it is deposited in the lower tank of the washing tower (equipment for removing SS using wash water). If there is any residue, it is sent to the wastewater treatment process by bleed-off.

[0004] The exhaust gas treatment equipment can also be equipped with a cooling tower that sprays cooling water onto the exhaust gas generated by the combustion equipment to cool it. In that case, the cooling water sprayed by the cooling tower is stored in a separate tank installed at the bottom of the cooling tower, or is stored together in the lower tank of the scrubbing tower. The suspended solids that accumulate in the lower tank of the scrubbing tower are mainly removed from the system by vacuum.

[0005] Meanwhile, the ash generated by the incineration process is dropped into a water tank that contains water. A chain conveyor for transporting the ash is placed in the tank, partially submerged, and carries the ash out. The ash that is carried out can be stored in a storage facility such as an ash yard.

[0006] As an example of a treatment facility having such a configuration, Patent Document 1 (JP 2018-169127 A) discloses a combustion treatment facility including a rotary kiln furnace, which is a first combustion furnace that heats the material to be treated to pyrolyze and gasify it, a stoker furnace, which is a second combustion furnace connected to the downstream side of the rotary kiln furnace, a secondary combustion furnace that completely combusts the pyrolysis gas gasified in the rotary kiln furnace and the combustion exhaust gas generated in the stoker furnace, a cooling tower that sprays cooling water on the exhaust gas generated in the secondary combustion furnace to cool it, and a washing tower that washes the exhaust gas cooled in the cooling tower. The cooling water sprayed in the cooling tower and the washing water sprayed in the washing tower are stored in the lower part of the washing tower as circulating water. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-169127 A Summary of the Invention [Problem to be solved by the invention]

[0008] In conventional suspended solids treatment equipment, the lower tank of the washing tower has the role of multiple treatment processes, such as accumulating the process circulating water containing suspended solids, separating the suspended solids from the process circulating water (accumulating the supernatant), and removing the suspended solids, so there is a problem that the treatment capacity is easily reached. If the amount of suspended solids bleed-off from the lower tank increases, the amount of suspended solids sent to the wastewater treatment process increases, which increases the burden on the wastewater treatment equipment. Therefore, a method that can treat suspended solids more efficiently is needed.

[0009] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide, in one embodiment, a method for operating a combustion treatment facility that can continuously treat suspended solids and achieve high removal efficiency. [Means for solving the problem]

[0010] As a result of intensive research, the present inventors have found that the amount of suspended solids treated can be improved and the above-mentioned problems can be solved by transporting a part or all of the exhaust gas treatment water containing suspended solids together with the ash out of the system by a transport means. The present invention has been completed based on the above findings, and is exemplified below.

[0011] [1] A method for operating a combustion treatment facility, comprising the steps of: The combustion treatment facility includes a combustion equipment for incinerating the material to be treated, a transport equipment for transporting ash generated from the combustion equipment, and an exhaust gas treatment equipment for removing soot and dust contained in the exhaust gas generated from the combustion equipment with cleaning water, The transport facility includes a water tank that stores water, and a conveyor that is disposed with a portion of the conveyor submerged in the water tank; The method includes a first step of sending a part or all of exhaust gas treatment water containing suspended solids generated from the exhaust gas treatment facility to the transport facility; A second step of allowing the suspended solids to settle on the conveyor and removing them together with the ash from the water in the tank. [2] The combustion treatment facility further includes a concentration device for concentrating the suspended solids in the exhaust gas treatment water, The method for operating a combustion treatment facility described in [1], wherein the first step includes using the concentration equipment to separate the exhaust gas treatment water into a first treatment water in which the suspended solids are concentrated and a second treatment water in which the concentration of suspended solids is lower than that of the first treatment water, and sending the first treatment water to the transportation equipment. [3] The method for operating a combustion treatment facility described in [2], further comprising subjecting the second treated water to wastewater treatment. [4] The method for operating a combustion treatment facility described in [2] or [3], wherein the concentration equipment includes one or more selected from a liquid cyclone, a centrifuge, and a thickener. [5] The method for operating a combustion treatment facility according to any one of [1] to [4], wherein the second step includes sprinkling cleaning water onto the ash carried out of the water in the water tank by the conveyor. [6] A recycling method comprising carrying out the method for operating a combustion treatment facility described in any one of [1] to [5], and recovering valuable metals from the combustion ash and the suspended solids carried out of the water in the water tank by the conveyor. [7] The recycling method according to [6], wherein the suspended solids contain 6.0 mass% or more of Cu. Effect of the Invention

[0012] According to one embodiment of the present invention, it is possible to provide a method for operating a combustion treatment facility that can continuously treat suspended solids and achieve high removal efficiency. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a combustion treatment facility in one embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a facility configuration for performing a first step and a second step in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, an embodiment of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiment, and that appropriate changes and improvements in the design may be made based on the ordinary knowledge of a person skilled in the art without departing from the spirit of the present invention.

[0015] (1. Combustion treatment facility) The combustion treatment facility includes a combustion equipment for incinerating the material to be treated, a transport equipment for carrying out the ashes generated from the combustion equipment, and an exhaust gas treatment equipment for removing soot and dust contained in the exhaust gas generated from the combustion equipment with cleaning water. The combustion equipment is not particularly limited, but examples thereof include a combination of a rotary kiln furnace, a stoker furnace, and a secondary combustion furnace. The material to be treated is not particularly limited, but examples thereof include scrap parts of electronic and electrical products.

[0016] The transport facility for transporting the ash generated from the combustion facility includes a water tank and a conveyor that is partially submerged in the water tank. The ash generated by the incineration of the materials to be treated is dropped into the water in the water tank and transported by the conveyor. The transported ash can be stored in a storage facility such as an ash yard.

[0017] The specific configuration of the exhaust gas treatment equipment is not limited as long as it removes soot and dust contained in the exhaust gas generated from the combustion equipment using cleaning water, but typical examples include a cooling tower that cools the exhaust gas by spraying cooling water on it, and a cleaning tower that cleans the exhaust gas cooled in the cooling tower. The cooling water and / or cleaning water (hereinafter collectively referred to as "exhaust gas treatment water") generated from these equipment contains suspended matter consisting of soot and dust. The cooling water and / or cleaning water can be stored in separate tanks, or can be stored together in a single tank.

[0018] The suspended solids contained in the stored exhaust gas treatment water accumulate at the bottom of the tank and can be removed from the system mainly by vacuum. Meanwhile, in continuous treatment, the suspended solids that exceed the tank's treatment capacity (also called "bleed-off") can be sent to the wastewater treatment process within the plant.

[0019] 1 shows a schematic diagram of a combustion treatment facility according to one embodiment of the present invention. The combustion treatment facility 1 includes a rotary kiln furnace 2, a stoker furnace 3, and a secondary combustion furnace 4 as combustion equipment, a water tank 5 (shown as a dotted line) that stores water, and a chain conveyor 5a arranged partially submerged in the water in the water tank as transport equipment, and a cooling tower 6, a scrubbing tower 7, and a tank 8 below the scrubbing tower 7 as exhaust gas treatment equipment. The chain conveyor 5a may be replaced with another conveyor, such as a screw conveyor or a bucket conveyor.

[0020] The rotary kiln 2 is equipped with a cylindrical horizontal rotary furnace 2a, with an inlet 2b for feeding the material to be treated at one end and a discharge port (drop-out) 2c at the opposite end. The rotary furnace 2a is placed so as to be slightly inclined toward the discharge port 2c and can be rotated by a motor (not shown). A kiln burner 2d is placed near the inlet 2b, and it is possible to blow a flame into the furnace by burning fuel such as heavy oil, thereby heating the inside of the furnace.

[0021] The end face of the rotary furnace 2a on the discharge port 2c side is connected to the stoker furnace 3, and the material discharged from the discharge port 2c falls onto the fire grate 3a of the stoker furnace 3, which is movable by a cylinder 3b, and the pyrolysis gas is introduced into the secondary combustion furnace 4. A water tank 5 and a chain conveyor 5a are arranged below the stoker furnace 3. The pyrolysis gas is completely combusted by a secondary combustion furnace burner (not shown) provided in the secondary combustion furnace 4. In addition, the combustion exhaust gas generated when the material is incinerated in the stoker furnace 3 is also completely combusted together with the pyrolysis gas in the secondary combustion furnace 4. The secondary combustion furnace 4 is provided with combustion air supply nozzles (not shown) at equal intervals for supplying air for combustion. The exhaust gas treated in the secondary combustion furnace 4 is sent to the cooling tower 6, which is connected to the secondary combustion furnace 4 by a duct 4a, and then to the scrubbing tower 7, where it is collected by a wet electrostatic precipitator (not shown) and then exhausted into the atmosphere. The soot and dust contained in the exhaust gas is collected in tank 8 together with the washing water, and is included in the exhaust gas treatment water as suspended matter.

[0022] (2. Operation method of combustion treatment facility) The method for operating a combustion treatment facility of the present invention includes a first step of sending a part or all of exhaust gas treatment water containing suspended solids generated from the exhaust gas treatment facility to a conveying facility, and a second step of allowing the suspended solids to settle on a conveyor and carrying them out of the water in the tank together with the burned ash. Hereinafter, the embodiment shown in FIG. 1 will be described as an example.

[0023] Water is stored in the water tank 5 located at the bottom of the stoker furnace 3, and the water level is generally kept constant. A chain conveyor 5a is placed in the water of the water tank 5, and part of it is submerged. Therefore, after combustion processing, the ash is submerged and falls onto the chain conveyor 5a. The chain conveyor 5a transports the ash (from left to right in Figure 1) and carries it out of the system.

[0024] Here, in the method of this embodiment, the first step is carried out in which part or all of the exhaust gas treatment water containing suspended matter is sent to the chain conveyor 5a. As described above, the suspended matter contained in the exhaust gas treatment water is deposited at the bottom of the tank 8 and can be removed from the system mainly by vacuum. However, in continuous treatment, if the suspended matter that exceeds the treatment capacity of the tank 8 is treated as bleed-off and discharged, the burden on the wastewater treatment equipment increases. Specifically, in order to treat the suspended matter in the wastewater treatment equipment, it is necessary to separate the suspended matter from the wastewater by performing solid-liquid separation using a filter press or the like. When the amount of suspended matter increases, it may exceed the capacity of this solid-liquid separation. Therefore, by sending the exhaust gas treatment water to the chain conveyor 5a and carrying out the suspended matter together with the ashes, the amount of suspended matter to be treated in the wastewater treatment equipment can be suppressed, and the increase in the burden on the wastewater treatment equipment can be suppressed. Note that a part of the exhaust gas treatment water can be treated within the treatment capacity of the tank 8, so that usually it is not necessary to send all of the exhaust gas treatment water to the chain conveyor 5a, and only a part of it is sufficient.

[0025] When the exhaust gas treatment water is sent to the chain conveyor 5a, the suspended solids contained therein settle onto the chain conveyor 5a by gravity and are removed from the water in the water tank 5 together with the ashes (second process). In this way, the suspended solids are removed from the water by the chain conveyor 5a, whereby the suspended solids are separated from the exhaust gas treatment water.

[0026] Here, when the exhaust gas treatment water is sent to the chain conveyor 5a, it is preferable to concentrate the suspended matter. By concentrating the suspended matter, the amount of exhaust gas treatment water sent to the chain conveyor 5a can be reduced. In addition to the exhaust gas treatment water, normal cleaning water is also supplied to the water tank 5, which causes the water level to rise. On the other hand, the evaporation of moisture due to the heat of the burned ash and the moisture carried out together with the burned ash by the chain conveyor 5a are causes of the water level to drop. If a large amount of exhaust gas treatment water is supplied to the water tank 5, the water level in the water tank 5 may rise and exceed the storage capacity of the water tank 5. In that case, some of the suspended matter leaves the water tank 5 together with the moisture (also called "overflow"). The overflow can be concentrated again to circulate the suspended matter to the chain conveyor 5a, or stored in a separate tank to allow the suspended matter to settle, but it is preferable to reduce the overflow as much as possible from the viewpoint of improving the treatment efficiency. Therefore, the amount of overflow can be reduced by concentrating the exhaust gas treatment water.

[0027] 2 shows an equipment configuration for performing the first and second steps in one embodiment of the present invention. The combustion treatment facility further includes a concentration equipment 9 for concentrating suspended solids in the exhaust gas treatment water. In the first step, the concentration equipment 9 is used to separate the exhaust gas treatment water into a first treated water in which suspended solids have been concentrated and a second treated water in which the concentration of suspended solids is lower than that of the first treated water, and the first treated water is sent to a chain conveyor 5a.

[0028] The concentration equipment 9 is not limited in its specific configuration as long as it can concentrate suspended solids, but can typically include one or more selected from a liquid cyclone, a centrifuge, and a thickener. A liquid cyclone is a device that separates solids and liquids by centrifugal force by supplying a sample to a cylindrical container in the circumferential direction at high speed, causing a rotational motion. A centrifuge is a device that separates samples based on differences in density using centrifugal force by rotating the sample at high speed. A thickener is a device that separates suspended solids in a liquid by settling them under gravity.

[0029] If the first treated water in which the suspended solids are concentrated is sent to the chain conveyor 5a, the amount of overflow can be reduced, and the treatment efficiency can be improved in the continuous treatment, which is more preferable. In addition, by concentrating the exhaust gas treatment water, the flow rate of the treated water sent to the chain conveyor 5a is reduced, and the time from the inflow of the treated water to the overflow is extended, and sufficient time for the suspended solids to settle is secured. In addition, in order to secure time for the suspended solids to settle, it is preferable to send the first treated water from the upstream side (left side in FIG. 2) of the chain conveyor 5a. On the other hand, the second treated water can be sent to a wastewater treatment. Since the concentration of suspended solids in the second treated water is low, the burden on the wastewater treatment is low. The wastewater treatment is not particularly limited, but may be, for example, a comprehensive wastewater treatment. The drainage means is not particularly limited, but typically a pump can be used.

[0030] In the second step, cleaning water can be sprinkled on the ashes carried out of the water tank 5 by the chain conveyor 5a. By sprinkling the cleaning water, the chain conveyor 5a can be cleaned to prevent adhesion of the ashes and the like, thereby extending the service life of the chain conveyor 5a.

[0031] In addition, since it is assumed that the first and second steps are carried out simultaneously in the continuous treatment, the order of the first and second steps is not limited in the method for operating a combustion treatment facility of the present invention.

[0032] The burnt ash and floating matter carried out of the water tank 5 by the chain conveyor 5a may contain valuable metals. In particular, when the material to be incinerated is scrap parts of electronic and electrical products, valuable metals are contained in a significant amount. Therefore, in another aspect, the present invention relates to a recycling method including recovering valuable metals from the burnt ash and floating matter carried out of the water tank 5 by the chain conveyor 5a. When all the floating matter is treated in a wastewater treatment facility as in the conventional technology, in order to recover valuable metals contained in the floating matter, a task of transporting the floating matter after solid-liquid separation to a metal recovery process is generated. On the other hand, by sending the exhaust gas treatment water to the chain conveyor 5a and carrying out the floating matter together with the burnt ash, the floating matter can be directly transported to the metal recovery process together with the burnt ash, which is preferable. The specific means for recovering valuable metals is not limited, but examples include a method using a melting furnace such as a flash furnace or a converter.

[0033] Although the type and amount of valuable metals contained in the suspended solids are not particularly limited, when the Cu content is 6.0 mass% or more, it is particularly economically preferable to recover them. Note that the content is measured not for the burned ash but for the suspended solids collected from the exhaust gas treatment water. EXAMPLES

[0034] Example 1 An incineration treatment facility was constructed with the configuration shown in Figures 1 and 2, and electronic and electrical product part scraps were incinerated as the material to be treated, and continuous treatment was carried out. The Cu content of the SS contained in the exhaust gas treatment water was measured and found to be 8.6 mass%. The SS was concentrated in the exhaust gas treatment water using a liquid cyclone and a centrifugal separator in combination, and the first treated water with concentrated SS (SS concentration 16,231 mg / L) was poured from the left side of the chain conveyor 5a over a distance of 3.3 m. 3 / h, and the washing water is sent from the right side at a flow rate of 0.9m 3 / h (total flow rate 4.2m 3 / h, SS concentration 12,909mg / L). The total flow rate of the water evaporated by the heat of the burnt ash and the water carried away from the burnt ash from the chain conveyor 5a is 3.0m 3 / h, and 1.2m 3 The flow rate of 1000 ml / h was circulated as overflow to the exhaust gas treatment equipment after cooling tower 6. The SS concentration in the overflow was measured and found to be 2,186 mg / L.

[0035] The SS concentration in the overflow was significantly lower than that in the first treated water, which indicates that the SS had sufficiently settled. Furthermore, calculations of the amount of SS flowing into and out of the chain conveyor 5a revealed that the inflow amount was approximately 54 kg / h, while the amount contained in the overflow was approximately 3 kg / h, indicating that the remaining 51 kg / h was transported out of the system. The SS recovery rate was approximately 95%.

[0036] Example 2 The flow rate of the first treated water is 4.5m 3 The combustion treatment facility was operated under the same conditions as in Example 1, except that the flow rate of the overflow from the chain conveyor 5a was changed to 2.4 m 3 / h, but when the SS concentration in the overflow was measured, it was 1,641 mg / L.

[0037] The SS concentration in the overflow was significantly lower than that in the first treated water, which indicates that the SS had sufficiently settled. Furthermore, calculations of the amount of SS flowing into and out of the chain conveyor 5a revealed that the inflow amount was approximately 86 kg / h, while the amount contained in the overflow was approximately 4 kg / h, indicating that the remaining 82 kg / h was transported out of the system. The SS recovery rate was approximately 95%.

[0038] From the above Examples 1 and 2, it is understood that the suspended solids can be efficiently removed by sending the exhaust gas treated water to the chain conveyor 5a. It is also understood that a high recovery rate can be obtained by concentrating the exhaust gas treated water. [Explanation of symbols]

[0039] 1. Combustion treatment facility 2 Rotary kiln furnace 3. Stoker Furnace 4 Secondary Combustion Furnace 5. Aquarium 5a Chain conveyor 6 cooling tower 7. Washing Tower 8. Tank 9 Concentration equipment

Claims

1. A method for operating a combustion treatment facility, comprising the steps of: The combustion treatment facility includes a combustion equipment for incinerating the material to be treated, a transport equipment for transporting ash generated from the combustion equipment, and an exhaust gas treatment equipment for removing soot and dust contained in the exhaust gas generated from the combustion equipment with cleaning water, The transport facility includes a water tank that stores water, and a conveyor that is disposed with a portion of the conveyor submerged in the water tank; The method includes a first step of sending a part or all of exhaust gas treatment water containing suspended solids generated from the exhaust gas treatment facility to the transport facility; and a second step of allowing the suspended solids to settle on the conveyor and removing them together with the ash from the water in the water tank.

2. The combustion treatment facility further includes a concentration device for concentrating the suspended solids in the exhaust gas treatment water, 2. The method of operating a combustion treatment facility as described in claim 1, wherein the first step includes using the concentrating equipment to separate the exhaust gas treatment water into a first treatment water in which the suspended solids are concentrated and a second treatment water in which the concentration of the suspended solids is lower than that of the first treatment water, and sending the first treatment water to the transport equipment.

3. The method for operating a combustion treatment facility according to claim 2 , further comprising subjecting the second treated water to wastewater treatment.

4. The method for operating a combustion treatment facility according to claim 2 or 3, wherein the thickening equipment includes one or more selected from the group consisting of a liquid cyclone, a centrifuge, and a thickener.

5. 3. The method for operating a combustion treatment facility according to claim 1 or 2, wherein the second step includes sprinkling cleaning water on the ash carried out of the water in the water tank by the conveyor.

6. 3. A recycling method comprising carrying out the method for operating a combustion treatment facility according to claim 1 or 2, and recovering valuable metals from the burnt ash and the suspended solids carried out of the water in the water tank by the conveyor.

7. The recycling method according to claim 6, wherein the suspended solids contain 6.0 mass % or more of Cu.

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