Operating methods for incineration treatment facilities

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 an operation method of a combustion treatment facility. In particular, the present invention relates to an operation method for efficiently treating suspended substances generated in the exhaust gas treatment process from combustion equipment.

Background Art

[0002] Parts scraps of electronic and electrical products, general household waste, shredder dust, waste plastics, wood chips, paper scraps, rubber scraps, fiber scraps, animal and plant residues, infectious waste, waste acids, waste alkalis, waste oils, mud, industrial waste, etc. have been conventionally incinerated by combustion equipment composed of a rotary kiln furnace, a stoker furnace, a secondary combustion furnace, etc. Dust (also called "dust") contained in the exhaust gas generated by combustion can be removed by a filter or removed by washing water in an exhaust gas treatment facility.

[0003] When removing dust with washing water, since the washing water can be recycled, it is recovered as process circulating water, and the dust is recovered as suspended solids (SS) contained in the process circulating water. After that, a part of it accumulates in the lower tank of the washing tower (SS removal equipment by washing water), and if there is any remaining, it is sent to the wastewater treatment process by bleed-off.

[0004] In addition, the exhaust gas treatment facility can also include a cooling tower that sprays cooling water to cool the exhaust gas generated in the combustion equipment. In that case, the cooling water sprayed in the cooling tower is stored in a separate tank provided at the lower part of the cooling tower or stored together in the lower tank of the washing tower. The suspended substances deposited in the lower tank of the washing tower are mainly removed outside the system by vacuum.

[0005] On the other hand, the ash generated by the incineration process is dropped into a water tank. Inside the tank, a chain conveyor is positioned with a portion submerged in water to transport the ash, which is then removed from the tank. The removed ash can then be stored in storage facilities such as an ash yard.

[0006] As an example of a processing facility with such a configuration, Patent Document 1 (Japanese Patent Application Publication No. 2018-169127) discloses a combustion processing facility that includes a rotary kiln furnace, which is a first combustion furnace that gasifies the material to be processed by thermal decomposition by heating; a stoker furnace, which is a second combustion furnace connected downstream of the rotary kiln furnace; a secondary combustion furnace that completely combusts the thermal decomposition gas gasified in the rotary kiln furnace and the combustion exhaust gas generated in the stoker furnace; a cooling tower that cools the exhaust gas generated in the secondary combustion furnace by spraying cooling water on it; and a scrubbing 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 scrubbing tower are stored as circulating water at the bottom of the scrubbing tower. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2018-169127 [Overview of the project] [Problems that the invention aims to solve]

[0008] Conventional suspended solids (FSS) treatment systems have a problem in that the lower tank of the scrubbing tower serves multiple treatment processes, including the accumulation of process circulating water containing suspended solids, the separation of suspended solids from the process circulating water (accumulation of the supernatant), and the removal of suspended solids, making it prone to reaching the limits of its treatment capacity. As the amount of suspended solids bleed off from the lower tank increases, the amount of suspended solids sent to the wastewater treatment process also increases, thus increasing the burden on the wastewater treatment equipment. Therefore, there is a need for a method that can treat suspended solids with higher efficiency.

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

[0010] As a result of diligent research by the inventors, it has been found that by transporting a portion or all of the exhaust gas treatment water containing suspended solids, along with the ash, out of the system using a transport means, the amount of suspended solids that can be treated can be improved, thereby solving the above problem. The present invention was completed based on the above findings and is illustrated below.

[0011] [1] A method for operating a combustion treatment facility, The aforementioned incineration facility includes a combustion unit for incinerating the material to be processed, a transport unit for transporting the ash generated from the combustion unit, and an exhaust gas treatment unit for removing soot contained in the exhaust gas generated from the combustion unit with washing water. The transport equipment includes a water tank that stores water and a conveyor that is positioned with a portion of it submerged in the water tank. The method comprises a first step of sending some or all of the exhaust gas treated water containing suspended solids generated from the exhaust gas treatment equipment to the conveying equipment, A method for operating a combustion treatment facility, comprising a second step of allowing the suspended material to settle on the conveyor and transporting it out of the water in the tank together with the charred ash. [2] The combustion treatment facility further includes a concentration facility for concentrating the suspended solids in the exhaust gas treatment water, The method for operating a combustion treatment facility according to [1], the first step comprising using the concentration equipment to separate the exhaust gas treated water into first treated water in which the suspended solids are concentrated and second treated water in which the concentration of the suspended solids is lower than that of the first treated water, and sending the first treated water to the conveying equipment. [3] A method for operating a combustion treatment facility according to [2], comprising performing wastewater treatment on the second treated water. [4] The concentration equipment includes one or more selected from a liquid cyclone, a centrifuge, and a thickener, and is the operation method of the combustion treatment facility according to [2] or [3]. [5] The second step includes spraying washing water on the ash removed from the water in the water tank by the conveyor, and is the operation method of the combustion treatment facility according to any one of [1] to [4]. [6] A recycling method including recovering valuable metals from the ash and the suspended substances removed from the water in the water tank by the conveyor by implementing the operation method of the combustion treatment facility according to any one of [1] to [5]. [7] The suspended substance contains 6.0% by mass or more of Cu, and is the recycling method according to [6].

Advantages of the Invention

[0012] According to an embodiment of the present invention, it is possible to provide an operation method of a combustion treatment facility that can continuously treat suspended substances and has high removal efficiency.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing a schematic view of a combustion treatment facility in an embodiment of the present invention. [Figure 2] It is a diagram showing the equipment configuration for performing the first step and the second step in an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0014] Next, embodiments 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 embodiments, and design changes, improvements, etc. can be appropriately made based on the ordinary knowledge of those 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 device for incinerating the object to be treated, a conveying device for carrying out the ash generated from the combustion device, and an exhaust gas treatment device for removing dust contained in the exhaust gas generated from the combustion device with washing water. The combustion device is not particularly limited, and examples include a combination of a rotary kiln furnace, a stoker furnace, and a secondary combustion furnace. The object to be treated is not particularly limited, and examples include parts scraps of electronic and electrical products.

[0016] The conveying device for carrying out the ash generated from the combustion device includes a water tank storing water and a conveyor arranged in a state where a part of it is submerged in the water tank. The ash generated by the incineration of the object to be treated is dropped into the water in the water tank and carried out by the conveyor. The carried-out ash can be stored in a storage facility such as an ash yard.

[0017] The specific configuration of the exhaust gas treatment device is not limited as long as it can remove the dust contained in the exhaust gas generated from the combustion device with washing water. Typically, it includes a cooling tower for spraying cooling water on the exhaust gas to cool it and a washing tower for washing the exhaust gas cooled by the cooling tower. The cooling water and / or washing water (hereinafter collectively referred to as "exhaust gas treatment water") generated from these facilities contains suspended substances consisting of dust. The cooling water and / or washing water can be stored in separate tanks or in a single tank together.

[0018] The suspended substances contained in the stored exhaust gas treatment water accumulate at the bottom of the tank and can be mainly removed outside the system by vacuum. On the other hand, in continuous treatment, the excess suspended substances beyond the treatment capacity of the tank (also called "bleed-off") can be sent to the wastewater treatment process in the factory.

[0019] Figure 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) containing water and a chain conveyor 5a positioned partially submerged in the water in the water tank as conveying equipment, and a cooling tower 6, a washing tower 7, and a tank 8 at the bottom of the washing tower 7 as exhaust gas treatment equipment. The chain conveyor 5a may be replaced with other conveyors, such as a screw conveyor or a bucket conveyor.

[0020] The rotary kiln furnace 2 is equipped with a cylindrical, horizontally positioned rotary furnace 2a, with an inlet 2b for feeding materials to be processed on one end face and an outlet (discharge port) 2c on the opposite end face. The rotary furnace 2a is positioned so as to be slightly inclined toward the outlet 2c and is rotatable by a motor (not shown). A kiln burner 2d is positioned near the inlet 2b, and by burning fuel such as heavy oil, it blows a flame into the furnace, thereby heating the inside of the furnace.

[0021] The end face of the rotary furnace 2a on the outlet 2c side is connected to the stoker furnace 3. The material to be processed discharged from the outlet 2c falls onto the 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 located below the stoker furnace 3. The pyrolysis gas is then completely combusted by a secondary combustion furnace burner (not shown) installed in the secondary combustion furnace 4. In addition, the combustion exhaust gas generated when the material to be processed is incinerated in the stoker furnace 3 is also completely combusted in the secondary combustion furnace 4 together with the pyrolysis gas. The secondary combustion furnace 4 is provided with combustion air supply nozzles (not shown) at equal intervals to supply combustion air. The exhaust gas processed in the secondary combustion furnace 4 is then sent from a cooling tower 6, which is connected to the secondary combustion furnace 4 by a duct 4a, to a washing tower 7, where it is further collected by a wet electrostatic precipitator (not shown) before being exhausted into the atmosphere. The particulate matter contained in the exhaust gas is collected in tank 8 along with the washing water and included in the exhaust gas treatment water as suspended solids.

[0022] (2. Operating procedures for incineration facilities) The method for operating a combustion treatment facility according to the present invention includes a first step of sending some or all of the exhaust gas treatment water containing suspended solids generated from the exhaust gas treatment equipment to a conveying equipment, and a second step of allowing the suspended solids to settle on a conveyor and transporting them out of the water tank together with the charred ash. The embodiment shown in Figure 1 will be described below as an example.

[0023] A water tank 5, located at the bottom of the stoker furnace 3, stores water, and its water level is generally kept constant. A chain conveyor 5a is positioned in the water of the water tank 5, with a portion of it submerged. Therefore, the ash produced after combustion is submerged and falls onto the chain conveyor 5a. The chain conveyor 5a transports the ash (from left to right in Figure 1) and removes it from the system.

[0024] In this embodiment, a first step is performed in which some or all of the exhaust gas treated water containing suspended solids is sent to the chain conveyor 5a. As mentioned above, suspended solids contained in the exhaust gas treated water accumulate at the bottom of the tank 8 and can be removed from the system mainly by vacuum. However, in continuous processing, if the suspended solids exceeding the processing capacity of the tank 8 are treated as wastewater by bleed-off, the burden on the wastewater treatment equipment increases. Specifically, in order to treat suspended solids in the wastewater treatment equipment, it is necessary to separate the suspended solids from the wastewater by performing solid-liquid separation using a filter press or the like. If the amount of suspended solids is large, it may exceed the capacity of this solid-liquid separation. Therefore, by sending the exhaust gas treated water to the chain conveyor 5a and transporting the suspended solids together with the ash, the amount of suspended solids that need to be treated in the wastewater treatment equipment can be suppressed, and the increased burden on the wastewater treatment equipment can be suppressed. Note that since some of the exhaust gas treated water can be treated within the processing capacity of the tank 8, it is usually not necessary to send all of the exhaust gas treated water to the chain conveyor 5a, and only some of it is required.

[0025] When the exhaust gas treated water is sent to the chain conveyor 5a, the suspended solids contained within it settle onto the chain conveyor 5a due to gravity and are removed from the water in the tank 5 along with the charred ash (second step). In this way, the suspended solids are removed from the water by the chain conveyor 5a, thus separating them from the exhaust gas treated water.

[0026] Here, it is preferable to concentrate the suspended solids when sending the exhaust gas treated water to the chain conveyor 5a. By concentrating the suspended solids, the amount of exhaust gas treated water sent to the chain conveyor 5a can be reduced. In addition to the exhaust gas treated water, regular washing water is also supplied to the tank 5, which causes the water level to rise. On the other hand, evaporation of water due to the heat of the ash and water carried out with the ash by the chain conveyor 5a cause the water level to fall. If the amount of exhaust gas treated water supplied to the tank 5 is large, the water level in the tank 5 may rise and exceed the storage capacity of the tank 5. In that case, some of the suspended solids will separate from the tank 5 along with the water (also called "overflow"). Overflow can be reconcentrated and circulated back to the chain conveyor 5a, or stored in a separate tank to allow the suspended solids to settle, but from the viewpoint of improving treatment efficiency, it is preferable to reduce overflow as much as possible. Therefore, the amount of overflow can be reduced by concentrating the exhaust gas treated water.

[0027] Figure 2 shows the equipment configuration for performing the first and second steps in one embodiment of the present invention. The combustion treatment facility further includes a concentration unit 9 for concentrating suspended solids in the exhaust gas treated water. In the first step, the concentration unit 9 is used to separate the exhaust gas treated water into first treated water in which suspended solids are concentrated and 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 typically it may 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 generating rotational motion by supplying a sample at high speed in a cylindrical container in a circumferential direction. A centrifuge is a device that separates a sample by density difference using centrifugal force by rotating the sample at high speed. A thickener is a device that separates suspended solids in a liquid by allowing them to settle under gravity.

[0029] Sending the first treated water, in which suspended solids are concentrated, to the chain conveyor 5a reduces the amount of overflow, thereby improving treatment efficiency in continuous processing, which is preferable. Furthermore, by concentrating the exhaust gas treated water, the flow rate of treated water sent to the chain conveyor 5a is reduced, extending the time from the inflow of treated water to overflow, and ensuring sufficient time for suspended solids to settle. In order to ensure sufficient time for suspended solids to settle, it is preferable to send the first treated water from the upstream side of the chain conveyor 5a (left side in Figure 2). On the other hand, the second treated water can be sent to wastewater treatment. Since the concentration of suspended solids in the second treated water is low, the burden on wastewater treatment is low. The wastewater treatment is not particularly limited, but for example, it may be integrated wastewater treatment. The wastewater means is not particularly limited, but typically a pump can be used.

[0030] In the second step, the charred ash that has been removed from the water in the tank 5 by the chain conveyor 5a can be sprayed with washing water. By spraying with washing water, the chain conveyor 5a is cleaned, preventing the adhesion of charred ash and other substances, and extending the service life of the chain conveyor 5a.

[0031] In continuous processing, the first and second steps are expected to be performed simultaneously; therefore, the order of the first and second steps is not limited in the operation method of the combustion treatment facility of the present invention.

[0032] Furthermore, the ash and suspended solids removed from the water in the tank 5 by the chain conveyor 5a may contain valuable metals. In particular, when the materials to be incinerated are scrap parts of electronic and electrical products, valuable metals are present in significant amounts. Therefore, in another aspect, the present invention relates to a recycling method that includes recovering valuable metals from the ash and suspended solids removed from the water in the tank 5 by the chain conveyor 5a. In the case of conventional technology, where all suspended solids are treated in a wastewater treatment facility, recovering valuable metals contained in the suspended solids requires transporting the suspended solids after solid-liquid separation to a metal recovery process. On the other hand, by sending exhaust gas treated water to the chain conveyor 5a and removing the suspended solids together with the ash, the suspended solids can be directly transported to the metal recovery process together with the ash, which is preferable. The specific means for recovering valuable metals are not limited, but examples include methods using melting furnaces such as self-melting furnaces and converters.

[0033] The type and amount of valuable metals contained in the suspended solids are not particularly limited, but if they contain 6.0% by mass or more of Cu, recovery is particularly economically preferable. Note that this content should be measured from suspended solids collected from exhaust gas treated water, not from incinerated ash. [Examples]

[0034] (Example 1) The combustion treatment facility was configured as shown in Figures 1 and 2, and continuous processing was carried out by incinerating scrap electronic and electrical product parts as the material to be processed. The Cu content of the suspended solids (SS) contained in the exhaust gas treated water was measured and found to be 8.6 mass%. The SS was concentrated in the exhaust gas treated water using a liquid cyclone and a centrifuge, and the first treated water with concentrated SS (SS concentration 16,231 mg / L) was transported from the left side of the chain conveyor 5a in a 3.3 m³ container. 3 The water is supplied at a flow rate of / h, and the washing water is sprayed from the right side at a rate of 0.9m 3 Sent at a flow rate of / h (total flow rate 4.2m 3 ( / h, SS concentration 12,909 mg / L). From chain conveyor 5a, the total flow rate of water evaporated by the heat of the ash and the flow rate of water carried out from the ash is 3.0 m 3 / h, and furthermore 1.2m 3 The flow rate of / h was recirculated as overflow to the exhaust gas treatment equipment from cooling tower 6 onward. The SS concentration in the overflow was measured to be 2,186 mg / L.

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

[0036] (Example 2) The flow rate of the first treated water is 4.5 m 3 The combustion treatment facility was operated under the same conditions as in Example 1, except that the flow rate was changed to / h and the SS concentration in the first treated water was changed to 19,127 mg / L. The overflow flow rate from chain conveyor 5a was 2.4 m³. 3 The initial reading was / h, but when the SS concentration in the overflow was measured, it was found to be 1,641 mg / L.

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

[0038] From the above examples 1 and 2, it can be seen that suspended solids can be efficiently removed by sending exhaust gas treated water to the chain conveyor 5a. Furthermore, it can be seen that a high recovery rate can be obtained by concentrating the exhaust gas treated water. [Explanation of Symbols]

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

Claims

1. A method for operating a combustion treatment facility, The aforementioned incineration facility includes a combustion unit for incinerating the material to be processed, a transport unit for transporting the ash generated from the combustion unit, and an exhaust gas treatment unit for removing soot contained in the exhaust gas generated from the combustion unit with washing water. The transport equipment includes a water tank that stores water and a conveyor that is positioned with a portion of it submerged in the water tank. The method comprises a first step of sending some or all of the exhaust gas treated water containing suspended solids generated from the exhaust gas treatment equipment to the conveying equipment, The process includes a second step of allowing the suspended material to settle on the conveyor and transporting it out of the water in the tank together with the burnt ash. The combustion treatment facility further includes a concentration facility for concentrating the suspended solids in the exhaust gas treatment water, The first step is a method for operating a combustion treatment facility, comprising using the concentration equipment to separate the exhaust gas treated water into a first treated water in which the suspended solids are concentrated and a second treated water in which the concentration of the suspended solids is lower than that of the first treated water, and sending the first treated water to the conveying equipment.

2. A method for operating a combustion treatment facility according to claim 1, comprising performing wastewater treatment on the second treated water.

3. The method for operating a combustion treatment facility according to claim 1 or 2, wherein the concentration equipment includes one or more selected from a liquid cyclone, a centrifugal separator, and a thickener.

4. The method for operating a combustion treatment facility according to claim 1, wherein the second step includes sprinkling washing water on the ash that has been removed from the water in the tank by the conveyor.

5. A recycling method comprising recovering valuable metals from the incinerated ash and suspended matter transported from the water in the tank by the conveyor, by performing the operation method of the incineration treatment facility described in claim 1.

6. The recycling method according to claim 5, wherein the suspended material contains 6.0% by mass or more of Cu.

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