A method for reducing the generation rate of fly ash in a waste incineration waste heat boiler

Abstract

The present invention provides a method for reducing the generation rate of fly ash in a waste incineration waste heat boiler, comprising the following steps: obtaining the working temperature range and soot composition in the target flue; classifying the soot composition according to the particle size threshold range to obtain multiple groups of soot reference groups under different particle size threshold ranges; obtaining the sintering rate and sintering temperature of the soot reference groups, locating the corresponding position of the sintering temperature in the working temperature range, and calibrating it as the target position; installing an evaporator at the target position, the evaporator being used to capture the soot particles corresponding to the soot reference groups in the target flue, so that the soot particles are sintered, aggregated and settled; small-particle-size soot can be sintered into large-particle-size soot, and it is stripped and settled in the waste heat boiler ash hopper through the ash cleaning equipment, thereby reducing the fly ash rate and the hazardous waste treatment cost.

Description

Technical Field

[0001] The present invention relates to the technical field of waste incineration fly ash product treatment, and particularly to a method for reducing the generation rate of fly ash in a waste incineration waste heat boiler. Background Art

[0002] Municipal solid waste incineration will produce 3%-5% of incineration fly ash. Due to the complexity of the composition of municipal solid waste itself, the incineration fly ash contains many toxic and harmful substances including dioxins and heavy metals, and the heavy metals account for 0.5%-3% of the total fly ash. If the fly ash is stacked randomly without treatment, the heavy metals in it are likely to enter the environment, pollute the soil, endanger the water body, and enter the food chain through media such as soil and water body, causing poisoning to humans and other organisms. Fly ash is fine particulate matter collected in the flue gas purification system, including fly ash generated when treating flue gas with chemical agents, accounting for about 10%-20% in the ash residue. Fly ash is generally grayish white or dark gray, with a particle size less than 300 μm, mostly 1.0 μm - 30 μm, a moisture content of 10%-23%, and a loss on ignition of 34%-51%. It is easy to frost heave and difficult to compact, and the particle morphology is mostly irregular shapes such as rod-shaped, multi-angular, cotton-like, spherical, etc. At the same time, incineration fly ash contains harmful substances such as dioxins and heavy metals. According to the "Municipal Solid Waste Incineration Pollution Control Standard" (GB18485-2014), it is stipulated that "municipal solid waste incineration fly ash should be managed as hazardous waste". Therefore, fly ash must be collected separately, and shall not be mixed with municipal solid waste, incineration residues, etc., nor with other hazardous wastes.

[0003] For the waste incineration waste heat boilers in the prior art, most of them are designed as "Π"-type, four-flue or six-flue. The soot with larger particles carried by the flue gas settles in the ash hopper of the flue, and is discharged from the boiler as furnace ash. When this part of the soot settles, the temperature is relatively high, and it basically does not adsorb heavy metals and dioxins, and is ordinary waste, which can be used to make environmental protection bricks; the part with small particle size that does not settle in the waste heat boiler and enters the flue gas treatment system is fly ash, which needs to be landfilled after chelation or other treatment means, and the treatment cost is relatively high. Therefore, there is an urgent need for a method that can settle and convert some small-particle soot particles into furnace ash during the incineration process to effectively reduce the proportion of fly ash in a short time. Summary of the Invention

[0004] In the prior art, there are still technical problems such as complicated fly ash treatment and inability to generate settlement in time and effectively during the incineration process; therefore, a technical solution is provided to solve this problem.

[0005] To achieve the above object, the present invention provides a method for reducing the generation rate of fly ash in a waste incineration waste heat boiler, including the following steps:

[0006] Obtain the working temperature range and soot composition in the target flue;

[0007] Classify the soot components according to the particle size threshold range to obtain multiple groups of soot reference groups under different particle size threshold ranges;

[0008] Obtain the sintering rate and sintering temperature of the soot reference group, locate the corresponding position of the sintering temperature in the working temperature range, and mark it as the target position;

[0009] Install an evaporator at the target position. The evaporator is used to capture the soot particles corresponding to the soot reference group in the target flue, so that the soot particles sinter, aggregate and settle.

[0010] Preferably,

[0011] Mark the soot reference group with the highest content in the soot components as the target reference group;

[0012] Obtain the softening temperature of the target reference group, locate the interval position corresponding to the softening temperature and the sintering temperature in the working temperature range, and mark it as the target position.

[0013] Preferably,

[0014] Mark the sintering temperature corresponding to the sintering rate of the target reference group in the range of 30%-70% as the optimal sintering temperature, locate the interval position corresponding to the softening temperature and the optimal sintering temperature in the working temperature range, and mark it as the target position.

[0015] Preferably,

[0016] The optimal sintering temperature range is 550-850 degrees Celsius; when the content of soot with a melting point in the range of 550-700 degrees Celsius in the target reference group exceeds 50%, take 550-700 degrees Celsius as the optimal sintering temperature range.

[0017] Preferably,

[0018] The evaporator is a semi-radiative and semi-convective heat exchange evaporator, and the evaporator is fixedly installed at the target position, and a soot cleaning device is also provided. The soot cleaning device is used to vibrate or blow off the large particle soot on the evaporator.

[0019] Preferably,

[0020] The target flue includes at least one outlet, and a dust hopper is arranged behind the outlet along the soot flow direction; the dust hopper is used to collect large particle soot.

[0021] Preferably, when the soot flow direction in the target flue is from horizontal high position to horizontal low position, the evaporator and the dust hopper are arranged in sequence along the soot flow direction, and the soot cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

[0022] Preferably, when the soot flow direction in the target flue is from the horizontal low position to the horizontal high position, the ash hopper is arranged on the horizontal low position side of the evaporator, and the ash cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

[0023] Preferably, when the soot flow direction in the target flue is horizontal, the ash cleaning device and the evaporator are arranged in sequence along the soot flow direction; the ash hopper is arranged on the horizontal low position side of the evaporator.

[0024] The beneficial effects of the present invention are as follows: The present invention provides a method for reducing the fly ash generation rate of a waste incineration waste heat boiler, including the following steps: obtaining the working temperature range and soot composition in the target flue; classifying the soot composition according to the particle size threshold range to obtain multiple groups of soot reference groups under different particle size threshold ranges; obtaining the sintering rate and sintering temperature of the soot reference groups, positioning the corresponding position of the sintering temperature in the working temperature range, and marking it as the target position; installing an evaporator at the target position, and the evaporator is used to capture the soot particles corresponding to the soot reference groups in the target flue, so that the soot particles are sintered, aggregated and settled; small particle size soot can be sintered into large particle size soot, and it is stripped and settled in the waste heat boiler ash hopper through the ash cleaning equipment, thereby reducing the fly ash rate and reducing the hazardous waste treatment cost. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram when the soot of the present invention flows from top to bottom;

[0026] Figure 2 It is a schematic structural diagram when the soot of the present invention flows from bottom to top;

[0027] Figure 3 It is a schematic structural diagram when the soot of the present invention flows horizontally;

[0028] Figure 4 It is a flowchart of the method of the present invention.

[0029] Description of Component Symbols

[0030] 1. Target flue;

[0031] 2. Evaporator;

[0032] 3. Ash hopper;

[0033] 4. Ash cleaning device. Detailed Embodiments

[0034] In order to describe the present invention more clearly, the present invention will be further described below with reference to the drawings.

[0035] In the following description, details of general election examples are given to provide a deeper understanding of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0036] It should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of the described features, wholes, steps, operations, elements or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components or their combinations.

[0037] In the prior art, most methods adopt the way of additionally installing a channel and then using a chemical chelating agent to achieve particle sedimentation. However, this method is difficult to transform, and the utilization rate of space and equipment is low. Therefore, a more effective method with high sedimentation efficiency is needed.

[0038] Specifically disclose a method for reducing the generation rate of fly ash in a waste incineration waste heat boiler, including the following steps:

[0039] Obtain the working temperature range and soot composition in the target flue 1; since the temperature in the pipeline of the waste heat boiler may vary, it is necessary to measure the temperature of different pipeline temperatures under working conditions to select a suitable working temperature range and its corresponding installation position;

[0040] And classify the soot composition according to the particle size threshold range to obtain multiple groups of soot reference groups under different particle size threshold ranges; the particle size threshold range can be generated according to needs during actual production, as long as it is relatively average when setting the range;

[0041] Obtain the sintering rate and sintering temperature of the soot reference group, locate the corresponding position of the sintering temperature in the working temperature range, and mark it as the target position; in the experiment, separate experiments can be carried out for ash particles of multiple different particle sizes to obtain the best sintering effect of various ash particles. After obtaining the sintering temperature, the corresponding position can be searched in the flue according to this temperature; in addition, it should be noted that because there are other fly ashes and air flow disturbances in the flue, even if there is this temperature range, it is impossible to effectively sinter fly ash particles, so effective deposition and sintering cannot be achieved;

[0042] Install the evaporator 2 at the target position. The evaporator is used to capture the soot particles corresponding to the soot reference group in the target flue, causing the soot particles to sinter, aggregate, and settle. The high-temperature soot adheres to the evaporator. Due to the characteristics of the soot itself, the components with low ash melting points melt in the high-temperature flue gas and sinter together with other components. The diameter of the soot particles increases. They are blown into the ash hopper through soot cleaning methods such as vibrating or soot blowers and then discharged outside the furnace through the ash conveying system. Since the temperature of the evaporator tube wall is relatively low, the soot adheres to the evaporator relatively loosely, while the soot particles are firmly bonded together after sintering. Therefore, under the action of the soot cleaning equipment, it is extremely easy to peel off from the evaporator. The sintered soot particles increase in size and are not easily carried by the flue gas, so they easily settle into the ash hopper. This process causes some of the originally non-settling soot particles with smaller particle sizes in the waste heat boiler to aggregate and increase in size due to sintering, and thus are settled in the ash hopper of the waste heat boiler to become furnace ash, thereby reducing the fly ash rate and the cost of hazardous waste treatment.

[0043] In this embodiment, the soot reference group with the highest content in the soot composition is calibrated as the target reference group. Depending on the characteristics of the flue gas soot, generally it is 850 - 550 °C. If the content of low melting point components is high, a lower value is taken. The temperature should be lower than the softening temperature of the soot, otherwise coking will occur, and it should not be lower than the temperature at which the soot cannot sinter.

[0044] Obtain the softening temperature of the target reference group, locate the interval positions corresponding to the softening temperature and the sintering temperature in the working temperature range, and calibrate them as the target positions.

[0045] In this embodiment, the sintering temperature corresponding to the sintering rate of the target reference group in the range of 30% - 70% is marked as the optimal sintering temperature. Locate the interval positions corresponding to the softening temperature and the optimal sintering temperature in the working temperature range, and calibrate them as the target positions. In the above way, the experimental scheme for the sintering rate and the sintering temperature is as follows: Select soot within a certain particle size range, after high-temperature sintering, pass it through a sieve with the same aperture again. The weight ratio of the soot remaining on the sieve is the sintering rate. The sintering rate increases with the increase of temperature. The temperature corresponding to the sintering rate in the range of 30% - 70% is taken as the appropriate sintering interval temperature, and the flue at the corresponding position is the appropriate temperature for installing this evaporator.

[0046] As a more preferred embodiment, the optimal sintering temperature range is 550 - 850 °C; when the content of soot with a melting point in the range of 550 - 700 °C in the target reference group exceeds 50%, the range of 550 - 700 °C is taken as the optimal sintering temperature range. If the content of low melting point components is high, a lower value is taken. The temperature should be lower than the softening temperature of the soot, otherwise coking will occur, and it should not be lower than the temperature at which the soot cannot sinter.

[0047] In this embodiment, the evaporator is a semi-radiative and semi-convective heat exchange evaporator, and the evaporator is fixedly installed at the target position, and a soot cleaning device is also provided. The soot cleaning device is used to vibrate or blow off large particle soot on the evaporator. The evaporator is fed with water through a downcomer, and the water is drained to the steam drum through a riser, driven by natural circulation, and can be suspended or supported in the flue. Soot is adsorbed on the pipe wall, and after high-temperature sintering, the soot particles aggregate and increase in size. Then, through a soot cleaning device such as a mechanical vibrator or soot blower installed on the flue, the soot with increased particle size attached to the evaporator tube bank is vibrated off or blown into the ash hopper, so as to ensure that some small particle soot can also be intercepted by the waste heat boiler and will not enter the flue gas treatment system to become fly ash.

[0048] In this embodiment, the target flue at least includes one outlet, and an ash hopper is arranged behind the outlet along the soot flow direction; the ash hopper 3 is used to collect large particle soot.

[0049] When the soot flow direction in the target flue is from the horizontal high position to the horizontal low position, the evaporator and the ash hopper are arranged in sequence along the soot flow direction. The soot cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

[0050] When the soot flow direction in the target flue is from the horizontal low position to the horizontal high position; the ash hopper is arranged on the horizontal low position side of the evaporator, and the soot cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

[0051] When the soot flow direction in the target flue is horizontal, the soot cleaning device and the evaporator are arranged in sequence along the soot flow direction; the ash hopper is arranged on the horizontal low position side of the evaporator. Figures 1 - 3 They are three layout structures respectively, which are the flue gas flowing from top to bottom, from bottom to top and horizontally in sequence. The evaporator is arranged in the flue, and a matching soot cleaning device is provided. There is an ash hopper below the evaporator. When the flue gas flows through the evaporator, due to acting forces such as inertia force and thermophoretic force, the soot is adsorbed on the evaporator. After being burned by high-temperature flue gas, the low-melting-point components in the soot melt and aggregate with the remaining non-molten components to form large particle soot. Under the action of the soot cleaning equipment, the soot is peeled off from the evaporator tube wall. Due to the increased particle size, it is not easily carried by the flue gas, so it settles and falls into the ash hopper and is discharged out of the furnace. During the design stage, the sintering rate of soot at different temperatures is tested. First, select soot in a certain particle size range. After high-temperature sintering, pass through the same aperture sieve again. The weight ratio of the material remaining on the sieve is the sintering rate. Select a suitable sintering rate range and determine the corresponding flue gas temperature range, and according to the position of the flue gas temperature range in the flue, set a semi-radiative and semi-convective heat exchange evaporator to capture soot particles, and partially sinter them under the action of high-temperature flue gas. The particles aggregate and increase in size. Through a soot cleaning device such as vibrating soot cleaning or shock wave soot blowing, the soot is vibrated (blown) into the lower ash hopper, and the soot is discharged out of the furnace.

[0052] The technical effects of the present invention are as follows:

[0053] It is possible to sinter small-particle-size soot into large-particle-size soot and strip and settle it in the ash hopper of the waste heat boiler through the ash cleaning equipment, thereby reducing the fly ash rate and the cost of hazardous waste treatment.

[0054] The above only discloses several specific embodiments of the present invention, but the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for reducing the generation rate of fly ash in a waste incineration waste heat boiler, characterized in that It includes the following steps: Obtain the working temperature range and soot composition in the target flue; Classify the soot composition according to the particle size threshold range to obtain multiple groups of soot reference groups under different particle size threshold ranges; Obtain the sintering rate and sintering temperature of the soot reference group, locate the corresponding position of the sintering temperature in the working temperature range, and mark it as the target position; Install an evaporator at the target position, and the evaporator is used to capture the soot particles corresponding to the soot reference group in the target flue, so that the soot particles are sintered and aggregated and settle.

2. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 1, wherein Mark the soot reference group with the highest content in the soot composition as the target reference group; Obtain the softening temperature of the target reference group, locate the interval positions corresponding to the softening temperature and the sintering temperature in the working temperature range, and mark it as the target position.

3. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 2, wherein Mark the sintering temperature corresponding to the sintering rate of the target reference group in the range of 30%-70% as the optimal sintering temperature, locate the interval positions corresponding to the softening temperature and the optimal sintering temperature in the working temperature range, and mark it as the target position.

4. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 3, wherein The optimal sintering temperature range is 550-850 degrees Celsius.

5. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 3, characterized in that When the sintered content of the soot in the target reference group exceeds 50%, the optimal sintering temperature range is 550-700 degrees Celsius.

6. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 4 or 5, wherein The evaporator is a semi-radiative and semi-convective heat exchange evaporator, and the evaporator is fixedly installed at the target position, and a soot cleaning device is also provided, and the soot cleaning device is used to vibrate or blow off the large-particle soot on the evaporator.

7. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 6, wherein The target flue includes at least one outlet, and a hopper is arranged behind the outlet along the soot flow direction; the hopper is used to collect large-particle soot.

8. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 7, characterized in that When the soot flow direction in the target flue is from a horizontal high position to a horizontal low position, the evaporator and the hopper are arranged in sequence along the soot flow direction, and the soot cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

9. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 7, characterized in that, When the soot flow direction in the target flue is from a horizontal low position to a horizontal high position; the hopper is arranged on the horizontal low position side of the evaporator, and the soot cleaning device is installed beside the evaporator and fixed on the side wall of the target flue.

10. The method for reducing the fly ash generation rate of a waste incineration waste heat boiler according to claim 7, characterized in that, When the soot flow direction in the target flue is horizontal, the soot cleaning device and the evaporator are arranged in sequence along the soot flow direction; the hopper is arranged on the horizontal low position side of the evaporator.

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