CN113521637A - System and method for treating dioxin in incineration fly ash by continuous microwave hydrothermal method - Google Patents
System and method for treating dioxin in incineration fly ash by continuous microwave hydrothermal method Download PDFInfo
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Abstract
The invention discloses a system and a method for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method, wherein the system for treating the dioxin in the incineration fly ash by the continuous microwave hydrothermal method comprises a heat exchange device, a buffer stirring tank, a circulating pump and a microwave reaction device; the microwave reaction device comprises a microwave safety shielding unit, a slurry circulating unit, a microwave irradiation unit and a control unit; a feed port of the slurry circulating unit is connected with the buffer stirring tank, and a discharge port of the slurry circulating unit is connected with the heat exchange device; and a circulating loop communicated with the buffer stirring tank is arranged on a pipeline between the microwave reaction device and the heat exchange device. The method is based on the traditional hydrothermal method treatment and is implanted with the high-parameter microwave treatment technology, so that organic pollutants such as dioxin in the incineration fly ash can be removed, and meanwhile, large-batch continuous treatment is realized, so that the incineration fly ash dioxin treatment process is continuous, safe, convenient, reliable in effect, small in occupied area, economical and efficient.
Description
Technical Field
The invention belongs to the field of fly ash disposal, and particularly relates to a system and a method for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method.
Background
In the work of pollution control of industrial and urban solid wastes in China, an incineration process is a treatment process with a high weight ratio, and fly ash generated in the incineration process contains a large amount of heavy metal and dioxin organic pollutants and is dangerous waste listed in national hazardous waste records, so that the incineration fly ash must be subjected to harmless treatment and resource utilization.
One of the major technical difficulties which plague the resource utilization of incineration fly ash at present is the safe, continuous, reliable and efficient removal of dioxin organic pollutants, and although some research achievements and laboratory-level small and miniature experimental equipment have been provided in some scientific research institutes at home and abroad, the methods are batch-type and discontinuous devices and corresponding systems and are limited to a single directional target. For example, publication No. CN 106077031A discloses a method for stabilizing fly ash from incineration of household garbage by applying microwave. Directly adding fly ash to be treated, an additive with a certain concentration and water into a sealed polytetrafluoroethylene container, and carrying out microwave heating to solidify heavy metals in the fly ash so as to obtain a stabilized product; after the treatment by the method, the leaching concentration of heavy metals in the fly ash is far lower than the limit value of national standard GB 16889-2008; the stabilizing method can be used for efficiently and quickly treating dangerous wastes such as the incineration fly ash of the household garbage and the like, so that the dangerous wastes can meet the requirements of safe landfill and later-period resource utilization. Also, as publication No. CN 110280196A discloses a microwave-driven hydrothermal carbonization reaction kettle device and method for municipal solid waste, a microwave generator is arranged on a microwave generator loading platform, a lower kettle body is connected with a middle kettle body through a first hexagonal stud, high pressure transmission resistant glass is arranged between the lower kettle body and the middle kettle body, a cold water pipeline is arranged on the surface of the middle kettle body, a glass kettle body is arranged in the middle kettle body, a kettle body top cover is arranged on the middle kettle body through a second hexagonal stud, and a paddle type stirrer, a thermocouple, an air inlet valve, a safety valve, a pressure gauge and an air outlet valve are arranged on the kettle body top cover; compared with the traditional hydrothermal carbonization method, the hydrothermal carbonization method has the advantages of more obvious hydrothermal carbonization effect, larger heat value promotion range, further improved energy grade of the solid fuel, simple and easy installation, strong practicability, applicability to the research of microwave-driven hydrothermal carbonization in scientific research institutions or laboratories, and wider market prospect.
The technology is only suitable for laboratory-level small and miniature experimental equipment, the power density is low, the working condition with high field intensity requirement cannot be realized, and the relevant parameters of a reaction system are difficult to accurately determine, in addition, microwave heating is mainly concentrated on a material bearing device or device at the bottom of a microwave oven chamber, the materials are heated unevenly and are all batch intermittent devices, the batch intermittent heating mode cannot meet the process treatment requirement of continuously heating the treatment materials, corresponding related treatment equipment still bears large temperature and mechanical alternating stress, in addition, the corresponding system is limited to a single-direction target, and short plates are obvious.
In view of the above, there is a need to develop a device and a method for continuous microwave treatment of incineration fly ash, which can remove organic pollutants such as dioxin in incineration fly ash and realize continuous treatment in large batch based on the traditional hydrothermal method.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a system and a method for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a system for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method, which comprises a heat exchange device, a buffer stirring tank connected with the heat exchange device, a circulating pump connected with the buffer stirring tank, and a microwave reaction device connected with the circulating pump;
the microwave reaction device comprises a microwave safety shielding unit, a slurry circulating unit and a microwave irradiation unit which are arranged in the microwave safety shielding unit, and a control unit which is electrically connected with the microwave irradiation unit; the feed inlet of the slurry circulating unit is connected with the buffer stirring tank, and the discharge outlet of the slurry circulating unit is connected with the heat exchange device; and a circulation loop communicated with the buffer stirring tank is arranged between the microwave reaction device and the heat exchange device.
Preferably, the heat exchange device is provided with a primary pulp inlet, a primary pulp outlet communicated with the primary pulp inlet, a mortar inlet connected with the discharge port of the slurry circulation unit and a mortar outlet communicated with the mortar inlet; and/or
A check valve is arranged on a pipeline between the microwave reaction device and the heat exchange device; and/or
The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method also comprises an online detection unit; and the sampling port of the online detection unit is arranged between the microwave reaction device and the heat exchange device.
Preferably, a port of the circulation loop is arranged on a first pipeline between the microwave reaction device and the check valve, and a discharge regulating valve is arranged on the first pipeline.
Preferably, the sampling port of the online detection unit is arranged between the microwave reaction device and the check valve; and/or
The control unit is connected with the online detection unit through an electric signal; the control unit controls the online detection unit to perform online detection on the slurry treated by the microwave reaction device, receives detection information of the online detection unit and controls the on-off of the circulation loop according to the detection information; and/or
And a liquid discharge pipe of the online detection unit is communicated with the inlet end of the circulating pump.
Preferably, a stirrer is arranged in the buffering stirring tank, a slag discharging port is arranged at the bottom of the buffering stirring tank, and the slag discharging port is connected with a slag discharging bin; and a slag discharge valve is arranged between the slag discharge port and the slag discharge bin.
Preferably, the bottom of the slag discharging bin is provided with a slag removing valve.
Preferably, the operating temperature of the microwave reaction device is 105-200 ℃, the operating pressure is 0.12-3 MPa, the microwave power is 0-100 kW, the microwave frequency is 300 MHz-2.8 GHz, and the fluctuation rate of the microwave electric field is less than or equal to 4%.
The second aspect of the invention provides a method for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method, wherein the incineration fly ash is treated by adopting the system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method; the process for treating incineration fly ash by the continuous microwave hydrothermal method comprises the following steps:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry;
(2) the raw ash slurry is subjected to preheating treatment and then is mixed and stirred with circulating slurry obtained through microwave heating treatment to obtain homogeneous slurry and precipitates, and the homogeneous slurry is subjected to microwave heating treatment and is circulated for 2-5 times to obtain mortar;
(3) and cooling the mortar by a heat exchange device and then discharging.
Preferably, in the step (1), the solid content of the raw ash slurry is 15-25 wt%; and/or
In the step (2):
the circulating slurry is obtained by the following steps: the raw ash slurry is preheated and then enters a buffer stirring tank for stirring treatment to obtain pretreated slurry, and then enters a microwave reaction device for microwave heat treatment to obtain the circulating slurry; and/or
After the mortar is detected, if the dioxin content in the mortar is less than 3 mu g TEQ/Kg, the step (3) is carried out, otherwise, the mortar is taken as circulating slurry to enter a circulating stirring tank.
Preferably, in the step (2):
after the preheating treatment, the temperature of the raw ash slurry is 45-65 ℃; and/or
In the stirring treatment process, the stirring speed is 60-120 rpm; and/or
In the microwave heating treatment, the treatment temperature is 105-200 ℃, and the treatment pressure is 0.12-3 MPa; and/or
In the step (3), after the cooling treatment, the temperature of the mortar is less than or equal to 50 ℃.
The system and the method for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method provided by the invention also have the following beneficial effects:
1. the method is based on the traditional hydrothermal method treatment and is implanted with the high-parameter microwave treatment technology, so that organic pollutants such as dioxin in the incineration fly ash can be removed, and meanwhile, large-batch continuous treatment is realized, so that the incineration fly ash dioxin treatment process is continuous, safe, convenient, reliable in effect, small in occupied area, economical and efficient;
2. according to the invention, the microwave heating treatment is carried out through the high temperature and field intensity effect generated by the microwave irradiation heating system, so that dioxin in the incineration fly ash is effectively decomposed, and heavy metal elements are effectively solidified;
3. according to the invention, the raw ash slurry is preheated and then mixed and stirred with the circulating slurry after microwave heating treatment in the buffer stirring tank, heavy metal elements are solidified in the precipitate (zeolite substance) in the process, secondary pollution is not generated in the subsequent microwave hydrothermal method treatment process, and the precipitate (zeolite substance) has high resource utilization potential due to the heavy metal elements;
4. the invention adopts the high-parameter microwave reaction device with stepless power regulation, so that the whole slurry circulating unit is in a high-temperature and high-pressure condition, the operation consumption is effectively reduced, and the consumption of required comprehensive unit manpower, energy and medium is less;
5. the invention directly detects the dioxin content in the slurry treated by the microwave reaction device through the online detection unit, thereby facilitating the continuous control of the whole incineration fly ash dioxin treatment process.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic structural diagram of a system for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method according to the present invention;
fig. 2 is a schematic structural diagram of another continuous microwave hydrothermal treatment system for dioxin in incineration fly ash according to the present invention.
Detailed Description
In order to better understand the technical solutions of the present invention, the following further describes the technical solutions of the present invention with reference to the accompanying drawings and examples.
Referring to fig. 1 and 2, the system for treating dioxin in incineration fly ash by using a continuous microwave hydrothermal method provided by the invention comprises a heat exchange device 4, a buffer stirring tank 1 connected with the heat exchange device 4, a circulating pump 2 connected with the buffer stirring tank 1, and a microwave reaction device 3 connected with the circulating pump 2;
the microwave reaction apparatus 3 shown in fig. 1 includes a microwave safety shielding unit 31, a slurry circulation unit 32 and a microwave safety shielding unit 33 disposed in the microwave safety shielding unit 31, and a control unit 34 electrically connected to the microwave safety shielding unit 33; the feed inlet of the slurry circulating unit 32 is connected with the buffer stirring tank 1, and the discharge outlet of the slurry circulating unit 32 is connected with the heat exchange device 4; a circulating branch pipe communicated with the buffering stirring tank 1 is also arranged on the pipeline between the microwave reaction device 3 and the heat exchange device 4. The operating parameters of the microwave reaction device 3 are as follows: the operation temperature is 105-200 ℃; the operation pressure is 0.12-2 MPa; the microwave power is 0-100 kW; the microwave frequency is 300 MHz-2.8 GHz; the fluctuation ratio of the microwave electric field is less than or equal to 4 percent.
In the specific embodiment shown in fig. 1, the heat exchanger 4 is provided with a raw slurry inlet, a raw slurry outlet, a slurry inlet and a slurry outlet, wherein the raw slurry inlet is communicated with the raw slurry outlet, the slurry inlet is communicated with the slurry outlet, and the slurry inlet is connected with the discharge port of the slurry circulating unit 32; raw mortar slurry enters a heat exchange device 4 from a raw pulp inlet of the heat exchange device 4, enters a buffer stirring tank 1 from a raw pulp outlet after heat exchange with mortar from a microwave reaction device 3, the temperature of the mortar is reduced after heat exchange, and the mortar is discharged from a mortar outlet, at the moment, dioxin in the mortar is decomposed, heavy metal elements in the mortar are solidified in precipitates (zeolite substances), and the mortar can be further utilized, such as being used as building materials after the mortar is dehydrated, and the like; the precipitate (zeolite substance) contains heavy metals and other substances, and has high resource utilization potential.
In the specific embodiment shown in fig. 1, a check valve 5 is provided on the pipe between the microwave reactor 3 and the heat exchanger 4 in order to prevent the slurry from flowing backward.
In the specific embodiment shown in fig. 1, the port of the circulation branch is arranged on the first pipeline 13 between the microwave reactor 3 and the check valve 5, and the first pipeline 13 is provided with the discharge regulating valve 6 to control whether the slurry after the reaction in the microwave reactor 3 continuously participates in the circulation (stirring treatment and microwave heating treatment).
Referring to fig. 1, a stirrer 10 is arranged in a buffering stirring tank 1, a slag discharging port is arranged at the bottom of the buffering stirring tank 1, and the slag discharging port is connected with a slag discharging bin 8; a slag discharging valve 7 is arranged between the slag discharging port and the slag discharging bin 8, and a slag cleaning valve 9 is arranged at the bottom of the slag discharging bin 8. After being preheated by the heat exchange device 4, the raw ash slurry enters the buffer stirring tank 1 and is mixed with the circulating slurry treated by the microwave reaction device 3, and the mixture can be directly stirred and treated, and can also be added with part of additives to accelerate the oxidative decomposition of dioxin in the fly ash; in the stirring process, heavy metal elements and the like in the preheated original ash slurry and the circulating slurry are solidified into precipitates, wherein the precipitates belong to zeolite substances, enter the slag discharging bin 8 from a slag discharging port of the buffering and stirring device, and after the precipitates are accumulated to a certain degree, the slag cleaning valve 9 at the bottom of the slag discharging bin 8 is opened to transfer the precipitates (the zeolite substances).
In a specific embodiment, as shown in fig. 2, in order to facilitate the continuous microwave hydrothermal process, the system for processing dioxin in incineration fly ash by the continuous microwave hydrothermal process further includes an online detection unit 11; the sampling port of the online detection unit 11 is arranged between the microwave reaction device 3 and the heat exchange device 4; for real-time online detection, a sampling port of the online detection unit 11 is arranged on the first pipeline 13 between the microwave reaction device 3 and the check valve 5, and specifically, the sampling port is arranged between the microwave reaction device 3 and the discharging regulating valve 6; wherein, the online detection unit 11 samples through a sampling pipe, the sampling port refers to a port of the sampling pipe during sampling, and the sampling pipe is provided with a sampling valve 12. The control unit 34 is connected with the on-line detection unit 11 through an electric signal, the control unit 34 is used for controlling the on-line detection unit 34 to perform on-line detection on the slurry processed by the microwave reaction device 3, receiving detection information of the on-line detection unit 11, and controlling the on-off of the circulation loop according to the detection information, wherein the on-line detection unit 11 detects toxicity TEQ of dioxin on the slurry processed by the microwave reaction device 3. The principle that the control unit 34 controls the on-off of the discharging adjusting valve 6 is as follows: when the toxicity TEQ of dioxin in the slurry treated by the microwave reaction device 3 does not reach the GB16889 standard specification, the control unit 34 controls the discharge adjusting valve 6 to be closed, and the slurry is circulated and treated again in the buffer stirring tank 1 through the circulation loop; in order to prevent the waste liquid of the online detection unit from discharging unqualified, a liquid discharge pipe of the online detection unit 11 is communicated with the inlet end of the circulating pump 2, and the waste liquid participates in microwave heating treatment under the action of negative pressure, so that the detected waste liquid is further treated conveniently; the check valve 14 is arranged on the liquid discharge pipe, so that when the circulating pump 2 is stopped, the slurry in the slurry circulating unit 32 is prevented from causing backflow of waste liquid in the liquid discharge pipe due to static pressure difference, and the online detection equipment 11 is prevented from being damaged.
With reference to fig. 1 and 2, the system for treating dioxin in incineration fly ash by using the continuous microwave hydrothermal method for treating incineration fly ash, specifically comprises the following steps:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry: in the pulping device, the solid content of the raw ash pulp is 15-25 wt%;
(2) preheating the raw ash slurry, mixing the raw ash slurry with circulating slurry obtained by microwave heating treatment, stirring to obtain homogeneous slurry and precipitates (zeolite substances), carrying out microwave heating treatment on the homogeneous slurry, and circulating for 2-5 times to obtain mortar;
the specific process is as follows: firstly, preheating raw ash slurry by a heat exchange device, then feeding the preheated raw ash slurry into a buffer stirring tank for stirring to obtain pretreated slurry, and feeding the pretreated slurry into a microwave reaction device under the action of a circulating pump for microwave heating to obtain circulating slurry; then mixing and stirring the circulating slurry and the preheated raw ash slurry to obtain the productHomogenizing the slurry and precipitate (zeolite material), and then subjecting the homogenized slurry to microwave heating treatment for 2-5 times to obtain mortar; in the process, in the preheating treatment, the heat source is from the mortar after microwave heating treatment, and the temperature of the original mortar after preheating treatment is 45-65 ℃; mixing the circulating slurry with the preheated raw ash slurry, stirring, and optionally adding part of additives (such as NaOH and H)2O2Etc.), accelerating the oxidative decomposition of dioxins in the fly ash; in the stirring process, the stirring speed is controlled to be 60-120 rpm, so that on one hand, precipitates (zeolite substances) cannot be solidified and precipitated due to too fast stirring, and on the other hand, the circulating slurry cannot be uniformly mixed with the preheated raw ash slurry due to too slow stirring; in the microwave heating treatment process, the treatment temperature is 105-200 ℃, and the treatment pressure is 0.12-3 MPa (in a further preferred scheme, the treatment pressure is controlled to be 0.12-2 MPa); with reference to fig. 2, whether the content of dioxins in the finally treated mortar reaches the standard or not is detected by using an online detection unit, and the specific process is as follows: the control unit controls the online detection unit to perform real-time online detection on the mortar subjected to microwave heating treatment, then judges whether the mortar subjected to microwave heating treatment reaches the standard or not according to the detection data of the online detection unit and the content of the dioxin, if the mortar exceeds the standard, the control unit immediately closes the discharging adjusting valve, the mortar serving as circulating slurry enters the buffer stirring tank and is mixed with the original mortar to continue to perform microwave heating treatment;
(3) cooling the mortar by a heat exchange device and then discharging: after microwave heating treatment, the mortar has higher temperature and needs to be cooled, and a heat exchange device is adopted to utilize waste heat, so that on one hand, the temperature of the mortar can be reduced, the energy consumption is reduced, and on the other hand, the waste heat is utilized to preheat the original mortar; the temperature of the cooled mortar is reduced to less than or equal to 50 ℃, for example, 45-50 ℃.
After the treatment, the content of heavy metal elements in the mortar is reduced to a lower level, the heavy metal content requirement specified by the GB16889 standard is met, and the mortar can be used as a building material; the dioxin content of the incineration fly ash after dechlorination treatment is less than 3 mu g TEQ/Kg most heavy metal elements are solidified in the precipitate (zeolite substance).
The system and the method for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method are further described by combining specific examples; examples 1 to 3 the incineration fly ash subjected to the dechlorination treatment was treated by using the system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method.
Example 1
The washing ash in this example is incineration fly ash subjected to dechlorination, and the dioxin and part of heavy metal element contents thereof are shown in table 1;
the process for treating dioxin in incineration fly ash by using the continuous microwave hydrothermal method in the embodiment is as follows:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry with the solid content of 15 wt%;
(2) preheating raw ash slurry by a heat exchange device to reach 65 ℃, feeding the raw ash slurry into a buffer stirring tank, and stirring to obtain pretreated slurry, wherein the pretreated slurry enters a microwave reaction device by a circulating pump to be subjected to microwave heating treatment to obtain circulating slurry, the stirring rotating speed is 120rpm, the microwave heating treatment temperature is 110 ℃, and the microwave heating treatment pressure is 0.12-2 MPa; then mixing and stirring the circulating slurry and the preheated original ash slurry to obtain homogeneous slurry and precipitate, feeding the homogeneous slurry into a microwave reaction device for microwave heating treatment, and circulating for 2 times to obtain mortar, wherein the stirring rotation speed is 60rpm, the microwave heating treatment temperature is 105-200 ℃, the microwave heating treatment pressure is 0.12-2 MPa, an online detection unit detects the content of dioxin in the mortar, and the result is shown in Table 1, wherein the content of the dioxin is 0.001622 mu g of TEQ/kg;
(3) the slurry was cooled by a heat exchanger and discharged, wherein the temperature of the cooled slurry was reduced to 45 ℃.
The precipitates collected after the above-mentioned treatment and the cooled mortar were subjected to chemical examination, and the results are shown in table 1, in which the removal rate of dioxin and organic volatile matters in the incineration fly ash after dechlorination was not less than 90%, and most of heavy metal elements were solidified in the precipitates (zeolite-like substances).
Example 2
The washing ash in this example is incineration fly ash subjected to dechlorination, and the dioxin and part of heavy metal element contents thereof are shown in table 1;
the process for treating dioxin in incineration fly ash by using the continuous microwave hydrothermal method in the embodiment is as follows:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry with the solid content of 20 wt%;
(2) preheating raw ash slurry by a heat exchange device, enabling the temperature to reach 50 ℃, entering a buffer stirring tank, stirring to obtain pretreated slurry, entering the pretreated slurry into a microwave reaction device by a circulating pump, performing microwave heating treatment to obtain circulating slurry, wherein the stirring speed is 120rpm, the microwave heating treatment temperature is 150 ℃, the microwave heating treatment pressure is 0.12-2 MPa, mixing and stirring the circulating slurry and the preheated raw ash slurry to obtain homogeneous slurry and precipitates, entering the homogeneous slurry into the microwave reaction device, performing microwave heating treatment, and circulating for 4 times to obtain mortar, wherein the stirring speed is 120rpm, the microwave heating treatment temperature is 105-200 ℃, and the microwave heating treatment pressure is 1.05-2 MPa; the system is provided with an online detection unit, real-time online detection is carried out on the slurry subjected to microwave heating treatment, the content of dioxin in the slurry is detected, if the content exceeds the standard, a discharging adjusting valve is immediately turned off, and the treated slurry is used as circulating slurry for retreatment; the online detection unit detects the content of dioxin in mortar, and the result is shown in table 1, wherein the content of dioxin is 0.00107 mu g TEQ/kg;
(3) the slurry is discharged after cooling by means of a heat exchanger, wherein the temperature of the cooled slurry is reduced to 50 ℃.
The precipitates collected after the above-mentioned treatment and the cooled mortar were subjected to chemical examination, and the results are shown in table 1, in which the removal rate of dioxin and organic volatile matters in the incineration fly ash after dechlorination was not less than 90%, and most of heavy metal elements were solidified in the precipitates (zeolite-like substances).
Example 3
The washing ash in this example is incineration fly ash subjected to dechlorination, and the dioxin and part of heavy metal element contents thereof are shown in table 1;
the process for treating dioxin in incineration fly ash by using the continuous microwave hydrothermal method in the embodiment is as follows:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry with the solid content of 25 wt%;
(2) preheating raw ash slurry by a heat exchange device to reach 45 ℃, feeding the raw ash slurry into a buffer stirring tank, and stirring to obtain pretreated slurry, wherein the pretreated slurry enters a microwave reaction device by a circulating pump to be subjected to microwave heating treatment to obtain circulating slurry, the stirring rotating speed is 120rpm, the microwave heating treatment temperature is 105-200 ℃, and the microwave heating treatment pressure is 0.12-2 MPa; then mixing and stirring the circulating slurry and the preheated original ash slurry to obtain homogeneous slurry and precipitate, allowing the homogeneous slurry to enter a microwave reaction device for microwave heating treatment, and circulating for 5 times to obtain mortar, wherein the stirring speed is 120rpm, the microwave heating treatment temperature is 105-200 ℃, and the microwave heating treatment pressure is 0.12-2 MPa, the system is provided with an online detection unit, performing real-time online detection on the slurry subjected to microwave heating treatment, detecting the content of dioxin in the slurry, and immediately turning off a discharging adjusting valve if the content exceeds the standard, and treating the slurry as the circulating slurry for retreatment; the online detection unit detects the contents of heavy metals and dioxin in mortar, and the result is shown in table 1, wherein the content of dioxin is 0.00153 mu g TEQ/kg;
(3) the slurry was cooled by a heat exchanger and discharged, wherein the temperature of the cooled slurry was reduced to 45 ℃.
The precipitates collected after the above-mentioned treatment and the cooled mortar were subjected to chemical examination, and the results are shown in table 1, in which the removal rate of dioxin and organic volatile matters in the incineration fly ash after dechlorination was not less than 90%, and most of heavy metal elements were solidified in the precipitates (zeolite-like substances).
TABLE 1 comparison of indexes of incineration fly ash subjected to dechlorination treatment before and after the treatment
In conclusion, the method is based on the traditional hydrothermal method for treatment and is implanted with the high-parameter microwave treatment technology, so that organic pollutants such as dioxin in the incineration fly ash can be removed, and meanwhile, large-batch continuous treatment is realized, so that the incineration fly ash dioxin treatment process is continuous, safe, convenient, reliable in effect, small in occupied area, economical and efficient; the microwave heating treatment is carried out through the high temperature and field intensity effect generated by the microwave irradiation heating system, so that dioxin in the incineration fly ash is effectively decomposed, and heavy metal elements are effectively solidified; according to the invention, the raw ash slurry is preheated and then mixed and stirred with the circulating slurry after microwave heating treatment in the buffer stirring tank, heavy metal elements are solidified in the precipitate (zeolite substance) in the process, secondary pollution is not generated in the subsequent microwave hydrothermal method treatment process, and the precipitate (zeolite substance) has high resource utilization potential due to the heavy metal elements; the invention adopts the high-parameter microwave reaction device with stepless power regulation, so that the whole slurry circulating unit is in a high-temperature and high-pressure condition, the operation consumption is effectively reduced, and the consumption of required comprehensive unit manpower, energy and medium is less; the invention directly detects the dioxin content in the slurry treated by the microwave reaction device through the online detection unit, thereby facilitating the continuous control of the whole incineration fly ash dioxin treatment process.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above described embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.
Claims (10)
1. A system for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method is characterized by comprising a heat exchange device, a buffer stirring tank connected with the heat exchange device, a circulating pump connected with the buffer stirring tank, and a microwave reaction device connected with the circulating pump;
the microwave reaction device comprises a microwave safety shielding unit, a slurry circulating unit and a microwave irradiation unit which are arranged in the microwave safety shielding unit, and a control unit which is electrically connected with the microwave irradiation unit; the feed inlet of the slurry circulating unit is connected with the buffer stirring tank, and the discharge outlet of the slurry circulating unit is connected with the heat exchange device; and a circulation loop communicated with the buffer stirring tank is arranged between the microwave reaction device and the heat exchange device.
2. The continuous microwave hydrothermal treatment system for dioxin in incineration fly ash according to claim 1,
the heat exchange device is provided with a primary pulp inlet, a primary pulp outlet communicated with the primary pulp inlet, a mortar inlet connected with the discharge port of the slurry circulation unit and a mortar outlet communicated with the mortar inlet; and/or
A check valve is arranged on a pipeline between the microwave reaction device and the heat exchange device; and/or
The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method also comprises an online detection unit; and the sampling port of the online detection unit is arranged between the microwave reaction device and the heat exchange device.
3. The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 2, wherein a port of the circulation circuit is provided in a first pipe between the microwave reaction device and the check valve, and the first pipe is provided with a discharge regulating valve.
4. The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 2, wherein a sampling port of the online detection unit is provided between the microwave reaction device and the check valve; and/or
The control unit is connected with the online detection unit through an electric signal; the control unit controls the online detection unit to perform online detection on the slurry treated by the microwave reaction device, receives detection information of the online detection unit and controls the on-off of the circulation loop according to the detection information; and/or
And a liquid discharge pipe of the online detection unit is communicated with the inlet end of the circulating pump.
5. The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 1, wherein a stirrer is arranged in the buffer stirring tank, a slag discharge port is arranged at the bottom of the buffer stirring tank, and the slag discharge port is connected with a slag discharge bin; and a slag discharge valve is arranged between the slag discharge port and the slag discharge bin.
6. The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 5, wherein a slag removal valve is arranged at the bottom of the slag discharge bin.
7. The system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 1, wherein the operating temperature of the microwave reaction device is 105 to 200 ℃, the operating pressure is 0.12 to 3MPa, the microwave power is 0 to 100kW, the microwave frequency is 300MHz to 2.8GHz, and the fluctuation rate of the microwave electric field is less than or equal to 4%.
8. A method for treating dioxin in incineration fly ash by a continuous microwave hydrothermal method, which is characterized in that the incineration fly ash is treated by using the system for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to any one of claims 1 to 7; the process for treating incineration fly ash by the continuous microwave hydrothermal method comprises the following steps:
(1) adding water into the incineration fly ash subjected to dechlorination treatment to prepare raw ash slurry;
(2) the raw ash slurry is subjected to preheating treatment and then is mixed and stirred with circulating slurry obtained through microwave heating treatment to obtain homogeneous slurry and precipitates, and the homogeneous slurry is subjected to microwave heating treatment again and is circulated for 2-5 times to obtain mortar;
(3) and cooling the mortar by a heat exchange device and then discharging.
9. The method for treating dioxin in incineration fly ash by the continuous microwave hydrothermal method according to claim 8, wherein in the step (1), the solid content of the raw ash slurry is 15 to 25 wt%; and/or
In the step (2):
the circulating slurry is obtained by the following steps: the raw ash slurry is preheated and then enters a buffer stirring tank for stirring treatment to obtain pretreated slurry, and then enters a microwave reaction device for microwave heat treatment to obtain the circulating slurry; and/or
After the mortar is detected, if the dioxin content in the mortar is less than 3 mu g TEQ/Kg, the step (3) is carried out, otherwise, the mortar is taken as circulating slurry to enter a circulating stirring tank.
10. The continuous microwave hydrothermal method for treating dioxin in incineration fly ash according to claim 9, characterized in that in the step (2):
after the preheating treatment, the temperature of the raw ash slurry is 45-65 ℃; and/or
In the stirring treatment process, the stirring speed is 60-120 rpm; and/or
In the microwave heating treatment, the treatment temperature is 105-200 ℃, and the treatment pressure is 0.12-3 MPa; and/or
In the step (3), after the cooling treatment, the temperature of the mortar is less than or equal to 50 ℃.
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