阅读说明：本技术 一种烧结处理水洗飞灰过程二噁英的控制方法 (Control method for dioxin in process of sintering treatment of washing fly ash ) 是由 甘敏 黄斌斌 范晓慧 卢四平 周志安 钟伟 季志云 孙增青 许澧鸣 徐莉 陈许玲 于 2021-07-05 设计创作，主要内容包括：本发明公开了一种烧结处理水洗飞灰过程二噁英的控制方法,该方法是将垃圾焚烧飞灰进行水洗脱氯处理后,进行造球并在球料表面包裹消石灰层,干燥,得到水洗飞灰球料；将水洗飞灰球料掺入铁矿烧结粒料中混合均匀后,通过偏析布料至烧结料层的中下部,进行点火和烧结。该方法对垃圾焚烧飞灰进行水洗脱氯,可大幅度减少烧结过程中二噁英的二次生成,同时在水洗飞灰球料表面裹附消石灰能够吸附水洗飞灰球料及周围烧结料挥发的氯,并通过优化布料和烧结工艺,有效降解飞灰中的二噁英并抑制烧结过程二噁英二次生成。该方法在不影响烧结矿品质的情况下,能够有效抑制二噁英二次生成,促进垃圾焚烧飞灰的清洁资源化利用。(The invention discloses a method for controlling dioxin in the process of sintering and treating washing fly ash, which comprises the steps of carrying out washing dechlorination treatment on waste incineration fly ash, pelletizing, coating a lime slaking layer on the surface of a pellet material, and drying to obtain a washing fly ash pellet material; and doping the water-washed fly ash pellets into iron ore sintered pellets, uniformly mixing, distributing to the middle lower part of a sintered material layer through segregation, and igniting and sintering. The method carries out washing dechlorination on the waste incineration fly ash, can greatly reduce the secondary generation of dioxin in the sintering process, simultaneously wraps slaked lime on the surface of the ball material of the washing fly ash, can adsorb chlorine volatilized by the ball material of the washing fly ash and the surrounding sintering material, effectively degrades the dioxin in the fly ash and inhibits the secondary generation of the dioxin in the sintering process by optimizing the material distribution and sintering process. The method can effectively inhibit the secondary generation of dioxin and promote the clean resource utilization of the waste incineration fly ash under the condition of not influencing the quality of the sintered ore.)

1. A method for controlling dioxin in the process of sintering and treating water-washed fly ash is characterized by comprising the following steps: the method comprises the following steps:

1) carrying out washing dechlorination treatment on the waste incineration fly ash to obtain washing fly ash;

2) pelletizing the washed fly ash, coating a slaked lime layer on the surface of the obtained pellet material, and drying to obtain a washed fly ash pellet material;

3) and doping the water-washed fly ash pellets into iron ore sintered pellets, uniformly mixing, distributing to the middle lower part of a sintered material layer through segregation, and igniting and sintering.

2. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1, characterized in that: the waste incineration fly ash includes fly ash generated from a grate incinerator and/or a fluidized bed incinerator.

3. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1, characterized in that:

the mass percentage content of Cl in the water-washed fly ash is not higher than 1.0%;

CaO/SiO in the water-washed fly ash₂Is not less than 2.5.

4. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1, characterized in that: the particle size range of the ball material is 5-8 mm, and the thickness of a slaked lime layer coated on the surface of the ball material is 0.5-1 mm.

5. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1 or 4, characterized in that: the slaked lime layer is obtained by slaking quicklime with the granularity not more than 0.1mm and the activity not less than 250 mL.

6. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1, characterized in that: the water content of the water-washed fly ash ball material is 5-9% by mass.

7. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1, characterized in that: the water-washing fly ash ball material is doped in the forming process of the iron ore sintering particle material, and the water-washing fly ash ball material is doped within 1min before the iron ore sintering raw material is granulated, so that the iron ore sintering particle material and the water-washing fly ash ball material are uniformly mixed.

8. The method for controlling dioxin in the process of sintering and treating water-washed fly ash according to claim 1 or 7, characterized in that: the mixing amount of the water-washing fly ash ball material is 0.5-5.0% of the mass of the iron ore sintering granular material.

9. The method for controlling dioxin in the process of collaborative processing of fly ash of garbage by iron ore sintering according to claim 1, wherein: the segregation cloth adopts nine-roller cloth, and the gap between 5# to 9# rollers is controlled to be 5-8 mm.

10. The method for controlling dioxin in the process of collaborative processing of fly ash of garbage by iron ore sintering according to claim 1, wherein: the highest temperature of the material layer of the water-washing fly ash ball material is controlled to be 1300-1350 ℃ in the sintering process, and the heating rate is not lower than 200 ℃/min.

Technical Field

The invention relates to a method for treating waste incineration fly ash, in particular to a method for cooperatively treating the waste incineration fly ash by utilizing an iron ore sintering process, and particularly relates to a method for washing and dechlorinating the waste incineration fly ash and realizing the decomposition of persistent organic matters such as dioxin and the like in the washed fly ash by utilizing iron ore sintering, belonging to the technical field of waste incineration fly ash treatment.

Background

According to the definition in the 'domestic waste incineration pollution control Standard' (GB18485-2014) of China, Incineration Fly Ash (IFA) refers to bottom ash settled at the bottoms of a flue gas purification system and a flue and a chimney. From the combustion chamber, small particles and volatile substances are carried to Air Pollution Control Systems (APCDs), where the solid residues resulting from the separation from the flue gas stream produce 10-30 kg of fly ash per ton of waste incineration. It is classified as a hazardous solid waste (HW18) because it contains a large amount of organic pollutants such as heavy metals and dioxins. How to safely and effectively dispose the waste fly ash becomes a worldwide environmental problem, and has great significance for human health and safety.

The treatment technology of the waste incineration fly ash can be generally divided into three major categories, namely solidification-stabilization technology, separation and extraction technology and heat treatment. Although extraction and solidification stability has a certain fixing effect on heavy metals, the heavy metals have potential risk of secondary release, and the solidification compatibilization occupies a large amount of land. For the high-temperature treatment process, as the waste incineration fly ash contains a large amount of volatile chlorine salt, the direct treatment or resource utilization has the following problems: (1) the low-melting-point volatile chlorine salt volatilizes in the high-temperature process and the volatilization of acid gas can cause certain blockage or corrosion to equipment; (2) chlorine salt enters raw materials to cause some side reactions, which affect the product quality; (3) the chlorination volatilization of alkali heavy metals can obviously complicate the sintering tail gas treatment process. Therefore, the removal of chlorine in the waste fly ash is beneficial to harmless treatment and resource utilization. After the fly ash is pretreated by water washing, most of soluble salts such as KCI, NaCl and the like are removed, and fly ash particles are converted into relatively regular shapes. The washing pretreatment has an obvious effect of eluting chloride ions in the fly ash, 60-97% of chlorine can be removed, and harmless treatment and resource utilization of the fly ash are facilitated.

The iron ore sintering is the first high-temperature process in the iron and steel industry, and the iron ore sintering is used for treating the waste incineration fly ash and mainly has the following advantages: (1) the typical high-temperature process has the potential of absorbing multi-source solid wastes, on one hand, the waste incineration fly ash contains a large amount of CaO and can be used as a calcium-based flux to be applied to the sintering process, and on the other hand, the high-temperature process is beneficial to the decomposition of dioxin and the solidification of partial heavy metals; (2) the sintering has a complete flue gas purification system, and can treat complex and various flue gas pollutants; (3) the fly ash generated by a waste incineration plant can be treated on site by a steel plant, the potential risk brought by the fly ash transfer process can be reduced by fewer transportation processes, and the transportation cost is reduced. Chinese patent (CN 107159678B) discloses a dioxin control method in a process of cooperatively treating municipal waste incineration fly ash in an iron ore sintering process, and specifically discloses mixing, granulating and drying waste fly ash, lime milk, solid fuel and sludge according to the ratio of 100: 5-10: 6-15: 2-5 to obtain pellets containing the waste fly ash. The fly ash pellets and sintering raw materials are mixed, distributed and sintered by ignition. The method degrades the dioxin in the garbage flying ash by more than 90 percent on the premise of not influencing sintering, and prevents the secondary synthesis of the dioxin in the cooperative treatment process of the garbage flying ash in the sintering process. The patent (CN 107159678B) mainly aims at the original garbage fly ash which is not washed by water, and is characterized in that the chlorine content is higher, and the content is generally within the range of 10-17% according to different garbage incineration material types and incinerator types. The research generally considers that the generation mechanism of dioxin (PCDD/Fs) in the sintering process is mainly de novo synthesis, namely that macromolecular carbon and Cl in fly ash can be catalyzed and oxidized in a low-temperature post-combustion area (200-450 ℃) to generate the PCDD/Fs. Although water is eluted to remove a part of chlorine, a part of chlorine is remained, and other components including carbon, alkali heavy metal, dioxin and the like are enriched to different degrees, so that the chemical composition is remarkably changed, and the generation and emission of the dioxin are influenced to a certain extent. Therefore, the synthesis and control of dioxins in iron ore sintering applications of the washed fly ash becomes a new problem. The method solves the problem of dioxin degradation and prevents secondary synthesis in the process of sintering and treating the washing fly ash, can radically promote the application of the washing fly ash in the sintering process, and realizes harmonious symbiosis of steel plants and cities.

Disclosure of Invention

Aiming at the technical problems that the fly ash from waste incineration in the prior art is likely to corrode equipment and affect the quality of sinter ore when being used in the process of iron ore sintering due to high chlorine content. The invention aims to provide a method for realizing high-efficiency decomposition of persistent organic matters such as dioxin and the like in washing fly ash in a pre-dechlorination and iron ore sintering process by washing, which can inhibit secondary generation of dioxin and promote clean resource utilization of the waste incineration fly ash under the condition of not influencing the quality of sintered ore.

In order to achieve the technical purpose, the invention provides a method for controlling dioxin in a process of sintering and treating water-washed fly ash, which is characterized by comprising the following steps: the method comprises the following steps:

1) carrying out washing dechlorination treatment on the waste incineration fly ash to obtain washing fly ash;

2) pelletizing the washed fly ash, coating a slaked lime layer on the surface of the obtained pellet material, and drying to obtain a washed fly ash pellet material;

3) and doping the water-washed fly ash pellets into iron ore sintered pellets, uniformly mixing, distributing to the middle lower part of a sintered material layer through segregation, and igniting and sintering.

Aiming at the characteristics that the waste incineration fly ash contains dioxin and simultaneously contains a large amount of halogen which can catalyze the generation of the dioxin in the high-temperature process, the technical scheme of the invention firstly carries out washing pre-dechlorination treatment on the waste incineration fly ash, removes most of chlorine through washing, and can reduce the possibility that macromolecular carbon in the waste incineration fly ash and Cl in the fly ash are catalyzed and oxidized to generate PCDD/Fs in a low-temperature post-combustion area (200-450 ℃) from the source, thereby preventing the secondary generation of the dioxin. Secondly, the waste incineration fly ash after the dechlorination by water washing still contains a small amount of halogen and high-content dioxin, the technical scheme of the invention is used for the iron ore sintering process and is improved as follows, so that the high-efficiency decomposition of the dioxin in the washing fly ash is realized, and the volatilization and secondary generation of the dioxin are prevented. On one hand, the washing fly ash is pelletized and is formed in a centralized way, the dioxin in the washing fly ash is prevented from being dispersed too much, the dioxin can be degraded in a centralized way in the sintering high-temperature process, and the secondary generation caused by dispersion is reduced₂Avoiding the direct contact of the water washing fly ash with HCl and Cl₂And contact is carried out, so that the possibility of secondary generation of dioxin is reduced. Thirdly, the temperature of the middle and lower layers of the sintering material is higher than that of the upper layer by properly distributing the washed fly ash ball material and combining a proper sintering mode and utilizing the heat storage function of the material layer in the sintering processLayer, and the programming rate is fast, can effectively decompose the dioxin that escapes from the ball material inside with washing flying dust ball material cloth in the well lower floor of sintering material, to sum up the improvement, can utilize the iron ore sintering process high efficiency to realize the decomposition of dioxin in the waste incineration flying dust to prevent the secondary and generate.

As a preferred aspect, the waste incineration fly ash includes fly ash generated from a grate incinerator and/or a fluidized bed incinerator.

As a preferable scheme, the Cl content in the water-washed fly ash is lower than 1.0 percent by mass. The soluble chlorine in the waste incineration fly ash can be removed by the conventional water washing process in the prior art and is reduced to below 1.0 percent.

As a preferred scheme, CaO/SiO in the water-washed fly ash₂Is not less than 2.5. If CaO/SiO₂Less than 2.5, CaO/SiO can be obtained by adding a proper amount of quicklime or limestone₂The mass ratio of (a) to (b) reaches 2.5. CaO/SiO₂The mass ratio of (A) to (B) is more than 2.5, which is beneficial to the degradation of dioxin.

As a preferable scheme, the particle size range of the ball material is 5-8 mm, and the thickness of the slaked lime layer coated on the surface of the ball material is 0.5-1 mm. The washing fly ash is made into ball material with the granularity of 5-8 mm, and the ball material is added into the sintering process, so that the contact point between fly ash powder and iron ore sintering material can be obviously reduced, the generation approach of dioxin is reduced, and further the dissipation of the fly ash powder is reduced. The slaked lime layer is wrapped on the surface of the ball material, and the ball material has the following advantages: (1) the direct contact between the surface of the fly ash ball material and the sintering mixture is blocked, so that the generation of dioxin on the outer layer is reduced; (2) the CaO has poor thermal conductivity, the sintering raw material is heated firstly, so that the washed fly ash ball material is in a high-temperature environment, and dioxin in the washed fly ash ball material coated with slaked lime can be quickly degraded after being dissipated to the high-temperature environment; (3) the slaked lime on the outer layer can adsorb HCl and Cl in the water-washed fly ash ball material and the surrounding sintering mixture₂Inhibiting the de novo synthesis pathway of dioxins.

As a preferable scheme, the slaked lime layer is obtained by slaking quicklime with the granularity not more than 0.1mm and the activity degree not less than 250 mL. The slaked lime layer on the outer layer has high specific surface area and high activity, and is favorable for absorbing Cl from the inside of the water-washed fly ash ball material and the sintering raw material.

As a preferable scheme, the water content of the water-washed fly ash ball material is 5-9% by mass. As a further preferable scheme, the washed fly ash ball material is dried for 2-3 hours at the temperature of 80-100 ℃ until the water content is 5% -9%. A large number of researches show that when the ball material containing the garbage fly ash with high water content is easy to crack at 300-700 ℃, the ball material containing the garbage fly ash with high water content is dried under the condition of low-temperature hot air to reach proper water content, so that the cracking phenomenon of the ball material containing the garbage fly ash in the rapid sintering and heating process is effectively avoided, and the effect of generating powder to excite dioxin is avoided.

As a preferable scheme, the water-washed fly ash ball material is mixed in the iron ore sintering granule forming process, and the water-washed fly ash ball material is mixed in 1min before the iron ore sintering raw material is granulated, so that the iron ore sintering granule and the water-washed fly ash ball material are uniformly mixed.

As a preferable scheme, the mixing amount of the water-washing fly ash ball material is 0.5-5.0% of the mass of the iron ore sintered aggregate. The amount of the additive exceeding 5.0% may lower the sintering yield and utilization factor to some extent.

As a preferable scheme, the segregation cloth adopts nine-roller cloth, and the gap between 5# to 9# rollers is controlled to be 5-8 mm. The chlorine fly ash ball material can be segregated to the middle lower part of the material bed by adopting the preferable material distribution mode.

As a preferable scheme, the highest temperature of a material layer where the water-washed fly ash ball material is located is controlled to be 1300-1350 ℃, and the temperature rise rate is not lower than 200 ℃/min.

According to the technical scheme, the water-washed fly ash ball materials are distributed on the middle-lower layer of the sintering material layer, and part of dioxin dissipated from the water-washed fly ash ball materials is decomposed by utilizing the heat storage effect of the middle-lower layer of the sintering material layer in the sintering process.

According to the technical scheme, by strengthening granulation and changing a sintering system, the air permeability of a sintering material layer is improved, the sintering speed is accelerated, and meanwhile, the temperature rise rate in the sintering process is reduced, so that the retention time of decomposed dioxin in the sintering material layer is shortened, and the secondary generation of the dioxin is reduced.

The raw materials of the iron ore sintered pellet related to the technical scheme of the invention comprise iron ore, limestone and/or quick lime, coke powder and/or anthracite and return fines, which are the most common raw materials of iron ore sintered ore in the industry.

According to the technical scheme, an air draft sintering method is adopted, firstly, the sintering charge level is ignited at 1050-1150 ℃, the fuel in the sintering raw material is ignited, and under the action of air draft, a high-temperature zone generated by fuel combustion is gradually transferred to a lower material layer from the charge level, so that the sintering process is sequentially completed. Controlling the sintering highest temperature of the middle and lower material layers of the washed fly ash ball material to be 1300-1350 ℃, and the heating rate to be not lower than 200 ℃/min.

In the technical scheme of the invention, in the raw materials of the iron ore sintered ore, the grain size distribution of the coke powder and/or the anthracite is-0.5 mm, 20-25%, 0.5-3 mm, 60-65% and 3-5 mm, 15-20%. The grain size can control the sintering highest temperature of the middle lower part of the material layer to be 1300-1350 ℃, and the heating rate is not lower than 200 ℃/min.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

(1) according to the technical scheme, the waste incineration fly ash is subjected to washing dechlorination pretreatment, so that most of chlorine in the waste incineration fly ash can be removed, the washing fly ash is applied to the sintering process, the corrosion of sintering equipment is avoided, the influence on the quality and the yield of sintered ores is less, and the secondary generation of dioxin can be reduced.

(2) The technical scheme of the invention utilizes the sintering process to cooperatively treat the washing fly ash, and utilizes the beneficial components in the washing fly ash to generate a liquid phase through solid-phase reaction with iron ore in the sintering process. On the other hand, the high-temperature sintering process can realize the decomposition of dioxin in the washing fly ash and prevent secondary generation. The concrete advantages are that: the iron ore sintering process is the first high-temperature process in the iron and steel industry, the typical sintering temperature range is 700-1300 ℃, dioxin in water washing fly ash can be effectively decomposed and generally synthesized at 200-450 ℃, and the control is carried outThe sintering system can effectively prevent the secondary generation of dioxin; secondly, a complete flue gas purification system is arranged in the sintering process, and various flue gas pollutants generated in the sintering process of the washing fly ash can be collected and treated; ③ the washing fly ash contains higher content of CaO (more than 40 percent) and certain content of SiO₂The liquid phase generation of the washing fly ash at high temperature is promoted.

(3) The technical scheme of the invention prepares the washing fly ash into pellets under the condition of not adding any additive which is sintered and has adverse effect, can prevent the additive from introducing new pollutants, and reduces the influence on the sintering process. Meanwhile, after the water washing flying ash is pelletized, the water washing flying ash is formed in a centralized mode, so that dioxin can be degraded in a centralized mode, and secondary generation of dioxin caused by dispersion is reduced.

(4) According to the technical scheme, slaked lime is wrapped outside the washed fly ash ball material, so that the heat conductivity of the whole washed fly ash ball material can be reduced, and dioxin generated inside the small balls is released to the surrounding high-temperature environment to be rapidly decomposed. The wrapped slaked lime can adsorb HCl and Cl in the ball material and the surrounding environment₂Avoiding the direct contact of the water washing fly ash with HCl and Cl₂And (4) contacting.

(5) According to the technical scheme, the washed fly ash balls are distributed on the middle-lower layer of the sintering material, the temperature of the middle-lower layer of the sintering material is higher than that of the upper layer due to the heat storage effect of the material layer in the sintering process, and the washed fly ash balls are distributed on the middle-lower layer of the sintering material, so that dioxin dissipated from the interior of the small balls can be effectively decomposed.

In conclusion, the invention fully utilizes the beneficial chemical composition of the washing fly ash and the characteristics of the sintering process, develops the resource utilization technology of the co-processing of the washing fly ash in the sintering process, and utilizes the CaO and SiO of the washing fly ash₂Concreting with iron ore at high temperature, promoting dioxin degradation by high temperature process, and absorbing Cl by calcium lime coated on the outer layer₂HCl, reducing dioxin synthesis. The cooperative treatment process of the water washing fly ash does not have adverse effect on the sintering ore and does not additionally increase the emission of dioxin, thereby realizing the resource utilization of the water washing fly ash in the sintering process.

Detailed Description

In order to facilitate an understanding of the present invention, the present invention will be described more fully and in detail with reference to the preferred embodiments, but the scope of the present invention is not limited to the specific embodiments described below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specified, the reagents and materials used in the present invention are commercially available products or products obtained by a known method.

Comparative example 1

The other operation steps and conditions were the same as in example 2 except that the washed fly ash was added directly to the sinter mix without pelletizing it. At this time, the concentration of dioxin in the flue gas was 0.65I-TEQ (ng. Nm.) from that in the case where no water-washed fly ash was added^-3) Increased to 1.41I-TEQ (ng. Nm)^-3)。

Comparative example 2

The other operation steps and conditions were the same as in example 2 except that the washed fly ash was made into pellets of 8mm without coating the surface with slaked lime. The concentration of dioxin in the flue gas at this time was from 0.65I-TEQ (ng. Nm)^-3) Increased to 0.85I-TEQ (ng. Nm)^-3)。

Example 1

Washing the waste incineration fly ash of the grate furnace with water to obtain water-washed fly ash with the Cl content of 0.7%, preparing the water-washed fly ash into small balls with the diameter of 5mm, and adding CaO/SiO in the small balls of the water-washed fly ash₂The mass ratio of (2) to (5) is 2.5. Coating a layer of slaked lime (quicklime activity is 270ml) with thickness of 1mm before drying, and drying at 100 deg.C for 2 hr to water content of 5%. Mixing 60% of iron ore, 4% of coke powder (-0.5mm, 0.5-3 mm and 3-5 mm in the ratio of 20%, 60% and 20%, respectively), 11% of limestone and 25% of return fines, granulating, adding water-washing fly ash pellets coated with raw lime uniformly along the horizontal axis direction of a cylinder when the granulation is carried out for 5min, wherein the addition of the water-washing fly ash pellets is 0.5% of the sintering raw material, continuously granulating and uniformly mixing for 1min to ensure that the water-washing fly ash pellets and the water-washing fly ash pellets are uniformly mixedThe sintering raw materials are fully mixed. And (3) distributing the obtained sintering mixture added with the washed fly ash ball material on the middle and lower layers of the sintering material by adopting a nine-roller distributor (the gap between 5# and 9# rollers is controlled to be 5-8 mm), then igniting and sintering, wherein the sintering adopts air draft sintering, the ignition temperature is controlled to be 1150 ℃, the sintering maximum temperature is 1350 ℃, and the sintering temperature rise rate is 220 ℃/min. The sintering indexes are shown in table 1, and it can be seen that when the washed fly ash is granulated and wrapped with slaked lime and added into the sintering process, the sintering indexes are equivalent to those of the washed fly ash which is not added, and dioxin in the washed fly ash is effectively decomposed in the sintering process, and the concentration of the generated dioxin is not higher than the sintering standard.

Example 2

Washing the waste incineration fly ash of the grate furnace with water to obtain water-washed fly ash with Cl content of 1.0%, preparing the water-washed fly ash into small balls with the diameter of 8mm, and adding CaO/SiO in the small balls of the water-washed fly ash₂The mass ratio of (A) to (B) is 3.0. Coating a layer of slaked lime (quicklime activity is 250ml) with thickness of 0.5mm before drying, and drying at 80 deg.C for 3 hr to water content of 9%. Mixing and granulating sintering raw materials such as 65% of iron ore, 4.5% of coke powder (-0.5mm, 0.5-3 mm and 3-5 mm respectively accounting for 20%, 60% and 20%), 10.5% of limestone and 20% of return fines, when the granulation is carried out for 3min, uniformly adding washing fly ash pellets coated with slaked lime along the horizontal axis direction of the cylinder, wherein the addition amount of the washing fly ash pellets is 5.0% of that of the sintering raw materials, and continuously granulating for 1min to fully mix the washing fly ash pellets with the sintering raw materials. And (3) distributing the obtained sintering mixture added with the washed fly ash ball material on the middle and lower layers of the sintering material by adopting a nine-roller distributor (the gap between 5# and 9# rollers is controlled to be 5-8 mm), then igniting and sintering, wherein the sintering adopts air draft sintering, the ignition temperature is controlled to be 1050 ℃, the highest sintering temperature is 1300 ℃, and the sintering temperature rise rate is 200 ℃/min. The sintering index is shown in table 1, and it can be seen that the sintering index is equivalent to that of the non-added washing fly ash when the washing fly ash is granulated and coated with the lime. Compared with the water washing fly ash, the water washing fly ash pellets wrapped with the slaked lime are directly added in a powder form and a pellet form, and the concentration of dioxin in the sintering flue gas is respectively reduced by 57 percent and 33 percent. Compared with the method that the water washing fly ash is directly added in a powder form or is prepared into small balls without being wrapped with slaked limeIn addition, by adopting the technical measures of the invention, the concentration of dioxin in the sintering flue gas can be greatly reduced, and the concentration of the generated dioxin is not higher than the sintering standard.

TABLE 1 sintering index and degradation rate of fly ash dioxin for different examples