阅读说明：本技术 一种飞灰碳化处置工艺 (Fly ash carbonization treatment process ) 是由 朱准平 钟坚 于 2021-07-30 设计创作，主要内容包括：本发明提供一种飞灰碳化处置工艺,采用以下处理步骤：经收集的飞灰,与碳源进行充分混合,然后进入高温碳化装置,在无氧条件下进行加热,首先使得二噁英类有机物挥发和热分解,生成的气体进入碳化装置的一次燃烧和二次燃烧装置,进行充分燃烧形成以二氧化碳为主的气体,二噁英热分解形成的固体主要为无定形碳,部分随着气体进入尾气处理过程,部分则沉淀下来,成为固体碳,排出碳化装置外,冷却后,经检验符合标准要求后,可储存与转运。相比现有的飞灰处置技术,本发明可同时解决飞灰的两大危害(即二噁英与重金属浸出毒性),产物可实现综合利用,如用作水泥原料等。(The invention provides a fly ash carbonization treatment process, which adopts the following treatment steps: the collected fly ash is fully mixed with a carbon source, and then enters a high-temperature carbonization device to be heated under the anaerobic condition, so that dioxin organic matters are volatilized and thermally decomposed at first, the generated gas enters a primary combustion and secondary combustion device of the carbonization device to be fully combusted to form gas mainly containing carbon dioxide, the solid formed by the thermal decomposition of the dioxin is mainly amorphous carbon, part of the solid enters a tail gas treatment process along with the gas, and part of the solid is precipitated to form solid carbon which is discharged out of the carbonization device and can be stored and transported after being tested to meet the standard requirements. Compared with the existing fly ash disposal technology, the invention can simultaneously solve two major hazards of the fly ash (namely the leaching toxicity of dioxin and heavy metal), and the product can realize comprehensive utilization, such as being used as a cement raw material and the like.)

1. A fly ash carbonization treatment process is characterized by comprising the following treatment steps: the collected fly ash is fully mixed with a carbon source, and then enters a high-temperature carbonization device to be indirectly heated under the anaerobic condition, the central temperature of the raw material is 300-600 ℃, dioxin organic matters are firstly volatilized and thermally decomposed, the generated gas enters a primary combustion device and a secondary combustion device of the carbonization device to be fully combusted to form gas mainly containing carbon dioxide, the solid formed by the thermal decomposition of the dioxin is mainly amorphous carbon, part of the solid enters a tail gas treatment process along with the gas, and part of the solid is precipitated to form solid carbon which is discharged out of the carbonization device and is stored and transported after being tested to meet the standard requirements.

2. A fly ash carbonization treatment process according to claim 1, characterized in that: the carbon source adopts carbon powder or pretreated garbage, and the pretreated garbage is regenerated carbon formed by carbonizing garbage.

3. A fly ash carbonization treatment process according to claim 1, characterized in that: adding slaked lime powder into the fly ash before the fly ash enters a high-temperature carbonization device and fully mixing;

or spraying slaked lime powder into the gas combustion chamber of the carbonizing device while combusting the gas to adsorb acid gas formed by combustion, such as HF, HCl and SOx.

4. A fly ash carbonization treatment process according to claim 1, characterized in that: washing and desalting fly ash, precipitating, filter-pressing, drying, and then performing carbonization treatment, wherein the water content of the dried fly ash is reduced to below 30%;

or the fly ash enters the carbonization treatment process firstly, then is washed and desalted, and the water content is reduced to below 30 percent after precipitation, filter pressing and drying.

5. A fly ash carbonization treatment process according to claim 2, characterized in that: the quality requirements of the carbon powder are as follows: the granularity is less than 2mm, and the carbon content is more than or equal to 20 percent.

6. A fly ash carbonization treatment process according to claim 2, characterized in that: the mixing proportion of the fly ash and the carbon powder is calculated according to the actual heavy metal and carbon content, and the weight ratio of the heavy metal to the carbon is 1: 5-1: 40.

7. a fly ash carbonization treatment process according to claim 3, characterized in that: the slaked lime powder has the following quality requirements: the purity is more than or equal to 70 percent, and the granularity is less than or equal to 0.5 mm.

8. A fly ash carbonization treatment process according to claim 3, characterized in that: the mixing proportion of the fly ash and the slaked lime powder is calculated according to the total amount of S + Cl elements in the fly ash and the total amount of Ca elements in the slaked lime, wherein the ratio of S + Cl: ca = 1: 2-1: 50.

9. a fly ash carbonization treatment process according to claim 2, characterized in that: the mixing ratio of the fly ash to the pretreated garbage is less than or equal to 1: 10.

10. a fly ash carbonization treatment process according to claim 2, characterized in that: the temperature of carbonization treatment in the high-temperature carbonization device is 400-900 ℃ (external heat temperature), the time of carbonization treatment is 10-60 min, the oxygen content in the carbonization process is controlled to be less than or equal to 1%, the interior of the carbonization device is generally controlled to be slightly negative pressure, and the internal pressure is generally-10 to-100 Pa;

before the carbonization device starts to operate, the furnace is purged by using compressed nitrogen, so that the oxygen content in the carbonization device is less than or equal to 3 percent, and the nitrogen is also used for protection in the disposal process;

the tail gas treatment process comprises the measures of quenching and cooling, desulfurization and deacidification treatment, denitration or dust removal treatment.

Technical Field

The invention belongs to a waste disposal method, and particularly relates to a fly ash carbonization disposal process.

Background

In the incineration process of household garbage (and other wastes including hazardous wastes), the bottom ash which is captured by a delay purification system and is settled in a flue and a chimney is called fly ash, belongs to hazardous wastes (code HW18, 772) 002-18), not only enriches heavy metals (such as Cr, Cd, Hg, Pb, Cu, Ni and the like), but also is a carcinogenic accident, is a main enrichment body of dioxin-like substances, is a double hazardous waste which simultaneously has heavy metals, high leaching concentration and high toxic equivalent of the dioxin-like substances, and is generally recognized as a waste with larger hazard in the world. At present, the disposal method is generally landfill, and two major hazard problems of fly ash cannot be really solved.

Disclosure of Invention

The invention aims to provide a fly ash carbonization treatment process, which aims to solve two major hazards of fly ash and create basic conditions for subsequent resource utilization.

In order to solve the technical problems, the invention adopts the following technical scheme:

a fly ash carbonization treatment process comprises the following treatment steps: the collected fly ash is fully mixed with a carbon source, and then enters a high-temperature carbonization device to be indirectly heated under an anaerobic condition (the central temperature of raw materials is 300-600 ℃), so that dioxin organic matters are volatilized and thermally decomposed at first, the generated gas enters a primary combustion and secondary combustion device of the carbonization device to be fully combusted to form gas mainly containing carbon dioxide, the solid formed by the thermal decomposition of the dioxin is mainly amorphous carbon, part of the solid enters a tail gas treatment process along with the gas, and part of the solid is precipitated to form solid carbon which is discharged out of the carbonization device and is stored and transported after being tested to meet standard requirements.

The carbon source adopts carbon powder or pretreated garbage, the pretreated garbage is regenerated carbon formed by carbonizing garbage, and the regenerated carbon refers to household garbage or other wastes taking organic matters as main components, and is a raw material after pretreatment (including but not limited to sorting, crushing and granulating).

In the technical scheme, the fly ash is added with slaked lime powder before entering the high-temperature carbonization device and is fully mixed.

Or spraying slaked lime powder into the gas combustion chamber of the carbonizing device while combusting the gas to adsorb acid gas formed by combustion, such as HF, HCl and SOx.

In the technical scheme, the fly ash is firstly washed and desalted, and then enters a carbonization treatment process after precipitation, filter pressing and drying, and the moisture content of the dried fly ash is reduced to below 30%. The main purposes of water washing are desalination and heavy metal recovery, and the main purpose of carbonization is dioxin removal.

Or the fly ash enters the carbonization treatment process firstly, then is washed and desalted, and the water content is reduced to below 30 percent after precipitation, filter pressing and drying.

Wherein, in the above technical scheme, the quality requirements of the carbon powder are as follows: the granularity is required to be less than 2mm, and the carbon content is more than or equal to 20 percent.

Wherein, the slaked lime (Ca (OH)₂) The quality requirement of the powder is as follows: the purity is more than or equal to 70 percent, and the granularity is less than or equal to 0.5 mm.

Wherein the mixing proportion of the fly ash and the carbon powder is calculated according to the actual heavy metal and carbon content, and the weight ratio of the heavy metal to the carbon is 1: 5-1: 40.

wherein, the mixing proportion of the fly ash and the slaked lime powder is calculated according to the total amount of S + Cl elements in the fly ash and the total amount of Ca elements in the slaked lime, and the ratio of S + Cl: ca 1: 2-1: 50.

wherein the mixing ratio of the fly ash to the pretreated garbage is less than or equal to 1: 10.

wherein the temperature of the carbonization treatment is 400-900 ℃, the time of the carbonization treatment is 10-60 min, the oxygen content in the carbonization process is controlled to be less than or equal to 1%, the interior of the carbonization device is generally controlled to be slightly negative pressure, and the internal pressure is generally-10 to-100 Pa.

Before the carbonization device starts to operate, the furnace is purged by using compressed nitrogen, so that the oxygen content in the carbonization device is less than or equal to 3%, and nitrogen protection is also adopted in the production process.

Further, slaked lime powder is injected into the gas combustion chamber of the carbonization device while the gas is combusted to adsorb acid gases (such as HF, HCl, SOx) formed by the combustion.

Basic physicochemical properties of fly ash:

water content: typically 5% or less, density: the bulk density is generally 0.5 to E1.0g/cm³The true density is usually 2.8-3.21 g/cm³Basic components (taking waste incineration fly ash as an example): ca. The inorganic elements such As Si, S, Mg, Al, K, Na, Fe, P and the like account for about 70-90% of the total amount, Cl accounts for about 2-12% of the total amount, S accounts for about 1-8% of the total amount, and heavy metals such As Cr, As, Cd, Hg, Pb, Cu, Ni, Zn and the like account for about 0.1-2% of the total amount. In addition, the total amount of dioxin pollutants is about 1 to 20 mu g TEQ/kg.

Mechanism of decomposition of dioxins:

dioxin is a group of polychlorinated substituted planar aromatic hydrocarbon compounds with similar structure and physical and chemical properties, belonging to chloro-oxygenated tricyclic aromatic hydrocarbon compounds, including 75 polychlorinated dibenzo-p-dioxins (PCDDs) and 135 polychlorinated dibenzofurans (PCDFS), which are in high-temperature and oxygen-free (low-oxygen) environment (lime can be selected to participate in catalysis), the dioxins undergo dechlorination/condensation reaction, C-Cl bond is broken, Cl element is adsorbed by Ca element to form chlorine salt, other organic elements mainly comprising C, H, O are continuously thermally decomposed to form small molecular chain gas (such as H, C, H₂、CH₄CO, etc.) and fixed carbon, wherein the gas enters a gas combustion chamber to be combusted for heat supply, and the fixed carbon and other inorganic components are discharged out of the carbonization device to be comprehensively utilized.

The mechanism of heavy metal solidification is:

in the high-temperature reduction environment, the ionic heavy metal is fixed by carbon in the carbon powder to form a carbon-based composite material (C-X, X is Cr, As, Cd, Hg, Pb, Cu, Ni, Zn and the like), the heavy metal changes the existing state and cannot be separated out in the ionic state, and thus the hazardous waste identification standard leaching toxicity identification is achieved

GB5085.3-2007 and GB16889-2008 "pollution control Standard for domestic refuse landfill".

The tail gas treatment process generally comprises treatment measures of quenching and cooling, desulfurization and deacidification treatment, denitration, dust removal and the like, so that the emission standard reaches the tail gas emission standard specified in hazardous waste incineration pollution control standard (GB 18484-2001).

The method comprises the following steps: in the carbonization process of the fly ash, the slaked lime powder is an unnecessary additive, because dioxin is an organic matter, the slaked lime powder can be desorbed and thermally decomposed in a high-temperature reduction environment, when the dioxin enters a combustion chamber of a carbonization device for combustion, the slaked lime powder is fully combusted through combustion control, and the slaked lime powder is sprayed into the combustion chamber to adsorb Cl elements, so that the decomposition of the dioxin can be realized, and the aim of harmlessness is fulfilled.

Compared with the prior art, the invention has the advantages and positive effects that:

compared with the existing fly ash disposal technology, the process scheme can simultaneously solve two major hazards of the fly ash (namely leaching toxicity of dioxin and heavy metal), and the product can realize comprehensive utilization, such as being used as a cement raw material and the like.

Other features and advantages of the present invention will become more apparent from the detailed description of the embodiments of the present invention when taken in conjunction with the accompanying drawings.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a process flow diagram of a first embodiment of a fly ash carbonization treatment process according to the invention;

FIG. 2 is a process flow diagram of a second embodiment of the fly ash carbonization treatment process of the present invention;

FIG. 3 is a process flow diagram of a third embodiment of the fly ash carbonization treatment process of the invention;

FIG. 4 is a process flow diagram of a fourth embodiment of the fly ash carbonization treatment process of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples. It should be understood that the embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

Example 1

Referring to fig. 1, a fly ash carbonization treatment process adopts the following treatment steps: the collected fly ash is fully mixed with carbon powder and slaked lime powder, and then the mixture enters a high-temperature carbonization device to be heated under the anaerobic condition, so that dioxin organic matters are volatilized and thermally decomposed at first, the generated gas enters a primary combustion and secondary combustion device of the carbonization device to be fully combusted to form gas mainly comprising carbon dioxide, the solid formed by the thermal decomposition of the dioxin is mainly amorphous carbon, part of the solid enters a tail gas treatment process along with the gas, and part of the solid is precipitated to form solid carbon which is discharged out of the carbonization device and is stored and transported after being tested to meet the standard requirements. The tail gas treatment process generally comprises treatment measures of quenching and cooling, desulfurization and deacidification treatment, denitration, dust removal and the like, so that the emission standard reaches the tail gas emission standard specified in hazardous waste incineration pollution control standard (GB 18484-2001).

Wherein the carbon powder has the following quality requirements: the granularity is less than 2mm, the carbon content is more than or equal to 20 percent, and slaked lime (Ca (OH)₂) The quality requirement of the powder is as follows: the purity is more than or equal to 70 percent, and the granularity is less than or equal to 0.5 mm.

Wherein, the mixing proportion of the fly ash and the carbon powder is calculated according to the actual heavy metal and carbon content, and the weight ratio of the heavy metal to the carbon is 1: 5-1: 40; the mixing proportion of the fly ash and the slaked lime powder is calculated according to the total amount of S + Cl elements in the fly ash and the total amount of Ca elements in the slaked lime, and the ratio of S + Cl: ca 1: 2-1: 50.

wherein the temperature of the carbonization treatment is 400-900 ℃, the time of the carbonization treatment is 10-60 min, the oxygen content in the carbonization process is controlled to be less than or equal to 1%, the interior of the carbonization device is generally controlled to be slightly negative pressure, and the internal pressure is generally-10 to-100 Pa. Before the carbonization device starts to operate, the furnace is purged by using compressed nitrogen, so that the oxygen content in the carbonization device is less than or equal to 3 percent, and the nitrogen protection is also adopted in the production process. The slaked lime powder is sprayed into the gas combustion chamber of the carbonizing device while the gas is combusted to adsorb acid gas (such as HF, HCl and SOx) formed by combustion.

The method comprises the following steps: in the carbonization process of the fly ash, the slaked lime powder can be added at the beginning of carbonization alone, or the slaked lime powder is sprayed into the combustion chamber alone, or the slaked lime powder can be added in both the carbonization process and the combustion chamber.

Example 2

Referring to fig. 2, different from example 1, the carbon source is changed from carbon powder into regenerated carbon formed by carbonizing garbage, other reaction and treatment mechanisms are consistent, and the mixing ratio of fly ash and pretreated garbage is less than or equal to 1: 10.

example 3

Referring to fig. 3, the fly ash is first washed and desalted, and then enters a carbonization treatment process after precipitation, filter pressing and drying, and the moisture content of the dried fly ash is reduced to below 30%. The main purposes of water washing are desalination and heavy metal recovery, and the main purpose of carbonization is dioxin removal.

Example 4

Referring to fig. 4, different from the embodiment 3, the two processes of carbonization and water washing can be reversed, that is, the fly ash enters the carbonization treatment process first, then is washed and desalted, and the water content is reduced to below 30% after precipitation, filter pressing and drying.

The total amount of fly ash produced by a certain refuse incineration plant is 10 tons, 1.5 tons of waste charcoal powder (with 85% of carbon content) is doped, the mixture is fully stirred and then continuously enters a high-temperature high-speed carbonization device, and the mixture is discharged out of the carbonization device after being continuously heated for 20 minutes under the environment that the oxygen content is less than or equal to 0.5% and the internal temperature is more than or equal to 700 ℃, and then is cooled and stored.

Comparison before and after treatment:

original fly ash pollution indexes:

pollution indexes of treated fly ash are as follows:

description of the drawings: "-" indicates that the detection limit is lower.

Therefore, the fly ash treated by the carbonization treatment process has greatly reduced content of various heavy metals and much reduced content of dioxin, and reaches the emission standard specified in hazardous waste incineration pollution control standard (GB 18484-2001).

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.