CN112275783A

CN112275783A - Fly ash detoxification treatment method and device

Info

Publication number: CN112275783A
Application number: CN202011230605.1A
Authority: CN
Inventors: 余广炜; 王玉; 汪印
Original assignee: Institute of Urban Environment of CAS
Current assignee: Institute of Urban Environment of CAS
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2021-01-29

Abstract

The invention belongs to the technical field of fly ash treatment, and relates to a fly ash detoxification treatment method and equipment. The fly ash detoxification treatment method comprises the following steps: uniformly mixing fly ash and biogas residue, forcibly stirring to obtain premixed mortar, heating and stirring the premixed mortar at 100-180 ℃ under a closed condition for 0.5-1 h to obtain heated mortar, and carrying out solid-liquid separation on the heated mortar to obtain liquid and solid; the liquid is discharged after being treated by sewage until the liquid reaches the standard; and pyrolyzing the solid at 400-600 ℃ to obtain pyrolysis residues, wherein the pyrolysis residues are used as solid wastes for landfill or as inorganic materials for preparing ceramics or baked bricks. The method can realize the detoxification of the fly ash and the stable solidification of the heavy metal by utilizing the biogas residues, thoroughly eliminate dioxin substances in the fly ash, avoid secondary pollution, realize the high-efficiency dehydration of the biogas residues and the cooperative resource utilization of dehydration products by utilizing the fly ash, and solve the problem of low-cost treatment of the fly ash and the biogas residues.

Description

Fly ash detoxification treatment method and device

Technical Field

The invention belongs to the technical field of fly ash treatment, and particularly relates to a fly ash detoxification treatment method and equipment.

Background

In recent years, with the rapid development of Chinese economy, the urbanization process is accelerated, and the production amount and accumulation amount of household garbage are increased year by year. The realization of harmlessness, reduction and recycling of household garbage is the key to solve the problem of 'enclosing a garbage city'. Incineration not only has the advantages of volume reduction of 90% and weight reduction of more than 75%, but also has thorough decomposition and high harmless degree to pollutants, and simultaneously, waste incineration can also generate heat energy for use and gradually becomes a mainstream treatment technology. According to statistics, the domestic waste incineration disposal capacity of China reaches 29.81 ten thousand tons/day, and the situation of continuous growth is shown. The quantity is extremely large by calculating the generation quantity of the waste incineration fly ash accounting for 3 percent of the total quantity of the waste treatment. The incineration fly ash contains various complex pollutants, including soluble chloride (NaCl and KCl), volatile heavy metals (Hg, Cd, Pb, As, Cr, Cu and Zn) and PCDD/Fs with strong toxicity. If the pollutants are directly discharged without treatment, various pollutants are released into environmental media (such as atmosphere, water and soil) through various channels, so that a large environmental risk is generated, the balance of an original ecological system is damaged, and the life safety of human beings is seriously threatened. In 2008, fly ash is listed in national hazardous waste records, the hazardous waste number is HW18, and the fly ash can be subjected to harmless detoxification treatment and can be subjected to landfill or subsequent resource utilization. On the other hand, in China, the process of converting organic solid waste into methane by anaerobic fermentation is widely applied, so that the yield of residue biogas residues is huge. According to the estimation, the yield of the biogas residues and the biogas liquid in China is up to 4 hundred million tons every year at present, and most of the biogas residues and the biogas liquid cannot be reasonably treated and utilized. The biogas residue contains a large amount of nutrients for plant growth such as organic matters, N, P, K, trace elements and the like, and also contains substances polluting the environment. The biogas residues are directly used for land without reasonable treatment and have the following potential risks: firstly, the un-decomposed biogas residues compete with crops for oxygen in soil, and root system development of the crops is influenced; secondly, the biogas residues may contain toxic and harmful substances such as antibiotics, heavy metals, pathogenic bacteria and the like, and the direct land utilization has safety risk. In addition, the factors such as high water content of the biogas residues, high viscosity, difficult dehydration and the like directly influence the resource utilization. Therefore, the efficient dehydration, drying, reduction treatment and resource utilization of the biogas residues become a technical bottleneck problem to be solved urgently for industrial popularization of biogas engineering.

Regarding the treatment of fly ash, CN104607434A discloses a method for solidifying fly ash from incineration of household garbage, which comprises mixing the fly ash from incineration of garbage, strontium carbonate waste residue, potassium carbonate and cement in parts by mass (40-50) to (25-38) to (3-6) to (15-25), solidifying and curing to obtain a solidified body which can be directly buried. The method takes the strontium carbonate waste residue as an important raw material for solidifying the fly ash, thereby reducing the using amount of cement. CN105585288A discloses a stabilizing and solidifying agent for fly ash from incineration of garbage and a method for treating fly ash from incineration of municipal solid waste, wherein the stabilizing and solidifying agent is composed of a heavy metal stabilizer, water and cement. The main goal of the process is to reduce the cement dosage and the set block compatibilization ratio. CN101972766A discloses a method for solidifying/stabilizing fly ash from incineration of garbage, which comprises fully preparing a heavy metal stabilizer and water into a solution, mixing the solution with fly ash from incineration of garbage and a small amount of cement, stirring, and curing. The method achieves the aim that the fly ash is stable in double effects and has certain strength so as to be beneficial to landfill. CN104492024A discloses a method for treating fly ash from waste incineration, which adopts calcium oxide and disodium hydrogen phosphate to form a dense network cement to realize the solidification of fly ash from waste incineration, improves the strength of the solidified body of fly ash, passivates the fly ash pollutants, adopts ferric chloride to stabilize the fly ash mortar, and reduces the release of phosphorus in the solidified body of fly ash by forming a compound with stable phosphorus and iron. However, this approach is relatively costly.

Regarding the treatment of biogas residues, CN107469768A discloses a preparation method of livestock and poultry manure biogas residue biochar, which is prepared by using livestock and poultry manure biogas residues as raw materials and carrying out oxygen-limited slow pyrolysis carbonization. CN109809403A discloses that after being dried and crushed, the anaerobic fermentation biogas residue is mixed with an activating agent in an inert gas atmosphere, co-ground, placed in the inert gas atmosphere, activated at the temperature of 500-800 ℃, cooled to obtain activated biogas residue biochar, and rinsed to be neutral to obtain biogas residue-based activated carbon. CN107469768A discloses a livestock and poultry manure biogas residue biochar/manganese oxide composite material and a preparation method thereof, wherein livestock and poultry manure biogas residue is used as a raw material, and is subjected to oxygen-limited slow pyrolysis carbonization to prepare livestock and poultry manure biogas residue biochar; the biochar of the livestock and poultry manure biogas residues is firstly deashed and dried by hydrochloric acid, then is immersed in a potassium permanganate solution and is subjected to ultrasonic treatment, so that the biochar/manganese oxide composite material of the livestock and poultry manure biogas residues is obtained and is used for treating a water body containing heavy metal/antibiotic composite pollutants. The method only relates to the independent disposal of the biogas residues, has relatively complex working procedures and higher cost, and does not relate to the detoxification treatment of the fly ash by using the biogas residues or the conditioning of the biogas residues by using the fly ash.

Regarding the mixed treatment of biogas residues and fly ash, CN107497094A discloses a method for treating waste incineration fly ash by using biogas residues, firstly transferring fly ash into a storage yard, then laying an impermeable layer in the storage yard, laying a flow guide material at the bottom, laying a mixed layer of biogas residues, a carbon source, sulfate, a nutritional additive and fly ash at the upper part of the mixed layer, and placing a mixed layer of a titanium-containing material and a nano-iron material at the upper part of the mixed layer; in the operation process, carbon source solution is injected from the upper part of the storage yard at irregular intervals, the percolate is collected into a percolate collecting system through a bottom diversion material at irregular intervals, and then the percolate is refluxed to the top of the storage yard for spraying and recharging. By adopting the method to treat the fly ash, the heavy metals in the fly ash can be fixed in a storage yard, and the dioxin in the fly ash can be degraded at the same time. Extracting dioxin in fly ash into leachate by using carbon source solutions such as ethanol and the like, adsorbing the dioxin by a nano iron material, and forming a photocatalytic effect to promote the decomposition of the dioxin under the action of a titanium-containing material; the pH value is adjusted to generate Fenton catalytic effect, and refractory organic matters generated by the biogas residues are removed. However, the method has complex process and higher cost, does not carry out reduction treatment on the fly ash and the biogas residues, and is suitable for landfill treatment of the fly ash.

In summary, the research and application of utilizing anaerobic fermentation biogas residue to detoxify and recycle fly ash are still insufficient.

Disclosure of Invention

The invention aims to provide a novel fly ash detoxification treatment method and equipment, on one hand, biogas residues are utilized to realize fly ash detoxification, stable solidification of heavy metals is realized, dioxin substances in fly ash are thoroughly eliminated, and secondary pollution is avoided; on the other hand, the fly ash is utilized to realize the high-efficiency dehydration of the biogas residues and the cooperative resource utilization of dehydration products, thereby solving the problem of low-cost treatment of the fly ash and the biogas residues.

Specifically, the invention provides a fly ash detoxification treatment method, which comprises the following steps:

(1) uniformly mixing fly ash and biogas residues, and forcibly stirring the obtained mixture to obtain premixed mortar;

(2) heating and stirring the premixed mortar at 100-180 ℃ for 0.5-1 h under a closed condition to obtain heated mortar;

(3) carrying out solid-liquid separation on the heated mortar to obtain liquid and solid; the liquid is discharged after being treated by sewage until the liquid reaches the standard; and pyrolyzing the solid at 400-600 ℃ to obtain pyrolysis residues, wherein the pyrolysis residues are used as solid wastes for landfill or as inorganic materials for preparing ceramics or baked bricks.

Further, in step (1), the fly ash is sourced from a conventional waste incineration site; the biogas residues are generated by anaerobic fermentation of kitchen waste or livestock and poultry manure, and the water content of the biogas residues is 80-95%.

Further, in the step (1), the fly ash and the biogas residue are mixed according to the mass ratio of the wet basis (10-30%) to the wet basis (90-70%).

Further, in the step (1), the forced stirring speed is 50-100 r/min, and the time is 0.5-1 h.

Further, in the step (2), the heating and stirring speed is 30-50 r/min.

Further, in the step (3), the solid-liquid separation mode is filter pressing or centrifugal separation.

Further, in the step (3), the filter pressing mode is plate-frame filter pressing.

Further, in the step (3), the pyrolysis time is 30-60 min.

The invention also provides a fly ash detoxification treatment device, wherein the device comprises: the system comprises a fly ash storage bin, a biogas residue storage pool, a No. 1 conveying device, a No. 2 conveying device, a premixing device, a No. 3 conveying device, a heating and stirring device, a No. 4 conveying device, a solid-liquid separation device, a No. 5 conveying device, a pyrolysis and carbonization device, a combustion device, a cooling device, a No. 7 conveying device, a No. 8 conveying device, a detoxified residue storage bin, a No. 9 conveying device, a tail gas purification device, a No. 6 conveying device and a sewage treatment device;

the outlet of the fly ash storage bin is connected with the inlet of the No. 1 conveying device, and the outlet of the No. 1 conveying device is connected with the fly ash inlet of the premixing device; the outlet of the biogas residue storage pool is connected with the inlet of a No. 2 conveying device, and the outlet of the No. 2 conveying device is connected with the biogas residue inlet of the premixing device; the outlet of the premixing device is connected with the inlet of the 3# conveying device, the outlet of the 3# conveying device is connected with the inlet of the heating and stirring device, the solid outlet of the heating and stirring device is connected with the inlet of the 4# conveying device, and the outlet of the 4# conveying device is connected with the inlet of the solid-liquid separation device; the liquid phase discharge port of the solid-liquid separation device is connected with the inlet of the No. 6 conveying device, and the outlet of the No. 6 conveying device is connected with the inlet of the sewage treatment device; the solid-phase discharge port of the solid-liquid separation device is connected with the inlet of the No. 5 conveying device, and the outlet of the No. 5 conveying device is connected with the inlet of the pyrolysis carbonization device; the solid outlet of the pyrolysis carbonization device is connected with the inlet of the cooling device, the solid outlet of the cooling device is connected with the inlet of the 8# conveying device, and the outlet of the 8# conveying device is connected with the inlet of the detoxified residue storage bin; the pyrolysis gas outlet of the pyrolysis carbonization device is connected with the inlet of the combustion device, and the flue gas outlet of the combustion device is connected with the high-temperature flue gas inlet of the pyrolysis carbonization device; the tail gas outlet of the flue gas of the pyrolysis carbonization device is connected with the inlet of the flue gas of the heating and stirring device, the outlet of the flue gas of the heating and stirring device is connected with the inlet of the No. 9 conveying device, and the outlet of the No. 9 conveying device is connected with the inlet of the tail gas purification device; and the outlet of the 7# conveying device is connected with the air inlet of the combustion device.

Further, the fly ash storage bin and the detoxified residue storage bin are common steel bins.

Further, the biogas residue storage pool is a concrete pool.

Further, the No. 1 conveying device and the No. 8 conveying device are respectively and independently a pneumatic conveyor, a scraper conveyor or a screw conveyor.

Further, the No. 2 conveying device, the No. 3 conveying device and the No. 4 conveying device are slurry pumps.

Further, the premixing device is a common steel electric stirring tank.

Further, the heating and stirring device is a closed common steel electric stirring tank with an indirect heating device.

Further, the solid-liquid separation device is a plate-and-frame filter press or a centrifugal dehydrator.

Further, the No. 5 conveying device is a spiral conveyor, a belt conveyor, a scraper conveyor or a bucket elevator.

Further, the pyrolysis carbonization device is a common indirect heating rotary kiln.

Further, the combustion device is a common gas burner.

Further, the cooling device is a rotary drum cooling conveyor.

Further, the 7# conveying device is an air induced draft fan.

Further, the 9# conveying device is a smoke induced draft fan.

Further, the tail gas purification device is a common wet tail gas purifier or a dry tail gas purifier.

Further, the No. 6 conveying device is a sewage pump.

Further, the sewage treatment device is a conventional sewage treatment device.

In the process of forcibly stirring the fly ash and the biogas residues, the fly ash is mixed with viscous biogas residues with high water content, so that high-content alkali, chloride and soluble heavy metals in the fly ash can be efficiently leached. On the other hand, the biogas residues are used as products of anaerobic digestion of organic wastes, have high water content and high viscosity, are in a colloidal liquid state, are difficult to dehydrate, and are difficult to carry out solid-liquid separation through gravity settling or conventional filter pressing, and alkali and chloride dissolved out of fly ash can be used as biogas residue conditioners, so that the structure of colloids is changed, the stability of the colloids is destroyed, the rapid wall breaking of water-containing cells is realized, and the dehydration performance of the biogas residues can be greatly improved under the condition of not using chemical agents.

The premixed mortar of the fly ash and the biogas residues is heated and stirred for 0.5-1 h at 100-180 ℃ under a closed condition, so that on one hand, the fly ash and organic and inorganic components in the biogas residues can act synergistically, heavy metals in the fly ash are converted into a stable residue state, and the curing effect on toxic and harmful metal elements such as Cd, Cr, Cu, Ni, Pb, Zn and the like is remarkably improved; on the other hand, the hydrogenation dechlorination reaction of the dioxin in the fly ash and the organic matter thermal hydrolysis product in the biogas residue is promoted in the heating and stirring process, so that the dioxin detoxification is facilitated. When the temperature of the heating and stirring treatment is lower than 100 ℃ and/or the time is shorter than 0.5h, the dioxin organic pollutants in the fly ash cannot be efficiently and thoroughly decomposed, and the effect of reducing the solidification of heavy metals cannot be ensured; when the temperature of the heating and stirring treatment is higher than 180 ℃ and/or the time is longer than 1h, the high-efficiency complete decomposition of dioxin organic pollutants in the fly ash and the solidification of heavy metals are not obviously improved, the energy is wasted, and the treatment capacity is reduced.

And performing solid-liquid separation on the heated mortar to obtain solid, and performing pyrolysis at 400-600 ℃, so that large-scale reduction of the mixture of fly ash and biogas residue can be realized. On one hand, the content of organic matters in the biogas residues is high, the residue state content of heavy metal elements can be further improved and the leachability of heavy metals in pyrolysis residues can be reduced by utilizing the action of free radicals in the pyrolysis process of the biogas residues and the solidification performance of the pyrolysis porous carbon, and the further deep detoxification of dioxin can be synchronously realized. When the pyrolysis temperature is lower than 400 ℃, efficient pyrolysis reduction cannot be realized, and the decomposition efficiency of the solidified heavy metal and dioxin of the biogas residue cannot be fully exerted; when the pyrolysis temperature is higher than 600 ℃, the complete pyrolysis of the heated mortar solid is not influenced, and the heavy metal curing and dioxin reduction effects in the pyrolysis residue are not obviously improved.

In conclusion, the method and the device provided by the invention are adopted to detoxify the fly ash, and the refractory wastes such as biogas residues are used as the medium for detoxifying the fly ash, so that on one hand, water in the biogas residues is used for dissolving high-content alkali, chloride and soluble heavy metals in the fly ash, and dechlorination of the fly ash and dissolution of the soluble heavy metals are realized; on the other hand, dissolved alkali or salt is fully utilized, so that bound water (microbial intracellular water) in the biogas residues can rapidly destroy cell walls, the bound water which is most difficult to remove is changed into external water which is easy to remove by a stirring and heating mode in a closed space, efficient dehydration can be realized by a mechanical dehydration mode and the like, the biogas residue dehydration efficiency is improved, heavy metals are solidified and stabilized, and meanwhile, efficient hydrolysis and detoxification of dioxin substances in fly ash are realized. The chlorine content in the solid and the liquid obtained by solid-liquid separation is obviously reduced, and the stability of heavy metal is improved. The solid is reduced by adopting pyrolysis treatment, the action of free radicals in the pyrolysis process of the biogas residues and the curing performance of the pyrolyzed porous carbon are fully utilized, the content of heavy metal element residues in the pyrolyzed residues is further improved, deep curing and detoxification of the heavy metal elements are realized, the leachability of the heavy metals in the pyrolyzed residues is greatly reduced, the long-term stability of the pyrolyzed residues is improved, and the content of dioxin is reduced by more than 99%. Pyrolysis residues generated by detoxification of the fly ash are cooled and then used as general solid wastes for landfill or further used as inorganic materials, so that the fly ash and biogas residues are cooperatively utilized, the wastes are treated by the wastes, and the problem of treatment of the fly ash and the biogas residues is solved, which has important significance for promoting sustainable development of the waste incineration industry and the organic solid waste anaerobic fermentation industry.

Drawings

FIG. 1 is a process flow diagram of a fly ash detoxification treatment method according to the present invention;

FIG. 2 is a schematic view of a fly ash detoxification treatment apparatus provided by the present invention;

FIG. 3 is a graph comparing the solids content of samples treated in example 2;

FIG. 4 is a graph showing the drying characteristics of the dehydrated solid phase of the sample treated in example 2.

Description of the reference numerals

1-fly ash storage bin, 2-biogas residue storage tank, 3-1# conveying device, 4-2# conveying device, 5-premixing device, 6-3# conveying device, 7-heating stirring device, 8-4# conveying device, 9-solid-liquid separation device, 10-5# conveying device, 11-pyrolysis carbonization device, 12-combustion device, 13-cooling device, 14-7# conveying device, 15-8# conveying device, 16-detoxication residue storage bin, 17-9# conveying device, 18-tail gas purification device, 19-6# conveying device and 20-sewage treatment device.

Detailed Description

The present invention will be described in detail below.

In one embodiment, as shown in fig. 1, the method for detoxifying fly ash provided by the present invention comprises: premixing fly ash and biogas residue (forcibly stirring and mixing after primary mixing) to obtain premixed mortar, and then stirring and heating the premixed mortar; and (2) carrying out solid-liquid separation on the heated mortar obtained by stirring and heating treatment, allowing the liquid to enter a sewage treatment system for treatment until the heated mortar reaches the standard and is discharged, carrying out pyrolysis and carbonization on the solid, cooling pyrolysis residues (detoxified residues) obtained by pyrolysis and carbonization, burying the cooled pyrolysis residues as solid wastes or using the cooled pyrolysis residues as inorganic materials for preparing ceramics or sintered bricks so as to realize resource utilization, burning pyrolysis gas obtained by pyrolysis and carbonization as energy, using high-temperature flue gas generated by burning as pyrolysis and carbonization energy, returning flue gas tail gas obtained by pyrolysis and carbonization as an indirect heating source to the stirring and heating treatment step, and treating the flue gas tail gas subjected to heat exchange to reach. Preferably, the red hot pyrolysis residue is cooled by cold air heat exchange, and hot air generated by the red hot pyrolysis residue is used as fuel combustion air.

In the present invention, the term "fly ash" refers to fly ash produced by a waste incineration system, and is numbered HW18 in the national records of hazardous wastes.

In the present invention, the term "biogas residue" refers to an aqueous solid remaining after fermentation of organic substances, and may be, for example, biogas residue produced by anaerobic fermentation of kitchen waste or livestock and poultry manure. The water content of the biogas residues is generally 80-95%.

In the invention, in the step (1), the fly ash and the biogas residue are preferably mixed according to the mass ratio of the wet basis (10-30%) to the wet basis (90-70%), the mixing ratio of the fly ash and the biogas residue is controlled within the preferred range, and the fly ash and the biogas residue can realize perfect synergistic cooperation, so that the dehydration efficiency is more effectively improved, and the solidification stability of heavy metals in the fly ash is more favorably realized.

In the invention, in the step (1), the speed of the forced stirring is preferably 50-100 r/min, and the time is preferably 0.5-1 h.

In the present invention, in the step (1), the temperature of the heating and stirring treatment is 100 to 180 ℃, and for example, may be 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃ or the like; the time of the heating and stirring treatment is 0.5 to 1 hour, and for example, may be 0.5 hour, 0.6 hour, 0.7 hour, 0.8 hour, 0.9 hour, 1 hour, or the like. The rate of the heating and stirring treatment is preferably 30 to 50r/min, and may be, for example, 30, 35, 40, 45, 50r/min or the like.

In the present invention, in the step (3), the pyrolysis temperature is 400 to 600 ℃, and for example, 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃ or the like may be used. In addition, the pyrolysis time is preferably 30 to 60min, and for example, may be 30min, 35min, 40min, 45min, 50min, 55min, 60min, or the like.

As shown in fig. 2, the present invention provides a fly ash detoxification treatment apparatus comprising: the device comprises a fly ash storage bin 1, a biogas residue storage pool 2, a No. 1 conveying device 3, a No. 2 conveying device 4, a premixing device 5, a No. 3 conveying device 6, a heating and stirring device 7, a No. 4 conveying device 8, a solid-liquid separation device 9, a No. 5 conveying device 10, a pyrolysis and carbonization device 11, a combustion device 12, a cooling device 13, a No. 7 conveying device 14, a No. 8 conveying device 15, a detoxified residue storage bin 16, a No. 9 conveying device 17, a tail gas purification device 18, a No. 6 conveying device 19 and a sewage treatment device 20, wherein the components are connected in the following sequence:

the outlet of the fly ash storage bin 1 is connected with the inlet of a No. 1 conveying device 3, and the outlet of the No. 1 conveying device 3 is connected with the fly ash inlet of a premixing device 5; an outlet of the biogas residue storage pool 2 is connected with an inlet of a No. 2 conveying device 4, and an outlet of the No. 2 conveying device 4 is connected with a biogas residue inlet of a premixing device 5; an outlet of the premixing device 5 is connected with an inlet of a No. 3 conveying device 6, an outlet of the No. 3 conveying device 6 is connected with an inlet of a heating and stirring device 7, a solid outlet of the heating and stirring device 7 is connected with an inlet of a No. 4 conveying device 8, and an outlet of the No. 4 conveying device 8 is connected with an inlet of a solid-liquid separation device 9; the liquid phase discharge port of the solid-liquid separation device 9 is connected with the inlet of a No. 6 conveying device 19, and the outlet of the No. 6 conveying device 19 is connected with the inlet of a sewage treatment device 20; the solid-phase discharge port of the solid-liquid separation device 9 is connected with the inlet of a No. 5 conveying device 10, and the outlet of the No. 5 conveying device 10 is connected with the inlet of a pyrolysis carbonization device 11; the solid outlet of the pyrolysis carbonization device 11 is connected with the inlet of a cooling device 13, the solid outlet of the cooling device 13 is connected with the inlet of a No. 8 conveying device 15, and the outlet of the No. 8 conveying device 15 is connected with the inlet of a detoxified residue storage bin 16; the pyrolysis gas outlet of the pyrolysis and carbonization device 11 is connected with the inlet of the combustion device 12, and the flue gas outlet of the combustion device 12 is connected with the high-temperature flue gas inlet of the pyrolysis and carbonization device 11; the tail gas outlet of the flue gas of the pyrolysis and carbonization device 11 is connected with the flue gas inlet of the heating and stirring device 7, the flue gas outlet of the heating and stirring device 7 is connected with the inlet of the No. 9 conveying device 17, and the outlet of the No. 9 conveying device 17 is connected with the inlet of the tail gas purification device 18; the outlet of the cooling device 13 for preheating air is connected with the inlet of the 7# delivery device 14, and the outlet of the 7# delivery device 14 is connected with the air inlet of the combustion device 12.

When the device works, the fly ash stored in the fly ash storage bin 1 is conveyed into a premixing device 5 through a No. 1 conveying device 3, the biogas residue stored in a biogas residue storage pool 2 is conveyed into the premixing device 5 through a No. 2 conveying device 4, the fly ash and the biogas residue are uniformly mixed in the premixing device 5, the obtained mixture is conveyed into a stirring and heating device 7 through a No. 3 conveying device 6 for heating and stirring treatment, the obtained tail gas is conveyed into a tail gas purifying device 18 through a No. 9 conveying device 17 for purifying treatment and then is discharged after reaching the standard, the obtained heated mortar is conveyed into a solid-liquid separation device 9 through a No. 4 conveying device 8 for solid-liquid separation, the liquid obtained by solid-liquid separation is conveyed into a sewage treatment device 20 through a No. 6 conveying device 19 for sewage treatment and is discharged after reaching the standard, the solid obtained by solid-liquid separation is conveyed into a pyrolysis and carbonization device 11 through a No. 5 conveying device 10 for pyrolysis and carbonization, and, high-temperature flue gas generated by the combustion device 12 is returned to the pyrolysis and carbonization device 11 as pyrolysis and carbonization energy, pyrolysis residues obtained by pyrolysis and carbonization are cooled by a cooling device 13 and then are sent to a detoxified residue storage bin 16 for storage through a No. 8 conveying device 15; the hot air generated by heat exchange between the cold air and the red hot residue in the cooling device 13 is sent into the combustion device 12 through the 7# conveying device 14 for fuel combustion-supporting air, and the flue gas tail gas generated by the pyrolysis carbonization device 11 is used as an indirect heating source and is returned to the stirring heating device 7.

In the invention, the heat generated by the combustion of the pyrolysis gas generated in the pyrolysis process is used as the energy source of the pyrolysis process; the flue gas tail gas generated by the combustion of the pyrolysis gas is used as a heat source for indirect heating in the stirring, heating and mixing process, so that the energy consumption is reduced, and the energy utilization rate is improved.

The following examples further illustrate the invention.

Example 1

Mixing biogas residues with a certain mass (water content is 80%) and fly ash accounting for 20% of the mass of wet biogas residues, and strongly stirring at a rotating speed of 100r/min for 0.5h to obtain premixed mortar; the premixed mortar is heated and stirred for 60min at 180 ℃ under a closed condition to obtain heated mortar. And carrying out solid-liquid separation on the heated mortar in a filter pressing mode to obtain liquid and solid. And (3) putting the liquid into a sewage treatment system of a sewage treatment plant for treatment and discharging after reaching the standard. And carrying out pyrolysis carbonization treatment on the solid at 600 ℃ for 40min to obtain detoxified residue. The generated pyrolysis gas is combusted to generate heat to provide heat for the pyrolysis process, and high-temperature flue gas generated by combustion of the pyrolysis gas is used for a heat source to heat the premixed mortar. The leaching property of the heavy metal in the detoxified residue is determined by a method of HJ/T299-2007, and is lower than GB5085.3-2007 standard, and the dioxin elimination amount is more than 99%. Therefore, the fly ash detoxified residue can be used as an inorganic material raw material for producing ceramsite or baked brick, and can also be used as general solid waste for landfill.

Example 2

Mixing wet base biogas residue with fly ash, wherein the addition proportion of the fly ash is 20 percent of the mass of the wet biogas residue. The premixed mortar is obtained by stirring vigorously for 0.5h at the rotating speed of 100r/min, and the premixed mortar is stirred and heated for 60min at 180 ℃ under the closed condition to obtain heated mortar which is named as BR + FA. The heated slurry was placed in a floor centrifuge and centrifuged at 3000r/min for 20min at 25 ℃ after which the supernatant was removed to give a centrifugally dewatered solid phase. Drying the centrifugal dehydration solid phase at 105 ℃ for 24h to obtain the solid content; and (3) continuously heating the centrifugally dehydrated solid phase in a constant-temperature oven at 75 ℃, recording the change of the water content every 15min until the change is not changed, and obtaining a curve of the change of the water content along with time, namely a dehydrated solid phase drying characteristic curve. The solid holdup and drying characteristic curve can be used for representing the effect of adding fly ash to dewater and improve the biogas residues by adopting the method provided by the invention. For better comparison, 100% biogas residue heated mortar (BR) was obtained using the same processes and parameters as described above and compared with a biogas residue sample (raw material) without any treatment, and the results are shown in fig. 3 and 4.

As is apparent from fig. 3, the solid content in the solid phase of the untreated biogas residue after centrifugal dehydration is 18.21%, and the solid content in the solid phase (BR) obtained by the biogas residue after direct heating treatment without adding fly ash is 20.94%, which is not obviously improved. After 20% of fly ash is added, the solid content in the solid phase obtained by centrifugally dehydrating the biogas residue and fly ash heated mortar is 38.66%, which is improved by 84.62% compared with BR, which shows that the dehydration performance of the biogas residue can be obviously improved by adding the fly ash and the biogas residue for synergistic treatment, and the method has important significance for the reduction treatment of the biogas residue. The above results are also verified from the drying curve of fig. 4, and the water content of the slurry mixture of biogas residue and fly ash is always lower than that of the other comparative groups at the same drying time point. In conclusion, the biogas residues are used as the fly ash detoxification medium, so that on one hand, the fly ash detoxification harmless treatment can be realized by utilizing the biogas residues, on the other hand, the fly ash can fully exert the function of the biogas residue dehydration conditioner, the dehydration performance of the biogas residues is improved, and the aims of cooperative reduction and resource utilization of the fly ash and the biogas residues are fully reflected.

Example 3

Heating 100% biogas residue to filter-press solid phase (BRH), mixing 80% biogas residue with 20% fly ash, heating and filter-press solid phase (BR + FAH), oven drying, and performing pyrolysis experiment. And respectively taking 30g of experimental samples, and loading the experimental samples into a tubular pyrolysis furnace for pyrolysis. And introducing 20mL/min nitrogen as a protective gas in the pyrolysis process, heating the mixture from room temperature to 600 ℃ at the heating rate of 15 ℃/min, keeping the temperature for 45min, finishing pyrolysis, cooling the mixture to room temperature along with a pyrolysis furnace, and obtaining pyrolysis residues which are respectively marked as BRHC, BR and FAHC. The dry samples of BRH, BRHC, BR + FAH and BR + FAHC were analyzed for the leachability of heavy metals TCLP and compared with the dry samples of raw materials of Biogas Residue (BR) and Fly Ash (FA), and the results are shown in the table.

TABLE 1 analysis of samples for heavy metals TCLP/(mg/L)

*US-EPA(1993)

The TCLP leaching toxicity analysis result in the table 1 shows that the leaching performance of heavy metal TCLP in the biogas residue meets the environmental requirement; the TCLP leachability of heavy metals such as Cr, Zn, Pb and the like in the fly ash exceeds the standard, and particularly, the Pb exceeds the standard by more than 40 times. The biogas residues are used as fly ash detoxification carriers, and the leaching property of TCLP of all heavy metals in the detoxification residues (BR + FAHC) obtained by the method provided by the invention is obviously reduced and is far lower than the limit value in the USEPA standard, which shows that the application of the biogas residues as the detoxification residues generated by fly ash detoxification treatment can not bring potential safety risks. In conclusion, the method provided by the invention can realize the detoxification and harmless treatment of the fly ash, can realize the high-efficiency dehydration and resource utilization of the anaerobic fermentation biogas residues, and can not bring new environmental problems.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.

Claims

1. A fly ash detoxification treatment method is characterized by comprising the following steps:

2. A fly ash detoxification treatment method according to claim 1, wherein in step (1), said fly ash is derived from a conventional waste incineration site; the biogas residues are generated by anaerobic fermentation of kitchen waste or livestock and poultry manure, and the water content of the biogas residues is 80-95%.

3. The method for detoxifying fly ash according to claim 2, wherein the fly ash is mixed with biogas residue at a wet basis mass ratio (10% -30%) (90% -70%).

4. A fly ash detoxification treatment method according to any of claims 1 to 3, wherein in the step (1), the forced stirring is performed at a speed of 50 to 100r/min for a time of 0.5 to 1 h.

5. A fly ash detoxification treatment method according to any of claims 1 to 3, wherein in the step (2), the heating and stirring treatment is performed at a rate of 30 to 50 r/min.

6. A fly ash detoxification treatment method according to any one of claims 1 to 3, wherein in the step (3), the solid-liquid separation is filter pressing or centrifugal separation.

7. A fly ash detoxification treatment method according to claim 6, wherein in step (3), the filter pressing mode is plate-and-frame filter pressing.

8. A fly ash detoxification treatment method according to any of claims 1 to 3, wherein in the step (3), the pyrolysis time is 30 to 60 min.

9. A fly ash detoxification treatment apparatus, comprising: the system comprises a fly ash storage bin (1), a biogas residue storage pool (2), a No. 1 conveying device (3), a No. 2 conveying device (4), a premixing device (5), a No. 3 conveying device (6), a heating stirring device (7), a No. 4 conveying device (8), a solid-liquid separation device (9), a No. 5 conveying device (10), a pyrolysis carbonization device (11), a combustion device (12), a cooling device (13), a No. 7 conveying device (14), a No. 8 conveying device (15), a detoxified residue storage bin (16), a No. 9 conveying device (17), a tail gas purification device (18), a No. 6 conveying device (19) and a sewage treatment device (20);

the outlet of the fly ash storage bin (1) is connected with the inlet of a No. 1 conveying device (3), and the outlet of the No. 1 conveying device (3) is connected with the fly ash inlet of the premixing device (5); the outlet of the biogas residue storage pool (2) is connected with the inlet of a No. 2 conveying device (4), and the outlet of the No. 2 conveying device (4) is connected with the biogas residue inlet of a premixing device (5); the outlet of the premixing device (5) is connected with the inlet of a 3# conveying device (6), the outlet of the 3# conveying device (6) is connected with the inlet of a heating and stirring device (7), the solid outlet of the heating and stirring device (7) is connected with the inlet of a 4# conveying device (8), and the outlet of the 4# conveying device (8) is connected with the inlet of a solid-liquid separation device (9); the liquid phase discharge port of the solid-liquid separation device (9) is connected with the inlet of a No. 6 conveying device (19), and the outlet of the No. 6 conveying device (19) is connected with the inlet of a sewage treatment device (20); the solid-phase discharge port of the solid-liquid separation device (9) is connected with the inlet of a No. 5 conveying device (10), and the outlet of the No. 5 conveying device (10) is connected with the inlet of a pyrolysis carbonization device (11); the solid outlet of the pyrolysis carbonization device (11) is connected with the inlet of the cooling device (13), the solid outlet of the cooling device (13) is connected with the inlet of the 8# conveying device (15), and the outlet of the 8# conveying device (15) is connected with the inlet of the detoxified residue storage bin (16); the pyrolysis gas outlet of the pyrolysis carbonization device (11) is connected with the inlet of the combustion device (12), and the flue gas outlet of the combustion device (12) is connected with the high-temperature flue gas inlet of the pyrolysis carbonization device (11); the tail gas outlet of the flue gas of the pyrolysis carbonization device (11) is connected with the flue gas inlet of the heating and stirring device (7), the flue gas outlet of the heating and stirring device (7) is connected with the inlet of a 9# conveying device (17), and the outlet of the 9# conveying device (17) is connected with the inlet of a tail gas purification device (18); the outlet of the preheating air of the cooling device (13) is connected with the inlet of a 7# conveying device (14), and the outlet of the 7# conveying device (14) is connected with the air inlet of the combustion device (12).

10. The fly ash detoxification treatment apparatus according to claim 9,

the fly ash storage bin (1) and the detoxified residue storage bin (16) are common steel bins;

the biogas residue storage pool (2) is a concrete pool;

the No. 1 conveying device (3) and the No. 8 conveying device (15) are respectively and independently a pneumatic conveyor, a scraper conveyor or a screw conveyor;

the 2# conveying device (4), the 3# conveying device (6) and the 4# conveying device (8) are slurry pumps;

the premixing device (5) is a common steel electric stirring tank;

the heating and stirring device (7) is a closed common steel electric stirring tank with an indirect heating device;

the solid-liquid separation device (9) is a plate-and-frame filter press or a centrifugal dehydrator;

the No. 5 conveying device (10) is a spiral conveyor, a belt conveyor, a scraper conveyor or a bucket elevator;

the pyrolysis carbonization device (11) is a common indirect heating rotary kiln;

the combustion device (12) is a common gas burner;

the cooling device (13) is a rotary drum cooling conveyor;

the 7# conveying device (14) is an air induced draft fan;

the No. 9 conveying device (17) is a flue gas induced draft fan;

the tail gas purification device (18) is a common wet tail gas purifier or a dry tail gas purifier;

the No. 6 conveying device (19) is a sewage pump;

the sewage treatment device (20) is a conventional sewage treatment device.