CN114671589B

CN114671589B - Method for synergistic harmless recycling treatment of oil sludge and fly ash

Info

Publication number: CN114671589B
Application number: CN202210261674.1A
Authority: CN
Inventors: 汪印; 李智伟; 余迪; 赖登国; 洪辰毅; 刘学蛟; 潘蓓蓓
Original assignee: Institute of Urban Environment of CAS
Current assignee: Institute of Urban Environment of CAS
Priority date: 2022-03-17
Filing date: 2022-03-17
Publication date: 2023-09-29
Anticipated expiration: 2042-03-17
Also published as: CN114671589A

Abstract

The invention discloses a method for synergistic harmless recycling treatment of oil sludge and fly ash, which mainly comprises the following steps: s1, mixing and preprocessing oil sludge and fly ash; s2, drying the pretreated material at a low temperature to generate a gas phase and a solid phase; s3, drying at a low temperature, and sending the solid phase into a pyrolysis device for pyrolysis carbonization, wherein a pyrolysis product comprises pyrolysis residues, pyrolysis gas and pyrolysis oil steam; the invention realizes the synergistic harmless and recycling treatment of two dangerous wastes of the oil sludge and the fly ash, solves the bottleneck problem of high-efficiency removal of toxic substances in the oil sludge and the fly ash, has good environmental protection, realizes the cascade utilization of energy, and can bring considerable economic benefit and environmental benefit.

Description

Method for synergistic harmless recycling treatment of oil sludge and fly ash

Technical Field

The invention relates to the technical field of solid waste treatment, in particular to a method for synergistic harmless recycling treatment of oil sludge and fly ash.

Background

Oily sludge (fatlute) is a high-volatility, high-viscosity organic hazardous waste produced in the petroleum industry production process. The oil sludge is mainly formed by mixing crude oil or finished oil into soil or other mediums, and is organic dangerous solid waste formed by petroleum substances, water, solid particles, heavy metals and the like, and has the characteristics of complex components, high viscosity, high volatility and the like, thus being a main source of petroleum pollution in China. At present, over 600 ten thousand tons of oil sludge are produced annually in China, hundreds of millions of tons are piled up, and the production quantity is increased year by year along with the development of the petroleum industry and the continuous expansion of energy requirements. The oil sludge is difficult to decompose under natural conditions, and volatile organic pollutants, heavy metals, harmful microorganisms and the like contained in the oil sludge seriously threaten natural environment and human health, and are listed in the 'national hazardous waste directory'. The promulgation of new environmental protection laws in 2015 puts higher demands on the disposal of oil sludge and related units. If the treatment of the oily sludge discharged by oil field enterprises does not reach the standard, huge dangerous waste pollution discharge fees need to be paid, and a heavy economic burden is brought to the enterprises. Meanwhile, the treatment of the oil sludge also becomes a great difficulty puzzling the petroleum industry.

At present, the domestic oil-containing sludge recycling technology comprises chemical hot washing, a solvent extraction method, coking, incineration, pyrolysis treatment, modulation separation and profile control technology, and the chemical hot washing and the solvent extraction method belong to physical-chemical conversion; coking, incineration, and pyrolysis processes belong to the thermal conversion. However, the oil sludge has various kinds and various technologies have certain limitations.

On the other hand, in recent years, with the increase of the garbage cleaning and transporting capacity in China, the amount of fly ash generated in the garbage incineration process is also increasing year by year. Fly ash is classified as hazardous waste because it carries high levels of chlorides, heavy metals, and highly toxic dioxins (PCDD/Fs). Therefore, cl, heavy metals and PCDD/Fs in the fly ash are the bottleneck of harmless and recycling utilization of the fly ash, and effective dechlorination and desalination, solidification (extraction) of heavy metals and elimination of PCDD/Fs are the key points of treatment and disposal of the fly ash.

At present, the treatment and disposal of the incineration fly ash of the household garbage can be roughly classified into 2 categories. One type is a traditional treatment method, which comprises separation and purification, solidification/stabilization treatment, high-temperature thermochemical treatment and the like; another category is currently emerging processing methods, comprising: thermochemical (hydrothermal), mechanochemical treatment, and the like. The separation and purification comprises the methods of water washing, acid washing, ion exchange, magnetic separation, electric separation and the like, and the technology is simple and convenient to operate and low in cost; however, after simple separation and purification, the subsequent treatment is still required. In addition, this technique requires consuming a large amount of clean water resources or acidic separation solvents, producing a large amount of wastewater, and imposing a heavy burden on the subsequent treatment. Stabilization is achieved by combining chemical reagents such as: sulfide, calcium salt, ferric salt, phosphate radical and the like are added into the incineration fly ash, and heavy metal precipitate is generated through chemical reaction after complete mixing, so that the aim of stabilization is fulfilled. This technique requires more chemical to be consumed and is costly. The solidification treatment is to mix the incineration fly ash with lime or cement to form a block with low heavy metal leaching toxicity so as to achieve the aim of solidification. However, the volume of the solidified fly ash is generally increased by 1.5-2 times, and the high content of Cl (mass fraction is more than 15%) in the fly ash also easily causes the defects of cracking of the solidified body, promotion of heavy metal leaching and the like. The high-temperature heat treatment comprises high-temperature melting, calcining or vitrification and other technologies, and toxic and harmful PCDD/Fs and the like are thoroughly decomposed at high temperature, so that the harmless treatment is realized, and meanwhile, the heavy metals in the fly ash are stored in crystal lattices of the product to realize stabilization by virtue of high-temperature crystallization and mineralization. The technology has better curing and detoxification effects, but has extremely severe requirements on equipment.

Therefore, the development of an economic, efficient, low-carbon and environment-friendly method for the synergistic harmless and recycling treatment of the decomposed and detoxified oil sludge and the fly ash becomes a hot spot for urgent demands and researches in the petroleum industry and the waste incineration industry.

Disclosure of Invention

Therefore, the invention aims to solve the problems and provide a method for the synergistic harmless recycling treatment of the oil sludge and the fly ash, which realizes the harmless recycling treatment of two major dangerous wastes by adjusting the proportion of the oil sludge to the fly ash and playing the synergistic effect of the oil sludge and the fly ash.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

a method for synergistic harmless recycling treatment of oil sludge and fly ash mainly comprises the following steps:

s1, mixing and preprocessing oil sludge and fly ash;

s2, drying the pretreated material at a low temperature to generate a gas phase and a solid phase;

s3, sending the solid phase after low-temperature drying into a pyrolysis device for pyrolysis carbonization, wherein a pyrolysis product comprises pyrolysis residues, pyrolysis gas and pyrolysis oil steam.

Further improved, during the pretreatment in S1, the mass ratio of the oil sludge to the fly ash is (1-10): 1, and the oil sludge and the fly ash are fully mixed and stirred for 30-60 minutes, so that the uniform mixing of the samples is ensured. In the invention, in order to ensure the synergistic effect of the oil sludge and the fly ash and achieve higher pyrolysis efficiency, the mass ratio of the oil sludge to the fly ash is (1-10): 1, for example, 1:1, 2:1, 2.5: 1. 3.75:1, 4:1, 10:1, etc., but are not limited to the recited values, as are other non-recited values within the range of values.

The proportion of the oil sludge and the fly ash is a key factor influencing the pyrolysis and carbonization of the mixed materials, and the inventor proves that the oil sludge and the fly ash can play better synergistic effect when the mass proportion of the oil sludge and the fly ash is (1-10): 1, thereby achieving higher pyrolysis efficiency. If the mass ratio of the oil sludge to the fly ash is too large, the viscosity of the mixed material is too high, the difficulty of furnace feeding pyrolysis is easily caused to be too large, and crude oil in the oil sludge is difficult to effectively remove; if the mass ratio of the oil sludge to the fly ash is too small, the heat value of the mixed material is too low, a great amount of heat energy needs to be provided in the pyrolysis process, so that the disposal cost is greatly increased, and more carbon emission is increased.

Still further, the fully mixed material is molded, including: extrusion molding or granulation molding. The purpose of the molding is to enlarge the contact area of the material and the pyrolysis gas and improve the pyrolysis efficiency.

Further improved, the gas phase generated in the step S2 and the pyrolysis gas generated in the step S3 are cooled and then enter a combustion device to be used as raw materials, and the high-temperature flue gas generated after incineration is used as an energy source of the pyrolysis device.

Still further, the heat source used for drying in S2 is medium temperature flue gas generated after high temperature flue gas exchanges heat through a pyrolysis device, the temperature of the medium temperature flue gas is about 300-600 ℃, the retention time is 20-60 minutes, the moisture content of a sample after drying is as low as less than 30%, and gas phase generated in the drying process enters a combustion device through a circulating cooling device. The gas phase generated by the drying is a fraction obtained by crude oil in the oil sludge at a certain temperature.

The gas phase generated in the S2 and the pyrolysis gas generated in the S3 enter a combustion device to serve as raw materials, heat generated after incineration sequentially enters the pyrolysis device and a drying device to supply heat, energy cascade utilization is achieved, and the residual low-temperature flue gas after heat supply is discharged after reaching the standard. The treatment mode of the low-temperature flue gas is common means in the prior art, including but not limited to bag dust removal, water washing spraying, alkali liquor spraying, activated carbon adsorption and the like.

The high-temperature flue gas temperature is 800 to 1100 ℃, for example 800 ℃, 850 ℃, 875 ℃, 900 ℃, 910 ℃, 1000 ℃, etc., but not limited to the values listed, and other values not listed in the range are applicable as well. The pyrolysis apparatus temperature is 300 to 950 ℃, for example, 300 ℃, 310 ℃, 350 ℃, 500 ℃, 800 ℃, etc., but not limited to the values listed, and other values not listed in the range are equally applicable.

In a further improvement, in S3, the pyrolysis device adopts an external heating type pyrolysis furnace. Compared with an internal heating type pyrolysis furnace, the external heating type pyrolysis furnace has a more accurate temperature control effect so as to ensure a good pyrolysis effect.

Further improvements, in S3, the pyrolysis temperature is 300-900 ℃, including but not limited to 310 ℃, 350 ℃, 375 ℃, 500 ℃, 800 ℃, and the like; the direction of the material entering the pyrolysis device is opposite to the direction of the high-temperature flue gas entering, so that the contact area is enlarged, and the retention time of the material in the pyrolysis device is 30-60 minutes.

In the step S3, pyrolysis oil steam enters a pyrolysis oil collection device after being cooled.

Further improving, cooling a part of pyrolysis residues obtained by pyrolysis and carbonization in the step S3, and then compounding the part of pyrolysis residues serving as building material auxiliary materials with building material raw materials, wherein the other part of pyrolysis residues directly serving as fuel.

The technical scheme provided by the invention has the following beneficial effects:

1. the invention realizes the synergistic harmless and recycling treatment of two dangerous wastes of the oil sludge and the fly ash, and solves the bottleneck problem of high-efficiency removal of toxic substances in the oil sludge and the fly ash;

2. the fly ash with proper proportion is added in the oil sludge to help to break the adhesion of the oil sludge, and toxic substances such as dioxin and the like in the fly ash are further removed;

3. the alkaline substances in the fly ash play a catalytic role in cracking crude oil in the oil sludge, so that the oil product generated by pyrolysis is light, the oil product can be used as high-quality raw oil, and the pyrolysis product can be used as building material auxiliary materials or fuel with high efficiency;

4. the invention does not pollute the environment in the process of the synergistic harmless treatment of the oil sludge and the fly ash and the recycling treatment, has good environmental protection, realizes the cascade utilization of energy and can bring considerable economic benefit and environmental benefit.

Drawings

FIG. 1 is a schematic illustration of the process flow of the present invention.

Detailed Description

The invention will be described in further detail with reference to the drawings and the detailed description.

Example 1

The oil sludge adopted in the embodiment is from oily sludge of a smooth petrochemical plant, the oil content of the oily sludge is 28.35%, and the fly ash is from bottom ash obtained after incineration of Ningbo household garbage.

As shown in fig. 1, a method for synergistic harmless recycling treatment of oil sludge and fly ash specifically comprises the following steps:

s1, pretreatment: proportioning the oil sludge and the fly ash according to the mass ratio of 2:1 (kg: kg), and then adding the mixture into a mechanical stirrer, and mixing and stirring for 30 minutes to obtain a uniformly mixed sample; the fully mixed materials enter a forming machine for forming;

s2, low-temperature drying: the molded sample enters a drying device through conveying equipment, a heat source used for drying is medium-temperature flue gas generated by a pyrolysis device, the temperature of the flue gas is about 500 ℃, the residence time is 30 minutes, the moisture content of the dried sample is as low as less than 30%, and a gas phase generated in the sample drying process enters a combustion device through a circulating cooling device;

s3, pyrolysis carbonization: and (3) feeding the solid-phase material subjected to low-temperature drying into an external heating type pyrolysis device through a feeding device for pyrolysis carbonization. The external heating type pyrolysis device is connected with the combustion device, a heat source required by pyrolysis carbonization is from high-temperature flue gas generated by combustion of combustible gas in the combustion device, the temperature of the high-temperature flue gas is 900 ℃, and the pyrolysis system can be controlled to be stable at 500 ℃. The direction of the material entering the pyrolysis device is opposite to the direction of the high-temperature flue gas entering, and the retention time of the material in the pyrolysis system is 30 minutes.

The pyrolysis products comprise pyrolysis residues, pyrolysis gas and pyrolysis oil steam, and the mass distribution is as follows: 52%, 22% and 26%. The pyrolysis gas enters a combustion system, and the pyrolysis gas and high-temperature flue gas generated after gas phase burning generated by drying in S2 are used as energy sources of a pyrolysis device; cooling pyrolysis oil steam and then entering a pyrolysis oil collection device; the calorific value of pyrolysis residues obtained by pyrolysis and carbonization is 11543kJ/kg, wherein the dioxin measurement is far lower than the limit value in the standard, and the leaching concentration of heavy metals is far lower than the limit value of the hazardous waste control standard. In addition, as shown in table 6, the pyrolysis residue is not inflammable (Ignitability, I), which further shows that the synergistic harmless recycling treatment effect of the oil sludge and the fly ash is better.

The specific test results are shown in tables 1 and 2:

TABLE 1

The pollution control standard of the landfill site (GB 16889-2008) requires that the content of dioxin (or equivalent toxicity amount) in the solid landfill waste (refer to the incineration residue of medical waste and the incineration fly ash of the household garbage) is lower than 3ng/g, and the content of dioxin in the identification result in the experiment is 4.0X10 ^-4 ng/g, well below the limits in the standard.

TABLE 2

Table 2 shows that the leaching concentration of metal ions (copper, zinc, lead, chromium, arsenic, cadmium, nickel, mercury, beryllium, selenium, barium, hexavalent chromium) in the pyrolysis residue is well below the hazardous waste control standard limit (see GB 5085.3-2007). The fluoride ion leaching concentration is also well below the hazardous waste control standard limit.

TABLE 3 Table 3

In addition, as shown in table 3, the pyrolysis residue is not inflammable (Ignitability, I), which further shows that the synergistic harmless recycling treatment effect of the oil sludge and the fly ash is better.

Example two

s1, pretreatment: proportioning the oil sludge and the fly ash according to the mass ratio of 8:1 (kg: kg), and then adding the mixture into a mechanical stirrer, and mixing and stirring for 30 minutes to obtain a uniformly mixed sample; the fully mixed materials enter a forming machine for forming;

s2, low-temperature drying: the molded sample enters a drying device through a conveying device, a heat source used for drying is medium-temperature flue gas generated by a pyrolysis device, the temperature of the flue gas is about 600 ℃, the residence time is 50 minutes, the moisture content of the dried sample is as low as less than 30%, and a gas phase generated in the sample drying process enters a combustion device through a circulating cooling device;

s3, pyrolysis carbonization: and (3) feeding the solid-phase material subjected to low-temperature drying into an external heating type pyrolysis device through a feeding device for pyrolysis carbonization. The external heating type pyrolysis device is connected with the combustion device, a heat source required by pyrolysis carbonization is from high-temperature flue gas generated by combustion of combustible gas in the combustion device, the temperature of the high-temperature flue gas is 900 ℃, and the pyrolysis system can be controlled to be stable at 700 ℃. The direction of the material entering the pyrolysis device is opposite to the direction of the high-temperature flue gas entering, and the retention time of the material in the pyrolysis system is 30 minutes.

The pyrolysis products comprise pyrolysis residues, pyrolysis gas and pyrolysis oil steam, and the mass distribution is as follows: 24%, 20% and 56%. The pyrolysis gas enters a combustion system, and the pyrolysis gas and high-temperature flue gas generated after gas phase burning generated by drying in S2 are used as energy sources of a pyrolysis device; cooling pyrolysis oil steam and then entering a pyrolysis oil collection device; the calorific value of pyrolysis residues obtained by pyrolysis carbonization is 16728kJ/kg, wherein the dioxin measurement is far lower than the limit value in the standard, and the leaching concentration of heavy metals is far lower than the limit value of the hazardous waste control standard.

The specific test results are shown in tables 4 and 5:

TABLE 4 Table 4

The pollution control standard of the landfill site (GB 16889-2008) requires that the content of dioxin (or equivalent toxicity amount) in the solid landfill waste (refer to the incineration residue of medical waste and the incineration fly ash of the household garbage) is lower than 3ng/g, and the content of dioxin in the identification result in the experiment is 4.0X10 ^-5 ng/g, well below the limits in the standard.

TABLE 5

Table five shows that the leaching concentration of various metal ions in pyrolysis residues at 700 ℃ is far lower than the hazardous waste control standard limit (GB 5085.3-2007), and the leaching concentration of fluorine ions is also far lower than the hazardous waste control standard limit.

TABLE 6

In addition, as shown in table 6, the pyrolysis residue is not inflammable (Ignitability, I), which further shows that the synergistic harmless recycling treatment effect of the oil sludge and the fly ash is better.

The embodiment can be seen that the synergistic treatment of the oil sludge and the fly ash not only can effectively remove toxic substances such as chlorine, dioxin and the like in the fly ash, but also can separate and collect crude oil in the oil sludge, and the products obtained by pyrolysis and carbonization can be used as building auxiliary materials or fuels. The toxic substance content of the treatment result is far lower than the control standard limit, and the treatment result is an effect which cannot be achieved by singly treating the oil sludge or the fly ash in the prior art.

Claims

1. A method for synergistic harmless recycling treatment of oil sludge and fly ash is characterized by comprising the following steps: the method comprises the following steps:

s1, mixing and preprocessing the oil sludge and the fly ash, wherein the mass ratio of the oil sludge to the fly ash is (1-10) 1, fully mixing and stirring for 30-60 minutes, ensuring that the samples are uniformly mixed, and molding the fully mixed materials;

s3, drying at a low temperature, and sending the solid phase into a pyrolysis device for pyrolysis carbonization, wherein a pyrolysis product comprises pyrolysis residues, pyrolysis gas and pyrolysis oil steam;

the gas phase generated in the step S2 and the pyrolysis gas generated in the step S3 are cooled and then enter a combustion device to be used as raw materials, and high-temperature flue gas generated after incineration is used as an energy source of the pyrolysis device.

2. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: the shaping in S1 includes: extrusion molding or granulation molding.

3. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: and S2, the heat source used for drying is medium-temperature flue gas generated after heat exchange of the high-temperature flue gas by the pyrolysis device, the temperature of the medium-temperature flue gas is 300-600 ℃, the residence time is 20-60 minutes, the moisture content of a dried sample is less than 30%, and gas phase generated in the drying process enters the combustion device by the circulating cooling device.

4. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: the high-temperature flue gas temperature is 800-1100 ℃, and the pyrolysis device temperature is 300-950 ℃.

5. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: s3, an external heating type pyrolysis furnace is adopted by the pyrolysis device.

6. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: and S3, the pyrolysis temperature is 300-900 ℃, the direction of the material entering the pyrolysis device is opposite to the direction of the high-temperature flue gas entering, and the retention time of the material in the pyrolysis device is 30-60 minutes.

7. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: and S3, cooling pyrolysis oil steam and then entering a pyrolysis oil collection device.

8. The method for the synergistic harmless recycling treatment of the oil sludge and the fly ash according to claim 1 is characterized in that: and S3, cooling part of pyrolysis residues obtained by pyrolysis and carbonization, and then compounding the part of pyrolysis residues serving as building material auxiliary materials with building material raw materials, wherein the other part of pyrolysis residues directly serves as fuel.