A method for purifying waste containing condensed ring aromatic hydrocarbons

Abstract

The application discloses a purification method containing condensed ring aromatic hydrocarbon waste, comprising the following steps: under an oxygen-containing atmosphere, the condensed ring aromatic hydrocarbon in the waste is contacted with a catalyst and a cracking-oxidation coupling reaction occurs, and the condensed ring aromatic hydrocarbon is converted into a substance that can reach the emission standard. The application takes a relatively simple device and an easily obtained catalyst as a premise, promotes the deep cracking-oxidation of the condensed ring aromatic hydrocarbon in the waste at a proper temperature, improves the decomposition effect of the condensed ring aromatic hydrocarbon, and the removal rate of the condensed ring aromatic hydrocarbon is at least 95.5%, tail gas or liquid obtained through treatment reaches the emission standard, so that the harm of the condensed ring aromatic hydrocarbon to the environment and the ecological system is reduced or eliminated, and the risk of secondary pollution is reduced.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and catalysts, and relates to a method for purifying waste containing polycyclic aromatic hydrocarbons. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are persistent organic wastes released into the environment from the combustion of fossil fuels, industrial production processes, and certain natural processes. PAHs can accumulate in soil, water bodies, and gases, and can have negative impacts on ecosystems, posing a potential hazard. Therefore, decomposing PAHs in waste is an important means of environmental remediation and pollution control.

[0003] The conjugated electron cloud of polycyclic aromatic hydrocarbons (PAHs) keeps the molecules in a stable low-energy state. To change the conjugated structure in the molecule to break the aromatic ring and degrade it, the reaction conditions are quite demanding. It usually needs to be carried out under strong oxidants, high temperature or other high-energy conditions (such as light). The demanding reaction requirements result in a lack of specific purification methods for different phases of waste.

[0004] Chemical oxidation, with its advantages of high efficiency, wide applicability, low cost, and simple operation, has been widely used in the decomposition of polycyclic aromatic hydrocarbons (PAHs). Patent CN111940490A discloses a method for remediating PAH complex waste in soil, utilizing green-synthesized nano-iron to react stepwise with PAHs and Cr(VI), remediating organic pollutants in the soil and reducing the toxicity of some heavy metal ions through a process of oxidation followed by reduction. Using nano-iron can avoid secondary heavy metal pollution in the soil caused by adding catalysts and exhibits a good decomposition rate of PAHs. However, treating PAH-contaminated soil requires a large-scale reaction, and nano-iron's applicability is limited, and its synthesis is cumbersome.

[0005] Patent CN105293683A discloses a method for treating polycyclic aromatic hydrocarbon (PAH) waste in groundwater. This method uses adsorption separation, which is effective. However, it uses a composite material with a core, filling layer, and shell, requiring a wall thickness of over 1 meter, resulting in a large material requirement. Furthermore, the synthesis of this composite material is relatively complicated, and the PAHs remaining after adsorption cannot be degraded, hindering rapid and effective removal. Patent CN105036293A discloses a method for removing organic waste from water using ferrate-enhanced ozone oxidation. This method directly introduces ferrate into water containing organic waste for oxidation, followed by the introduction of ozone to co-oxidize and remove the waste, increasing the waste removal rate by 30%–50%. However, this method is too expensive, and the substances generated after oxidation of organic waste still remain in the water; incompletely oxidized organic matter can even cause more serious water pollution.

[0006] Patent CN106310871A discloses a method for the combined degradation of coal chemical waste gas, including a method for degrading waste gas containing polycyclic aromatic hydrocarbons (PAHs), which involves degrading NO... x When used as an oxidant in waste gas containing polycyclic aromatic hydrocarbons and then heated to its ignition temperature, the waste gas can be converted into other substances in one step. However, the introduced nitrogen element can lead to some uncontrollable side reactions, and NO... x As an oxidant, it is essentially a secondary pollutant of waste gas, and its versatility is not strong. Summary of the Invention

[0007] The purpose of this invention is to address the problem that existing methods for treating polycyclic aromatic hydrocarbons (PAHs) in waste are incomplete, and that adsorption or extraction separation cannot degrade them, resulting in secondary pollution. This invention provides a purification method for waste containing PAHs.

[0008] The objective of this invention is achieved through the following methods.

[0009] A method for purifying waste containing polycyclic aromatic hydrocarbons includes: in an oxygen-containing atmosphere, the polycyclic aromatic hydrocarbons in the waste come into contact with a catalyst and undergo a cracking-oxidation coupling reaction to be converted into substances that can meet emission standards.

[0010] The waste containing polycyclic aromatic hydrocarbons is solid waste, waste liquid, or waste gas.

[0011] The solid waste is one of the following: sludge, soil, or salt contaminated with polycyclic aromatic hydrocarbons (PAHs). The water content of the solid waste is 0–35%. The concentration of PAHs in the solid waste is 5–1000 mg / kg.

[0012] The waste liquid is at least one of groundwater, river water, or municipal sewage contaminated with polycyclic aromatic hydrocarbons (PAHs). The concentration of PAHs in the waste liquid is 0.1–2.1 mg / L.

[0013] The exhaust gas is at least one of the following: automobile exhaust, coking industry exhaust, and waste incineration flue gas, all of which are polluted by polycyclic aromatic hydrocarbons (PAHs). The concentration of PAHs in the exhaust gas is 5–188 μg / m³. 3 .

[0014] The polycyclic aromatic hydrocarbons mentioned are naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, etc. One or more of benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indo[1,2,3-cd]pyrene, dibenzo[a,h]anthene, benzo[perylene], 1-methylnaphthalene, and 2-methylnaphthalene.

[0015] The oxygen-containing atmosphere is achieved by introducing either air or oxygen into the reaction apparatus as a carrier gas; the mass hourly space velocity (HSV) of the carrier gas is 0.4–15 h⁻¹. -1When the waste is solid waste, the mass hourly space velocity of the carrier gas can be further selected from 8 to 10 h⁻¹. -1 When the waste is waste liquid, the mass hourly space velocity of the carrier gas can be further selected from 8 to 10 h⁻¹. -1 When the waste is exhaust gas, the mass hourly space velocity of the carrier gas can be further selected from 6 to 8 h⁻¹. -1 .

[0016] Select a suitable reactor and catalyst based on the phase state of the waste and the type of polycyclic aromatic hydrocarbons:

[0017] When the waste is solid waste, since the solid waste is in solid-solid contact with the catalyst, an external driving force is required to drive the solid waste into contact with the catalyst surface, so a rotary reactor is selected. The process includes: loading the solid waste and catalyst into the rotary reactor, which is in a continuous rotating state. Under an oxygen-containing atmosphere and the action of the catalyst, the polycyclic aromatic hydrocarbons in the solid waste undergo a cracking-oxidation coupling reaction. The temperature of the cracking-oxidation coupling reaction is 200–500℃, preferably 350–400℃, and the pressure of the cracking-oxidation coupling reaction is -0.05–0.2 MPa. To prevent gas leakage from the rotary reactor during the treatment process, the pressure of the cracking-oxidation coupling reaction is preferably negative, specifically -0.01 MPa.

[0018] When the waste is solid waste, the catalyst is at least one of CaO, MgO, Fe2O3, Al2O3, calamine, fly ash, and amorphous silica-alumina; the particle size of the catalyst is 400 nm to 100 μm. By controlling the minimum particle size of the catalyst, excessively fine catalyst particles are prevented from being carried out of the reactor along with the tail gas; at the same time, the maximum particle size is limited to ensure that the catalyst can fully contact the waste.

[0019] In the rotary reactor, the mass ratio of catalyst to solid waste is 0.01:1 to 2:1, preferably 0.1:1 to 0.15:1.

[0020] The rotational speed of the rotary reactor is 1 to 15 r / min, preferably 5 to 12 r / min, and more preferably 10 to 12 r / min.

[0021] After the cracking-oxidation coupling reaction, the concentration of polycyclic aromatic hydrocarbons in the solid waste reaches below 5 mg / kg.

[0022] When the waste is liquid waste, since the treatment of liquid waste involves three phases (gas, liquid, and solid), selecting a fluidized bed reactor allows the liquid waste and catalyst to be in a carrier state, forming a state of full contact and friction between the three phases of "liquid waste, carrier gas, and catalyst" accompanied by the carrier gas. This includes: simultaneously and continuously introducing the liquid waste and oxygen-containing carrier gas from the bottom into the fluidized bed reactor; under the oxygen-containing atmosphere and the action of the catalyst, the polycyclic aromatic hydrocarbons in the liquid waste undergo a cracking-oxidation coupling reaction to form substances that meet emission standards; the temperature of the cracking-oxidation coupling reaction is 200–400℃, preferably 300–350℃; the pressure of the cracking-oxidation coupling reaction is -0.05–0.2 MPa, preferably 0.1 MPa.

[0023] As a further preferred option, the gas obtained from the cracking-oxidation coupled reaction is discharged from the top of the fluidized bed reactor and condensed to obtain condensate and non-condensable gas. The concentration of polycyclic aromatic hydrocarbons in the condensate reaches below 0.1 mg / L, and the non-condensable gas meets the emission standards.

[0024] When the waste is waste liquid, the catalyst is a supported catalyst. The active component of the catalyst is one or two of CaO, MgO, Fe2O3, Al2O3, CeO2, Cr2O3, and CuO. The catalyst support is one of SiO2, TiO2, ZSM-35, USY, MCM-22, and ZSM-5. The loading of the active component is 5% to 15%. The supported catalyst is prepared by a conventional impregnation method.

[0025] In the fluidized bed reactor, the liquid hourly space velocity (LHSV) of the waste liquid is 0.8–2.5 h⁻¹. -1 Preferably, it is 1.8 to 2.0 hours. -1 .

[0026] When the waste is exhaust gas, since gas-solid contact must be considered during exhaust gas treatment, the exhaust gas and carrier gas are in a flowing state, allowing the exhaust gas to flow through the catalyst. A fixed-bed reactor is the most economical choice. The process includes: loading a tableted catalyst into a fixed-bed reactor, preheating the catalyst, and then simultaneously and continuously introducing the preheated exhaust gas and preheated oxygen-containing carrier gas from the top into the fixed-bed reactor. The exhaust gas contacts the catalyst, causing a cracking-oxidation coupling reaction of polycyclic aromatic hydrocarbons, resulting in tail gas that meets emission standards. The temperature of the cracking-oxidation coupling reaction is 200–400°C, preferably 250–300°C; the pressure of the cracking-oxidation coupling reaction is -0.05–0.2 MPa, preferably 0.02–0.1 MPa.

[0027] Preferably, the catalyst, exhaust gas, and carrier gas are all preheated to the reaction temperature.

[0028] When the waste is waste gas, the catalyst is a catalyst obtained by pressing at least one of CaO, MgO, Fe2O3, Al2O3, CeO2, Cr2O3, CuO, ZSM-5, calamine, fly ash, and amorphous silica-alumina into tablets.

[0029] In the fixed-bed reactor, the gas hourly space velocity of the waste gas is 6000–20000 h⁻¹. -1 .

[0030] As a further preferred option, the exhaust gas is discharged from the bottom of the fixed-bed reactor, and the concentration of polycyclic aromatic hydrocarbons in the exhaust gas reaches 5 μg / m³. 3 the following.

[0031] The beneficial effects of this invention are reflected in:

[0032] This invention, based on relatively simple equipment and readily available catalysts, promotes the deep cracking-oxidation of polycyclic aromatic hydrocarbons (PAHs) in waste at appropriate temperatures, thereby improving the decomposition efficiency of PAHs. The removal rate of PAHs reaches at least 95.5%, and the treated tail gas or liquid meets emission standards, thus reducing or eliminating the harm of PAHs to the environment and ecosystem, reducing the risk of secondary pollution, and contributing to the improvement of the ecological environment. It has important application value for the treatment and ecological restoration of PAHs.

[0033] This invention significantly improves the processing efficiency of polycyclic aromatic hydrocarbons and reduces equipment and energy costs. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below through implementation examples.

[0035] Example 1

[0036] The waste to be treated was naphthalene-contaminated soil with a concentration of 1000 mg / kg and a moisture content of 19%. The catalyst was MgO powder with a particle size of 20 μm.

[0037] The soil contaminated with naphthalene was treated using a solid-phase catalytic purification method, with the following steps: First, the catalyst and the naphthalene-contaminated soil were physically mixed at a mass ratio of 0.1:1, and then loaded into a rotary reactor; oxygen was selected as the carrier gas, and the mass hourly space velocity (HHSV) of the carrier gas was 8 h⁻¹. -1 The reaction tube of the rotary reactor rotates at 10 r / min. While rotating, the temperature of the reaction zone is maintained at 400℃ and the pressure at -0.01 MPa to allow naphthalene to undergo a cracking-oxidation coupled reaction. The processing time is 20 min.

[0038] The concentration of naphthalene in the soil after cracking-oxidation coupling treatment was 4.2 mg / kg, with a naphthalene removal rate of 99.6%; benzaldehyde was detected in the exhaust gas, with a concentration of 0.03 mg / m³. 3 .

[0039] Example 2

[0040] The waste to be treated was sludge contaminated with polycyclic aromatic hydrocarbons (PAHs), namely benzo[a]pyrene, fluorene, phenanthrene, and anthracene, with a concentration of 800 mg / kg and a moisture content of 34%. The catalyst was Fe2O3 powder with a particle size of 50 μm.

[0041] Soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was treated using a solid-phase catalytic purification method. The steps are as follows: First, the catalyst and the contaminated soil were physically mixed at a mass ratio of 0.15:1, and then loaded into a rotary reactor. Air was used as the carrier gas, and the mass hourly space velocity (MHV) of the carrier gas was 10 h⁻¹. -1 The reaction tube of the rotary reactor rotates at 12 r / min. While rotating, the temperature of the reaction zone is maintained at 350℃ and the pressure at -0.01 MPa, so that benzo[a]pyrene, fluorene, phenanthrene and anthracene undergo cracking-oxidation coupling reaction. The processing time is 25 min.

[0042] The concentration of polycyclic aromatic hydrocarbons (PAHs) in the soil after cracking-oxidation coupling treatment was 4.9 mg / kg, with a PAH removal rate of 99.4%. Formic acid was detected in the exhaust gas, with a concentration of 5.9 mg / m³. 3 .

[0043] Example 3

[0044] The waste to be treated is groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs), of which the PAH is indo[1,2,3-cd]pyrene, with a pollution concentration of 1.8 mg / L.

[0045] The catalyst is a supported catalyst with Fe2O3 as the active component and SiO2 as the support, and the loading of the active component is 15%. The supported catalyst is prepared by the following method: ferric nitrate is dissolved in water to obtain a ferric nitrate solution, SiO2 is added to the ferric nitrate solution, the mixture is stirred at room temperature for 12 h, filtered, dried in an oven, and the dried sample is placed in a tube furnace and calcined at 400 °C in air atmosphere.

[0046] Groundwater contaminated with inde[1,2,3-cd]pyrene was treated using a continuous feed method, with the following steps: First, the catalyst was placed in a fluidized bed reactor; air was used as the carrier gas, and both the carrier gas and the groundwater contaminated with polycyclic aromatic hydrocarbons were continuously fed into the fluidized bed reactor from the bottom simultaneously, with a mass hourly space velocity (MSV) of 8 h⁻¹ for the carrier gas. -1 The liquid hourly space velocity (LHSV) of groundwater contaminated with polycyclic aromatic hydrocarbons (PAHs) is 1.8 h⁻¹. -1The internal pressure of the fluidized bed reactor is 0.1 MPa, and the temperature is 350℃. The waste liquid and catalyst are in a carrier state, and indo[1,2,3-cd]pyrene undergoes a cracking-oxidation coupled reaction. The tail gas is discharged from the top of the fluidized bed reactor and condensed to obtain condensate, which is the groundwater after cracking-oxidation treatment. The concentration of polycyclic aromatic hydrocarbons (PAHs) is 0.07 mg / L, and the PAH removal rate is 96.1%. The concentration of PAHs in the non-condensable gas is detected, and the PAH concentration is lower than the value specified in the "Air Pollutant Emission Standard".

[0047] Example 4

[0048] The waste to be treated is river water contaminated with polycyclic aromatic hydrocarbons (PAHs), namely fluoranthene and pyrene, with a pollution concentration of 2.1 mg / L.

[0049] The catalyst is a supported catalyst with Al2O3 as the active component and ZSM-5 as the support, with a loading of 10% for the active component. The supported catalyst is prepared by the following method: aluminum nitrate is dissolved in water to obtain an aluminum nitrate solution, ZSM-5 molecular sieve is added to the aluminum nitrate solution, stirred at room temperature for 12 h, filtered, dried in an oven, and the dried sample is placed in a tube furnace and calcined at 400 °C in air atmosphere.

[0050] The treatment of river water contaminated with polycyclic aromatic hydrocarbons (PAHs) using a continuous feed method involves the following steps: The catalyst is placed in a solid-fluidized bed reactor; oxygen is used as the carrier gas, and both the carrier gas and the PAH-contaminated river water are continuously fed into the fluidized bed reactor from the bottom simultaneously, with a carrier gas mass hourly space velocity (MHV) of 8 h⁻¹. -1 The liquid hourly space velocity (LHSV) of the river water contaminated with polycyclic aromatic hydrocarbons was 2.0 h⁻¹. -1 The waste liquid and catalyst are in a carrier state. The internal pressure of the fluidized bed reactor is 0.1 MPa and the temperature is 300℃. Fluoranthene and pyrene undergo cracking-oxidation coupling reaction. The tail gas is discharged from the top of the fluidized bed reactor and condensed to obtain condensate, which is the river water treated by cracking-oxidation. The concentration of polycyclic aromatic hydrocarbons is 0.05 mg / L, and the removal rate of polycyclic aromatic hydrocarbons is 97.6%. The concentration of polycyclic aromatic hydrocarbons in the non-condensable gas is detected, and the concentration of polycyclic aromatic hydrocarbons is lower than the value specified in the "Emission Standard of Air Pollutants".

[0051] Example 5

[0052] The waste to be treated is vehicle exhaust, containing benzo[a]pyrene, a polycyclic aromatic hydrocarbon, at a concentration of 155 μg / m³. 3 The catalyst is Fe2O3 in tablet form.

[0053] The treatment of automotive exhaust gas using a continuous feed method involves the following steps: A tableted catalyst is loaded into a fixed-bed reactor, and the catalyst is preheated to 300°C; oxygen is selected as the carrier gas, with a mass hourly space velocity (HHSV) of 6 h⁻¹.-1 The space velocity of automobile exhaust is 10,000 h⁻¹. -1 Both oxygen and automobile exhaust are preheated to 300°C and continuously fed into a fixed-bed reactor from the top. The internal pressure of the fixed-bed reactor is 0.02 MPa and the temperature is 300°C. Benzo[a]pyrene undergoes a cracking-oxidation coupling reaction and exhaust gas is discharged from the top of the fixed-bed reactor.

[0054] The concentration of polycyclic aromatic hydrocarbons in the exhaust gas was 2 μg / m³. 3 The concentration of polycyclic aromatic hydrocarbons (PAHs) was lower than the value specified in the "Emission Standard for Air Pollutants", and the removal rate of PAHs was 98.7%.

[0055] Example 6

[0056] The waste to be treated is exhaust gas from a coking plant, containing polycyclic aromatic hydrocarbons (PAHs) of naphthalene and anthracene, with a pollution concentration of 180 μg / m³. 3 The catalyst is CaO that has been compressed into tablets.

[0057] The waste gas from the coal gas plant is treated using a continuous feed method, with the following steps: Catalyst tablets are loaded into a fixed-bed reactor and heated to 300°C; oxygen is selected as the carrier gas, with a mass hourly space velocity (HHSV) of 8 h⁻¹. -1 The gas hourly space velocity of the exhaust gas from the gas plant is 15000 h⁻¹. -1 Both oxygen and coal gas plant exhaust gas are preheated to 300℃ and simultaneously fed into a fixed-bed reactor from the top. The internal pressure of the fixed-bed reactor is 0.02MPa and the temperature is 300℃. Naphthalene and anthracene undergo a cracking-oxidation coupling reaction, and the exhaust gas is discharged from the top of the fixed-bed reactor.

[0058] The concentration of polycyclic aromatic hydrocarbons in the exhaust gas was 5 μg / m³. 3 The concentration of polycyclic aromatic hydrocarbons (PAHs) was lower than the value specified in the "Emission Standard for Air Pollutants", and the removal rate of PAHs was 97.2%.

[0059] Example 7

[0060] The waste to be treated was naphthalene-contaminated soil with a concentration of 1000 mg / kg and a moisture content of 19%. The catalyst was calamine powder with a particle size of 100 μm.

[0061] The soil contaminated with naphthalene was treated using a solid-phase catalytic purification method, with the following steps: First, the catalyst and the naphthalene-contaminated soil were physically mixed at a mass ratio of 0.1:1, and then loaded into a rotary reactor; oxygen was selected as the carrier gas, and the mass hourly space velocity (HHSV) of the carrier gas was 8 h⁻¹. -1The reaction tube of the rotary reactor rotates at 10 r / min. While rotating, the temperature of the reaction zone is maintained at 400℃ and the pressure at -0.01 MPa to enable naphthalene to undergo a cracking-oxidation coupled reaction.

[0062] The concentration of naphthalene in the soil after cracking-oxidation coupling treatment was 4.8 mg / kg, with a naphthalene removal rate of 99.5%; benzaldehyde was detected in the exhaust gas, with a concentration of 0.05 mg / m³. 3 .

[0063] Example 8

[0064] The waste to be treated is river water contaminated with polycyclic aromatic hydrocarbons (PAHs), namely fluoranthene and pyrene, with a pollution concentration of 2.1 mg / L.

[0065] The catalyst is a supported catalyst with CuO as the active component and TiO2 as the support, and the loading of the active component is 10%. The supported catalyst is prepared by the following method: copper nitrate is dissolved in water to obtain a copper nitrate solution, TiO2 is added to the copper nitrate solution, stirred for 12 hours, filtered, dried in an oven, and the dried sample is placed in a tube furnace and calcined at 350°C in an air atmosphere.

[0066] River water contaminated with fluoranthene and pyrene was treated using a continuous feed method, with the following steps: The catalyst was placed in a fluidized bed reactor; oxygen was used as the carrier gas, and both the carrier gas and the contaminated river water were continuously fed into the fluidized bed reactor from the bottom simultaneously, with a carrier gas mass hourly space velocity (HHSV) of 8 h⁻¹. -1 The liquid hourly space velocity (LHSV) of the river water contaminated with fluorescein and pyrene was 2.0 h⁻¹. -1 The waste liquid and catalyst are in a carrier state. The internal pressure of the fluidized bed reactor is 0.1 MPa and the temperature is 300℃. Fluoranthene and pyrene undergo a cracking-oxidation coupled reaction. The tail gas is discharged from the top of the fluidized bed reactor and condensed to obtain condensate, which is the river water treated by cracking-oxidation. The concentration of polycyclic aromatic hydrocarbons is 0.04 mg / L, and the removal rate of polycyclic aromatic hydrocarbons is 98.1%. The concentration of polycyclic aromatic hydrocarbons in the non-condensable gas is detected, and the concentration of polycyclic aromatic hydrocarbons is lower than the value specified in the "Emission Standard of Air Pollutants".

[0067] Example 9

[0068] The waste to be treated is river water contaminated with polycyclic aromatic hydrocarbons (PAHs), namely fluoranthene and pyrene, with a pollution concentration of 2.1 mg / L.

[0069] The catalyst is a supported catalyst with Cr2O3 as the active component and MCM-22 as the support, and the loading of the active component is 10%. The supported catalyst is prepared by the following method: dissolving chromium nitrate in water to obtain a chromium nitrate solution, adding MCM-22 to the chromium nitrate solution, stirring for 12 h, filtering, drying in an oven, and calcining the dried sample in a tube furnace at 400 °C in an air atmosphere.

[0070] River water contaminated with fluoranthene and pyrene was treated using a continuous feed method, with the following steps: The catalyst was placed in a fluidized bed reactor; oxygen was used as the carrier gas, and both the carrier gas and the contaminated river water were continuously fed into the fluidized bed reactor from the bottom simultaneously, with a carrier gas mass hourly space velocity (HHSV) of 8 h⁻¹. -1 The liquid hourly space velocity (LHSV) of the river water contaminated with fluorescein and pyrene was 2.0 h⁻¹. -1 The internal pressure of the fluidized bed reactor is 0.1 MPa, and the temperature is 300℃. Fluoranthracene and pyrene undergo a cracking-oxidation coupled reaction. The tail gas is discharged from the top of the fluidized bed reactor and condensed to obtain condensate, which is the river water treated by cracking-oxidation. The concentration of polycyclic aromatic hydrocarbons (PAHs) is 0.09 mg / L, and the PAH removal rate is 95.7%. The concentration of PAHs in the non-condensable gas is detected, and the PAH concentration is lower than the value specified in the "Emission Standard of Air Pollutants".

[0071] Example 10

[0072] The waste to be treated is vehicle exhaust, containing benzo[a]pyrene, a polycyclic aromatic hydrocarbon, at a concentration of 155 μg / m³. 3 The catalyst is CuO in tablet form.

[0073] The treatment of vehicle exhaust gas using a continuous feed method involves the following steps: A tableted catalyst is loaded into a fixed-bed reactor and preheated to 250°C; oxygen is selected as the carrier gas, and both the oxygen and vehicle exhaust gas are preheated to 250°C. Both oxygen and vehicle exhaust gas are then continuously introduced into the fixed-bed reactor simultaneously from the top, with a mass hourly space velocity (HSV) of 6 h⁻¹. -1 The space velocity of automobile exhaust is 10,000 h⁻¹. -1 The internal pressure of the fixed-bed reactor is 0.1 MPa and the temperature is 250 °C. Benzo[a]pyrene undergoes a cracking-oxidation coupling reaction and exhausts the tail gas from the top of the fixed-bed reactor.

[0074] The concentration of polycyclic aromatic hydrocarbons in the exhaust gas was 1.8 μg / m³. 3 The concentration of polycyclic aromatic hydrocarbons (PAHs) was lower than the value specified in the "Emission Standard for Air Pollutants", and the removal rate of PAHs was 98.8%.

[0075] Example 11

[0076] The waste to be treated is vehicle exhaust, containing benzo[a]pyrene, a polycyclic aromatic hydrocarbon, at a concentration of 155 μg / m³. 3 The catalyst is CeO2 in tablet form.

[0077] The treatment of vehicle exhaust gas using a continuous feed method involves the following steps: A tableted catalyst is loaded into a fixed-bed reactor and preheated to 250°C; oxygen is selected as the carrier gas, and both the oxygen and vehicle exhaust gas are preheated to 250°C. Both oxygen and vehicle exhaust gas are simultaneously and continuously introduced into the fixed-bed reactor from the top, with a carrier gas mass hourly space velocity (MHV) of 8 h⁻¹. -1 The gas space velocity of automobile exhaust is 12,000 h⁻¹. -1 The internal pressure of the fixed-bed reactor is 0.1 MPa and the temperature is 250 °C. Benzo[a]pyrene undergoes a cracking-oxidation coupling reaction and exhaust gas is discharged from the top of the fixed-bed reactor.

[0078] The concentration of polycyclic aromatic hydrocarbons in the exhaust gas was 1.5 μg / m³. 3 The concentration of polycyclic aromatic hydrocarbons (PAHs) was lower than the value specified in the "Emission Standard for Air Pollutants", and the removal rate of PAHs was 99.0%.

[0079] Example 12

[0080] The waste to be treated is exhaust gas from a coking plant, containing polycyclic aromatic hydrocarbons (PAHs) of naphthalene and anthracene, with a pollution concentration of 180 μg / m³. 3 The catalyst is compressed fly ash, the main active components of which are Al2O3 (15.6% by mass), Fe2O3 (12.3% by mass) and CaO (5.2% by mass), with the remainder being SiO2.

[0081] The waste gas from the coal gas plant is treated using a continuous feeding method, with the following steps: A tableted catalyst is loaded into a fixed-bed reactor and heated to 300°C; oxygen is selected as the carrier gas, and both the oxygen and the waste gas from the coal gas plant are preheated to 300°C. Both oxygen and the waste gas are simultaneously and continuously introduced into the fixed-bed reactor from the top, with a mass hourly space velocity (HSV) of 8 h⁻¹. -1 The gas hourly space velocity of the exhaust gas from the gas plant is 20,000 h⁻¹. -1 The internal pressure of the fixed-bed reactor is 0.1 MPa and the temperature is 300℃. Naphthalene and anthracene undergo cracking-oxidation coupling reaction, and the tail gas is discharged from the top of the fixed-bed reactor.

[0082] The concentration of polycyclic aromatic hydrocarbons in the exhaust gas was 3.8 μg / m³. 3 The concentration of polycyclic aromatic hydrocarbons (PAHs) was lower than the value specified in the "Emission Standard for Air Pollutants", and the removal rate of PAHs was 97.9%.

Claims

1. A method for purifying waste containing polycyclic aromatic hydrocarbons, characterized in that: include: The waste containing polycyclic aromatic hydrocarbons is solid waste, waste liquid or waste gas. Under an oxygen-containing atmosphere, the polycyclic aromatic hydrocarbons in the waste come into contact with the catalyst and undergo a cracking-oxidation coupling reaction, transforming them into substances that can be discharged in compliance with standards. When the waste is solid waste, the process includes: loading solid waste and catalyst into a rotary reactor, the rotary reactor being continuously rotated, and under the action of an oxygen-containing atmosphere and catalyst, the polycyclic aromatic hydrocarbons in the solid waste undergo a cracking-oxidation coupling reaction. The catalyst is at least one of CaO, MgO, Fe2O3, Al2O3, calamine, fly ash, and amorphous silica-alumina; the particle size of the catalyst is 400 nm to 100 μm. The temperature of the cracking-oxidation coupling reaction is 350–400 °C, and the pressure of the cracking-oxidation coupling reaction is -0.01 MPa. When the waste is waste liquid, the process includes: continuously introducing the waste liquid and oxygen-containing carrier gas from the bottom into a fluidized bed reactor at the same time, and under the action of an oxygen-containing atmosphere and a catalyst, the polycyclic aromatic hydrocarbons in the waste liquid undergo a cracking-oxidation coupling reaction. The active component of the catalyst is one or two of CaO, MgO, Fe2O3, Al2O3, CeO2, Cr2O3, and CuO; the catalyst support is one of SiO2, TiO2, ZSM-35, USY, MCM-22, and ZSM-5; and the loading of the active component is 5-15%. The temperature of the cracking-oxidation coupling reaction is 200–400°C, and the pressure of the cracking-oxidation coupling reaction is -0.05–0.2 MPa. When the waste is waste gas, the process includes: loading a tableted catalyst into a fixed-bed reactor, preheating the catalyst, and then continuously introducing the preheated waste gas and the preheated oxygen-containing carrier gas into the fixed-bed reactor from the top at the same time, so that the waste gas contacts the catalyst and causes the polycyclic aromatic hydrocarbons to undergo a cracking-oxidation coupling reaction. The catalyst is a catalyst obtained by pressing at least one of CaO, MgO, Fe2O3, Al2O3, CeO2, Cr2O3, CuO, ZSM-5, calamine, fly ash, and amorphous silica-alumina into tablets. The temperature of the cracking-oxidation coupling reaction is 200–400 °C, and the pressure of the cracking-oxidation coupling reaction is -0.05–0.2 MPa.

2. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The solid waste is one of sludge, soil, or salt contaminated with polycyclic aromatic hydrocarbons (PAHs), and the water content of the solid waste is 0-35%; the concentration of PAHs in the solid waste is 5-1000 mg / kg. The waste liquid is at least one of groundwater, river water, and urban sewage contaminated with polycyclic aromatic hydrocarbons; the concentration of polycyclic aromatic hydrocarbons in the waste liquid is 0.1–2.1 mg / L. The exhaust gas is at least one of the following: automobile exhaust, coking industry exhaust, and waste incineration flue gas polluted by polycyclic aromatic hydrocarbons (PAHs); the concentration of PAHs in the exhaust gas is 5–188 μg / m³. 3 .

3. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The polycyclic aromatic hydrocarbons mentioned are one or more of the following: naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indo[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, benzo[perylene], 1-methylnaphthalene, and 2-methylnaphthalene.

4. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The oxygen-containing atmosphere is achieved by introducing either air or oxygen into the reaction apparatus as a carrier gas; the mass hourly space velocity (HSV) of the carrier gas is 0.4–15 h⁻¹. -1 .

5. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The mass ratio of the catalyst to solid waste is 0.01:1 to 2:1; the rotation speed of the rotary reactor is 1 to 15 r / min.

6. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 5, characterized in that: The mass ratio of catalyst to solid waste is 0.1:1 to 0.15:1; the rotation speed of the rotary reactor is 5 to 12 r / min.

7. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 6, characterized in that: The rotational speed of the rotary reactor is 10-12 r / min.

8. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The liquid hourly space velocity (LISH) of the waste liquid is 0.8–2.5 h⁻¹. -1 .

9. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 8, characterized in that: The liquid hourly space velocity (LHSV) of the waste liquid is 1.8–2.0 h⁻¹. -1 .

10. The purification method for waste containing polycyclic aromatic hydrocarbons according to claim 1, characterized in that: The gas hourly space velocity of the exhaust gas is 6000–20000 h⁻¹. -1 ; The temperature of the cracking-oxidation coupling reaction is 250–300°C, and the pressure of the cracking-oxidation coupling reaction is 0.02–0.1 MPa.