Tar residue treatment method

Abstract

The invention discloses a tar residue treatment method, and belongs to the technical field of coking waste treatment, and the tar residue treatment method comprises the following steps: S1, pretreating and tempering tar residues to disperse large-particle blocks and preliminarily dissociate wrapped organic matters; s2, gradient solvent extraction and separation: adopting a two-stage extraction process, namely recycling light oil products and phenols through first-stage extraction and recycling medium tar and asphaltene through second-stage extraction; and S3, low-temperature catalytic pyrolysis of the raffinate residues: carrying out catalytic modification, low-temperature pyrolysis and heavy metal solidification on the raffinate residues subjected to two-stage extraction. S4, resource oriented utilization of the product; comprising the following steps: condensing and separating pyrolysis oil gas, and recovering pyrolysis oil; and after the pyrolysis carbon residue / ash is extracted and pyrolyzed, the total amount of polycyclic aromatic hydrocarbon in the final solid residue reaches the harmless standard. The tar residue can be efficiently separated and recycled at a high value, hazardous waste is completely converted into marketable products and safe building raw materials, and the win-win situation of environment and economic benefits is achieved.

Description

Technical Field

[0001] This invention belongs to the field of coking waste treatment technology, and particularly relates to a method for treating tar residue. Background Technology

[0002] Coal tar residue is a complex residue produced during coal tar processing. Its main components are polycyclic aromatic hydrocarbons (PAHs), heavy metals, and incompletely decomposed organic impurities. It exhibits significant viscosity and physicochemical stability, leading to numerous difficulties in its treatment and resource utilization. The current mainstream treatment method is coal blending and reprocessing, where coal tar residue is mixed into coking coal in a certain proportion and then reprocessed in a coke oven. However, this method has significant limitations: the blending ratio is low, resulting in a large amount of coal tar residue not being utilized; harmful components in the coal tar residue affect the microstructure and mechanical strength of coke, leading to a decline in coke quality; simultaneously, toxic substances such as PAHs are not completely degraded during the reprocessing process and may still enter the environment through volatilization or leaching; furthermore, if used only as a cheap fuel, its calorific value utilization efficiency is low, its economic value is limited, and it cannot achieve high-value-added resource conversion. While direct incineration can reduce volume, it easily produces toxic gases such as dioxins and sulfur oxides, causing air pollution. Direct landfilling, on the other hand, poses risks of heavy metal seepage into groundwater and long-term soil contamination, wasting potential energy value and creating environmental risks. Therefore, developing a tar residue treatment technology that can completely degrade or transform its toxic components, avoid secondary pollution, and has high economic value is of great significance for promoting the green and sustainable development of the coal chemical industry. Summary of the Invention

[0003] This invention provides a method for treating tar residue, which can efficiently separate and recycle tar residue with high value, completely transforming hazardous waste into marketable products and safe building material raw materials, achieving a win-win situation for both environmental and economic benefits.

[0004] To achieve the above-mentioned technical objectives, the present invention aims to provide a method for treating tar residue, comprising:

[0005] S1. Pre-treat and condition the tar residue to disperse large particles and initially dissociate the encapsulated organic matter.

[0006] S2, Step-by-step solvent extraction and separation: A two-stage extraction process is adopted, namely, the first stage extraction recovers light oil and phenols, and the second stage extraction recovers medium tar and asphaltenes.

[0007] S3. Low-temperature catalytic pyrolysis of raffinate residue: The raffinate residue after two-stage extraction is subjected to catalytic modification, low-temperature pyrolysis and heavy metal solidification.

[0008] S4. Targeted utilization of the product's resources; including:

[0009] The pyrolysis oil and gas are condensed and separated to recover the pyrolysis oil.

[0010] After extraction and pyrolysis of the pyrolysis residue / ash, the total amount of polycyclic aromatic hydrocarbons in the final solid residue meets the harmlessness standard.

[0011] Furthermore, S1 includes: mixing tar residue with light circulating oil or bio-based solvent in a certain proportion, and performing ultrasonic-assisted or microwave-assisted stirring to reduce its viscosity, disperse large particle agglomerates, and initially dissociate the encapsulated organic matter.

[0012] Furthermore, the mass ratio of solvent to tar residue is 0.5:1 to 0.8:1.

[0013] Furthermore, in S2, the primary extraction includes: feeding the conditioned mixture into the first extraction tower and performing countercurrent extraction using the low-boiling-point, recyclable green solvent ethyl acetate or dimethyl ether at a temperature of 40°C to 60°C.

[0014] Furthermore, the separated extract phase I is rich in low molecular weight aromatics and phenols. After solvent recovery by vacuum distillation, light fuel oil or chemical raw materials are obtained.

[0015] Furthermore, in S2, the secondary extraction includes: feeding the residue after the primary extraction into a second extraction tower and extracting it using the solvent N-methylpyrrolidone at a temperature of 80–120°C.

[0016] Furthermore, the separated extract phase II contains high molecular weight tar and asphaltenes, which, after processing, can be used as heavy fuel oil, carbon black raw material, or asphalt modifier.

[0017] Furthermore, the catalytic modification includes: using a supported metal catalyst, loading Fe or Ni onto fly ash or waste molecular sieve, uniformly mixing the residue with the supported metal catalyst, utilizing the catalyst's ability to reduce the pyrolysis activation energy, and guiding the organic matter towards a specific product.

[0018] Furthermore, the low-temperature pyrolysis includes: pyrolysis at 400℃~550℃ in an oxygen-free or oxygen-deficient environment; macromolecular polycyclic aromatic hydrocarbons are selectively cracked into hydrogen-rich fuel gas and carbon-rich solid residue; the hydrogen-rich fuel gas, whose main components are H2, CH4, and CO, is used as fuel to recover thermal energy.

[0019] Furthermore, the heavy metal solidification includes: during the pyrolysis process, the inorganic mineral components in the catalyst and materials solidify the heavy metals to prevent them from volatilizing and migrating.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] This invention couples two core units, green solvent extraction and low-temperature catalytic pyrolysis, to construct a graded treatment process that first extracts high-value components and then degrades residual hazardous substances, and enables targeted regulation and resource utilization of the products throughout the process.

[0022] This invention achieves the goal of precise and high-value recycling of hazardous waste. Unlike traditional crude treatment methods such as direct incineration or simple recycling, this invention uses multi-stage gradient extraction technology to separate and purify components with different boiling ranges and economic values ​​in tar residue, significantly improving the added value and economic benefits of the end product.

[0023] This invention ensures the complete and harmless treatment of waste. Building upon the removal of most organic matter in the green solvent extraction stage, the subsequent low-temperature catalytic pyrolysis unit further degrades residual recalcitrant polycyclic aromatic hydrocarbons, combining high-temperature mineralization and physical solidification to produce a final solid product with extremely low environmental risk, meeting safe disposal requirements.

[0024] The entire process of this invention is green and low-carbon, with minimal environmental impact. Compared to direct incineration, low-temperature catalytic pyrolysis significantly reduces energy consumption and generates combustible gases with utilization value. The extraction solvent used can achieve closed-loop circulation within the system, greatly reducing solvent consumption and volatile organic compound emissions.

[0025] This invention achieves a fully closed-loop resource conversion. The overall process ultimately realizes the efficient recovery of oil resources and the utilization of solid products in building materials, with no secondary hazardous waste generated throughout the entire process, truly achieving "complete utilization".

[0026] This invention uses green solvents, emphasizing environmental friendliness and engineering feasibility. The solvents or their composite systems employed are characterized by low toxicity, easy biodegradability, and high recovery rates, ensuring separation efficiency while minimizing potential impacts on the environment and operators.

[0027] This invention adheres to the "waste-to-waste" concept in catalyst selection. It employs a supported metal catalyst, clearly specifying the sources of the active component and the support. For example, it utilizes solid waste such as fly ash and waste desulfurizing agents from the plant as catalyst supports, which not only reduces catalyst costs but also achieves waste resource utilization. This catalyst can effectively promote the directional cracking of polycyclic aromatic hydrocarbons during the low-temperature pyrolysis stage, improving product cleanliness.

[0028] This invention features an innovative combination of process parameters. By optimizing multiple sets of operating parameters, such as "extraction temperature-pressure-solvent ratio" and "pyrolysis temperature-catalyst addition amount," a specific ratio is formed, thereby achieving the best overall recovery efficiency and treatment effect.

[0029] This invention sets strict standards for the performance and safety of the final building materials. It not only ensures that solid residues meet the requirements for harmlessness, but also further processes them into building materials such as permeable bricks and lightweight aggregates that meet national standards, possessing practical engineering application value.

[0030] This invention, through systematic process innovation of multi-stage resource separation and progressive deep pyrolysis, is significantly superior to existing traditional treatment methods such as recycling or incineration in terms of economic benefits and environmental safety, and has broad prospects for promotion and application. Attached Figure Description

[0031] Figure 1 The complete flowchart provided for a preferred embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Generally, the embodiments of the present invention described and shown in the accompanying drawings are characteristic technologies and solutions. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] Please see Figure 1 A method for predicting the tensile properties of carbon structural steel, mainly including:

[0034] Step 1: Pretreatment and Conditioning

[0035] Tar residue is mixed with light circulating oil or bio-based solvents in a specific ratio, typically between 0.5:1 and 0.8:1 by mass, to ensure optimal treatment results. Within this range, the viscosity of the mixture is significantly reduced, facilitating subsequent operations. Ultrasonic or microwave-assisted stirring techniques, applying high-frequency vibration or electromagnetic wave energy, effectively break up large particle agglomerates, promoting uniform particle dispersion and initially dissociating encapsulated organic matter. This process not only improves treatment efficiency but also achieves better overall mixing, allowing most of the organic matter to be released, laying the foundation for subsequent resource recovery or environmental treatment. Improved particle dispersion helps reduce clogging and wear, enhancing the overall process stability and economy.

[0036] Step 2: Step-by-step solvent extraction and separation

[0037] A two-stage extraction process is employed to achieve efficient separation and recovery of different components in mixed oils. The first stage of extraction focuses on the extraction of light oils and phenolic substances, while the second stage targets the recovery of medium-grade tar and asphaltenes.

[0038] In the first-stage extraction, the conditioned feed mixture is pumped into the first extraction tower. A low-boiling-point and environmentally friendly solvent, such as ethyl acetate or dimethyl ether, is used for countercurrent extraction under mild temperature conditions of 40–60°C. Under these conditions, the solvent can effectively dissolve and separate the light components.

[0039] The separated extract phase I mainly consists of low molecular weight aromatics and phenolic compounds. This phase liquid is processed by a vacuum distillation unit to recover the solvent contained therein (the solvent can be purified and returned to the extraction system for recycling), ultimately yielding light fuel oil that can be used directly or as a raw material for downstream chemical production.

[0040] The next step is a secondary extraction process: the residue remaining after the primary extraction is transferred to a second extraction tower. In this stage, N-methylpyrrolidone (NMP), a solvent with stronger selectivity and solubility, is used, and extraction is carried out at a higher temperature (80–120°C). High temperature helps promote the dissolution of medium and heavy components.

[0041] The separated extract phase II contains high-molecular-weight tar components and asphaltenes. After appropriate processing, this material can be used as heavy fuel oil, as a raw material for carbon black production, or for industrial applications such as asphalt modifiers, thus achieving high-value-added utilization of resources.

[0042] Step 3: Low-temperature catalytic pyrolysis of extraction residue

[0043] The raffinate residue after two-stage extraction mainly consists of carbonaceous inorganic matter, insoluble macromolecular polycyclic aromatic hydrocarbons, and heavy metals. These components exhibit high stability and potential environmental risks. The following steps are used to treat it:

[0044] Catalytic modification: Supported metal catalysts are used, typically by supporting transition metals such as Fe or Ni on fly ash or waste molecular sieves to provide high specific surface area and active sites. The residue is uniformly mixed with the supported metal catalyst in a certain proportion to ensure sufficient contact. This catalyst can significantly reduce the pyrolysis activation energy and guide the conversion of organic matter towards specific products through catalytic action, thereby improving reaction efficiency and product selectivity.

[0045] Low-temperature pyrolysis: The pyrolysis process is carried out in an oxygen-free or oxygen-deficient environment at 400–550℃ to avoid oxidation reactions. Within this temperature range, large-molecule polycyclic aromatic hydrocarbons are selectively cracked into hydrogen-rich fuel gas and carbon-rich solid char residue. The pyrolysis time is usually controlled at 30–60 minutes to optimize the cracking effect. The hydrogen-rich fuel gas, whose main components are H2, CH4, CO, etc., has a high calorific value and can be used as fuel for direct heat recovery or, after purification, for energy supply. The solid char residue can be used for further resource utilization.

[0046] Heavy metal solidification: During pyrolysis, inorganic mineral components in the catalyst and materials, such as silicates and aluminates, can effectively solidify heavy metals by forming stable compounds or physical encapsulations to prevent their volatilization and migration. This process reduces the risk of secondary pollution from heavy metals to the environment, while the solidified products can be safely disposed of as building materials or landfill materials.

[0047] Step 4: Targeted utilization of the product as a resource

[0048] Pyrolysis oil and gas: After condensation and separation, pyrolysis oil can be effectively recovered. This pyrolysis oil has a high calorific value and can be used as a fuel oil component in industrial combustion equipment, or it can be further refined. The non-condensable pyrolysis gas, after purification, desulfurization, and deacidification, can be reused for heating the pyrolysis furnace itself, significantly reducing external energy consumption and achieving system energy self-sufficiency and optimized operating costs.

[0049] Pyrolysis Residue / Ash: After extraction and pyrolysis, the total amount of harmful substances such as polycyclic aromatic hydrocarbons in the final solid residue has been significantly reduced, meeting national harmless standards. Furthermore, its physicochemical properties are stable, and it exhibits high environmental safety. This residue can be further used as a raw material for activated carbon or as a precursor for adsorbents, and after activation treatment, it can be used for wastewater purification or waste gas treatment. It can also be mixed with cement, aggregates, etc., to prepare non-fired bricks or roadbed materials, realizing the resource utilization of solid waste and its safe use in building materials, demonstrating good environmental and economic benefits.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that any improvements, modifications, substitutions or variations made by those skilled in the art without departing from the principle of the present invention should be considered as being included within the protection scope of the present invention.

Claims

1. A method for treating tar residue, characterized in that, include: S1. Pre-treat and condition the tar residue to disperse large particles and initially dissociate the encapsulated organic matter. S2, Step-by-step solvent extraction and separation: A two-stage extraction process is adopted, namely, the first stage extraction recovers light oil and phenols, and the second stage extraction recovers medium tar and asphaltenes. S3. Low-temperature catalytic pyrolysis of raffinate residue: The raffinate residue after two-stage extraction is subjected to catalytic modification, low-temperature pyrolysis and heavy metal solidification. S4. Targeted utilization of the product's resources; including: The pyrolysis oil and gas are condensed and separated to recover the pyrolysis oil. After extraction and pyrolysis of the pyrolysis residue / ash, the total amount of polycyclic aromatic hydrocarbons in the final solid residue meets the harmlessness standard.

2. The method for treating tar residue according to claim 1, characterized in that, S1 includes: The tar residue is mixed with light circulating oil or bio-based solvent in a certain proportion and stirred with ultrasonic or microwave assistance to reduce its viscosity, disperse large particle agglomerates, and initially dissociate the encapsulated organic matter.

3. The method for treating tar residue according to claim 2, characterized in that, The mass ratio of solvent to tar residue is 0.5:1 to 0.8:

1.

4. The method for treating tar residue according to claim 1, characterized in that, In S2, the first-stage extraction includes: feeding the conditioned mixture into the first extraction tower and performing countercurrent extraction using the low-boiling-point, recyclable green solvent ethyl acetate or dimethyl ether at a temperature of 40°C to 60°C.

5. The method for treating tar residue according to claim 4, characterized in that, The separated extract phase I is rich in low molecular weight aromatics and phenols. After the solvent is recovered by vacuum distillation, light fuel oil or chemical raw materials are obtained.

6. The method for treating tar residue according to claim 1, characterized in that, In S2, the secondary extraction includes: sending the residue after the primary extraction into a second extraction tower and extracting it using the solvent N-methylpyrrolidone at a temperature of 80–120°C.

7. The method for treating tar residue according to claim 6, characterized in that, The separated extract phase II contains high molecular weight tar and asphaltenes, which, after processing, can be used as heavy fuel oil, carbon black raw material, or asphalt modifier.

8. The method for treating tar residue according to claim 1, characterized in that, The catalytic modification includes: using a supported metal catalyst, loading Fe or Ni onto fly ash or waste molecular sieve, uniformly mixing the residue with the supported metal catalyst, utilizing the catalyst's ability to reduce the pyrolysis activation energy, and guiding the organic matter towards a specific product.

9. The method for treating tar residue according to claim 1, characterized in that, The low-temperature pyrolysis includes: pyrolysis at 400℃~550℃ in an oxygen-free or oxygen-deficient environment; macromolecular polycyclic aromatic hydrocarbons are selectively cracked into hydrogen-rich fuel gas and carbon-rich solid char residue; the hydrogen-rich fuel gas, whose main components are H2, CH4 and CO, is used as fuel to recover thermal energy.

10. The method for treating tar residue according to claim 1, characterized in that, The heavy metal solidification includes: during the pyrolysis process, the inorganic mineral components in the catalyst and materials solidify the heavy metals to prevent them from volatilizing and migrating.

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