Ozone oxidation-based low-sulfur low-nitrogen coal tar pitch production method and production system

Abstract

The invention belongs to the technical field of coal chemical industry, and particularly relates to a production method and a production system of low-sulfur low-nitrogen coal tar pitch based on ozone oxidation. The method comprises the following steps: mixing coal tar pitch with a solvent to obtain mixed oil, heating the mixed oil to 80-120 DEG C, adding a supported iron-based metal oxide catalyst, carrying out an ozone reaction, extracting, and evaporating to obtain the low-sulfur low-nitrogen coal tar pitch. Compared with the prior art, the low-sulfur low-nitrogen coal tar pitch prepared by the method has the advantages that the sulfur content is lower, the effect is improved remarkably, less ozone is used in the reaction process, the oxidation reaction temperature is lower, and the method has positive significance in saving raw materials and reducing energy consumption. The production system disclosed by the invention comprises the dissolution reaction kettle, the oxidation tower, the extraction tower group and the evaporation tower, and by adopting the system, the desulfurization reaction is more sufficient, so that the desulfurization efficiency is improved, meanwhile, a solvent is recycled, raw materials are saved, and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal chemical industry, and particularly relates to a production method and a production system for low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation. Background Art

[0002] China is a major producer of coal tar pitch. The coal tar pitch produced by the coking industry can reach tens of millions of tons annually. Coal tar pitch is widely used in the manufacture of binders and impregnants for carbon electrodes in the metallurgical industry, waterproof and anti-corrosion materials, and road construction materials due to its high carbon content, good fluidity, easy graphitization, excellent pairing with carbonaceous aggregates, rich resources, and low price. At the same time, coal tar pitch is also used as a raw material for producing high-value-added carbon materials such as needle coke, carbon fiber, and lithium-ion battery anodes. However, heteroatom elements such as sulfur and nitrogen in coal tar pitch affect the processing process of the pitch and the quality of downstream products. For example, sulfur and nitrogen in coal tar pitch will produce atmospheric pollutants such as sulfides and nitrides during the processing of coal tar pitch, causing environmental pollution and many environmental problems. At the same time, sulfur and nitrogen in the pitch will remain in high-grade carbon materials such as needle coke and carbon fiber in downstream products, seriously affecting the performance of carbon material products. The sulfur content in coal tar pitch will significantly affect the performance of needle coke, which will have an adverse impact on the quality and performance of needle coke and its products, resulting in a decrease in the bulk density, an increase in the resistivity, and a decrease in the strength of the prepared graphite electrode.

[0003] Coal tar pitch is mainly obtained by removing light fractions (separating monoanthracene oil and dianthracene oil) from coal tar and then performing high-temperature distillation to produce soft pitch. Due to the quality of the coal tar feedstock, currently, the sulfur content of the produced soft pitch is about 0.60%, which is difficult to meet the use requirements of soft pitch in specific applications. Therefore, it is necessary to further reduce the sulfur content in the soft pitch.

[0004] In the prior art, the technical routes for asphalt desulfurization mainly include catalytic hydrogenation and solvent methods. Among them, the catalytic hydrogenation method has complex processes, high safety risks, and high production costs. The solvent method is an asphalt desulfurization technology with relatively low costs and low safety risks. For example, in the prior art, the invention patent with the application number 202310363129.8 discloses an asphalt desulfurization method, including: mixing asphalt with a solvent to obtain a mixed oil; heating (150 - 400 °C) the mixed oil; the heated mixed oil enters an oxidation tower for flash evaporation, and a gas oxidant is introduced for reaction; after the reaction, the solvent and the unreacted gas oxidant enter the light phase and escape from the top of the tower; the asphalt enters the heavy phase and is discharged from the bottom of the tower; the asphalt enters a washing tank, a desulfurization liquid is introduced, and they are mixed and stirred; the sulfur-rich desulfurization liquid is discharged from the upper part of the washing tank, and the desulfurized asphalt is discharged from the bottom of the washing tank. The gas oxidant includes at least one of ozone, oxygen, or air. However, in the actual production process, when using ozone as the gas catalyst, although the sulfur content can be reduced to a relatively low level, the heating temperature of the mixed oil is relatively high (150 - 400 °C), resulting in high energy consumption. Summary of the Invention

[0005] Based on this, the present application provides a production method and a production system for low-sulfur and low-nitrogen coal tar asphalt based on ozone oxidation to solve the technical problem of high energy consumption caused by the relatively high heating temperature of the mixed oil in the prior art.

[0006] The technical solution of the present application to solve the above technical problems is as follows:

[0007] A production method for low-sulfur and low-nitrogen coal tar asphalt based on ozone oxidation, characterized by comprising the following steps:

[0008] S10. Adding a solvent to coal tar asphalt, heating to a first preset temperature and mixing evenly to obtain a mixed oil;

[0009] S20. Heating the mixed oil to 80 °C to 120 °C, introducing ozone for reaction in the presence of a catalyst to obtain a primary mixed oil; the catalyst includes a supported iron-based metal oxide catalyst;

[0010] S30. Extracting and evaporating the primary mixed oil to obtain low-sulfur and low-nitrogen coal tar asphalt.

[0011] A production system for low-sulfur and low-nitrogen coal tar asphalt based on ozone oxidation, comprising:

[0012] A dissolution reactor, the inlet of the dissolution reactor is connected to a coal tar asphalt tank and a solvent tank, and the bottom outlet of the dissolution reactor is provided with a mixed oil discharge pipe;

[0013] Oxidation tower. In the height direction, a spraying layer, a fixed bed, and a gas distributor are arranged from top to bottom in the oxidation tower. A primary discharge pipe is provided at the bottom outlet of the oxidation tower. The other end of the mixed oil discharge pipe is connected to the primary discharge pipe. The primary discharge pipe is also connected with a circulation pipe. A first heater is arranged on the circulation pipe. The other end of the circulation pipe is connected to the spraying layer. The fixed bed is used for filling catalysts. The gas distributor is connected with an ozone feed pipe;

[0014] Extraction tower group. The other end of the primary discharge pipe is connected to the light liquid inlet of the extraction tower group;

[0015] Evaporation tower. The light liquid outlet of the extraction tower group is connected to the inlet of the evaporation tower. The bottom outlet of the evaporation tower is connected with a finished product extraction pipe. The top outlet of the evaporation tower is connected to the inlet of the solvent tank.

[0016] Compared with the prior art, the present application has at least the following advantages:

[0017] A production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation disclosed in the present application. After mixing coal tar pitch with a solvent to obtain a mixed oil, by heating the mixed oil to 80°C to 120°C and adding a supported iron-based metal oxide catalyst while reacting with ozone, and then extracting and evaporating, low-sulfur and low-nitrogen coal tar pitch can be obtained. The combined action of ozone and the supported iron-based metal oxide catalyst promotes the occurrence of the oxidation reaction, strengthening the desulfurization and denitrification effects. Experiments prove that the desulfurization rate of the low-sulfur and low-nitrogen coal tar pitch prepared by the scheme of the present application reaches 76.7%, and the denitrification rate reaches 54%. Among them, the sulfur content can be as low as 0.14%. Compared with the lowest sulfur content of 0.275% in the prior art (background technology document 202310363129.8), the sulfur content has decreased by 0.135%, and the decrease rate is 49%. The effect is significantly improved. Moreover, less ozone is used in the reaction process, and the oxidation reaction temperature is also lower, which has a positive significance for saving raw materials and reducing energy consumption.

[0018] The low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation disclosed in this application includes a dissolution reactor, an oxidation tower, an extraction tower group, and an evaporation tower. Coal tar pitch and a solvent are mixed and heated in the dissolution reactor to obtain a mixed oil. The mixed oil enters the oxidation tower after heating and is sprayed downward from the spray layer at the upper part of the oxidation tower. Ozone is evenly distributed in the oxidation tower through a gas distributor. The fixed bed is filled with a catalyst, and the mixed oil undergoes a sufficient oxidation reaction in the oxidation tower to effectively separate sulfur and nitrogen in the coal tar pitch. The reacted primary mixed oil is extracted in the extraction tower group to remove sulfur, nitrogen, organic substances, salts, etc. The light phase after extraction, that is, the mixture of coal tar pitch and the solvent, is evaporated in the evaporation tower to obtain the finished product of low-sulfur and low-nitrogen coal tar pitch. The evaporated solvent is transported to the solvent tank for recycling. Using this system makes the desulfurization reaction more sufficient, thereby improving the desulfurization and denitrification efficiency. At the same time, the solvent is recycled, saving raw materials and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a system diagram of the low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation according to an embodiment of this application.

[0020] In the figure: dissolution reactor 100, coal tar pitch tank 110, solvent tank 120, mixed oil discharge pipe 130, second heater 131, oxidation tower 200, spray layer 210, fixed bed 220, gas distributor 230, primary discharge pipe 240, circulation pipe 250, first heater 251, ozone feed pipe 260, gas discharge pipe 270, first extraction tower 300, waste liquid pipe 310, second extraction tower 400, heavy liquid feed pipe 410, evaporation tower 500, finished product extraction pipe 510, asphalt circulation pipe 520, third heater 530. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to the relevant drawings. The preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0022] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right", "top", "bottom", "bottom end", "top end" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the specification herein are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] In a specific embodiment of this application, a production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation is characterized by comprising the following steps:

[0025] S10. Add a solvent to the coal tar pitch, heat it to a first preset temperature and mix evenly to obtain a mixed oil;

[0026] Coal tar pitch is one of the main products of coal tar processing and is the residue after the distillation fraction of coal tar is extracted. It is a brown or black viscous liquid. When desulfurizing it, a solvent needs to be added to dissolve it. Further, the solvent includes at least one of wash oil or anthracene oil, and the first preset temperature is 50°C to 110°C. To make the dissolution sufficient and facilitate the subsequent production process, the mass ratio of coal tar pitch to the solvent is 1:(1 to 5).

[0027] S20. Heat the mixed oil to 80°C to 120°C, and introduce ozone to react in the presence of a catalyst to obtain a primary mixed oil; the catalyst includes a supported iron-based metal oxide catalyst;

[0028] Ozone (O3) provides an oxidation environment for the reaction. In a preferred embodiment, the mass ratio of the mixed oil to the ozone is 1:(0.2 to 0.5).

[0029] The catalyst includes a supported iron-based metal oxide catalyst. This type of catalyst can be reused and is easy to separate. Further, the substrate of the supported iron-based metal oxide catalyst includes any one of diatomaceous earth and alumina, and the iron-based metal includes any two of titanium, vanadium, chromium, manganese, iron, cobalt, and nickel. For example, iron-manganese supported on alumina, cobalt-nickel supported on diatomaceous earth, etc. This type of catalyst promotes the oxidation reaction by providing variable valences of metal ions (such as V 5+ / V 4+ , Co 3+ / Co 2+ , Fe 3+ / Fe 2+ ). In a preferred embodiment, the addition amount of the catalyst is 0.5 wt% to 3 wt% of the coal tar pitch.

[0030] The preparation method of the catalyst is as follows: (1) Pretreat the substrate material. The pretreatment method depends on the specific substrate material. For example, when the substrate material is diatomite, wash the diatomite repeatedly with deionized water to remove surface impurities, and then dry it at a certain temperature (such as 100°C to 120°C) for several hours to remove moisture. Then calcine the dried diatomite in a muffle furnace. The calcination temperature is usually between 400°C and 600°C, and the calcination time is 2 to 4 hours to increase the specific surface area and pore structure of the diatomite and enhance its loading capacity. When the substrate material is alumina, select a suitable alumina support, such as γ-alumina. First, soak the alumina in dilute acid (such as dilute nitric acid, dilute hydrochloric acid, etc.) for a period of time to remove surface impurities and part of the amorphous alumina, and improve the purity and activity of the support. The soaking time is generally 1 to 2 hours, and the acid concentration is 0.1 to 1 mol / L. Then wash it with deionized water until neutral, dry it at 100°C to 120°C for several hours, and then calcine it in a muffle furnace at 500°C to 700°C for 3 to 5 hours to obtain a stable crystal phase structure and a large specific surface area. (2) Prepare the precursor solution. Weigh a certain amount of iron-based metal salts (such as titanium nitrate, ammonium metavanadate, chromium nitrate, manganese sulfate, iron nitrate, cobalt nitrate, nickel nitrate, etc.). In this application, two iron-based metal salts are loaded, so weigh two iron-based metal salts and then dissolve them in an appropriate amount of deionized water to prepare a solution. (3) Add the pretreated substrate material into deionized water to form a suspension. Under stirring, slowly drop the precursor solution into the substrate material suspension, and at the same time drop a precipitant (such as potassium hydroxide, potassium carbonate, etc.) to uniformly precipitate metal ions on the alumina / diatomite. (4) After precipitation, perform an aging treatment. Let the suspension stand and age at a certain temperature (such as room temperature to 60°C) for a period of time, usually 1 to 24 hours. After aging, filter to separate the alumina / diatomite loaded with iron-based metal precipitates, and wash it with deionized water multiple times until there are no impurity ions in the washing solution. (5) Dry and calcine. Dry the washed sample at 80°C to 100°C for 6 to 10 hours, and then calcine it in a muffle furnace. The calcination temperature is generally between 400°C and 700°C, and the calcination time is 3 to 5 hours to convert the metal precipitate into an active phase and firmly load it on the alumina / diatomite to obtain a supported iron-based metal oxide catalyst.

[0031] S30. Extract and evaporate the primary mixed oil to obtain low-sulfur and low-nitrogen coal tar pitch.

[0032] It should be noted that in the above embodiments, the process temperatures and process times involved are all a temperature or time adopted during the experiment. Those skilled in the art can make reasonable adjustments within the error range based on the process temperatures and process times provided by the present invention, and all should be included within the protection scope of the present invention.

[0033] The technical solutions and effects of the present invention are further illustrated by specific experimental examples below.

[0034] 1. Experimental materials and methods

[0035] 1.1 Experimental materials

[0036] Coal tar pitch, from Ningxia Xitai Coal Chemical Industry Co., Ltd.; other raw materials and reagents are commercially available and can be used without further purification. The determination of sulfur and nitrogen contents in coal tar pitch follows relevant national standards of China (GB / T 38395-2019 Determination of sulfur and nitrogen contents in coal tar). The parameters of the coal tar pitch samples and the sulfur and nitrogen contents in the coal pitch are shown in Table 1.

[0037] Table 1 Parameters of coal tar pitch samples

[0038]

[0039] 1.2 Determination and calculation of sulfur content

[0040] The total sulfur content of coal tar pitch was measured using a KZDL-500 type micro automatic sulfur analyzer (Huadian Analytical Instruments Co., Ltd., Hebi City).

[0041] Calculation of desulfurization rate: The desulfurization rate refers to the percentage of sulfur compounds removed from coal pitch, that is, the ratio of the sulfur compounds removed after the treatment of coal pitch to the sulfur content in the original coal pitch, denoted as DRS, and the following calculation formula is as follows:

[0042]

[0043] In the formula: DR S —Desulfurization rate, %;

[0044] S t1 —Total sulfur content in the pitch before desulfurization;

[0045] S t2 —Sulfur content in the pitch sample after treatment.

[0046] 1.3 Determination and calculation of nitrogen content

[0047] The total ammonia content in coal pitch was determined using an HD-CN500 automatic nitrogen analyzer, and this equipment meets the national standards for the ammonia content in coal pitch.

[0048] Calculation of denitrification rate: The denitrification rate refers to the percentage of nitrogen compounds removed from coal pitch, that is, the ratio of the nitrogen compounds removed after the treatment of coal pitch to the nitrogen content in the original coal pitch, denoted as DR, and the following calculation formula is as follows:

[0049]

[0050] In the formula: DRN — Denitrification rate, %;

[0051] N t1 — Total sulfur content in asphalt before denitrification;

[0052] N t2 — Nitrogen content in the asphalt sample after treatment.

[0053] 2. Example 1

[0054] Preparation of Catalyst 1:

[0055] (1) Wash 2 kg of diatomite with deionized water repeatedly to remove surface impurities, and then dry it at 100 °C to remove moisture. Then calcine the dried diatomite in a muffle furnace at a temperature of 500 °C for 3 hours;

[0056] (2) Preparation of the precursor solution. Weigh 1.94 kg of cobalt nitrate, and then dissolve it in 1.94 kg of deionized water (the mass ratio of cobalt nitrate to deionized water is 1:1) to prepare the precursor solution;

[0057] (3) Add the pretreated diatomite to 4 kg of deionized water to make a suspension. Under stirring, slowly drop the precursor solution into the diatomite suspension, and at the same time add the precipitant sodium hydroxide to make the pH value of the solution 8.

[0058] (4) After precipitation, carry out aging treatment. Let the suspension stand and age at 30 °C (such as room temperature to 60 °C) for 12 h. After aging, filter to separate the diatomite loaded with cobalt nitrate precipitate, and wash it with deionized water multiple times until there are no impurity ions in the washing solution. (5) Dry the washed sample at 90 °C for 8 hours, and then calcine it in a muffle furnace at 600 °C for 4 hours to obtain the supported iron-based metal oxide catalyst, that is, the diatomite-supported cobalt catalyst.

[0059] Preparation of Catalyst 2:

[0060] (1) Wash 2 kg of diatomite with deionized water repeatedly to remove surface impurities, and then dry it at 100 °C to remove moisture. Then calcine the dried diatomite in a muffle furnace at a temperature of 500 °C for 3 hours;

[0061] (2) Preparation of the precursor solution. Weigh 974 g of cobalt nitrate and 974 g of nickel nitrate, and then dissolve them in 1.94 kg of deionized water (the mass ratio of cobalt nitrate to deionized water is 1:1) to prepare the precursor solution;

[0062] (3) Add the pretreated diatomite to 4 kg of deionized water to make a suspension. Under stirring, slowly drip the precursor solution into the diatomite suspension, and at the same time drip the precipitant sodium hydroxide to make the pH value of the solution 8.

[0063] (4) After precipitation, carry out aging treatment. Let the suspension stand and age at 30 °C (such as from room temperature to 60 °C) for 12 h. After aging, separate the diatomite loaded with cobalt nitrate precipitate by filtration, and wash it with deionized water many times until there are no impurity ions in the washing liquid. (5) Dry the washed sample at 90 °C for 8 hours, and then calcine it in a muffle furnace at 600 °C for 4 hours to obtain a supported composite iron-based metal oxide catalyst, that is, a diatomite-supported cobalt-nickel catalyst.

[0064] 3. Example 2

[0065] Add 200 kg of coal tar pitch to the dissolution reactor, and add 400 kg of wash oil to it. The temperature in the reactor is 70 °C, and mix well for 1 hour to obtain a mixed oil;

[0066] Heat the mixed oil to 80 °C, make the mixed oil contact with 2 kg of Catalyst 1, and introduce 180 kg of ozone (the mass ratio of the mixed oil to ozone is 1:0.3) to react to obtain a primary mixed oil; Wash and evaporate the primary mixed oil to obtain a low-sulfur and low-nitrogen coal tar pitch, marked as Sample 1.

[0067] 4. Example 3

[0068] The method is the same as that of Example 2, except that the mixed oil is heated to 90 °C. The obtained low-sulfur and low-nitrogen coal tar pitch is marked as Sample 2.

[0069] 5. Example 4

[0070] The method is the same as that of Example 2, except that the mixed oil is heated to 100 °C. The obtained low-sulfur and low-nitrogen coal tar pitch is marked as Sample 3.

[0071] 6. Example 5

[0072] The method is the same as that of Example 2, except that the mixed oil is heated to 110 °C. The obtained low-sulfur and low-nitrogen coal tar pitch is marked as Sample 4.

[0073] 7. Example 6

[0074] The method is the same as that of Example 2, except that the mixed oil is heated to 120 °C. The obtained low-sulfur and low-nitrogen coal tar pitch is marked as Sample 5.

[0075] 8. Example 7

[0076] The method was the same as that of Example 2, except that the mixed oil was heated to 140 °C. The obtained low-sulfur and low-nitrogen coal tar pitch was labeled as Sample 6.

[0077] 9. Example 8

[0078] The method was the same as that of Example 2, except that the mixed oil was heated to 60 °C. The obtained low-sulfur and low-nitrogen coal tar pitch was labeled as Sample 7.

[0079] 10. Example 9

[0080] The method was the same as that of Example 4, except that Catalyst 1 was replaced by Catalyst 2 for contact. The obtained low-sulfur and low-nitrogen coal tar pitch was labeled as Sample 8.

[0081] 11. Comparative Example

[0082] The method was the same as that of Example 4, except that there was no catalyst, and the obtained coal tar pitch was labeled as Sample 9.

[0083] The sulfur content and nitrogen content of the above examples and comparative example samples were tested. The sulfur content and nitrogen content of each sample are shown in the following table:

[0084] Table 2 Sulfur content and nitrogen content of each sample

[0085]

[0086] Please refer to Table 2. The average sulfur content of Samples 1 to 5 is about 0.2%, which is about 0.4% lower than that of the raw coal tar pitch, and the average desulfurization rate is 66.7%; the nitrogen content is about 0.5, which is about 0.37% lower than that of the raw coal tar pitch, and the average denitrification rate is 42.5%. The sulfur content and nitrogen content of Sample 8 are the lowest. The sulfur content is 0.14%, which is 0.46% lower than that of the raw coal tar pitch, and the desulfurization rate is as high as 76.7%. Compared with the lowest sulfur content of 0.275% in the prior art (Background Technical Document 202310363129.8), the sulfur content has decreased by 0.135%, and the reduction rate is 49%, showing a significant improvement in effect. The nitrogen content of Sample 8 is 0.4%, which is 0.47% lower than that of the raw coal tar pitch, and the denitrification rate is as high as 54%, with excellent denitrification effect. This shows that when other reaction conditions are the same, using Catalyst 2, that is, the supported composite iron-based metal catalyst (cobalt-nickel catalyst supported on diatomite), can obtain better desulfurization and denitrification effects than using Catalyst 1 (cobalt catalyst supported on diatomite), and the sulfur content and nitrogen content of the prepared sample are lower. At the same time, in this application, the mass ratio of the mixed oil to the ozone is 1:(0.2 to 0.5), using less ozone than the prior art, and the oxidation reaction temperature is 80 °C to 120 °C, which is also lower than the prior art.

[0087] The reduction in sulfur and nitrogen content of Sample 6 and Sample 7 is not very significant, which may be caused by reasons such as too low reaction temperature (Sample 6) or too high reaction temperature (Sample 7).

[0088] The sulfur and nitrogen content of Sample 9 has hardly decreased, indicating that under the experimental conditions of this application, only introducing ozone without adding a catalyst cannot significantly reduce the sulfur and nitrogen content in coal tar pitch.

[0089] In another specific embodiment of this application, a low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation includes:

[0090] A dissolution reactor 100, an inlet of the dissolution reactor 100 is connected to a coal tar pitch tank 110 and a solvent tank 120, and a bottom outlet of the dissolution reactor 100 is provided with a mixed oil discharge pipe 130; an oxidation tower 200, in the height direction, a spray layer 210, a fixed bed 220, and a gas distributor 230 are arranged from top to bottom in the oxidation tower 200, a bottom outlet of the oxidation tower 200 is provided with a primary discharge pipe 240, the other end of the mixed oil discharge pipe 130 is connected to the primary discharge pipe 240, the primary discharge pipe 240 is further connected to a circulation pipe 250, a first heater 251 is arranged on the circulation pipe 250, the other end of the circulation pipe 250 is connected to the spray layer 210, the fixed bed 220 is used for filling a catalyst, and the gas distributor 230 is connected to an ozone feed pipe 260; an extraction tower group, the other end of the primary discharge pipe 240 is connected to a light liquid inlet of the extraction tower group; an evaporation tower 500, a light liquid outlet of the extraction tower group is connected to an inlet of the evaporation tower 500, a bottom outlet of the evaporation tower 500 is connected to a finished product extraction pipe 510; a top outlet of the evaporation tower 500 is connected to an inlet of the solvent tank 120.

[0091] Specifically, it should be noted that the spraying layer 210 mainly sprays the mixed oil onto the fixed bed 220 to make it contact the catalyst in the fixed bed 220 evenly. The spraying direction of the spraying layer 210 should be downward, so that the sprayed mixed oil can contact the input ozone at a lower position and the catalyst in the fixed bed 220, thereby undergoing an oxidation reaction. At the same time, the mixed oil is sprayed out through the spraying layer 210 to form small droplets or a liquid film, which fully contacts the ozone and the catalyst, accelerating the oxidation reaction. The fixed bed 220 is also called a fixed bed reactor, and a catalyst is filled inside; the gas distributor 230 can make the ozone evenly distributed across the entire cross-section of the oxidation tower 200, making the reaction faster. The dissolution reactor 100 has a heating function, which can be in the form of jacket heating, so that the coal tar pitch and the solvent are mixed and heated in the dissolution reactor 100. There are two connection methods between the mixed oil discharge pipe 130 and the oxidation tower 200: the first is that the mixed oil discharge pipe 130 is directly connected to the spraying layer 210 of the oxidation tower 200, and the second is that the mixed oil discharge pipe 130 is connected to the primary discharge pipe 240, and then connected to the spraying layer 210 through the circulation pipe 250 connected by the primary discharge pipe 240. In this application, the second method is preferably used. In this process, the unreacted mixed oil discharged from the oxidation tower 200 and the mixed oil from the mixed oil discharge pipe 130 are heated by the first heater 251 on the circulation pipe 250 and then sent to the spraying layer 210 to react in the oxidation tower 200.

[0092] The production process is as follows: The coal tar pitch and the solvent are mixed and heated in the dissolution reactor 100 to obtain the mixed oil, realizing step S10; the mixed oil enters the primary discharge pipe 240 through the mixed oil discharge pipe 130, flows through the circulation pipe 250 connected by the primary discharge pipe 240, is heated by the first heater 251 on the circulation pipe 250, then enters the spraying layer 210 of the oxidation tower 200, and is sprayed out from the spraying layer 210. At the same time, ozone is sent into the gas distributor 230 through the ozone feed pipe 260, and after being evenly distributed by the gas distributor 230, it contacts the mixed oil in the fixed bed 220 and undergoes an oxidation reaction under the action of the catalyst in the fixed bed 220 to generate the primary mixed oil, realizing step S20; the reacted primary mixed oil is transported to the light liquid inlet of the extraction tower group through the primary discharge pipe 240, and after extraction in the extraction tower group, the sulfur, nitrogen, organic matter, salts, etc. are removed. The extracted light phase, that is, the mixture of low-sulfur and low-nitrogen coal tar pitch and the solvent, is discharged from the light liquid outlet of the extraction tower and sent to the evaporation tower 500. After evaporation in the evaporation tower 500, the low-sulfur and low-nitrogen coal tar pitch finished product is obtained and taken out from the finished product extraction pipe 510 at the bottom of the evaporation tower 500. The evaporated solvent is discharged from the top outlet of the evaporation tower 500 and then transported to the solvent tank 120 for recycling, realizing step S30. Using this set of systems makes the desulfurization reaction more complete, thereby improving the desulfurization efficiency. At the same time, the solvent is recycled, saving raw materials and reducing costs.

[0093] In a preferred embodiment, a gas discharge pipe 270 is further provided at the top of the oxidation tower 200 to extract the waste gas generated by the reaction in the tower. Generally, the gas discharge pipe 270 is also connected to a post-treatment device for treating the waste gas.

[0094] In order to make the primary mixed oil be more fully extracted and more efficiently remove sulfur, nitrogen, organic substances and salts therein, in a preferred embodiment, the extraction tower group includes a first extraction tower 300 and a second extraction tower 400 arranged in series. The other end of the primary discharge pipe 240 is connected to the light liquid inlet of the first extraction tower 300. The light liquid outlet of the first extraction tower 300 is connected to the light liquid inlet of the second extraction tower 400. The light liquid outlet of the second extraction tower 400 is connected to the inlet of the evaporation tower 500. A heavy liquid feed pipe 410 is provided on the second extraction tower 400. The heavy liquid outlet of the second extraction tower 400 is connected to the heavy liquid inlet of the first extraction tower 300. The heavy liquid outlet of the first extraction tower 300 is connected to a waste liquid pipe 310. In the prior art, an extraction tower generally has a light liquid inlet, a light liquid outlet, a heavy liquid inlet and a heavy liquid outlet. In this application, the light liquid fed into the first extraction tower 300 is the primary mixed oil, and the heavy liquid input into the second extraction tower 400 is water. On the one hand, the primary mixed oil after the oxidation reaction is transported through the primary discharge pipe 240 to the light liquid inlet of the first extraction tower 300. After extraction in the first extraction tower 300, it is output from the light liquid outlet of the first extraction tower 300 and fed into the second extraction tower 400 through the light liquid inlet of the second extraction tower 400 for further extraction. The light liquid after extraction in the second extraction tower 400 is a mixture of low-sulfur and low-nitrogen coal tar pitch and solvent, which is discharged from the light liquid outlet of the second extraction tower 400. On the other hand, water is fed into the second extraction tower 400 through the heavy liquid inlet of the second extraction tower 400 to extract the light liquid in the second extraction tower 400 (i.e., the primary mixed oil after extraction in the first extraction tower 300), and then is fed into the heavy liquid inlet of the first extraction tower 300 through the heavy liquid outlet of the second extraction tower 400 to extract the light liquid in the first extraction tower 300 (i.e., the primary mixed oil). The heavy liquid generated after extraction, that is, the waste liquid containing sulfur, nitrogen, organic substances and salts, is discharged from the heavy liquid outlet of the first extraction tower 300 through the waste liquid pipe 310.

[0095] As described above, the reaction between the mixed oil and ozone in the oxidation tower 200 needs to be carried out under heating conditions, which is 80°C to 120°C in this application. A second heater 131 is provided on the mixed oil discharge pipe 130, which can preheat the mixed oil so that it enters the primary discharge pipe 240 and the circulation pipe 250 at a certain temperature, saving the heating time in the first heater 251 and ensuring the continuous production.

[0096] Furthermore, a bitumen circulation pipe 520 is provided at the bottom outlet of the evaporation tower 500. A third heater 530 is provided on the bitumen circulation pipe 520. The other end of the bitumen circulation pipe 520 is connected to the circulation inlet at the top of the evaporation tower 500. The bitumen circulation pipe 520 is connected with a finished product extraction pipe 510. The heavy components evaporated by the evaporation tower 500 enter the bitumen circulation pipe 520 from the bottom outlet, are heated by the third heater 530, and enter the evaporation tower 500 again for recirculation through the circulation inlet at the top of the evaporation tower 500. At the same time, the qualified heavy components, that is, low-sulfur and low-nitrogen coal tar pitch, can be extracted from the finished product extraction pipe 510.

[0097] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation, characterized in that, It includes the following steps: S10. Add a solvent to coal tar pitch, heat it to a first preset temperature and mix evenly to obtain a mixed oil; S20. Heat the mixed oil to 80°C to 120°C, and introduce ozone for reaction in the presence of a catalyst to obtain a primary mixed oil; the catalyst includes a supported iron-based metal oxide catalyst; S30. Extract and evaporate the primary mixed oil to obtain low-sulfur and low-nitrogen coal tar pitch.

2. The production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to claim 1, wherein In step S10, the solvent includes at least one of wash oil or anthracene oil.

3. The production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to claim 1, wherein In step S10, the first preset temperature is 50°C to 110°C.

4. The production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to claim 1, characterized in that, In step S20, the mass ratio of the mixed oil to the ozone is 1:(0.2 to 0.5).

5. The production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to claim 1, characterized in that In step S20, the substrate of the supported iron-based metal oxide catalyst includes any one of diatomite and alumina, and the iron-based metals include any two of titanium, vanadium, chromium, manganese, iron, cobalt, and nickel.

6. The production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to claim 1, characterized in that, In step S20, the addition amount of the catalyst is 0.5wt% to 3wt% of the coal tar pitch.

7. A low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation, characterized in that, Applying the production method of low-sulfur and low-nitrogen coal tar pitch based on ozone oxidation according to any one of claims 1 to 6, includes: A dissolution reactor, the inlet of the dissolution reactor is connected with a coal tar pitch tank and a solvent tank, and the bottom outlet of the dissolution reactor is provided with a mixed oil discharge pipe; An oxidation tower, in the height direction, a spraying layer, a fixed bed, and a gas distributor are arranged from top to bottom in the oxidation tower. The bottom outlet of the oxidation tower is provided with a primary discharge pipe, the other end of the mixed oil discharge pipe is connected to the primary discharge pipe, the primary discharge pipe is also connected with a circulation pipe, a first heater is arranged on the circulation pipe, the other end of the circulation pipe is connected to the spraying layer, the fixed bed is used for filling the catalyst, and the gas distributor is connected with an ozone feed pipe; An extraction tower group, the other end of the primary discharge pipe is connected with the light liquid inlet of the extraction tower group; An evaporation tower, the light liquid outlet of the extraction tower group is connected with the inlet of the evaporation tower, the bottom outlet of the evaporation tower is connected with a finished product extraction pipe; the top outlet of the evaporation tower is connected with the inlet of the solvent tank.

8. The low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation according to claim 7, characterized in that, The extraction tower group includes a first extraction tower and a second extraction tower arranged in series. The other end of the primary discharge pipe is connected with the light liquid inlet of the first extraction tower, the light liquid outlet of the first extraction tower is connected with the light liquid inlet of the second extraction tower, and the light liquid outlet of the second extraction tower is connected with the inlet of the evaporation tower; the second extraction tower is provided with a heavy liquid feed pipe, the heavy liquid outlet of the second extraction tower is connected with the heavy liquid inlet of the first extraction tower, and the heavy liquid outlet of the first extraction tower is connected with a waste liquid pipe.

9. The low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation according to claim 7, characterized in that, A second heater is arranged on the mixed oil discharge pipe.

10. The low-sulfur and low-nitrogen coal tar pitch production system based on ozone oxidation according to claim 7, characterized in that, The bottom outlet of the evaporation tower is provided with an asphalt circulation pipe, a third heater is arranged on the asphalt circulation pipe, the other end of the asphalt circulation pipe is connected with the circulation inlet at the top of the evaporation tower, and the asphalt circulation pipe is connected with the finished product extraction pipe.

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