Application of deoiled bitumen in the preparation of prebaked anode binders and prebaked anodes

Abstract

This invention provides an application of deoiled bitumen in the preparation of prebaked anode binders. The deoiled bitumen has a softening point of not less than 70℃, a coking value of not less than 30%, and a C / H atomic ratio of not less than 1.0. Modified deoiled bitumen is obtained from this deoiled bitumen through a modification process. This modified deoiled bitumen is the oil-based prebaked anode binder. The modified bitumen has a softening point of 100–105℃, a viscosity of 8–12 Pa·s at 140℃, a viscosity of 1.2–2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55–58%, and a C / H atomic ratio of ≥1.2. Compared to modified coal tar pitch, a coal-based prebaked anode binder, it is more environmentally friendly and has superior air oxidation resistance, carbon dioxide reactivity, and wettability. It can replace a portion of modified coal tar pitch as a prebaked anode binder for preparing prebaked anodes. The performance of the prebaked anode meets current industry standards.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, and in particular relates to the application of deoiled bitumen in the preparation of prebaked anode binders and prebaked anodes. Background Technology

[0002] Prebaked anodes are carbon blocks produced using petroleum coke and pitch coke as aggregates and coal tar pitch as a binder. Coal tar pitch typically accounts for 16-19 wt%. One of their functions is to impart plasticity to the paste during mixing and molding, allowing it to meet molding requirements. When coal tar pitch is liquid, it wets, binds, and mixes carbonaceous aggregates and powders into a plastic paste. After pressing and cooling, the binder pitch hardens, solidifying the aggregates and powders into a green body. Another function is to form carbon film bonding bridges between solid carbonaceous materials during roasting, binding them into a whole and giving it a certain mechanical strength. During high-temperature roasting, the binder coal tar pitch undergoes a carbonization reaction, generating binding coke and forming a good solid bond, giving the product a fixed geometric shape and performance characteristics. Prebaked anodes are used as anode materials in electrolytic cells during aluminum electrolysis, acting as both conductors and participating in electrochemical reactions, thus being consumed.

[0003] Coal tar pitch contains a large amount of toxic and harmful substances such as anthracene and phenols, which are not environmentally friendly and are detrimental to health. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide the application of deoiled bitumen in the preparation of prebaked anode binders and prebaked anodes. The invention makes full use of deoiled bitumen to prepare oil-based prebaked anode binders. Compared with modified coal tar pitch, it has superior environmental protection, air oxidation, carbon dioxide reactivity and wettability, and can replace part of modified coal tar pitch as a prebaked anode binder for the preparation of prebaked anodes.

[0005] This invention provides the application of deoiled bitumen in the preparation of prebaked anode binders;

[0006] The softening point of the deoiled bitumen is not lower than 70℃, the coking value is not less than 30%, and the C / H atomic ratio is not less than 1.0.

[0007] This invention provides an oil-based prebaked anode binder, wherein the oil-based prebaked anode binder has a softening point of 100-105℃, a viscosity of 8-12 Pa·s at 140℃, a viscosity of 1.2-2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55-58%, and a C / H atomic ratio of ≥1.2.

[0008] Preferably, the oil-based prebaked anode binder is prepared by heat-treating deoiled bitumen obtained by solvent extraction of residue oil obtained from atmospheric and vacuum distillation at 300-500°C and 100-300 rpm for 5-15 hours.

[0009] This invention provides a prebaked anode binder, the raw materials of which include modified coal tar pitch and oil-based prebaked anode binder in a mass ratio of (7-9):(1-3).

[0010] The oil-based prebaked anode binder has a softening point of 100–105℃, a viscosity of 8–12 Pa·s at 140℃, a viscosity of 1.2–2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55–58%, and a C / H atomic ratio of ≥1.2.

[0011] Preferably, the modified coal tar pitch has a moisture content of ≤5.0%, an ash content of ≤0.3%, a coking value of ≥54%, a softening point of 100-110℃, and a volatile matter content of ≤56%.

[0012] Preferably, the oil-based prebaked anode binder has a softening point of 103–105°C, a coking value of 57–57.3%, a viscosity of 10.8–11.85 Pa·s at 140°C, a viscosity of 1.3–1.705 Pa·s at 160°C, and a C / H atomic ratio of 1.2–1.4.

[0013] Preferably, the mass ratio of the oil-based prebaked anode binder to the modified coal tar pitch is 3:7 or 1:9.

[0014] The present invention provides a prebaked anode, comprising the prebaked anode binder described in the above technical solution.

[0015] Preferably, the prebaked anode binder accounts for 16-19 wt%.

[0016] Preferably, the prebaked anode further includes calcined petroleum coke; the calcined petroleum coke comprises: 21-26 wt% calcined coke with a particle size of 3-6 mm; 16-18 wt% calcined coke with a particle size of 3-1 mm; 18-25 wt% calcined coke with a particle size of 1-0 mm; and 36-40 wt% powder.

[0017] This invention provides an application of deoiled pitch in the preparation of prebaked anode binders. The deoiled pitch has a softening point of not less than 70℃, a coking value of not less than 30%, and a C / H atomic ratio of not less than 1.0. The modified deoiled pitch with the above parameters has a softening point of 100–105℃, a viscosity of 8–12 Pa·s at 140℃, a viscosity of 1.2–2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55–58%, and a C / H atomic ratio of ≥1.2. Compared to modified coal tar pitch, it is more environmentally friendly and has superior air oxidation resistance, carbon dioxide reactivity, and wettability. It can replace part of the modified coal tar pitch as a prebaked anode binder for the preparation of prebaked anodes. The performance of the prebaked anode meets current industry standards. Experimental results show that the polycyclic aromatic hydrocarbon content in the oil-based prebaked anode binder is 1870–2000 ppm, the air oxidation rate (coke reaction residue rate) is 88.56–89.05%, the carbon dioxide reactivity (coke reaction residue rate) is 93.23–94.04%, the permeability coefficient is 2.99–3.07, the flexural strength of the prebaked anode is 9.6–9.8 MPa, the carbon dioxide reaction residue rate is 96.1–97.1%, and the ash content is 0.22–0.28%. Detailed Implementation

[0018] This invention provides an application of deoiled bitumen in the preparation of prebaked anode binders;

[0019] The softening point of the deoiled bitumen is not lower than 70℃, the coking value is not less than 30%, and the C / H atomic ratio is not less than 1.0.

[0020] In the existing technology, deoiled bitumen is a low-value-added product, and most of it is used as fuel oil or in the fields of roads and waterproofing, resulting in low economic benefits. This invention modifies it and uses it as a prebaked anode binder in the carbon industry, thus expanding its application fields and application value.

[0021] In a specific embodiment of the present invention, the softening point of the deoiled asphalt is 79°C, the coking value is 35.6%, and the C / H atomic ratio is 1.08; or the softening point of the deoiled asphalt is 90°C, the coking value is 51%, and the C / H atomic ratio is 1.20.

[0022] This invention provides an oil-based prebaked anode binder, wherein the oil-based prebaked anode binder has a softening point of 100-105℃, a viscosity of 8-12 Pa·s at 140℃, a viscosity of 1.2-2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55-58%, and a C / H atomic ratio of ≥1.2.

[0023] The oil-based prebaked anode binder described in this invention is prepared by solvent extraction of deoiled bitumen obtained from atmospheric and vacuum distillation residue oil, followed by heat treatment at 300–500°C and 100–300 rpm for 5–15 hours.

[0024] This invention provides a prebaked anode binder, the raw materials of which include modified coal tar pitch and oil-based prebaked anode binder in a mass ratio of (7-9):(1-3); the oil-based prebaked anode binder has a softening point of 100-105℃, a viscosity of 8-12 Pa·s at 140℃, a viscosity of 1.2-2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55-58%, and a C / H atomic ratio of ≥1.2.

[0025] In this invention, the oil-based prebaked anode binder is prepared by heat-treating de-oiled bitumen obtained from atmospheric and vacuum distillation residue through solvent extraction, followed by stirring at 300–500°C and 100–300 rpm for 5–15 hours. Specifically, the heaviest component from atmospheric and vacuum distillation is the residue. The residue is fed into a solvent deasphalting unit and extracted with a solvent to obtain de-oiled bitumen and deasphalted oil. This invention uses de-oiled bitumen as raw material to prepare modified de-oiled bitumen, i.e., the oil-based prebaked anode binder. The softening point of the oil-based prebaked anode binder is 103–105°C, the coking value is 57.0–57.3%, the viscosity at 140°C is 10.8–11.85 Pa·s, the viscosity at 160°C is 1.3–1.705 Pa·s, and the C / H atomic ratio is 1.2–1.4. In a specific embodiment of the present invention, the oil-based prebaked anode binder has a softening point of 105℃, a coking value of 57.3%, an ash content of 0.7%, a viscosity of 11.85 Pa·s at 140℃, a viscosity of 1.715 Pa·s at 160℃, and a C / H atomic ratio of 1.29; or the oil-based prebaked anode binder has a softening point of 103℃, a coking value of 57.0%, an ash content of 0.9%, a viscosity of 10.8 Pa·s at 140℃, a viscosity of 1.3 Pa·s at 160℃, and a C / H atomic ratio of 1.27.

[0026] The modified coal tar pitch of this invention has a moisture content ≤5.0%, an ash content ≤0.3%, a coking value ≥54%, a softening point of 100-105℃, and a volatile matter content ≤56%. In a specific embodiment, the modified coal tar pitch has a moisture content of 0.10%, an ash content of 0.30%, a coking value of 56.87%, a softening point of 105.5℃, and a volatile matter content of 55.46%; or the modified coal tar pitch has a moisture content of 0.07%, an ash content of 0.11%, a coking value of 57.83%, a softening point of 106.5℃, and a volatile matter content of 55.20%.

[0027] In this invention, the mass ratio of the oil-based prebaked anode binder to the modified coal tar pitch is (1-3):(7-9); in specific embodiments, the mass ratio of the oil-based prebaked anode binder to the modified coal tar pitch is 3:7 or 1:9.

[0028] This invention provides a prebaked anode, comprising the prebaked anode binder described in the above-mentioned technical solution. The prebaked anode binder accounts for 16-19 wt% of the prebaked anode. The prebaked anode also includes 81-84% aggregate; the aggregate is calcined petroleum coke of different sizes, wherein the calcined petroleum coke of different sizes includes: 3-6 mm calcined coke content 21-26%; 3-1 mm calcined coke content 16-18%; 1-0 mm calcined coke content 18-25%; and powder 36-40%.

[0029] This invention tests the environmental performance of oil-based prebaked anode binders, and uses gas chromatography-mass spectrometry (GC-MS) to detect polycyclic aromatic hydrocarbons in the aforementioned oil-based prebaked anode binders.

[0030] The chemical reaction of the coke generated after carbonization of the above-mentioned oil-based prebaked anode binder is similar to that of aggregate petroleum coke, which can reduce the selective oxidation of the binder coke and the loss of coke aggregates, thereby improving the overall effective utilization rate of the prebaked anode. The low content of quinoline insolubles in the oil-based prebaked anode binder is conducive to the binder's infiltration into the petroleum coke and its carbon bridging effect, thus facilitating the performance of the binder.

[0031] This invention tests the air oxidation / carbon dioxide reactivity of oil-based prebaked anode binders:

[0032] A certain amount of oil-based prebaked anode binder was taken and loaded into the anode using the embedding method. In the crucible, place the crucible containing the sample. The crucible was filled with calcined petroleum coke smaller than 1 mm as a filling material and placed in a muffle furnace. The temperature was raised to 1000℃ and held for 2 hours. The prepared pitch coke was ground, and particles of 1-1.4 mm (carbonized particles of oil-based prebaked anode binder) were taken as raw materials for performance testing. These particles were placed in a ceramic boat of a certain size and placed in a tubular atmosphere furnace. The furnace was purged with N2 atmosphere and heated to 550℃ (CO2 reactivity is 1000℃) at a heating rate of 5℃ / min. After holding at this temperature for 30 minutes, the furnace was switched to air or CO2 atmosphere at a flow rate of 1 L / min and held for 4 hours. Then, the furnace was switched back to N2 atmosphere, cooled to room temperature, and the residual mass was weighed.

[0033] Coke reaction residue rate = (m2-m0) / (m1-m0)×100%

[0034] m0 - Mass of the porcelain ark, in grams;

[0035] m1 - Total mass of the ceramic ark and sample before firing, in g;

[0036] m2 - Total mass of the fired ceramic ark and residue, in grams.

[0037] This invention tests the wettability of oil-based prebaked anode binders:

[0038] Weigh a certain amount of aggregate coke (petroleum coke) of a specific particle size (1-0.5mm, 0.5-0.25mm) and place it into a stainless steel cylinder with a diameter of 20mm and a height of 100mm. After compacting it several times, weigh a certain amount of asphalt particles (oil-based prebaked anode binder) with a particle size of 1-2mm and add them to the top layer of the aggregate coke. Place the cylinder in the center of an oven and heat it according to the set heating rate. Maintain the temperature at 160℃ for 2 hours to allow the asphalt layer to disappear and the asphalt to be completely absorbed and penetrated into the aggregate coke. After cooling, remove the container, remove the base, pour out the unadhered aggregate, and weigh it.

[0039] W = (m⁴ - m³) / m³

[0040] W is the permeability coefficient; m4 is the total mass of petroleum coke used to bind the asphalt; m3 is the mass of the asphalt.

[0041] To further illustrate the present invention, the application of the deoiled bitumen provided by the present invention in the preparation of prebaked anode binders and the prebaked anodes are described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] The residue oil from the atmospheric and vacuum distillation unit was solvent-extracted to obtain de-oiled pitch (softening point 79℃, coking value 35.6%, C / H atomic ratio 1.08). This was then heat-treated in a high-temperature reactor at 310℃ and a stirring speed of 200 r / min for 14.5 h to obtain an oil-based prebaked anode binder (with the following specifications: softening point 103℃, coking value 57.0%, ash content 0.9%, viscosity at 140℃ 10.8 Pa·s, viscosity at 160℃ 1.3 Pa·s, C / H atomic ratio 1.27). This prebaked anode binder was then mixed uniformly with coal-based prebaked anode binder modified coal tar pitch (with the following specifications: moisture 0.10%, ash content 0.30%, coking value 56.87%, softening point 105.5℃, volatile matter 55.46%) at a ratio of 3:7 to obtain the prebaked anode binder.

[0044] Table 1. Performance differences of prebaked anode binders for coal-series and oil-series ... prebaked anode binders

[0045]

[0046] As shown in Table 1, the environmental performance, air oxidation performance, carbon dioxide reactivity, and wettability of the oil-based prebaked anode binder in this invention are all superior to those of the coal-based prebaked anode binder modified coal tar pitch.

[0047] In this invention, the modified coal tar pitch described above is used as the prebaked anode binder for control group 1.

[0048] In this invention, the prebaked anode binder from Example 1 and the prebaked anode binder from Control Group 1 are used as raw materials, accounting for 16%, and mixed with 84% calcined petroleum coke (of the calcined coke, 22wt% is calcined coke with a particle size of 3-6mm; 17wt% is calcined coke with a particle size of 3-1mm; 25wt% is calcined coke with a particle size of 1-0mm; and 36wt% is powder) to form a prebaked anode. The prebaked anode index is tested according to the industry standard for prebaked anodes used in aluminum electrolysis to determine the performance of the binder.

[0049] Table 2. Performance Evaluation of Prebaked Anodes (Industry Standard YS / T 285-2022)

[0050] Testing items TY-2 Technical Requirements Control group 1 Example 1 <![CDATA[True density / g / cm 3 > Not less than 2.03 2.071 2.071 resistivity / μΩ·m No more than 62 59.60 58.72 <![CDATA[Apparent density / g / cm 3 > Not less than 1.53 1.5900 1.5924 Pressure resistance / MPa Not less than 32 33.14 33.45 Flexural strength / MPa Not less than 8 9.2 9.8 Carbon dioxide reaction residue / % Not less than 80 95.0 96.1 Ash content / % No greater than 0.7 0.25 0.28 Coefficient of thermal expansion K <![CDATA[Not greater than 5.0*10 -6 > <![CDATA[4.8*10 -6 ]]> <![CDATA[4.8*10 -6 ]]>

[0051] As shown in Table 2, the oil-based prebaked anode binder prepared using the present invention can partially replace the current coal-based binder. After application performance evaluation, it meets the current industry standard requirements for prebaked anodes, and some indicators are superior to the prebaked anodes prepared with the coal-based binder of control group 1.

[0052] Example 2

[0053] The residue oil from the atmospheric and vacuum distillation unit was solvent-extracted to obtain de-oiled pitch (softening point 90℃, coking value 51%, C / H atomic ratio 1.20). This was then heat-treated in a high-temperature reactor at 400℃ and a stirring speed of 300 r / min for 5.5 h to obtain an oil-based prebaked anode binder (with the following specifications: softening point 105℃, coking value 57.3%, ash content 0.7%, viscosity at 140℃ 11.85 Pa·s, viscosity at 160℃ 1.715 Pa·s, C / H atomic ratio 1.29). This prebaked anode binder was then mixed uniformly with coal-based prebaked anode binder modified coal tar pitch (with the following specifications: moisture 0.07%, ash content 0.11%, coking value 57.83%, softening point 106.5℃, volatile matter 55.20%) at a ratio of 1:9 to obtain the prebaked anode binder.

[0054] Table 3. Performance differences of prebaked anode binders for coal-series and oil-series ... prebaked anode binders

[0055]

[0056] As shown in Table 3, the environmental performance, air oxidation performance, carbon dioxide reactivity, and wettability of the oil-based prebaked anode binder in this invention are all superior to those of the coal-based prebaked anode binder modified coal tar pitch.

[0057] In this invention, the modified coal tar pitch described above is used as the prebaked anode binder for control group 2.

[0058] In this invention, the prebaked anode binder from Example 2 and the prebaked anode binder from Control Group 2 are used as raw materials, accounting for 16%, and mixed with 84% calcined petroleum coke (of the calcined coke, 22wt% is calcined coke with a particle size of 3-6mm; 17wt% is calcined coke with a particle size of 3-1mm; 25wt% is calcined coke with a particle size of 1-0mm; and 36wt% is powder) to form a prebaked anode. The prebaked anode index is tested according to the industry standard for prebaked anodes used in aluminum electrolysis to determine the performance of the binder.

[0059] Table 4. Performance evaluation of the prebaked anode prepared in Example 2 (Industry Standard YS / T 285-2022)

[0060] Testing items TY-2 Technical Requirements Control group 2 Example 2 <![CDATA[True density / g / cm 3 > Not less than 2.03 2.070 2.070 resistivity / μΩ·m No more than 62 57.91 56.98 <![CDATA[Apparent density / g / cm 3 > Not less than 1.53 1.5935 1.5936 Pressure resistance / MPa Not less than 32 33.44 33.75 Flexural strength / MPa Not less than 8 9.3 9.6 Carbon dioxide reaction residue / % Not less than 80 96.0 97.1 Ash content / % No greater than 0.7 0.22 0.22 Coefficient of thermal expansion K <![CDATA[Not greater than 5.0*10 -6 > <![CDATA[4.9*10 -6 ]]> <![CDATA[4.9*10 -6 ]]>

[0061] As shown in Table 4, the oil-based prebaked anode binder prepared using the present invention can partially replace the current coal-based binder. After application performance evaluation, it meets the current industry standard requirements for prebaked anodes, and some indicators are superior to the prebaked anodes prepared with the coal-based binder of control group 2.

[0062] As can be seen from the above embodiments, this invention provides an application of deoiled bitumen in the preparation of prebaked anode binders; the deoiled bitumen has a softening point of not less than 70℃, a coking value of not less than 30%, and a C / H atomic ratio of not less than 1.0. The modified deoiled bitumen obtained after modification of the deoiled bitumen raw material has a softening point of 100–105℃, a viscosity of 8–12 Pa·s at 140℃, a viscosity of 1.2–2 Pa·s at 160℃, an ash content of ≤1.0%, a coking value of 55–58%, and a C / H atomic ratio of ≥1.2. Compared with modified coal tar pitch, the modified deoiled bitumen with the above parameters is more environmentally friendly and has excellent air oxidation resistance, carbon dioxide reactivity, and wettability. It can replace part of the modified coal tar pitch as a prebaked anode binder for the preparation of prebaked anodes. The performance of the prebaked anode meets current industry standards. Experimental results show that the polycyclic aromatic hydrocarbon content in the oil-based prebaked anode binder is 1870–2000 ppm, the air oxidation rate (coke reaction residue rate) is 88.56–89.05%, the carbon dioxide reactivity (coke reaction residue rate) is 93.23–94.04%, the permeability coefficient is 2.99–3.07, the flexural strength of the prebaked anode is 9.6–9.8 MPa, the carbon dioxide reaction residue rate is 96.1–97.1%, and the ash content is 0.22–0.28%.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A prebaked anode binder, characterized in that, The preparation raw materials include modified coal tar pitch and an oil-based pre-baked anode binder with a mass ratio of 7:3 or 9:1; The oil-based pre-baked anode binder is prepared by heat-treating the de-oiled asphalt obtained by solvent extraction of the residue oil obtained from atmospheric and vacuum distillation at 300 - 500 °C with stirring at 100 - 300 rpm for 5 - 15 h; the softening point of the de-oiled asphalt is not lower than 70 °C, the coking value is not less than 30%, and the C / H atomic ratio is not less than 1.0; The softening point of the oil-based pre-baked anode binder is 103 - 105 °C, the coking value is 57.0 - 57.3%, the viscosity at 140 °C is 10.8 - 11.85 Pa·s, the viscosity at 160 °C is 1.3 - 1.705 Pa·s, the C / H atomic ratio is 1.2 - 1.4, and the ash content is ≤1.0%; In the modified coal tar pitch, the water content is ≤5.0%, the ash content is ≤0.3%, the coking value is ≥54%, the softening point is 100 - 110 °C, and the volatile content is ≤56%.

2. A pre-baked anode, comprising the pre-baked anode binder as described in claim 1.

3. The pre-baked anode according to claim 2, wherein The proportion of the pre-baked anode binder is 16 - 19 wt%.

4. The pre-baked anode according to claim 2, wherein The pre-baked anode further comprises calcined petroleum coke; the calcined petroleum coke includes: 21 - 26 wt% of calcined coke with a particle size of 3 - 6 mm; 16 - 18 wt% of calcined coke with a particle size of 3 - 1 mm; 18 - 25 wt% of calcined coke with a particle size of 1 - 0 mm, and 36 - 40 wt% of powder.

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