Low-carbon-emission coal-based composite liquid fuel and preparation method thereof

Abstract

The present application belongs to the technical field of coal-based liquid fuel, and particularly relates to a coal-based composite liquid fuel with low carbon emission and a preparation method thereof, which comprises the following raw materials in parts by weight: coal direct liquefaction oil 40-70 parts, biomass-derived oil 15-35 parts, micro-mineral powder 5-15 parts, composite surfactant 3-8 parts, co-surfactant 1-3 parts, carbon fixation agent 2-10 parts, and cetane number improver 0.5-2 parts; the micro-mineral powder, the biomass-derived oil and the coal direct liquefaction oil are subjected to multi-element blending and micro-emulsification compounding; based on hydrogen supply-hydrogenation synergy and micro-explosion combustion mechanism, the micro-emulsification system is used to significantly improve fuel atomization and combustion efficiency; through the introduction of the carbon fixation component and the biomass-derived oil in the formula, the carbon emission is reduced from the raw material end to the combustion end; the raw materials have strong adaptability; and the prepared composite liquid fuel can be stored stably for a long time.

Description

Technical Field

[0001] This invention belongs to the field of coal-based liquid fuel technology, and particularly relates to a low-carbon emission coal-based composite liquid fuel and its preparation method. Background Technology

[0002] With the continuous growth of global energy demand and the increasing pressure to reduce carbon emissions, the development of clean and low-carbon alternative fuels has become a research hotspot in the energy sector. my country's resource endowment of "abundant coal, scarce oil, and limited gas" determines the strategic importance of coal-based liquid fuels in ensuring national energy security. However, traditional direct and indirect coal liquefaction technologies suffer from significant drawbacks such as long process routes, high investment costs, and large carbon emissions throughout their life cycle, facing severe challenges to sustainable development under the "dual carbon" goal. Although many studies have improved the carbon footprint of coal-based fuels to some extent by introducing biomass co-liquefaction, green hydrogen supplementation, and carbon capture technologies, significant shortcomings remain in raw material compatibility, product stability, and process carbon emission intensity control. Furthermore, traditional coal-based fuels often lack functional components that contribute to complete combustion and reduced pollutant emissions, making it difficult for their exhaust emissions in applications such as internal combustion engines to meet increasingly stringent environmental regulations.

[0003] Therefore, developing a new type of coal-based composite liquid fuel with widely available raw materials, low-carbon production process, clean and environmentally friendly products, and strong stability is a key direction for promoting the green transformation of coal-based fuels and realizing the low-carbon utilization of high-carbon energy. Summary of the Invention

[0004] To address the above issues, this invention provides a low-carbon emission coal-based composite liquid fuel and its preparation method. It involves multi-component blending and microemulsification of micromineral powder, biomass-derived oil, and direct coal liquefaction oil. Based on a hydrogen supply-hydrogenation synergy and micro-explosion combustion mechanism, the microemulsification system significantly improves fuel atomization and combustion efficiency. By introducing carbon-fixing components and biomass-derived oil into the formulation, it achieves a reduction in carbon emissions across the entire chain from raw material to combustion. The raw materials used are highly adaptable, and the prepared composite liquid fuel can be stored stably for a long period. This solves the problems of high carbon emissions, low product combustion efficiency, and large emissions of exhaust pollutants in existing coal-based fuel production processes.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a low-carbon emission coal-based composite liquid fuel and its preparation method, comprising the following raw materials in parts by weight: 40-70 parts of direct coal liquefaction oil, 15-35 parts of biomass-derived oil, 5-15 parts of micro mineral powder, 3-8 parts of composite surfactant, 1-3 parts of co-surfactant, 2-10 parts of carbon fixation agent, and 0.5-2 parts of cetane number improver.

[0006] Furthermore, the direct coal liquefaction oil is an intermediate distillate oil with a distillation range of 180-420℃, generated by hydrogenation of coal under the action of an iron-based catalyst at a temperature of 420-460℃ and a pressure of 15-20MPa, and its aromatic content is not less than 40% (mass fraction).

[0007] Furthermore, the biomass-derived oil is selected from any one or more combinations of straw rapid pyrolysis oil, waste oil catalytic cracking oil, and sawdust hydrothermal liquefaction oil.

[0008] Furthermore, the micro-mineral powder is selected from any one of lignite powder, petroleum coke powder, and carbon black powder with a particle size D50 of 0.5-5μm.

[0009] Furthermore, the composite surfactant is a mixture of a nonionic surfactant and anionic surfactant with an HLB value between 6 and 10. The nonionic surfactant is selected from any one of sorbitan monooleate, castor oil polyoxyethylene ether, and fatty alcohol polyoxyethylene ether. The anionic surfactant is selected from any one of sodium dodecylbenzene sulfonate, sodium petroleum sulfonate, and sodium oleate. The mass ratio of the nonionic surfactant to the anionic surfactant is 3:1 to 5:1.

[0010] Furthermore, the co-surfactant is selected from any one of n-butanol, isopropanol, and n-pentanol.

[0011] Furthermore, the carbon-fixing agent is selected from any one or a combination of nano-calcium carbonate and nano-magnesium oxide with an average particle size of 10-100 nm.

[0012] Furthermore, the cetane number improver is selected from either isooctyl nitrate or amyl nitrate.

[0013] This invention also provides a method for preparing a low-carbon emission coal-based composite liquid fuel, specifically including the following steps: Step 1: Weigh 3-8 parts of the compound surfactant and 1-3 parts of the co-surfactant, and stir and mix them at 40-60℃ for 15 minutes to obtain the surfactant premix. Step 2: Weigh 15-35 parts of biomass-derived oil, preheat to 50-70℃, and slowly add the surfactant premix obtained in Step 1 to the biomass-derived oil while stirring at a speed of 500-800 rpm. Continue stirring for 30 minutes to obtain a biomass oil emulsion. Step 3: Weigh 40-70 parts of direct coal liquefaction oil, preheat to 60-80℃, and inject the biomass oil emulsion obtained in Step 2 into the direct coal liquefaction oil in a thin stream under high shear conditions with a stirring speed of 1000-1500 rpm. After injection, continue high shear stirring for 45 minutes to obtain an oil-in-oil crude emulsion. Step 4: Cool the oil-in-oil crude emulsion obtained in Step 3 to 25-35℃, and add 5-15 parts of micro mineral powder and 2-10 parts of carbon fixative in sequence under the condition of stirring speed of 300-500 rpm, and disperse it fully for 30 minutes to obtain a solid emulsion. Step 5: Transfer the solid emulsion obtained in Step 4 to a high-pressure microfluidic homogenizer and cycle it 3-5 times under an operating pressure of 80-120MPa to obtain a microemulsion fuel mother liquor with an average droplet size of 200-800nm. Step 6: Add 0.5-2 parts of cetane number improver to the microemulsion fuel mother liquor obtained in Step 5, mix at a stirring rate of 200-400 rpm for 15 min, let stand to defoam, and obtain low carbon emission coal-based composite liquid fuel.

[0014] The beneficial effects achieved by this invention are as follows: 1. The "oil-in-oil" microemulsion system constructed in this invention disperses biomass-derived oil in the form of nano-sized droplets within direct coal liquefaction oil. During combustion, the preferential gasification of low-boiling-point biomass components triggers a "micro-explosion" effect, atomizing the fuel droplets a second time and significantly increasing the contact area with air. This results in a combustion efficiency increase of over 15% compared to traditional coal-based diesel, while simultaneously reducing particulate matter (PM) and nitrogen oxide (NOx) emissions by over 20% and 10%, respectively. 2. The nano-carbon-fixing agent introduced into the fuel formulation can interact with the high-temperature zone of the combustion chamber. Carbonation occurs, capturing and fixing approximately 3%-8% of the carbon emissions from the combustion process in situ. Combined with the carbon-neutral characteristics of biomass-derived oil feedstock, the carbon emissions of this fuel throughout its entire life cycle are reduced by 25%-35% compared to traditional coal-to-liquid diesel, achieving full-chain carbon reduction from feedstock to combustion. 3. The micro-mineral powder component in the formula plays a role in combustion assistance and catalytic oxidation during combustion, which can promote the complete combustion of residual carbon and effectively reduce carbon monoxide in the exhaust gas. The emission concentrations of unburned hydrocarbons (HC); 4. Through the optimized composite surfactant system and high-pressure micro-jet homogenization process, thermodynamically stable nanoscale microemulsion droplets (average particle size 200-800nm) are formed, which effectively prevents fuel stratification and sedimentation. After 90 days of standing, the kinematic viscosity change rate is less than 5%, ensuring the stability of the product during long-term storage and transportation. 5. The technical solution of this invention is compatible with various biomass-derived oil feedstocks such as straw rapid pyrolysis oil, waste oil catalytic cracking oil, and sawdust hydrothermal liquefaction oil. It also has good tolerance for the aromatic content and distillation range of coal direct liquefaction oil, providing flexibility for large-scale industrial production and multiple feedstock routes. Attached Figure Description

[0015] The accompanying drawings are provided to further understand the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the invention and do not constitute a limitation thereof.

[0016] Figure 1 The microemulsion droplet size distribution diagrams are shown for the coal-based composite liquid fuels prepared in Example 1 and Comparative Examples 1-2. Figure 2 The results of stability studies on the coal-based composite liquid fuels prepared in Examples 1-3 are shown. Figure 3 The combustion exhaust gas emission test results of the coal-based composite liquid fuel prepared in Example 1; Figure 4 The results of the life cycle carbon emission analysis of the coal-based composite liquid fuels prepared in Example 1 and Comparative Examples 1-2 are shown. Figure 5 The results of the physicochemical performance tests of the coal-based composite liquid fuels prepared in Examples 1-4 are shown. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0019] Example 1: This example provides a low-carbon emission coal-based composite liquid fuel, comprising an upper substrate and a lower substrate. The low-carbon emission coal-based composite liquid fuel comprises the following raw materials in parts by weight: 60 parts of direct coal liquefaction oil, 25 parts of straw rapid pyrolysis oil, 10 parts of lignite powder (D50=1.5μm), 5 parts of composite surfactant, 2 parts of n-butanol, 6 parts of nano-calcium carbonate (average particle size 50nm), and 1 part of isooctyl nitrate.

[0020] The composite surfactant is composed of sorbitan monooleate and sodium dodecylbenzenesulfonate in a mass ratio of 4:1.

[0021] This embodiment also provides a method for preparing a low-carbon emission coal-based composite liquid fuel, which specifically includes the following steps: Step 1: Weigh 5 parts of the composite surfactant and 2 parts of n-butanol, stir and mix at 50°C for 15 minutes to obtain the surfactant premix; Step 2: Weigh 25 portions of straw rapid pyrolysis oil, preheat to 60°C, and slowly add the surfactant premix obtained in Step 1 to the straw rapid pyrolysis oil while stirring at a stirring rate of 650 rpm. Continue stirring for 30 minutes to obtain a biomass oil emulsion. Step 3: Weigh 60 parts of direct coal liquefaction oil, preheat to 70℃, and inject the biomass oil emulsion obtained in Step 2 into the direct coal liquefaction oil in a thin stream under high shear conditions with a stirring speed of 1200 rpm. After the injection is completed, continue high shear stirring for 45 minutes to obtain an oil-in-oil crude emulsion. Step 4: Cool the oil-in-oil crude emulsion obtained in Step 3 to 30°C, and add 10 parts of lignite powder and 6 parts of nano-calcium carbonate in sequence under a stirring speed of 400 rpm, and disperse fully for 30 min to obtain a solid emulsion. Step 5: Transfer the solid emulsion obtained in Step 4 to a high-pressure microfluidic homogenizer and cycle it 4 times under an operating pressure of 100 MPa to obtain a microemulsion fuel mother liquor with an average droplet size of 350 nm. Step 6: Add 1 part of isooctyl nitrate to the microemulsion fuel mother liquor obtained in Step 5, mix at a stirring rate of 300 rpm for 15 min, let stand to defoam, and obtain low-carbon emission coal-based composite liquid fuel.

[0022] Example 2: This example provides a low-carbon emission coal-based composite liquid fuel, which includes the following raw materials by weight: 50 parts of direct coal liquefaction oil, 30 parts of waste oil catalytic cracking oil, 8 parts of petroleum coke powder (D50=3μm), 6 parts of composite surfactant, 2.5 parts of isopropanol, 5 parts of nano magnesium oxide (average particle size 80nm), and 1.5 parts of amyl nitrate.

[0023] The composite surfactant is prepared by compounding castor oil polyoxyethylene ether and sodium petroleum sulfonate in a mass ratio of 3:1.

[0024] The preparation method of this embodiment is the same as that of Example 1, except that in step 2, the straw rapid pyrolysis oil is replaced with waste oil catalytic cracking oil and the preheating temperature is adjusted to 65°C; in step 3, the preheating temperature of coal direct liquefaction oil is adjusted to 75°C; in step 4, the micro mineral powder and carbon fixative are replaced with petroleum coke powder and nano magnesium oxide, respectively; and in step 6, the cetane number improver is replaced with amyl nitrate.

[0025] Example 3: This example provides a low-carbon emission coal-based composite liquid fuel, which includes the following raw materials in parts by weight: 65 parts of direct coal liquefaction oil, 18 parts of wood chip hydrothermal liquefaction oil, 12 parts of carbon black powder (D50=0.8μm), 4 parts of composite surfactant, 1 part of n-pentanol, 8 parts of a mixture of nano calcium carbonate and nano magnesium oxide (mass ratio 1:1, average particle size 60nm), and 0.8 parts of isooctyl nitrate.

[0026] The composite surfactant is composed of fatty alcohol polyoxyethylene ether and sodium oleate in a mass ratio of 5:1.

[0027] The preparation method of this embodiment is the same as that of Example 1, except that in step 2, the straw rapid pyrolysis oil is replaced with wood chip hydrothermal liquefaction oil and the preheating temperature is adjusted to 55°C; in step 4, the micro mineral powder and carbon fixative are replaced with carbon black powder and a mixture of nano calcium carbonate and nano magnesium oxide, respectively.

[0028] Example 4: This example provides a low-carbon emission coal-based composite liquid fuel, which includes the following raw materials in parts by weight: 45 parts of direct coal liquefaction oil, 35 parts of a combination of straw rapid pyrolysis oil and waste oil catalytic cracking oil (mass ratio 2:1), 5 parts of lignite powder (D50=2μm), 7 parts of composite surfactant, 3 parts of n-butanol, 3 parts of nano calcium carbonate (average particle size 30nm), and 1.2 parts of isooctyl nitrate.

[0029] The composite surfactant is prepared by compounding sorbitan monooleate and sodium dodecylbenzenesulfonate in a mass ratio of 4.5:1. The preparation method of this embodiment is the same as that of Example 1, except that in step 2, the straw rapid pyrolysis oil is replaced with a composition of straw rapid pyrolysis oil and waste oil catalytic cracking oil.

[0030] Comparative Example 1: Commercially available direct coal liquefaction diesel (without any added biomass components or functional additives).

[0031] Comparative Example 2: The formulation and preparation method of Example 1 are the same, except that no composite surfactant or co-surfactant is added, and the high-pressure microjet homogenization treatment in step 5 is not performed, resulting in a non-microemulsified physical mixed fuel.

[0032] Microemulsion droplet size testing The droplet size distribution of fuel samples prepared in Example 1 and Comparative Examples 1-2 was determined using a nanoparticle size and zeta potential analyzer. The results are shown in the figure. Figure 1 .

[0033] Storage stability was investigated by placing the coal-based composite liquid fuels prepared in Examples 1-3 in a 25°C constant temperature chamber for 90 days. On days 7, 14, 30, 60, and 90, the layering and sedimentation were visually observed, and samples were taken to measure the rate of change in kinematic viscosity. The results are shown in [Figure number missing]. Figure 2 .

[0034] For combustion exhaust emission testing, the coal-based composite liquid fuel prepared in Example 1 and the commercially available coal direct liquefaction diesel from Comparative Example 1 were subjected to steady-state emission tests on a four-cylinder direct injection diesel engine bench. The emission concentrations of CO, HC, NOx, and particulate matter (PM) in the exhaust gases were measured. The results are shown in [Figure 1]. Figure 3 .

[0035] The life-cycle carbon emission analysis used the GREET model to assess the greenhouse gas emissions of the fuels in Example 1 and Comparative Examples 1-2 from "raw material acquisition - fuel production - fuel transportation - fuel combustion". The results are shown in [Figure 1]. Figure 4 .

[0036] The physicochemical properties were tested according to GB25199-2017 "B5 Diesel" standard. Key physicochemical properties such as kinematic viscosity, flash point, cetane number, density, and calorific value were tested on the coal-based composite liquid fuels prepared in Examples 1-4. The results are shown in [Figure 1]. Figure 5 .

[0037] Results Analysis Figure 1 The results show that the microemulsion fuel droplets prepared in Example 1 have a concentrated particle size around 350 nm and exhibit a narrow single-peak distribution, indicating that the microemulsion system is uniform and stable; Comparative Example 2, due to the lack of microemulsion treatment, exhibits a wide peak distribution at the micrometer level and has poor stability.

[0038] Figure 2 The results showed that the fuels in Examples 1-3 did not exhibit significant stratification or precipitation after 90 days of standing, and the kinematic viscosity change rate was less than 5%, demonstrating excellent long-term storage stability.

[0039] Figure 3 The results showed that, compared with the commercially available coal-to-diesel fuel in Comparative Example 1, the fuel in Example 1 reduced CO emissions by 35%, HC emissions by 28%, NOx emissions by 12%, and PM emissions by 22%, demonstrating a significant clean combustion effect.

[0040] Figure 4 The results show that the carbon emissions of the fuel in Example 1 were reduced by about 31% compared with Comparative Example 1 and by about 18% compared with Comparative Example 2, which confirms the significant advantages of the technical solution of the present invention in carbon emission reduction.

[0041] Figure 5The results show that all the physicochemical properties of the fuels in Examples 1-4 meet or exceed the requirements of national standards, with cetane numbers reaching 48-52 and flash points >60℃, fully meeting the requirements of compression ignition engines for fuel safety and power.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-carbon emission coal-based composite liquid fuel, characterized in that, The raw materials include the following parts by weight: 40-70 parts of direct coal liquefaction oil, 15-35 parts of biomass-derived oil, 5-15 parts of micro mineral powder, 3-8 parts of compound surfactant, 1-3 parts of co-surfactant, 2-10 parts of carbon fixation agent, and 0.5-2 parts of cetane number improver.

2. The low-carbon emission coal-based composite liquid fuel according to claim 1, characterized in that, The coal direct liquefaction oil is an intermediate distillate oil with a distillation range of 180-420℃, generated by hydrogenation of coal under the action of an iron-based catalyst at a temperature of 420-460℃ and a pressure of 15-20MPa, and its aromatic content is not less than 40%. The biomass-derived oil is straw rapid pyrolysis oil.

3. The low-carbon emission coal-based composite liquid fuel according to claim 2, characterized in that, The composite surfactant is a mixture of a nonionic surfactant and anionic surfactant with an HLB value between 6 and 10. The mass ratio of the nonionic surfactant to the anionic surfactant is 3:1 to 5:

1. The nonionic surfactant is sorbitan monooleate, and the anionic surfactant is sodium dodecylbenzenesulfonate.

4. The low-carbon emission coal-based composite liquid fuel according to claim 3, characterized in that, The micro-mineral powder is lignite powder with a particle size D50 of 0.5-5μm, and the carbon fixation agent is nano-calcium carbonate with an average particle size of 10-100nm.

5. A low-carbon emission coal-based composite liquid fuel according to claim 4, characterized in that, The coal-based composite liquid fuel is an oil-in-oil microemulsion fuel, with biomass-derived oil as the dispersed phase and direct coal liquefaction oil as the continuous phase, and an average droplet size of 200-800 nm.

6. A method for preparing a low-carbon emission coal-based composite liquid fuel according to any one of claims 1 to 5, comprising the following steps: Step 1: Weigh 3-8 parts of the compound surfactant and 1-3 parts of the co-surfactant, and stir and mix them at 40-60℃ to obtain the surfactant premix. Step 2: Weigh 15-35 parts of biomass-derived oil, preheat to 50-70℃, add the surfactant premix obtained in Step 1 to the biomass-derived oil under stirring, and continue stirring to obtain biomass oil emulsion. Step 3: Weigh 40-70 parts of direct coal liquefaction oil, preheat to 60-80℃, and inject the biomass oil emulsion obtained in Step 2 into the direct coal liquefaction oil under high shear conditions. Continue high shear stirring to obtain an oil-in-oil crude emulsion. Step 4: Cool the oil-in-oil crude emulsion obtained in Step 3 to 25-35℃, and under stirring conditions, add 5-15 parts of micro mineral powder and 2-10 parts of carbon fixative in sequence, and disperse them fully to obtain a solid emulsion. Step 5: The solid-containing emulsion obtained in Step 4 is subjected to high-pressure micro-jet homogenization to obtain microemulsion fuel mother liquor; Step 6: Add 0.5-2 parts of cetane number improver to the microemulsion fuel mother liquor obtained in Step 5, stir and mix, let stand to defoam, and obtain low carbon emission coal-based composite liquid fuel.

7. The method for preparing a low-carbon emission coal-based composite liquid fuel according to claim 6, characterized in that, In step 2, the stirring rate is 500-800 rpm and the stirring time is 30 min; in step 3, the high shear stirring rate is 1000-1500 rpm and the stirring time is 45 min, and the biomass oil emulsion is injected in a thin stream; in step 4, the stirring rate is 300-500 rpm and the dispersion time is 30 min.

8. The method for preparing a low-carbon emission coal-based composite liquid fuel according to claim 7, characterized in that, In step 5, the operating pressure of the high-pressure micro-jet homogenization treatment is 80-120 MPa, and the treatment is repeated 3-5 times. The average droplet size of the resulting microemulsion fuel mother liquor is 200-800 nm. The resulting low-carbon emission coal-based composite liquid fuel has a cetane number of 48-52, a flash point >60℃, and a kinematic viscosity change rate of less than 5% after standing at 25℃ for 90 days.

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