Method and system for preparing sustainable aviation kerosene through methanol based on biomass gasification

Abstract

The invention relates to the technical field of biomass energy conversion, in particular to a method and system for preparing sustainable aviation kerosene through methanol based on biomass gasification. The method sequentially comprises the steps of biomass gasification, purification and proportion adjustment, methanol synthesis, methanol-to-olefin conversion, oligomerization reaction and hydrofining. The selectivity of a target component is effectively improved by regulating and controlling the H2 / CO molar ratio to 2.0-2.2 and realizing multi-section conversion and heat energy gradient recovery under middle and high pressure. The condensation point of the finished product can reach-48 DEG C, the aromatic hydrocarbon mass fraction is as low as 0.22%, and the aviation fuel standard requirements are met. The method has the advantages of being high in carbon utilization rate, excellent in product quality, low in energy consumption, suitable for large-scale operation and the like, and is suitable for green manufacturing of sustainable aviation fuel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomass energy conversion, and particularly relates to a method and system for preparing sustainable aviation kerosene based on biomass gasification and methanol. BACKGROUND

[0002] Aviation kerosene is the main fuel in the field of civil aviation and military aviation, and its production has long relied on fossil oil resources. Fossil-based aviation kerosene will emit a large amount of carbon dioxide and other greenhouse gases during production and combustion, which will have an adverse impact on global climate change and the ecological environment.

[0003] The existing SAF preparation routes mainly include: Hydroprocessing ester and fatty acid route (HEFA): using animal and vegetable oils as raw materials, aviation fuel is prepared through hydrogenation and isomerization, etc. The process is mature and the product quality is stable, but the raw material sources are limited and the price fluctuates greatly, which is difficult to meet the large-scale supply demand.

[0004] Gasification-Fischer-Tropsch synthesis route (F-T): coal, biomass or municipal solid waste is gasified to obtain synthesis gas, which is synthesized into liquid fuel by Fischer-Tropsch synthesis. The raw material has a wide range of applications, but the Fischer-Tropsch synthesis product has a wide distribution, the aviation fuel yield is low, the carbon conversion efficiency is insufficient, and the proportion of byproduct heavy components is high, which requires additional hydrogenation cracking treatment, increasing energy consumption and cost.

[0005] Alcohol-to-jet route (ATJ): ethanol is prepared by biological fermentation, and then aviation fuel is prepared through dehydration, oligomerization and hydrogenation, etc. This method has lower carbon emissions, but it is still in the pilot stage and has not been commercialized on a large scale. The process is long and the energy consumption is high.

[0006] In the above technical routes, HEFA is limited by the availability and cost of oil-based raw materials; F-T can use biomass raw materials, but the aviation fuel yield and carbon efficiency are low; ATJ has certain environmental advantages, but the economic efficiency and scalability are insufficient. Especially in the F-T route, the complex reaction conditions, high byproduct yield and excessive processing steps seriously restrict the overall economic efficiency and carbon emission reduction potential.

[0007] Therefore, there is an urgent need for a sustainable aviation kerosene production method and supporting system that can use widely available biomass as raw material, combined with efficient synthesis gas purification, methanol synthesis, methanol-to-light olefins, oligomerization and hydrogenation refining, etc. to realize the integration and optimization of the whole process, significantly improve the carbon conversion rate and target fraction yield, reduce the unit energy consumption and carbon emissions, and take into account the resource utilization of byproducts, to meet the future large-scale, low-carbon, safe and sustainable supply demand of aviation fuel. SUMMARY

[0008] To achieve the above object, the technical scheme is as follows: A method for preparing sustainable aviation kerosene from biomass gasification via methanol, comprising: S1, generating synthesis gas from biomass gasification; S2, purifying the synthesis gas and adjusting the molar ratio of H2 / CO to 2.0-2.2; S3, converting the synthesis gas in a methanol synthesis and rectification unit and obtaining a methanol product; S4, converting the methanol into a low-carbon olefin stream mainly composed of ethylene and propylene under the action of a molecular sieve catalyst at 400-500°C, and the total molar selectivity of ethylene and propylene is not less than 80%; S5, oligomerizing the low-carbon olefins in a fixed-bed series oligomerization reactor at 5.0-7.0 MPa, heat removal units are arranged between the beds to remove heat and control temperature, generating C8-C16 aviation kerosene precursors, and the unreacted olefins are recycled to the reactor inlet through a circulating gas compressor; S6, hydrofining the aviation kerosene precursors to obtain sustainable aviation kerosene.

[0009] Further, the biomass in step S1 is one or more of rice straw, wheat straw, corn straw, bamboo, forestry waste or municipal dry garbage; The biomass gasification unit is one of fixed bed, gas flow bed or fluidized bed type, and is operated at a pressure of 3.0-6.0 MPa.

[0010] Further, in step S2, low-temperature methanol washing is used to remove acid gases from the converted and cooled synthesis gas, and the volume fraction of H2S at the purification outlet is not higher than 1 ppm, and the volume fraction of CO2 is not higher than 0.5%, so as to meet the feed cleanliness and composition requirements of the downstream reaction.

[0011] Further, the methanol synthesis in step S3 is carried out on a Cu-Zn-Al type catalyst at 220-260°C; the obtained crude methanol is purified by rectification, and the mass fraction of the obtained methanol is not less than 99.85%.

[0012] Further, the operating temperature of step S4 is 450°C.

[0013] Further, the fixed-bed series oligomerization reactor in step S5 includes at least two series beds, and a steam generator is arranged between adjacent beds to remove reaction heat and inhibit hot spots and coking, thereby improving the selectivity to C8-C16 fraction.

[0014] Further, the hydrofining in step S6 is carried out under the condition that the volume fraction of hydrogen is not less than 90%; the freezing point of the obtained sustainable aviation kerosene is not higher than -40°C, and the mass fraction of aromatic hydrocarbons is not higher than 0.5%.

[0015] The application further provides a system for preparing sustainable aviation kerosene based on biomass gasification and methanol, comprising a biomass gasification unit, a purification and ratio adjustment unit, a methanol synthesis and rectification unit, a methanol to olefin conversion and separation unit, an oligomerization reactor and a hydrofining unit connected in sequence. The oligomerization reactor is connected to a recycle gas compressor for recycling unreacted olefins from the oligomerization reactor to the inlet of the reactor. The purification and ratio adjustment unit is configured to control the molar ratio of H2 / CO to be 2.0-2.2. The oligomerization reactor is a fixed-bed series structure with a pressure of 5.0-7.0 MPa, and a heat exchange unit is arranged between the beds to remove heat and control temperature.

[0016] Further, the biomass gasification unit is one of a fixed-bed, an entrained-flow bed or a fluidized bed, and is operated at a pressure of 3.0-6.0 MPa, and a raw material pretreatment device is arranged to adapt to biomass raw materials with different forms and water contents.

[0017] Further, the purification and ratio adjustment unit comprises a shift cooling device and a low-temperature methanol washing device, and is provided with an online detection and control assembly, so that the volume fraction of H2S at the outlet of the purification unit is not higher than 1 ppm.

[0018] Compared with the prior art, the application has the following beneficial effects: (1) Efficient control of syngas ratio improves the quality of intermediate products: By arranging an H2 / CO molar ratio adjustment device, the hydrogen-carbon ratio in the gasification gas is adjusted to an ideal range, effectively improving the reactivity of the syngas.

[0019] (2) Continuous conversion chain is built, and the controllability is high: a series process of "methanol to low-carbon olefins + directional oligomerization + selective hydrogenation" is built, which ensures the conversion rate, strengthens the path control of light feedstocks to target middle distillates, effectively avoids the accumulation of by-products, and improves the process convergence and product consistency.

[0020] (3) High selectivity of ethylene / propylene and excellent oligomerization efficiency: By accurately controlling the reaction temperature of the methanol to olefins (MTO) reaction, the molar selectivity of ethylene and propylene reaches 85.1%, which is significantly improved compared with the scheme with a lower reaction temperature zone, providing ideal raw material composition for the subsequent oligomerization reactor, and the overall olefin utilization efficiency is higher.

[0021] (4) Concentrated distillate distribution and high-quality terminal oil: The oligomerization section adopts a multi-stage fixed-bed and heat exchange temperature adjustment structure to remove reaction heat and adjust chain length distribution, and the carbon-based selectivity of the final middle distillate C8-C16 can reach 72%. The obtained product has a condensation point as low as -48℃ and an aromatic hydrocarbon mass fraction of 0.22% after hydrogenation, which ensures the low-temperature fluidity and thermal stability of the aviation kerosene product.

[0022] (5) High system integration, energy efficiency and resource utilization efficiency are improved: the system sets a circulating gas compressor for recycling unreacted olefins, and adjusts the heat load of the reactor through the inter-bed heat exchange unit, so as to realize the coupling of stable reactor discharge and heat exchange.

[0023] (6) The green path is clear, and it has industrial application feasibility: the present application uses renewable biomass as a carbon source, combines gasification and C1 conversion route to realize the directional preparation of middle distillate, does not need to purchase fossil hydrogen, and optimally uses endogenous hydrogen obtained by syngas shift and separation for ratio adjustment, and the product can be directly used as aviation fuel, which meets the low-carbon, green and sustainable development trend. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a process flow chart of the method of the present application; Figure 2 is a structural schematic diagram of the system of the present application; Figure 3 is a comparison chart of main performance indicators; Figure 4 is a trend chart of ethylene + propylene selectivity with methanol to olefins (MTO) temperature; Figure 5 is a comparison schematic diagram of oligomerization reactor structures; Figure 6 is a comparison chart of product quality indicators meeting standards. DETAILED DESCRIPTION

[0025] In order to more clearly illustrate the technical solutions of the present application, the present application will be further described in detail below in combination with specific embodiments. It should be understood that the following examples are only used to illustrate the present application, and not to limit the protection scope of the present application.

[0026] Part of the term explanation in the example: WHSV (mass air speed): the mass of the reactant processed per hour per unit mass of catalyst; GHSV (gas volume air speed): the volume of the gas processed per hour at standard conditions divided by the volume of the catalyst; LHSV (liquid volume air speed): the volume of the liquid processed per hour per unit volume of catalyst; the total molar selectivity of ethylene and propylene: the sum of the moles of ethylene and propylene in the reaction product accounts for the percentage of the total number of moles of organic products: (moles of ethylene + moles of propylene) ÷ total moles of organic products × 100%; C8-C16 selectivity: the sum of the moles of hydrocarbons with carbon number from 8 to 16 (mainly middle distillate olefins and alkanes) in the product accounts for the percentage of the total number of moles of all organic products: (total moles of C8-C16 hydrocarbons) ÷ total moles of organic products × 100% Example 1 The present example provides a method for preparing sustainable aviation kerosene, which specifically comprises: Raw material treatment: Corn stalks were selected as the biomass raw material. After unloading and storage, the raw material was subjected to magnetic separation to remove metal, sorting to remove foreign matter, screening and crushing, and the particle size was 5-20 mm; hot air or low-temperature belt drying was used, and the dry basis moisture content was 9.6%; in order to ensure continuous and stable feeding, medium-intensity granulation was implemented, and the bulk density was 0.50-0.55 tons per cubic meter; the treated biomass was fed into the biomass gasification unit through a sealed screw feeder and a lock hopper system, and dust removal and inert gas insulation were configured during the conveying process.

[0027] S1, Biomass gasification to generate synthesis gas: A fluidized bed gasifier was used, with a pressure of 4.5 MPa and a temperature of 850-900℃. The synthesis gas (dry basis volume fraction): H2 34-36%, CO 43-45%, CO2 15-17%, CH4 1-2%, H2S 20-50 ppm. After cyclone separation and ceramic filtration, it was sent to the subsequent section.

[0028] S2, Purification and molar ratio adjustment: The synthesis gas was first cooled to about 40℃ by shift conversion, and then reduced to the operating temperature of the low-temperature methanol wash by heat exchange and refrigeration, and then entered the low-temperature methanol wash device to remove acid gas. The actual measurement at the purification outlet: H2S 0.4 ppm, CO2 0.4%; in the purification and adjustment unit, H2 / CO was adjusted to 2.1 by shift conversion, separation and hydrogen addition, and the dew point of the purified gas was -22℃.

[0029] S3, Methanol synthesis and purification: Methanol synthesis was carried out on a Cu-Zn-Al type catalyst at 240℃ and 6.5 MPa, with a gas volume space velocity GHSV of 9000 h -1 (per standard volume), and the crude methanol was purified by rectification, and the obtained methanol had a mass fraction of not less than 99.85%.

[0030] S4, Methanol to olefins: This example was operated at 450℃ and near atmospheric pressure, with WHSV = 1.0-2.0 h -1 , and the single-pass conversion rate of methanol was 99.0-99.3%. After condensation, dehydration, and gas-liquid separation, low-carbon olefin streams were obtained by absorption, desorption, or rectification; the total molar selectivity of ethylene and propylene was 84-86%.

[0031] S5, Oligomerization reaction and thermal management: The oligomerization reactor was a two-stage fixed bed in series structure, with a total pressure of 6.0 MPa. The inlet temperature of the first stage was 80-95℃, and the WHSV was 1.0-1.5 h -1 ; the inlet temperature of the second stage was 100-115℃, and the WHSV was 0.8-1.2 h -1The heat exchange unit (steam generator) is arranged between the beds, and the steam pressure is 0.8-1.2 MPa. The selectivity of the C8-C16 aviation kerosene precursor is 72.0% (calculated based on carbon basis). The unreacted olefins are separated and sent back to the inlet of the oligomerization reactor by the recycle gas compressor, and the recycle ratio is 28%.

[0032] S6, hydrofining: the hydrofining unit is operated under the condition of a hydrogen volume fraction of 95%, a pressure of 3.0-5.0 MPa, a temperature of 260-320 ℃, and an LHSV of 1.0-1.5 h -1 The typical indicators of the finished product are: a freezing point of -48 ℃, an aromatic hydrocarbon mass fraction of 0.22%, a total sulfur of 3-5 ppm, and a total nitrogen of 1-2 ppm.

[0033] Example 2 The method for preparing sustainable aviation kerosene comprises the following steps: Raw material treatment: rice straw is selected as the biomass raw material. The treatment method is basically the same as that in Example 1.

[0034] S1, synthesis gas generated by biomass gasification: a fixed bed gasification furnace is used, the pressure is 3.0 MPa, and the temperature is 830-880 ℃. The dry basis volume fraction of the synthesis gas is: H2 30-33%, CO 46-48%, CO2 17-19%, CH4 1-2%, and H2S 30-60 ppm. After cyclone separation and ceramic filtration, the synthesis gas is sent to the subsequent section.

[0035] S2, purification and molar ratio adjustment: the synthesis gas is first cooled to about 40 ℃ by shift conversion, and then is cooled to the low-temperature methanol washing operating temperature by heat exchange and refrigeration, and is introduced into the low-temperature methanol washing device to remove acid gases. The actual measurement at the outlet of the purification is: H2S 0.5 ppm, CO2 0.5%; in the purification and adjustment unit, the H2 / CO is adjusted to 2.0 by combination of shift conversion, separation and hydrogen addition, and the dew point of the purified gas is -21 ℃.

[0036] S3, methanol synthesis and purification: the methanol synthesis is carried out on a Cu-Zn-Al type catalyst at 230 ℃ and 6.5 MPa, and the gas volume space velocity GHSV is 9000 h -1 (per volume at standard conditions), and the crude methanol is purified by rectification, and the mass fraction of the obtained methanol is not less than 99.85%.

[0037] S4, methanol to olefins: this embodiment is operated at 400 ℃ and near atmospheric pressure, and the WHSV is 1.2-1.6 h -1 , and the single-pass conversion rate of methanol is 99.0-99.1%. After condensation, dehydration, and gas-liquid separation, low-carbon olefins are obtained by absorption, desorption or rectification; the total molar selectivity of ethylene and propylene is 81-83%.

[0038] S5, oligomerization and heat management: the oligomerization reactor is a two-stage fixed bed in series structure, and the total pressure is 5.0 MPa. The first stage inlet temperature is 78-90℃, and the WHSV is 1.2h -1 ; the second stage inlet temperature is 98-110℃, and the WHSV is 1.0h -1 . A heat exchange unit (steam generator) is arranged between the bed layers, and the steam production pressure is 0.8-1.0 MPa. The selectivity of C8-C16 aviation kerosene precursor is 68.0% (calculated on the basis of carbon). The unreacted olefins are separated and sent back to the oligomerization reactor inlet by a recycle gas compressor, and the recycle ratio is 22%.

[0039] S6, hydrofining: the hydrofining unit is operated under the condition of hydrogen volume fraction 90%, pressure 3.0-4.0 MPa, temperature 260-300℃, and LHSV 1.0-1.3h -1 . The typical indicators of the finished product are: freezing point -42℃, aromatic hydrocarbon mass fraction 0.45%, total sulfur 4 ppm, and total nitrogen 1.5 ppm.

[0040] Example 3 The present embodiment provides a method for preparing sustainable aviation kerosene, which specifically comprises: Raw material treatment: forestry waste is selected as the biomass raw material. The treatment method is basically the same as that of Example 1.

[0041] S1, synthesis gas generated by biomass gasification: a gas flow bed gasifier is used, the pressure is 6.0 MPa, and the temperature is 900-950℃. The synthesis gas (dry basis volume fraction): H2 36-38%, CO 42-44%, CO2 15-16%, CH4 1-2%, and H2S 15-40 ppm. After cyclone separation and ceramic filtration, it is sent to the subsequent section.

[0042] S2, purification and molar ratio adjustment: the synthesis gas is first cooled to about 40℃ by shift conversion, and then reduced to the low-temperature methanol washing operating temperature by heat exchange and refrigeration, and then enters the low-temperature methanol washing device to remove acid gas. The actual measurement at the purification outlet: H2S 0.35 ppm, CO2 0.30%; in the purification and adjustment unit, the H2 / CO is adjusted to 2.2 by combination of shift conversion, separation and hydrogen addition, and the dew point of the purified gas is -23℃.

[0043] S3, methanol synthesis and purification: methanol synthesis is carried out on a Cu-Zn-Al type catalyst at 250℃ and 7.0 MPa, and the gas hourly space velocity GHSV is 8500h -1 (by volume at standard conditions), and the crude methanol is purified by rectification, and the obtained methanol mass fraction is not less than 99.85%.

[0044] S4, methanol to olefins: this embodiment is operated at 500℃ and near atmospheric pressure, and the WHSV is 1.0-1.4h -1, the methanol single-pass conversion rate is 99.1-99.3%, and the total molar selectivity of ethylene and propylene is 82-84%.

[0045] S5, oligomerization reaction and thermal management: the oligomerization reactor has a two-stage fixed bed series structure, and the total pressure is 7.0 MPa. The inlet temperature of the first stage is 85-100°C, and the WHSV is 1.0 h -1 ; the inlet temperature of the second stage is 105-120°C, and the WHSV is 0.8 h -1 . Heat exchange units (steam generators) are arranged between the bed layers, and the steam generation pressure is 1.0-1.2 MPa. The selectivity of C8-C16 aviation coal precursors is 74.0% (calculated based on carbon basis). The unreacted olefins are separated and sent back to the oligomerization reactor inlet by a recycle gas compressor, and the recycle ratio is 30%.

[0046] S6, hydrofining: the hydrofining unit is operated at a hydrogen volume fraction of 98%, a pressure of 4.0-5.0 MPa, a temperature of 280-320°C, and an LHSV of 1.0-1.4 h -1 . The typical indicators of the finished product are: a freezing point of -55°C, an aromatic hydrocarbon mass fraction of 0.18%, a total sulfur of 3 ppm, and a total nitrogen of 1 ppm.

[0047] Example 4 The present embodiment provides an integrated system for preparing sustainable aviation kerosene, which comprises in sequence and is in communication with: a biomass gasification unit, a purification and ratio adjustment unit, a methanol synthesis and rectification unit, a methanol-to-olefins and separation unit, an oligomerization reactor, a recycle gas compressor, and a hydrofining unit.

[0048] Among them: the purification and ratio adjustment unit comprises a shift cooling device and a low-temperature methanol washing device; the oligomerization reactor has a two-stage fixed bed series structure, and heat exchange units (steam generators) are arranged between the bed layers; the process conditions between units are matched through pressure, temperature, and components to realize continuous conversion, and the system is provided with an online detection and feedback adjustment mechanism at key points to ensure overall operation stability and efficiency.

[0049] The system process flow is as follows: (1) The biomass gasification unit converts the pretreated biomass raw material into synthesis gas under high temperature and high pressure conditions. The synthesis gas has a high CO and H2 ratio, and contains a certain amount of acidic impurities and particulate matter; (2) The synthesis gas after cyclone separation and ceramic filtration dust removal enters a purification and ratio adjustment unit, which is matched with the gasification outlet in pressure (4-6 MPa), first passes through a shift cooling and a low-temperature methanol washing system to deeply remove acidic components (H2S, CO2), and controls the gas dew point below -20°C; then passes through a combination of shift, separation and hydrogen supplement to accurately adjust the H2 / CO molar ratio to the interval of 2.0-2.2 to adapt to the metering requirement of the downstream methanol synthesis reaction; (3) The synthesis gas after purification and ratio adjustment is sent into a methanol synthesis and rectification unit after heat exchange and temperature rise, and methanol is synthesized under the action of a Cu-Zn-Al type catalyst at a medium-high pressure platform (6-7 MPa), and the gasification-purification-synthesis section in the system is kept in pressure grading coupling, the generated crude methanol is further rectified and purified to obtain high-purity methanol products with a mass fraction not less than 99.85%; (4) The high-purity methanol after pressure stabilization and temperature drop enters a methanol to olefin conversion and separation unit, and low-carbon olefins are generated under the reaction of a molecular sieve catalyst at a 400-500°C window and near atmospheric pressure, in order to guarantee the gas-liquid separation efficiency and material quality, the methanol feed composition and temperature control strategy are coupled with the outlet parameters of the upstream rectification to avoid cold and hot shock, the molar selectivity of ethylene and propylene in the unit product is controlled to be more than 80%, and the olefin stream is sent into the next unit after purification by a dehydration and oxygen-containing byproduct removal system; (5) The olefin stream is compressed and enters an oligomerization reactor, which operates at a pressure platform of 5.0-7.0 MPa, and adopts a two-section fixed bed series configuration, in order to coordinate the reaction heat release and selectivity control, a heat exchange unit (steam generator) arranged between the beds is used to remove heat in real time and output medium-pressure steam (0.8-1.2 MPa) to provide a heat energy recovery channel for the system to realize energy closed loop, the unit cooperatively controls the inlet composition, reuse ratio and reactor bed temperature gradient to ensure that the selectivity of C8-C16 aviation kerosene precursor is controlled to be more than 70%; (6) A circulating gas compressor returns the unreacted low-carbon olefins in the oligomerization outflow to the oligomerization reactor inlet to mix with fresh olefins, the system is provided with an automatic adjusting valve to control the reuse ratio to vary in the range of 15-40% to realize inlet component stabilization, reduce unit consumption and improve carbon efficiency, the material circulation path and heat management module are cooperatively operated to avoid accumulation of hydrocarbons, system flow deviation or conversion rate fluctuation; (7) The liquid-phase aviation kerosene precursor after gas-liquid separation is sent into a hydrofining unit, which completes process steps such as impurity removal, hydrogenation saturation and aromaticity inhibition under the conditions of a hydrogen volume fraction not less than 90% and medium-high pressure operation, the system links a downstream quality inspection module to perform online detection of aromatic hydrocarbons, condensation point and sulfur and nitrogen content to ensure that the final product meets the aviation kerosene technical specification.

[0050] Comparative Example 1 The process flow of the comparative example is consistent with that of Example 1 except for the following differences. The differences are as follows: In the purification and ratio adjustment unit, only the shift cooling and low-temperature methanol washing device is provided, and no ratio adjustment device for controlling the molar ratio of H2 / CO is configured.

[0051] The synthesis gas directly enters the methanol synthesis and rectification unit after purification treatment, and the molar ratio of H2 / CO remains the original ratio of 1.5 during gasification, and is not adjusted to the range of 2.0-2.2 set in the example.

[0052] Comparative Example 2 The process flow of the present comparative example is consistent with Example 1 except for the following differences. The difference settings are as follows: In step S4, the operating temperature of the methanol to olefin reaction is set to 350°C, which is lower than the temperature control range of 400-500°C used in the example, and the remaining reaction conditions remain unchanged, including the same catalyst, space velocity, and pressure parameters.

[0053] Comparative Example 3 The process flow of the present comparative example is consistent with Example 1 except for the following differences. The difference settings are as follows: In step S5, the oligomerization reactor is a two-stage fixed bed series structure, but no heat exchange unit is provided between adjacent beds, and no steam generator is configured for heat removal and reaction temperature control.

[0054] Comparative Example 4 The process flow of the present comparative example is consistent with Example 1 except for the following differences. The difference settings are as follows: In step S5, no recycle gas compressor is provided between the oligomerization reactor and the downstream separation unit, and the unreacted low-carbon olefins in the oligomerization product are not returned to the reactor inlet, and no reuse ratio adjustment device is configured in the system.

[0055] Comparative Example 5 The process flow of the present comparative example is consistent with Example 1 except for the following differences. The difference settings are as follows: In step S2, the synthesis gas purification method uses an amine method for acid removal system at room temperature, the operating temperature is 35-45°C, the system pressure is normal pressure to slight pressure difference, no low-temperature methanol washing device is used, and no cooling system for reducing the dew point of the gas is provided.

[0056] Comparative Example 6 The present comparative example provides a system for preparing sustainable aviation kerosene, and the structure and process flow thereof are consistent with Example 4 except for the following differences. The difference settings are as follows: The oligomerization reactor adopts a fixed bed series structure, but no heat exchange unit is arranged between the bed layers, and no steam generator is configured in the system for removal of reaction heat and recovery of medium-pressure steam; at the same time, no circulating gas compressor is arranged between the oligomerization reactor and the separation unit, and no return path of unreacted olefins is constructed; in addition, no device for adjusting the molar ratio of H2 / CO is arranged in the purification and ratio adjustment unit, and the purified synthesis gas is directly transported to the methanol synthesis and rectification unit.

[0057] To verify the effect of the key unit parameters and module settings in the application on the performance improvement of the product, Comparative Examples 1 to 5 and Comparative Example 6 were designed for control experiments, respectively, with Example 1 and Example 4. All the comparative experiments were carried out under uniform equipment conditions, keeping the raw material types, catalyst formulations and other process parameters consistent, only changing the characteristic variables to be verified, to ensure that the comparison is representative and unique.

[0058] Corn straw was used as the biomass raw material in the experiment, and the raw material treatment method was consistent with that of the examples. The dry basis moisture content was controlled at about 9.5%, and the bulk density was about 0.52 tons per cubic meter. Under stable operating conditions, each group of experiments independently prepared 5 batches of samples, with 100 Nm³ of synthesis gas processed per batch. After stable operation, gas and liquid samples were collected 3 times each for detection. The comparative example groups and main setting parameters are shown in Table 1: Table 1: Group and parameter settings Test indexes and test methods in the experiment: H2 / CO molar ratio: component analysis was performed using a thermal conductivity detector gas chromatograph, and the molar fraction ratio was calculated; Crude methanol yield: calculated based on the volume measurement of synthesis gas feed, combined with the mass of condensed methanol output (electronic scale), with the unit being kg / Nm³; Methanol mass fraction: determined by gas chromatography internal standard method; Ethylene + propylene molar selectivity: gas phase analysis was performed using a flame ionization detector, a capillary column HP-PLOT Al2O3 was selected, and the carbon atom basis was combined for calculation; C8-C16 fraction selectivity: liquid products were quantitatively segmented after atmospheric distillation, and carbon basis accounting was performed combined with GC analysis; Aviation kerosene product freezing point: tested using an automatic freezing point tester; Aromatic hydrocarbon mass fraction: determined by high performance liquid chromatograph; Carbon utilization rate: calculated based on the carbon content of the input and output materials (based on gas components + liquid fractions); Unit energy consumption: calculated based on the electric energy meter reading and the total amount of products, with the unit being kWh / kg of aviation kerosene.

[0059] After each group of experiments was continuously run, gas phase samples and liquid phase samples were collected for 3 times respectively, and the sample collection positions were the synthesis gas outlet, the top of the rectification unit, the oligomerization separation outlet and the outlet after hydrofining. Each batch of sampling was independently performed, and a total of 5 batches were collected as the basis for statistical data.

[0060] All test results were expressed in the form of "average value ± standard deviation", and the methanol yield, molar selectivity, freezing point and other indicators were subjected to paired t-test for significance judgment, and the confidence level was set to 95%, and p<0.05 was determined as significant difference.

[0061] Consistency of detection: all key detection items were operated by two technical personnel respectively, and the error was controlled by using parallel measurement and blind sample cross verification. All instruments were calibrated before each operation, and 99.999% high purity nitrogen was used as the carrier gas for gas chromatography, and the instrument drift error was controlled within ±0.3%. The carbon balance closure degree of all inlet and outlet gases and liquid products should reach more than 98%, and the data of abnormal batches were not included in the final statistical analysis.

[0062] The test results are shown in Tables 2 and 3.

[0063] Table 2 Comparison of properties of intermediate products and fractions in each group Table 3 Comparison of product quality and energy efficiency From the data in Tables 2 and 3, it can be seen that the embodiment of the present application is superior to each group of comparative examples in terms of intermediate product composition, target fraction yield, end product quality and system energy efficiency, etc. in many key performance indicators, as follows: (1) In terms of synthesis gas composition adjustment, in Example 1, the H2 / CO molar ratio was adjusted to 2.1, achieving the ideal stoichiometric ratio of synthesis gas, and the crude methanol yield reached 0.67 kg / Nm³, and the methanol mass fraction reached 99.85%. In Comparative Example 1, no adjustment device was configured, and H2 / CO remained at the original value of 1.5, resulting in a significant decrease in methanol yield to 0.51 kg / Nm³ and a decrease in mass fraction to 98.40%, verifying the necessity of the adjustment module in the efficient utilization of synthesis gas.

[0064] (2) In terms of temperature control in the methanol to olefin (MTO) reaction section, the temperature in the embodiment was controlled at 450℃, and the ethylene+propylene molar selectivity was 85.1%, while in Comparative Example 2, the reaction temperature was set to 350℃, and the selectivity decreased to 59.4%, and at the same time, the C8-C16 target fraction selectivity also decreased from 72.0% to 52.6%, indicating that the reasonable setting of the methanol to olefin (MTO) reaction temperature zone is crucial for ensuring the yield of light olefins and the composition of subsequent fractions.

[0065] (3) The embodiment is configured with a heat exchange unit between the beds and a steam generator, which ensures the thermal stability of the reactor. After cancelling the structure in Comparative Example 3, although the raw material structure does not change, the ethylene+propylene selectivity fluctuates slightly, and the C8-C16 fraction yield decreases to 63.7%, indicating that the heat exchange structure helps to stably generate medium and long chain oligomers and avoid the increase of side reactions.

[0066] (4) The embodiment realizes dynamic balance of reactant composition by recycling the unreacted olefins to the inlet of the oligomerization reactor through a circulating gas compressor. Comparative Example 4 does not have this unit, and the C8-C16 selectivity decreases to 65.1%, the carbon utilization rate decreases to 76.3%, and the unit energy consumption increases to 1.85 kWh / kg, proving that the recycling of unreacted olefins is the key path to improve energy efficiency.

[0067] (5) The embodiment uses a low-temperature methanol washing technology to ensure high gas cleanliness, and the aromatic hydrocarbon mass fraction is only 0.22%, and the product freezing point reaches-48℃. Comparative Example 5 uses a normal-temperature amine method to remove acid, and the purification depth is insufficient, the aromatic hydrocarbon content increases to 0.62%, and the freezing point increases to-35℃, indicating that the purification depth is directly related to the product quality.

[0068] (6) Example 4 integrates the heat exchange unit, the circulating gas compressor and the H2 / CO ratio adjusting device, and the overall carbon utilization rate is as high as 84.7%, and the unit energy consumption is as low as 1.62 kWh / kg. After cancelling the above modules in Comparative Example 6, the ethylene+propylene selectivity is only 75.6%, which is significantly lower than that of Example 1, the C8-C16 selectivity decreases from 72.0% to 63.0%, and the carbon utilization rate and energy efficiency are obviously retrogressed, verifying the key role of system synergistic integration in stable operation and efficient output.

[0069] In summary, the experimental data fully prove that the present application can realize higher light olefin selectivity, medium fraction yield and terminal product quality by optimizing process parameters and system structure, has lower aromatic hydrocarbon content and excellent low-temperature performance, and at the same time improves the carbon utilization rate and reduces the energy consumption.

[0070] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for producing sustainable aviation kerosene from methanol via biomass gasification, characterized in that, include: S1. Biomass gasification produces syngas; S2. The synthesis gas is purified, and the molar ratio of H2 / CO is adjusted to 2.0-2.2; S3. The synthesis gas is converted in the methanol synthesis and distillation unit to obtain methanol product; S4. Convert methanol into a low-carbon olefin stream mainly composed of ethylene and propylene under molecular sieve catalyst and 400-500℃ conditions, with a combined molar selectivity of ethylene and propylene not less than 80%; S5. The low-carbon olefins are oligomerized in a fixed-bed series oligomerization reactor at 5.0-7.0 MPa. Heat exchange units are set between the beds to transfer heat and control the temperature, generating C8-C16 jet fuel precursors. Unreacted olefins are returned to the reactor inlet through a recirculating gas compressor. S6. Hydrorefining the jet fuel precursor to obtain sustainable jet fuel.

2. The method according to claim 1, characterized in that, The biomass mentioned in step S1 is one or more of the following: rice straw, wheat straw, corn straw, reed, forestry waste, or urban dry waste; The biomass gasification unit is one of the fixed bed, entrained bed or fluidized bed types, and operates at a pressure of 3.0-6.0 MPa.

3. The method according to claim 1, characterized in that, In step S2, the syngas cooled by conversion is washed with low-temperature methanol to remove acidic gases, and the volume fraction of H2S at the purified outlet is not higher than 1 ppm and the volume fraction of CO2 is not higher than 0.5%, so as to meet the feed cleanliness and composition requirements of the downstream reaction.

4. The method according to claim 1, characterized in that, The methanol synthesis in step S3 is carried out at 220-260℃ on a Cu-Zn-Al catalyst; the crude methanol obtained by synthesis is purified by distillation, and the mass fraction of the methanol obtained is not less than 99.85%.

5. The method according to claim 1, characterized in that, The operating temperature for step S4 is 450℃.

6. The method according to claim 1, characterized in that, The fixed-bed series oligomer reactor in step S5 includes at least two series beds, and a steam generator is set between adjacent beds to remove the heat of reaction and suppress hot spots and coking, thereby improving the selectivity for C8-C16 fractions.

7. The method according to claim 1, characterized in that, The hydrorefining in step S6 is carried out under the condition that the volume fraction of hydrogen is not less than 90%; the resulting sustainable aviation kerosene has a pour point not higher than -40°C and an aromatic mass fraction not higher than 0.5%.

8. A system for implementing the method of any one of claims 1-7, characterized in that, It includes a biomass gasification unit, a purification and proportioning unit, a methanol synthesis and distillation unit, a methanol-to-olefins and separation unit, an oligomerization reactor, and a hydrorefining unit connected in sequence. The oligomerization reactor is connected to a recirculating gas compressor, which is used to return unreacted olefins from the oligomerization reactor to the reactor inlet. The purification and adjustment unit is configured to control the H2 / CO molar ratio at 2.0-2.2; The oligomer reactor is a fixed-bed series structure with a pressure of 5.0-7.0 MPa, and heat exchange units are set between the bed layers to implement heat transfer and temperature control.

9. The system according to claim 8, characterized in that, The biomass gasification unit is one of the fixed bed, entrained bed, or fluidized bed types, and operates at a pressure of 3.0-6.0 MPa. It is also equipped with a raw material pretreatment device to adapt to biomass raw materials of different forms and moisture contents.

10. The system according to claim 8, characterized in that, The purification and adjustment unit includes a conversion cooling device and a low-temperature methanol washing device, and is equipped with online detection and control components to ensure that the volume fraction of H2S at the purification outlet is not higher than 1 ppm.

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