Method and system for preparing aviation kerosene by coupling green hydrogen and biomass gasification

Abstract

The present application belongs to the technical field of biomass conversion and synthetic fuel, and relates to a method and system for preparing aviation kerosene by coupling green hydrogen and biomass gasification. The method comprises: preparing green hydrogen by electrolyzing water, and byproduct oxygen is used for biomass oxygen-enriched gasification; biomass is gasified in a fluidized bed at an oxygen partial pressure of 0.5-1 MPa and a temperature of 800-1000 DEG C to prepare syngas; the syngas is mixed with electrolytic hydrogen after pressure swing adsorption, methanol solution contact, low-temperature filtration and pressure reduction purification; the volume fraction of the feed hydrogen is stabilized at 70%-80% through online analysis and closed-loop control; crude oil is synthesized in a Fischer-Tropsch system taking methanol as a medium and carrier and oxalic acid as an adjusting agent; aviation kerosene fraction is obtained through rectification, and the heavy component is subjected to hydrocracking / isomerization by using a Pt-based catalyst. The present application effectively improves the stability of the feed hydrogen partial pressure and the product yield, and ensures the consistent quality of the aviation kerosene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomass conversion and synthetic fuel, in particular to a method and system for preparing aviation kerosene by coupling green hydrogen and biomass gasification. BACKGROUND

[0002] With the rapid growth of the demand for emission reduction and green fuel in the aviation industry, the use of biomass to prepare alternative aviation kerosene (sustainable aviation fuel, SAF) has become the focus of research and industry. At present, the mainstream path of biomass to liquid fuel usually includes: converting biomass into syngas in a fluidized bed or other gasification device, purifying and adjusting the components to achieve a suitable H2 / CO ratio, and then synthesizing hydrocarbon products under the action of iron-based or cobalt-based Fischer-Tropsch catalysts, and then obtaining the target aviation kerosene components through fraction cutting and hydroisomerization / cracking treatment. In order to improve the carbon utilization rate and product quality, external hydrogen, oxygen-rich gasification, reforming / shift, tail gas recycling and post-processing units are often introduced for system coupling.

[0003] The existing process generally takes H2 / CO molar ratio as the core parameter for feed ratio and process monitoring, but this index is difficult to fully reflect the dilution effect of inert or by-product components such as CO2, CH4 and N2 on the reaction gas, resulting in significant differences in hydrogen volume fraction and hydrogen partial pressure actually entering the Fischer-Tropsch reactor even if the H2 / CO ratio is the same, causing fluctuations in product distribution and reaction selectivity.

[0004] In terms of hydrogen / oxygen sources and system coupling, current external hydrogen is mostly dependent on fossil energy hydrogen production or distributed hydrogen sources; the green hydrogen produced by water electrolysis and its by-product oxygen have a low level of synergistic utilization in the gasification-synthesis system. In particular, the by-product oxygen is usually only used as ordinary oxygen-rich medium, without establishing a clear process cascade mechanism with the oxygen partial pressure control of the gasification unit, making it difficult to simultaneously ensure the stability of gasification, the quality of syngas and the feed requirements of the downstream synthesis unit.

[0005] Fischer-Tropsch synthesis reaction mostly uses metal / solid support catalyst system, which still has deficiencies in reaction heat transfer, mass transfer efficiency and metal active site microenvironment regulation. Although there are unit operations in existing industrial processes that use methanol as a physical absorbent or purification solvent, the system integration scheme of using methanol as a Fischer-Tropsch reaction medium and catalyst carrier, and synergizing with acidic or complexing-type regulators to optimize the active site environment and product distribution, still needs to be improved.

[0006] In the product separation and reconstituent utilization, the conventional process mainly obtains the aviation kerosene fraction through rectification, and the heavy components are subjected to hydroisomerization / cracking to improve the low-temperature fluidity and yield. However, the closed-loop strategy of recycling the heavy components to aviation kerosene lacks effective linkage between the upstream syngas feed control, and an operable and integrated system solution has not yet been formed.

[0007] In addition, the syngas purification and ratio adjustment units are usually independent of each other, and the operations such as pressure swing adsorption, absorption, filtration and pressure reduction cannot form an efficient and integrated process in cooperation with the online gas analysis and closed-loop control system, which is difficult to continuously provide high-quality syngas meeting the boundary conditions of the Fischer-Tropsch synthesis feed under fluctuating operating conditions. SUMMARY

[0008] The present application aims to solve the problems of large fluctuation of reaction hydrogen partial pressure, unstable product selectivity, low yield of aviation kerosene target fraction and difficulty in efficient recovery of heavy components in the existing process of preparing aviation kerosene fraction from biomass by Fischer-Tropsch synthesis due to poor controllability of feed, insufficient cooperation between gasification and synthesis section.

[0009] To achieve the above-mentioned purpose, the present application provides a method for preparing aviation kerosene by coupling green hydrogen and biomass gasification, comprising the following steps:

[0010] S1, hydrogen and oxygen are prepared by electrolyzing water, and the oxygen is used as a byproduct of the process;

[0011] S2, the pretreated biomass is fed into a fluidized bed gasifier with adjustable oxygen concentration, and is gasified under controlled oxygen partial pressure and temperature conditions to obtain syngas containing hydrogen, carbon monoxide, methane and carbon dioxide;

[0012] S3, the syngas is subjected to pressure swing adsorption purification, and is mixed with the hydrogen produced by electrolysis, and the mixed gas is adjusted so that the volume fraction of hydrogen entering the Fischer-Tropsch synthesis unit is 70%-80%, and the volume fraction is stabilized within the range of the hydrogen volume fraction through online gas component analysis combined with closed-loop control;

[0013] S4, in the presence of a metal catalyst, using methanol as a reaction medium, cooperating with a supported metal Fischer-Tropsch catalyst, and adding oxalic acid as a phase and active site environment regulator to obtain a crude synthesis oil;

[0014] S5, aviation kerosene fraction is obtained by column separation or rectification cutting, and heavy components are subjected to hydrocracking and / or isomerization to recover aviation kerosene products.

[0015] Further, the oxygen prepared in step S1 is used as an oxygen-rich medium in step S2 for adjusting the oxygen partial pressure of the gasification process, and is coordinated with the closed-loop control of the hydrogen volume fraction in step S3.

[0016] Further, the step S2 is carried out under the conditions of oxygen partial pressure 0.5-1 MPa and gasification temperature 800-1000 DEG C, the raw material is ground to a particle size less than 100 mesh by biomass pretreatment, and the volume fraction of the obtained synthesis gas satisfies the relationship H2:CO:CH4:CO2=1:(0-0.5):(0.5-0.8):1.

[0017] Further, the mass fraction of C1-C4 alcohols in the obtained crude synthesis oil in the step S4 is not less than 60%, and the mass fraction of heavy aromatic hydrocarbons is not less than 30%.

[0018] Further, the synthesis gas is mixed with electrolytic hydrogen according to the closed-loop control requirement of the set hydrogen volume fraction in the step S3, the mixed gas stream is purified by sequentially passing through a methanol solution contactor, a low-temperature filter and a pressure reduction unit before entering the Fischer-Tropsch synthesis reaction.

[0019] Further, the metal catalyst is a Co-based supported Fischer-Tropsch catalyst or a Fe-Cu-K system Fischer-Tropsch catalyst; and the heavy component hydrocracking and / or isomerization in the step S5 uses a Pt-based catalyst.

[0020] Further, the Fischer-Tropsch synthesis is carried out under the conditions of pressure 1-2 MPa and temperature 200-300 DEG C, pure hydrogen and methanol are simultaneously introduced into the Fischer-Tropsch synthesis unit, and the reaction product is obtained by column separation to obtain the aviation kerosene fraction.

[0021] The application further provides a system for preparing aviation kerosene by coupling green hydrogen and biomass gasification, which comprises an electrolytic hydrogen production unit, a biomass gasification unit, a synthesis gas purification and ratio adjustment unit, a Fischer-Tropsch synthesis unit, a separation unit and a heavy component treatment unit which are sequentially connected and communicate with each other.

[0022] The Fischer-Tropsch synthesis unit is provided with a reaction system of a supported metal Fischer-Tropsch catalyst and an oxalic acid regulator and is equipped with an online gas component analyzer and a closed-loop control module for maintaining the volume fraction of the feeding hydrogen; the oxygen outlet of the electrolytic hydrogen production unit is connected to the oxygen-rich inlet of the biomass gasification unit; and the separation unit is used for cutting to obtain the aviation kerosene fraction.

[0023] Further, the biomass gasification unit is a fluidized bed structure with adjustable oxygen concentration, is provided with an oxygen partial pressure control mechanism to maintain the oxygen partial pressure of 0.5-1 MPa, and is equipped with a pretreatment device capable of grinding the biomass to a particle size less than 100 mesh.

[0024] Further, the syngas purification and ratio adjustment unit comprises a pressure swing adsorption device for removing CO2, water and trace amounts of polar impurities, a hydrogen mixing manifold, a methanol solution contactor, a low-temperature filter and a pressure adjustment unit to ensure that the feed pressure entering the Fischer-Tropsch synthesis unit is in the target range of 1-2 MPa.

[0025] Preferably, the present application adopts a master-slave combined feedforward process level control strategy: taking feed hydrogen volume fraction closed loop control as the master loop and taking gasification unit oxygen partial pressure closed loop control as the slave loop; when the raw material characteristics change or system load disturbance causes syngas composition fluctuation, the oxygen-rich supply amount is corrected in real time through the feedforward mechanism, thereby shortening the disturbance recovery time and effectively inhibiting the transmission of fluctuations to the Fischer-Tropsch synthesis section; the trigger conditions of the feedforward control include but are not limited to: when the CH4 or CO2 content in the syngas exceeds the set threshold, or the gas flow rate changes by more than the limit, the oxygen-rich supply amount and the opening of the hydrogen mixing ratio valve are adjusted synchronously.

[0026] The present application has the following beneficial effects:

[0027] (1) By taking the feed hydrogen volume fraction as the main control variable and realizing online closed loop control, the effective hydrogen partial pressure at the inlet of the Fischer-Tropsch synthesis unit can be directly stabilized, the transmission and amplification of upstream raw material and load disturbance to the downstream are effectively inhibited, the feed fluctuation recovery time is significantly shortened, and the yield and batch consistency of the kerosene fraction are improved.

[0028] (2) The by-product oxygen from electrolysis of water is introduced into the oxygen partial pressure (0.5-1 MPa) closed loop control of the gasification section, which enhances the stability of the gasification process and the controllability of the syngas composition, reduces the dust and tar generation load, and provides cleaner and more stable gas source conditions for subsequent pressure swing adsorption and Fischer-Tropsch synthesis, and forms system synergy with the feed hydrogen fraction control.

[0029] (3) Taking methanol as the reaction medium and catalyst carrier and cooperating with oxalic acid as the regulator, the heat and mass transfer performance of the reaction system and the microenvironment of the metal active sites are effectively improved, which promotes the distribution of C1-C4 alcohols and heavy aromatic hydrocarbons in the crude synthesis oil to be more conducive to subsequent column separation and heavy component recovery, and improves the product compliance rate and performance stability of the kerosene fraction.

[0030] (4) By sequentially arranging the pressure swing adsorption device, the methanol solution contactor, the low-temperature filter and the pressure reduction unit, and cooperating with online gas component analysis and closed loop control module, the negative effects of polar and non-polar impurities and condensed components on the feed gas and catalyst are significantly reduced, and the long-term stable maintenance of the 70%-80% feed hydrogen volume fraction range is ensured.

[0031] (5) The system can be stably operated under Co-based supported or Fe-Cu-K system Fischer-Tropsch catalyst, and Pt-based catalyst is used for hydrocracking / isomerization upgrading and recycling of heavy components, so that the total distillate output rate of aviation kerosene, the low-temperature fluidity and the consistency of combustion performance are further improved, and the device adaptability and engineering amplification potential are good. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a general flow block diagram of the system of the application;

[0033] Figure 2 It is a schematic diagram of double closed-loop control structure;

[0034] Figure 3 It is a schematic diagram of biomass gasification unit and by-product oxygen access;

[0035] Figure 4 It is a flow chart of syngas purification and ratio adjustment unit;

[0036] Figure 5 It is a schematic diagram of separation unit and heavy component upgrading and recycling path;

[0037] Figure 6 It is a flow chart of the preparation method of the application;

[0038] Figure 7 It is a comparison diagram of feed closed-loop dynamic performance;

[0039] Figure 8 It is a comparison diagram of key properties of aviation kerosene distillate.

[0040] Reference signs:

[0041] 1 - electrolytic hydrogen production unit; 2 - biomass gasification unit; 3 - syngas purification and ratio adjustment unit; 4 - Fischer-Tropsch synthesis unit; 5 - separation unit; 6 - heavy component treatment unit.

[0042] 11 - hydrogen outlet; 12 - oxygen outlet.

[0043] 21 - oxygen-rich inlet; 22 - oxygen partial pressure sensor; 23 - fluidized bed reaction zone; 24 - pretreatment device.

[0044] 31 - pressure swing adsorption device; 32 - hydrogen mixing manifold; 33 - methanol solution contactor; 34 - low-temperature filter; 35 - pressure reduction unit; 36 - online gas component analyzer.

[0045] 51 - top condenser; 52 - reflux tank; 53 - aviation kerosene distillate side line;

[0046] 61 - hydrogenation bed layer; 62 - isomerization bed layer; 63 - back and forth pipeline.

[0047] 71 - oxygen line; 72 - syngas line; 73 - feed line; 74 - product line. DETAILED DESCRIPTION

[0048] For the person skilled in the art to understand and implement the present application, the present application is further described below in conjunction with the drawings and examples. The following embodiments are used to illustrate the present application and do not constitute a limitation on the scope defined by the claims. Any equivalent replacement or modification made without departing from the spirit of the present application shall be deemed to fall within the scope of the present application.

[0049] As shown in Figure 1 , the system for preparing aviation kerosene by coupling green hydrogen and biomass gasification provided by the present application comprises, in sequence according to the technological process: an electrolytic hydrogen production unit 1, a biomass gasification unit 2, a syngas purification and ratio adjustment unit 3, a Fischer-Tropsch synthesis unit 4, a separation unit 5, and a heavy component treatment unit 6; the heavy component treatment unit 6 comprises a hydrocracking unit and / or an isomerization unit.

[0050] The oxygen outlet 12 of the electrolytic hydrogen production unit 1 is connected to the oxygen-rich inlet 21 of the biomass gasification unit 2 through an oxygen line 71; the hydrogen outlet 11 of the electrolytic hydrogen production unit 1 is connected to the syngas purification and ratio adjustment unit 3 through a hydrogen mixing manifold 32; the syngas outlet of the biomass gasification unit 2 is connected to the syngas purification and ratio adjustment unit 3 through a syngas line 72; the gas outlet of the syngas purification and ratio adjustment unit 3 is connected to the feed inlet of the Fischer-Tropsch synthesis unit 4 through a feed line 73; the reaction product of the Fischer-Tropsch synthesis unit 4 enters the separation unit 5 through a product line 74, aviation kerosene fraction is obtained by separation, and the heavy components are sent to the heavy component treatment unit 6 for upgrading treatment, and the treated material is returned to the separation unit 5 through a return line 63.

[0051] As shown in Figure 2 , an online gas component analyzer 36 and a closed-loop control module are provided on the feed line 73 between the syngas purification and ratio adjustment unit 3 and the Fischer-Tropsch synthesis unit 4, for monitoring and adjusting the hydrogen volume fraction in the feed, and by controlling the hydrogen mixing manifold 32 and the related valve group, the hydrogen volume fraction entering the Fischer-Tropsch synthesis unit 4 is stably controlled within the range of 70%-80%. At the same time, an oxygen partial pressure sensor 22 is provided in the biomass gasification unit 2, which is connected to the oxygen outlet 12 of the electrolytic hydrogen production unit 1 and the oxygen-rich inlet 21 of the biomass gasification unit 2 through the oxygen line 71, to form a closed-loop control of the oxygen partial pressure in the gasification section, and the target oxygen partial pressure range is 0.5-1 MPa. The closed loop cooperates with the aforementioned closed loop of the hydrogen fraction in the feed to operate.

[0052] The closed-loop control module is an industrial process control unit for maintaining the feed hydrogen volume fraction and the gasification oxygen supply intensity within a set range. It receives the hydrogen volume fraction signal from the online gas component analyzer 36 and the oxygen partial pressure signal from the oxygen partial pressure sensor 22 as inputs; and sends the opening degree or flow rate command to the relevant valve group on the hydrogen mixing manifold 32 and the oxygen pipeline 71 to achieve precise control.

[0053] The oxygen partial pressure control mechanism is composed of the oxygen partial pressure sensor 22, the closed-loop control module, the oxygen pipeline 71, and the supporting regulating valve, which realizes the closed-loop regulation and control of the oxygen partial pressure in the biomass gasification unit 2. The oxygen partial pressure sensor 22 is a measurement and estimation module for obtaining the equivalent oxygen partial pressure, which preferably includes a high-temperature sampling probe, an inertization and cooling unit, a solid electrolyte or paramagnetic online oxygen analyzer, a supporting pressure transmitter, and a partial pressure calculation unit. The sensor is installed at the bypass sampling point of the oxygen-rich supply pipeline and the gas phase zone above the free board, and the sampling gas enters the oxygen analyzer after cooling and inertization treatment. Combined with the pressure and gas component data at this point, the equivalent oxygen partial pressure reflecting the oxygen supply intensity of the gasification zone is calculated, which is used as the controlled variable for the closed-loop control of the oxygen partial pressure in the gasification section.

[0054] The method of the present application specifically comprises the following steps:

[0055] S1, electrolysis of water to produce hydrogen and oxygen: hydrogen and oxygen are prepared by using an electrolysis device. The obtained hydrogen is used as a supplementary hydrogen source for subsequent synthesis gas ratio adjustment; the oxygen is used as a process byproduct, which is buffered and metered, and then used as an oxygen-rich medium for the biomass gasification unit 2, and is used in process synergy with the feed hydrogen volume fraction closed-loop control. The biomass gasification unit 2 is equipped with a pretreatment device 24 and a fluidized bed reaction zone 23, and the oxygen partial pressure in the reaction zone is controlled by the oxygen partial pressure sensor 22.

[0056] S2, biomass gasification: the pretreated biomass raw material is sent to the fluidized bed gasification furnace with adjustable oxygen concentration, and gasification is carried out under the controlled conditions of oxygen partial pressure 0.5-1 MPa and temperature 800-1000℃, to generate synthesis gas mainly composed of hydrogen, carbon monoxide, methane, and carbon dioxide. The biomass pretreatment includes grinding the raw material to a particle size of less than 100 mesh; under the preferred conditions, the normalized proportion of each component in the synthesis gas is H2: CO: CH4: CO2 = 1: (0-0.5): (0.5-0.8): 1 (based on H2 and CO2 as 1), which is used to represent the relative relationship of the gas composition.

[0057] S3, syngas purification, ratio adjustment and online closed loop control: the syngas is purified by a pressure swing adsorption device 31 (PSA), and then mixed with electrolytic hydrogen; the mixed gas is sequentially subjected to impurity removal by a methanol solution contactor 33, a low-temperature filter 34 and a pressure reduction unit 35, and after purification, is used as a feed for Fischer-Tropsch synthesis, and the volume fraction of the feed hydrogen gas entering the Fischer-Tropsch synthesis unit 4 is stably controlled at 70%-80% by an online gas component analyzer 36 and a closed loop control module. To achieve this goal, the mixing ratio of electrolytic hydrogen to syngas is dynamically adjusted according to the closed loop setting, and the mass ratio is preferably: syngas: electrolytic hydrogen = 1:0.1-0.3; the range of the hydrogen volume fraction is jointly ensured by the closed loop control and hydrogen supplement strategy.

[0058] S4, Fischer-Tropsch synthesis: the Fischer-Tropsch synthesis reaction is carried out under the action of a metal catalyst, the reaction system uses methanol as the reaction medium and catalyst carrier, and oxalic acid is added as an adjusting agent, and the synthesis reaction is preferably carried out at a pressure of 1-2 MPa and a temperature of 200-300°C, and pure hydrogen and methanol are introduced into the reactor. A Co-based supported Fischer-Tropsch catalyst or a Fe-Cu-K Fischer-Tropsch catalyst can be used. In the obtained crude synthetic oil, the mass fraction of C1-C4 alcohols is not less than 60%, and the mass fraction of heavy aromatic hydrocarbons is not less than 30%.

[0059] S5, separation and heavy component upgrading and recovery: aviation kerosene fractions are obtained by column separation or rectification cutting; the heavy components are subjected to hydrocracking and / or isomerization treatment, preferably using a Pt-based catalyst, and the upgraded heavy components are recycled and combined into the aviation kerosene product.

[0060] The present application sets two process-level closed loop control loops, as follows:

[0061] The first loop is the feed hydrogen volume fraction closed loop:

[0062] An online gas component analyzer 36 is arranged at the outlet of the syngas purification and ratio adjustment unit 3 to monitor the gas composition in real time; the detection signal is transmitted to a closed loop control module, which dynamically controls the hydrogen supplement amount and / or the purified gas reflux ratio by adjusting the hydrogen mixing ratio valve and the vent valve or reflux valve of the pressure swing adsorption device 31, so that the hydrogen volume fraction in the feed gas entering the Fischer-Tropsch synthesis unit 4 is stably maintained within the range of 70%-80%.

[0063] The second loop is the gasification oxygen partial pressure closed loop:

[0064] An oxygen partial pressure sensor 22 is arranged in the biomass gasification unit 2 to detect the oxygen partial pressure state of the gasification reaction zone in real time; the signal is transmitted to the same or coordinated closed loop control module, which controls the delivery amount of the oxygen-rich medium by adjusting the oxygen supply valve on the electrolysis byproduct oxygen supply pipeline, so that the oxygen partial pressure of the gasification reaction zone is stably maintained at 0.5-1 MPa.

[0065] The preferred control strategy is master-slave + feedforward structure:

[0066] The feed hydrogen volume fraction closed loop is used as the main control loop, the gasification oxygen partial pressure closed loop is used as the slave loop, and a feedforward compensation mechanism is introduced. When the raw material properties change or the system load disturbance causes the gas composition to change, the feedforward correction of the gasification oxygen partial pressure closed loop set value is performed in advance to quickly stabilize the synthesis gas output characteristics at the gasification end and inhibit the transmission of the disturbance to the downstream Fischer-Tropsch synthesis feed.

[0067] Example 1

[0068] Raw materials and pretreatment: The raw material is corn straw, and the moisture content is about 8wt%. The raw material is ground to a particle size of less than 100 mesh by a hammer mill-screening combined process. The treated material is stored in a dry silo and protected by a nitrogen atmosphere to prevent moisture absorption and oxidation.

[0069] Device and instrument configuration: A proton exchange membrane water electrolysis device is used, with a rated hydrogen production capacity of 10Nm 3 / h, equipped with an oxygen buffer tank and a mass flowmeter; the gasification unit uses a bubbling fluidized bed gasifier, equipped with an oxygen-rich gas injection port and an oxygen partial pressure sensor 22; the synthesis gas purification and ratio adjustment unit 3 includes a pressure swing adsorption device 31, a hydrogen mixing manifold 32, a methanol solution contactor 33, a low-temperature filter 34, and a pressure reduction unit 35; the Fischer-Tropsch synthesis unit 4 is a fixed bed reactor, equipped with a methanol supply liquid metering pump, an oxalic acid solution metering pump, and an online gas component analyzer 36 in the feed line; the separation unit 5 is a rectification system, equipped with a top condenser 51 and a reflux tank 52, and the aviation kerosene fraction is recovered through a side line 53, and the heavy component hydrogenation cracking unit uses a platinum-based catalyst.

[0070] Start-up and temperature rise: The gasifier is first replaced with nitrogen for 30 minutes, gradually heated to 600℃, then the oxygen-rich gas is introduced, and the temperature is continued to rise to the target operating temperature; the Fischer-Tropsch synthesis unit 4 is also replaced with nitrogen and heated to 200℃ standby; the methanol circulating tank is controlled to 8℃ standby.

[0071] The specific operation steps include:

[0072] S1, start the water electrolysis device, and the generated oxygen is transported to the gasifier as an oxygen-rich medium;

[0073] S2, under the conditions of oxygen partial pressure 0.80MPa and temperature 900℃, carry out biomass gasification, and the feeding amount is 100kg / h;

[0074] S3, the synthesis gas after purification by pressure swing adsorption is mixed with electrolytic hydrogen, and the hydrogen volume fraction in the feed of Fischer-Tropsch synthesis is maintained at 70%-80% by closed loop control. The mixed gas is further purified by methanol solution contactor 33, low temperature filter 34 and pressure reduction unit 35 in sequence to remove impurities;

[0075] S4, the Fischer-Tropsch synthesis reaction uses Fe-Cu-K / SiO2 catalyst, methanol as reaction medium and catalyst carrier, and the addition amount of oxalic acid is 0.05-0.10wt% of the mass of methanol. The reaction is carried out at a pressure of 1.5MPa and a temperature of 250℃, and pure hydrogen and methanol are co-fed into the reactor;

[0076] S5, the reaction product is cut into aviation kerosene fraction by rectification, and the heavy component is subjected to hydrocracking under the action of platinum-based catalyst and then returned to the aviation kerosene product stream after upgrading.

[0077] The Fischer-Tropsch feed is sampled every 10 minutes to record the hydrogen volume fraction; the crude synthetic oil is sampled every hour, and the mass fraction of C1-C4 alcohols and the mass fraction of heavy aromatic hydrocarbons are determined by offline gas chromatography (GC) analysis; the aviation kerosene fraction is detected according to the industry standard method to determine its 15℃ density, freezing point, smoke point and 20℃ kinematic viscosity.

[0078] Example 2

[0079] On the basis of Example 1, the Fischer-Tropsch synthesis catalyst is replaced by Co / Al2O3 catalyst, and the rest of the device configuration and control strategy remains unchanged.

[0080] Specific operation steps: S1-S3 are the same as Example 1, the closed loop control sets the target value of hydrogen volume fraction to 75%, and the allowable fluctuation bandwidth is 70%-80%; in S4, the reaction conditions are adjusted to a pressure of 1.5MPa and a temperature of 240℃, methanol is still used as the reaction medium and catalyst carrier, and the addition amount of oxalic acid is 0.05-0.10wt% of the mass of methanol; S5 is consistent with Example 1.

[0081] Sampling and detection: the detection items and methods are the same as Example 1.

[0082] Example 3

[0083] The raw material is replaced by wheat straw powder, and the water content of the raw material is increased from 8wt% to 15wt%, and a load step disturbance of ±10% is implemented on the basis of the rated load;

[0084] The oxygen partial pressure closed loop control target of the gasification section is set to 0.85MPa; the hydrogen volume fraction closed loop target of the Fischer-Tropsch synthesis feed is 75%; the rest of the device, control and operation conditions are the same as Example 1.

[0085] Sampling and detection: record the system recovery time, steady-state error and fluctuation amplitude after the disturbance is applied; crude synthetic oil samples are collected every 30 minutes for offline analysis of composition changes.

[0086] Example 4

[0087] The control architecture is implemented with the feed hydrogen volume fraction closed loop as the main loop and the gasification oxygen partial pressure closed loop as the secondary loop, and a feedforward mechanism is introduced: when the online gas analysis detects that the CH4 or CO2 content exceeds the set threshold, the feedforward action is triggered to dynamically correct the oxygen-rich supply flow;

[0088] The control target of hydrogen volume fraction is set to 75%, and the control target of oxygen partial pressure is set to 0.80 MPa; the system receives two load disturbances with an amplitude of ±10% within 15 minutes.

[0089] Sampling and detection: record the main and secondary loop control valve opening changes and the system time constant; simultaneously monitor and record the dynamic response curves of the feed hydrogen volume fraction and the gasification oxygen partial pressure.

[0090] Example 5

[0091] The system configuration of this example is as follows:

[0092] The rated hydrogen production capacity of the electrolytic hydrogen production unit is 10 Nm 3 / h; the gasification unit uses a bubbling fluidized bed reactor equipped with an oxygen-rich gas injection port and an oxygen partial pressure sensor 22; the synthesis gas purification and ratio adjustment unit 3 includes a pressure swing adsorption device 31, a hydrogen mixing manifold 32, a methanol solution contactor 33, a low-temperature filter 34, and a pressure reduction unit 35; the Fischer-Tropsch synthesis unit 4 is a fixed bed reactor provided with a methanol supply liquid metering pump, an oxalic acid solution metering pump, and an online gas component analyzer 36 in the feed line; the separation unit 5 is a rectifying column system provided with a top condenser 51 and a reflux tank 52, and the aviation kerosene fraction is taken out through the side line 53; the heavy component treatment unit 6 includes a hydrocracking unit and / or an isomerization unit; preferably configured as a combination of hydrogenation bed layer 61 and isomerization bed layer 62, and the upgraded product is returned to the separation unit 5 through the return line 63.

[0093] The system runs continuously and stably for 72 hours, during which: the feed hydrogen volume fraction of the Fischer-Tropsch synthesis unit is closed-loop controlled within the range of 70%-80%; the oxygen partial pressure of the biomass gasification unit is closed-loop controlled within the range of 0.5-1 MPa.

[0094] Comparative Example 1

[0095] Run under the conditions described in Example 1, but do not add oxalic acid to the methanol reaction medium; the rest of the device configuration, operating parameters and control strategy are consistent with Example 1.

[0096] Operating conditions: oxygen partial pressure in gasification stage is 0.80 MPa, and gasification temperature is 900℃; the synthesis gas is mixed with electrolytic hydrogen after purification by pressure swing adsorption, and the mixed gas is purified by methanol solution contactor 33, low temperature filter 34 and pressure reduction unit 35 in sequence; the Fischer-Tropsch synthesis reaction is carried out at a pressure of 1.5 MPa and a temperature of 250℃, and methanol is used as the reaction medium and catalyst carrier.

[0097] Sampling and detection: the detection items and frequency are the same as in Example 1.

[0098] Comparative Example 2

[0099] Based on Example 1, the methanol in the Fischer-Tropsch reaction system is replaced by an inert organic solvent (such as n-hexane, isooctane), and the oxalic acid injection port and addition function are retained; the rest of the device, working condition and control setting remain unchanged.

[0100] Operating conditions: oxygen partial pressure in gasification is 0.80 MPa, and gasification temperature is 900℃; the synthesis gas is mixed with electrolytic hydrogen after purification by pressure swing adsorption, and the mixed gas is purified by inert organic solvent contact cooling, low temperature filter 34 and pressure reduction unit 35; the Fischer-Tropsch synthesis reaction is carried out at a pressure of 1.5 MPa and a temperature of 250℃.

[0101] Sampling and detection: the detection items and frequency are the same as in Example 1.

[0102] Comparative Example 3

[0103] The online gas component analysis and closed-loop control are cancelled, and only H2 / CO molar ratio ≈2.0 is used as the feed blending index; the rest of the device and process are the same as in Example 1.

[0104] Operating conditions: oxygen partial pressure in gasification is 0.80 MPa, and gasification temperature is 900℃; the synthesis gas is mixed with electrolytic hydrogen after purification by pressure swing adsorption, and the mixed gas is purified by inert organic solvent contact cooling, low temperature filter 34 and pressure reduction unit 35; the Fischer-Tropsch synthesis reaction is carried out at a pressure of 1.5 MPa and a temperature of 250℃.

[0105] Sampling and detection: the feed gas is sampled every 10 minutes, and the actual volume fraction of hydrogen is recorded; the crude synthesis oil is sampled every hour, and the composition of C1-C4 alcohols and heavy aromatic hydrocarbons is detected; the performance indicators of the separated products are detected according to standard methods.

[0106] In order to evaluate the influence of different process conditions on the performance of the system, a standardized test process is established and key data are recorded, and the specific test scheme and recording method are as follows:

[0107] Test objects and grouping: the test includes examples 1-5 and comparative examples 1-3, a total of 8 groups; each group is repeatedly operated under key working conditions not less than 3 times, and the results are expressed by mean value ± standard deviation; the device process, measuring point arrangement and sampling mode strictly follow the description in each example and comparative example. Three types of typical disturbances are introduced in the test: raw material switching (pine powder → straw powder), moisture increase (8 → 15 wt%), load step (± 10%); under the master-slave + feedforward control structure, the dynamic response trajectories of hydrogen volume fraction, oxygen partial pressure and corresponding control valve position are recorded synchronously.

[0108] Feed control: the hydrogen volume fraction in the feed gas entering the Fischer-Tropsch synthesis unit is 70%-80% as the main control target; comparative example 3 only controls the feed ratio according to H2 / CO≈2, and does not enable the hydrogen volume fraction closed loop.

[0109] Synthesis gas purification and ratio adjustment: after the synthesis gas is purified by the pressure swing adsorption device 31, it is mixed with electrolytic hydrogen, and the mixed gas is sequentially purified by the methanol solution contactor 33, the low temperature filter 34 and the pressure reduction unit 35, and then enters the Fischer-Tropsch synthesis unit 4.

[0110] Fischer-Tropsch synthesis system: methanol is used as the reaction medium and catalyst carrier, and oxalic acid is used as the regulator; the catalyst is selected from cobalt-based supported catalyst or iron-copper-potassium Fischer-Tropsch catalyst; the reaction pressure is 1-2 MPa, and the temperature is 200-300℃.

[0111] Separation and heavy component recovery: tower separation or rectification is used to obtain aviation kerosene fraction; after the heavy component is subjected to hydrocracking and / or isomerization upgrading by a platinum-based catalyst, it is returned to the aviation kerosene product.

[0112] Gasification section operation: gasification is carried out in a fluidized bed gasifier with adjustable oxygen concentration, and the oxygen partial pressure closed loop control target is 0.5-1 MPa, and the temperature is maintained at 800-1000℃.

[0113] Index definition: feed hydrogen volume fraction (%): online analysis measured value; fluctuation amplitude: maximum absolute deviation of actual value and target value; recovery time (s): time experienced from disturbance occurrence to parameter recovery to target value ± 1% bandwidth; C1-C4 alcohol mass fraction (wt%): calculated based on total mass of crude synthesis oil; heavy aromatic hydrocarbon mass fraction (wt%): calculated based on total mass of crude synthesis oil; aviation kerosene fraction yield (wt%): calculated based on total mass of crude synthesis oil; oxygen partial pressure fluctuation (%): percentage deviation of actual oxygen partial pressure relative to set value.

[0114] The results are shown in Tables 1-4.

[0115] Table 1 Key indicators of feed control and Fischer-Tropsch product composition

[0116] The results are shown in Tables 1-4.

[0117] Note: The heavy aromatics in Table 1 are heavy components (before upgrading) distillate;

[0118] Table 2 Influence of oxygen partial pressure closed loop on gasification stability

[0119]

[0120] Table 3 Key physicochemical properties of aviation kerosene distillate

[0121]

[0122] Note: The data in Table 3 are for the final aviation kerosene distillate, the density is measured at 15°C, and the kinematic viscosity is measured at -20°C;

[0123] Table 4 Double closed loop dynamic indicators and oxygen partial pressure fluctuation

[0124]

[0125] From the data in Table 1, compared with Comparative Example 3 which only controls H2 / CO≈2, the fluctuation range of the hydrogen feed volume fraction is reduced from ±5.2% to ±1.1% in Example 1, and the recovery time is shortened from 240 seconds to 55 seconds; the fluctuation range of Examples 2-5 is stabilized between ±1.2% and ±1.5%, and the average recovery time is between 48-60 seconds. Taking "70%-80% of the hydrogen feed volume fraction" as the main control variable, the upstream disturbance transmission can be effectively inhibited, the effective hydrogen concentration and hydrogen partial pressure at the inlet of the Fischer-Tropsch synthesis unit are stabilized, and a key guarantee is provided for the improvement of the aviation kerosene distillate yield. According to the dynamic response data, the time constant of the closed loop system is estimated to be 13.7-17.7 seconds according to t S ≈3.5τ (t S is the time after disturbance to adjust to ±1% bandwidth, and τ is the equivalent first-order time constant), which is significantly lower than 68.6 seconds of Comparative Example 3, further confirming the effectiveness of the control strategy from the response characteristic angle.

[0126] Compared with the comparative example 1 without adding oxalic acid, the content of C1-C4 alcohols in the product distribution of example 1 is increased from 56.8 wt% to 65.4 wt%, and heavy aromatic hydrocarbons are increased from 29.0 wt% to 32.1 wt%; compared with the comparative example 2 without using methanol as a reaction medium and a catalyst carrier, the content of C1-C4 alcohols is significantly increased from 50.5 wt% to 65.4 wt%, and heavy aromatic hydrocarbons are increased from 24.8 wt% to 32.1 wt%. The above results show that the combined use of methanol and oxalic acid effectively optimizes the heat and mass transfer performance of the reaction system and the microenvironment of the metal active site, promotes the distribution of light alcohols and heavy aromatic hydrocarbons to be more conducive to subsequent tower separation and heavy component recovery, and the corresponding aviation kerosene fraction exhibits better performance in key properties such as freezing point, smoke point and viscosity.

[0127] From the gasification stability, the data in Table 2 shows that after introducing the oxygen partial pressure closed-loop control, the oxygen partial pressure fluctuation is reduced from 7.5% to 2.0%, the dust and tar contents in the synthesis gas are reduced from 60 mg / Nm 3 and 1.9 g / Nm 3 to 25 mg / Nm 3 and 0.8 g / Nm 3 , respectively, and the synthesis gas composition is more stably in the target interval of H2:CO:CH4:CO2=1:(0-0.5):(0.5-0.8):1. The stable operation of the upstream gasification and the cooperation of the downstream feed closed loop jointly contribute to the stability improvement of the aviation kerosene fraction yield and product composition in Table 1.

[0128] The unit sequence of “pressure swing adsorption→methanol solution contact→low-temperature filtration→reduced pressure” effectively reduces the interference of polar and nonpolar impurities, particles and condensed components on the feed gas quality and the catalyst activity, and in combination with the feed hydrogen volume fraction closed-loop control, the system can stably maintain the hydrogen volume fraction in the range of 70%-80% under the conditions of raw material and load fluctuation.

[0129] In terms of catalyst adaptability, whether a Co-based supported catalyst or a Fe-Cu-K Fischer-Tropsch catalyst is used, Tables 1 and 3 show that under the cooperation of the control strategy and the reaction medium / regulator, stable product distribution and aviation kerosene fraction properties can be obtained. The heavy components are treated by hydrogenation cracking or isomerization with a platinum-based catalyst and then returned to the aviation kerosene product, further improving the consistency of the total fraction yield and product properties.

[0130] Without departing from the core idea of the present application and the scope of the claims, the following adjustments can be made in practical applications:

[0131] The biomass raw material can be straw, forest residue or other agricultural and forestry waste, which is pretreated to a particle size of less than 100 mesh;

[0132] The gasification operation conditions can be adjusted in the range of 0.5-1 MPa of oxygen partial pressure and 800-1000 DEG C of temperature;

[0133] The mixing ratio of the synthesis gas and the electrolytic hydrogen is controlled in real time in a closed loop under the premise that the volume fraction of the feeding hydrogen is 70%-80%, and the recommended mass ratio of the synthesis gas to the electrolytic hydrogen is 1:0.1-0.3;

[0134] The Fischer-Tropsch catalyst can be selected from Co-based supported type and Fe-Cu-K system, and the reaction pressure and temperature can be optimized in the range of 1-2 MPa and 200-300 DEG C, respectively;

[0135] The separation can adopt tower type separation or rectification cutting, and the heavy component treatment can select hydrocracking, isomerization or combination of both in series and parallel.

[0136] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art 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, and various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A method for preparing aviation kerosene by coupling green hydrogen and biomass gasification, characterized in that, The method comprises the following steps: S1, producing hydrogen and oxygen by electrolysis, wherein the oxygen is used as a byproduct of the process; S2, feeding pretreated biomass into a fluidized bed gasifier with adjustable oxygen concentration, and gasifying the biomass under controlled oxygen partial pressure and temperature to obtain synthesis gas containing hydrogen, carbon monoxide, methane and carbon dioxide; S3, purifying the synthesis gas by pressure swing adsorption, mixing the purified synthesis gas with the hydrogen produced by electrolysis, and adjusting the mixed gas so that the volume fraction of hydrogen fed into a Fischer-Tropsch synthesis unit is 70%-80%, and the volume fraction is stabilized in the range of the hydrogen volume fraction by online gas component analysis combined with closed-loop control; S4, performing Fischer-Tropsch synthesis reaction in methanol as a reaction medium, using a supported metal Fischer-Tropsch catalyst, and adding oxalic acid as a phase and active site environment regulator to obtain crude synthetic oil; S5, obtaining aviation kerosene fraction by column separation or rectification, and performing hydrocracking and / or isomerization on heavy components to recover aviation kerosene products.

2. The method of claim 1, wherein, The oxygen produced in step S1 is used as an oxygen-rich medium in step S2 to adjust the oxygen partial pressure of the gasification process and cooperate with the hydrogen volume fraction closed-loop control in step S3.

3. The method of claim 1, wherein, Step S2 is performed under the conditions of an oxygen partial pressure of 0.5-1 MPa and a gasification temperature of 800-1000℃, the biomass is pretreated by grinding the raw material to a particle size of less than 100 mesh, and the volume fraction relationship of the obtained synthesis gas satisfies H2:CO:CH4:CO2=1:(0-0.5):(0.5-0.8):

1.

4. The method of claim 1, wherein, The mass fraction of C1-C4 alcohols in the crude synthetic oil obtained in step S4 is not less than 60%, and the mass fraction of heavy aromatic hydrocarbons is not less than 30%.

5. The method of claim 1, wherein, In step S3, the synthesis gas is mixed with the electrolytic hydrogen according to the set hydrogen volume fraction closed-loop control requirement at a mass ratio of 1:0.1-0.3, and the mixed gas stream is purified by sequentially passing through a methanol solution contactor, a low-temperature filter and a pressure reduction unit before entering the Fischer-Tropsch synthesis reaction.

6. The method of claim 1, wherein, The supported metal Fischer-Tropsch catalyst is a Co-based supported Fischer-Tropsch catalyst, and the heavy component hydrocracking and / or isomerization in step S5 uses a Pt-based catalyst.

7. The method of claim 1, wherein, The Fischer-Tropsch synthesis reaction is performed under the conditions of a pressure of 1-2 MPa and a temperature of 200-300℃, pure hydrogen and methanol are simultaneously introduced into the Fischer-Tropsch synthesis unit, and the reaction product is column separated to obtain aviation kerosene fraction.

8. A system for implementing the method of any one of claims 1-7 for the production of aviation kerosene by coupling green hydrogen with biomass gasification, characterized in that, The method comprises the following steps: The Fischer-Tropsch synthesis unit is configured to use methanol as a reaction medium, use a reaction system of a supported metal Fischer-Tropsch catalyst and an oxalic acid regulator, and be equipped with an online gas component analyzer and a closed-loop control module to maintain the volume fraction of the feed hydrogen; the oxygen outlet of the electrolytic hydrogen production unit is connected to the oxygen-rich inlet of the biomass gasification unit; and the separation unit is used to cut aviation kerosene fraction.

9. The system of claim 8, wherein, The biomass gasification unit is a fluidized bed structure with adjustable oxygen concentration, provided with an oxygen partial pressure control mechanism to maintain an oxygen partial pressure of 0.5-1 MPa, and equipped with a pretreatment device capable of grinding the biomass to a particle size of less than 100 mesh.

10. The system of claim 8, wherein, The synthesis gas purification and ratio adjustment unit includes a pressure swing adsorption device for removing CO2, water and trace polar impurities, a hydrogen mixing manifold, a methanol solution contactor, a low-temperature filter and a pressure adjustment unit to ensure that the feed pressure entering the Fischer-Tropsch synthesis unit is within the target range of 1-2 MPa.

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