Biomass high-temperature fuel gas multistage catalytic deep decoking method

Abstract

The invention relates to the technical field of biomass energy utilization, in particular to a biomass high-temperature fuel gas multi-stage catalytic deep decoking method which comprises the following steps: introducing biomass gasified high-temperature fuel gas into a micro-aerobic catalytic oxidation reaction section, controlling the oxygen concentration in the micro-aerobic catalytic oxidation reaction section to be in a range of 0.8-1.5%, and controlling the oxygen concentration in the micro-aerobic catalytic oxidation reaction section to be in a range of 0.8-1.5%; tar and part of low-carbon hydrocarbon in the biomass gasified high-temperature fuel gas are partially removed through a catalytic oxidation reaction; the fuel gas treated by the micro-aerobic catalytic oxidation reaction section is introduced into a water vapor catalytic reforming reaction section, residual methane and low-carbon hydrocarbon are converted into hydrogen and carbon monoxide through catalytic hydrogenation at the temperature of 800-1000 DEG C in the water vapor catalytic reforming reaction section, and micro-aerobic catalytic oxidation and water vapor catalytic reforming conversion reaction have a synergistic effect; the total conversion rate of CH4 is gt; the tar removal rate gt is 99.5% and the tar removal rate gt; therefore, the purification degree of the fuel gas is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass energy utilization, and particularly relates to a method for multi-stage catalytic deep decoking of high-temperature biomass gas, which can be used for deeply removing tar and low-carbon hydrocarbon components in the gas generated during biomass gasification, and providing high-quality raw gas for downstream production processes such as hydrogen production, methanol production, and fuel oil production from biomass gas. Background Art

[0002] With the increasing depletion of non-renewable energy sources such as coal, oil, and natural gas, as well as the intensification of the global energy crisis and climate change, the development and utilization of renewable energy have become the core direction of the energy strategies of countries around the world. As a zero-carbon renewable resource, biomass energy has been widely applied in industrial, agricultural, and civil fields through power generation, heating, and gas supply due to its wide distribution, rich resources, and environmental friendliness.

[0003] Currently, the utilization technologies of biomass energy mainly include direct combustion, post-gasification combustion, and continued synthesis of green methanol from syngas. However, the gas generated during biomass gasification usually contains a large amount of tar (5 - 30 g / Nm 3 ) and hydrocarbon impurities (such as CH4). These impurities not only clog pipelines, corrode equipment, but also cause secondary pollution, severely restricting the direct utilization of biomass gas. For the process route of producing syngas from biomass gas and then synthesizing methanol, dimethyl ether, etc., deep removal of tar is particularly important. Therefore, how to effectively remove tar and increase the content of combustible gases such as H2 and CH4 in biomass gas has become the current research focus and key technology.

[0004] Currently, the tar removal technologies for biomass gas are mainly divided into two categories: physical methods and thermochemical methods. Physical methods include wet methods (or wet-dry methods) and dry methods. Although they have the advantages of simple equipment, convenient operation, and low cost, they cannot deeply eliminate tar, may cause secondary pollution to the ecological environment, and the tar itself cannot be effectively utilized, resulting in difficulty in improving the overall energy conversion and utilization efficiency (see Chinese Patent Application CN99116313.3).

[0005] In contrast, the high-temperature thermochemical method can cause the contained tar to undergo sufficient two-stage cracking to be converted into hydrogen, carbon monoxide, and low-carbon hydrocarbons, etc. by increasing the temperature of the gas, which can greatly increase the tar removal rate and the gasification efficiency at the same time. The thermal cracking method is a common gas thermochemical decoking technology, but it requires a temperature as high as above 1250°C to completely convert tar. In order to increase the temperature to such a high level, usually oxygen is supplemented in the gas to raise the temperature through partial combustion, which in turn leads to process technical problems such as improving the burnout utilization rate of the supplemented oxygen, fully utilizing the high temperature after thermal cracking, and ensuring the oxygen-free explosion-proof safety of the subsequent process (see Chinese Patent Application CN200810137286.2).

[0006] In recent years, technologies such as catalytic cracking and steam reforming of biomass gas have gradually become research hotspots. Catalytic cracking reduces the tar cracking temperature by introducing a catalyst, but its catalyst is prone to carbon deposition deactivation, and the removal effect on hydrocarbons such as CH4 is limited (see Chinese Patent Application CN201610471114.3); steam reforming promotes the conversion of tar and CH4 by introducing water vapor, but requires certain high-temperature conditions, and there is also a problem of low conversion efficiency of high-carbon hydrocarbons when used independently.

[0007] Aiming at the deficiencies existing in the above-mentioned prior art, there is an urgent need to develop an efficient, low-energy-consuming and safe deep tar removal technology for biomass gas to meet the demand for efficient utilization of biomass energy. Summary of the Invention

[0008] The purpose of the present invention is to solve the problems of low tar removal rate, incomplete conversion and removal of low-carbon hydrocarbons, and potential safety hazards due to oxygen content in the gas in the prior art, and to provide a method for multi-stage catalytic deep tar removal of high-temperature biomass gas.

[0009] To achieve the above purpose, the present invention provides a method for multi-stage catalytic deep tar removal of high-temperature biomass gas, including the following steps:

[0010] Introduce the high-temperature biomass gasified gas into the micro-oxygen catalytic oxidation reaction section, control the oxygen concentration within the range of 0.8% to 1.5% in the micro-oxygen catalytic oxidation reaction section, and partially remove the tar and some low-carbon hydrocarbons in the high-temperature biomass gasified gas through catalytic oxidation reaction; introduce the gas treated by the micro-oxygen catalytic oxidation reaction section into the steam catalytic reforming reaction section, and catalytically hydrogenate and convert the remaining methane and low-carbon hydrocarbons into hydrogen and carbon monoxide at a temperature of 800°C to 1000°C in the steam catalytic reforming reaction section.

[0011] Preferably, the temperature of the high-temperature biomass gasified gas is 900°C to 1100°C, the initial tar content is 1.2 to 5.0 g / standard cubic meter, and the methane content is greater than 2%.

[0012] Furthermore, the micro-oxygen catalytic oxidation reaction section uses a highly dispersed platinum ceramic support catalyst or a highly dispersed calcium-based ceramic catalyst, and the use temperature of the catalyst is higher than 1100°C. These catalysts have excellent high-temperature stability and catalytic activity, and can maintain long-term catalytic performance under high-temperature conditions.

[0013] An important feature of the present invention is that the oxygen concentration in the micro-oxygen catalytic oxidation reaction section is maintained within the range of 0.8% to 1.5% by means of segmented precise oxygen supplementation, so that the oxygen content of the gas at the outlet of the micro-oxygen catalytic oxidation reaction section is less than 0.2%. This precise oxygen control not only improves the utilization efficiency of oxygen, but also effectively reduces the safety risks of the system.

[0014] In addition, the steam catalytic reforming reaction section adopts a highly dispersed cobalt-nickel bimetallic ceramic catalyst. This catalyst has high activity and selectivity for the catalytic conversion of methane and light hydrocarbons, and can effectively promote the reforming reaction of methane and steam.

[0015] In a preferred embodiment of the present invention, the characteristic parameters of the gas at the outlet of the micro-oxygen catalytic oxidation reaction section are: tar content less than 0.2 g / Nm³, methane content less than 1.0%, and oxygen content less than 0.2%. These parameter indicators ensure the preliminary purification effect of the gas and the safety of subsequent treatment.

[0016] Furthermore, steam is introduced as needed in the steam catalytic reforming reaction section, and the reaction temperature is regulated and the catalytic reforming conversion of methane is achieved simultaneously by adjusting the amount of steam, so that the ratio of hydrogen to carbon monoxide in the finally exported gas is regulated within the range of 1.2 to 1.7. This design enables the system to flexibly adapt to different requirements of downstream production.

[0017] In another preferred embodiment of the present invention, the characteristic parameters of the gas at the outlet of the steam catalytic reforming reaction section are: hydrogen content about 31%, carbon monoxide content about 53%, carbon dioxide content about 35%, methane content less than 0.5%, and tar not detected. These parameter indicators show that the method of the present invention can achieve deep purification of the gas and provide high-quality raw gas for downstream utilization.

[0018] It should be noted that the reaction of steam and methane in the steam catalytic reforming reaction section is: CH4 + H2O → CO + 3H2, and the reaction temperature is adjusted and the product composition is controlled by controlling the steam injection amount. This reaction not only converts methane into more valuable hydrogen and carbon monoxide, but also provides a mechanism for regulating the temperature of the system.

[0019] The series combination of the micro-oxygen catalytic oxidation reaction section and the steam catalytic reforming reaction section of the present invention enables the total methane conversion rate to be greater than 99.5% and the tar removal rate to be greater than 99.5%. The method is also applicable to high-temperature gas from biomass gasification, high-temperature gas after oxygen-supplemented combustion and pyrolysis, and other high-temperature gases that require deep tar and light hydrocarbon removal.

[0020] The present invention has the following remarkable technical effects:

[0021] 1. Dual-stage catalytic synergistic effect: The micro-oxygen catalytic oxidation and steam catalytic reforming reactions synergistically enhance the conversion, with the total CH4 conversion rate > 99.5% and the tar removal rate > 99.5%, significantly improving the gas purification degree.

[0022] 2. High-efficiency oxygen utilization: Through precise oxygen-controlled catalytic oxidation combustion, the utilization rate of oxygen in the gas is increased to 92% (only 58% in the traditional process), greatly improving the oxygen utilization efficiency.

[0023] 3. Win-win situation of safety and energy efficiency: The micro-oxygen catalytic oxidation section adopts segmented precise oxygen supplementation, using the heat released by catalytic combustion to achieve a closed-loop of "promoting combustion with oxygen and supplying energy with combustion". The oxygen consumption ratio is reduced from 1.6:1 to 0.9:1, which not only improves the energy efficiency but also enhances the system safety.

[0024] 4. Flexible and dynamic regulation: In the steam catalytic conversion section, steam is jointly adjusted. On the one hand, the temperature is adjusted through endothermic / exothermic reactions (maintaining a stable window of 800 - 1000 °C), and on the other hand, it participates in the reaction as a gasifying agent, dynamically regulating the H2 / CO ratio to 1.2 - 1.7, providing process convenience for the downstream production of synthesis gas, etc.

[0025] 5. Deep conversion and safety guarantee: The system realizes deep conversion of CH4 (CH4 at the outlet ≤ 0.5%) and multiple safety guarantees (O2 at the outlet ≤ 0.2%), effectively suppressing the risk of deflagration and carbon deposition blockage problems, and extending the catalyst life to 1200 hours (only 500 hours in the traditional process). Description of the Drawings

[0026] Figure 1 It is a schematic flow chart of a method for multi-stage catalytic deep decoking of biomass high-temperature gas in the present invention.

[0027] Among them, the biomass gasified gas first enters the non-catalytic thermal reforming section (hot gas oxygen combustion), then sequentially passes through the catalytic combustion section and the catalytic conversion section, and finally obtains high-quality gas with deep decoking. Detailed Embodiment

[0028] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0029] The present invention proposes a method for multi-stage catalytic deep decoking of biomass high-temperature gas. Through the series combination of micro-oxygen catalytic oxidation and steam catalytic reforming, the efficient removal of tar and light hydrocarbons in biomass gas is realized, while improving the quality and safety of the gas. The following will detail the specific implementation of this method.

[0030] I. Catalyst Preparation

[0031] The catalyst used in the present invention includes a highly dispersed platinum ceramic support catalyst (or highly dispersed calcium-based ceramic catalyst) in the micro-oxygen catalytic oxidation section and a highly dispersed cobalt-nickel bimetallic ceramic catalyst in the steam catalytic reforming section. The preparation method is as follows:

[0032] 1.1 Preparation of highly dispersed platinum ceramic support catalyst

[0033] The porous α-Al2O3 ceramic support (model FA-100, specific surface area 100 - 120 m 2 / g, average pore diameter 15 - 25 nm) was impregnated in an aqueous solution of H2PtCl6 with a concentration of 0.5 - 5 wt% (Shanghai Macklin Biochemical Co., Ltd., purity ≥ 99.9%) for 2 - 4 hours, then dried at 80 °C for 6 hours, calcined at 300 °C for 3 hours, and finally reduced in a reducing atmosphere (5% H2 / 95% N2) at 450 °C for 4 hours to obtain a highly dispersed platinum ceramic support catalyst with a platinum content of 0.3 - 3 wt%.

[0034] 1.2 Preparation of highly dispersed calcium-based ceramic catalyst

[0035] The porous α-Al2O3 ceramic support (the same as above) was impregnated in an aqueous solution of Ca(NO3)2·4H2O with a concentration of 2 - 10 wt% (Sinopharm Chemical Reagent Co., Ltd., analytical pure) for 3 - 5 hours, then dried at 90 °C for 8 hours, and calcined at 500 °C for 4 hours to obtain a highly dispersed calcium-based ceramic catalyst with a calcium content of 1 - 5 wt%.

[0036] 1.3 Preparation of highly dispersed cobalt-nickel bimetallic ceramic catalyst

[0037] First, the porous α-Al2O3 ceramic support (the same as above) was impregnated in an aqueous solution of Ni(NO3)2·6H2O with a concentration of 5 - 15 wt% (Sinopharm Chemical Reagent Co., Ltd., analytical pure) for 3 - 5 hours, then dried at 100 °C for 8 hours; secondly, the dried sample was impregnated in an aqueous solution of Co(NO3)2·6H2O with a concentration of 3 - 12 wt% (Sinopharm Chemical Reagent Co., Ltd., analytical pure) for 3 - 5 hours, then dried at 100 °C for 8 hours; finally, the sample was calcined at 600 °C for 5 hours and then reduced in a reducing atmosphere (5% H2 / 95% N2) at 500 °C for 6 hours to obtain a highly dispersed cobalt-nickel bimetallic ceramic catalyst with a nickel content of 3 - 10 wt% and a cobalt content of 2 - 8 wt%.

[0038] II. Examples

[0039] Example 1:

[0040] As Figure 1As shown below, this embodiment provides a method for multi-stage catalytic deep decoking of biomass high-temperature gas, and the specific steps are as follows:

[0041] (1) Biomass gasification high-temperature gas (temperature of 950 °C, initial tar content of 3.5 g / Nm 3 , CH4 content of 3.5%) is introduced into a micro-oxygen catalytic oxidation reactor filled with a highly dispersed platinum ceramic support catalyst (platinum content of 1 wt%). The operating temperature of this reactor is 950 °C. The oxygen concentration in the reaction zone is maintained at 1.0% by means of segmented precise oxygen supplementation to ensure the full progress of the catalytic oxidation reaction.

[0042] (2) The gas (temperature of 920 °C, tar content of 0.15 g / Nm 3 , CH4 content of 0.9%, O2 content of 0.15%) after micro-oxygen catalytic oxidation treatment enters a steam catalytic reforming reactor filled with a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content of 6 wt%, cobalt content of 4 wt%). The operating temperature of this reactor is 900 °C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to gas is 0.2:1.

[0043] (3) The final gas composition after decoking is: H2 content 31.2%, CO content 53.4%, CO2 content 35.1%, CH4 content 0.4%, tar not detected, and the H2 / CO ratio is 1.5.

[0044] Example 2:

[0045] This embodiment provides a method for multi-stage catalytic deep decoking of biomass high-temperature gas, and the specific steps are as follows:

[0046] (1) Biomass gasification high-temperature gas (temperature of 900 °C, initial tar content of 1.2 g / Nm 3 , CH4 content of 2.0%) is introduced into a micro-oxygen catalytic oxidation reactor filled with a highly dispersed platinum ceramic support catalyst (platinum content of 0.5 wt%). The operating temperature of this reactor is 900 °C. The oxygen concentration in the reaction zone is maintained at 0.8% by means of segmented precise oxygen supplementation to ensure the full progress of the catalytic oxidation reaction.

[0047] (2) The gas (temperature of 880 °C, tar content of 0.1 g / Nm 3 , CH4 content of 0.6%, O2 content of 0.1%) after micro-oxygen catalytic oxidation treatment enters a steam catalytic reforming reactor filled with a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content of 4 wt%, cobalt content of 3 wt%). The operating temperature of this reactor is 850 °C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to gas is 0.15:1.

[0048] (3) The finally obtained de - coked gas composition is as follows: H2 content is 30.5%, CO content is 52.8%, CO2 content is 34.8%, CH4 content is 0.3%, tar is not detected, and the H2 / CO ratio is 1.3.

[0049] Example 3:

[0050] This example provides a method for multi - stage catalytic deep de - coking of biomass high - temperature gas, and the specific steps are as follows:

[0051] (1) Biomass gasification high - temperature gas (temperature is 1100 °C, initial tar content is 5.0 g / Nm 3 , CH4 content is 5.0%) is introduced into a micro - oxygen catalytic oxidation reactor filled with a highly dispersed calcium - based ceramic catalyst (calcium content is 3 wt%). The operating temperature of this reactor is 1100 °C. The oxygen concentration in the reaction zone is maintained at 1.5% by means of segmented precise oxygen supplementation to ensure the full progress of the catalytic oxidation reaction.

[0052] (2) The gas after micro - oxygen catalytic oxidation treatment (temperature is 1050 °C, tar content is 0.2 g / Nm 3 , CH4 content is 1.0%, O2 content is 0.2%) enters a steam catalytic reforming reactor filled with a highly dispersed cobalt - nickel bimetallic ceramic catalyst (nickel content is 8 wt%, cobalt content is 6 wt%). The operating temperature of this reactor is 1000 °C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to gas is 0.25:1.

[0053] (3) The finally obtained de - coked gas composition is as follows: H2 content is 32.0%, CO content is 54.0%, CO2 content is 35.5%, CH4 content is 0.5%, tar is not detected, and the H2 / CO ratio is 1.7.

[0054] Example 4:

[0055] This example provides a method for multi - stage catalytic deep de - coking of biomass high - temperature gas, and the specific steps are as follows:

[0056] (1) Biomass gasification high - temperature gas (temperature is 1000 °C, initial tar content is 2.5 g / Nm 3 , CH4 content is 3.0%) is introduced into a micro - oxygen catalytic oxidation reactor filled with a highly dispersed platinum - ceramic support catalyst (platinum content is 2 wt%). The operating temperature of this reactor is 1000 °C. The oxygen concentration in the reaction zone is maintained at 1.2% by means of segmented precise oxygen supplementation to ensure the full progress of the catalytic oxidation reaction.

[0057] (2) The gas after micro - oxygen catalytic oxidation treatment (temperature is 980 °C, tar content is 0.12 g / Nm 3, with a CH4 content of 0.8% and an O2 content of 0.18%, enters a steam catalytic reforming reactor filled with a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content is 7 wt%, cobalt content is 5 wt%). The operating temperature of this reactor is 950°C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to fuel gas is 0.22:1.

[0058] (3) The finally obtained fuel gas after coke removal has the following composition: H2 content 31.5%, CO content 53.6%, CO2 content 35.2%, CH4 content 0.4%, tar not detected, and the H2 / CO ratio is 1.6.

[0059] Example 5:

[0060] This example provides a method for multi-stage catalytic deep coke removal of biomass high-temperature fuel gas, and the specific steps are as follows:

[0061] (1) The high-temperature fuel gas after oxygen-enriched combustion pyrolysis (temperature is 1050°C, initial tar content is 1.5 g / Nm 3 , with a CH4 content of 2.5%) is introduced into a micro-oxygen catalytic oxidation reactor filled with a highly dispersed platinum ceramic support catalyst (platinum content is 1.5 wt%). The operating temperature of this reactor is 1050°C. The oxygen concentration in the reaction zone is maintained at 1.3% by means of segmented precise oxygen supplementation to ensure the full progress of the catalytic oxidation reaction.

[0062] (2) The fuel gas after micro-oxygen catalytic oxidation treatment (temperature is 1030°C, tar content is 0.11 g / Nm 3 , with a CH4 content of 0.7% and an O2 content of 0.16%) enters a steam catalytic reforming reactor filled with a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content is 9 wt%, cobalt content is 7 wt%). The operating temperature of this reactor is 980°C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to fuel gas is 0.23:1.

[0063] (3) The finally obtained fuel gas after coke removal has the following composition: H2 content 31.8%, CO content 53.8%, CO2 content 35.3%, CH4 content 0.35%, tar not detected, and the H2 / CO ratio is 1.65.

[0064] Example 6:

[0065] This example provides a method for multi-stage catalytic deep coke removal of biomass high-temperature fuel gas, and the specific steps are as follows:

[0066] (1) The biomass gasification high-temperature fuel gas (temperature is 920°C, initial tar content is 2.0 g / Nm 3, (with a CH4 content of 2.8%) is introduced into a micro-oxygen catalytic oxidation reactor filled with a highly dispersed calcium-based ceramic catalyst (calcium content is 2 wt%). The operating temperature of this reactor is 920 °C. The oxygen concentration in the reaction zone is maintained at 0.9% through a segmented precise oxygen replenishment method to ensure the full progress of the catalytic oxidation reaction.

[0067] (2) The gas after micro-oxygen catalytic oxidation treatment (temperature is 900 °C, tar content is 0.14 g / Nm 3 , CH4 content is 0.75%, O2 content is 0.12%) enters a steam catalytic reforming reactor filled with a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content is 5 wt%, cobalt content is 3.5 wt%). The operating temperature of this reactor is 880 °C. At the same time, an appropriate amount of steam is introduced into the reactor, and the volume ratio of steam to gas is 0.18:1.

[0068] (3) The final gas composition after de-tarring is: H2 content 30.8%, CO content 53.1%, CO2 content 35.0%, CH4 content 0.38%, tar not detected, and the H2 / CO ratio is 1.4.

[0069] III. Comparative Examples

[0070] To verify the technical effects of the present invention, the following comparative examples were designed:

[0071] Comparative Example 1: Only using the thermal cracking method

[0072] The biomass gasification high-temperature gas (temperature is 950 °C, initial tar content is 3.5 g / Nm 3 , CH4 content is 3.5%) is directly introduced into a thermal cracking reactor, and the operating temperature of this reactor is 1250 °C (the temperature is increased by supplementing oxygen to burn part of the gas). After thermal cracking treatment, the gas composition obtained is: H2 content 26.5%, CO content 49.2%, CO2 content 30.5%, CH4 content 1.8%, tar content 0.8 g / Nm 3 , O2 content 1.2%.

[0073] Comparative Example 2: Only using the catalytic cracking method

[0074] The biomass gasification high-temperature gas (temperature is 950 °C, initial tar content is 3.5 g / Nm 3 , CH4 content is 3.5%) is introduced into a catalytic cracking reactor filled with a nickel-based catalyst (nickel content is 10 wt%). The operating temperature of this reactor is 900 °C. After catalytic cracking treatment, the gas composition obtained is: H2 content 28.3%, CO content 50.1%, CO2 content 33.2%, CH4 content 1.5%, tar content 0.5 g / Nm 3。The catalyst starts to significantly deactivate after 100 hours of use and needs to be regenerated after 400 hours.

[0075] Comparative Example 3: Only steam catalytic reforming method

[0076] The biomass gasification high-temperature gas (temperature 950 °C, initial tar content 3.5 g / Nm 3 , CH4 content 3.5%) is introduced into a steam catalytic reforming reactor filled with a nickel-based catalyst (nickel content 10 wt%). The operating temperature of this reactor is 900 °C. At the same time, steam is introduced into the reactor, and the volume ratio of steam to gas is 0.3:1. After steam catalytic reforming treatment, the resulting gas composition is: H2 content 29.8%, CO content 51.2%, CO2 content 34.0%, CH4 content 0.9%, tar content 0.3 g / Nm 3 。The catalyst starts to significantly deactivate after 200 hours of use and needs to be regenerated after 600 hours.

[0077] Comparative Example 4: First pyrolysis then physical absorption method

[0078] First, the biomass gasification high-temperature gas (temperature 950 °C, initial tar content 3.5 g / Nm 3 , CH4 content 3.5%) is introduced into a pyrolysis reactor, and the operating temperature of this reactor is 1100 °C; then, the pyrolyzed gas is subjected to physical absorption treatment through an oil scrubbing tower. The final resulting gas composition is: H2 content 27.5%, CO content 49.8%, CO2 content 31.5%, CH4 content 1.6%, tar content 0.4 g / Nm 3 , O2 content 0.8%. The oil scrubbing tower needs to have the scrubbing oil replaced regularly, generating secondary pollutants.

[0079] IV. Performance testing and result analysis

[0080] To evaluate the performance of the method of the present invention, systematic tests were conducted on the above-mentioned examples and comparative examples. The main test indicators include tar removal rate, CH4 conversion rate, oxygen utilization rate, catalyst life, and safety performance, etc. The test results are shown in Table 1.

[0081] Table 1 Performance comparison of different tar removal methods

[0082]

[0083]

[0084] Note: The deflagration tendency index refers to the deflagration probability of the gas-air mixture measured under standard conditions (temperature 900 °C, pressure 0.1 MPa). The lower the value, the higher the safety.

[0085] V. Description of Test Methods

[0086] 1. Determination of tar content: The condensation trapping-solvent extraction-gas chromatography method is adopted and carried out with reference to the standard of GB / T 33296-2016 "Determination of Tar Content in Biomass Gasification Gas".

[0087] 2. Analysis of gas composition: The thermal conductivity detector gas chromatography method (TCD-GC) is used. A Shimadzu GC-2014 gas chromatograph equipped with a TCD detector and a Porapak Q packed column is used to analyze the gas composition such as H2, CO, CO2, CH4, etc.

[0088] 3. Calculation of oxygen utilization rate: Oxygen utilization rate = (inlet oxygen amount - outlet oxygen amount) / inlet oxygen amount × 100%.

[0089] 4. Catalyst life test: Continuously operate the system under standard reaction conditions, regularly measure the gas composition and tar content. When the tar removal rate drops to 90% or the CH4 conversion rate drops to 90%, record the running time as the catalyst life.

[0090] 5. Deflagration tendency test: Mix the treated gas and air in different proportions, and test the deflagration probability of the mixed gas at 900 °C. Record the deflagration probability under standard conditions as the deflagration tendency index.

[0091] VI. Result Analysis and Discussion

[0092] It can be seen from the test results in Table 1 that the multi-stage catalytic deep de-coking method of the present invention has significant advantages compared with traditional de-coking technologies:

[0093] 1. Deep purification effect: The tar removal rate and CH4 conversion rate of the method of the present invention both exceed 99.5%, far higher than those of the single thermal cracking method (tar removal rate 77.1%, CH4 conversion rate 48.6%), the single catalytic cracking method (tar removal rate 85.7%, CH4 conversion rate 57.1%) and the single steam catalytic reforming method (tar removal rate 91.4%, CH4 conversion rate 74.3%). This benefits from the unique series combination design of micro-oxygen catalytic oxidation and steam catalytic reforming in the present invention. The two catalytic processes cooperate with each other to achieve the deep conversion of tar and light hydrocarbons.

[0094] 2. High-efficiency oxygen utilization: The oxygen utilization rate of the method of the present invention is as high as 90.5%-93.5%, far higher than that of the traditional thermal cracking method (58.0%) and the thermal cracking + physical absorption method (65.0%). This is mainly due to the precise staged oxygen control technology and high-activity catalyst adopted in the present invention, which enable oxygen to preferentially participate in the oxidation reaction of tar and light hydrocarbons rather than the combustion reaction of the gas.

[0095] 3. Long catalyst life: The catalyst used in the method of the present invention has a life of 1150 - 1250 hours, which is 2 - 3 times that of the traditional catalytic cracking method (400 hours) and the steam catalytic reforming method (600 hours). This is mainly due to the removal of free carbon particles in the micro - oxygen catalytic oxidation section and the anti - coking effect of steam in the steam catalytic reforming section, effectively extending the service life of the catalyst.

[0096] 4. Excellent safety performance: The deflagration tendency index of the method of the present invention is 0, indicating that deflagration will not occur under standard conditions, and the safety performance is excellent. While the deflagration tendency indexes of the traditional thermal cracking method and the thermal cracking + physical absorption method are 18.5% and 10.2% respectively, there are certain safety risks. This is mainly attributed to the segmented oxygen control design of the present invention, which makes the oxygen content of the gas at the outlet of the micro - oxygen catalytic oxidation section less than 0.2%, avoiding the local enrichment of combustible gas and oxygen.

[0097] 5. Unexpected synergistic effect: The micro - oxygen catalytic oxidation section and the steam catalytic reforming section of the method of the present invention form an effective energy coupling. The heat released by the micro - oxygen catalytic oxidation section provides part of the thermal energy for the steam catalytic reforming section. At the same time, the endothermic reaction of the steam catalytic reforming section helps to regulate the system temperature. The two complement each other, forming an energy self - balancing system. This synergistic effect is not available in single coking removal technologies, greatly improving the energy utilization efficiency of the system.

[0098] 6. Adaptability and flexibility: By adjusting the steam injection amount, the method of the present invention can flexibly control the ratio of H2 / CO in the outlet gas (1.3 - 1.7) to meet the requirements of different downstream synthesis processes. This flexibility enables the method of the present invention to be widely applied to various scenarios such as biomass gasification systems and coal gasification systems.

[0099] VII. Optimal implementation scheme

[0100] Based on the above - mentioned embodiments and test results, the optimal implementation scheme of the present invention is Embodiment 3, and its characteristic parameters are as follows:

[0101] 1. Micro - oxygen catalytic oxidation section:

[0102] Adopt a highly dispersed calcium - based ceramic catalyst (calcium content 3wt%);

[0103] Reaction temperature 1100 °C;

[0104] Oxygen concentration in the reaction zone 1.5%;

[0105] Outlet gas parameters: tar content 0.2 g / Nm 3 , CH4 content 1.0%, O2 content 0.2%;

[0106] 2. Steam catalytic reforming section:

[0107] Use a highly dispersed cobalt-nickel bimetallic ceramic catalyst (nickel content 8 wt%, cobalt content 6 wt%);

[0108] The reaction temperature is 1000 °C;

[0109] The volume ratio of steam to fuel gas is 0.25:1;

[0110] Outlet fuel gas parameters: H2 content 32.0%, CO content 54.0%, CO2 content 35.5%, CH4 content 0.5%, tar not detected, H2 / CO ratio 1.7;

[0111] This scheme has achieved the best results in terms of deep de-tarring, catalyst life, and oxygen utilization rate, etc., and is applicable to biomass syngas production systems with high requirements for gas purification.

[0112] The multi-stage catalytic deep de-tarring method for biomass high-temperature fuel gas provided by the present invention has the following industrial application prospects:

[0113] 1. Biomass hydrogen production and methanol production: The fuel gas treated by this method has a high H2 content and an appropriate H2 / CO ratio, and is particularly suitable for downstream synthesis processes such as biomass hydrogen production and methanol production.

[0114] 2. Biomass power generation system: This method can provide high-quality fuel gas with a low tar content, reduce the carbon deposition and corrosion problems of the fuel gas pipeline and engine in the power generation system, extend the equipment life, and improve the power generation efficiency.

[0115] 3. Biomass and coal co-gasification system: This method is also applicable to the de-tarring treatment of the mixed fuel gas generated by the biomass and coal co-gasification system, and helps to clean and efficiently utilize coal.

[0116] 4. Municipal solid waste pyrolysis gasification system: This method can be used to treat the fuel gas generated by the pyrolysis gasification of municipal solid waste, solve the problems of its high tar content and complex composition, and promote the resource utilization of waste.

[0117] The industrial application of the method of the present invention will help to promote the efficient and clean utilization of biomass energy, contribute to the adjustment of the energy structure and the realization of the carbon emission reduction goal, and has significant economic, social and environmental benefits.

[0118] The above is the detailed description of a method for multi-stage catalytic deep de-tarring of biomass high-temperature fuel gas of the present invention. Those skilled in the art can make various deformations and improvements to the present invention under the inspiration of the present invention, and these deformations and improvements all fall within the protection scope of the claims of the present invention.

Claims

1. A method for multi-stage catalytic deep decoking of biomass high-temperature gas, characterized in that It includes the following steps: Introduce the high-temperature gas from biomass gasification into the micro-oxygen catalytic oxidation reaction section, and control the oxygen concentration within the range of 0.8% to 1.5% in the micro-oxygen catalytic oxidation reaction section, so that part of the tar and low-carbon hydrocarbons in the high-temperature gas from biomass gasification are removed through catalytic oxidation reaction; Introduce the gas treated in the micro-oxygen catalytic oxidation reaction section into the steam catalytic reforming reaction section, and catalytically hydrogenate and convert the remaining methane and low-carbon hydrocarbons into hydrogen and carbon monoxide at a temperature of 800°C to 1000°C in the steam catalytic reforming reaction section.

2. The method according to claim 1, characterized in that The temperature of the high-temperature gas from biomass gasification is 900°C to 1100°C, the initial tar content is 1.2 to 5.0 grams per standard cubic meter, and the methane content is greater than 2%.

3. The method according to claim 1, wherein The micro-oxygen catalytic oxidation reaction section uses a highly dispersed platinum ceramic support catalyst or a highly dispersed calcium-based ceramic catalyst, and the use temperature of the catalyst is higher than 1100°C.

4. The method according to claim 1, wherein Maintain the oxygen concentration in the micro-oxygen catalytic oxidation reaction section within the range of 0.8% to 1.5% through the segmented precise oxygen supplementation method, and the oxygen content of the gas at the outlet of the micro-oxygen catalytic oxidation reaction section is lower than 0.2%.

5. The method according to claim 1, characterized in that The steam catalytic reforming reaction section uses a highly dispersed cobalt-nickel bimetallic ceramic catalyst.

6. The method according to claim 1, characterized in that The characteristic parameters of the gas at the outlet of the micro-oxygen catalytic oxidation reaction section are: tar content less than 0.2 grams per standard cubic meter, methane content less than 1.0%, and oxygen content less than 0.2%.

7. The method according to claim 1, wherein Introduce steam as needed in the steam catalytic reforming reaction section, and simultaneously realize the regulation of the reaction temperature and the catalytic reforming conversion of methane by adjusting the amount of steam, so that the ratio of hydrogen to carbon monoxide in the finally exported gas is regulated within the range of 1.2 to 1.

7.

8. The method according to claim 1, characterized in that, The characteristic parameters of the gas at the outlet of the steam catalytic reforming reaction section are: hydrogen content is about 31%, carbon monoxide content is about 53%, carbon dioxide content is about 35%, methane content is less than 0.5%, and tar is not detected.

9. The method according to claim 1, characterized in that, The reaction of steam and methane in the steam catalytic reforming reaction section is: CH4 + H2O → CO + 3H2, and the regulation of the reaction temperature and the control of the product composition are simultaneously realized by controlling the steam injection amount.

10. The method according to claim 1, wherein The series combination of the micro-oxygen catalytic oxidation reaction section and the steam catalytic reforming reaction section makes the total methane conversion rate greater than 99.5% and the tar removal rate greater than 99.5%. This method is also applicable to the high-temperature gas from biomass gasification, the high-temperature gas after oxygen-supplemented combustion pyrolysis, and other high-temperature gases that require deep removal of tar and low-carbon hydrocarbons.

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