A method for reforming volatile matter based on biomass pyrolysis semi-coke circulation

Abstract

This invention belongs to the field of biomass thermochemical conversion and resource utilization technology, specifically involving a volatile matter reforming method based on biomass pyrolysis semi-coke recycling. This invention introduces a staged condensation unit to achieve full-component capture of tar, and mixes the condensed tar with by-products from column separation and a gasifying agent, then uniformly feeds it into the semi-coke bed in the high-temperature reforming zone at a controllable flow rate, achieving homogenization of the pyrolysis feed and avoiding bed blockage. A column-based staged separation method is used to promptly remove high-purity target products from the reaction system, preventing reverse reactions in the high-temperature reforming zone and improving the yield and purity of the target products. Low-temperature, oxygen-deficient pyrolysis conditions are controlled to retain highly active sites in the semi-coke, and a closed-loop semi-coke recycling system is established to achieve the recycling and online regeneration of active sites, while simultaneously realizing the cascade utilization of energy within the system.

Description

Technical Field

[0001] This invention belongs to the field of biomass thermochemical conversion and resource utilization technology, specifically relating to a volatile reforming method based on the semi-coke cycle of biomass pyrolysis. Background Technology

[0002] Biomass, as the world's most abundant renewable carbon-based resource, has been widely used in clean fuel preparation, carbon-based functional material production, and green chemical synthesis. With the increasingly urgent need for the harmless disposal of agricultural and forestry waste in my country, and the rapid expansion of the renewable clean energy market, the demand for large-scale and industrial applications of biomass pyrolysis gasification technology is showing a continuous growth trend. In the field of biomass pyrolysis gasification technology, traditional processes have the following technical problems: First, there is a contradiction between pyrolysis temperature and gasification temperature in traditional single-stage gasifiers. If the reaction temperature is too high (>900℃), although it is beneficial for tar cracking, it will lead to excessive gasification of semi-coke, significantly reducing the char yield; if the temperature is too low, tar cracking will be incomplete, and a large amount of residual tar will condense and form scale in subsequent stages. Second, traditional nickel-based and precious metal catalysts used in biomass pyrolysis gasification are expensive and easily poisoned. High-efficiency catalytic reforming technology relies on these expensive metal catalysts, which not only require large initial investments but are also easily poisoned by impurities such as sulfur and chlorine in the raw materials or rapidly deactivated due to carbon deposition. Regeneration is difficult and costly, making it difficult to meet the requirements of long-term industrial operation.

[0003] To address the aforementioned problems with traditional processes, Chinese patent CN106590705A discloses a method for producing in-situ composite semi-coke secondary reforming tar using high-alkali coal and biomass. This method utilizes the pyrolysis of low-quality high-alkali coal and biomass to prepare in-situ hot composite semi-coke as a catalyst. The tar produced from the upper pyrolysis layer is then subjected to secondary catalytic reforming in a two-stage fixed-bed reactor. Chinese patent CN117660029A discloses a biomass pyrolysis device and method, providing a two-stage device that uses microwaves to heat biomass at low temperatures (300-500℃) to generate volatiles. The gaseous products are then passed through a high-temperature carbon ash layer in a downdraft moving bed to complete steam reforming and secondary pyrolysis of the tar. While these existing technologies propose improvements based on the problems of traditional processes, they still suffer from the following three shortcomings in practical applications:

[0004] (1) Unstable tar cracking and bed blockage: The above-mentioned existing technology uses pyrolysis gas to directly pass through the hot coke bed for cracking, which lacks a buffer regulation mechanism. When the raw material fluctuation causes the instantaneous tar concentration to be too high, it is easy to cause local adsorption saturation of the bed, resulting in rapid carbon accumulation and blockage. In addition, the unconverted tar will directly enter the downstream, and it is impossible to guarantee that the tar content at the outlet meets the standard.

[0005] (2) Low yield and insufficient purity of target products, and weak product control capability: The main products of the above-mentioned existing technical solutions are crude syngas (mainly H2 and CO). Due to the lack of product separation and removal mechanism, the generated hydrogen is easily consumed by participating in the reverse water-gas conversion reaction, and the generated methane is easily reformed and cracked in the high-temperature bed, resulting in low purity of H2 and CH4 in the final gas, and it is difficult to flexibly control the product ratio according to market demand.

[0006] (3) Loss of active sites in semi-coke and continuous deactivation of catalyst: In the CN106590705A scheme, the reaction temperature in the lower layer is as high as 500-900℃, which may lead to the premature loss of some key active sites (such as persistent free radicals); and the semi-coke flows in one direction, and is discharged or repurposed after use, so the active sites are consumed at once, and the system needs to be continuously replenished with new materials. In the CN117660029A scheme, its carbon ash layer mainly relies on high-temperature physical cracking and passive catalysis of some residual minerals, and lacks a deliberate retention and circulation enhancement mechanism for active sites in semi-coke (such as free radicals), which leads to the decay of catalytic efficiency over time. Summary of the Invention

[0007] To address the shortcomings of the existing technologies, the technical problem to be solved by this invention is to provide a volatile reforming method based on the recycling of biomass pyrolysis semi-coke: introducing a buffer regulation mechanism to achieve homogenization of the pyrolysis feed and avoid bed blockage; designing a product separation and removal mechanism to improve the yield and purity of the target product; controlling the pyrolysis conditions to retain the high-activity sites of the semi-coke, and establishing a closed-loop recycling system for the semi-coke to achieve the recycling and online regeneration of the active sites, while realizing the cascade utilization of energy within the system.

[0008] The technical solution adopted in this invention is as follows:

[0009] A volatile matter reforming method based on biomass pyrolysis semi-coke cycle includes the following steps:

[0010] Step S1: After pretreatment, the biomass raw material is fed into the low-temperature pyrolysis zone of the thermal reactor for low-temperature oxygen-deficient pyrolysis to obtain pyrolytic semi-coke and volatile matter containing tar; the low-temperature oxygen-deficient pyrolysis temperature is 300-400℃, and the oxygen volume fraction of the system is 1-4 vol%.

[0011] Preferably, in step S1, the step of feeding the pretreated biomass raw material into the low-temperature pyrolysis zone of the thermal reactor specifically includes:

[0012] The lignocellulosic biomass raw material is crushed to a particle size of 0.5-5 mm, dried to a moisture content of 8-12 wt%, and then sent to a low-temperature pyrolysis zone; wherein, the lignocellulosic biomass includes at least one of agricultural and forestry waste and organic biomass solid waste.

[0013] Preferably, in step S1, the low-temperature oxygen-deficient pyrolysis also has the following reaction parameters set as follows: solid phase biomass residence time is 45-60 min, gas phase volatile matter residence time is <2 s, and system pressure is a slight negative pressure of -80 to -120 Pa.

[0014] Step S2: The tar-containing volatiles obtained in step S1 are sent to a condensation unit for step-by-step condensation to achieve gas-liquid separation and obtain condensed tar and crude fuel gas respectively.

[0015] Preferably, in step S2, the stepwise condensation treatment adopts a two-stage condensation method, with the first-stage condensation temperature being 180–220℃ and the second-stage condensation temperature being 50–70℃, the total tar condensation collection rate being ≥95%, and the residual amount of gaseous tar after condensation being ≤30mg / Nm³. 3 .

[0016] Step S3: The crude gas obtained in step S2 is fed into a column separator for graded separation to enrich the target product and separate by-product components.

[0017] Preferably, in step S3, the column separation device is a multi-tower series pressure swing adsorption column separation system, and the adsorbent is at least one of 13X molecular sieve, activated carbon molecular sieve, and ZIFs porous material; the operating temperature of the fractionation separation process is 30-40℃, and the operating pressure is 0.5-0.8MPa; the target product includes at least one of H2 with a purity ≥95 vol% and CH4 with a purity ≥90 vol%.

[0018] Step S4: The pyrolysis semi-coke obtained in step S1 is fed into a high-temperature reforming zone to form a semi-coke bed.

[0019] Preferably, in step S4, the reaction parameters of the high-temperature reforming zone are set as follows: reaction temperature 750-850℃, semi-coke bed height 1-1.5m, residence time of gaseous material in the semi-coke bed 2-3s, and residence time of the pyrolytic semi-coke in the reforming zone 70-90min.

[0020] Step S5: The condensed tar obtained in step S2, the by-product components obtained in step S3, and the gasifying agent and reaction promoter are mixed and sent to the high-temperature reforming zone. The volatile matter reforming and tar cracking reaction are completed through the semi-coke bed obtained in step S4. The hydrogen-rich gas produced by the reaction is fed into the condensation unit for recycling.

[0021] Preferably, in step S5, the gasifying agent includes at least one of water vapor and CO2, and the mass ratio of the gasifying agent to the condensed tar is 1 to 2:1; and / or, the reaction promoter includes at least one of dolomite, olivine, and iron-based modifier, and the amount added is 0 to 2.5 wt% of the biomass raw material.

[0022] Step S6: The semi-coke in the semi-coke bed after the high-temperature reforming reaction in step S5 is recycled back to the low-temperature pyrolysis zone after heat exchange regulation, serving as a heat carrier and reaction aid, forming a closed-loop semi-coke recycling system.

[0023] The surplus semi-coke produced during low-temperature oxygen-deficient pyrolysis and high-temperature reforming processes can be modified and sold as carbon-based products, enabling flexible control of the output ratio of solid and gaseous products.

[0024] Preferably, in step S6, the mass ratio of the recycled semi-coke to the fresh biomass feed in the low-temperature pyrolysis zone is 0.8–1.2:1; and the spin concentration of persistent free radicals (PFRs) in the recycled semi-coke is 10. 16 ~10 19 spin / g has its surface enriched with alkali metals such as K, Na, Ca, and Mg, as well as alkaline earth metals (AAEMs) catalytic elements.

[0025] Step S7: The unused portion of the by-products obtained from column separation in step S3 and the tail gas that was not condensed after the reforming reaction in step S5 are collected and burned. The heat generated by combustion is used to supply the reaction heat demand of the low-temperature pyrolysis zone and the high-temperature reforming zone to achieve the self-heating balance of the system. The tail gas generated by combustion is purified and then discharged in compliance with standards.

[0026] The apparatus for implementing the above-mentioned volatile matter reforming method based on biomass pyrolysis semi-coke cycle includes an integrated vertical thermal reactor, a pretreatment unit, a staged condensation unit, a column-type separation unit, a semi-coke cycle unit, a waste heat utilization and tail gas treatment unit, and an automated control unit.

[0027] The integrated vertical thermal reactor is a sealed, pressure-resistant vertical furnace body. The interior is divided into three functional chambers from top to bottom: a low-temperature pyrolysis zone, an isolated feeding zone, and a high-temperature reforming zone. The low-temperature pyrolysis zone corresponds to the low-temperature, oxygen-deficient pyrolysis process in step S1, achieving low-temperature, oxygen-deficient pyrolysis of biomass raw materials to directionally prepare pyrolysis semi-coke rich in active sites and tar-containing volatiles. Simultaneously, a micro-negative pressure environment facilitates the rapid extraction of volatiles. The isolated feeding zone connects the low-temperature pyrolysis zone and the high-temperature reforming zone, corresponding to the pyrolysis semi-coke conveying process in steps S1 and S4. After the low-temperature, oxygen-deficient pyrolysis is completed, the discharge valve is opened, and the pyrolysis semi-coke naturally falls into the high-temperature reforming zone. The high-temperature reforming zone corresponds to the volatile matter reforming and tar cracking processes in steps S4 and S5, completing the in-situ catalytic cracking of tar and the volatile matter reforming reaction. The pretreatment unit corresponds to the raw material pretreatment process in step S1, achieving continuous, sealed, and quantitative feeding of raw materials. The staged condensation unit corresponds to the gas-liquid separation process in step S2, achieving the capture of all tar components and efficient gas-liquid separation. The column separation unit corresponds to the product classification separation process in step S3, enabling the early removal of target products and preventing their consumption due to reverse reactions in the high-temperature zone. The semi-coke recycling unit corresponds to the closed-loop semi-coke recycling process in step S6, achieving the recycling of active sites in the semi-coke and the tiered utilization of system energy. The waste heat utilization and tail gas treatment unit corresponds to the heat recovery and tail gas treatment process in step S7. The automated control unit is used to realize the real-time acquisition, closed-loop control, and safety interlock protection of all process parameters, ensuring continuous and stable operation of the entire process.

[0028] The beneficial effects obtained by adopting the above technical solution are as follows:

[0029] (1) The method of the present invention sends the volatiles generated by low-temperature oxygen-deficient pyrolysis into a step-by-step condensation unit (first stage 180-220℃, capturing heavy tar components; second stage 50-70℃, capturing light tar components) to achieve the capture of all components of tar ≥95%; then, the condensed tar is mixed with the by-product components (CO, light hydrocarbons, etc.) after column separation and the gasifying agent, and uniformly fed into the semi-coke bed of the high-temperature reforming zone at a controllable flow rate, thereby achieving homogeneous and stable feed, eliminating the instantaneous peak of tar concentration caused by raw material fluctuations, and avoiding local adsorption saturation and rapid carbon buildup blockage of the bed.

[0030] (2) The present invention adopts a column-type fractional separation method and sets up a multi-tower series pressure swing adsorption column separation device (adsorbents include 13X molecular sieve, ZIFs, etc.) to directly separate H2 with a purity ≥95 vol% and CH4 with a purity ≥90 vol% from crude gas. The high-purity target product is removed from the reaction system in a timely manner, avoiding reverse reaction (such as methane cracking and hydrogen consumption) in the high-temperature reforming zone. Moreover, the remaining by-product components (CO, CO2, etc.) are used as reforming feedstock and fed into the semi-coke bed to further convert into the target product. In the end, the yield and purity of the target product are improved, and the H2 / CH4 production ratio can be flexibly adjusted by adjusting the separation parameters to meet different market demands.

[0031] (3) This invention maximizes the retention of persistent free radicals (PFRs) on the surface of the semi-coke by strictly controlling the parameters of the low-temperature pyrolysis zone (300-400℃, oxygen content 1-4 vol%). 6 ~10¹ 9 The system utilizes active sites of alkali metals (Spin / g) and alkaline earth metals (AAEMs) to prevent activity quenching caused by high temperatures. Simultaneously, a closed-loop semi-coke recycling system is constructed, where the semi-coke after high-temperature reforming is circulated back to the low-temperature pyrolysis zone as a heat carrier and reaction aid after heat exchange regulation. The mass ratio of recycled semi-coke to fresh biomass is controlled at 0.8–1.2:1, forming a dynamically renewed active bed, achieving the recycling and online regeneration of active sites. Furthermore, the sensible heat carried by the recycled semi-coke is used to supply low-temperature pyrolysis, realizing the cascaded utilization of energy within the system. Attached Figure Description

[0032] Figure 1 This is a system flow diagram of the volatile matter reforming method based on the semi-coke cycle of biomass pyrolysis according to the present invention.

[0033] Figure 2 This is a block diagram showing the product flow of the volatile matter reforming method based on the semi-coke cycle of biomass pyrolysis according to the present invention.

[0034] Figure 3 This is a schematic diagram of the adsorption of volatiles in the porous semi-coke pores in this invention.

[0035] Figure 4 This is a schematic diagram of the reforming reaction of tar on the active sites of porous semi-coke surface in this invention. Detailed Implementation

[0036] The technical solution of the present invention will now be described more clearly and completely with reference to the accompanying drawings.

[0037] The core equipment used in this invention is an integrated thermal reactor. The furnace body is divided into two functional zones connected in series: the upper zone is a low-temperature pyrolysis zone, and the lower zone is a high-temperature reforming zone. A gravity feeding device and a heat exchange unit are installed between the two zones. Supporting components include a pretreatment unit, a two-stage progressive condensation unit, a multi-tower series pressure swing adsorption column separation unit, a semi-coke circulation conveying unit, and a heat recovery and tail gas treatment unit. The specific implementation steps are as follows:

[0038] 1. Select lignocellulosic biomass raw materials, including any one or more combinations of agricultural and forestry waste (corn stalks, wheat stalks, sawdust, bamboo shavings, fruit shells, cotton stalks, etc.) and organic biomass solid waste (edible fungus residue, furfural residue, papermaking black liquor solids, kitchen waste organic dry base, etc.). Use a hammer mill to crush the raw materials to a particle size of 0.5-5mm, and then send them to a forced-air drying oven to dry them, controlling the moisture content of the raw materials to be 5-15wt%. After pretreatment, send them to a sealed silo for later use.

[0039] 2. The pretreated biomass feedstock is continuously fed into the upper low-temperature pyrolysis zone of the integrated thermal reactor via a screw feeder for low-temperature, oxygen-deficient pyrolysis. The method parameters are controlled as follows: pyrolysis temperature 300–400℃, oxygen volume fraction 0.5–3 vol% (precisely controlled by a combination of high-purity nitrogen carrier gas and trace amounts of air), residence time of solid biomass in the pyrolysis zone 30–90 min, residence time of gaseous volatiles <2 s, and the system is maintained at a slight negative pressure environment of -50 to -200 Pa by an induced draft fan.

[0040] In this step, hemicellulose, cellulose, and lignin in biomass undergo stepwise pyrolysis at low temperatures, while long-chain aliphatic hydrocarbons complete deoxygenation, decarboxylation, and cyclization reactions. On one hand, volatiles containing tar and combustible gases are generated and continuously discharged through the gas outlet at the top of the furnace. The slightly negative pressure environment ensures that the volatiles quickly leave the pyrolysis zone, avoiding secondary pyrolysis to generate carbon black. On the other hand, pyrolysis semi-coke with a well-developed porous structure and rich in persistent free radicals (PFRs) and AAEMs catalytic elements is directionally prepared, with a specific surface area of ​​50–300 m². 2 / g, porosity 40-65%, porous framework structure as follows Figure 3 As shown, this provides a core carrier for subsequent volatile matter adsorption and reforming reactions. The pyrolysis semi-coke is continuously fed into the high-temperature reforming zone below via a gravity feeding device inside the furnace.

[0041] 3. The tar-containing volatiles extracted from the low-temperature pyrolysis zone are sent to a two-stage condensation unit for condensation treatment using a shell-and-tube condenser. The first-stage condensation temperature is controlled at 180–220℃ to capture the heavy tar components; the second-stage condensation temperature is controlled at 50–100℃ to capture the light tar components, achieving efficient gas-liquid separation of tar and crude fuel gas. This step can achieve a total tar condensation capture rate of ≥95%, and the residual tar in the gas phase after condensation is ≤30mg / Nm³. 3 The condensed liquid tar is sent to a sealed buffer tank, while the crude gas is discharged from the top of the secondary condenser and sent to the subsequent column separation unit.

[0042] 4. The crude gas obtained from condensation is fed into a multi-tower series pressure swing adsorption (PSA) column separation system. The system is filled with at least one of 13X molecular sieve, activated carbon molecular sieve, and ZIFs porous materials as adsorbents. The separation operation temperature is controlled at 25-60℃ and the operation pressure is 0.2-1.2MPa.

[0043] Target products such as H2 and CH4 in the crude fuel gas are selectively separated by an adsorbent and enriched at the bottom of the system, yielding high-concentration combustible gases with a purity ≥95 vol% for H2 and ≥90 vol% for CH4, which are sold directly as products. The separated byproducts, such as CO2 and uncondensed light hydrocarbons, are discharged from the top of the system, mixed with condensed tar, and then sent to the high-temperature reforming zone. This step achieves pre-purification and targeted collection of the target products, completely preventing them from being consumed by side reactions in the reforming zone and significantly improving the yield of the target products.

[0044] 5. The pyrolysis semi-coke continuously fed into the low-temperature pyrolysis zone is stacked in the high-temperature reforming zone at the bottom of the integrated thermal reactor to form a fixed semi-coke bed, with the bed height controlled at 0.5-2m. After the aforementioned condensed tar, column-separated by-product components, gasifying agent, and optional reaction promoter are fully mixed, the mixture is continuously and uniformly introduced from the bottom of the bed through a gas distributor. The gaseous material passes through the semi-coke stacked bed from bottom to top, completing the volatile matter reforming and tar cracking reaction.

[0045] The method parameters are controlled as follows: reforming reaction temperature 700-900℃, residence time of gaseous material in the semi-coke bed 1-5s, residence time of semi-coke in the reforming zone 60-120min; the gasifying agent is at least one of steam and CO2, and the mass ratio of gasifying agent to circulating tar is 0.5-3:1; for biomass feedstocks with low AAEMs content (such as pine sawdust), a reaction promoter is added, which is at least one of dolomite, olivine, and iron-based modifier, and the amount added is 1-3wt% of the biomass feed mass.

[0046] The core reaction process in this step is divided into two stages:

[0047] Adsorption and enrichment stage: such as Figure 3 As shown, heavy components such as tar are first adsorbed by the porous framework of the semi-coke and enriched inside the pores of the semi-coke, which greatly increases the contact area between the tar macromolecules and the active sites on the surface of the semi-coke, thereby enhancing the mass transfer process.

[0048] In-situ reorganization stage: such as Figure 4 As shown, the adsorbed and enriched tar macromolecules undergo cleavage and reforming reactions at the active sites on the surface of the semi-coke, with a spin concentration of 10 in the semi-coke. 16 ~10 19 PFRs with spin / g serve as reaction initiators, triggering free radical chain reactions and reducing the activation energy of tar cracking from the traditional 220–300 kJ / mol to 120–180 kJ / mol. The K, Na, Ca, and Mg-type AAEMs enriched on the surface of the semi-coke serve as catalytic sites, further enhancing the cracking, reforming, and lightening of tar macromolecules, ultimately converting them into hydrogen-rich fuel gas mainly composed of H2 and CH4.

[0049] The hydrogen-rich fuel gas produced by the reforming reaction is discharged from the top of the reforming zone and sent to the condensation unit in step 3. It is then condensed and separated into gas and liquid components together with the pyrolysis volatiles, and then enters the column separation unit. The semi-coke after the reforming reaction is circulated back to the low-temperature pyrolysis zone in step 2 after the temperature is controlled by a screw conveyor and a heat exchange unit. It serves as a heat carrier and reaction aid. The mass ratio of the circulating semi-coke to the fresh biomass feed is controlled at 0.5 to 2:1 to form a closed-loop coke circulation system, which realizes the continuous renewal of the active sites of the semi-coke and the self-balance of the system's heat. The excess semi-coke remaining after the reaction is discharged from the bottom of the furnace and sold as a carbon-based product after modification treatment.

[0050] 6. Collect the unused by-product gas from column separation and the uncondensed tail gas from the reforming reaction, and send them into the combustion furnace for complete combustion. The heat generated by combustion is supplied to the reaction heat demand of the low-temperature pyrolysis zone and the high-temperature reforming zone through heat exchange devices to achieve self-heating balance of the method system. The tail gas generated by combustion is treated by bag filter dust removal, desulfurization and denitrification, and then discharged in compliance with standards.

[0051] Example 1

[0052] This embodiment provides a volatile matter reforming method based on the biomass pyrolysis semi-coke cycle, and the specific implementation is as follows:

[0053] 1. Raw material pretreatment: Select corn stalks as raw material, crush them to a particle size of 1-3 mm, and dry them to a moisture content of 10 wt% for later use;

[0054] 2. Low-temperature oxygen-deficient pyrolysis: The pretreated corn stalks are continuously fed into the low-temperature pyrolysis zone of the integrated thermal reactor. The pyrolysis temperature is controlled at 300℃, the oxygen volume fraction of the system is 1 vol%, the solid phase residence time is 45 min, the gas phase volatile matter residence time is <2 s, and the system pressure is -100 Pa.

[0055] 3. Staged condensation and gas-liquid separation: Volatile matter is fed into a two-stage condenser, with the first-stage condensation temperature controlled at 200℃ and the second-stage condensation temperature at 60℃. The tar condensation and collection rate is 95.2%, and the residual tar in the gas phase is 22 mg / Nm³. 3 ;

[0056] 4. Column separation and enrichment: The crude gas is fed into a pressure swing adsorption column separation system filled with 13X molecular sieve. The operating temperature is controlled at 30℃ and the operating pressure is 0.6MPa to obtain H2 with a purity of 96.4 vol% and CH4 with a purity of 92.1 vol%.

[0057] 5. High-temperature reforming and coke recycling: Pyrolytic semi-coke forms a 1.2m high bed in the reforming zone, with the reforming temperature controlled at 800℃, a gas phase residence time of 2.5s, and a semi-coke residence time in the reforming zone of 80min; steam is used as the gasifying agent, with a steam-to-recycled tar mass ratio of 1.5:1; corn stalks themselves are rich in AAEMs, so no additional reaction promoters are added; the semi-coke recycling ratio is 1:1.

[0058] 6. By-product gas and exhaust gas are fed into a combustion furnace for combustion and heating, and the exhaust gas is purified to meet emission standards.

[0059] The test results in this embodiment are as follows: tar conversion rate 95.2%, and residual tar in the gas phase after reforming 8 mg / Nm³. 3 The H2 yield was increased by 38.3% and the CH4 yield by 26.7% compared to the traditional high-temperature gasification method; the overall energy consumption of the method was reduced by 25.2%; the unit operated continuously and stably for 1200 hours without any problems such as pipeline blockage or catalyst deactivation.

[0060] Example 2

[0061] This embodiment provides a volatile matter reforming method based on the biomass pyrolysis semi-coke cycle, and the specific implementation is as follows:

[0062] 1. Raw material pretreatment: Select pine sawdust as raw material, crush it to a particle size of 0.5-2mm, dry it to a moisture content of 8wt%, and set it aside;

[0063] 2. Low-temperature oxygen-deficient pyrolysis: The pyrolysis temperature is controlled at 350℃, the oxygen volume fraction of the system is 2.5 vol%, the solid phase residence time is 60 min, the gas phase volatile matter residence time is <2 s, and the system pressure is -120 Pa;

[0064] 3. Staged condensation gas-liquid separation: The first-stage condensation temperature is controlled at 180℃, the second-stage condensation temperature at 50℃, the tar condensation collection rate is 95.0%, and the residual tar in the gas phase is 25 mg / Nm³. 3 ;

[0065] 4. Column separation and enrichment: Using activated carbon molecular sieve and ZIFs composite adsorbent, the operating temperature is controlled at 40℃ and the operating pressure at 0.8MPa to obtain H2 with a purity of 95.8 vol% and CH4 with a purity of 91.5 vol%.

[0066] 5. High-temperature reforming and coke recycling: The semi-coke bed height is 1m, the reforming temperature is 750℃, the gas phase residence time is 3s, and the residence time in the semi-coke reforming zone is 90min; the gasifying agent is a mixture of CO2 and water vapor (volume ratio 1:1), and the mass ratio of gasifying agent to circulating tar is 2:1; olivine is added as a reaction promoter at a rate of 1.5wt% of the sawdust feed mass; the semi-coke recycling ratio is 1.2:1.

[0067] 6. Heat recovery and exhaust gas treatment are the same as in Example 1.

[0068] The test results in this embodiment are as follows: tar conversion rate 95.0%, and residual tar in the gas phase after reforming 9 mg / Nm³. 3 The H2 yield was increased by 35.6% and the CH4 yield by 23.2% compared to the traditional high-temperature gasification method; the overall energy consumption of the method was reduced by 22.7%; the unit operated continuously and stably for 1100 hours without any problems such as pipeline blockage or catalyst deactivation.

[0069] Example 3

[0070] This embodiment provides a volatile matter reforming method based on the biomass pyrolysis semi-coke cycle, and the specific implementation is as follows:

[0071] 1. Raw material pretreatment: Select edible fungus residue as raw material, crush it to a particle size of 2-5 mm, dry it to a moisture content of 12 wt%, and set it aside;

[0072] 2. Low-temperature oxygen-deficient pyrolysis: The pyrolysis temperature is controlled at 400℃, the oxygen volume fraction of the system is 4 vol%, the solid phase residence time is 50 min, the gas phase volatile matter residence time is <2 s, and the system pressure is -80 Pa;

[0073] 3. Staged condensation gas-liquid separation: The first-stage condensation temperature is controlled at 220℃, the second-stage condensation temperature at 70℃, the tar condensation and collection rate is 99.3%, and the residual tar in the gas phase is 20mg / Nm³. 3 ;

[0074] 4. Column separation and enrichment: Using a composite adsorbent of 13X molecular sieve and activated carbon molecular sieve, the operating temperature is controlled at 35℃ and the operating pressure at 0.5MPa to obtain H2 with a purity of 95.2 vol% and CH4 with a purity of 90.8 vol%.

[0075] 5. High-temperature reforming and coke recycling: The semi-coke bed height is 1.5m, the reforming temperature is 850℃, the gas phase residence time is 2s, and the residence time in the semi-coke reforming zone is 70min; steam is used as the gasifying agent, and the mass ratio of gasifying agent to circulating tar is 1:1; an iron-based modifier is added as a reaction promoter at a rate of 2.5wt% of the inoculum feed mass; the semi-coke recycling ratio is 0.8:1.

[0076] 6. Heat recovery and exhaust gas treatment are the same as in Example 1.

[0077] The test results in this embodiment are as follows: tar conversion rate 96.1%, and residual tar in the gas phase after reforming 8.5 mg / Nm³. 3 The H2 yield was increased by 32.9% and the CH4 yield by 21.5% compared with the traditional high-temperature gasification method; the overall energy consumption of the method was reduced by 20.4%; the unit operated continuously and stably for 11,000 hours without pipeline blockage or catalyst deactivation.

[0078] Comparative Example 1

[0079] This comparative example uses a traditional one-step biomass high-temperature gasification method. The raw material is the same as in Example 1, which is corn straw. The pretreatment parameters are the same as in Example 1. The method parameters are: gasification temperature 950℃, oxygen volume fraction of system 8 vol%, no semi-coke circulation, no pre-condensation and column separation steps, and no catalytic reforming step.

[0080] The results of this comparative example are: tar conversion rate 72.3%, and tar residue in the outlet gas phase 186 mg / Nm³. 3 The purity of H2 was 72.5 vol%, and the purity of CH4 was 41.2 vol%. The overall energy consumption of the method was 54.3% higher than that of Example 1. The equipment experienced pipe blockage and coking problems after 800 hours of continuous operation, requiring shutdown for cleaning.

[0081] Comparative Example 2

[0082] This comparative example uses a traditional post-processing nickel-based catalytic reforming method. The raw material is the same as in Example 1, which is corn straw. The pretreatment, pyrolysis, and condensation steps are the same as in Example 1. The difference is that there is no semi-coke recycling and high-temperature semi-coke reforming step. The condensed crude gas is directly fed into a reforming reactor filled with commercial Ni / Al2O3 catalyst. The reforming temperature is 900℃. There is no pre-column separation step. The product is separated after reforming.

[0083] The test results of this comparative example are as follows: the initial tar conversion rate was 96.8%, and after 500 hours of continuous operation, the catalyst coking and deactivation occurred, and the tar conversion rate dropped to 65.4%; the H2 yield was 37.6% lower than that of Example 1, and the CH4 yield was 29.8% lower; the catalyst cost was 12 times that of Example 1, and the overall energy consumption of the method was 42.1% higher than that of Example 1.

[0084] Comparative Example 3

[0085] This comparative example uses a pyrolysis reforming method without half-coke circulation. The raw materials, pretreatment, pyrolysis, condensation, and separation steps are the same as in Example 1. The difference is that there is no closed-loop half-coke circulation, the pyrolysis half-coke is sold directly, and a commercial dolomite catalyst is used in the reforming process. The reforming temperature is 800℃.

[0086] The results of this comparative example are as follows: tar conversion rate 82.5%, and residual tar in the gas phase after reforming 68 mg / Nm³. 3 The H2 yield was 28.3% lower than that of Example 1, and the CH4 yield was 21.7% lower. The catalyst deactivated after 500 hours of continuous operation and needed to be shut down for replacement. The continuous operation period of the unit was much shorter than that of Example 1.

Claims

1. A method for reforming volatiles based on a biomass pyrolysis char cycle, characterized by, Includes the following steps: Step S1: After pretreatment, the biomass raw material is fed into the low-temperature pyrolysis zone of the thermal reactor for low-temperature oxygen-deficient pyrolysis to obtain pyrolytic semi-coke and volatile matter containing tar; the low-temperature oxygen-deficient pyrolysis temperature is 300-400℃, and the oxygen volume fraction of the system is 1-4 vol%. Step S2: The tar-containing volatiles obtained in step S1 are sent to a condensation unit for step-by-step condensation to achieve gas-liquid separation and obtain condensed tar and crude fuel gas respectively. Step S3: The crude gas obtained in step S2 is fed into a column separator for graded separation to enrich the target product and separate by-product components. Step S4: The pyrolysis semi-coke obtained in step S1 is fed into a high-temperature reforming zone to form a semi-coke bed. Step S5: The condensed tar obtained in step S2, the by-product components obtained in step S3, and the gasifying agent and reaction promoter are mixed and sent to the high-temperature reforming zone. The volatile matter reforming and tar cracking reaction are completed through the semi-coke bed obtained in step S4. The hydrogen-rich gas produced by the reaction is fed into the condensation unit for recycling. Step S6: The semi-coke in the semi-coke bed after the high-temperature reforming reaction in step S5 is recycled back to the low-temperature pyrolysis zone after heat exchange regulation, serving as a heat carrier and reaction aid, forming a closed-loop semi-coke recycling system. Step S7: The unused portion of the by-product components obtained from column separation in step S3 and the tail gas that was not condensed after the reforming reaction in step S5 are collected and burned. The heat generated by the combustion is used to supply the reaction heat demand of the low-temperature pyrolysis zone and the high-temperature reforming zone. The tail gas generated by the combustion is purified and then discharged in compliance with standards.

2. The method of claim 1 wherein, In step S1, the step of feeding the pretreated biomass raw material into the low-temperature pyrolysis zone of the thermal reactor specifically includes: The lignocellulosic biomass raw materials are crushed to a particle size of 0.5-5 mm, dried to a moisture content of 8-12 wt%, and then sent to a low-temperature pyrolysis zone.

3. The method of claim 1 wherein, In step S1, the low-temperature oxygen-deficient pyrolysis also has the following reaction parameters set as follows: solid phase biomass residence time is 45-60 min, gas phase volatile matter residence time is <2 s, and system pressure is a slight negative pressure of -80 to -120 Pa.

4. The method of claim 1 wherein, In step S2, the stepwise condensation process adopts a two-stage condensation method, with the first-stage condensation temperature being 180-220℃ and the second-stage condensation temperature being 50-70℃.

5. The method of claim 1 wherein, In step S3, the column separation device is a multi-tower series pressure swing adsorption column separation system, and the adsorbent is at least one of 13X molecular sieve, activated carbon molecular sieve, and ZIFs porous material; the operating temperature of the fractionation separation process is 30-40℃, and the operating pressure is 0.5-0.8MPa; the target product includes at least one of H2 and CH4.

6. The method of claim 1 wherein, In step S4, the reaction parameters of the high-temperature reforming zone are set as follows: reaction temperature 750-850℃, semi-coke bed height 1-1.5m, residence time of gaseous material in the semi-coke bed 2-3s, and residence time of pyrolytic semi-coke in the reforming zone 70-90min.

7. The method of claim 1 wherein, In step S5, the gasifying agent includes at least one of water vapor and CO2, and the mass ratio of the gasifying agent to the condensed tar is 1 to 2:1; and / or the reaction promoter includes at least one of dolomite, olivine, and iron-based modifier, and the amount added is 0 to 2.5 wt% of the biomass raw material.

8. The volatile matter reforming method according to claim 1, characterized in that, In step S6, the mass ratio of the recycled semi-coke to the fresh biomass feed in the low-temperature pyrolysis zone is 0.8 to 1.2:1.

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