Biomass gasifier with internal circulation

Abstract

The invention discloses a biomass gasification furnace with internal circulation. A gasification area and a feed fluidization area are sequentially arranged in a furnace body of the disclosed gasification furnace from top to bottom; the feed fluidization area is of an inverted conical structure, a fluidization gas inlet is formed in the bottom of the feed fluidization area, a biomass inlet, a catalyst inlet and outlet and an ash outlet are formed in the side wall of a furnace body of the feed gasification area, and a synthesis gas outlet is formed in the furnace wall of the area above the gasification area; a fluidization cyclone is mounted at the fluidization gas inlet and is connected with a gas inlet device; an inner circulation cylinder is mounted in the furnace body, the body of the inner circulation cylinder is of a cylindrical structure, the inner circulation cylinder, the fluidization cyclone and the furnace body are coaxial, and meanwhile, the inner circulation cylinder is positioned above the biomass inlet and the catalyst inlet and outlet and below the synthesis gas outlet; the reaction efficiency of the tar and the catalyst is improved through air distribution.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass gasification hydrogen production and relates to a biomass gasifier with internal circulation. Background Art

[0002] Biomass thermochemical hydrogen production is a process in which biomass undergoes a gasification reaction with a gasifying agent (water vapor, pure oxygen, oxygen-enriched air, etc.) in a gasifier to generate a hydrogen-rich synthesis gas containing components such as hydrogen, carbon monoxide, carbon dioxide, methane, and tar. The synthesis gas is then purified and separated to obtain pure hydrogen gas for use in hydrogen fuel cells, etc.

[0003] At present, the hydrogen-rich synthesis gas obtained by biomass thermochemical hydrogen production contains a large amount of tar, which not only blocks subsequent pipelines and equipment, but also, as a macromolecular organic matter, wastes biomass energy and affects the production of effective gases (hydrogen and carbon monoxide) in the synthesis gas.

[0004] Catalytic cracking of tar in a gasifier is one of the most commonly used methods for disposing tar. This method involves putting a catalyst into a gasifier to crack the tar into small molecules of hydrogen, carbon monoxide and other gases in the furnace. Because it does not require a separate catalytic reactor outside the gasifier, it has the advantages of a simple system structure.

[0005] In the prior art, when a fixed bed gasifier is used, biomass and catalyst are mixed together to form a fixed bed layer. At this time, biomass and catalyst are piled together, and the contact area with tar is small, the reaction efficiency is low, the catalyst is seriously wasted, and the tar removal effect is poor. When a fluidized bed gasifier is used, a cyclone separator must be separately set outside the gasifier to separate the catalyst from the synthesis gas, making the system structure complicated.

[0006] In addition, biomass carbon will be generated during the biomass gasification process and will be discharged with the ash, which will also affect the production of effective gases (hydrogen and carbon monoxide) in the synthesis gas, resulting in a low biomass carbon conversion rate. Summary of the invention

[0007] In view of the defects or shortcomings of the prior art, the present invention provides a biomass gasifier with internal circulation.

[0008] To this end, the biomass gasifier with internal circulation provided by the present invention comprises a furnace body, wherein a gasification zone and a feed fluidization zone are sequentially arranged from top to bottom in the furnace body;

[0009] The feed fluidization zone is an inverted cone structure, with a fluidization gas inlet at the bottom of the feed fluidization zone, a biomass inlet, a catalyst inlet and outlet, and an ash outlet on the side wall of the furnace body of the feed fluidization zone; a synthesis gas outlet is opened on the furnace wall above the gasification zone;

[0010] A fluidizing cyclone is installed at the fluidizing gas inlet, and the fluidizing cyclone is connected to a gas supply device;

[0011] An inner circulation cylinder is installed in the furnace body. The inner circulation cylinder body is a cylindrical structure. The axial upper and lower ends of the inner circulation cylinder are open structures, and the upper end is a flared structure. The inner diameter of the inner circulation cylinder is larger than the diameter of the fluidized cyclone, and the outer diameter is smaller than the inner diameter of the furnace body. The inner circulation cylinder, the fluidized cyclone and the furnace body are coaxial. At the same time, the inner circulation cylinder is located above the biomass inlet and the catalyst inlet and outlet, and below the synthesis gas outlet. The inner circulation cylinder is the inner circulation area, and the area between the outer wall of the inner circulation cylinder and the inner wall of the cylinder is the outer circulation area.

[0012] An optional solution is that the upper section of the inner circulation barrel is located in the gasification zone, and the lower section is located in the feed fluidization zone.

[0013] An optional solution is that the fluidized cyclone includes a cyclone body, a middle area of ​​the body is an inner direct flow area, and an outer cyclone area is surrounding the inner direct flow area;

[0014] The inner direct flow zone is provided with a plurality of vertical vents, and the outer vortex zone is provided with a plurality of circles of inclined vents, and a plurality of inclined vents are distributed in each circle of inclined vents; the axial direction of the vertical vents is along the axial direction of the furnace body, and the axial direction of the inclined vents is inclined relative to the axial direction of the furnace body, and the inclination direction of the plurality of inclined vents in the same circle, wherein after a port A of any inclined vent is projected along the axial direction of the furnace body to the surface where another port B is located, the line connecting the projection port of port A and port B is the inclination direction of the inclined vent to form a circle;

[0015] The inner direct flow zone, the outer cyclone zone, the inner circulation cylinder and the furnace body are coaxial.

[0016] An optional solution is that the inner direct current zone is circular.

[0017] An optional solution is that the inner diameter of the gasification zone remains unchanged from top to bottom.

[0018] An optional solution is that the ash outlet is located below the biomass inlet and the catalyst inlet and outlet.

[0019] An optional solution is that the air inlet device includes a wind box, a gasifying agent inlet is provided on the wind box, and the wind box is installed at the bottom of the fluidizing cyclone.

[0020] An optional solution is that the furnace body is a vertical furnace body.

[0021] The gasifier of the present invention, through a special structure and airflow organization, forms an inner circulation zone and an outer circulation zone in the reaction zone, and the biomass and tar cracking catalyst continuously circulate in the two zones in a fluidized state, which can significantly improve the reaction efficiency of the tar and the catalyst, and simultaneously realizes biomass gasification and tar removal in the gasifier, making the system simple, easy to operate, and reducing costs.

[0022] The present invention solves the problems in the prior art that when a fixed bed gasifier is used, biomass and catalyst are piled together, the contact area with tar is small, the reaction efficiency is low, the catalyst is seriously wasted and the tar removal effect is poor. When a fluidized bed gasifier is used, a cyclone separator must be separately set outside the gasifier, and the system structure is complicated. In addition, the biomass carbon reaction is insufficient and will be discharged with the ash, resulting in a low biomass carbon conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 is a schematic diagram of the structure of the gasifier of Example 1 of the present invention; in the figure, 1 is a furnace body; 2 is a feed fluidizing zone; 3 is a gas supply device; 4 is a top cover; 5 is a biomass inlet; 6 is a catalyst inlet and outlet; 7 is a gasifying agent inlet; 8 is a fluidizing cyclone; 9 is an ash outlet; 10 is an ash discharge valve; 11 is a synthesis gas outlet; 12 is an inner circulation cylinder; 1201 is a straight section cylinder; 1202 is an expanded section cylinder.

[0024] Figure 2 This is a schematic diagram of the external circulation area and internal circulation area of ​​the gasifier. In the figure, NH is the internal circulation area; WH is the external circulation area.

[0025] Figure 3 Schematic diagram of the structure of the fluidized cyclone in the embodiment.

[0026] Figure 4 for Figure 3 Schematic diagram of the structure of the middle inclined vent hole; Figure 3-4 In the figure, WX is the outer cyclone zone; NZ is the inner direct flow zone; 801 is the fluidizing cyclone body; 802 is the vertical vent; 803 is the inclined vent.

[0027] Figure 5 This is another structural example of the gasifier of the present invention; wherein 13 is a slag discharge pipe, and 14 is a valve. DETAILED DESCRIPTION

[0028] Unless otherwise specified, the scientific and technical terms used herein are understood according to the knowledge of ordinary technicians in the relevant fields.

[0029] The directional or directional terms such as axial, upper, lower, top, bottom, side, etc. described in this article are consistent with the relevant directions or orientations in the drawings of the specification. It should be noted that the drawings of the specification are intended to explain the present invention. The solutions obtained by technical personnel in this field through equivalent transformation based on the contents disclosed in this article are all within the protection scope of the present invention.

[0030] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Embodiment 1:

[0032] like Figure 1 As shown, the biomass gasifier with internal circulation of the present invention comprises a furnace body 1, in which a gasification zone and a feed fluidization zone 2 are arranged in sequence from top to bottom, wherein the inner diameter of the feed fluidization zone gradually decreases from top to bottom to present an inverted cone structure, and a fluidization gas inlet is provided at the bottom of the feed fluidization zone, and a biomass inlet 5, a catalyst inlet and outlet 6 and an ash outlet 9 are provided on the side wall; a synthesis gas outlet 11 is provided on the side wall of the furnace body at the top or upper area of ​​the gasification zone;

[0033] A fluidizing cyclone 8 is installed at the fluidizing gas inlet, and the fluidizing cyclone is connected to the gas supply device 3;

[0034] At the same time, an inner circulation cylinder 12 of a cylindrical structure is installed in the furnace body (in the specific scheme, it can be fixed to the feed fluidization zone and / or gasification zone cylinder by a multi-point method), and the inner circulation cylinder is coaxial with the furnace body and the fluidized cyclone. At the same time, the inner circulation cylinder is axially located above the biomass inlet and the catalyst inlet and outlet, and below the synthesis gas; the inner circulation cylinder has open structures at both axial ends and a flared structure at the upper end. In the specific scheme, the inner circulation cylinder is composed of a straight section cylinder 1201 and a flared end cylinder 1202; and the inner diameter of the inner circulation cylinder is larger than the diameter of the fluidized cyclone, and the outer diameter is smaller than the inner diameter of the furnace body, so as to ensure that an inner circulation zone is formed in the inner circulation cylinder under the drive of the airflow below, and the area between the outer wall of the inner circulation cylinder and the inner wall of the cylinder is the outer circulation zone.

[0035] Figure 1 The upper section of the inner circulation tube in the furnace body is located in the gasification zone, and the lower section is located in the feed fluidization zone.

[0036] The furnace body of the present invention is coaxially arranged with the inner circulation tube 12, and the diameter of the inner circulation tube straight section 1201 is larger than the diameter of the lower fluidizing cyclone 8. With this arrangement, an inner circulation zone NH and an outer circulation zone WH (such as Figure 2As shown). The principle of the formation of this circulation zone is that under the action of the lower fluidized cyclone and the inner circulation cylinder, the biomass particles and the tar cracking catalyst flow upward, and under the action of the rotating airflow of the fluidized cyclone, a negative pressure zone is formed in the central area directly above the fluidized cyclone (i.e., inside the inner circulation cylinder). At the same time, since the feed fluidized zone cylinder adopts an inverted cone structure, another negative pressure zone will be formed near the outer wall surface of the inner circulation cylinder (i.e., the area between the inner circulation cylinder and the inner wall of the furnace body), which makes part of the airflow entrained with particles deflected to the central negative pressure zone in the inner circulation cylinder, and the other part of the airflow entrained with particles deflected to the negative pressure zone outside the inner circulation cylinder, thereby forming the inner circulation zone NH and the outer circulation zone WH. When the particles flow to the fluidized cyclone through the inner circulation zone and the outer circulation zone, the airflow flowing out of the fluidized cyclone is blown up again.

[0037] At the beginning of operation, the ash discharge valve 10 at the ash outlet is closed; after starting operation, the mixed gas of water vapor and pure oxygen enters the furnace body through the air intake device and the fluidized cyclone, and the airflow forms a rotating airflow (a spiral rising airflow in the preferred embodiment) after passing through the fluidized cyclone; then, biomass particles and tar cracking catalyst are fed through the biomass inlet 5 and the catalyst inlet and outlet 6 (the catalyst can be fed discontinuously, fed once at the initial start-up, and selectively fed in addition according to the catalytic cracking effect in the later stage);

[0038] Then, the biomass particles and the tar cracking catalyst particles flow through the inner circulation zone and the outer circulation zone under the action of the rotating airflow (see Figure 2 As shown in the figure, during the flow process, the biomass particles and the gasification agent undergo a gasification reaction to generate components such as hydrogen, carbon monoxide, methane, carbon dioxide, tar, and some biomass carbon; at the same time, the tar and the tar cracking catalyst undergo a catalytic cracking reaction to decompose the tar into small molecules of hydrogen and carbon monoxide and other gases, and the generated biomass carbon is fully in contact with the water vapor in the gasification agent during the continuous circulation process to produce hydrogen and carbon monoxide;

[0039] Finally, the generated synthesis gas (hydrogen, carbon monoxide, methane, carbon dioxide and a small amount of unreacted tar) flows out through the synthesis gas outlet 11 provided on the upper cylinder.

[0040] After running for a period of time, if the tar content in the synthesis gas discharged from the gasifier exceeds the standard, the ash discharge valve 10 is opened to discharge the deactivated tar cracking catalyst and ash therein, and new tar cracking catalyst particles are fed through the tar cracking catalyst inlet 6 at the same time.

[0041] In the scheme of the present invention, the function of the fluidized cyclone is to make the gasified gas entering the furnace body form a cyclonic gas, ensuring that the biomass particles and the catalyst are in a fluidized state. A preferred structure of the fluidized cyclone is as follows: Figure 3 and 4As shown, it includes a cyclone body 801, the middle area of ​​the body is an inner direct current zone NZ, and the inner direct current zone is surrounded by an outer cyclone zone WX, wherein the inner direct current zone is provided with a plurality of vertical vents 802, and the outer cyclone zone is provided with a plurality of circles of inclined vents, and a plurality of inclined vents 803 are distributed in each circle of inclined vents, the axial direction of the vertical vents is along the axial direction of the furnace body, and the axial direction of the inclined vents is inclined relative to the axial direction of the furnace body, and the inclination direction of the plurality of inclined vents in the same circle (the inclination direction is defined as: after projecting one port A of an inclined vent along the axial direction of the furnace body to the surface where the other port B is located, the line connecting the projection port of port A and port B is the inclination direction of the inclined vent) surrounds a circle; the outer cyclone zone, the inner direct current zone are coaxial with the inner circulation tube and the furnace body. The advantage of this solution is that by setting up the inner direct current zone NZ in the central area, the biomass particles and tar cracking catalyst particles returned from the central area of ​​the inner circulation zone NH of the reaction zone will be blown up again by the strong vertical upward airflow, preventing larger particles from depositing on the surface of the fluidizing cyclone 8, thereby affecting the fluidization effect of the particles.

[0042] When the above cyclone is used, in the specific scheme, the swirl coefficient (the ratio of the tangential wind speed to the radial wind speed) of the fluidized cyclone needs to be greater than 0.5. In the preferred scheme, when 0.5 < swirl coefficient ≤ 1 and the inner diameter of the furnace gasification zone is less than or equal to 1.5 meters, the maximum height from the top of the inner circulation tube to the upper plane of the fluidized cyclone is 1.5 meters; when 0.5 < swirl coefficient ≤ 1 and the inner diameter of the furnace gasification zone is less than or equal to 3 meters, the maximum height from the top of the inner circulation tube to the upper plane of the fluidized cyclone is 2 meters.

[0043] In the specific plan, Figure 1 The furnace body shown is a vertical furnace body, which is composed of a straight cylinder with a constant inner diameter at the top, a top cover 4 and a lower inverted conical cylinder.

[0044] In the specific plan, Figure 1 As shown, the gas supply device 3 includes a wind box installed at the bottom of the fluidized cyclone, and a gasifying agent inlet 7 is opened on the side wall of the wind box. The gasifying agent uses water vapor and pure oxygen.

[0045] Comparative Example:

[0046] The difference between this comparative example and Example 1 is that Figure 3 On the basis of the invention, the structure of the inclined vent hole used is a straight hole.

[0047] The furnace bodies of Example 1 and Comparative Example 1 are used to gasify the same biomass with the same process. When the temperature in each furnace is the same at 800°C, the fluidizing plate adopts a full straight hole structure. Compared with the middle inclined hole scheme of Example 1, the internal circulation zone and the external circulation zone cannot be formed in the furnace body of the comparative example, and the residence time of the biomass particles and the tar catalyst particles in the furnace is reduced, resulting in an increase in the tar content in the outlet synthesis gas, a decrease in the carbon conversion rate, and an increase in the unreacted carbon content in the slag. The relevant test data of Example 1 and Comparative Example 1 after running for the same time are shown in Table 1 below. The tar content detection method in Table 1 can be found in GB / T1999-2008 "Sampling Method for Coking Oil Products", the definition method of carbon conversion rate can be found in NB / T10795-2021 "Technical Guidelines for Biomass Gasification Polygeneration System", and the carbon content detection method in slag can be found in GB / T176-2017 "Cement Chemical Analysis Method" for the determination method of cement ignition loss.

[0048] Table 1 Comparison of the effects of comparative example 1 and embodiment 2

[0049] Comparison Items Export tar content (mg / Nm3) Carbon conversion rate (%) Carbon content in slag (%) Comparative Example 1 20 75 2.2 Example 2 10 90 1.2

[0050] Embodiment 2:

[0051] See also Figure 5 As shown, the gasifier of this embodiment is based on the embodiment 1, and a slag discharge pipe 13 is provided at the bottom of the furnace body. The slag discharge pipe passes through the central area of ​​the inner direct flow zone of the cyclone. A valve 14 is installed on the slag discharge pipe, and the discharge of ash is controlled by the switch of the valve 14. It should be noted that the furnace body is suitable for processes in which the catalyst particle size is smaller than the ash particle size. For example, the catalyst particles use nickel-based metal oxide catalysts, the catalyst particle size is less than 50um, and the ash particle size is generally: 100um-3mm; in this process, since the ash particle size is larger than the catalyst particle size, the ash and the deactivated catalyst can be separated by gravity. When the tar content in the synthesis gas discharged from the gasifier exceeds the standard, the ash is discharged through the bottom slag discharge pipe 13, and the ash outlet 9 is used to discharge the deactivated catalyst.

Claims

1. A biomass gasification furnace with internal circulation, comprising a furnace body, characterized in that: The furnace body is provided with a gasification zone and a feed fluidization zone from the top to the bottom in sequence; The feed fluidization zone is an inverted cone structure, with a fluidization gas inlet at the bottom of the feed fluidization zone, a biomass inlet, a catalyst inlet and outlet, and an ash outlet on the side wall of the furnace body of the feed fluidization zone; a synthesis gas outlet is opened on the furnace wall above the gasification zone; A fluidizing cyclone is installed at the fluidizing gas inlet, and the fluidizing cyclone is connected to a gas supply device; An inner circulation cylinder is installed in the furnace body. The inner circulation cylinder body is a cylindrical structure. The axial upper and lower ends of the inner circulation cylinder are open structures, and the upper end is a flared structure. The inner diameter of the inner circulation cylinder is larger than the diameter of the fluidized cyclone, and the outer diameter is smaller than the inner diameter of the furnace body. The inner circulation cylinder, the fluidized cyclone and the furnace body are coaxial. At the same time, the inner circulation cylinder is located above the biomass inlet and the catalyst inlet and outlet, and below the synthesis gas outlet. The inner circulation cylinder is the inner circulation area, and the area between the outer wall of the inner circulation cylinder and the inner wall of the cylinder is the outer circulation area.

2. The biomass gasifier with internal circulation according to claim 1, characterized in that: The upper section of the inner circulation barrel is located in the gasification zone, and the lower section is located in the feed fluidization zone.

3. The biomass gasifier with internal circulation according to claim 1, characterized in that: The fluidized cyclone comprises a cyclone body, the middle area of ​​the body is an inner direct flow area, and the area surrounding the inner direct flow area is an outer cyclone area; The inner direct flow zone is provided with a plurality of vertical vents, and the outer vortex zone is provided with a plurality of circles of inclined vents, and a plurality of inclined vents are distributed in each circle of inclined vents; the axial direction of the vertical vents is along the axial direction of the furnace body, and the axial direction of the inclined vents is inclined relative to the axial direction of the furnace body, and the inclination direction of the plurality of inclined vents in the same circle, wherein after a port A of any inclined vent is projected along the axial direction of the furnace body to the surface where another port B is located, the line connecting the projection port of port A and port B is the inclination direction of the inclined vent to form a circle; The inner direct flow zone, the outer cyclone zone, the inner circulation cylinder and the furnace body are coaxial.

4. The biomass gasifier with internal circulation according to claim 3, characterized in that: The inner direct current zone is circular.

5. The biomass gasifier with internal circulation according to claim 1, characterized in that: The inner diameter of the gasification zone remains constant from top to bottom.

6. The biomass gasifier with internal circulation according to claim 1, characterized in that: The ash outlet is located below the biomass inlet and the catalyst inlet and outlet.

7. The biomass gasifier with internal circulation according to claim 1, characterized in that: The air inlet device comprises a wind box, on which a gasifying agent inlet is arranged, and the wind box is installed at the bottom of the fluidizing cyclone.

8. The biomass gasifier with internal circulation according to claim 1, characterized in that: The furnace body is a vertical furnace body.

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