Biomass gasification method and related gasification furnace

Abstract

The invention discloses a biomass gasification method and a related gasification furnace. The gasification method is carried out in a gasification furnace, and a gasification oxidation area and an ash collecting area are arranged in the gasification furnace; the gasification oxidation zone is divided into an oxidation zone and a peripheral gasification zone; the method comprises the following steps: introducing water vapor and biomass into a gasification area, and gasifying the biomass by the water vapor in the gasification area to generate ash and intermediate synthesis gas; the intermediate synthesis gas enters the oxidation zone through the bottom of the oxidation zone; oxygen-containing gas is introduced into the bottom of the oxidation zone, the oxygen-containing gas in the oxidation zone performs partial oxidative cracking on the intermediate synthesis gas to generate synthesis gas and release heat, the synthesis gas is discharged from the top of the oxidation zone, and the heat generated by partial oxidative cracking provides heat for the gasification reaction of the gasification zone at the same time. The problems that in the prior art, the reforming reaction effect is poor due to the fact that the temperature of a tar reforming reaction area is not uniform, and when water vapor is adopted as a gasifying agent, oxygen-containing gas needs to be introduced to provide heat for gasification reaction are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass gasification hydrogen production, and relates to a biomass gasifier with tar reforming and a method for preparing hydrogen-rich synthesis gas by using the gasifier. Background Art

[0002] As a way of producing hydrogen from biomass, thermochemical hydrogen production from biomass (such as straw, wood chips, bamboo, etc.) can convert biomass into hydrogen-rich synthesis gas, and then obtain pure hydrogen gas through separation for use in hydrogen fuel cells, etc.

[0003] At present, the hydrogen-rich syngas obtained by biomass thermochemical hydrogen production contains a large amount of tar, which not only blocks subsequent pipelines and equipment, but also wastes biomass energy as a macromolecular organic matter and affects the yield of effective gas (hydrogen and carbon monoxide) in the syngas. Catalytic cracking and high-temperature cracking of tar are the two most commonly used methods for the disposal of tar.

[0004] ZL200710020623.5 discloses a biomass tar catalytic cracking device, the technical solution of which is characterized in that: biomass gasification and tar catalytic cracking reactions are integrated in the same reaction device, biomass gasification is achieved through an inner cylinder, and tar catalytic cracking is achieved through an outer cylinder coaxial with the inner cylinder, and the gasification reaction of the inner cylinder provides heat for the catalytic cracking reaction of the outer cylinder. Although this patent integrates gasification and tar catalytic cracking into one reactor, due to the heat dissipation effect of the outer cylinder wall of the reactor, the tar catalytic cracking reactor will have the problem of uneven temperature along the radial direction, thereby affecting the effect of tar catalytic cracking.

[0005] CN202311194702.3 discloses a biomass gasification furnace, which realizes biomass gasification and high-temperature cracking of tar by arranging an outer cylinder, an inner cylinder and a partition heating layer outside the outer cylinder. Although the heat dissipation effect of the outer wall of the outer cylinder on the temperature of the outer cylinder is reduced by arranging the partition heating outside the outer cylinder, it will cause the structure of the reactor to be complicated, which is not conducive to manufacturing and operation.

[0006] In the prior art, when water vapor is used to prepare hydrogen-rich synthesis gas, oxygen-containing gas (pure oxygen, oxygen-enriched air or air) needs to be introduced to provide heat for the gasification reaction. At this time, part of the biomass will undergo oxidation reaction with the oxygen-containing gas, resulting in less hydrogen content and more carbon monoxide content in the synthesis gas, thereby reducing the hydrogen yield. In addition, due to the heat dissipation of the outer cylinder wall, the uneven temperature in the tar reforming reaction zone affects the effect of tar reforming. Summary of the invention

[0007] In view of the defects or shortcomings of the prior art, the present invention provides a biomass gasification method.

[0008] The biomass gasification method provided by the present invention is carried out in a gasifier, wherein a gasification oxidation zone and an ash collection zone are arranged in the gasifier; along the axial direction of the furnace body, the gasification oxidation zone is located above the ash collection zone; the gasification oxidation zone is divided into a middle zone and a peripheral zone surrounding the middle zone, wherein the middle zone is an oxidation zone and the peripheral zone is a gasification zone; an auxiliary heater is installed above the gasification zone; the method comprises:

[0009] Step 1, introducing water vapor and biomass into the gasification zone, where the water vapor gasifies the biomass to generate ash and intermediate synthesis gas; the ash then enters the ash collection zone and is discharged from the bottom of the ash collection zone, and the intermediate synthesis gas enters the oxidation zone through the bottom of the oxidation zone;

[0010] Step 2, introducing oxygen-containing gas into the bottom of the oxidation zone, wherein the oxygen-containing gas in the oxidation zone partially oxidizes and cracks the intermediate synthesis gas to produce synthesis gas and release heat, and the synthesis gas is discharged through the top of the oxidation zone. The heat generated by the partial oxidation and cracking also provides heat for the gasification reaction in the gasification zone; the temperature of the oxidation zone is above 1100°C.

[0011] An optional solution is that the temperature of the intermediate synthesis gas entering the oxidation zone is 600-1000°C.

[0012] Optionally, the oxygen-containing gas is selected from pure oxygen, oxygen-enriched gas or air.

[0013] An optional solution is that the mass ratio of the water vapor to the biomass is 0.3-1:1.

[0014] An optional solution is to include an outer furnace body, wherein a gasification oxidation zone and an ash collection zone are sequentially arranged from top to bottom in the outer furnace body; and a grate is installed between the gasification oxidation zone and the ash collection zone;

[0015] An inner furnace body is axially mounted inside the outer furnace body, the bottom of the inner furnace body is an open structure, and the inner furnace body is located in the gasification and oxidation zone, and the bottom of the inner furnace body passes through the grate and is located in the ash collection zone; a gasification zone is formed between the outer wall of the inner furnace body located in the gasification and oxidation zone and the inner wall of the outer furnace body, and the interior of the inner furnace body is an oxidation zone, and the gasification zone is connected to the oxidation zone through the grate and the open structure;

[0016] A biomass feed inlet and a water vapor inlet are provided on the outer furnace wall of the gasification zone, a synthesis gas outlet is provided on the top of the inner furnace body, and an oxygen-containing gas inlet is provided on the inner furnace wall, and the oxygen-containing gas inlet is close to the bottom open structure;

[0017] The furnace body of the ash collection area is an inverted cone structure, and an ash outlet is provided at the bottom of the ash collection area.

[0018] Optionally, the oxygen-containing gas inlet is located in the ash collection area.

[0019] Optionally, the grate can rotate around the inner cylinder.

[0020] An optional solution is that the top of the outer cylinder is a hole-expanding structure.

[0021] An optional solution is that the oxygen-containing gas inlet is connected to an air inlet pipe.

[0022] An optional solution is that both the outer furnace body and the inner furnace body are vertical furnace bodies.

[0023] The present invention integrates the biomass gasification reaction zone and the tar reforming reaction zone into one body, the outer furnace body of the outer tube is the biomass gasification reaction zone, and the inner furnace body is the tar reforming reaction zone, so that the temperature of the tar reforming reaction zone is more uniform, which is effective in improving the reforming reaction efficiency of the tar. And the high temperature of the syngas in the tar reforming reaction zone of the inner furnace body provides the heat required for the steam gasification reaction of the biomass in the outer furnace body, so that hydrogen-rich syngas can be obtained while removing the tar.

[0024] The invention solves the problems in the prior art that the reforming reaction effect of the tar reforming reaction zone is poor due to uneven temperature, and when water vapor is used as the gasifying agent, oxygen-containing gas (pure oxygen, oxygen-enriched air or air) needs to be introduced to provide heat for the gasification reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The schematic diagram of the biomass gasifier of the present invention; in the figure, 1-external furnace body, 2-inner furnace body, 3-biomass inlet, 4-water vapor inlet, 5-biomass bed, 6-ash discharge valve, 7-ash outlet, 8-oxygen-containing gas inlet, 9-grate, 10-synthesis gas outlet, 101-top cover, 102-cylinder body, 103-inverted cone-shaped cylinder body, 104-straight section discharge cylinder; 201-inner cylinder top cover, 202-inner cylinder.

[0026] Figure 2 Another structural schematic diagram of the biomass gasifier of the present invention. DETAILED DESCRIPTION

[0027] Unless otherwise specified, the scientific and technical terms used herein are understood according to the knowledge of ordinary technicians in the relevant fields.

[0028] 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.

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention reduces the tar content in biomass gasification synthesis gas (i.e., intermediate synthesis gas) by setting an oxidation zone, and improves the heat utilization rate of the entire process.

[0031] Embodiment 1:

[0032] As attached Figure 1 As shown, the biomass gasifier for implementing the process of the present invention comprises an outer furnace body 1, in which a gasification oxidation zone and an ash collection zone are sequentially arranged from the top to the bottom along the axial direction, and a grate 9 is arranged between the two zones; Figure 1 The furnace body is a vertical furnace body;

[0033] An inner furnace body 2 is axially arranged in the gasification and oxidation zone, and the bottom of the inner furnace body 2 is an open structure, and the bottom open structure passes through the grate and is located in the ash collection area; the space between the outer wall of the inner furnace body and the inside of the outer furnace body forms a gasification zone, and the inner wall of the inner furnace body is an oxidation zone, and the gasification zone is connected to the gasification zone through the grate and the open structure. An auxiliary heater (not shown in the figure) is installed on the upper part of the gasification zone. In the specific scheme, multiple heaters can be installed according to process requirements, and the auxiliary heater is preferably a natural gas combustion nozzle;

[0034] A biomass feed port 3 and a water vapor inlet 4 are provided on the outer furnace wall of the gasification zone, a synthesis gas outlet 10 is provided on the top of the inner furnace body, and an oxygen-containing gas inlet 8 is provided on the inner furnace wall, and the oxygen-containing gas inlet is close to the bottom open structure. Figure 1 The oxygen-containing gas inlet is shown to be located in the ash collection area. The furnace body of the ash collection area is an inverted cone structure, and an ash outlet 7 is provided at the bottom.

[0035] An interlayer area is formed between the outer furnace body and the inner furnace body, and a movable grate 9 is arranged at the lower part of the interlayer area. The area formed by the upper part of the grate 9 and the inner part of the outer furnace body 1 is a biomass gasification reaction area, which carries a biomass bed 5 in the process; the biomass undergoes a gasification reaction with water vapor in this area to generate an intermediate synthesis gas composed of hydrogen, carbon monoxide, methane, carbon dioxide, tar, etc., and ash; the intermediate synthesis gas and ash can enter the lower area of ​​the grate through the grate 9; the ash discharge is controlled by the ash discharge valve at the ash outlet;

[0036] A tar reforming reaction zone (i.e., oxidation zone) is formed in the inner furnace body, and the lower opening is connected to the lower area of ​​the grate. The intermediate synthesis gas enters the oxidation zone through the lower opening and undergoes an oxidation reaction with the oxygen-containing gas entering this area, causing the tar in the intermediate synthesis gas to undergo a cracking reaction, thereby decomposing it into small molecules of hydrogen and carbon monoxide, which are then discharged from the synthesis gas outlet 11.

[0037] At the beginning of the process, the auxiliary heater heats the gasification zone, and after water vapor and biomass are introduced, the water vapor gasifies the biomass to produce ash and intermediate synthesis gas, wherein the intermediate synthesis gas contains H2, CO, CH4, CO2, tar, etc. (Compared with the existing method, in the first stage of biomass gasification in the process of the present invention, water vapor is used to gasify the biomass in the absence of oxygen-containing gas. The principle of the reaction process is that water vapor and biomass pyrolysis products CO, CO2, CH4, coke, etc. undergo a water-gas conversion reaction at above 500°C to produce intermediate synthesis gas); when the temperature of the gasification zone is raised to 100°C, the water vapor will react with the biomass pyrolysis products CO, CO2, CH4, coke, etc. to produce intermediate synthesis gas. After the temperature rises to above 500°C or / and the amount of intermediate synthesis gas in the gasification zone is stabilized, the auxiliary heater is turned off, and then or in advance, oxygen-containing gas is introduced to partially oxidize and crack the intermediate synthesis gas (the partial oxidation and cracking refers to the oxidation and cracking of part of the intermediate synthesis gas, that is, by oxidizing and utilizing part of the combustible gas (such as H2, CO) in the gasification synthesis gas) to generate internal heat to further crack the tar in the intermediate synthesis gas and provide the heat required for the gasification reaction in the gasification zone outside the oxidation zone. The final synthesis gas is hydrogen-rich synthesis gas, that is, the volume fraction of H2 in the synthesis gas is much greater than the volume fraction of CO. In the process of the present invention, although H2 and CO are consumed at the same time during the oxidation process, the volume fraction of H2 in the synthesis gas is still greater than the volume fraction of CO due to the high volume fraction of H2 in the intermediate synthesis gas itself.

[0038] In the above scheme of the present invention, the intermediate synthesis gas contains H2, methane, carbon monoxide, carbon dioxide, tar, etc., and has a high calorific value. It is introduced into oxygen-containing gas (such as pure oxygen, oxygen-rich gas or air) to produce oxidation reaction, which can generate high temperature. In the specific scheme, the mass ratio of steam to biomass is 0.3-1:1; the amount of oxygen-containing gas introduced depends on the oxygen content in the gas and the temperature requirement of the oxidation zone (i.e., above 1100°C).

[0039] In a preferred embodiment, the outer furnace body 1 and the inner furnace body 2 are cylindrical and coaxially arranged. The grate 9 is a rotating grate that can rotate along the central axis of the outer tube and the inner tube, and during the rotation, the ash and slag enter the lower area of ​​the grate.

[0040] In a specific solution, the outer furnace body 1 is assembled from a top cover 101, a cylinder 102, and an inverted conical cylinder 103. In a further solution, a straight section discharge cylinder 104 is connected to the ash outlet at the bottom of the inverted conical cylinder 103. The inner furnace body 2 is assembled from an inner cylinder top cover 201 and an inner cylinder 202.

[0041] Embodiment 2:

[0042] This embodiment adopts Figure 1The gasifier shown in the figure processes the variegated reed, and the industrial analysis, elemental analysis, and low calorific value analysis of the variegated reed (water content of 10%) (industrial analysis and elemental analysis detection methods refer to GB / T28731-2012 "Industrial Analysis Methods for Solid Biomass Fuels", and calorific value analysis refers to GB / T 30727-2014 "Automatic Oxygen Bomb Calorimeter Method") are shown in Table 1 below:

[0043] Table 1 Industrial analysis, elemental analysis and low calorific value of raw materials of Phragmites australis

[0044]

[0045] The method and gasifier of the present invention are used, and the furnace input is: 5000kg / h of variegated reed feed, 3000kg / h of water vapor, and 500kg / h of pure oxygen; the intermediate synthesis gas temperature is 800-1000°C (i.e., the bottom temperature of the gasification zone), and the oxidation zone temperature is 1050-1150°C;

[0046] The intermediate synthesis gas and synthesis gas components in the furnace were analyzed (the synthesis gas detection method was gas chromatography, and the synthesis gas was passed into a gas chromatograph for testing). The intermediate synthesis gas components in the process are shown in Table 2 below:

[0047] Table 2

[0048] Components unit Volume fraction CO ％ 20.6 CO2 ％ 9.5 CH4 ％ 3.2 H2 ％ 42.0 H2O ％ 24.3 tar g / Nm3 10g / Nm3

[0049] The composition of the syngas at the gasifier outlet is shown in Table 3 below:

[0050] Table 3

[0051] Components unit Volume fraction CO ％ 19.2 CO2 ％ 12.2 CH4 ％ 0.6 H2 ％ 44.6 H2O ％ 23.2 tar g / Nm3 2g / Nm3

[0052] In some other preferred embodiments, Figure 2 As shown, in order to facilitate the discharge of the synthesis gas, the top of the inner furnace body 2 is a hole expansion structure.

Claims

1. A biomass gasification method, characterized in that: The method is carried out in a gasifier, wherein a gasification oxidation zone and an ash collection zone are arranged in the gasifier; along the axial direction of the furnace body, the gasification oxidation zone is located above the ash collection zone; the gasification oxidation zone is divided into a middle zone and a peripheral zone surrounding the middle zone, wherein the middle zone is an oxidation zone and the peripheral zone is a gasification zone; an auxiliary heater is installed above the gasification zone; the method comprises: Step 1, introducing water vapor and biomass into the gasification zone, where the water vapor gasifies the biomass to generate ash and intermediate synthesis gas; the ash then enters the ash collection zone and is discharged from the bottom of the ash collection zone, and the intermediate synthesis gas enters the oxidation zone through the bottom of the oxidation zone; Step 2, introducing oxygen-containing gas into the bottom of the oxidation zone, wherein the oxygen-containing gas in the oxidation zone partially oxidizes and cracks the intermediate synthesis gas to produce synthesis gas and release heat, and the synthesis gas is discharged through the top of the oxidation zone. The heat generated by the partial oxidation and cracking also provides heat for the gasification reaction in the gasification zone; the temperature of the oxidation zone is above 1100°C.

2. The biomass gasification method according to claim 1, characterized in that: The temperature of the intermediate synthesis gas entering the oxidation zone is 600-1000°C.

3. The biomass gasification method according to claim 1, characterized in that: The oxygen-containing gas is selected from pure oxygen, oxygen-enriched gas or air.

4. The biomass gasification method according to claim 1, characterized in that: The mass ratio of the water vapor to the biomass is 0.3-1:

1.

5. A biomass gasifier for implementing the method of claim 1, characterized in that: It comprises an outer furnace body, wherein a gasification oxidation zone and an ash collection zone are arranged in sequence from the top to the bottom of the outer furnace body; and a grate is installed between the gasification oxidation zone and the ash collection zone; An inner furnace body is axially mounted inside the outer furnace body, the bottom of the inner furnace body is an open structure, and the inner furnace body is located in the gasification and oxidation zone, and the bottom of the inner furnace body passes through the grate and is located in the ash collection zone; a gasification zone is formed between the outer wall of the inner furnace body located in the gasification and oxidation zone and the inner wall of the outer furnace body, and the interior of the inner furnace body is an oxidation zone, and the gasification zone is connected to the oxidation zone through the grate and the open structure; A biomass feed inlet and a water vapor inlet are provided on the outer furnace wall of the gasification zone, a synthesis gas outlet is provided on the top of the inner furnace body, and an oxygen-containing gas inlet is provided on the inner furnace wall, and the oxygen-containing gas inlet is close to the bottom open structure; The furnace body of the ash collection area is an inverted cone structure, and an ash outlet is provided at the bottom of the ash collection area.

6. The biomass gasifier according to claim 5, characterized in that: The oxygen-containing gas inlet is located in the ash collection area.

7. The biomass gasifier according to claim 5, characterized in that: The grate can rotate around the inner cylinder.

8. The biomass gasifier according to claim 5, characterized in that: The top of the outer cylinder is a hole expansion structure.

9. The biomass gasifier according to claim 5, characterized in that: The oxygen-containing gas inlet is connected with an air inlet pipe.

10. The biomass gasifier according to claim 5, characterized in that: The outer furnace body and the inner furnace body are both vertical furnace bodies.

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