Multi-section fluidized bed gasification device and gasification method thereof

Abstract

The invention relates to a multi-section fluidized bed gasification device and a gasification method, the multi-section fluidized bed gasification device comprises a gasification furnace, the gasification furnace comprises a reaction section, a throat section and an expansion section which are sequentially connected from bottom to top, the cavity diameter of the throat section is smaller than the cavity diameter of the reaction section and the cavity diameter of the expansion section, and the cavity diameter of the reaction section is smaller than the cavity diameter of the expansion section; materials in the reaction section are accelerated by the opening waiting section and then enter the expansion section to form a central jet flow; the gas-solid separator is communicated with the expansion section; and the material returning device is communicated with the gas-solid separator and the reaction section so as to convey the solid material separated by the gas-solid separator back to the reaction section.

Description

Technical Field

[0001] The present invention relates to the technical field of solid fuel conversion, and particularly to a multi-stage fluidized bed gasification device and a gasification method. Background Art

[0002] Coal gasification is one of the core technologies for clean and efficient utilization of coal, and is the basis for the development of coal chemical industries such as coal-based chemicals and coal-based gas. The fluidized bed gasification technology uses pulverized coal with a particle size of 0 - 10 mm as raw material, and the gasification agent and pulverized coal undergo a gasification reaction in a fluidized form, with solid slag discharge. It has the advantages of strong coal type adaptability, environmental friendliness, no generation of wastewater such as tar, phenol water, and black water, large gasification intensity, and low investment, and is suitable as a gas source for industrial gas, small and medium-sized synthetic ammonia, coal-to-methanol, hydrogen, and other coal chemical industries.

[0003] Currently, in the existing fluidized bed gasification technology, the pyrolysis, gasification, and combustion reactions of coal in the furnace are coupled together. Part of the volatile matter generated by pyrolysis directly reacts with the introduced gasification agent, resulting in the conversion of volatile matter into carbon dioxide, carbon monoxide, and hydrogen. When producing gas, there is a problem of low calorific value, and when producing syngas, there is a problem of syngas containing methane. In addition, the particle radial concentration distribution in the transition zone and dilute phase zone of the fluidized bed shows an annular core structure, which is not conducive to the gasification reaction between the high-concentration carbon near the furnace sidewall and the carbon dioxide and water vapor in the furnace center, resulting in problems such as low carbon conversion rate and low furnace space utilization rate. Summary of the Invention

[0004] In view of the above analysis, embodiments of the present invention aim to provide a multi-stage fluidized bed gasification device and a gasification method to solve at least one of the above problems.

[0005] On the one hand, the present invention provides a multi-stage fluidized bed gasification device, including:

[0006] A gasification furnace, including a reaction section, a throat section, and an expansion section connected in sequence from bottom to top. The cavity diameter of the throat section is smaller than the cavity diameters of the reaction section and the expansion section, so that the materials in the reaction section can enter the expansion section after being accelerated through the throat section to form a central jet;

[0007] A gas-solid separator, communicated with the expansion section;

[0008] A return feeder, communicated with the gas-solid separator and the reaction section, for returning the solid materials separated by the gas-solid separator to the reaction section.

[0009] Further, the reaction section is provided with a first air inlet, a slag discharge port, and a return material port;

[0010] The first air inlet is located at the bottom end face of the reaction section;

[0011] The slag discharge port is located at the bottom of the side wall of the reaction section;

[0012] The return port is located on the side wall of the reaction section, and the return port is higher than the slag discharge port on the side wall.

[0013] Furthermore, the return port is located in the transition region between the dense phase region and the dilute phase region.

[0014] Furthermore, the ratio of the length of the throat section to the diameter of the throat section is 1-3:1.

[0015] Furthermore, the diameter of the lower part of the expansion section gradually increases from bottom to top;

[0016] A second air inlet is provided at the lower part of the expansion section, an air inlet pipe is provided at the second air inlet, and the included angle between the air inlet pipe and the horizontal plane is γ, -45°≤γ≤45°.

[0017] Furthermore, a plurality of the second air inlets are provided at the lower part of the expansion section, and correspondingly, an equal number of the air inlet pipes are provided;

[0018] The air inlet directions of the plurality of air inlet pipes are tangent to the same circle, the center line of the gasifier passes through the center of the tangent circle, and the diameter of the tangent circle is smaller than the diameter of the expansion section where the second air inlet is provided.

[0019] Furthermore, the gasifier is provided with a first feed port and a second feed port;

[0020] The first feed port is arranged in the reaction section, and the second feed port is arranged in the expansion section.

[0021] Furthermore, when the gasification device is used to produce synthesis gas, the first feed port is opened and the second feed port is closed to prepare for feeding through the first feed port;

[0022] When the gasification device is used to produce fuel gas, the second feed port is opened and the first feed port is closed to prepare for feeding through the second feed port.

[0023] Furthermore, the gasifier comprises two or more combinations composed of a throat section and an expansion section.

[0024] On the other hand, the present invention provides a gasification method for a multi-stage fluidized bed gasification device, which is realized by the above multi-stage fluidized bed gasification device, and the gasification method comprises:

[0025] Importing solid fuel into the gasifier through the first feed port or the second feed port;

[0026] Importing the gasification agent into the gasifier from the first air inlet, or from the first air inlet and the second air inlet;

[0027] Among them, the gasification temperature in the reaction section of the gasifier is T1, and the ash softening temperature of the solid fuel is ST, then 900°C ≤ T1 ≤ (ST - 100°C);

[0028] When the solid fuel is fed through the first feed port, a gasifying agent composed of air, oxygen-enriched air, or oxygen and steam is introduced into the first air inlet, and the oxygen concentration is 15% - 45%; a gasifying agent composed of oxygen and steam is introduced into the second air inlet, the oxygen concentration is 30% - 65%, and the gas inlet velocity of the second air inlet is 30 m / s - 70 m / s; the apparent fluidization velocity in the throat section is set to 1.05 - 1.5 times the terminal settling velocity of the median particle size of the hydrocarbon solid fuel fed; the apparent velocity in the reaction section is 2.5 m / s - 6 m / s; the apparent air velocity in the upper straight section of the expansion section is 3 m / s - 4 m / s;

[0029] When the solid fuel is fed through the second feed port, a gasifying agent composed of air or oxygen-enriched air and steam is introduced into the first air inlet, and the oxygen concentration is 15% - 45%; the second air inlet is not opened or the gasifying agent introduced is recycled gas or carbon dioxide; the apparent fluidization velocity in the throat section is set to 1.05 - 1.5 times the terminal settling velocity of the median particle size of the hydrocarbon solid fuel fed; the apparent velocity in the reaction section is 4 m / s - 8 m / s; the apparent air velocity in the upper straight section of the expansion section is 3 m / s - 4 m / s, and the gas phase residence time in the expansion section is 4 s - 8 s;

[0030] The proportion of the gasifying agent introduced through the first air inlet in the total gasifying agent introduced into the gasifier is 70% - 100%, and the gasifying agent is mainly introduced through the first air inlet.

[0031] Compared with the prior art, at least one of the beneficial effects that can be achieved by the present invention is as follows: by arranging a throat section in the gasifier, the furnace chamber of the gasifier is divided into a reaction section at the bottom and an expansion section at the upper part, breaking the annular core structure of the traditional fluidized bed for the separation of solid materials and gas phase in the dilute phase region, forming a central jet in the expansion section, increasing the internal circulation, and strengthening the heat and mass transfer between gas and solid, which is beneficial to improving the carbon conversion rate of the gasification device.

[0032] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the content specifically pointed out in the specification and the drawings. Description of the Drawings

[0033] The drawings are only used for the purpose of showing specific embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference signs represent the same components.

[0034] Figure 1 It is a schematic structural diagram of a multi-stage fluidized bed gasification device in the specific implementation manner;

[0035] Figure 2 It is a schematic diagram of the tangential circle distribution of the air inlet pipe on the expansion section in the specific implementation manner;

[0036] Figure 3 It is another schematic structural diagram of the multi-stage fluidized bed gasification device in the specific implementation manner.

[0037] Reference numerals:

[0038] 1 - Gasifier; 101 - First air inlet; 102 - Slag discharge port; 103 - Return port; 104 - Second air inlet; 105 - Discharge port; 106 - First feed port; 107 - Second feed port; 11 - Reaction section; 111 - Slag discharge pipe; 112 - Return pipe; 12 - Houkou section; 13 - Expansion section; 131 - Air inlet pipe; 2 - Gas-solid separator; 201 - Material inlet; 202 - First outlet; 203 - Second outlet; 3 - Return device. Specific implementation manner

[0039] The following will specifically describe the preferred embodiments of the present invention in conjunction with the drawings, wherein the drawings form a part of the present invention and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0040] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the term "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] The terms "top", "bottom", "above...", "below" and "on..." used throughout the description are relative positions with respect to the components of the device, such as the relative positions of the top and bottom linings inside the device. It can be understood that the device is multifunctional and is independent of its orientation in space.

[0042] The normal working surface of the present invention can be a plane or a curved surface, can be inclined, or can be horizontal. For the convenience of description, the embodiments of the present invention are placed on a horizontal plane and used on the horizontal plane, and "high and low" and "up and down" are defined accordingly.

[0043] Embodiment 1

[0044] This embodiment discloses a multi-stage fluidized bed gasification device, as Figures 1 to 3As shown, it includes:

[0045] The gasifier 1 includes a reaction section 11, a throat section 12, and an expansion section 13 that are connected in sequence from bottom to top. The cavity diameter of the throat section 12 is smaller than the cavity diameters of the reaction section 11 and the expansion section 13 respectively, so that the materials in the reaction section 11 can enter the expansion section 13 after being accelerated by the throat section 12 to form a central jet.

[0046] The gas-solid separator 2 is communicated with the expansion section 13.

[0047] The return feeder 3 is communicated with the gas-solid separator 2 and the reaction section 11, so as to transport the solid materials separated by the gas-solid separator 2 back to the reaction section 11.

[0048] The cavity diameter of the throat section 12 is smaller than the cavity diameters of the reaction section 11 and the expansion section 13 respectively, which means that the diameter at any place of the cavity of the throat section 12 is smaller than the diameter at any place of the cavities of the reaction section 11 and the expansion section 13, so as to ensure the acceleration effect of the throat section 12 on the materials and enable the materials to enter the expansion section 13 in the form of a central jet.

[0049] The multi-stage fluidized bed gasification device of the present invention (hereinafter referred to as the gasification device) divides the furnace chamber of the gasifier 1 into a bottom reaction section 11 and an upper expansion section 13 by arranging a throat section 12 in the gasifier 1, breaking the annular core structure of the traditional fluidized bed for solid-gas separation in the dilute phase region, forming a central jet in the expansion section 13, increasing the internal circulation, and strengthening the heat transfer and mass transfer between gas and solid, which is beneficial to improving the carbon conversion rate of the gasification device.

[0050] The present invention constructs a central upward jet through the throat section 12 for gas acceleration and the expansion section, and forms an internal circulation particle flow form in which the sidewall particles move downward. The solid materials coalesce in the lower conical section of the expansion section 13. In the dilute phase region compared with the traditional fluidized bed, the particle concentration in this region shows several times growth.

[0051] It should be noted that the gasifier 1 is provided with a cavity (i.e., the furnace chamber) for material reaction, and the cavity is divided into a reaction section 11, a throat section 12, and an expansion section 13. The diameters mentioned below for the three are all the diameters of the corresponding cavities, and the shapes mentioned for the three are also the shapes of the corresponding cavities.

[0052] The centerlines of the reaction section 11, the throat section 12, and the expansion section 13 coincide approximately (including completely) with the centerline A-A of the gasifier 1.

[0053] The reaction section 11 is provided with a first air inlet 101, a slag discharge port 102 and a return material port 103. Specifically, the first air inlet 101 is located at the bottom end face of the reaction section 11, and the primary air g1 enters the gasifier 1 from the first air inlet 101, that is, the primary air g1 enters the reaction section 11 from the first air inlet 101. The slag discharge port 102 is located at the bottom of the side wall of the reaction section 11. The return material port 13 is located on the side wall of the reaction section 11, and the return material port 13 is higher than the slag discharge port 102 on the side wall.

[0054] A slag discharge pipe 111 extending obliquely downward is provided at the slag discharge port 102 to quickly discharge the bottom slag d generated at the bottom of the reaction section 11. The included angle between the slag discharge pipe 111 and the center line A-A is α, and 30° ≤ α ≤ 60°. Preferably, α = 45°.

[0055] A return material pipe 112 extending obliquely upward is provided at the return material port 103 to quickly introduce the solid material separated by the gas-solid separator 2 into the reaction section 11 through the return material pipe 112 by the return feeder 3. The included angle between the return material pipe 112 and the center line A-A is β, and 30° ≤ β ≤ 60°. Preferably, β = 45°.

[0056] Preferably, the return material port 103 is located in the transition area between the dense phase area and the dilute phase area, ensuring that the solid material returned by the return feeder through the return material pipe 112 can smoothly return to the reaction section 11. At the same time, it can ensure that the returned solid material can quickly mix with the solid material in the dense phase area, conduct heat transfer and reaction, and enable the returned solid material to further react. Specifically, the transition area between the dense phase area and the dilute phase area is controlled at the return material port 103 by controlling the pressure difference or the stock volume in the reaction section through slag discharge.

[0057] In this embodiment, the middle part (i.e., the straight section of the reaction section 11) of the reaction section 11 is cylindrical, the upper part of the reaction section 11 is in the shape of a frustum of a cone, that is, the diameter of the upper part of the reaction section 11 gradually decreases from bottom to top, the lower part of the reaction section 11 is in the shape of an inverted frustum of a cone, that is, the diameter of the lower part of the reaction section 11 gradually increases from bottom to top, and a section extends vertically downward from the bottom end of the lower part of the reaction end to form the bottom of the reaction section 11, that is, the bottom diameter of the reaction section 11 is equal to the diameter of the lower bottom end. The return material port 103 is arranged in the middle of the reaction section 11, the first air inlet 101 is located at the lower end face of the bottom, and the slag discharge port 102 is located at the side wall of the bottom. With such an arrangement, on the one hand, it is convenient for the materials in the reaction section 11 to concentrate and enter the throat section 12 in the upper part; on the other hand, it is convenient for the waste slag to be concentrated and discharged from the slag discharge port 102 in the lower part; at the same time, a flow field with a more uniform particle concentration distribution and a more intense internal circulation is constructed.

[0058] To ensure the reaction effect of the reaction section 11, the ratio of the length of the upper or lower part to the length of the middle part of the reaction section 11 is not greater than 1:4, and the length of the bottom part is not greater than the length of the lower part.

[0059] The height h of the reaction section 11 11 It is the height of the first air inlet 101 at the bottom of the reaction section 11 from the interface between the reaction section 11 and the outlet section 12 .

[0060] h 11 The range is 0.1 to 0.6 times of the characteristic height h of the reaction section 11, the oxygen in the gasifying agent entering through the first air inlet 101 is completely reacted in the reaction section, and the pressure gradient dP / dh at the top of the reaction section 11 is in the range of 1 kPa / m to 0.2 kPa / m.

[0061] The characteristic height h of the reaction section is a function of the particle size of the reaction material, the fluidization velocity, the circulation flow rate and the height H of the gasifier, and its calculation formula is as follows:

[0062] h=0.518×Ar -0.3 ×Fr 0.0755 ×(G s / (ρ g ×V g )) 0.311 ×H

[0063] Where Ar is the Archimedean constant, Fr is the Froude number, G s is the circulation flow rate, ρ g is the gas density, V g is the apparent velocity.

[0064] The Houkou section 12 is connected downwardly to the reaction section 11 and upwardly to the expansion section 13, so as to accelerate the material in the reaction section 11 and introduce it into the expansion section 13. Specifically, the function of the Houkou section 12 is mainly to accelerate the raw coal gas generated in the reaction section 11 with the solid material in the Houkou section 12, and enter the expansion section 13 in the form of a central jet, while reducing the amount of solid material in the expansion section 13 that adheres to the wall and refluxes to the reaction section 11.

[0065] In order to ensure the acceleration effect of the Houkou section 12, the ratio of the length of the Houkou section 12 to the diameter of the Houkou section 12 is 1 to 3:1, and preferably, the ratio of the length of the Houkou section 12 to the diameter of the Houkou section 12 is 1.5 to 2:1. The structure is set so that the particles entering the Houkou from the reaction section are fully accelerated and enter the expansion section at a higher speed, which is conducive to quickly taking away the heat generated by the reaction at the lower part of the expansion section; and the drag force support for the solid materials adhering to the wall reflux prolongs the residence time of the solid materials adhering to the wall reflux in the expansion section and the Houkou section, or the solid materials adhering to the wall reflux are transported to the expansion section again, which prolongs the residence time of the particles in the expansion section, which is conducive to providing carbon conversion rate and coal gas calorific value.

[0066] In this embodiment, the shape of the hopper section 12 is cylindrical, and the diameter of the hopper section 12 is equal to the top diameter of the upper part of the reaction section, that is, the upper top of the reaction section extends vertically upward to form the hopper section 12.

[0067] The bottom end of the expansion section 13 is connected to the hopper section 12, and the upper part of the expansion section 13 is connected to the gas-solid separator 2.

[0068] Specifically, the lower part of the expansion section 13 is in the shape of an inverted truncated cone, that is, the diameter of the lower part of the expansion section 13 gradually increases from bottom to top, and a solid material accumulation area is formed in the lower part of the expansion section 13. Preferably, a second air inlet 104 is provided in the lower part of the expansion section 13, and the secondary air g2 enters the expansion section 13 through the second air inlet 104 to prevent the solid material from accumulating in the expansion section 13.

[0069] To facilitate the control of the air inlet of the second air inlet 104, an air inlet pipe 131 is provided at the second air inlet 104. Preferably, the air inlet pipe 131 of the second air inlet 104 is inclined downward or upward, so that the secondary air g2 entering from the air inlet pipe 131 enters the lower part of the expansion section 13 obliquely upward or obliquely downward.

[0070] The opening direction of the second air inlet 104 (i.e., the air inlet direction of the air inlet pipe 131) forms an angle γ with the horizontal plane (a plane perpendicular to the center line A-A), -45° ≤ γ ≤ 45°, preferably, -15° ≤ γ ≤ 15°. The secondary air promotes the diffusion of the solid material adhering to the wall back to the center and mixes with the secondary air to form a stable solid material flow field with the center upward and the side wall refluxing. It should be noted that when γ is negative, the air inlet pipe 131 extends obliquely upward from the second air inlet, that is, the air inlet direction of the air inlet pipe 131 enters the lower part of the expansion section obliquely downward; when γ is positive, the air inlet pipe 131 extends obliquely downward from the second air inlet, that is, the air inlet direction of the air inlet pipe 131 enters the lower part of the expansion section obliquely upward; when γ is zero, the air inlet pipe 131 is horizontally arranged, that is, the air inlet direction of the air inlet pipe 131 is perpendicular to the center line A-A. In this embodiment, γ = 15°.

[0071] Preferably, a plurality of second air inlets 104 are provided in the lower part of the expansion section 13, and a corresponding number of air inlet pipes 131 are provided, that is, the air inlet pipes 131 and the second air inlets 104 are arranged in one-to-one correspondence. The plurality of second air inlets 104 are located on the same horizontal plane, that is, the plurality of second air inlets 104 are set at the same height on the expansion section 13. The angles of the plurality of air inlet pipes 131 with the horizontal plane are the same.

[0072] Furthermore, the plurality of air inlet pipes 131 introduce the secondary air g2 in a tangential circle form, that is, the air inlet directions of the plurality of air inlet pipes 131 are tangent to the same circle O (circle O is also called the tangential circle), as Figure 2As shown, the center line A-A passes through the center of the circle O, and the diameter D of the circle O is smaller than the diameter at the position where the second air inlet is opened in the expansion section 13. Preferably, the diameter D of the circle O is greater than or equal to the diameter of the hopper section 12 and less than or equal to 0.85 times the diameter at the position where the second air inlet is opened in the expansion section 13. In the lower part of the expansion section, a flow field is formed where the solid materials form a central jet flowing upward and the side wall flows downward in a backflow; the concentration of the solid material particles is the highest within the range of 0.85 times the cross-sectional diameter and the diameter of the hopper section. Therefore, taking the diameter within this range as the tangential circle diameter range will effectively promote the mixing, mass transfer, heat transfer, and reaction between the secondary air and the solid materials, thus strengthening the gasification reaction. At the same time, adopting the tangential circle form to introduce the secondary air promotes the mixing of the solid materials flowing downward along the side wall and the diffusion towards the center, avoiding the problems of overheating of the wall surface and slagging caused by introducing the secondary air tangentially.

[0073] The number of the intake pipes 131 is not less than three. In this embodiment, the number of the intake pipes 131 is four, and they are evenly distributed on the lower side wall of the expansion section 13.

[0074] The middle part of the expansion section 13 (i.e., the straight section of the expansion section 13) is cylindrical in shape, and the diameter of the middle part of the expansion section 13 is equal to the diameter of the top end of the lower part of the expansion section 13, that is, the top end of the lower part of the expansion section 13 extends vertically upward to form the middle part of the expansion section 13. Preferably, the ratio of the length of the lower part of the expansion section 13 to the length of the middle part of the expansion section does not exceed 1:7. In this embodiment, the ratio of the length of the lower part of the expansion section 13 to the length of the middle part of the expansion section is 1:9.

[0075] The top of the expansion section 13 is arch-shaped, having a good mechanical structure.

[0076] The expansion section 13 is provided with a discharge port 105, and the discharge port 105 is communicated with the gas-solid separator 2. The discharge port 105 is located in the upper part of the side wall of the expansion section 13. Specifically, the discharge port 105 is located at a position near the top of the middle side wall of the expansion section 13, that is, the discharge port 105 is located at the upper end of the middle side wall of the expansion section 13.

[0077] The gasifier 1 is provided with two feed ports, namely a first feed port 106 and a second feed port 107, to meet the requirements for the preparation of high-calorific value gas and syngas. Specifically, the first feed port 106 is arranged in the reaction section 11, and the second feed port 107 is arranged in the expansion section 13.

[0078] The first feed port 106 is arranged in the middle of the reaction section 11, and its position is higher than the return material port 103.

[0079] The second feed inlet 107 is arranged at the middle part of the expansion section 13 near the lower part of the expansion section 13, that is, the second feed inlet 107 is arranged at the lower end of the middle part of the expansion section 13, and the position of the second feed inlet 107 is lower than that of the discharge outlet 105.

[0080] For convenient feeding, a feed pipe is provided obliquely upward at the feed inlet (including the first feed inlet 106 and the second feed inlet 107), and the included angle between the feed pipe and the center line is δ, 15° ≤ δ ≤ 75°. In this embodiment, δ = 70°.

[0081] When the gasification device is used to produce gas, a high methane content is required. Feed through the second feed inlet 107 and close the first feed inlet 106. At this time, the second air inlet 104 does not admit air (that is, the second air inlet is closed) or the secondary air uses recycled gas or carbon dioxide, and the recycled gas is the gas after dust removal of the gas separated by the gas-solid separator 2.

[0082] When the gasification device is used to produce syngas, a low methane content is required. Feed through the first feed inlet 106, close the second feed inlet 107, and the secondary air uses a mixture of oxygen and steam.

[0083] The height of the expansion section 13 of the gasification furnace 1 is greater than the height of the reaction section 11, and the height of the reaction section 11 is higher than the height of the Houkou section 12. Specifically, the ratio of the height of the reaction section 11 to the height of the expansion section 13 is not greater than 1:4, and the ratio of the height of the Houkou section 12 to the height of the reaction section 11 is not greater than 1:3.

[0084] The gas-solid separator 2 is provided with a material inlet 201, a first outlet 202 and a second outlet 203. The material inlet 201 is communicated with the discharge outlet 105 so that the material discharged from the discharge outlet 105 enters the gas-solid separator 2 through the material inlet 201 for gas-solid separation. The gas separated by the gas-solid separator 2 is guided to the downstream device for treatment through the first outlet 202, and the separated solid is discharged through the second outlet 203 and returned to the reaction section 11 through the return feeder 3 for reprocessing.

[0085] The material inlet 201 is located at the upper end of the side wall of the gas-solid separator, the first outlet 202 is located at the top of the gas-solid separator, and the second outlet 203 is located at the bottom of the gas-solid separator.

[0086] The return feeder 3 is respectively communicated with the second outlet 203 and the return feed inlet 103 so as to transport the solid material separated by the gas-solid separator 2 back to the gasification furnace 1 for further processing.

[0087] The return feeder 3 is a non-mechanical return device, which can be a U-valve, a J-valve, an N-valve, an L-valve, or a jet conveyor. The return feeder 3 can automatically adjust the riser material level height according to the pressure change in the gasification furnace cavity.

[0088] The gasifier 1 of the present invention includes two reaction zones, namely a reaction section 11 and an expansion section 13. That is, the reaction section 11 is the primary reaction zone, and the expansion section 13 is the secondary reaction zone. The gasification temperature T1 of the reaction section 11 is such that for the material (such as hydrocarbon solid fuel) fed into the gasifier 1 through the feed port, the ash softening temperature is ST, and 900°C ≤ T1 ≤ (ST - 100°C), and the oxygen reacts completely within the reaction section 11.

[0089] The proportion of the primary air g1 in the total air volume fed into the gasifier ranges from 70% to 100%, preferably from 70% to 80%.

[0090] When the gasification device produces fuel gas, the primary air g1 is a gasifying agent composed of air or oxygen-enriched air and steam (i.e., air / oxygen-enriched air + steam), the oxygen concentration is 15% to 45%, the secondary air g2 is recycled coal gas or carbon dioxide or there is no secondary air, and the feeding is carried out through the second feed port 107. The apparent fluidization velocity of the throat section 12 is set to the terminal settling velocity U of the median particle size d of the hydrocarbon solid fuel fed in. 50 of t1.05 to 1.5 times. The superficial velocity of the reaction section 11 is 4 m / s to 8 m / s, preferably 5 m / s to 6 m / s. The superficial wind speed of the upper straight section in the expansion section 13 is 3 m / s to 4 m / s, and the gas-phase residence time in the expansion section 13 is 4 s to 8 s. By setting the superficial velocity and residence time, the hydrocarbon solid fuel fed into the expansion section 13 forms a central jet at the bottom of the expansion section 13 and the Houkou section 12, strengthening the heat transfer between gas and solid and prolonging the residence time of the hydrocarbon solid fuel. The hydrocarbon solid fuel with a smaller particle size is entrained by the raw gas ejected from the Houkou section 12 to the upper-middle part of the furnace, where pyrolysis, cracking and gasification reactions occur, cracking the tar into high-calorie light hydrocarbon gases. At the same time, since the raw gas in the Houkou section 12 is anaerobic and will not consume the methane-rich gas generated by pyrolysis in the expansion section 13, the methane content of the gas is increased. When the hydrocarbon solid fuel with a median particle size enters the Houkou section 12 or the bottom of the expansion section 13, it cannot enter the reaction section 11 under the drag of the raw gas in the Houkou section 12. At the same time, when leaving the Houkou section 12 and the bottom of the expansion section 13, it cannot be entrained by the raw gas and leave the furnace due to the decrease in the superficial velocity, so it is in a suspended state and has a long residence time, and the volatile matter is fully released; at the same time, it undergoes a gasification reaction with carbon dioxide from the reaction section 11 under the action of high temperature, is correspondingly broken into fine particles, and finally is entrained by the raw gas and leaves the furnace. Although the coarse hydrocarbon solid fuel cannot be lifted and suspended by the raw gas in the Houkou section 12, the falling speed of the coarse particles is delayed, so that the residence time of the coarse particles from entering the furnace to entering the reaction section 11 > 3 s, that is, more than 80% of the volatile matter of the coarse particles has been released. Therefore, the solid materials entering the reaction section 11 include coarse particles with released volatile matter and fine particles with released volatile matter and captured by the gas-solid separator 2 and returned through the return feeder 3. These two types of particles have the characteristics of large specific surface area and no volatile matter. Therefore, a higher gasification temperature and a higher fluidization velocity are beneficial to strengthening the gasification reaction and preventing slagging caused by uneven fluidization.

[0091] When the gasification device produces syngas, it is desired that the methane content in the gas is low. Feed through the first feed port 106, and the primary air g1 is a gasifying agent composed of air, oxygen-enriched air or oxygen and steam (i.e., air / oxygen-enriched air / oxygen + steam), and the oxygen concentration is 15% to 45%. The secondary air g2 is a gasifying agent composed of oxygen and steam (i.e., oxygen + steam), the oxygen concentration is 30% to 65%, and the nozzle velocity of the secondary air g2 is 30 m / s to 70 m / s. The apparent fluidization velocity of the Houkou section 12 is set to the terminal settling velocity U of the median particle size d of the fed hydrocarbon solid fuel 50 of t1.05 to 1.5 times, the apparent velocity in the reaction section is 2.5 m / s to 6 m / s, and the apparent air velocity in the upper-middle straight section of the expansion section 13 is 3 m / s to 4 m / s. By setting the apparent velocity, the unreacted hydrocarbon solid fuel leaving with the raw gas in the reaction section 11 forms a central jet at the bottom of the expansion section 13 after being accelerated through the Houkou section 12. The hydrocarbon solid fuel is accelerated through the Houkou section 12 and enters the expansion section 13, and then moves downward along the wall with the decrease in velocity, forming a fountain-like internal circulation, significantly increasing the particle concentration in this area. The tangent circle of the secondary air g2 coincides with the area with a high particle concentration, and the gas-solid mixing is strengthened through the tangent circle jet, thereby strengthening the gasification reaction, increasing the gasification temperature in this area, reforming the raw gas from the reaction section, and oxidizing methane and light hydrocarbon gases in the raw gas to produce CO, CO2, and H2, thereby increasing the carbon conversion rate of the system and reducing the methane concentration.

[0092] The proportion of the gasification agent introduced through the first air inlet in the total gasification agent introduced into the gasifier is 70% to 100%, and the gasification agent is mainly introduced through the first air inlet.

[0093] According to an embodiment of the present invention, the gasifier includes two or more combinations composed of the Houkou section 12 and the expansion section 13, that is, the gasifier 1 includes, from top to bottom, the reaction section 11, the Houkou section 12 + the expansion section 13,..., the Houkou section 12 + the expansion section 13. It should be noted that at this time, the length ratio of the reaction section, the Houkou section, and the expansion section 13 of the gasifier is different from the foregoing, but generally still satisfies that the length of the Houkou section < the length of the reaction section < the length of the expansion section.

[0094] The structure of the uppermost expansion section 13 is different from that of the foregoing expansion section 13 (as Figure 1 shown) in that the second feed port is not provided. The structure of the lowermost expansion section 13 is different from that of the foregoing expansion section 13 in that the top shape of the expansion section 13 is a frustum of a cone rather than an arch, and the discharge port is not provided, that is, the top diameter of the expansion section 13 gradually increases from bottom to top. The structure of the expansion section 13 in the middle position is different from that of the foregoing expansion section 13 in that the second feed port and the discharge port are not provided, and the top shape of the expansion section 13 is a frustum of a cone, that is, the top diameter of the expansion section 13 gradually increases from bottom to top. Except for the uppermost expansion section 13, the bottom and top diameters of the remaining expansion sections 13 are equal to the diameter of the Houkou section 12.

[0095] An air inlet and an air inlet pipe are provided at the lower part of all the expansion sections 13, and the air inlet direction of the air inlet pipe of the same expansion section is set in a tangent circle manner. That is, when the gasifier 1 includes N expansion sections 13, the gasifier 1 can have N + 1 secondary air entering the gasifier from different air inlets.

[0096] Preferably, along the gasifier center line A-A upwards, the length of the Houkou section 12 gradually shortens, the length of the latter Houkou section 12 being 0.8 to 1 times that of the previous Houkou section 12, and the superficial velocity of the Houkou section 12 gradually decreases along the center line A-A upwards, the superficial velocity of the latter Houkou section being 0.65 to 0.85 times that of the previous Houkou section. Along the axis upwards, the particle size gradually decreases. Therefore, the requirements for the distance for accelerating the particles and the gas velocity by the Houkou section gradually decrease. Therefore, on the premise of meeting the particle acceleration, gradually reducing the length of the Houkou section and the velocity of the Houkou section is beneficial to reducing the energy consumption caused by particle acceleration.

[0097] Preferably, the superficial velocity in the middle of the expansion section 13 gradually decreases along the center line A-A upwards.

[0098] As Figure 3 shown, the gasifier 1 includes two groups of Houkou sections 12 and expansion sections 13. An air inlet is provided at the lower part of the upper expansion section 13, and the tertiary air g3 is introduced from this air inlet, and no feed inlet is provided in the upper expansion section 13. No discharge port is provided in the lower expansion section 13, and the top shape of the lower expansion section 13 is a truncated cone. A second feed inlet is provided in the middle of the lower expansion section 13, and an air inlet is provided at the lower part of the lower expansion section 13, and the secondary air g2 is introduced from this air inlet.

[0099] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0100] (1) The multi-stage fluidized bed gasification device of the present invention divides the furnace into a bottom reaction section and an upper expansion section through the Houkou section, and correspondingly performs gasifying agent staging, breaking the annular core structure of the traditional fluidized bed for the separation of solid materials and gas phase in the dilute phase region, forming a central jet in the expansion section, increasing the internal circulation, and introducing the secondary air in a tangential circle manner, strengthening the heat transfer and mass transfer between gas and solid, which is beneficial to improving the carbon conversion rate;

[0101] (2) The multi-stage fluidized bed gasification device of the present invention can simultaneously meet the requirements of producing fuel gas and synthesis gas, expanding the application range of the applied gasification device, being more flexible and convenient to use, and saving resources;

[0102] (3) The present invention provides a second air inlet with a tangential circle form at the lower part of the expansion section, which not only forms a cooperation with the central jet to push the particles on the side wall to converge towards the center, and mix and react the gasifying agent with the particles, but also avoids the problem of over-temperature slagging on the side wall caused by the tangential entry of the second gasifying agent;

[0103] (4) The multi-stage fluidized bed gasification device of the present invention can produce fuel gas, enabling the pyrolysis and gasification of hydrocarbon solid fuels to be decoupled from combustion in the same furnace, avoiding the ineffective consumption of high-calorific value light hydrocarbons generated by pyrolysis by oxygen in the gasifying agent in the traditional fluidized bed where the pyrolysis, gasification, and combustion of hydrocarbon solid fuels are coupled in the same furnace. Therefore, the calorific value of the fuel gas can be significantly increased. At the same time, the porous solid material with a large specific surface area formed after pyrolysis entering the reaction section for gasification is conducive to improving the carbon conversion rate;

[0104] (5) The multi-stage fluidized bed gasification device of the present invention can produce syngas. The reaction section is used as the gasification reaction area, and the bottom of the expansion section is used as the reforming area. Through the acceleration in the throat section and the deceleration in the expansion section, a region with a relatively high particle concentration and a relatively high internal circulation intensity is formed at the bottom of the expansion section. Tangential secondary air is introduced into this region to strengthen the mixing, heat transfer, and reaction between gas-solid and gas-gas phases, which is conducive to improving the carbon conversion rate and reducing the methane content in the coal gas, reducing the burden of syngas purge gas, and improving the conversion efficiency of syngas.

[0105] Example Two

[0106] This example discloses a gasification method for a multi-stage fluidized bed gasification device, which is realized through the multi-stage fluidized bed gasification device provided in Example One. The gasification method includes:

[0107] Import the solid fuel into the gasification furnace 1 through the first feed port 106 or the second feed port 107;

[0108] Import the gasifying agent into the gasification furnace through the first air inlet 101, or the first air inlet 101 and the second air inlet 104;

[0109] Among them, the gasification temperature in the reaction section 11 of the gasification furnace 1 is T1, and the ash softening temperature of the solid fuel is ST, then 900°C ≤ T1 ≤ (ST - 100°C).

[0110] The gasifying agent entering from the first air inlet 101 is the primary air g1, and the proportion of the primary air g1 in the total air volume introduced into the gasification furnace ranges from 70% to 100%, preferably 70% to 80%.

[0111] The gasifying agent entering from the second air inlet 104 is the secondary air g2.

[0112] When the solid fuel is fed through the first feed port 106, an oxidizing agent composed of air, oxygen-enriched air, or oxygen and steam is introduced through the first air inlet, and the oxygen concentration is 15% to 45%; an oxidizing agent composed of oxygen and steam is introduced through the second air inlet 107, the oxygen concentration is 30% to 65%, and the gas inlet velocity of the second air inlet 107 is 30 m / s to 70 m / s; the apparent fluidization velocity of the Houkou section 12 is set to 1.05 to 1.5 times the terminal settling velocity Ut of the median particle size d50 of the hydrocarbon solid fuel fed; the apparent velocity of the reaction section is 2.5 m / s to 6 m / s; the apparent wind velocity of the upper straight section in the expansion section 13 is 3 m / s to 4 m / s. At this time, syngas is produced by the gasification device.

[0113] When the solid fuel is fed through the second feed port 107, an oxidizing agent composed of air or oxygen-enriched air and steam is introduced through the first air inlet, and the oxygen concentration is 15% to 45%; the second air inlet 107 is not opened or the introduced oxidizing agent is recycled coal gas or carbon dioxide; the apparent fluidization velocity of the Houkou section 12 is set to 1.05 to 1.5 times the terminal settling velocity Ut of the median particle size d50 of the hydrocarbon solid fuel fed; the apparent velocity of the reaction section 11 is 4 m / s to 8 m / s, preferably 5 m / s to 6 m / s; the apparent wind velocity of the upper straight section in the expansion section 13 is 3 m / s to 4 m / s, and the gas residence time in the expansion section 13 is 4 s to 8 s. At this time, high-calorific value gas is produced by the gasification device.

[0114] The proportion of the oxidizing agent introduced through the first air inlet in the total oxidizing agent introduced into the gasifier is 70% to 100%, and the oxidizing agent is mainly introduced through the first air inlet.

[0115] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A multi-stage fluidized bed gasification device, characterized in that, Comprising: A gasifier, including a reaction section, a throat section, and an expansion section connected in sequence from bottom to top. The cavity diameter of the throat section is smaller than that of the reaction section and the expansion section respectively, so that the materials in the reaction section can enter the expansion section after being accelerated through the throat section to form a central jet. A gas-solid separator communicated with the expansion section. A return feeder communicated with the gas-solid separator and the reaction section to return the solid materials separated by the gas-solid separator to the reaction section.

2. The multi-stage fluidized bed gasification device according to claim 1, characterized in that, The reaction section is provided with a first air inlet, a slag discharge port, and a return material port. The first air inlet is located at the bottom end face of the reaction section. The slag discharge port is located at the bottom of the side wall of the reaction section. The return material port is located on the side wall of the reaction section, and the return material port is higher than the slag discharge port on the side wall.

3. The multi-stage fluidized bed gasification device according to claim 2, wherein, The return material port is located in the transition region between the dense phase region and the dilute phase region.

4. The multi-stage fluidized bed gasification device according to claim 1, characterized in that, The ratio of the length of the throat section to the diameter of the throat section is 1 - 3:

1.

5. The multi-stage fluidized bed gasification device according to claim 1, characterized in that, The diameter of the lower part of the expansion section gradually increases from bottom to top. The lower part of the expansion section is provided with a second air inlet, and an air inlet pipe is provided at the second air inlet. The included angle between the air inlet pipe and the horizontal plane is γ, and -45° ≤ γ ≤ 45°.

6. The multi-stage fluidized bed gasification device according to claim 5, wherein The lower part of the expansion section is provided with a plurality of the second air inlets, and correspondingly, the same number of the air inlet pipes are provided. The air inlet directions of the plurality of air inlet pipes are tangent to the same circle, the central axis of the gasifier passes through the center of the tangent circle, and the diameter of the tangent circle is smaller than the diameter of the expansion section where the second air inlet is opened.

7. The multi-stage fluidized bed gasification device according to any one of claims 1 to 6, characterized in that, The gasifier is provided with a first feed port and a second feed port. The first feed port is arranged in the reaction section, and the second feed port is arranged in the expansion section.

8. The multi-stage fluidized bed gasification device according to claim 7, characterized in that, When the gasification device is used to produce syngas, the first feed port is opened and the second feed port is closed to feed through the first feed port. When the gasification device is used to produce fuel gas, the second feed port is opened and the first feed port is closed to feed through the second feed port.

9. The multi-stage fluidized bed gasification device according to claim 1, wherein The gasifier includes two or more combinations composed of a throat section and an expansion section.

10. A gasification method of a multi-stage fluidized bed gasification device, implemented by the multi-stage fluidized bed gasification device according to any one of claims 1 - 9. The gasification method includes: Importing solid fuel into the gasifier through the first feed port or the second feed port. Importing the gasifying agent into the gasifier from the first air inlet, or from the first air inlet and the second air inlet. Wherein, the gasification temperature of the reaction section of the gasifier is T1, and the ash softening temperature of the solid fuel is ST, then 900°C ≤ T1 ≤ (ST - 100°C). When the solid fuel is fed through the first feed port, the gasifying agent composed of air, oxygen-enriched air or oxygen and steam is introduced into the first air inlet, and the oxygen concentration is 15% - 45%; the gasifying agent composed of oxygen and steam is introduced into the second air inlet, and the oxygen concentration is 30% - 65%, and the gas inlet velocity of the second air inlet is 30m / s - 70m / s; the apparent fluidization velocity of the throat section is set to 1.05 - 1.5 times the terminal settling velocity of the median particle size of the fed hydrocarbon solid fuel; the apparent velocity of the reaction section is 2.5m / s - 6m / s. The apparent wind speed in the upper straight section of the extended section is 3 m / s to 4 m / s; When the solid fuel is fed through the second feed port, an oxidizing agent composed of air or oxygen-enriched air and steam is introduced into the first air inlet, and the oxygen concentration is 15% to 45%; the second air inlet is not opened or the introduced oxidizing agent is recycled coal gas or carbon dioxide; the apparent fluidization velocity in the Houkou section is set to 1.05 to 1.5 times the terminal settling velocity of the median particle size of the fed hydrocarbon solid fuel; the apparent velocity in the reaction section is 4 m / s to 8 m / s; the apparent wind speed in the upper straight section of the extended section is 3 m / s to 4 m / s, and the gas phase residence time in the extended section is 4 s to 8 s; The proportion of the oxidizing agent introduced through the first air inlet in the total oxidizing agent introduced into the gasifier is 70% to 100%, and the oxidizing agent is mainly introduced through the first air inlet.

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