Biomass coal mixture with high biomass content and production equipment and method thereof

Abstract

The invention relates to the technical field of biomass resource utilization, and particularly discloses a biomass coal mixture with high biomass content and production equipment and method thereof. The production equipment comprises a hammer mill for crushing and drying biomass granules, a medium-speed coal mill for crushing and drying coal, a bag-type dust collector and an induced draft fan connected with a gas outlet of the bag-type dust collector, the mixing pipe horizontally penetrates through the bag-type dust collector, and ports at two ends of the mixing pipe are respectively connected with discharge ports of the hammer mill and the medium-speed coal mill; the flow guide pipe is arranged in the bag-type dust collector, a top end port of the flow guide pipe is communicated with the material mixing pipe, and a bottom end port of the flow guide pipe faces a discharge port of the bag-type dust collector. According to the invention, the biomass particles and the coal are respectively crushed and pulverized, so that the pulverized coal and the biomass powder which are high in sphericity degree, small in length-diameter ratio and better in flowability are respectively prepared, and high-proportion mixing of the biomass in the pulverized coal can be realized; therefore, the coal powder with excellent fluidity can be used for driving the biomass powder with poor fluidity to enter the entrained-flow bed gasification furnace.

Description

Technical Field

[0001] This invention relates to the field of biomass resource utilization technology, and in particular to a biomass-coal mixture with high biomass content and its production equipment and method. Background Technology

[0002] The modern coal chemical industry is one of the largest carbon-emitting industries in my country. Biomass is the only renewable carbon source. Blending biomass with coal in a certain proportion to form biomass-coal mixed powder, which can be used as feedstock for fluidized bed gasification, can significantly reduce carbon emissions from coal chemical plants and is one of the important directions for carbon reduction in modern coal chemical enterprises.

[0003] Biomass has a complex composition and high fiber content, which is detrimental to the stable operation of pneumatic conveying feeding units. Traditionally, biomass needs to be pyrolyzed and carbonized at high temperatures to become coke, which is then fed into a conventional roller mill and mixed with pulverized coal for grinding. However, most of the volatile matter in biomass is lost during the pyrolysis stage, resulting in significant energy loss and underutilization of energy.

[0004] When the proportion of biomass in a pulverized coal gasification unit is low, biomass pellets can be directly fed into a roller mill and mixed with pulverized coal for grinding. However, industrial practice shows that: firstly, the flue gas temperature used for pulverized coal drying is as high as 320℃, limiting the proportion of pellets and requiring strict control, otherwise the safety risks of grinding are significant; secondly, taking wheat straw as an example, when ground together with pulverized coal in a roller mill, the wheat straw pellets have a large aspect ratio (>3) and low sphericity (<0.4), indicating that roller mills used for pulverized coal preparation are unsuitable for preparing fine biomass powder. Industrial practice shows that when the proportion of biomass pellets exceeds 15%, the powder feeding system begins to show obvious bridging and arching phenomena, and the flowability of the mixed powder deteriorates.

[0005] In summary, achieving a high proportion of biomass mixing in pulverized coal and high-pressure feeding of biomass-coal mixed powder to meet the carbon reduction requirements of fluidized bed gasification feedstock are key technologies for biomass-coupled pulverized coal gasification processes. Summary of the Invention

[0006] Based on this, the purpose of this invention is to provide a biomass-coal mixture with high biomass content, as well as its production equipment and method, to achieve high-proportion mixing of biomass in coal powder and high-pressure feeding of biomass-coal mixed powder with high biomass content, thereby meeting the need for carbon reduction of feedstock in fluidized bed gasification.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention first provides a production equipment for biomass-coal mixture with high biomass content, which includes a hammer mill for crushing and drying biomass pellets, a medium-speed coal mill for crushing and drying coal, a bag filter, and an induced draft fan connected to the gas outlet of the bag filter; a mixing pipe horizontally penetrates the bag filter and its two ends are respectively connected to the discharge ports of the hammer mill and the medium-speed coal mill; a guide pipe is set inside the bag filter, its top end is connected to the mixing pipe and its bottom end faces the discharge port of the bag filter.

[0009] In this invention, under the action of an induced draft fan, pulverized coal and biomass powder enter the mixing pipe from both ends. The pulverized coal and biomass powder collide at the center of the bag filter, forming a uniformly mixed powder. This mixed powder then falls along the guide pipe, flows out from the guide pipe's outlet, and finally settles at the bottom of the bag filter's cone, exiting from the bag filter's outlet. This invention places the mixing pipe and guide pipe within the bag filter, mixing the dried biomass powder and dried pulverized coal powder first in the mixing pipe, and then introducing them into the bag filter through the guide pipe. This prevents segregation of the two powders due to differences in density, particle size, etc., during their entry into the filter bags.

[0010] As a further improvement to the above-mentioned solution of the present invention, the hammer mill is a hammer-type or blade-type mill, and is driven to rotate by a rotor. When the rotor of the hammer mill rotates at high speed, due to the centrifugal force, the hammers become radial (for rotors with suspended hammers). Biomass pellets enter the machine and are immediately crushed into pellets by the impact and tearing action of the hammers. The biomass powder is discharged from the discharge screen at the bottom of the machine. If the larger powder cannot pass through the screen, it is left to be impacted by the hammers again until it passes through the screen.

[0011] As a further improvement to the above-mentioned solution of the present invention, the center of the mixing pipe is located on the central axis of the bag filter; the top end of the guide pipe is connected to the center of the mixing pipe.

[0012] As a further improvement to the above-mentioned solution of the present invention, the distance between the bottom end of the guide pipe and the discharge port of the bag filter is 1-10m, preferably 2-5m.

[0013] As a further improvement of the above-mentioned scheme of the present invention, the apparent gas velocity in the mixing pipe is 5-25 m / s, preferably 10-20 m / s; the apparent gas velocity in the guide pipe is 1-10 m / s, preferably 2-5 m / s.

[0014] The present invention also provides a method for producing a biomass coal mixture with high biomass content, which uses the production equipment described above and includes the following steps: S1. Add centimeter-sized biomass pellets to a hammer mill and pulverize them to the micron level and dry them to obtain dry biomass powder; S2. Add coal to a medium-speed coal mill and pulverize it to the micron level and dry it to obtain dry coal powder; S3. Start the induced draft fan to transport the dried biomass powder and the dried coal powder to the mixing pipe by inert gas. The dried biomass powder and the dried coal powder collide in the mixing pipe to form a uniformly mixed powder, which falls along the guide pipe and flows out from the outlet of the guide pipe. Finally, it settles at the bottom of the bag filter cone to obtain a biomass-coal mixture. The biomass powder content in the biomass-coal mixture can reach 60wt%.

[0015] As a further improvement to the above-mentioned solution of the present invention, in step S1, the drying is achieved by introducing a 25-300℃ hot inert gas (mainly inert gases such as carbon dioxide and nitrogen, with an oxygen content of <6%) into the hammer mill; the biomass pellets are centimeter-sized pellets formed by pressing raw biomass for easy transportation and conversion, and are agricultural and forestry waste pellets, wherein the agricultural and forestry waste is at least one of wheat straw, rice straw, cotton straw, and corn straw.

[0016] As a further improvement to the above-mentioned scheme of the present invention, in step S1, the dried biomass powder has a particle size <2000μm, a moisture content <15wt%, a sphericity >0.4, and an aspect ratio <4; preferably, the dried biomass powder has a particle size of 50-800μm, a moisture content <8wt%, a sphericity >0.5, and an aspect ratio <3.

[0017] As a further improvement to the above-mentioned solution of the present invention, in step S2, the drying is achieved by introducing a 100-400℃ hot inert gas (mainly inert gases such as carbon dioxide and nitrogen, with an oxygen content of <6%) into the medium-speed coal mill.

[0018] As a further improvement to the above-described scheme of the present invention, in step S2, the particle size of the dried coal powder is <1000μm and the moisture content is <10wt%; preferably, the particle size of the dried coal powder is <200μm and the moisture content is <2wt%.

[0019] The present invention also provides a biomass coal mixture with high biomass content, which is prepared by the production method described above.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention processes biomass pellets and coal separately, producing coal powder and biomass powder with high sphericity, low aspect ratio, and excellent flowability. This allows for a high proportion of biomass mixed in the coal powder, with the biomass powder content reaching 60 wt%. The excellent flowability of the coal powder allows it to carry the less flowable biomass powder into the fluidized bed gasifier. Without altering the original coal powder feeding system (atmospheric pressure coal powder storage silo, coal powder lock hopper, feeding tank, and conveying pipelines, etc.), the gasification requirements for high-biomass-coal mixed powder feedstock with high biomass blending ratios can be met, thus satisfying the need for carbon reduction in fluidized bed gasification feedstock. The biomass-coal mixed powder obtained by this invention can be pressurized to 5.0 MPa through the coal powder lock hopper and then fed into the fluidized bed gasifier at 4.0 MPa through the feeding tank. The biomass-coal mixed powder concentration conveyed through the corresponding pneumatic conveying pipeline can be controlled at 100-400 kg / m³. 3 The conveying speed is 5-15m / s, and the conveying capacity is 8-30t / h. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a production equipment for a high biomass content biomass coal mixture according to an embodiment of the present invention; Attached reference numerals: 1. Mixing pipe; 2. Bag filter; 3. Guide pipe. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0024] Reference Figure 1 This embodiment proposes a production equipment for biomass coal mixture with high biomass content, which includes a hammer mill (not shown), a medium-speed coal mill (not shown), a mixing pipe 1, a bag filter 2, an induced draft fan (not shown), and a guide pipe 3.

[0025] The hammer mill is used to crush centimeter-sized biomass pellets to a particle size <2000μm (preferably 50-800μm), while simultaneously drying them with a 25-300℃ heat-carrying inert gas (mainly carbon dioxide, nitrogen, etc., with an oxygen content <6%) to a moisture content <15wt% (preferably <8wt%). The dried biomass powder is discharged from its outlet. The biomass powder has a sphericity >0.4 and an aspect ratio <4; preferably, a sphericity >0.5 and an aspect ratio <3. In this embodiment, the biomass pellets are centimeter-sized pellets formed by pressing raw biomass for easy transportation and conversion. They are agricultural and forestry waste pellets, specifically at least one of wheat straw, rice straw, cotton straw, and corn straw. In this embodiment, the hammer mill is a hammer mill type and is driven to rotate by a rotor. When the rotor of the hammer mill rotates at high speed, due to the centrifugal force, the hammers become radial (for rotors with suspended hammers). Biomass pellets are crushed into pellets by the impact and tearing action of the hammers as they enter the machine. The biomass powder is discharged from the discharge screen at the bottom of the machine. Larger powders that cannot pass through the screen are left to be impacted by the hammers again until they pass through the screen.

[0026] The medium-speed coal mill is a conventional medium-speed coal mill, which is used to crush coal to a particle size of <1000μm (preferably <200μm) and dry it to a moisture content of <10wt% (preferably <2wt%) by a hot inert gas (mainly carbon dioxide, nitrogen and other inert gases, with an oxygen content of <6%) at 100-400℃, and then discharge the dried coal powder from its outlet.

[0027] The mixing pipe 1 horizontally penetrates the bag filter 2, and its two ends, B and C, are connected to the discharge ports of the hammer mill and the medium-speed coal mill, respectively, via conveying pipes. The center K of the mixing pipe 1 is located on the central axis of the bag filter 2. The guide pipe 3 is installed inside the bag filter 2, with its top end connected to the center of the mixing pipe 1 and its bottom end M facing the discharge port O of the bag filter 2. The distance between the bottom end M of the guide pipe 3 and the discharge port O of the bag filter is 1-10m, preferably 2-5m. The gas outlet A of the bag filter 2 is connected to an induced draft fan. Under the action of the induced draft fan, pulverized coal and biomass powder enter the mixing pipe 1 from both ends of the mixing pipe. The pulverized coal and biomass powder collide at the center of the bag filter 2 to form a uniformly mixed powder, which falls along the guide pipe 3 and flows out from the outlet of the guide pipe 3. Finally, it settles at the bottom of the cone of the bag filter and is discharged from the outlet of the bag filter 2. The apparent gas velocity in the mixing pipe 1 is 5-25 m / s (preferably 10-20 m / s), and the apparent gas velocity in the guide pipe 3 is 1-10 m / s (preferably 2-5 m / s).

[0028] This embodiment utilizes the aforementioned production equipment for a high-biomass-content biomass-coal mixture to propose a production method for a high-biomass-content biomass-coal mixture, which includes the following steps: S1. Add centimeter-sized biomass pellets to a hammer mill and pulverize them to the micron level and dry them to obtain dry biomass powder; S2. Add coal to a medium-speed coal mill and pulverize it to the micron level and dry it to obtain dry coal powder; S3. Start the induced draft fan to transport the dry biomass powder and dry coal powder to the mixing pipe 1 by means of inert gas to achieve uniform mixing of the two, so as to obtain biomass and coal mixed powder. The biomass and coal mixed powder falls along the guide pipe 3 and flows out from the outlet of the guide pipe 3, settling at the bottom of the cone of the bag filter 2. In this embodiment, the biomass powder content in the biomass and coal mixed powder can reach 60wt%.

[0029] Taking wheat straw pellets as an example, the equipment of this invention is used to prepare biomass coal mixtures with high biomass content. Specifically: a medium-speed coal mill produces 8 t / h of pulverized coal with a moisture content of 2 wt% and a particle size d90 < 100 μm; a hammer mill produces 12 t / h of wheat straw powder with a moisture content of 5 wt%, a particle size d90 < 800 μm, and a sphericity of 0.6; the bottom port M of the guide pipe is connected to the bag filter dust collector. The distance from the discharge port O is 3m; biomass powder enters mixing pipe 1 from port B with an apparent air velocity of 12m / s; pulverized coal enters mixing pipe 1 from port C with an apparent air velocity of 15m / s; after the pulverized coal and biomass powder collide and mix at point K, they flow downwards along guide pipe 3 with an apparent air velocity of 2m / s, exiting from outlet M and entering the bottom of the bag filter 2 cone. The biomass powder in the mixed powder at the bottom of the cone is evenly distributed, and the biomass powder content is 60wt% according to the sample analysis. A level gauge is installed near the bottom of the bag filter 2 cone to monitor the material level, ensuring that the distance from the bottom of the cone does not exceed 2.5m, to prevent excessive material level from clogging outlet M.

[0030] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0031] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A production equipment for a biomass-coal mixture with high biomass content, characterized in that, It includes a hammer mill for crushing and drying biomass pellets, a medium-speed coal mill for crushing and drying coal, a bag filter, and an induced draft fan connected to the gas outlet of the bag filter; a mixing pipe runs horizontally through the bag filter and its two ends are connected to the discharge ports of the hammer mill and the medium-speed coal mill, respectively; a guide pipe is installed inside the bag filter, its top end is connected to the mixing pipe, and its bottom end faces the discharge port of the bag filter.

2. The production equipment for high biomass content biomass coal mixture according to claim 1, characterized in that, The center of the mixing pipe is located on the central axis of the bag filter; the top end of the guide pipe is connected to the center of the mixing pipe.

3. The production equipment for high biomass content biomass coal mixture according to claim 1, characterized in that, The distance between the bottom end of the guide pipe and the outlet of the bag filter is 1-10m; a level gauge is installed inside the bag filter.

4. The production equipment for high biomass content biomass coal mixture according to claim 1, characterized in that, The apparent gas velocity in the mixing pipe is 5-25 m / s, and the apparent gas velocity in the guide pipe is 1-10 m / s.

5. A method for producing a biomass-coal mixture with high biomass content, characterized in that, It employs the production equipment described in any one of claims 1-4, and includes the following steps: S1. Add centimeter-sized biomass pellets to a hammer mill and pulverize them to the micron level and dry them to obtain dry biomass powder; S2. Add coal to a medium-speed coal mill and pulverize it to the micron level and dry it to obtain dry coal powder; S3. Start the induced draft fan to transport the dried biomass powder and the dried coal powder to the mixing pipe by means of inert gas. The dried biomass powder and the dried coal powder collide in the mixing pipe to form a uniformly mixed powder, which falls along the guide pipe and flows out from the outlet of the guide pipe. Finally, it settles at the bottom of the bag filter to obtain the biomass-coal mixture.

6. The method for producing a high-biomass-content biomass coal mixture according to claim 5, characterized in that, In step S1, the drying is achieved by introducing a 25-300℃ hot inert gas into the hammer mill; the biomass pellets are agricultural and forestry waste pellets, and the agricultural and forestry waste is at least one of wheat straw, rice straw, cotton straw, and corn straw.

7. The method for producing a high biomass content biomass coal mixture according to claim 5, characterized in that, In step S1, the dried biomass powder has a particle size of <2000μm, a moisture content of <15wt%, a sphericity of >0.4, and an aspect ratio of <4.

8. The method for producing a biomass-coal mixture with high biomass content according to claim 5, characterized in that, In step S2, the drying is achieved by introducing a 100-400℃ hot inert gas into the medium-speed coal mill.

9. The method for producing a biomass-coal mixture with high biomass content according to claim 5, characterized in that, In step S2, the dried coal powder has a particle size of <1000μm and a moisture content of <10wt%.

10. A biomass-coal mixture with high biomass content, characterized in that, It is prepared using the production method described in any one of claims 5-9.

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