Powdered low-rank coal / biomass fast pyrolysis device and process

Abstract

The present application relates to low rank coal / biomass energy clean, efficient, cascade polygeneration technology field, and relates to a kind of pulverous low rank coal / biomass rapid pyrolysis device and process, including pyrolysis reactor, the shell of pyrolysis reactor is composed of cylinder and cone, cylinder and cone are integrally formed in upper and lower, both sides of cylinder top end are equipped with feed inlet, feed inlet is tangent to cylinder;Cylinder top center is equipped with upper exhaust pipe;Tapered middle lower part is equipped with stop piece, the upper part of stop piece is conical, the lower part is cylindrical shell and bottom is empty, tapered lower end is welded with discharge pipe, the lower part of stop piece is equipped with lower exhaust pipe, discharge pipe and lower exhaust pipe are coaxial, the cylinder, cone, discharge pipe, upper exhaust pipe and lower exhaust pipe are coaxial, the lower part of discharge pipe is connected with expansion bin, overflow port is equipped on the side of expansion bin.The above structural members cooperate with each other, build the reactor of centrifugal force field and gas cyclone combination, realize the rapid heating of granular raw material while effectively removing the dust in pyrolysis oil gas.

Description

Technical Field

[0001] This invention relates to the field of clean, efficient, and multi-stage co-generation technology for low-rank coal / biomass energy, and particularly to the clean conversion technology of low-rank coal / biomass pyrolysis and gasification or combustion. This invention is applicable to the catalytic pyrolysis, catalytic depolymerization, and co-pyrolysis of powdered low-rank coal / biomass. Background Technology

[0002] Of the total proven coal reserves, low-rank coal accounts for approximately 47%. Due to its lower degree of coalification, low-rank coal has a lower energy density and is unsuitable for direct use as fuel. However, it has a higher hydrogen-to-carbon ratio and better reactivity. In particular, its abundant volatile matter, including a large amount of aromatic structures and cyclic hydrocarbons, makes it an excellent raw material for co-producing oil and high-value-added chemicals. Biomass resources share similar characteristics with low-rank coal, with my country's total exploitable reserves estimated at approximately 700 million tons of standard coal equivalent. Achieving efficient and clean utilization of low-rank coal / biomass through technologies such as pyrolysis and catalytic depolymerization is of great significance.

[0003] The generation of pulverized coal is unavoidable during coal mining and biomass collection, and the output of pulverized coal is constantly increasing with the improvement of fully mechanized mining levels. However, existing pyrolysis technologies cannot directly utilize pulverized coal; it needs to be shaped before being fed into the furnace for pyrolysis, increasing the cost of clean and efficient coal utilization. A crucial reason for this is the difficulty in effectively separating the fine particles generated after pulverized coal pyrolysis from high-boiling-point organic matter, causing blockages in downstream pipelines and hindering long-term operation of the equipment. Patent application CN103881761A proposes using circulating ash to form a particle bed to filter small particles in pyrolysis oil and gas. While this technical solution effectively purifies the oil and gas, it increases the contact time between the high-temperature circulating ash and the pyrolysis oil and gas, raising the oil and gas temperature and promoting secondary reactions, resulting in low liquid product yield. Patent application CN106336907A proposes a cyclone pyrolysis high-throughput circulating gasification device and process, utilizing high-throughput solid heat-carrying particles to rapidly heat pulverized coal or biomass, and using centrifugal force to remove dust, thus purifying the oil and gas. The reactor structure proposed in this invention application has the following shortcomings:

[0004] First, the heat-carrying particles are transported by a carrier gas, and a large amount of the carrier gas mixes with the pyrolysis oil and gas during the outflow from the reactor. This dilutes the oil and gas concentration, increasing the difficulty of subsequent oil and gas extraction; on the other hand, the carrier gas temperature is higher than that of the pyrolysis oil and gas, and the mixing of the two raises the oil and gas temperature, intensifying secondary reactions and reducing the yield of liquid products. Second, the gas flow in the reactor first descends and then turns back upwards; the distance between the turning point and the feed inlet is called the cyclone length. Within the cyclone length range, gas-solid convection is significant, resulting in efficient heat transfer; outside this range, the heat transfer efficiency is significantly reduced due to weakened convection. Furthermore, the cyclone length decreases with increasing particle flux; therefore, high particle flux operating conditions limit the reactor's heat transfer efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a rapid pyrolysis device and process for powdered low-rank coal / biomass, which solves the problems of existing pyrolysis devices where heat transfer efficiency is limited by particle throughput, pyrolysis oil and gas temperature rises due to prolonged contact time with high-temperature materials during dust removal, oil and gas concentration is easily diluted by carrier gas, increasing the difficulty of subsequent oil and gas extraction and exacerbating secondary reactions, thus reducing the yield of liquid products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A rapid pyrolysis device for powdered low-rank coal / biomass includes a pyrolysis reactor. The shell of the pyrolysis reactor is composed of a cylindrical body and a conical body, which are integrally formed. Feed inlets are located on both sides of the top of the cylindrical body, and both feed inlets are tangent to the cylindrical body. An upper exhaust pipe is located at the center of the top of the cylindrical body. A baffle is located in the lower part of the conical body. The upper part of the baffle is conical, and the lower part is a cylindrical shell with a hollow bottom. A discharge pipe is welded to the lower end of the conical body. A lower exhaust pipe is located below the baffle. The discharge pipe and the lower exhaust pipe are coaxial, and the diameter of the discharge pipe is larger than the diameter of the lower exhaust pipe. The cylindrical body, the conical body, the discharge pipe, the upper exhaust pipe, and the lower exhaust pipe are all coaxial. An expansion chamber is connected below the discharge pipe, and an overflow port is located on the side of the expansion chamber.

[0008] The lower exhaust pipe is L-shaped, with the horizontal outlet end passing through the discharge pipe and connecting to the external pipeline of the device to quickly extract the enriched pyrolysis oil and gas.

[0009] The outlet end of the lower exhaust pipe is higher than the expansion chamber, and a support frame is welded below the lower exhaust pipe to support it.

[0010] A rapid pyrolysis process for powdered low-rank coal / biomass includes the following steps:

[0011] S1: Carrier gas transports powdered low-rank coal / biomass and heat-carrying particles into the pyrolysis reactor of the fast pyrolysis unit through two feed inlets. The particles aggregate toward the side wall of the reactor under centrifugal force, and the pyrolysis raw materials come into full contact with the heat-carrying particles, resulting in a fast pyrolysis reaction.

[0012] S2: As the carrier gas descends, it continuously converges towards the center, and 40% of the carrier gas turns back upward and flows out from the exhaust pipe at the top of the cylinder.

[0013] S3: The carrier gas that does not turn back during the downward process carries pyrolysis oil and gas into the lower exhaust pipe through the baffle and flows into the subsequent tar recovery and processing unit.

[0014] S4: Under the action of gravity, the particles enter the expansion chamber through the gap formed by the discharge pipe and the lower exhaust pipe along the inner wall of the cone shell. The expansion chamber stores the particles and flows out through the overflow port under the action of the conveying air.

[0015] Pyrolysis Principle: The heat carrier particles and pyrolysis feedstock particles enter from different inlets with the carrier gas, then rotate downwards. During this process, the pyrolysis feedstock particles rapidly heat up to the reaction temperature through conduction, convection, and radiation. As the temperature rises, the downward airflow continuously converges towards the center and then reverses upwards, exiting the reactor through the upper exhaust pipe. The gaseous products of the pyrolysis reaction are carried into the center by the carrier gas, while dust and solid pyrolysis products remain concentrated on the sidewalls under centrifugal force, achieving the first stage of oil-gas dust removal and purification. A baffle is used to regulate the flow pattern at the contracted section of the shell, preventing the mixing of wall particles towards the center caused by turbulence. Additionally, the baffle guides the downward rotating airflow in the central area towards the sidewalls before reversing and entering the lower exhaust pipe. During this process, fine particles carried in the oil-gas are ejected, achieving a second stage of oil-gas dust removal and purification. The heat carrier particles and solid pyrolysis products form a sealed particle bed within the expansion chamber, preventing gas from flowing out through the expansion chamber.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0017] (1) By using the lower exhaust pipe, the airflow will not be completely reversed at a certain height in the reactor, ensuring that the cyclone length can run through the reactor and maintain efficient heat transfer throughout the entire process of particle rotation and downward movement; at the same time, the cone shape of the baffle can increase the airflow rotation speed and enhance convective heat transfer.

[0018] (2) The carrier gas is diverted by two exhaust pipes, which effectively alleviates the dilution effect of the carrier gas on the pyrolysis oil and gas and avoids the problem of difficulty in subsequent oil and gas extraction.

[0019] (3) During the heating stage of low-rank coal / biomass, a large flow of gas is beneficial to enhance gas-solid convection heat transfer and increase the heating rate of low-rank coal / biomass particles. After the heating stage is completed, part of the gas flow turns back and flows out of the system from the upper exhaust pipe. Since the pyrolysis reaction occurs less, this part of the carrier gas contains almost no pyrolysis oil and gas. After the pyrolysis oil and gas is produced, only part of the downward carrier gas carries the cylindrical body through the baffle into the lower exhaust pipe.

[0020] (4) The pyrolysis oil and gas are carried by the carrier gas into the central area of ​​the reactor. Since the high-temperature heat-carrying particles are concentrated on the side wall, the temperature in the central area is lower, and the generated pyrolysis oil and gas will not rise significantly. At the same time, due to the proximity of the exhaust pipe, the oil and gas can flow out of the reactor quickly, effectively avoiding the secondary reaction caused by prolonged stay in the high-temperature zone, and ensuring the tar yield. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of an embodiment of the present invention;

[0023] Explanation of reference numerals in the attached drawings: 1. Shell; 2. Upper exhaust pipe; 3. Feed inlet; 4. Baffle; 5. Lower exhaust pipe; 6. Discharge pipe; 7. Overflow port; 8. Expansion chamber. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown, a rapid pyrolysis device for powdered low-rank coal / biomass includes a pyrolysis reactor. The shell 1 of the pyrolysis reactor is composed of a cylindrical body and a conical body, which are integrally formed. Feed inlets 3 are provided on both sides of the top of the cylindrical body, and both feed inlets 3 are tangent to the cylindrical body. An upper exhaust pipe 2 is provided at the center of the top of the cylindrical body. A baffle 4 is provided in the lower part of the conical body. The upper part of the baffle 4 is conical, and the lower part is a cylindrical shell with an empty bottom. A discharge pipe 6 and a lower exhaust pipe 5 are provided at the lower end of the conical body, and the discharge pipe 6 and the lower exhaust pipe 5 are coaxial. The diameter of the discharge pipe 6 is larger than the diameter of the lower exhaust pipe 5. The cylindrical body, the conical body, the discharge pipe 6, the upper exhaust pipe 3, and the lower exhaust pipe 5 are all coaxial. The lower exhaust pipe is L-shaped, and its outlet end is higher than the expansion chamber and connected to an external pipeline. The enriched pyrolysis oil and gas are quickly extracted, and the expansion chamber 8 is connected below the discharge pipe 6. The expansion chamber 8 is provided with an overflow port 7 on its side. The carrier gas is diverted through the upper and lower exhaust pipes to alleviate the dilution of the pyrolysis oil and gas by the carrier gas. At the same time, efficient gas-solid convection heat exchange can be achieved in the entire reactor space. The baffle and the lower exhaust pipe together form a baffle structure, forming a functional unit for the re-dust removal and purification of the pyrolysis oil and gas. The lower exhaust pipe is relatively short and is connected to the pipeline outside the device of this invention through the outlet end to quickly extract the enriched pyrolysis oil and gas. The above structural components work together to build a special reactor that combines centrifugal force field and gas vortex, so as to achieve rapid heating of particulate raw materials while effectively removing dust from the pyrolysis oil and gas. It is suitable for the pyrolysis of powdery low-rank coal / biomass.

[0026] like Figure 2 As shown, the dimensions of the relevant structures of this pyrolysis device are limited. The cylinder diameter D is selected as the baseline dimension. The remaining dimensions of the components are as follows: The cylinder diameter of the pyrolysis reactor shell is a / D = 0.25~0.75, b / D = 0.085~0.37, H / D = 1~4, Hc / D = 1~4, He / D = 1~2, Hd / D = 1~2, Df / D = 0.25~0.5, De / D = 0.3~0.5, Ds / D = 0.5~0.75, α = 45-75°. The specific steps of the pyrolysis process are as follows:

[0027] S1: Carrier gas transports coal and / or biomass into the pyrolysis reactor of the fast pyrolysis unit from different feed inlets 3. The flow ratio of carrier gas to particulate material is approximately 1.2 to 1.8. The coal and / or biomass are transported at a rate of 500 K·s. -1 ~800 K·s -1The temperature is increased at a rate of 550℃~600℃ to initiate the pyrolysis reaction;

[0028] S2: After the pyrolysis reaction starts, about 40% of the carrier gas turns back upward and flows out from the upper exhaust pipe 2. The remaining gas continues to descend with the particles. This step slows down the dilution effect of the carrier gas on the pyrolysis oil and gas.

[0029] S3: Gaseous pyrolysis products are carried by the carrier gas and converge towards the center of the reactor, reducing the concentration of gaseous products on the surface of the feed particles, increasing the rate of mass transfer of volatile components from the feed particles to the outside of the particles, and reducing the residence time of volatiles within the high-temperature particles. Furthermore, there are virtually no high-temperature particles at the center of the reactor, and the temperature is nearly 200°C lower than that of the sidewalls. Due to these two reasons, the temperature rise after the pyrolysis oil and gas is not high, and the secondary reaction is weakened. Therefore, the yield of oil substances is approximately 10% higher than that of the Gejin dry distillation process.

[0030] S4: The downward airflow that converges into the center is guided by the cone of the baffle 4, flows towards the side wall first, and then turns back into the lower exhaust pipe 5. Under the combined action of centrifugal separation and inertial separation, 90% of the particles are removed, thus achieving purification.

[0031] S5: The granular material enters the expansion chamber 8 through the discharge pipe 6, first forming a granular bed seal, preventing 98% of the pyrolysis oil gas and carrier gas from flowing out of the expansion chamber overflow port 7, and guiding the gas to flow out of the device from the upper exhaust pipe 2 and the lower exhaust pipe 5. The granules move towards the overflow port under the action of the fluidizing air and flow out of the device from there.

[0032] Comparative Example 1

[0033] Invention patent number 2016108779287 proposes a pyrolysis reactor similar to this invention, also using particulate heat carriers to pyrolyze coal and / or biomass. However, because the airflow in this reactor first descends and then reverses upwards, the reversal point is relatively close to the top exhaust pipe due to the high particle flux, resulting in a shorter time for the convective heat transfer mechanism to take effect. Furthermore, after the airflow reverses, the carrier gas velocity is significantly reduced, greatly diminishing the gas-solid convective heat transfer effect. Therefore, under the same conditions, the particle heating rate is less than 300 K·s. -1 The effect of increasing oil yield was not significant. Furthermore, the pyrolysis gas and carrier gas rise together, inevitably mixing. On one hand, the large carrier gas flow rate will dilute the oil and gas after mixing, increasing the difficulty of subsequent separation; on the other hand, the high carrier gas temperature will promote further reaction of the pyrolysis gas itself, reducing oil yield. Overall, the tar-like substances obtained in Comparative Example 1 are comparable to the yield of the Gekin carbonization process.

[0034] The reason why this invention is superior to Comparative Example 1 is that:

[0035] First, in the cyclone reactor of Comparative Example 1, all gas flow exits through the top exhaust pipe, causing the downward carrier gas entering from the inlet to completely reverse and rise in the upper part of the reactor, reducing the effective convective heat transfer space. In this invention, a bottom exhaust pipe is provided, ensuring that the gas swirl fills the entire reactor, allowing convective heat transfer to function throughout the entire reactor area. Simultaneously, the conical shape of the baffle 4 increases the airflow rotation speed, enhancing convective heat transfer. The heat transfer rate of this invention can reach 500 K·s. -1 ~800 K·s -1 This achieves the required heating rate for rapid pyrolysis, thereby increasing tar yield.

[0036] Secondly, in Comparative Example 1, there is only one exhaust pipe at the top, through which both carrier gas and pyrolysis oil gas flow out, inevitably mixing and diluting the concentration of pyrolysis oil gas. However, Comparative Example 1 is a reactor designed for rapid heat transfer, and a large flow rate of carrier gas is beneficial for enhancing gas-solid convective heat transfer. This contradiction is difficult to balance in Comparative Example 1. The present invention uses two exhaust pipes, one above and one below, to achieve a carrier gas diversion effect. During the preheating stage of low-rank coal / biomass, the large flow rate of gas enhances gas-solid convective heat transfer, increasing the heating rate of the low-rank coal / biomass particles. After preheating, approximately 40% of the gas flow reverses and flows out of the system through the top exhaust pipe. Due to the relatively small amount of pyrolysis reaction, this portion of the carrier gas contains almost no pyrolysis oil gas. After the carrier gas produces pyrolysis oil gas, it flows out of the reactor carried by the remaining downward-flowing carrier gas. The dilution effect of the carrier gas is significantly reduced.

Claims

1. A pulverized low rank coal / biomass fast pyrolysis apparatus comprising a pyrolysis reactor, characterized by, The shell (1) of the pyrolysis reactor is composed of a cylinder and a cone, which are integrally formed. Inlet ports (3) are provided on both sides of the top of the cylinder, and both inlet ports are tangent to the cylinder. An upper exhaust pipe (2) is provided at the center of the top of the cylinder. A baffle (4) is provided in the lower part of the cone. The upper part of the baffle (4) is conical, and the lower part is a cylindrical shell with an empty bottom. A discharge pipe (6) is welded to the lower end of the cone. A lower exhaust pipe (5) is provided below the baffle (4). The discharge pipe (6) and the lower exhaust pipe (5) are coaxial, and the discharge pipe (6) is... The diameter is larger than that of the lower exhaust pipe (5). The cylinder, cone, discharge pipe (6), upper exhaust pipe (2) and lower exhaust pipe (5) are all coaxial. The lower part of the discharge pipe (6) is connected to the expansion chamber (8). The side of the expansion chamber (8) is provided with an overflow port (7). The lower exhaust pipe (5) is "L" shaped. The horizontal outlet end passes through the discharge pipe (6) and is connected to the external pipe of the device. The outlet end of the lower exhaust pipe (5) is higher than the expansion chamber (8). A support frame is welded below the lower exhaust pipe (5) to support the lower exhaust pipe.

2. A pyrolysis process based on the pulverized low rank coal / biomass fast pyrolysis apparatus of claim 1, characterized in that, The specific steps are as follows: S1: The carrier gas transports the powdered low-rank coal / biomass and the heat-carrying particles into the pyrolysis reactor of the rapid pyrolysis device through two feed ports (3). The particles gather towards the side wall of the reactor under centrifugal force, and the pyrolysis raw materials come into full contact with the heat-carrying particles, resulting in a rapid pyrolysis reaction. S2: The carrier gas continuously converges towards the center during the downward process, and 40% of the carrier gas turns back upward and flows out from the exhaust pipe (2) at the top of the cylinder; S3: The carrier gas that does not turn back during the downward process carries the pyrolysis oil gas and is guided by the baffle (4) into the lower exhaust pipe (5) and flows into the subsequent tar recovery and processing device; S4: Under the action of gravity, the particles enter the expansion chamber (8) through the gap formed by the discharge pipe (6) and the lower exhaust pipe (5) along the inner wall of the cone shell. The expansion chamber (8) stores the particles and flows out through the overflow port (7) under the action of the conveying air.

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