A biomass pyrolysis system and its process method

Abstract

The present invention discloses a biomass pyrolysis system and its process method, which includes a biomass pyrolysis furnace. The biomass pyrolysis furnace successively includes a pyrolysis product conveying section, a heat carrier and pyrolysis product separation section, a circulating pyrolysis reaction section, and a heat carrier output section from top to bottom. A product outlet is provided at the top of the pyrolysis product conveying section; the circulating pyrolysis reaction section includes a draft tube, a draft area, and an annulus area; multiple rows of openings are provided on the wall of the draft tube, and the openings in each row are arranged at equal intervals. The draft tube is coaxially arranged with the circulating pyrolysis reaction section. The draft area is located inside the draft tube, and the annulus area is located between the draft tube and the circulating pyrolysis reaction section. A heat carrier outlet is provided at the bottom of the heat carrier output section. The present invention realizes the effective control of the pyrolysis reaction depth and reaction process of large-particle biomass in the pyrolysis reactor, improves the particle contact environment, increases the particle heat exchange efficiency, regulates the pyrolysis reaction time, increases the yield of target products, has a simple process flow, and is convenient to operate.

Description

Technical Field

[0001] The present invention relates to the field of biomass energy, and particularly relates to a biomass pyrolysis system and a process method thereof. Background Art

[0002] In China, with the vigorous development of agriculture and forestry, there are a large number of agricultural wastes (such as straw, rice husks, etc.) and a large number of forestry wastes (such as wood chips, palm, etc.) every year. Based on the increasing demand for clean and convenient gaseous fuels with high combustion efficiency, such as liquefied petroleum gas, it is an urgent need for national production to reasonably utilize biomass such as straw and efficiently convert it into clean and utilizable fuels.

[0003] Biomass pyrolysis refers to the process of converting biomass into low-molecular substances such as charcoal, liquid, and gas through thermochemical conversion under the condition of air isolation or supply of a small amount of air. Pyrolysis can obtain products such as fuel oil, wood tar, wood gas, and charcoal. By controlling the corresponding conditions (mainly reaction temperature, heating rate, residence time) parameters in pyrolysis, different pyrolysis products can be obtained. Biomass pyrolysis technology can convert biomass with low energy density, which is difficult to handle by conventional methods, into gaseous, liquid, and solid products with high energy density at a relatively low cost and continuous production process, reducing the volume of biomass, facilitating storage and transportation, and at the same time, high-value-added chemicals can be extracted from bio-oil.

[0004] Chinese Patent Application Publication No. CN107903924A discloses an upward heat storage type pulverized coal rapid pyrolysis reaction system and method. The system includes an upward heat storage type pyrolysis furnace, a cyclone separator, a semicoke condenser, and an oil and gas condenser. The upward heat storage type pyrolysis furnace includes a furnace body and radiation tubes, and the coal material is heated through the radiation tubes. Its disadvantages are as follows: (1) In the pyrolysis furnace, pulverized coal contacts and exchanges heat with the radiation tubes, and the pulverized coal pyrolyzes to generate products such as semicoke and oil and gas. The product semicoke and oil and gas are easily adhered and accumulated on the surface of the radiation tubes, affecting the heat transfer effect and service life of the radiation tubes; (2) The pulverized coal particles of this device are fed from the bottom of the pyrolysis furnace and pyrolyzed from top to bottom to obtain pyrolysis products. The products are transported to the top of the pyrolysis furnace under the action of lifting gas. Therefore, the pyrolysis furnace of this device is a typical upward bed, and the residence time of pulverized coal particles in it is short, which is not conducive to the full pyrolysis of large-particle pulverized coal; (3) Multiple radiation tubes are arranged in the pyrolysis furnace, making the structure of the whole device complex, the operation cumbersome, and the energy consumption high.

[0005] Chinese Patent Publication No. CN105238426B discloses a detachable plate - type indirect heating coal pyrolysis device, which uses heat - exchange plates to heat coal materials for pyrolysis. Its deficiencies are as follows: (1) During the coal pyrolysis process, substances such as tar and dust will contaminate the heat - exchange plates, resulting in a reduction in the heat - exchange efficiency of the heat - exchange plates, increasing the frequency of regular cleaning. At the same time, the heat - exchange plates work at a relatively high temperature in the gas - solid two - phase environment for a long time, increasing the detection and replacement frequency of local components of the heat - exchange plates; (2) Multiple heat - exchange plates are loaded in the pyrolysis chamber, occupying the pyrolysis space of pulverized coal and affecting the processing capacity of the device.

[0006] Chinese Patent Publication No. CN209619268U discloses a pyrolysis furnace filled with internal components, which heats coal materials for pyrolysis by arranging multiple mutually parallel pyrolysis walls in the furnace body. Its deficiencies are as follows: (1) The pyrolysis walls are all arranged at the bottom of the furnace body, which is not conducive to the heat absorption of the coal materials in the upper part of the furnace chamber, and the heat transfer efficiency of the whole system is low; (2) The coal - loosening device in the upper part of the furnace body only avoids the extrusion of the upper coal layer on the lower coal layer, but the voids in the coal layer are still very small, which is not conducive to the heat absorption of the coal materials and it is difficult to ensure the full pyrolysis of the coal materials. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above - mentioned deficiencies existing in the prior art, and to provide a biomass pyrolysis system and its process method with reasonable structural design and simple process flow, so as to solve the problems that two solid particles at different temperatures, namely large - particle biomass and heat carrier, are mixed unevenly and have non - uniform heat exchange, the pyrolysis reaction depth and reaction process of biomass are uncontrollable, the pyrolysis is incomplete, the conversion rate is low, the yield of pyrolysis target products is low, and the secondary cracking of pyrolysis oil and gas is serious.

[0008] The technical solution adopted by the present invention to solve the above problems is: a biomass pyrolysis system, including a biomass pyrolysis furnace, which successively includes a pyrolysis product conveying section, a heat carrier and pyrolysis product separation section, a circulating pyrolysis reaction section, and a heat carrier output section from top to bottom. A product outlet is provided at the top of the pyrolysis product conveying section;

[0009] The circulating pyrolysis reaction section includes a draft tube, a draft area, and an annulus area; multiple rows of openings are provided on the tube wall of the draft tube, and each row of the openings is arranged at equal intervals. The draft tube is coaxially arranged with the circulating pyrolysis reaction section. The draft area is located inside the draft tube, and the annulus area is located between the draft tube and the circulating pyrolysis reaction section. A heat carrier outlet is provided at the bottom of the heat carrier output section.

[0010] Furthermore, the circulating pyrolysis reaction section further includes a biomass feed port, a heat carrier feed port, a gas distributor in the diversion zone, and a gas distributor in the annulus zone. The biomass feed port and the heat carrier feed port are both located on one side of the circulating pyrolysis reaction section, and the position of the biomass feed port is higher than that of the heat carrier feed port.

[0011] To ensure that the reactant biomass at the bottom of the biomass pyrolysis furnace has sufficient momentum and continuously circulates and moves from the diversion zone to the annulus zone, a gas distributor in the diversion zone and a gas distributor in the annulus zone are provided in the circulating pyrolysis reaction section. The gas distributor in the diversion zone and the gas distributor in the annulus zone are both located at the bottom of the circulating pyrolysis reaction section, and the gas distributor in the annulus zone is located between the draft tube and the gas distributor in the diversion zone.

[0012] The heat carrier output section vertically penetrates through the gas distributor in the annulus zone and the gas distributor in the diversion zone, and the top end of the heat carrier output section is flush with the top end of the gas distributor in the annulus zone.

[0013] A number of air caps are provided on both the gas distributor in the diversion zone and the gas distributor in the annulus zone. The air caps can be in the shape of a mushroom, a bell, or an embedded countercurrent column.

[0014] Furthermore, the biomass pyrolysis system further includes a biomass pre-processor, a biomass bin, a biomass feeder, a heat carrier heater, a cyclone separator, a biochar condenser, a biochar collector, a pyrolysis oil and gas condenser, an electrostatic precipitation and purification separator, a tar collector, a pyrolysis gas condenser, an oil-water separator, a pyrolysis water collector, and a pyrolysis gas collector.

[0015] The biomass outlet of the biomass pre-processor is connected to the biomass inlet of the biomass silo. The biomass outlet of the biomass silo is connected to the biomass inlet of the biomass feeder. The biomass outlet of the biomass feeder is connected to the biomass feed port. The inlet of the heat carrier heater is connected to the outlet of the heat carrier output section. The outlet of the heat carrier heater is connected to the heat carrier feed port. The product outlet of the biomass pyrolysis furnace is connected to the product inlet of the cyclone separator. The bottom outlet of the cyclone separator is connected to the biochar inlet of the biochar condenser. The condensed biochar outlet of the biochar condenser is connected to the inlet of the biochar collector. The top outlet of the cyclone separator is connected to the gas-liquid inlet of the pyrolysis oil and gas condenser. The gas-liquid outlet of the pyrolysis oil and gas condenser is connected to the gas-liquid inlet of the electrostatic precipitation and purification separator. The tar outlet of the electrostatic precipitation and purification separator is connected to the tar inlet of the tar collector. The oil-water-containing pyrolysis gas outlet of the electrostatic precipitation and purification separator is connected to the oil-water-containing pyrolysis gas inlet of the pyrolysis gas condenser. The oil-water outlet of the pyrolysis gas condenser is connected to the oil-water inlet of the oil-water separator. The tar outlet of the oil-water separator is connected to the tar inlet of the tar collector. The pyrolysis water outlet of the oil-water separator is connected to the pyrolysis water collector. The pyrolysis gas outlet of the pyrolysis gas condenser is connected to the inlet of the pyrolysis gas collector.

[0016] Further, the outlet of the pyrolysis gas collector is connected to the inlet of the biochar condenser; a heat exchanger is provided in the biochar condenser for heat exchange between the pyrolysis gas and the biochar, that is, the heat of the biochar is recovered to preheat the pyrolysis gas; the pyrolysis gas outlet of the biochar condenser is connected to the gas inlets of the diversion zone gas distributor and the annulus zone gas distributor. The pyrolysis gas (also known as "lifting gas") is transported by the diversion zone gas distributor and the annulus zone gas distributor to the bottom of the circulating pyrolysis reaction section and is used to regulate the directional circulating movement of the biomass and the heat carrier in the biomass pyrolysis furnace.

[0017] The present invention also provides a pyrolysis method for a biomass pyrolysis system, and the process is as follows:

[0018] Feed the biomass into the biomass pre-processor from the inlet of the biomass pre-processor for pre-treatment such as cleaning, drying, and pulverizing;

[0019] Feed the pre-treated biomass from the outlet of the biomass pre-processor into the biomass silo;

[0020] Feed the biomass in the biomass silo from the outlet of the biomass silo into the biomass feeder;

[0021] Feed the biomass from the biomass feeder into the biomass feed port of the biomass pyrolysis furnace;

[0022] Feed the heat carrier from the heat carrier heater into the heat carrier feed port of the biomass pyrolysis furnace;

[0023] Use the pyrolysis gas generated by pyrolysis as the lifting gas. After heat exchange through the biochar condenser, it is respectively transported from the diversion zone gas distributor and the annulus zone gas distributor to the inside of the biomass pyrolysis furnace through the tuyeres, so that the biomass and the heat carrier circulate, mix and exchange heat along the diversion zone to the annulus zone under the action of the lifting gas;

[0024] Cause the biomass to undergo pyrolysis reaction after heat exchange with the heat carrier, generating biochar, gaseous and liquid products;

[0025] Make the products generated by the pyrolysis reaction and the heat carrier after heat exchange flow from the circulating pyrolysis reaction section of the biomass pyrolysis furnace into the heat carrier and pyrolysis product separation section;

[0026] Separate the heat carrier after heat exchange from the pyrolysis products in the heat carrier and pyrolysis product separation section;

[0027] Feed the separated heat carrier into the heat carrier output section from the top of the annulus zone gas distributor through the circulating pyrolysis reaction section, and discharge it from the bottom of the heat carrier output section, and return it to the heat carrier heater;

[0028] Discharge the pyrolysis products from the top of the pyrolysis product conveying section;

[0029] Separate biochar, gaseous and liquid products through a cyclone separator;

[0030] Condense biochar through a biochar condenser;

[0031] Condense gaseous and liquid products through a pyrolysis oil and gas condenser;

[0032] Preliminarily purify and separate gaseous and liquid products through an electrostatic precipitation purification separator;

[0033] Collect the liquid product (semicoke) separated in the electrostatic precipitation purification separator through a tar collector;

[0034] Condense the gaseous product (pyrolysis gas) and liquid products (tar and pyrolysis water) separated in the electrostatic precipitation purification separator through a pyrolysis gas condenser;

[0035] Collect the gaseous product (pyrolysis gas) condensed in the pyrolysis gas condenser through a pyrolysis gas collector;

[0036] Cause the pyrolysis gas to exchange heat with biochar in the biochar condenser, recover the heat of biochar, and use it to preheat the pyrolysis gas;

[0037] The preheated pyrolysis gas (also known as "lifting gas") is transported into the gas distributors in the diversion zone and the annular gap zone, and enters the bottom of the circulating pyrolysis reaction section through the air caps, which is used to lift and regulate the directional circulating movement of biomass and heat carrier in the biomass pyrolysis furnace;

[0038] The liquid products (tar) and liquid products (pyrolysis water) condensed in the pyrolysis gas condenser are separated by an oil-water separator;

[0039] The liquid product (pyrolysis water) separated by the oil-water separator is collected by a pyrolysis water collector;

[0040] The liquid product (tar) separated by the oil-water separator is collected by a tar collector.

[0041] Furthermore, the furnace temperature of the biomass pyrolysis furnace is 300 - 950 °C, and the furnace temperature of the biomass pyrolysis furnace is specifically determined according to the target pyrolysis gas quality or the biomass feed rate. The preferred temperature is 500 - 900 °C. If the purpose is to produce tar, the furnace temperature is set at 300 - 500 °C; if the main purpose is to produce medium calorific value gas, the furnace temperature is set at 700 - 900 °C.

[0042] Furthermore, the furnace pressure of the biomass pyrolysis furnace is 0.1 - 0.4 Mpa; the furnace temperature of the biomass pyrolysis furnace is provided by the heat carrier, and the heat carrier temperature is controlled at 500 - 1000 °C.

[0043] Compared with the prior art, the present invention has the following advantages and effects:

[0044] The biomass pyrolysis reaction technology provided by the present invention forms a diversion zone and an annular gap zone by arranging a draft tube inside the circulating pyrolysis reaction section. By regulating the amount of lifting gas on the gas distributors in the diversion zone and the annular gap zone, the biomass particles and the heat carrier flow directionally in the circulating pyrolysis reaction section and form multiple circulations, effectively improving the flow environment of the biomass particles and the heat carrier, ensuring the uniform mixing and heat exchange of the biomass particles and the heat carrier, and at the same time, the pyrolysis time of the biomass can be effectively controlled according to different target products, thereby effectively controlling the depth and process of the biomass pyrolysis reaction, improving the conversion rate, and increasing the yield of the target product.

[0045] The present invention reduces the superficial gas velocity of the lifting gas by expanding the diameter in the middle of the heat carrier and pyrolysis product separation section, strengthens the classification behavior of the pyrolysis oil and gas products and the heat carrier, enables the pyrolysis oil and gas products to be separated from the heat carrier efficiently and quickly, and effectively ensures that the pyrolysis oil and gas flow into the pyrolysis product conveying section rapidly.

[0046] The present invention rapidly increases the superficial gas velocity of the lifting gas by reducing the diameter of the pyrolysis product conveying section, strengthens the conveying of biochar particles floating on the upper part of the bed layer after the middle-stage classification, and can reduce the residence time of pyrolysis oil and gas, weakening the secondary cracking reaction of pyrolysis oil and gas.

[0047] The structure of the present invention is simply designed, easy to operate, and easy to achieve large-scale production. At the same time, it has strong adaptability to different types of biomass, and can adapt to rice straw, wood chips, and palm. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic structural diagram of the biomass pyrolysis system in the embodiment of the present invention.

[0049] Figure 2 It is a schematic structural diagram of the biomass pyrolysis furnace in the embodiment of the present invention.

[0050] In the figure: biomass pre-processor 2, biomass bin 3, biomass feeder 4, heat carrier heater 5, biomass pyrolysis furnace 6, cyclone separator 7, biochar condenser 8, biochar collector 9, pyrolysis oil and gas condenser 10, electrostatic precipitation purification separator 11, pyrolysis gas condenser 12, oil-water separator 13, tar collector 14, pyrolysis gas collector 15, pyrolysis water collector 16.

[0051] Heat carrier output section 6-1, gas distributor in the diversion area 6-2, gas distributor in the annulus area 6-3, heat carrier feed port 6-4, circulating pyrolysis reaction section 6-5, annulus area 6-6, draft tube 6-7, diversion area 6-8, biomass feed port 6-9, heat carrier and pyrolysis product separation section 6-10, pyrolysis product conveying section 6-11, opening 6-12, air cap 6-13. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The present invention will be further described in detail below with reference to the accompanying drawings and through embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0053] Embodiment

[0054] See Figures 1 to 2 , in this embodiment, a biomass pyrolysis system includes a biomass pyrolysis furnace 6. The biomass pyrolysis furnace 6 sequentially includes a pyrolysis product conveying section 6-11, a heat carrier and pyrolysis product separation section 6-10, a circulating pyrolysis reaction section 6-5, and a heat carrier output section 6-1 from top to bottom. The top of the pyrolysis product conveying section 6-11 is provided with a product outlet.

[0055] The circulating pyrolysis reaction section 6-5 includes a draft tube 6-7, a draft zone 6-8, and an annulus zone 6-6; multiple rows of openings 6-12 are provided on the wall of the draft tube 6-7, and each row of openings 6-12 is arranged at equal intervals. The draft tube 6-7 is coaxially arranged with the circulating pyrolysis reaction section 6-5. The draft zone 6-8 is located inside the draft tube 6-7, and the annulus zone 6-6 is located between the draft tube 6-7 and the circulating pyrolysis reaction section 6-5. A heat carrier outlet is provided at the bottom of the heat carrier output section 6-1.

[0056] The circulating pyrolysis reaction section 6-5 further includes a biomass feed port 6-9, a heat carrier feed port 6-4, a draft zone gas distributor 6-2, and an annulus zone gas distributor 6-3. Both the biomass feed port 6-9 and the heat carrier feed port 6-4 are located on one side of the circulating pyrolysis reaction section 6-5, and the position of the biomass feed port 6-9 is higher than that of the heat carrier feed port 6-4.

[0057] The draft zone gas distributor 6-2 and the annulus zone gas distributor 6-3 are both located at the bottom of the circulating pyrolysis reaction section 6-5. The annulus zone gas distributor 6-3 is located between the draft tube 6-7 and the draft zone gas distributor 6-2.

[0058] The heat carrier output section 6-1 vertically penetrates through the annulus zone gas distributor 6-3 and the draft zone gas distributor 6-2, and the top end of the heat carrier output section 6-1 is flush with the top end of the annulus zone gas distributor 6-3.

[0059] A number of wind caps 6-13 are provided on both the draft zone gas distributor 6-2 and the annulus zone gas distributor 6-3. The wind caps 6-13 can be in the shape of a mushroom, a bell, or an embedded countercurrent column.

[0060] The biomass pyrolysis system further includes a biomass pre-processor 2, a biomass bin 3, a biomass feeder 4, a heat carrier heater 5, a cyclone separator 7, a biochar condenser 8, a biochar collector 9, a pyrolysis oil and gas condenser 10, an electrostatic precipitation and purification separator 11, a tar collector 14, a pyrolysis gas condenser 12, an oil-water separator 13, a pyrolysis water collector 16, and a pyrolysis gas collector 15.

[0061] The biomass outlet of the biomass pre-processor 2 is connected to the biomass inlet of the biomass silo 3. The biomass outlet of the biomass silo 3 is connected to the biomass inlet of the biomass feeder 4. The biomass outlet of the biomass feeder 4 is connected to the biomass feed ports 6-9. The inlet of the heat carrier heater 5 is connected to the outlet of the heat carrier output section 6-1. The outlet of the heat carrier heater 5 is connected to the heat carrier feed port 6-4. The product outlet of the biomass pyrolysis furnace 6 is connected to the product inlet of the cyclone separator 7. The bottom outlet of the cyclone separator 7 is connected to the biochar inlet of the biochar condenser 8. The condensed biochar outlet of the biochar condenser 8 is connected to the inlet of the biochar collector 9. The top outlet of the cyclone separator 7 is connected to the gas-liquid inlet of the pyrolysis oil and gas condenser 10. The gas-liquid outlet of the pyrolysis oil and gas condenser 10 is connected to the gas-liquid inlet of the electrostatic precipitation and purification separator 11. The tar outlet of the electrostatic precipitation and purification separator 11 is connected to the tar inlet of the tar collector 14. The oil-water-containing pyrolysis gas outlet of the electrostatic precipitation and purification separator 11 is connected to the oil-water-containing pyrolysis gas inlet of the pyrolysis gas condenser 12. The oil-water outlet of the pyrolysis gas condenser 12 is connected to the oil-water inlet of the oil-water separator 13. The tar outlet of the oil-water separator 13 is connected to the tar inlet of the tar collector 14. The pyrolysis water outlet of the oil-water separator 13 is connected to the pyrolysis water collector 16. The pyrolysis gas outlet of the pyrolysis gas condenser 12 is connected to the inlet of the pyrolysis gas collector 15.

[0062] The outlet of the pyrolysis gas collector 15 is connected to the inlet of the biochar condenser 8. A heat exchanger is provided in the biochar condenser 8 for heat exchange between the pyrolysis gas and the biochar, that is, the heat of the biochar is recovered to preheat the pyrolysis gas. The pyrolysis gas outlet of the biochar condenser 8 is connected to the gas inlets of the diversion zone gas distributor 6-2 and the annulus zone gas distributor 6-3. The pyrolysis gas (also known as "lifting gas") is transported by the diversion zone gas distributor 6-2 and the annulus zone gas distributor 6-3 to the bottom of the circulating pyrolysis reaction section 6-5 and is used to regulate the directional circulating movement of the biomass and the heat carrier in the biomass pyrolysis furnace 6.

[0063] The biomass pre-processor 2 is used for pre-processing biomass such as cleaning, drying, and pulverizing. The biomass silo 3 is used for storing the pre-processed biomass. The biomass feeder 4 is used for feeding the biomass in the biomass silo 3 into the biomass feed inlet 6-9 of the biomass pyrolysis furnace 6. The heat carrier heater 5 is used for feeding the heat carrier into the heat carrier feed inlet 6-4 of the biomass pyrolysis furnace 6. The gas distributor 6-2 in the diversion zone and the gas distributor 6-3 in the annulus zone are used for transporting the pyrolysis gas (also known as "lifting gas") after heat exchange in the biochar condenser 8 into the biomass pyrolysis furnace 6 from the bottom through the air cap 6-13, for lifting and regulating the directional circulation movement of the biomass and the heat carrier in the biomass pyrolysis furnace 6. The circulating pyrolysis reaction section 6-5 in the biomass pyrolysis furnace 6 is used for the directional cyclic mixing and heat exchange of the biomass and the heat carrier, and for causing the heat-exchanged biomass to undergo pyrolysis reactions to generate biochar, gaseous, liquid products, and dust. The heat carrier and pyrolysis product separation section 6-10 is used for separating the products generated by the pyrolysis reaction and the heat carrier after heat exchange. The separated heat carrier enters the heat carrier output section 6-1 from the top of the annulus gas distributor 6-3 through the circulating pyrolysis reaction section 6-5, and is discharged from the bottom of the heat carrier output section 6-1 and returned to the heat carrier heater 5. The cyclone separator 7 is used for separating the biochar and the gaseous and liquid products from the products generated by pyrolysis. The biochar condenser 8 is provided with a heat exchanger for heat exchange between the pyrolysis gas and the biochar. On the one hand, it condenses the separated biochar and recovers the heat of the biochar, facilitating the subsequent recovery of biochar by the biochar collector 9. On the other hand, it is used for preheating the pyrolysis gas from the pyrolysis gas collector 15 after cooling. The gaseous and liquid products are condensed by the pyrolysis oil and gas condenser 10 and then separated by the electrostatic precipitation purification separator 11 to obtain tar and pyrolysis gas containing oil and water. The separated tar is transported to the tar collector 14 for tar recovery. The pyrolysis gas containing oil and water separated is further transported to the pyrolysis gas condenser 12 for condensation to obtain oil and water and pyrolysis gas. The pyrolysis gas in the pyrolysis gas condenser 12 is transported to the pyrolysis gas collector 15 for pyrolysis gas recovery. The oil and water in the pyrolysis gas condenser 12 are transported to the oil and water separator 13 for separation to further obtain pyrolysis water and tar. The tar in the oil and water separator 13 can be transported to the tar collector 14 for tar recovery. The pyrolysis water in the oil and water separator 13 is transported to the pyrolysis water collector 16 for pyrolysis water recovery.

[0064] By controlling the amount of lifting gas on the gas distributor 6-2 in the diversion zone and the gas distributor 6-3 in the annulus zone, the superficial velocity of the lifting gas in the diversion zone 6-8 is made greater than that in the annulus zone 6-6, ensuring that the pressure in the diversion zone 6-8 at the bottom of the draft tube 6-7 is greater than the pressure in the annulus zone 6-6, so as to realize the upward flow of biomass and heat carrier in the diversion space of the diversion zone 6-8, and then enter the top edge of the diversion zone 6-8 and flow downward along the annulus zone 6-6. After the biomass and the heat carrier circulate 5 to 20 times (i.e., experience 5 to 20 times of mixing), they flow out of the pyrolysis device, and their residence time can be as long as hundreds of seconds, far exceeding the residence time of the traditional upward or downward circulating fluidized bed. This not only enables the complete mixing and heat transfer of biomass and heat carrier, but also allows larger particles of biomass to have sufficient pyrolysis time for full pyrolysis.

[0065] Using the above system to pyrolyze biomass, the process is as follows:

[0066] The normal-temperature biomass, taking rice straw as an example, is sent to the biomass pre-processor 2 for cleaning, drying, and pulverizing into particles with 90% less than 8 mm, and then transported to the biomass silo 3, and sprayed into the biomass feed port 6-9 at the upper part of the central circulating pyrolysis reaction section 6-5 of the biomass pyrolysis furnace 6 through the biomass feeder 4.

[0067] The furnace temperature of the biomass pyrolysis furnace 6 is 300 - 950 °C, and the furnace temperature of the biomass pyrolysis furnace 6 is specifically determined according to the target pyrolysis gas quality or the biomass feed rate. The preferred temperature is 500 - 900 °C. If the purpose is to produce tar, the furnace temperature is set at 300 - 500 °C; if the main purpose is to produce medium-calorific-value gas, the furnace temperature is set at 700 - 900 °C.

[0068] The furnace pressure of the biomass pyrolysis furnace 6 is 0.1 - 0.4 Mpa. The furnace temperature of the biomass pyrolysis furnace 6 is provided by the heat carrier, and the heat carrier temperature is controlled at 500 - 1000 °C. The biomass and the heat carrier in the biomass pyrolysis furnace 6 circulate simultaneously from the diversion zone 6-8 to the annulus zone 6-9 and then back to the diversion zone 6-8 under the action of the lifting gas. The pyrolysis reaction time is adjusted by regulating the amount of lifting gas on the gas distributor 6-2 in the diversion zone and the gas distributor 6-3 in the annulus zone. A large amount of gaseous, liquid, and solid products and a small amount of dust are generated after pyrolysis. The products, dust, and the heat carrier after heat exchange are separated in the heat carrier and pyrolysis product separation section 6-10. The separated heat carrier enters the bottom of the heat carrier output section 6-1 from the top of the annulus void zone gas distributor 6-3 and is discharged, and the separated products and dust are discharged from the top of the pyrolysis product conveying section 6-11.

[0069] The heat carrier discharged from the bottom of the heat carrier output section 6-1 is fed into the heat carrier heater 5. The heat carrier heater 5 is used to heat the heat carrier after heat exchange and feed the heated heat carrier into the heat carrier inlet 6-4 of the circulating pyrolysis reaction section 6-5. The products and dust discharged from the top of the pyrolysis product conveying section 6-11 are fed into the high-temperature cyclone separator 7, where biochar is separated from the oil gas, passes through the biochar condenser 8 and enters the biochar collector 9 as a solid product. The extremely fine dust is discharged with the flue gas.

[0070] A heat exchanger, such as a heat exchange coil, is added to the biochar condenser 8. The pyrolysis gas in the pyrolysis gas collector 15 is passed through the heat exchange coil, and the pyrolysis gas exchanges heat with the biochar. The preheated pyrolysis gas at 200-300 °C (also known as "lifting gas") is transported into the flow guide area gas distributor 6-2 and the annulus area gas distributor 6-3, and enters the bottom of the circulating pyrolysis reaction section 6-5 through the air cap 6-13, which is used to lift and regulate the directional circulating movement of the biomass and the heat carrier in the biomass pyrolysis furnace 6. Specifically, by controlling the amount of the lifting gas on the flow guide area gas distributor 6-2 and the annulus area gas distributor 6-3, a pressure difference is generated between the flow guide area 6-8 and the annulus area 6-6 at the bottom of the draft tube 6-7, which promotes the cyclic flow of coal and the heat carrier between the flow guide area 6-8 and the annulus area 6-6, forming an intersecting mixture to achieve heat exchange. Therefore, under the guiding action of the draft tube 6-7, the biomass and the heat carrier undergo multiple directional cyclic mixing and heat exchange, and the biomass after heat exchange undergoes pyrolysis reaction.

[0071] The pyrolysis oil gas (gaseous and liquid products) at 300-700 °C separated from the high-temperature cyclone separator 7 is fed into the pyrolysis oil gas condenser 10, and the pyrolysis oil gas is condensed to 70-90 °C. The pyrolysis oil gas mixture in the pyrolysis oil gas condenser 10 is separated by the electrostatic precipitation purification separator 11. The tar separated from the bottom of the electrostatic precipitation purification separator 11 is fed into the tar collector 14 as a liquid product.

[0072] The pyrolysis gas containing oil and water separated from the upper part of the electrostatic precipitation purification separator 11 passes through the pyrolysis gas condenser 12, and the condensed pyrolysis gas and the oil and water are fed into the pyrolysis gas collector 15 and the oil-water separator 13 from the upper and lower parts of the pyrolysis gas condenser 12 respectively. The oil and water further enter the oil-water separator 13, the separated tar is fed into the tar collector 14, and the separated pyrolysis water is fed into the pyrolysis water collector 16.

[0073] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0074] Although the present invention has been disclosed above by way of examples, it is not intended to limit the scope of protection of the present invention. Any person skilled in the art, without departing from the concept and scope of the present invention, any changes and modifications made shall fall within the scope of protection of the present invention.

Claims

1. A biomass pyrolysis system, characterized in that: It includes a biomass pyrolysis furnace (6), and the biomass pyrolysis furnace (6) successively includes a pyrolysis product conveying section (6-11), a heat carrier and pyrolysis product separation section (6-10), a circulating pyrolysis reaction section (6-5), and a heat carrier output section (6-1) from top to bottom. A product outlet is provided at the top of the pyrolysis product conveying section (6-11). The circulating pyrolysis reaction section (6-5) includes a draft tube (6-7), a draft zone (6-8), and an annulus zone (6-6); multiple rows of openings (6-12) are provided on the wall of the draft tube (6-7), and each row of the openings (6-12) is arranged at equal intervals. The draft tube (6-7) is coaxially arranged with the circulating pyrolysis reaction section (6-5). The draft zone (6-8) is located inside the draft tube (6-7), and the annulus zone (6-6) is located between the draft tube (6-7) and the circulating pyrolysis reaction section (6-5). A heat carrier outlet is provided at the bottom of the heat carrier output section (6-1). The circulating pyrolysis reaction section (6-5) further includes a biomass feed port (6-9), a heat carrier feed port (6-4), a draft zone gas distributor (6-2), and an annulus zone gas distributor (6-3). Both the biomass feed port (6-9) and the heat carrier feed port (6-4) are located on one side of the circulating pyrolysis reaction section (6-5), and the position of the biomass feed port (6-9) is higher than the position of the heat carrier feed port (6-4). Both the draft zone gas distributor (6-2) and the annulus zone gas distributor (6-3) are located at the bottom of the circulating pyrolysis reaction section (6-5), and the annulus zone gas distributor (6-3) is located between the draft tube (6-7) and the draft zone gas distributor (6-2). The heat carrier output section (6-1) vertically penetrates through the annulus zone gas distributor (6-3) and the draft zone gas distributor (6-2), and the top end of the heat carrier output section (6-1) is flush with the top end of the annulus zone gas distributor (6-3).

2. The biomass pyrolysis system according to claim 1, wherein: A number of air caps (6-13) are provided on both the draft zone gas distributor (6-2) and the annulus zone gas distributor (6-3), and the air caps (6-13) are in the shape of a mushroom, a bell, or an embedded countercurrent column.

3. The biomass pyrolysis system according to claim 2, wherein: The biomass pyrolysis system further includes a biomass pre-processor (2), a biomass bin (3), a biomass feeder (4), a heat carrier heater (5), a cyclone separator (7), a biochar condenser (8), a biochar collector (9), a pyrolysis oil and gas condenser (10), an electrostatic precipitation and purification separator (11), a tar collector (14), a pyrolysis gas condenser (12), an oil-water separator (13), a pyrolysis water collector (16), and a pyrolysis gas collector (15). The biomass outlet of the biomass preprocessor (2) is connected to the biomass inlet of the biomass silo (3). The biomass outlet of the biomass silo (3) is connected to the biomass inlet of the biomass feeder (4). The biomass outlet of the biomass feeder (4) is connected to the biomass feed port (6-9). The inlet of the heat carrier heater (5) is connected to the outlet of the heat carrier output section (6-1). The outlet of the heat carrier heater (5) is connected to the heat carrier feed port (6-4). The product outlet of the biomass pyrolysis furnace (6) is connected to the product inlet of the cyclone separator (7). The bottom outlet of the cyclone separator (7) is connected to the biochar inlet of the biochar condenser (8). The condensed biochar outlet of the biochar condenser (8) is connected to the inlet of the biochar collector (9). The top outlet of the cyclone separator (7) is connected to the gas-liquid inlet of the pyrolysis oil and gas condenser (10). The gas-liquid outlet of the pyrolysis oil and gas condenser (10) is connected to the gas-liquid inlet of the electrostatic precipitation and purification separator (11). The tar outlet of the electrostatic precipitation and purification separator (11) is connected to the tar inlet of the tar collector (14). The oily-water-containing pyrolysis gas outlet of the electrostatic precipitation and purification separator (11) is connected to the oily-water-containing pyrolysis gas inlet of the pyrolysis gas condenser (12). The oil-water outlet of the pyrolysis gas condenser (12) is connected to the oil-water inlet of the oil-water separator (13). The tar outlet of the oil-water separator (13) is connected to the tar inlet of the tar collector (14). The pyrolysis water outlet of the oil-water separator (13) is connected to the pyrolysis water collector (16). The pyrolysis gas outlet of the pyrolysis gas condenser (12) is connected to the inlet of the pyrolysis gas collector (15).

4. The biomass pyrolysis system according to claim 3, wherein: The outlet of the pyrolysis gas collector (15) is connected to the inlet of the biochar condenser (8). A heat exchanger is provided in the biochar condenser (8) for heat exchange between the pyrolysis gas and the biochar. The pyrolysis gas outlet of the biochar condenser (8) is connected to the gas inlets of the diversion zone gas distributor (6-2) and the annulus zone gas distributor (6-3).

5. A pyrolysis method for a biomass pyrolysis system as described in claim 4, characterized in that: The process is as follows: Feed the biomass into the biomass preprocessor (2) from the inlet of the biomass preprocessor (2) for pretreatment; Feed the pretreated biomass from the outlet of the biomass preprocessor (2) into the biomass silo (3); Feed the biomass in the biomass silo (3) from the outlet of the biomass silo (3) into the biomass feeder (4); Feed the biomass from the biomass feeder (4) into the biomass feed port (6-9) of the biomass pyrolysis furnace (6); Feed the heat carrier from the heat carrier heater (5) into the heat carrier feed port (6-4) of the biomass pyrolysis furnace (6); Taking the pyrolysis gas generated by pyrolysis as the lifting gas, after heat exchange in the biochar condenser (8), it is respectively transported from the diversion zone gas distributor (6-2) and the annulus zone gas distributor (6-3) to the biomass pyrolysis furnace (6) through the tuyeres (6-13), so that the biomass and the heat carrier circulate, mix and exchange heat along the diversion zone (6-8) to the annulus zone (6-6) under the action of the lifting gas; After the biomass exchanges heat with the heat carrier, a pyrolysis reaction occurs to generate biochar, gaseous and liquid products; Making the products generated by the pyrolysis reaction and the heat carrier after heat exchange flow from the circulating pyrolysis reaction section (6-5) of the biomass pyrolysis furnace (6) into the heat carrier and pyrolysis product separation section (6-10); Separating the heat carrier after heat exchange from the pyrolysis products in the heat carrier and pyrolysis product separation section (6-10); Transporting the separated heat carrier from the top of the annulus zone gas distributor (6-3) through the circulating pyrolysis reaction section (6-5) into the heat carrier output section (6-1), and discharging it from the bottom of the heat carrier output section (6-1) and returning it to the heat carrier heater (5); Discharging the pyrolysis products from the top of the pyrolysis product conveying section (6-11); Separating biochar, gaseous and liquid products through a cyclone separator (7); Condensing biochar through a biochar condenser (8); Condensing gaseous and liquid products through a pyrolysis oil and gas condenser (10); Preliminarily purifying and separating gaseous and liquid products through an electrostatic precipitation purification separator (11); Collecting the semicoke separated in the electrostatic precipitation purification separator (11) through a tar collector (14); Condensing the pyrolysis gas, tar and pyrolysis water separated in the electrostatic precipitation purification separator (11) through a pyrolysis gas condenser (12); Collecting the pyrolysis gas condensed in the pyrolysis gas condenser (12) through a pyrolysis gas collector (15); Making the pyrolysis gas exchange heat with the biochar in the biochar condenser (8), recovering the heat of the biochar, and using it to preheat the pyrolysis gas; Transporting the preheated pyrolysis gas into the diversion zone gas distributor (6-2) and the annulus zone gas distributor (6-3), and entering the bottom of the circulating pyrolysis reaction section (6-5) through the tuyeres (6-13) to be used for lifting and regulating the directional circulating movement of the biomass and the heat carrier in the biomass pyrolysis furnace (6); Separating the pyrolysis water and tar condensed in the pyrolysis gas condenser (12) through an oil-water separator (13); Collecting the pyrolysis water separated by the oil-water separator (13) through a pyrolysis water collector (16); Collecting the tar separated by the oil-water separator (13) through a tar collector (14).

6. The pyrolysis method of the biomass pyrolysis system according to claim 5, characterized in that: The furnace temperature of the biomass pyrolysis furnace (6) is 300-950 °C, and the furnace temperature of the biomass pyrolysis furnace (6) is specifically determined according to the target pyrolysis gas quality or the biomass feed rate.

7. The pyrolysis method of the biomass pyrolysis system according to claim 5, characterized in that: The furnace pressure of the biomass pyrolysis furnace (6) is 0.1-0.4 MPa; the furnace temperature of the biomass pyrolysis furnace (6) is provided by the heat carrier, and the heat carrier temperature is controlled at 500-1000 °C.

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