Process and device for preparing powdery quality-improved fuel through two-stage biomass baking

Abstract

The invention discloses a two-stage process for preparing powdery quality-improving fuel through biomass baking, which comprises the following steps: S1, a drying procedure: carrying out coarse crushing on biomass to form biomass particles, and screening and drying the biomass particles; s2, a low-temperature baking and powdering process: baking the dried biomass particles, and performing multi-stage fine crushing and grinding on the biomass particles in the baking process to form biomass powder; and S3, cyclic utilization of the baking gas: circularly inputting one part of the baking gas generated in the biomass particle baking process in the step S2 into the step S2 to provide heat for the baking process, and returning the other part of the baking gas to the step 1 to provide heat for the drying process. According to the technology for preparing the powdery upgrading fuel through two-section type biomass baking, powder preparation is completed while baking is conducted through the stirring unit, the baking powder preparation time is greatly saved, and compared with three-section type baking powder preparation, the production efficiency is greatly improved, and the baking efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of biomass milling, and in particular to a two-stage biomass baking process and device for preparing powdered quality-enhanced fuel. Background Art

[0002] Biomass torrefaction technology is a method of heat treating biomass under specific conditions of low temperature, lack of oxygen and low heating rate. This technology can cause cellulose, hemicellulose and lignin in biomass to undergo a certain degree of pyrolysis and carbonization reaction. This process not only effectively removes moisture and light volatiles from biomass, but also produces a certain amount of solid fuel particles and a certain amount of condensed liquid, including bio-oil and water vapor. At the same time, some non-condensable gases such as carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4) are also produced. Through the torrefaction process, the quality of the raw materials is significantly improved, making them have higher application value.

[0003] At the same time, the reaction conditions of biomass low-temperature baking are relatively strict. There must be no oxygen in the system. An inert atmosphere needs to be created and the pressure is normal. The main target product of the process is in a biochar state and pyrolyzed at a relatively slow rate. Most of the water in the biomass is separated, and the same is true for light volatiles. The traditional baking process requires the use of an independent inert gas to ensure the baking process, which requires the consumption of a certain amount of inert gas (such as nitrogen) and the heating process of the inert gas also consumes a certain amount of energy, which increases energy consumption.

[0004] In addition, in the traditional process of biomass baking, the three steps of drying, baking and milling are usually set up independently. There is a lot of heat loss in the process of transporting the baked biomass particles to the milling equipment, which causes the biomass particles to condense into blocks after cooling, which is not conducive to the subsequent milling operation. Therefore, how to optimize this process is an important issue that needs to be solved in the current biomass baking technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a two-stage biomass baking process for preparing powdered upgraded fuel.

[0006] The technical solution adopted by the present invention to solve the above problems is: a two-stage biomass baking process for preparing powdered upgraded fuel, comprising:

[0007] S1: Drying process, coarsely crushing the biomass to form biomass particles, screening and drying the biomass particles;

[0008] S2: Low-temperature baking and powder making process, the dried biomass particles are baked, and in this process the biomass particles are finely crushed and ground into biomass powder in multiple stages.

[0009] S3: Recycling of torrefaction gas. Part of the torrefaction gas generated during the torrefaction of the biomass particles in S2 is recycled and input into S2 to provide heat for the torrefaction process, and part of it is returned to step 1 to provide heat for the drying process.

[0010] Preferably, the S1 comprises:

[0011] S1.1: Preliminary drying: the biomass particles after coarse crushing are screened, and hot flue gas is introduced during the screening process for preliminary drying;

[0012] S1.2: Remove impurities, transport the biomass particles after preliminary drying from high to low and roll them along the transport direction to separate impurities attached to the surface or inside of the biomass;

[0013] S1.3: Secondary drying: hot flue gas is introduced during the transportation of biomass particles in S1.2.

[0014] Preferably, the S2 comprises:

[0015] S2.1: Multi-stage screening, the biomass particles after drying are screened and transported layer by layer from top to bottom;

[0016] S2.2: stirring to remove carbon, stirring the biomass particles in each layer, and striking and peeling off the carbon formed on the surface of the biomass particles during the baking process while stirring;

[0017] S2.3: Grinding and powdering: Grind the biomass particles at the bottom layer, discharge the biomass powder together with the baking gas generated during the baking process, and perform gas-solid separation.

[0018] Preferably, the S3 comprises:

[0019] S3.1: Dehydrating and pressurizing the separated roasting gas, and diverting the treated roasting gas;

[0020] S3.2: 50% to 90% of the baking gas is transported back to the baking furnace for circulation after heat exchange with the hot flue gas in S1 as a high-temperature inert gas, and the remaining baking gas is mixed with combustible gas and air and burned to heat the inert gas as a heat source for the baking process in S2.

[0021] The present invention also provides a device for preparing powdered upgraded fuel by two-stage biomass baking according to any one of the above technical solutions, comprising:

[0022] Pretreatment station: The biomass is coarsely crushed by a crushing and screening device, and then biomass particles with a particle size of less than 20 mm are screened out, and hot flue gas is introduced into the biomass particles through an air supply device for preliminary drying;

[0023] Drying station: The biomass particles are transported upwards by the transfer device, and the hot flue gas is transported from below by the air supply device for secondary drying;

[0024] Baking and milling station: The dried biomass particles are transported to the baking and milling station by the transfer device, and the baking and milling device completes the baking and milling. During the baking process, the biomass particles are finely crushed in multiple stages by the stirring unit, and finally the biomass particles are made into biomass powder;

[0025] Among them, part of the baking gas generated in the baking and flour making station is burned through a heat source device to form high-temperature hot flue gas to generate heat. The high-temperature hot flue gas is heat exchanged with another part of the baking gas and then transported to the pretreatment station and the drying station to provide heat. The part of the baking gas that has heat exchanged with the high-temperature hot flue gas is transported back to the baking and flour making station to provide heat.

[0026] Preferably: the crushing and screening device comprises a crushing unit, a screening unit and a return unit, the crushing unit comprises two groups of crushing wheels, and the two groups of crushing wheels are driven by a first motor and a gear transmission mechanism to realize reverse differential rotation. The screening unit is arranged below the crushing unit, and comprises an obliquely arranged screen plate and a vibration motor for driving the screen plate to vibrate, a first discharge port for discharging biomass particles with a particle size greater than 20 mm is arranged at one end of the screen plate obliquely downward, and a second discharge port for discharging biomass particles with a particle size less than 20 mm is arranged below the screen plate, the return unit transports the biomass particles discharged from the first discharge port upwardly back to the first feed port of the crushing unit, and the crushing and screening device is provided with a first air inlet and a first air outlet communicated with the interior thereof.

[0027] Preferably: the transfer device includes a second belt conveyor for transporting the biomass particles obliquely upward to the baking and powder making device and a porous air distribution plate arranged in parallel below the second belt conveyor, wherein the feed end of the second belt conveyor is located below the second discharge port of the crushing and screening device, and the discharge end is located above the second feed port of the baking and powder making device, and a second air inlet connected to the porous air distribution plate is arranged below the transfer device.

[0028] Preferably: the baking and powder making device comprises an obliquely arranged fixed shell, in which a drum is rotatably arranged and a driving component for driving the drum to rotate is installed, a stirring unit and a plurality of groups of circular screens arranged in parallel are arranged in the drum, and the aperture of the screens decreases step by step from top to bottom, the stirring unit comprises a stirring shaft and a fourth motor for driving the stirring unit to rotate, the stirring shaft is arranged on the central axis of the drum, passes through the screens in sequence, and stirring blades and a beating ball connected by a metal chain are arranged in a stirring chamber between two adjacent groups of screens, the beating ball is adapted to the contour of the stirring blades, a third discharge port communicated with the discharge end of the drum is arranged below the fixed shell, and the fixed shell is provided with a third air inlet communicated with the interior thereof.

[0029] Preferably: the heat source device includes a gas-solid separator for separating the biomass powder and baking gas discharged from the powder making unit and a combustion device for burning baking gas and oxygen to form high-temperature flue gas, the heat source device is respectively connected to the crushing and screening device, the transfer device and the baking and powder making device through pipelines, wherein the input end of the gas-solid separator is connected to the third discharge port of the baking and powder making device, the baking gas output end of the gas-solid separator is diverted after dehydration and pressurization, the baking gas is connected to the input end of the combustion device through a branch, the baking gas is connected to the third air inlet of the baking and powder making device after heat exchange with the high-temperature hot flue gas generated at the output end of the combustion device through another branch through a heat exchanger, and then the heat is connected to the third air inlet of the baking and powder making device, and the gas-solid separator is also provided with a first regulating valve for adjusting the baking gas delivery ratio of the two branches.

[0030] Preferably: the air supply device includes a hot flue gas fan, the hot flue gas at the output end of the combustion device after heat exchange and cooling is connected to the input end of the hot air fan through a pipeline, the output end of the hot air fan is respectively connected to the first air inlet of the crushing and screening device and the second air inlet of the transfer device, and a second regulating valve is provided for adjusting the hot flue gas delivery ratio of the two branches, and the hot flue gas is finally discharged through the first exhaust port of the crushing and screening device.

[0031] Compared with the prior art, the present invention has the following advantages and effects:

[0032] (1) The present invention adopts a two-stage biomass baking process to prepare powdered upgraded fuel. The mixing unit completes the powdering during baking, which greatly saves the time of baking and powdering. Compared with the three-stage baking and powdering, the production efficiency is greatly improved.

[0033] (2) The present invention converts biomass raw materials into powdered upgraded fuel, which reduces the moisture content of biomass while also increasing the calorific value and energy density of biomass products, thereby improving the fuel performance of biomass and facilitating long-term storage and long-distance transportation, thereby realizing resource utilization of biomass and facilitating large-scale utilization of biomass.

[0034] (3) The present invention recycles the baking gas, which not only plays a role in isolating oxygen during the low-temperature baking process, but also can use its heat to provide heat for the baking of biomass, thereby realizing multi-level utilization of heat, improving the utilization rate of heat, thereby ensuring baking efficiency and reducing baking energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the process of preparing powdered upgraded fuel by a two-stage biomass baking process according to Example 1 of the present invention.

[0036] Figure 2 It is a schematic flow chart of a two-stage biomass baking process for preparing powdered upgraded fuel according to Example 1 of the present invention.

[0037] Figure 3 It is a three-dimensional schematic diagram of a two-stage biomass baking device for preparing powdered upgraded fuel according to Example 2 of the present invention.

[0038] Figure 4 It is a side schematic diagram of a two-stage biomass baking device for preparing powdered upgraded fuel according to Example 2 of the present invention.

[0039] Figure 5 The present invention Figure 4 A partial structural sectional view of the crushing and screening device shown in.

[0040] Figure 6 The present invention Figure 4 A partial structural sectional view of the crushing and screening device shown in.

[0041] Figure 7 The present invention Figure 4 A partial structural sectional view of the transfer device shown in .

[0042] Figure 8 The present invention Figure 7 The structural schematic diagram of the driving components is shown in .

[0043] Fig. 9 The present invention Figure 4 Schematic diagram of the internal structure of the baking and flour making device shown in.

[0044] Figure numbers: pretreatment station 11, drying station 12, baking and powder making station 13, crushing and screening device 14, air supply device 15, transfer device 16, baking and powder making device 17, stirring unit 18, heat source device 19, screw conveyor 20, crushing unit 21, screening unit 22, crushing wheel 23, first motor 24, sieve plate 31, vibration motor 32, first discharge port 33, second discharge port 34, first feed port 35, first air inlet 36, first exhaust port 37, gas-solid separator 38, VOCs adsorber 39, heat exchanger 40, return unit 41, first storage bin 42, first belt conveyor 43, first baffle 44, sealed shell 45, first accommodating chamber 46, first closing plate 51, linear drive mechanism 52, first drive shaft 53, second motor 54, transfer device 55, second belt conveyor 56, porous air distribution plate 57, second storage bin 58, second air inlet 59, second baffle 61, second accommodating chamber 62, connecting port 63, second closing plate 64, third motor 65, fixed shell 71, roller 72, drive component 73, screen 74, stirring shaft 81, fourth motor 82, stirring chamber 83, stirring blade 84, metal chain 85, striking ball 86, third discharge port 87, third air inlet 88, fifth motor 91, second drive shaft 92, roller 93, heat source device 94, combustion device 95, first regulating valve 96, hot air blower 97, second regulating valve 98. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.

[0046] Embodiment 1:

[0047] See also Figure 1 and Figure 2 The present embodiment provides a two-stage biomass baking process for preparing powdered upgraded fuel, comprising the following steps:

[0048] S1: Drying process, the biomass with a moisture content of 17% is coarsely crushed to form biomass particles, the biomass particles are screened and dried, the drying temperature is 110-120°C, and the moisture content of the biomass after drying is 1.9%;

[0049] S2: Low-temperature baking and powder making process, the dried biomass particles are baked at a temperature of 160-180°C for 20-30 minutes, and in this process the biomass particles are finely crushed and ground in multiple stages to form biomass powder.

[0050] S3: Recycling of torrefaction gas. Part of the torrefaction gas generated during the torrefaction of the biomass particles in S2 is recycled and input into S2 to provide heat for the torrefaction process, and part of it is returned to step 1 to provide heat for the drying process.

[0051] The S1 includes:

[0052] S1.1: Preliminary drying: the biomass particles after coarse crushing are screened, and hot flue gas is introduced during the screening process for preliminary drying;

[0053] S1.2: Remove impurities, transport the biomass particles after preliminary drying from high to low and roll them along the transport direction to separate impurities attached to the surface or inside of the biomass;

[0054] S1.3: Secondary drying: hot flue gas is introduced during the transportation of biomass particles in S1.2.

[0055] The S2 includes:

[0056] S2.1: Multi-stage screening, the biomass particles after drying are screened and transported layer by layer from top to bottom;

[0057] S2.2: stirring to remove carbon, stirring the biomass particles in each layer, and striking and peeling off the carbon formed on the surface of the biomass particles during the baking process while stirring;

[0058] S2.3: Grinding and powdering: Grind the biomass particles at the bottom layer, discharge the biomass powder together with the baking gas generated during the baking process, and perform gas-solid separation.

[0059] The S3 includes:

[0060] S3.1: Dehydrating and pressurizing the separated roasting gas, and diverting the treated roasting gas;

[0061] S3.2: 50% to 90% of the baking gas is heat exchanged with the hot flue gas in S1 and then transported back to the baking furnace for circulation as high-temperature inert gas, and the remaining baking gas is mixed with combustible gas and air for combustion to heat the inert gas as the heat source for the baking process in S2. The combustible gas is the analytical gas and / or relaxation gas of the subsequent process.

[0062] Embodiment 2:

[0063] See also Figure 3 and Figure 4, this embodiment is a device for preparing powdered quality-improving fuel by two-stage biomass baking process described in Example 1, including a pretreatment station 11, a drying station 12 and a baking and powdering station 13. The pretreatment station 11 uses a crushing and screening device 14 to coarsely crush the biomass and then screen out biomass particles with a particle size less than 20 mm, and introduces hot flue gas into the biomass particles through an air supply device 15 for preliminary drying. The drying station 12 uses a transfer device 55 to transport the biomass particles obliquely upward, and uses the air supply device 15 to transport the hot flue gas from below for secondary drying. The baking and powdering station 13 transports the dried biomass particles to the baking and powdering station 13 through the transfer device 55, and the baking and powdering device 17 completes the baking and powdering. During the baking process, the biomass particles are finely crushed in multiple stages through the stirring unit 18, and finally the biomass particles are made into biomass powder. Among them, part of the baking gas generated in the baking and powder making station 13 is burned through the heat source device 19 to form high-temperature hot flue gas to generate heat. The high-temperature hot flue gas is heat exchanged with another part of the baking gas and then transported to the pretreatment station 11 and the drying station 12 to provide heat. The part of the baking gas that has heat exchanged with the high-temperature hot flue gas is transported back to the baking and powder making station 13 to provide heat.

[0064] When preparing powdered upgraded fuel, the biomass raw materials (including agricultural wastes such as straw and stalks and forestry wastes such as bamboo and wood) are crushed into biomass particles with a particle size of less than 20 mm by the crushing and screening device 14 (biomass particles with a particle size greater than 20 mm are crushed again by the return unit 41), and are heated by hot flue gas for preliminary drying to reduce the stickiness of the biomass particles during transportation. Then, they are transported by the transfer device 55, and the hot flue gas is used to maintain the heating state during transportation for secondary drying, thereby removing most of the moisture contained in the biomass particles, and then The biomass particles are transported to the baking and powder making device 17 through the transport device 55, so that the stirring unit 18 stirs and grinds the transported biomass particles, and the biomass particles are changed from granular to powdery, and baked at the same time. The baked biomass powder and the baking gas generated during the baking process are discharged together through the screw conveyor 20, and the discharged baking gas is returned to the baking and powder making device 17 through the air supply device 15 to be used as an inert gas, and provide heat for the baking and powder making of the biomass particles. The discharged biomass powder can be collected by the vacuum amplifier and then sealed and stored for subsequent processing. In the baking process, the present invention makes full use of the baking gas generated in the baking process, uses the baking gas as the inert gas of the baking process, and at the same time, heat is exchanged with the baking gas by using the hot flue gas after the baking gas is burned to provide heat for baking, improve the baking efficiency, and realize the multi-stage utilization of heat. The powder making is completed by the stirring unit 18 while baking, which greatly saves the time of baking and powder making, and greatly improves the production efficiency compared with the three-stage baking and powder making.

[0065] See also Figure 5 and Figure 6 The crushing and screening device 14 includes a crushing unit 21, a screening unit 22 and a return unit 41. The crushing unit 21 includes two groups of crushing wheels 23, which are driven by a first motor 24 and a gear transmission mechanism to achieve reverse differential rotation. The screening unit 22 is arranged below the crushing unit 21, and includes an obliquely arranged screen plate 31 and a vibration motor 32 for driving the screen plate 31 to vibrate. A first discharge port 33 for discharging biomass particles with a particle size greater than 20 mm is arranged at one end of the screen plate 31 obliquely downward, and a second discharge port 34 for discharging biomass particles with a particle size less than 20 mm is arranged below the screen plate 31. The return unit 41 transports the biomass particles discharged from the first discharge port 33 upward to the first feed port 35 of the crushing unit 21. The crushing and screening device 14 is provided with a first air inlet 36 and a first air outlet 37 communicated with the interior thereof.

[0066] Specifically, the gear transmission mechanism includes two groups of gears meshing with each other and having different numbers of teeth. One end of the small gear with fewer teeth is connected to the first motor 24, and the other end is connected to a group of crushing wheels 23. The large gear with more teeth is connected to the other group of crushing wheels 23. The first motor 24 drives the two groups of crushing wheels 23 to rotate in opposite directions at different speeds. The crushing wheels 23 are densely covered with teeth for crushing biomass raw materials in the circumferential direction. The two groups of crushing wheels 23 are crushed into biomass particles by squeezing between teeth during rotation. When drying (the material drying temperature is set at 110-120°C), hot flue gas enters from the first air inlet 36 through the air supply device 15, preliminarily dries the biomass particles, and is finally discharged from the first exhaust port 37.

[0067] In order to reduce the pollution of gas emissions to the environment, the hot flue gas discharged from the first exhaust port 37 can pass through the gas-solid separator 38 to separate the dust entrained in the hot flue gas, and then pass through the VOCs adsorber 39 to remove the trace organic matter generated in the drying process.

[0068] The return unit 41 includes a first storage bin 42 and a first belt conveyor 43 for obliquely transporting biomass particles back to the crushing unit 21. The first storage bin 42 is located below the first discharge port 33 and its bottom is connected to the feed end of the first belt conveyor 43. The discharge end of the first belt conveyor 43 is located above the first feed port 35 of the crushing unit 21. The belt of the first belt conveyor 43 is provided with a plurality of first baffles 44 arranged at equal intervals, and the first baffles 44 are arranged obliquely with the conveyor belt. A sealing shell 45 is provided on the outside of the conveyor 43, which is in close contact with both sides of the belt and the outer edge of the first baffle 44, so that a first accommodating chamber 46 is formed between two adjacent groups of first baffles 44. The first storage bin 42 uses the first belt conveyor 43 to transport the biomass particles with a particle size greater than 20 mm back to the crushing unit 21 for further crushing until the particle size of the biomass particles is less than 20 mm and can be discharged from the second discharge port 34 through the sieve plate 31, wherein the sieve plate 31 and the vibration motor 32 are driven by belt transmission to achieve vibration.

[0069] When the crushing and screening device 14 is just started, its internal temperature is relatively low, and part of the previously generated water vapor is easily accumulated at the bottom of the first storage bin 42 after condensation. In order to prevent condensed water from penetrating into the feed end of the first belt conveyor 43, a first closing plate 51 is provided at the feed end of the first belt conveyor 43 and a linear drive mechanism 52 is installed to drive it to slide. When condensed water accumulates in the first storage bin 42, the first closing plate 51 can close the feed end through the linear drive mechanism 52 to ensure that the condensed water does not penetrate into the conveyor belt and the first baffle 44, thereby preventing the biomass particles from sticking to the conveyor belt during transportation. In order to deal with the condensed water, the air supply device 15 can be started in advance to input hot flue gas. The hot flue gas is heated by contact with the condensed water, causing the condensed water to evaporate again into water vapor. The evaporated water vapor will be discharged through the second discharge port 34 of the first storage bin 42 together with the hot flue gas.

[0070] In this embodiment, the linear drive mechanism 52 includes a first drive shaft 53, which is rotatably arranged on the first storage bin 42. A second motor 54 is installed on the first storage bin 42 to drive the first drive shaft 53 to rotate relative to the storage bin. The second motor 54 and the first drive shaft 53 are connected by a gear transmission mechanism, and the first closing plate 51 is threadedly mounted on the first drive shaft 53.

[0071] See also Figure 7The transfer device 55 includes a second belt conveyor 56 for transporting the biomass particles obliquely upward to the baking and powder making device 17 and a porous air distribution plate 57 arranged in parallel below the second belt conveyor 56, wherein the feeding end of the second belt conveyor 56 is located below the second discharge port 34 of the crushing and screening device 14, and the discharge end is located above the second storage bin 58 of the baking and powder making device 17. A second air inlet 59 connected to the porous air distribution plate 57 is arranged below the transfer device 55. Through the arrangement of the porous air distribution plate 57, a more uniform transportation of hot flue gas for drying is achieved to improve the drying effect.

[0072] Specifically, the belt of the second belt conveyor 56 is provided with a plurality of second baffles 61 arranged at equal intervals, and the second baffles 61 are arranged perpendicular to the belt, so that a second accommodating chamber 62 for accommodating biomass particles is formed between the second baffles 61 and the belt, and the second storage bin 58 is provided with a connecting port 63 which is connected to the baking and powder making device 17, and a second closing plate 64 is rotatably provided at the connecting port 63 and a third motor 65 for driving the second closing plate 64 to rotate is installed, and the second closing plate 64 is driven by the third motor 65 to realize the opening or closing of the connecting port 63.

[0073] The temperature setting range is 160 to 180 degrees Celsius, which is higher than the 110 to 120 degrees Celsius in the previous drying stage. In order to ensure that the chamber of the baking and milling device 17 maintains a high temperature and an inert gas environment, the second closing plate 64 remains closed, thereby isolating the drying station 12 from the baking and milling station 13. This is to prevent the hot flue gas with a lower temperature from invading the baking and milling device 17 during the drying process, destroying the inert atmosphere and thus affecting the baking quality. The biomass particles discharged through the second discharge port 34 are then transported to the second storage bin 58 by the second belt conveyor 56. When the biomass particles in the second storage bin 58 accumulate to a certain amount, the third motor 65 will drive the second closing plate 64 to switch from a closed state to an open state, so that the biomass particles in the second storage bin 58 can directly enter the chamber of the baking and milling device 17 through the connecting port 63, effectively reducing the possibility of chamber contamination or temperature fluctuations.

[0074] See also Fig. 9The baking powder making device 17 comprises a fixed shell 71 which is arranged obliquely, a roller 72 is rotatably arranged in the fixed shell 71 and a driving component 73 for driving the roller 72 to rotate is installed, a stirring unit 18 and a plurality of groups of circular screens 74 arranged in parallel are arranged in the drum 72, and the aperture of the screens 74 decreases step by step from top to bottom, the stirring unit 18 comprises a stirring shaft 81 and a fourth motor 82 for driving the stirring unit 18 to rotate, the stirring shaft 81 is arranged on the central axis of the drum 72, and passes through the screens 74 in sequence, and a stirring blade 84 and a striking ball 86 connected by a metal chain 85 are arranged in a stirring chamber 83 between two adjacent groups of screens 74, and the striking ball 86 is adapted to the contour of the stirring blade 84, a third discharge port 87 which is connected to the discharge end of the drum 72 is arranged below the fixed shell 71, and a third air inlet 88 which is connected to the interior of the fixed shell 71 is arranged. Figure 8 Specifically, the driving component 73 includes a fifth motor 91, and the two ends of the fifth motor 91 are connected to two sets of synchronously rotating second driving shafts 92 through a gear transmission mechanism. A set of rollers 93 are installed at both ends of each set of second driving shafts 92, and the drum 72 rotates through the contact and friction between its outer shell and the rollers 93.

[0075] During the baking process, the circulating high-temperature baking gas of 220-230°C enters the baking and powder making device 17 from the third air inlet 88, heats the biomass therein to 160-180°C for baking, and drives the stirring shaft 81 to rotate through the fourth motor 82, so that the stirring shaft 81 drives the stirring blade and the hitting ball 86 to rotate together, thereby stirring the biomass particles to ensure the smoothness of the flow of baking gas between the biomass particles, reducing the risk of biomass particle accumulation affecting the baking effect and the risk of biomass particles blocking the screen 74 and affecting the biomass particles from obliquely entering each stirring chamber 83 in sequence. The hitting ball 86 can rotate together with the stirring shaft 81 through the metal chain 85, thereby hitting the biomass particles in the stirring chamber 83, thereby achieving crushing and grinding of the biomass particles, thereby ensuring carbon stripping during the baking process of the biomass particles, forming biomass powder and discharging it through the third discharge port 87, and the feed end of the screw conveyor 20 is connected to the third discharge port 87. In particular, the height of the striking ball 86, that is, the grinding radius of the striking ball 86, can be adjusted by adjusting the rotation speed of the stirring shaft 81 driven by the fourth motor 82, so as to increase the crushing and grinding range of the striking ball 86. In addition, the fifth motor 91 drives the roller 72 to rotate in the opposite direction relative to the stirring shaft 81, so that the roller 72 is fully in contact with the baking gas and is heated evenly, thereby avoiding the influence of local high temperature on the baking effect. The biomass particles at the bottom of the stirring chamber 83 are lifted up by the rotation of the roller 72, effectively reducing the possibility of the accumulation of biomass particles at the edge of the screen 74 at the bottom of the stirring chamber 83 and causing the screen 74 to be blocked. This embodiment performs powder making while baking, realizes the simultaneous progress of baking and powder making, and greatly improves the efficiency of preparing powdered quality-enhanced fuel.

[0076] The heat source device 19 includes a gas-solid separator 38 for separating the biomass powder and baking gas discharged from the powder making unit, and a combustion device 95 for burning baking gas and oxygen to form high-temperature flue gas. The heat source device 19 is respectively connected to the crushing and screening device 14, the transfer device 55 and the baking and powder making device 17 through pipelines, wherein the input end of the gas-solid separator 38 is connected to the third discharge port 87 of the baking and powder making device 17, and the baking gas output end of the gas-solid separator 38 is dehydrated and pressurized and then diverted. The baking gas is connected to the input end of the combustion device 95 through a branch, and the baking gas is connected to the high-temperature hot flue gas generated at the output end of the combustion device 95 through another branch. After heat exchange is achieved through a heat exchanger 40, it is connected to the third air inlet 88 of the baking and powder making device 17. The gas-solid separator 38 is also provided with a first regulating valve 96 for adjusting the baking gas delivery ratio of the two branches.

[0077] In this embodiment, by adjusting the first regulating valve 96, 50% to 90% of the baking gas can be transported through the pipeline to return to the baking and powder making device 17 for circulation after heat exchange with the high-temperature flue gas generated by the combustion device 95 through the heat exchanger 40, and the remaining baking gas is sent to the combustion device 95 through another pipeline, and is mixed with air and burned by the combustion device 95 as a heat source. The generated high-temperature flue gas indirectly heats the circulating baking gas through the heat exchanger 40 to provide heat for baking.

[0078] The air supply device 15 includes a hot air blower 97. The hot flue gas at the output end of the combustion device 95 after heat exchange and cooling is connected to the input end of the hot air blower 97 through a pipeline. The output end of the hot air blower 97 is respectively connected to the first air inlet 36 of the crushing and screening device 14 and the second air inlet 59 of the transfer device 55, and is provided with a second regulating valve 98 for adjusting the hot flue gas transmission ratio of the two branches. The hot flue gas is finally discharged through the first exhaust port 37 of the crushing and screening device 14. Among them, the first air inlet 36 is set at the bottom of the crushing and screening device 14, the first exhaust port 37 is set at the top of the crushing and screening device 14, and the second air inlet 59 is set at the bottom of the transfer device 55.

[0079] In the initial state of the equipment, the temperature of the crushing and screening device 14 is relatively low, and the second regulating valve 98 is used to increase the intake rate of the hot flue gas entering the first air inlet 36, so that the crushing and screening device 14 is preheated quickly and the discharge of condensed water is accelerated; when the crushing and screening device 14 is started, the second regulating valve 98 is used to reduce the intake rate of the hot flue gas entering the first air inlet 36 to avoid the biomass particles being blown away. At this time, the intake rate of the hot flue gas entering the first air inlet 36 is increased, which is helpful for the secondary drying of the biomass particles.

[0080] The above contents described in this specification are merely examples of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, as long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A two-stage biomass baking process for preparing powdered fuel, characterized in that: The steps include: S1: Drying process, coarsely crushing the biomass to form biomass particles, screening and drying the biomass particles; S2: low-temperature baking and milling process, baking the dried biomass particles, and in this process, performing multi-level fine crushing and grinding on the biomass particles to form biomass powder; S3: Recycling of torrefaction gas. Part of the torrefaction gas generated during the torrefaction of the biomass particles in S2 is recycled and input into S2 to provide heat for the torrefaction process, and part of it is returned to step 1 to provide heat for the drying process.

2. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 1, characterized in that: The S1 includes: S1.1: Preliminary drying: the biomass particles after coarse crushing are screened, and hot flue gas is introduced during the screening process for preliminary drying; S1.2: Remove impurities, transport the biomass particles after preliminary drying from high to low and roll them along the transport direction to separate impurities attached to the surface or inside of the biomass; S1.3: Secondary drying: hot flue gas is introduced during the transportation of biomass particles in S1.

2.

3. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 1, characterized in that: The S2 includes: S2.1: Multi-stage screening, the biomass particles after drying are screened and transported layer by layer from top to bottom; S2.2: stirring to remove carbon, stirring the biomass particles in each layer, and striking and peeling off the carbon formed on the surface of the biomass particles during the baking process while stirring; S2.3: Grinding and powdering: Grind the biomass particles at the bottom layer, discharge the biomass powder together with the baking gas generated during the baking process, and perform gas-solid separation.

4. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 1, characterized in that: The S3 includes: S3.1: Dehydrating and pressurizing the separated roasting gas, and diverting the treated roasting gas; S3.2: 50%-90% of the baking gas is transported back to the baking furnace for circulation after heat exchange with the hot flue gas in S1 as high-temperature inert gas, and the remaining baking gas is mixed with combustible gas and air for combustion to heat the inert gas as the heat source for the baking process in S2.

5. A device for preparing powdered upgraded fuel by two-stage biomass baking process according to any one of claims 1 to 4, characterized in that: include: Pretreatment station: The biomass is coarsely crushed by a crushing and screening device, and then biomass particles with a particle size of less than 20 mm are screened out, and hot flue gas is introduced into the biomass particles through an air supply device for preliminary drying; Drying station: The biomass particles are transported upwards by the transfer device, and the hot flue gas is transported from below by the air supply device for secondary drying; Baking and milling station: The dried biomass particles are transported to the baking and milling station by the transfer device, and the baking and milling device completes the baking and milling. During the baking process, the biomass particles are finely crushed in multiple stages by the stirring unit, and finally the biomass particles are made into biomass powder; Among them, part of the baking gas generated in the baking and flour making station is burned through a heat source device to form high-temperature hot flue gas to generate heat. The high-temperature hot flue gas is heat exchanged with another part of the baking gas and then transported to the pretreatment station and the drying station to provide heat. The part of the baking gas that has heat exchanged with the high-temperature hot flue gas is transported back to the baking and flour making station to provide heat.

6. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 5, characterized in that: The crushing and screening device includes a crushing unit, a screening unit and a return unit. The crushing unit includes two groups of crushing wheels, which are driven by a first motor and a gear transmission mechanism to realize reverse differential rotation. The screening unit is arranged below the crushing unit, and includes an obliquely arranged screen plate and a vibration motor for driving the screen plate to vibrate. A first discharge port for discharging biomass particles with a particle size greater than 20 mm is arranged at one end of the screen plate obliquely downward, and a second discharge port for discharging biomass particles with a particle size less than 20 mm is arranged below the screen plate. The return unit transports the biomass particles discharged from the first discharge port upwardly back to the first feed port of the crushing unit. The crushing and screening device is provided with a first air inlet and a first air outlet communicated with the interior thereof.

7. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 5, characterized in that: The transfer device includes a second belt conveyor for transporting biomass particles obliquely upward to the baking and powder making device and a porous air distribution plate arranged in parallel below the second belt conveyor, wherein the feed end of the second belt conveyor is located below the second discharge port of the crushing and screening device, and the discharge end is located above the second feed port of the baking and powder making device, and a second air inlet connected to the porous air distribution plate is arranged below the transfer device.

8. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 5, characterized in that: The baking and powder making device includes an obliquely arranged fixed shell, in which a roller is rotatably arranged and a driving component for driving the roller to rotate is installed, a stirring unit and a plurality of groups of circular screens arranged in parallel are arranged in the drum, and the aperture of the screens decreases step by step from top to bottom, the stirring unit includes a stirring shaft and a fourth motor for driving the stirring unit to rotate, the stirring shaft is arranged on the central axis of the drum, passes through the screens in sequence, and stirring blades and a beating ball connected by a metal chain are arranged in a stirring chamber between two adjacent groups of screens, the beating ball is adapted to the contour of the stirring blades, a third discharge port connected to the discharge end of the drum is arranged below the fixed shell, and the fixed shell is provided with a third air inlet connected to its interior.

9. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 5, characterized in that: The heat source device includes a gas-solid separator for separating the biomass powder and baking gas discharged from the powder making unit, and a combustion device for burning baking gas and oxygen to form high-temperature flue gas. The heat source device is respectively connected to the crushing and screening device, the transfer device and the baking and powder making device through pipelines, wherein the input end of the gas-solid separator is connected to the third discharge port of the baking and powder making device, the baking gas output end of the gas-solid separator is dehydrated and pressurized and then diverted, the baking gas is connected to the input end of the combustion device through a branch, the baking gas is connected to the third air inlet of the baking and powder making device after heat exchange with the high-temperature hot flue gas generated at the output end of the combustion device through another branch through a heat exchanger, and then connected to the third air inlet of the baking and powder making device, and the gas-solid separator is also provided with a first regulating valve for adjusting the baking gas delivery ratio of the two branches.

10. A two-stage biomass baking process for preparing powdered upgraded fuel according to claim 9, characterized in that: The air supply device includes a hot flue gas fan. The hot flue gas at the output end of the combustion device after heat exchange and cooling is connected to the input end of the hot air fan through a pipeline. The output end of the hot air fan is respectively connected to the first air inlet of the crushing and screening device and the second air inlet of the transfer device, and a second regulating valve is provided for adjusting the hot flue gas delivery ratio of the two branches. The hot flue gas is finally discharged through the first exhaust port of the crushing and screening device.

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