Device and method for preparing white carbon black by biomass carbon thermal conversion

Abstract

The present application relates to the field of biomass energy utilization, and particularly relates to a device for preparing white carbon black by biomass carbon thermal conversion, which comprises a driving motor, a sealed joint, a furnace body, a heat preservation sleeve and a sealed end. The device adopts a spiral combustion device to control the residence time of the material in the furnace, and the combustion rate is controlled by the proportion of the oxygen carrier and the rice hull charcoal, and the temperature is controlled by the external molten salt heat preservation system, so that the precise temperature control of the combustion process is realized, and the rice hull charcoal is completely combusted without damaging the amorphous silicon dioxide structure. In addition, the present application also provides a method for preparing white carbon black by biomass carbon thermal conversion, which mainly controls the residence time of the material in the furnace by controlling the rotating speed of the driving motor, controls the combustion rate by controlling the proportion of the oxygen carrier and the rice hull charcoal, and controls the temperature by the molten salt heat preservation system, so that the efficient preparation of the white carbon black from the rice hull is realized.

Description

Technical Field

[0001] This invention relates to the field of biomass energy utilization, specifically to an apparatus and method for preparing precipitated silica from biomass carbothermal conversion. Background Technology

[0002] my country is the world's largest rice producer, with an annual output exceeding 200 million tons. Rice husks, a processing byproduct, account for approximately 20% of the rice's weight, meaning about 40 million tons of rice husks need to be processed annually. The simplest way to process rice husks is through direct combustion to provide energy, but unfortunately, this produces a large amount of ash that is difficult to utilize effectively and easily causes secondary pollution. Research shows that rice husks contain 15-20 wt% amorphous silica (also known as white carbon black). If this amorphous silica can be extracted and processed into white carbon black without destroying its structure, it can be transformed from waste into a valuable resource, significantly increasing the utilization value of rice husks.

[0003] Therefore, many scholars have conducted research on producing precipitated silica from rice husks. Currently, the main methods developed include precipitation and combustion. The precipitation method involves dissolving the silicon components of rice husks, rice husk charcoal, or rice husk ash in an alkali solution to create a water glass solution. Then, the pH of the solution is adjusted using acid to induce precipitation. Finally, the solution is filtered and dried to obtain the precipitated silica product. This method is not significantly different from traditional precipitation-based precipitated silica, except for the silicon source used. Therefore, the resulting precipitated silica product is not significantly different from that of traditional precipitation-based precipitated silica and is difficult to use directly as a high-end precipitated silica product. The combustion method involves removing impurities from rice husks or rice husk charcoal, and then removing organic components through combustion to directly obtain the precipitated silica product. Compared to the precipitation method, this method does not damage the natural amorphous silica structure of rice husks, resulting in higher quality precipitated silica. However, because high temperatures can damage the amorphous silica structure and low temperatures can lead to incomplete combustion, this method requires high-precision process parameters, and currently, there is a lack of corresponding temperature-controlled combustion devices.

[0004] In contrast, rice husks have a high volatile content, resulting in a fast and violent combustion rate, making it difficult to control low combustion temperatures. Rice husk char, on the other hand, has a low volatile content, a slow combustion reaction rate, and is easier to control in terms of temperature. However, traditional fixed-bed or grate-fired charcoal combustion devices struggle to provide stable and uniform air distribution, leading to uneven combustion temperatures and making them unsuitable for direct use in the production of precipitated silica from rice husk charcoal. In recent years, researchers have proposed chemical looping combustion, which, compared to air-supply, uses a solid oxygen carrier for oxygen supply, resulting in more stable combustion reaction rate control and more uniform combustion temperature distribution. This makes it highly suitable for temperature-controlled combustion of rice husk charcoal to produce high-quality precipitated silica. However, corresponding chemical looping combustion devices and methods are currently lacking. Therefore, there is an urgent need to develop efficient devices and methods for the biomass carbothermal conversion to produce precipitated silica, enabling the efficient production of rice husk-derived precipitated silica. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an apparatus and method for preparing precipitated silica by biomass carbothermal conversion with precise temperature control and high efficiency.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the apparatus for preparing silica from biomass carbon thermal conversion according to the present invention includes: a drive motor, a sealing joint, a furnace body, an insulation sleeve, and a sealing end.

[0009] The furnace body includes a cylindrical furnace wall and a spiral shaft with spiral blades rotatably disposed inside the furnace wall; an oxygen carrier inlet and a rice husk charcoal inlet are sequentially opened on the upper part of the furnace wall near the first end, and a solid outlet is opened on the lower part of the furnace wall near the second end; the furnace wall protrudes upward from the position near the rice husk charcoal inlet to the upper part of the second end to form a flue gas channel with the spiral blades, and multiple flue gas outlets are opened on the flue gas channel;

[0010] The heat insulation sleeve is installed outside the furnace wall, and a spiral guide vane is installed in the annular space between the heat insulation sleeve and the furnace wall. A molten salt inlet is formed at the second end of the annular space, and a molten salt outlet is formed at the first end of the annular space.

[0011] The sealing joint is provided at the first end of the furnace wall and the sealing end is provided at the second end of the furnace wall. The sealing joint and the sealing end together provide rotational support for the spiral shaft.

[0012] The drive motor is connected to the helical shaft through the sealed joint to drive the helical shaft to rotate.

[0013] Optionally, the molten salt inlet is located at the lower part of the second end of the annular space, and the extending direction of the molten salt inlet is perpendicular to the axial direction of the annular space;

[0014] The molten salt outlet is located at the upper part of the first end of the annular space, and the extension direction of the molten salt outlet is perpendicular to the axial direction of the annular space.

[0015] Optionally, the spiral shaft is provided with a reverse blade with a pitch of 0.5 to 1.0 near the second end. The reverse blade rotates in the opposite direction to the spiral blade and has the same pitch. The solid outlet is located between the spiral blade and the reverse blade.

[0016] And / or, the pitch of the helical blade is 0.8 to 2.0 times the diameter of the helical shaft.

[0017] Optionally, the oxygen carrier inlet is 3 to 6 screw pitches away from the rice husk charcoal inlet;

[0018] And / or, the rice husk charcoal inlet is 1 to 2 screw pitches away from the flue gas passage.

[0019] Optionally, the top of the flue gas passage is 50-100 mm higher than the top of the spiral blade.

[0020] Furthermore, the present invention also provides a method for preparing precipitated silica from biomass by biothermal carbothermal conversion, the method being implemented based on the above-described apparatus for preparing precipitated silica from biomass by biothermal carbothermal conversion, the method comprising the following steps:

[0021] S1. Start the drive motor and add oxygen carrier at 450-550°C from the oxygen carrier inlet to preheat the furnace body to the first temperature using the oxygen carrier.

[0022] S2. Start the molten salt circulation pump and introduce molten salt at 350-450°C into the insulation sleeve to preheat the furnace body to a second temperature, which is higher than the first temperature;

[0023] S3. Add rice husk charcoal from the rice husk charcoal inlet and maintain the feed ratio of rice husk charcoal to oxygen carrier at a predetermined mass ratio. Adjust the speed of the drive motor to keep the rice husk charcoal in the furnace for a predetermined time.

[0024] S4. Adjust the flow rate of the molten salt circulation pump, control the furnace body to maintain the predetermined temperature, separate the solid residue discharged from the solid outlet to obtain oxygen carrier and rice husk ash, send the obtained oxygen carrier to the oxidation furnace for oxidation and then recycle, and the obtained rice husk ash is the white carbon black produced.

[0025] Optionally, the oxygen carrier in step S1 is an oxide of one or more of iron-based, nickel-based, manganese-based, and copper-based materials, or a composite oxide of several of them, and the first temperature is 250–300°C.

[0026] Optionally, the molten salt in step S2 is a ternary mixed molten salt composed of potassium nitrate, sodium nitrate, and sodium nitrite, with a melting point of 140–180°C and a second temperature of 350–400°C.

[0027] Optionally, the rice husk charcoal in step S3 is obtained by pyrolysis at 450–650°C, the predetermined mass ratio is 1:30–1:60, and the predetermined time is 30–60 min.

[0028] Optionally, the predetermined temperature in step S4 is 450–550°C.

[0029] (III) Beneficial Effects

[0030] The aforementioned apparatus for preparing precipitated silica from biomass through carbothermal conversion employs a spiral combustion device to control the residence time of materials within the furnace. This is supplemented by controlling the combustion rate through the ratio of oxygen carrier to rice husk charcoal, and combined with an external molten salt insulation system for temperature control. This achieves precise temperature control during combustion, ensuring that the rice husk charcoal is completely burned without damaging the amorphous silica structure. Furthermore, this invention also proposes a method for preparing precipitated silica from biomass through carbothermal conversion. This method primarily controls the residence time of materials within the furnace by controlling the rotational speed of the drive motor, controls the combustion rate by controlling the ratio of oxygen carrier to rice husk charcoal, and combines this with a molten salt insulation system to control the temperature, thereby achieving efficient preparation of rice husk-derived precipitated silica.

[0031] The above technical solution also has the following beneficial effects:

[0032] 1. Compared with the conventional gas-solid reaction of rice husk charcoal combustion to produce precipitated silica, chemical looping combustion is a solid-solid reaction, which allows for more stable reaction rate control and more uniform temperature control, preventing local overheating and resulting in better quality precipitated silica. Furthermore, the solid oxygen carrier does not introduce impurities into the combustion flue gas, which is almost entirely composed of carbon dioxide, making it easy to separate and capture, and thus producing no carbon emissions.

[0033] 2. A cleverly designed spiral combustion device is used to control the spiral speed by driving a motor, thereby controlling the residence time of materials in the furnace and ensuring complete combustion. The device is easy to operate. Separate oxygen carrier inlets and rice husk charcoal inlets are provided to facilitate the adjustment of their ratio. The design of the flue gas channel allows for the timely removal of combustion-generated gases, which solves the problem of excessive pressure in the furnace due to the inability to remove combustion flue gas in time, thus affecting the operation of the device and improving the stability of equipment operation.

[0034] 3. An external molten salt insulation system is connected through the molten salt inlet and outlet. Taking advantage of the large specific heat capacity of molten salt and the small temperature change during heat absorption / release, the temperature inside the furnace is kept uniform. This can prevent the pyrolysis of carbon from being too low and the combustion from being incomplete, and can also prevent the combustion temperature from being too high and damaging the amorphous silica structure, thus further ensuring the quality of the silica. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the apparatus for preparing silica from biomass by biothermal carbothermal conversion according to the present invention.

[0036] [Explanation of Labels in the Attached Image]

[0037] 1: Drive motor; 2: Sealing joint; 3: Furnace body; 4: Insulation sleeve; 5: Sealing end; 31: Spiral shaft; 32: Spiral blade; 33: Flue gas passage; 34: Reverse blade; 35: Oxygen carrier inlet; 36: Rice husk charcoal inlet; 37: Flue gas outlet; 38: Solid outlet; 41: Spiral guide vane; 42: Molten salt inlet; 43: Molten salt outlet. Detailed Implementation

[0038] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0040] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; "connection" can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] See Figure 1 The present invention provides an apparatus for preparing precipitated silica by biomass carbothermal conversion, comprising: a drive motor 1, a sealing joint 2, a furnace body 3, an insulation sleeve 4, and a sealing end 5.

[0043] The furnace body 3 includes a cylindrical furnace wall and a spiral shaft 31 with spiral blades 32 rotatably mounted inside the furnace wall. The spiral blades 32 may be welded to the spiral shaft 31. An oxygen carrier inlet 35 and a rice husk charcoal inlet 36 are sequentially opened on the upper part of the furnace wall near the first end. The oxygen carrier is first introduced into the furnace body 3 and moves with the spiral blades 32 to heat up. It then contacts and collides with the rice husk charcoal to ensure temperature control. Simultaneously, the oxygen carrier and rice husk charcoal collide and grind each other inside the furnace, which can reduce the particle size of the silica and improve its quality. Furthermore, a solid outlet 38 is opened on the lower part of the furnace wall near the second end. The furnace wall protrudes upwards from the position near the rice husk charcoal inlet 36 to the upper part of the second end, forming a flue gas channel 33 between itself and the spiral blades 32. The flue gas channel 33 can be a rectangular channel, making the cross-section of the furnace wall approximately U-shaped. Multiple flue gas outlets 37 are opened on the upper part of the flue gas channel 33 to facilitate rapid flue gas exhaust.

[0044] Furthermore, an insulation sleeve 4 is installed outside the furnace wall, and a spiral guide vane 41 is installed in the annular space between the insulation sleeve 4 and the furnace wall. Specifically, the spiral guide vane 41 can be welded to the outer surface of the furnace body 3, and the internal shape of the spiral guide vane 41 is adapted to the shape of the furnace wall. A molten salt inlet 42 is formed at the second end of the annular space, and a molten salt outlet 43 is formed at the first end of the annular space. A sealing joint 2 is provided at the first end of the furnace wall, and a sealing end head 5 is provided at the second end of the furnace wall. The sealing joint 2 and the sealing end head 5 together provide rotational support for the spiral shaft 31. The drive motor 1 is connected to the spiral shaft 31 through the sealing joint 2 to drive the spiral shaft 31 to rotate. The first end of the furnace wall and the first end of the annular space are both the ends closest to the drive motor 1.

[0045] Rice husk charcoal and oxygen carrier enter the furnace body 3 through different inlets. Under the stirring of the spiral blades 32, they are thoroughly mixed. The rice husk charcoal undergoes a combustion reaction to produce silica, which is then moved to the solid outlet 38 and discharged by the spiral blades 32. Molten salt at 350-450℃ is introduced through the insulation sleeve 4 outside the furnace body 3 to prevent the furnace body 3 from overheating or losing temperature due to excessively rapid or slow combustion of the rice husk charcoal. The above-mentioned biomass carbon thermal conversion device for producing silica uses a spiral combustion device to control the residence time of the material in the furnace. The combustion rate is controlled by adjusting the ratio of oxygen carrier to rice husk charcoal, and temperature is controlled by an external molten salt insulation system. This achieves precise temperature control during combustion, ensuring that the rice husk charcoal is completely burned without damaging the amorphous silica structure. Simultaneously, the collision and grinding of the oxygen carrier and rice husk charcoal within the furnace reduces the particle size of the silica, improving its quality. Compared to the conventional gas-solid reaction of rice husk charcoal to produce silica, chemical looping combustion is a solid-solid reaction, which allows for more stable reaction rate control and more uniform temperature control, preventing local overheating and resulting in higher quality silica. Furthermore, the solid oxygen carrier does not introduce impurities into the combustion flue gas, which is almost entirely composed of carbon dioxide, facilitating its separation and capture, and preventing carbon emissions.

[0046] Furthermore, the above-mentioned scheme cleverly incorporates a spiral combustion device. The spiral speed is controlled by the drive motor 1 to regulate the residence time of the material within the furnace, ensuring complete combustion and simplifying operation. Separate oxygen carrier inlets 35 and rice husk char inlets 36 facilitate adjustment of their ratio. A flue gas channel 33 is designed to promptly exhaust combustion gases, preventing excessive furnace pressure and ensuring stable operation. An external molten salt insulation system is connected via the molten salt inlet 42 and outlet 43. Utilizing the high specific heat capacity and small temperature fluctuations during heat absorption / release of molten salt, a uniform furnace temperature is maintained. This prevents incomplete combustion of pyrolyzed char due to low furnace temperature and avoids damage to the amorphous silica structure due to excessively high combustion temperature, further guaranteeing the quality of the silica.

[0047] In a preferred embodiment, the molten salt inlet 42 is located at the lower part of the second end of the annular space, and the extension direction of the molten salt inlet 42 is perpendicular to the axial direction of the annular space; the molten salt outlet 43 is located at the upper part of the first end of the annular space, and the extension direction of the molten salt outlet 43 is perpendicular to the axial direction of the annular space. This arrangement allows the extension direction of the molten salt inlet 42 or the molten salt outlet 43 to be the same as the tangential direction of the spiral guide vane 41, thereby improving the smoothness of molten salt feeding and discharging.

[0048] Furthermore, see again Figure 1 In a more preferred embodiment, a reverse blade 34 with a pitch of 0.5 to 1.0 is provided on the spiral shaft 31 near the second end. The reverse blade 34 rotates in the opposite direction to the spiral blade 32 and has the same pitch. The solid outlet 38 is located between the spiral blade 32 and the reverse blade 34. That is, the spiral blade 32 and the reverse blade 34 are not arranged on the spiral shaft 31 directly opposite the solid outlet 38, thereby ensuring that the solid can be completely discharged. And / or, the pitch of the spiral blade 32 is 0.8 to 2.0 times the diameter of the spiral shaft 31 to facilitate control of the feeding speed.

[0049] In addition, the oxygen carrier inlet 35 is spaced 3 to 6 screw pitches apart from the rice husk charcoal inlet 36 to ensure sufficient heating time for the oxygen carrier. And / or, the rice husk charcoal inlet 36 is spaced 1 to 2 screw pitches apart from the flue gas passage 33 to ensure smooth exhaust of flue gas as soon as the oxygen carrier and rice husk charcoal begin to react after mixing. The top of the flue gas passage 33 is 50 to 100 mm higher than the top of the spiral blade 32, thus creating a sufficiently large flue gas expansion space to prevent excessive flue gas pressure, and multiple flue gas outlets 37 are correspondingly provided to minimize flue gas residence time.

[0050] Furthermore, the present invention also provides a method for preparing precipitated silica from biomass carbothermal conversion, the method being implemented based on the aforementioned apparatus for preparing precipitated silica from biomass carbothermal conversion, and the method comprising the following steps:

[0051] S1. Start the drive motor 1 and add oxygen carrier at 450-550°C from the oxygen carrier inlet 35 to preheat the furnace body 3 to the first temperature using the oxygen carrier.

[0052] S2. Start the molten salt circulation pump and introduce molten salt at 350-450°C into the insulation sleeve 4 to preheat the furnace body 3 to the second temperature, which is higher than the first temperature.

[0053] S3. Add rice husk charcoal from rice husk charcoal inlet 36 and maintain the feed ratio of rice husk charcoal to oxygen carrier at a predetermined mass ratio. Adjust the speed of drive motor 1 so that the rice husk charcoal stays in the furnace for a predetermined time.

[0054] S4. Adjust the flow rate of the molten salt circulation pump to control the furnace body 3 to maintain the predetermined temperature. Separate the solid residue discharged from the solid outlet 38 to obtain the oxygen carrier and rice husk ash. The obtained oxygen carrier is sent to the oxidation furnace for oxidation and then recycled. The obtained rice husk ash is the white carbon black produced.

[0055] In step S2, molten salt at 350–450°C is introduced into the insulation sleeve 4 outside the furnace body to prevent the furnace body from overheating or losing temperature due to excessively fast or slow combustion of rice husk charcoal. The above method mainly controls the residence time of materials in the furnace by controlling the speed of the drive motor 1, controls the combustion rate by controlling the ratio of oxygen carrier to rice husk charcoal, and controls the temperature by combining the molten salt insulation system, thereby achieving efficient preparation of rice husk-derived silica.

[0056] In a preferred embodiment, the oxygen carrier in step S1 can be an oxide of one or more of the following: iron-based, nickel-based, manganese-based, and copper-based, or a composite oxide of several of them, with a first temperature of 250–300°C. The molten salt in step S2 is a ternary mixed molten salt composed of potassium nitrate, sodium nitrate, and sodium nitrite, with a melting point of 140–180°C and a second temperature of 350–400°C. The rice husk charcoal in step S3 is obtained by pyrolysis at 450–650°C, with a predetermined mass ratio of 1:30–1:60 and a predetermined time of 30–60 min. The predetermined temperature in step S4 is 450–550°C.

[0057] The above method will be described below based on specific embodiments, and the method specifically includes the following steps:

[0058] S1. Start the drive motor 1 and add iron oxide oxygen carrier at 450-550°C from the oxygen carrier inlet 35. Use the oxygen carrier to preheat the furnace body 3 to 250°C.

[0059] S2. Start the molten salt circulation pump and introduce molten salt at 350-450°C into the insulation sleeve 4 to preheat the furnace body 3 to 400°C.

[0060] S3. Add rice husk charcoal through rice husk charcoal inlet 36 and maintain the feed ratio of rice husk charcoal to oxygen carrier at a predetermined mass ratio of 1:30. Adjust the speed of drive motor 1 so that the rice husk charcoal stays in the furnace for 40 minutes.

[0061] S4. Adjust the flow rate of the molten salt circulation pump to control the temperature inside the furnace body 3 to 550℃. Separate the solid residue discharged from the solid outlet 38 to obtain oxygen carrier and rice husk ash. The separated oxygen carrier is sent to the oxidation furnace for oxidation and then recycled. The separated rice husk ash is the white carbon black produced.

[0062] By using the above method to prepare precipitated silica through precise temperature control, the yield can reach over 95% and the purity (silicon dioxide content) can reach over 98%, realizing the efficient preparation of precipitated silica from rice husks and greatly improving the utilization value of rice husks.

[0063] It should be understood that the above description of specific embodiments of the present invention is only for illustrating the technical approach and features of the present invention, and is intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, the present invention is not limited to the specific embodiments described above. All changes or modifications made within the scope of the claims of the present invention should be covered within the protection scope of the present invention.

Claims

1. An apparatus for preparing precipitated silica from biomass through biothermal carbide conversion, characterized in that, The device includes: a drive motor (1), a sealing joint (2), a furnace body (3), an insulation sleeve (4), and a sealing end (5); The furnace body (3) includes a cylindrical furnace wall and a spiral shaft (31) with spiral blades (32) rotatably disposed inside the furnace wall; an oxygen carrier inlet (35) and a rice husk charcoal inlet (36) are sequentially opened on the upper part of the furnace wall near the first end, and a solid outlet (38) is opened on the lower part of the furnace wall near the second end. The upper part of the furnace wall near the rice husk charcoal inlet (36) protrudes upward and forms a flue gas channel (33) between the furnace wall and the spiral blades (32). Multiple flue gas outlets (37) are opened on the flue gas channel (33). The insulation sleeve (4) is installed outside the furnace wall. A spiral guide vane (41) is installed in the annular space between the insulation sleeve (4) and the furnace wall. A molten salt inlet (42) is formed at the second end of the annular space, and a molten salt outlet (43) is formed at the first end of the annular space. The molten salt inlet (42) is located at the lower part of the second end of the annular space, and the extension direction of the molten salt inlet (42) is perpendicular to the axial direction of the annular space. The molten salt outlet (43) is located at the upper part of the first end of the annular space, and the extension direction of the molten salt outlet (43) is perpendicular to the axial direction of the annular space. The first end of the furnace wall is provided with the sealing joint (2) and the second end of the furnace wall is provided with the sealing end (5). The sealing joint (2) and the sealing end (5) together provide rotational support for the spiral shaft (31). The drive motor (1) is connected to the spiral shaft (31) through the sealing joint (2) to drive the spiral shaft (31) to rotate.

2. The apparatus for preparing precipitated silica from biomass carbon thermal conversion according to claim 1, characterized in that, The spiral shaft (31) is provided with a reverse blade (34) with a pitch of 0.5 to 1.0 near the second end. The reverse blade (34) rotates in the opposite direction to the spiral blade (32) and has the same pitch. The solid outlet (38) is located between the spiral blade (32) and the reverse blade (34). And / or, the pitch of the helical blade (32) is 0.8 to 2.0 times the diameter of the helical shaft (31).

3. The apparatus for preparing precipitated silica from biomass by biothermal carbon conversion according to claim 1, characterized in that, The oxygen carrier inlet (35) is 3 to 6 pitches away from the rice husk charcoal inlet (36); And / or, the rice husk charcoal inlet (36) is 1 to 2 pitches away from the flue gas passage (33).

4. The apparatus for preparing precipitated silica from biomass carbon thermal conversion according to claim 1, characterized in that, The top of the flue gas passage (33) is 50-100 mm higher than the top of the spiral blade (32).

5. A method for preparing precipitated silica from biomass by biothermal carbide conversion, said method being implemented based on the apparatus for preparing precipitated silica from biomass by biothermal carbide conversion according to any one of claims 1-4, characterized in that, The method includes the following steps: S1. Start the drive motor (1) and add oxygen carrier at 450~550°C from the oxygen carrier inlet (35) to preheat the furnace body (3) to the first temperature using the oxygen carrier. S2. Start the molten salt circulation pump and introduce molten salt at 350~450°C into the insulation sleeve (4) to preheat the furnace body (3) to a second temperature, which is higher than the first temperature; S3. Add rice husk charcoal from the rice husk charcoal inlet (36) and keep the feed ratio of rice husk charcoal to oxygen carrier at a predetermined mass ratio. Adjust the speed of the drive motor (1) so that the rice husk charcoal stays in the furnace for a predetermined time. S4. Adjust the flow rate of the molten salt circulation pump, control the furnace body (3) to maintain the predetermined temperature, separate the solid residue discharged from the solid outlet (38) to obtain oxygen carrier and rice husk ash, send the obtained oxygen carrier to the oxidation furnace for oxidation and then recycle, and the obtained rice husk ash is the white carbon black produced.

6. The method for preparing precipitated silica from biomass by biothermal conversion according to claim 5, characterized in that, The oxygen carrier in step S1 is an oxide of one of iron-based, nickel-based, manganese-based and copper-based materials or a composite oxide of several of them, and the first temperature is 250~300℃.

7. The method for preparing precipitated silica from biomass by biothermal conversion according to claim 5, characterized in that, The molten salt in step S2 is a ternary mixed molten salt composed of potassium nitrate, sodium nitrate, and sodium nitrite, with a melting point of 140~180℃ and a second temperature of 350~400℃.

8. The method for preparing precipitated silica from biomass by biothermal conversion according to claim 5, characterized in that, The rice husk charcoal in step S3 is obtained by pyrolysis at 450~650℃, the predetermined mass ratio is 1:30~1:60, and the predetermined time is 30~60min.

9. The method for preparing precipitated silica from biomass by biothermal conversion according to claim 5, characterized in that, The predetermined temperature in step S4 is 450~550℃.

Images