Biomass impurity removal method as well as preparation method and application of biological carbon powder

Abstract

The invention provides a biomass impurity removal method and a preparation method and application of biological carbon powder, and relates to the technical field of solid waste treatment.The biomass impurity removal method comprises the following steps that biomass is sequentially subjected to crushing, fluidized bed separation, dust removal, magnetic separation, water washing and drying, and biomass powder with impurities removed is obtained. According to the method, biomass is crushed and then subjected to multi-stage impurity removal, external ash on the surface can be removed, internal ash of the biomass can also be removed, and the impurity content of the obtained biomass powder is greatly reduced through cooperative treatment of multiple impurity removal methods.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste treatment, and in particular to a biomass impurity removal method and a biocarbon powder preparation method and application. Background Art

[0002] In the process of resource processing of biomass, one of the methods is to use low-temperature baking for processing, but biomass will carry a lot of impurities, which will affect the quality of biochar powder. The traditional method is to perform preliminary impurity removal before crushing, and remove the iron wire and sand and gravel in it through a vibrating screen, but part of the biomass will be taken away during the impurity removal process, resulting in the loss of biomass straw, leading to increased costs, and the dust removal efficiency is affected by its own morphological structure. The dust in the texture structure cannot be removed, making it impossible to remove the soil of the biomass itself. This is because when biomass is baked at low temperature, there is often a lot of dust attached to the surface, so that the biochar powder carries a lot of impurities. Usually affected by the texture of the biomass straw structure, the fine particles mixed in the gaps and the inherent ash (such as inorganic salts) of the biomass cannot be removed and are not easy to remove, resulting in poor dust removal efficiency, and the separation process before crushing will cause the loss of organic matter, which increases the cost of biomass resource utilization.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] One of the purposes of the present invention is to provide a biomass impurity removal method to at least solve one of the technical problems existing in the prior art. The biomass impurity removal method comprises the following steps: crushing the biomass, fluidized bed sorting, dust removal, magnetic separation, water washing and drying in sequence to obtain the impurity-removed biomass powder. The present invention performs multi-stage impurity removal after the biomass is crushed, which can not only remove the external ash on the surface, but also remove the internal ash of the biomass. Through the coordinated treatment of multiple impurity removal methods, the impurity content of the obtained biomass powder is greatly reduced.

[0005] The second object of the present invention is to provide an application of the biomass impurity removal method in the preparation of bio-carbon powder. The present invention performs multi-stage impurity removal on biomass to separate impurities at the front end of biomass baking, and finally bakes to obtain high calorific value bio-carbon powder, which has more concentrated energy and high energy yield.

[0006] The third object of the present invention is to provide a method for preparing biochar powder, which comprises the following steps: baking the biomass powder after impurities are removed by the biomass impurity removal method to obtain biochar powder. The method for preparing biochar powder provided by the present invention crushes the biomass, and then sequentially performs crushing, fluidized bed sorting, dust removal, magnetic separation, water washing, drying and baking, with high impurity removal efficiency, not only removing the external ash on the surface of the biomass, but also removing the internal ash of the biomass, and finally realizing the carbonization of the biomass, preparing the biochar powder with uniform component materials and high energy density by improving the quality and efficiency of the biomass, which can be further used for the preparation of green energy, enriching the back-end process route.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] In a first aspect, the present invention provides a biomass impurity removal method, the biomass impurity removal method comprising the following steps:

[0009] The biomass is sequentially crushed, fluidized bed sorted, dusted, magnetically separated, washed and dried to obtain the impurity-free biomass powder.

[0010] Furthermore, the crushing includes a first crushing and a second crushing in sequence;

[0011] Preferably, the particle size of the biomass powder obtained after the first crushing is 20-100 mm, and the particle size of the biomass powder obtained after the second crushing is 5-10 mm;

[0012] Preferably, the width of the blade used for the first crushing is 10-14 mm, the number of blades is 2-4 groups, each group of blades includes a moving blade and a stationary blade arranged at intervals, and the rotation speed of the moving blade is 2800-3000 r / min;

[0013] Preferably, the width of the blade used for the second crushing is 4-6 mm, the number of blades is 4-6 groups, each group of blades includes a moving blade and a stationary blade arranged at intervals, and the rotation speed of the moving blade is 2800-3000 r / min;

[0014] Preferably, the first crushing adopts a coarse crusher, and the second crushing adopts a vertical crusher.

[0015] Furthermore, the fluidized bed separation includes: using a fluidized medium to suspend light matter in the biomass powder, using a fluidized bed to put heavy matter in the biomass powder in a non-fluidized state, separating and transporting the light matter to the dust removal process through the fluidized bed, and removing the heavy matter;

[0016] Preferably, the heavy objects include sand and / or metal;

[0017] Preferably, the fluidizing medium comprises air at room temperature, the fluidizing velocity is 4.5-6.5 cm / s, the air inlet temperature of the fluidizing medium is 160-170° C., and the wind pressure is 0.05-0.2 MPa.

[0018] Furthermore, the dust removal includes primary dust removal and secondary dust removal in sequence, wherein the primary dust removal is used to remove large dust particles, and the secondary dust removal is used to remove sticky particles generated in the primary dust removal;

[0019] Preferably, the primary dust removal and the secondary dust removal use a cyclone dust collector, and the ratio of the barrel diameter of the cyclone dust collector to the exhaust pipe diameter is 2-3;

[0020] Preferably, an electrostatic field is provided after the primary dust removal so that the impurity particles are negatively charged and deposited at the anode;

[0021] Preferably, the inlet air flow velocity of the primary dust removal is 20-25 m / s and the temperature is 120-130°C;

[0022] Preferably, the inlet air flow velocity of the secondary dust removal is 16-20 m / s and the temperature is 80-90°C.

[0023] Furthermore, the magnetic separation is used to remove iron-containing substances in biomass powder;

[0024] Preferably, a magnetic separator is used to carry out the magnetic separation process;

[0025] Preferably, the rotation speed of the cylinder used for the magnetic separation is 30-40 r / min, the magnetic deflection angle of the magnetic separation is 15-20 degrees, and the magnetic field strength is 500 Gauss-3500 Gauss.

[0026] Furthermore, the water washing includes soaking and stirring the biomass powder in sequence, dissolving inorganic salts in the internal structure of the biomass in water through water washing, thereby removing the inorganic salts;

[0027] Preferably, the water used for washing has a temperature of 60-80°C and a pH of 6-7;

[0028] Preferably, the soaking time is 50-60 min;

[0029] Preferably, the stirring time is 20-30 min.

[0030] Furthermore, the drying includes performing solid-liquid separation on the washed biomass powder, and then drying the solid material to obtain dry biomass powder;

[0031] Preferably, a hydrocyclone separator is used for the solid-liquid separation process, and a cyclone dryer is used for the drying process;

[0032] Preferably, during the solid-liquid separation process, the water inlet pressure of the hydrocyclone is greater than 0.4 MPa, and the pressure loss of the hydrocyclone is 0.028-0.032 MPa.

[0033] Preferably, the inlet air temperature of the drying process is 100-150°C, and the exhaust air temperature is 50-70°C.

[0034] In a second aspect, the present invention provides an application of the biomass impurity removal method in the preparation of bio-carbon powder.

[0035] In a third aspect, the present invention provides a method for preparing bio-carbon powder, the method comprising the following steps:

[0036] The biomass powder after impurities are removed by the biomass impurity removal method is baked to obtain bio-carbon powder.

[0037] Furthermore, the baking temperature is 200-220°C, the baking time is 20-30min, and the heating rate is 20°C / min;

[0038] Preferably, the heat source for baking is one of water vapor, hot flue gas and inert gas.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The biomass impurity removal method provided by the present invention performs multi-stage impurity removal after the biomass is crushed. First, the particle size of the biomass is reduced by a crushing process, the heavy matter in the biomass powder is removed by a fluidized bed sorting process, the dust is removed by a dust removal process, the iron-containing matter is removed by a magnetic separation process, and then the inorganic matter is removed by a water washing process, and finally the biomass powder is dried. The impurity removal method of the present invention can not only remove the external ash on the surface of the biomass, but also remove the internal ash of the biomass. Through the coordinated treatment of multiple impurity removal methods, the impurity content of the obtained biomass powder is greatly reduced.

[0041] The method for preparing biochar powder provided by the present invention performs multi-stage impurity removal on biomass and then bakes the biomass to prepare biochar powder, thereby improving fuel properties and achieving full resource utilization of biomass. DETAILED DESCRIPTION

[0042] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The first aspect of the present invention provides a biomass impurity removal method, which comprises the following steps: sequentially crushing, fluidized bed sorting, dust removal, magnetic separation, water washing and drying the biomass to obtain impurity-removed biomass powder.

[0045] In the present invention, after the biomass is crushed, multi-stage impurity removal is performed. First, the particle size of the biomass is reduced by a crushing process, the heavy matter in the biomass powder is removed by a fluidized bed sorting process, the dust is removed by a dust removal process, the iron-containing matter is removed by a magnetic separation process, and then the inorganic matter is removed by a water washing process, and finally the biomass powder is dried. The impurity removal method of the present invention can not only remove the external ash on the surface of the biomass, but also remove the internal ash (such as inorganic salts) of the biomass. Through the coordinated treatment of multiple impurity removal methods, the impurity content of the obtained biomass powder is greatly reduced.

[0046] Furthermore, the crushing includes a first crushing and a second crushing in sequence;

[0047] Preferably, the particle size of the biomass powder obtained after the first crushing is 20-100mm, for example, it can be 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, 100mm, etc., and the particle size of the biomass powder obtained after the second crushing is 5-10mm, for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.;

[0048] Preferably, the width of the blade used for the first crushing is 10-14 mm, for example, it can be 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, etc., the number of blades is 2-4 groups, for example, it can be 2 groups, 3 groups, 4 groups, etc., each group of blades includes a moving knife and a stationary knife arranged at intervals, the rotation speed of the moving knife is 2800-3000 r / min, for example, it can be 2800 r / min, 2850 r / min, 2900 r / min, 2950 r / min, 3000 r / min, etc., and the rotation speed of the moving knife is further preferably 2960 r / min;

[0049] Preferably, the width of the blade used for the second crushing is 4-6 mm, for example, 4 mm, 5 mm, 6 mm, etc., the number of blades is 4-6 groups, for example, 4 groups, 5 groups, 6 groups, etc., each group of blades includes a moving knife and a stationary knife arranged at intervals, the rotation speed of the moving knife is 2800-3000 r / min, for example, 2800 r / min, 2850 r / min, 2900 r / min, 2950 r / min, 3000 r / min, etc., and the rotation speed of the moving knife is further preferably 2890 r / min;

[0050] Preferably, the first crushing adopts a coarse crusher, and the second crushing adopts a vertical crusher.

[0051] In the present invention, the biomass is firstly crushed to make the biomass particle size 5-10 mm. In order to obtain the biomass of the required particle size, the first crushing (i.e., coarse crushing) and the second crushing (i.e., fine crushing) are used in combination. After the first crushing, the second crushing is performed to improve the efficiency and quality of the crushing.

[0052] Specifically, regarding the first crushing: the first crushing uses a coarse crusher, which is mainly composed of a feed port, a circular hollow crushing chamber, and a discharge port. The size of the crushing chamber is D×L=1000mm×600mm. It is equipped with an electric motor and a belt drive to drive the moving knife used in the first crushing to rotate in order to reduce damage to the shaft. The belt drive ratio is 1:1, wherein each set of blades includes a moving knife and a stationary knife, which are arranged at intervals and cooperate with each other for crushing.

[0053] Specifically, regarding the second crushing: the second crushing uses a vertical crusher, which can also be called a fine crusher or a secondary crusher, for fine crushing of the coarse crushing products. The fine crusher uses a total of four motors with a rated power of 15kW and a rated current of 28.9A. It is still equipped with an electric motor and a belt drive to drive the moving knife used in the second crushing to rotate. The belt drive ratio is also 1:1. Among them, each set of blades includes a moving knife and a stationary knife. The moving knife and the stationary knife are arranged at intervals and cooperate with each other for crushing. The fine crusher is mainly composed of a feed pipe, a crushing chamber, a discharge pipe and a power transmission device. When working, the coarse crushing products are quickly fed into the fine crusher from the entrance near each set of blades by the negative pressure formed by the high-speed rotation of several sets of blades in the crushing chamber and the suction effect of the fan at the end of the system. Since the materials entering the fine crushing system have passed the primary crushing of the previous coarse crusher, the average particle size is less than 100mm. Therefore, in the fine crusher, the materials are mainly ground with the help of the high-speed rotation of the motor and the grinding between the blades and the mutual grinding between the materials to achieve a finer particle size. After grinding and mutual grinding, the materials with small particle size will float on the upper layer, and then be pumped by the fan from the outlet at the upper end of the crushing chamber to the fluidized bed sorting device of the next process, while the particles with relatively large particle size will remain in the lower layer due to gravity and continue to be crushed. Among them, after crushing, the materials with small particle size can be pumped to the fluidized bed, and a screen is set at the outlet near the upper end of the crushing chamber. The materials that meet the particle size can pass through and enter the next fluidized bed sorting process, and the materials that do not meet the particle size continue to be crushed at the bottom until they meet the particle size.

[0054] Furthermore, the fluidized bed separation includes: using a fluidized medium to suspend light matter in the biomass powder, using a fluidized bed to put heavy matter in the biomass powder in a non-fluidized state, separating and transporting the light matter to the dust removal process through the fluidized bed, and removing the heavy matter;

[0055] Preferably, the heavy objects include sand and / or metal;

[0056] In the present invention, a fluidized bed sorting process is adopted, and gas or liquid is used to pass through a granular solid layer to put the solid particles in a suspended motion state. The heavy matter is put into a bubbling state or a non-fluidized state through the fluidized bed, and the light matter (i.e., light organic matter) is blown away in an entrained state in the fluidized bed. The separation efficiency is controlled by controlling the wind speed, and part of the sand and metal in the biomass is separated.

[0057] Preferably, the fluidizing medium comprises air at room temperature, and the fluidizing velocity is 4.5-6.5 cm / s, for example, it can be 4.5 cm / s, 5 cm / s, 5.5 cm / s, 6 cm / s, 6.5 cm / s, etc. The inlet temperature of the fluidizing medium is 160-170°C, for example, it can be 160°C, 165°C, 170°C, etc., and the wind pressure is 0.05-0.2 MPa, for example, it can be 0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa, etc.

[0058] In the present invention, air at room temperature is used as the fluidizing medium. The power system consists of air, a blower, and an air bag. The blower provides the fluidizing medium, which enters the air distribution plate after being pressure-stabilized by the air bag. The air volume and air pressure entering the fluidized bed are adjusted by the control valve. The initial fluidizing velocity is 4.5-6.5 cm / s, the fluidizing air inlet temperature is 160-170°C, and the air pressure is 0.05-0.2 MPa. The biomass powder sorted from the fluidized bed enters the next dust removal process.

[0059] Furthermore, the dust removal includes primary dust removal and secondary dust removal in sequence, wherein the primary dust removal is used to remove large dust particles, and the secondary dust removal is used to remove sticky particles generated in the primary dust removal;

[0060] Preferably, the primary dust removal and the secondary dust removal use a cyclone dust collector, and the ratio of the barrel diameter of the cyclone dust collector to the exhaust pipe diameter is 2-3, for example, it can be 2, 3, etc.;

[0061] In the present invention, a cyclone dust collector is used for separation, which is also called a cyclone separator. It is a device that uses centrifugal force to remove dust particles or droplets from an airflow. Its working principle is based on density difference, that is, the density between solid or liquid particles and gas is different, so that the centrifugal force on the particles in the rotating airflow is greater than the centripetal force of the airflow, so that they are thrown onto the wall of the cyclone dust collector and slide down along the wall to the bottom for discharge, and the purified gas leaves from the top. The cyclone dust collector uses the centrifugal force generated by the rotating dust-containing airflow to separate the substances in the material from the gas by using the difference in density. When the dust-containing airflow enters the cyclone dust collector from the air inlet pipe, the airflow changes from linear motion to circular motion. Most of the rotating airflow spirals downward along the wall and the cylinder and flows toward the cone, which is an external vortex. The dust-containing gas generates centrifugal force during the rotation process, throwing particles with a density greater than that of the gas toward the wall. Once the particles come into contact with the wall, they lose their inertial force and fall along the wall by the momentum of the inlet velocity and the downward gravity, and enter the ash discharge pipe. Among them, the ratio of the cylinder diameter of the cyclone dust collector to the exhaust pipe diameter is 2-3, which helps to optimize the dust removal efficiency and ensure that under the same pressure loss, the cyclone dust collector can process about 3 times the amount of gas as other types of dust collectors, while achieving uniformity of airflow distribution.

[0062] Preferably, the inlet air flow velocity of the primary dust removal is 20-25 m / s, for example, it can be 20 m / s, 21 m / s, 22 m / s, 23 m / s, 24 m / s, 25 m / s, etc., the inlet air flow velocity is further preferably 23 m / s, and the temperature is 120-130°C, for example, it can be 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, etc.;

[0063] Preferably, the inlet air flow velocity of the secondary dust removal is 16-20m / s, for example, it can be 16m / s, 17m / s, 18m / s, 19m / s, 20m / s, etc., and the inlet air flow velocity is further preferably 18m / s, and the temperature is 80-90℃, for example, it can be 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, etc.

[0064] In the present invention, the present invention adopts the combination of primary dust removal and secondary dust removal. After the primary dust removal, the secondary dust removal is carried out to improve the efficiency and quality of dust removal. During dust removal, the proper control of the inlet airflow velocity is crucial to improving the dust removal efficiency and separation efficiency of the cyclone dust collector. The proper inlet airflow velocity can effectively improve the performance of the cyclone dust collector, but too high a velocity may lead to a decrease in separation efficiency and increased equipment wear. Specifically, the inlet airflow velocity of the primary dust removal is controlled within the range of 20-25m / s, and the temperature during the gas separation process is 120-130°C. Because the temperature is too high, it will increase its viscosity, so that the centripetal force on the dust particles is increased, thereby reducing the separation efficiency. The external ash dust removal efficiency of the primary dust removal can reach 82-84%. The inlet airflow velocity of the secondary dust removal is controlled within the range of 16-20m / s, and the temperature during the gas separation process is controlled at 80-90°C, so that the viscous particles caused by the temperature in the primary dust removal process are further removed, and the external ash dust removal efficiency of the secondary dust removal can be improved by 87-88%. In summary, the first-stage dust collector removes large pieces of dust and then enters the next stage. By adjusting the air velocity, the second-stage dust collector removes small-size viscous particles. Among them, the two-stage cyclone dust collector sets up two cyclone separation units, and the two sets of specifications and sizes are the same. The advantages of the two-stage cyclone dust collector are to improve the dust removal efficiency and handle a wider range of particle sizes, realizing the double separation of dust, thereby improving the overall dust removal efficiency. It is suitable for handling dust containing larger particles, because a single-stage cyclone dust collector may not be able to effectively handle larger particles. The setting of the two-stage cyclone dust collector can better separate and collect these larger particles, thereby improving the dust removal efficiency of the entire system. Through two-stage separation, particles from tiny to larger can be handled more effectively, which makes it have a wider range of applications when dealing with various types of dust.

[0065] Preferably, an electrostatic field is set after the primary dust removal and before the secondary dust removal, so that the impurity particles are negatively charged and deposited at the anode, so that the impurity particles are further separated from the biomass powder;

[0066] In the present invention, an electrostatic field is set in the channel between the primary dust removal and the secondary dust removal, and the electric field strength is 5-20kv / cm. The gas is electrically separated when passing through the high-voltage electrostatic field. The effective retention time of the gas in the electric field is 4-6s. After the impurity particles are combined with negative ions and carry negative charges, they tend to discharge and deposit on the anode surface. The dust removal principle is to use the electrostatic field to ionize the airflow so that the impurities are charged and adsorbed on the electrode for dust removal. In the strong electric field, the air molecules are ionized into positive ions and electrons. The electrons encounter impurity particles in the process of rushing to the positive electrode, so that the impurity particles are negatively charged and adsorbed to the positive electrode and collected, thereby realizing the separation of biomass powder and other impurity particles.

[0067] Furthermore, the magnetic separation is used to remove iron-containing substances in biomass powder;

[0068] Preferably, a magnetic separator is used to carry out the magnetic separation process;

[0069] Preferably, the rotation speed of the cylinder used for the magnetic separation is 30-40r / min, for example, it can be 30r / min, 31r / min, 32r / min, 33r / min, 34r / min, 35r / min, 36r / min, 37r / min, 38r / min, 39r / min, 40r / min, etc., the magnetic declination of the magnetic separation is 15-20 degrees, for example, it can be 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, etc., and the magnetic field strength is 500 Gauss-3500 Gauss, for example, it can be 500 Gauss, 1000 Gauss, 1500 Gauss, 2000 Gauss, 2500 Gauss, 3000 Gauss, 3500 Gauss, etc.

[0070] In the present invention, magnetism is used to separate the substances therein. Soil usually contains iron. The iron-containing substances are separated by magnetic separation. By adjusting the magnetic field strength, both ferroferric oxide and ferric oxide can be separated in a strong magnetic field. When performing magnetic separation, the cylinder diameter is preferably 750 mm, the cylinder speed is preferably 36 r / min, and the appropriate adjustment of the cylinder speed is conducive to improving the recovery rate of iron. The magnetic declination is set at 15-20 degrees. The size of the magnetic declination directly affects the width of the scanning area. As the magnetic declination increases, the scanning area becomes narrower, which also affects the recovery rate of iron.

[0071] Furthermore, the water washing includes soaking and stirring the biomass powder in sequence, dissolving inorganic salts in the internal structure of the biomass in water through water washing, thereby removing the inorganic salts;

[0072] In the present invention, after magnetic separation, water washing is used to remove not only dust from the biomass powder but also inorganic salts in the biomass, thereby efficiently removing intrinsic ash and extrinsic ash in the biomass powder and improving the quality of the baked carbon powder.

[0073] Furthermore, after washing, flushing is also included, and flushing is a step of transporting the soaked and stirred biomass powder to the next process using running water.

[0074] Preferably, the temperature of the water used for washing is 60-80°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the pH is 6-7, for example, 6, 6.5, 7, etc.;

[0075] Preferably, the soaking time is 50-60 min, for example, it can be 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min, 60 min, etc.;

[0076] Preferably, the stirring time is 20-30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, etc.;

[0077] In the present invention, a water washing process is used to remove inorganic matter. The water washing is based on the difference in solubility of solutes. When impurities are attached to the surface or inside of the biomass, these solutes can be dissolved in water through water washing, thereby achieving the removal of impurities.

[0078] Specifically, the soil surface is hydrophilic, and the biomass straw is hydrophobic. After adding water, mud can be formed. Water-soluble inorganic matter can be dissolved in water, and organic matter floats on the water surface. It can be seen that water washing can not only remove external ash, but also remove internal ash, and realize the separation of organic matter and inorganic matter. Water washing removes internal ash and external ash in biomass without the use of organic solvents or chemical reagents. It is environmentally friendly and produces less pollutants. In addition, water washing has a small impact on the material and will not change the inherent properties of the material. At the same time, it removes a variety of impurities therein, which is simple to operate and low in cost. Since the traditional method is to remove impurities and dust by drum screening before crushing, a large amount of biomass will be lost in the impurity removal process, and the impurity removal efficiency is not high. The present invention performs multi-process synergistic treatment on the crushed biomass, cooperates with each other, and the impurity removal efficiency of the water washing process and other processes is high, and finally high-quality biomass carbon powder is obtained.

[0079] Furthermore, the drying includes performing solid-liquid separation on the washed biomass powder, and then drying the solid material to obtain dry biomass powder;

[0080] Preferably, a hydrocyclone separator is used for the solid-liquid separation process, and a cyclone dryer is used for the drying process;

[0081] Preferably, the water inlet pressure of the hydrocyclone during the solid-liquid separation process is greater than 0.4 MPa, and the pressure loss of the hydrocyclone is 0.028 MPa-0.032 MPa;

[0082] Preferably, the inlet air temperature of the drying treatment is 100-150°C, for example, it can be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., and the exhaust air temperature is 50-70°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0083] In the present invention, the biomass powder is dried in a cyclone manner. First, the solid particles are separated from the suspension by the centrifugal sedimentation principle of the hydrocyclone separator. The feed liquid enters from the cylindrical part in a tangential direction and generates centrifugal force by rotating motion. The centrifugal force becomes more intense when it descends to the conical part. The solid particles in the feed liquid are thrown to the wall of the device under the action of the centrifugal force and flow down to the outlet (bottom flow) along the wall in a spiral line. The clarified liquid rises and overflows from the central outlet. Then, the hot air flow carries the dried material particles into the cyclone dryer in a tangential direction and generates a rotating motion along the hot wall, so that the material particles are in a suspended rotating motion state for drying. The wall of the device can be provided with a steam jacket as needed, and the drying process is greatly enhanced. In addition, the particles are crushed due to collision with the wall, and the contact area of ​​the gas-solid phase is increased, which also enhances the drying process. The hydrocyclone separator is used for cyclone separation to achieve the purpose of liquid-solid separation, and then the cyclone dryer is used to dry the material.

[0084] The cyclone dryer uses the rotational energy in the rotating flow field of the airflow in the dryer to make the gas-solid mixture swirl, and classify and dry the moving materials according to the length of drying time required for the particle size. The hot air flow carries the wet material and enters the first-level drying chamber at the bottom of the dryer at a high speed tangent. Under the action of the rotating force and centrifugal force, the material rotates with the airflow in the drying chamber and is separated from the gas and solid. After separation, the gas enters the upper drying chamber from the center hole, and the bottom drying chamber is filled with new materials until the drying chamber is full of materials and overflows to the upper drying chamber with the airflow, and repeats the original material filling process. During the continuous filling process, the material stays in the drying chamber for a long time. The wet material is well dried in the hot air flow by relying on the heat transfer provided by the hot gas convection and the heat radiation provided by the drying wall jacket. Finally, the material is separated from the gas and solid with the airflow.

[0085] In a second aspect, the present invention provides an application of the biomass impurity removal method in the preparation of bio-carbon powder.

[0086] In the present invention, the biomass impurity removal method can efficiently remove impurities in biomass on a large scale with high efficiency, low cost, and not only removes surface dust in the biomass, but also removes the internal ash of the biomass. The impurity removal efficiency is high, and the quality of the baked biocarbon powder is improved.

[0087] In a third aspect, the present invention provides a method for preparing bio-carbon powder, the method comprising the following steps:

[0088] The biomass powder after impurities are removed by the biomass impurity removal method is baked to obtain bio-carbon powder.

[0089] Further, the baking temperature is 200-220°C, for example, 200°C, 210°C, 220°C, etc., the baking time is 20-30min, for example, 20min, 22min, 24min, 26min, 28min, 30min, and the heating rate is 20°C / min;

[0090] Preferably, the heat source for baking is one of water vapor, hot flue gas and inert gas.

[0091] In the present invention, the impurities at the front end of biomass baking are separated by multi-stage impurity removal, and finally the bio-carbon powder with high calorific value is obtained by baking, the energy is more concentrated, and the energy yield is high. Specifically, the present invention removes impurities from the biomass after crushing, and removes impurities that affect the quality of the biomass carbon powder in the biomass in a coordinated manner using a variety of impurity removal methods, and then converts the biomass into high calorific value and high-quality bio-carbon powder by low-temperature baking. The impurity removal method of the present invention not only removes the external ash (dust) on the surface of the biomass, but also removes the internal ash (inorganic salts) in the biomass at the same time, and has high impurity removal efficiency, which improves the quality of the bio-carbon powder after baking, and the bio-carbon powder is convenient for storage and transportation, enriches the back-end processing process route, and realizes the reduction, harmlessness and resource treatment of domestic waste.

[0092] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0093] Example 1

[0094] This embodiment provides a biomass impurity removal method, comprising the following steps:

[0095] Step 1: Crushing: the biomass to be cleaned is transported to the coarse crusher for the first crushing. The width of the blade used for the first crushing is 10 mm, the number of blades is 4 groups, the speed of the moving blade is 2800 r / min, and the particle size of the biomass powder obtained after the first crushing is 20-100 mm;

[0096] The biomass after the first crushing is transported to the vertical crusher for the second crushing. The blade width used for the second crushing is 4mm, the number of blades is 6 groups, the rotating speed of the moving blade is 2800r / min, and the particle size of the biomass powder obtained after the second crushing is 5-10mm; the biomass powder after the second crushing is sucked into the fluidized bed sorting device from the outlet at the upper end of the crushing chamber by the fan, while the particles with relatively large particle size are left in the lower layer due to gravity and continue to be crushed;

[0097] Step 2: Fluidized bed sorting, using fluidized medium to suspend the light matter (i.e., light organic matter) in the biomass powder, and using fluidized bed to put the heavy matter (including sand and metal) in the biomass powder in a non-fluidized state, and the light matter is sorted and transported to the next dust removal process through the fluidized bed, while removing the heavy matter;

[0098] The fluidizing medium is air at room temperature, and the air volume and air pressure entering the fluidized bed are adjusted by the control valve. The initial fluidizing velocity is 4.5 cm / s, the fluidizing air inlet temperature is 170°C, and the air pressure is 0.05 MPa. The biomass powder separated from the fluidized bed enters the cyclone dust collector.

[0099] Step 3: Dust removal: a cyclone dust collector is used for primary and secondary dust removal. The ratio of the cylinder diameter of the cyclone dust collector to the exhaust pipe diameter is 3. The two-stage cyclone dust collector is provided with two cyclone separation units, and the two groups have the same specifications and sizes. During cyclone dust removal, the inlet air flow velocity of the primary dust removal is 20m / s and the temperature is 130°C. The biomass powder after the primary dust removal enters the secondary dust removal process, and the inlet air flow velocity of the secondary dust removal is 16m / s and the temperature is 90°C.

[0100] Step 4: Magnetic separation: The biomass powder after dust removal is magnetically separated by a magnetic separator, with a cylinder diameter of 750 mm, a cylinder speed of 40 r / min, a magnetic declination of 20 degrees, and a magnetic field strength of 3500 Gauss;

[0101] Step 5: Washing with water, soaking, stirring and washing the biomass powder after magnetic separation in sequence;

[0102] The water used for washing was at a temperature of 60°C, a pH of 7, a soaking time of 50 minutes, stirring for 30 minutes, and rinsing;

[0103] Step 6: Drying: using a cyclone separator to perform cyclone separation on the washed biomass powder to achieve the purpose of liquid-solid separation, and then using a cyclone dryer to dry the biomass powder to obtain dry biomass powder;

[0104] Among them, the water inlet pressure of the cyclone separator during solid-liquid separation treatment is 0.8Mpa, the pressure loss of the cyclone separator is 0.032Mpa, and during cyclone drying, the inlet air temperature is 150°C and the exhaust air temperature is 70°C.

[0105] Example 2

[0106] This embodiment provides a biomass impurity removal method, comprising the following steps:

[0107] Step 1: Crushing: the biomass to be cleaned is transported to the coarse crusher for the first crushing. The width of the blade used for the first crushing is 14 mm, the number of blades is 2 sets, the speed of the moving blade is 3000 r / min, and the particle size of the biomass powder obtained after the first crushing is 20-100 mm;

[0108] The biomass after the first crushing is transported to the vertical crusher for the second crushing. The blade width used for the second crushing is 6mm, the number of blades is 4 groups, the rotating speed of the moving blade is 3000r / min, and the particle size of the biomass powder obtained after the second crushing is 5-10mm; the biomass powder after the second crushing is sucked into the fluidized bed sorting device from the outlet at the upper end of the crushing chamber by the fan, while the particles with relatively large particle size are left in the lower layer due to gravity and continue to be crushed;

[0109] Step 2: Fluidized bed sorting, using fluidized medium to suspend the light matter (i.e., light organic matter) in the biomass powder, and using fluidized bed to put the heavy matter (including sand and metal) in the biomass powder in a non-fluidized state, and the light matter is sorted and transported to the next dust removal process through the fluidized bed, while removing the heavy matter;

[0110] The fluidizing medium is air at room temperature, and the air volume and air pressure entering the fluidized bed are adjusted by the control valve. The initial fluidizing velocity is 6.5 cm / s, the fluidizing air inlet temperature is 160°C, and the air pressure is 0.2 MPa. The biomass powder separated from the fluidized bed enters the cyclone dust collector.

[0111] Step 3: Dust removal: a cyclone dust collector is used for primary and secondary dust removal. The ratio of the cylinder diameter of the cyclone dust collector to the exhaust pipe diameter is 2. The two-stage cyclone dust collector is provided with two cyclone separation units, and the two groups have the same specifications and sizes. During cyclone dust removal, the inlet air flow velocity of the primary dust removal is 25m / s and the temperature is 120°C. The biomass powder after the primary dust removal enters the secondary dust removal process, and the inlet air flow velocity of the secondary dust removal is 20m / s and the temperature is 80°C.

[0112] Step 4: Magnetic separation: The biomass powder after dust removal is magnetically separated by a magnetic separator, with a cylinder diameter of 750 mm, a cylinder speed of 30 r / min, a magnetic declination of 15 degrees, and a magnetic field strength of 500 Gauss;

[0113] Step 5: Washing with water, soaking, stirring and washing the biomass powder after magnetic separation in sequence;

[0114] The water used for washing was at a temperature of 80°C, a pH of 6, a soaking time of 60 minutes, stirring for 20 minutes, and then rinsing;

[0115] Step 6: Drying: using a cyclone separator to perform cyclone separation on the washed biomass powder to achieve the purpose of liquid-solid separation, and then using a cyclone dryer to dry the biomass powder to obtain dry biomass powder;

[0116] Among them, the water inlet pressure of the cyclone separator during solid-liquid separation treatment is 0.8Mpa, the pressure loss of the cyclone separator is 0.028Mpa, and during cyclone drying, the inlet air temperature is 100°C and the exhaust air temperature is 50°C.

[0117] Example 3

[0118] This embodiment provides a biomass impurity removal method, comprising the following steps:

[0119] Step 1: Crushing: the biomass to be cleaned is transported to the coarse crusher for the first crushing. The width of the blade used for the first crushing is 12 mm, the number of blades is 3 groups, the speed of the moving blade is 2960 r / min, and the particle size of the biomass powder obtained after the first crushing is 20-100 mm;

[0120] The biomass after the first crushing is transported to the vertical crusher for the second crushing. The blade width used for the second crushing is 5mm, the number of blades is 5 groups, the rotating speed of the moving blade is 2890r / min, and the particle size of the biomass powder obtained after the second crushing is 5-10mm; the biomass powder after the second crushing is sucked into the fluidized bed sorting device from the outlet at the upper end of the crushing chamber by the fan, while the particles with relatively large particle size are left in the lower layer due to gravity and continue to be crushed;

[0121] Step 2: Fluidized bed sorting, using fluidized medium to suspend the light matter (i.e., light organic matter) in the biomass powder, and using fluidized bed to put the heavy matter (including sand and metal) in the biomass powder in a non-fluidized state, and the light matter is sorted and transported to the next dust removal process through the fluidized bed, while removing the heavy matter;

[0122] The fluidizing medium is air at room temperature, and the air volume and air pressure entering the fluidized bed are adjusted by the control valve. The initial fluidizing velocity is 5.5 cm / s, the fluidizing air inlet temperature is 165°C, and the air pressure is 0.1 MPa. The biomass powder separated from the fluidized bed enters the cyclone dust collector.

[0123] Step 3: Dust removal: a cyclone dust collector is used for primary and secondary dust removal. The ratio of the cylinder diameter of the cyclone dust collector to the exhaust pipe diameter is 2.5. The two-stage cyclone dust collector is provided with two cyclone separation units, and the two groups have the same specifications and sizes. During cyclone dust removal, the inlet air flow velocity of the primary dust removal is 23m / s and the temperature is 125°C. The biomass powder after the primary dust removal enters the secondary dust removal process, and the inlet air flow velocity of the secondary dust removal is 18m / s and the temperature is 85°C.

[0124] Step 4: Magnetic separation: The biomass powder after dust removal is magnetically separated by a magnetic separator, with a cylinder diameter of 750 mm, a cylinder speed of 36 r / min, a magnetic declination of 18 degrees, and a magnetic field strength of 2000 Gauss;

[0125] Step 5: Washing with water, soaking, stirring and washing the biomass powder after magnetic separation in sequence;

[0126] The water used for washing was 70°C, pH 6.5, soaking time was 55 min, stirring was 35 min, and then rinsing was performed;

[0127] Step 6: Drying: using a cyclone separator to perform cyclone separation on the washed biomass powder to achieve the purpose of liquid-solid separation, and then using a cyclone dryer to dry the biomass powder to obtain dry biomass powder;

[0128] Among them, the water inlet pressure of the cyclone separator during solid-liquid separation treatment is 0.8Mpa, the pressure loss of the cyclone separator is 0.03Mpa, and during cyclone drying, the inlet air temperature is 125°C and the exhaust air temperature is 60°C.

[0129] Example 4

[0130] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in Step 3, the inlet air flow velocity of the first-stage dust removal is 19 m / s, and the remaining steps are consistent with Embodiment 3.

[0131] Example 5

[0132] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in step 3, the inlet air flow velocity of the first-stage dust removal is 26 m / s, and the remaining steps are consistent with Embodiment 3.

[0133] Example 6

[0134] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in Step 3, the inlet air flow velocity of the secondary dust removal is 15 m / s, and the remaining steps are consistent with Embodiment 3.

[0135] Example 7

[0136] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in step 3, the inlet air flow velocity of the secondary dust removal is 21 m / s, and the remaining steps are consistent with Embodiment 3.

[0137] Example 8

[0138] This embodiment provides a biomass impurity removal method, which is different from Embodiment 3 in that in step 1, no second crushing is performed, and the remaining steps are consistent with Embodiment 3.

[0139] Example 9

[0140] This embodiment provides a biomass impurity removal method, which is different from Embodiment 3 in that in step 3, no secondary dust removal is performed, and the remaining steps are consistent with Embodiment 3.

[0141] Example 10

[0142] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in step 3, an electrostatic field is set in the channel between the primary dust removal and the secondary dust removal, the electric field strength is 5 kv / cm, the effective residence time of the gas in the electric field is 6 s, and the remaining steps are consistent with Embodiment 3.

[0143] Embodiment 11

[0144] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in step 3, an electrostatic field is set in the channel between the primary dust removal and the secondary dust removal, the electric field strength is 20 kv / cm, and the effective residence time of the gas in the electric field is 4 s. The remaining steps are consistent with Embodiment 3.

[0145] Example 12

[0146] This embodiment provides a biomass impurity removal method, which differs from Embodiment 3 in that: in step 3, an electrostatic field is set in the channel between the primary dust removal and the secondary dust removal, the electric field strength is 12 kv / cm, and the effective residence time of the gas in the electric field is 5 s. The remaining steps are consistent with Embodiment 3.

[0147] Example 13

[0148] This embodiment provides a biomass impurity removal method, which differs from Embodiment 12 in that in step 3, an electrostatic field is set before the primary dust removal, and the remaining steps are consistent with Embodiment 12.

[0149] Embodiment 14

[0150] This embodiment provides a biomass impurity removal method, which differs from Embodiment 12 in that in step 3, an electrostatic field is set after the secondary dust removal, and the remaining steps are consistent with Embodiment 12.

[0151] Embodiment 15

[0152] This embodiment provides a method for preparing bio-carbon powder, comprising the following steps:

[0153] The biomass powder after impurities are removed by the biomass impurity removal method in Example 3 is baked to obtain bio-carbon powder;

[0154] The heat source for baking is inert gas, the baking temperature is 200°C, the baking time is 20 min, and the heating rate is 20°C / min.

[0155] Example 16

[0156] This embodiment provides a method for preparing bio-carbon powder, comprising the following steps:

[0157] The biomass powder after impurities are removed by the biomass impurity removal method in Example 3 is baked to obtain bio-carbon powder;

[0158] The heat source for baking is hot flue gas, the baking temperature is 220°C, the baking time is 30 minutes, and the heating rate is 20°C / min.

[0159] Examples 17-30

[0160] This embodiment provides a method for preparing bio-carbon powder, comprising the following steps:

[0161] The biomass powders after impurities are removed by the biomass impurity removal method in Examples 1-14 are baked in sequence to obtain the biocarbon powders of Examples 17-30;

[0162] The heat source for baking is water vapor, the baking temperature is 210°C, the baking time is 25 min, and the heating rate is 20°C / min.

[0163] Comparative Example 1

[0164] This comparative example provides a biomass impurity removal method, which is different from Example 3 in that step 2 is not performed, and the remaining steps are consistent with Example 3.

[0165] Comparative Example 2

[0166] This comparative example provides a biomass impurity removal method, which is different from Example 3 in that step 3 is not performed, and the remaining steps are consistent with Example 3.

[0167] Comparative Example 3

[0168] This comparative example provides a biomass impurity removal method, which is different from Example 3 in that step 5 is not performed, and the remaining steps are consistent with Example 3.

[0169] Comparative Example 4

[0170] This comparative example provides a biomass impurity removal method, which is different from Example 3 in that the order of step 2 and step 3 is reversed, that is, dust removal is performed first, and then fluidized bed separation is performed, and the remaining steps are consistent with Example 3.

[0171] Comparative Example 5

[0172] This comparative example provides a biomass impurity removal method, which is different from Example 3 in that the order of steps 1 and 2 is reversed, that is, fluidized bed sorting is performed first, and then crushing is performed, and the remaining steps are consistent with Example 3.

[0173] Comparative Examples 6-10

[0174] This comparative example provides a method for preparing biochar powder, which differs from Example 19 in that the biomass powders removed by the biomass impurity removal method in Comparative Examples 1-5 are baked in sequence to obtain the biochar powders of Comparative Examples 1-5, and the remaining steps are consistent with Example 19.

[0175] Test Case

[0176] Test samples: the bio-carbon powders prepared in Examples 15-30 and the bio-carbon powders prepared in Comparative Examples 6-10.

[0177] Test method: The test is based on GB / T30727-2014 solid biomass fuel calorific value determination method.

[0178] The test results are shown in Table 1.

[0179] Table 1

[0180]

[0181]

[0182] It can be seen from Table 1 that the biomass impurity removal method provided by the embodiment of the present invention has a better impurity removal effect, so the calorific value of the biological carbon powder obtained by baking is higher, which improves the quality of the biological carbon powder after baking.

[0183] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biomass impurity removal method, characterized in that: The biomass impurity removal method comprises the following steps: The biomass is sequentially crushed, fluidized bed sorted, dusted, magnetically separated, washed and dried to obtain the impurity-free biomass powder.

2. The biomass impurity removal method according to claim 1, characterized in that: The crushing includes first crushing and second crushing in sequence; Preferably, the particle size of the biomass powder obtained after the first crushing is 20-100 mm, and the particle size of the biomass powder obtained after the second crushing is 5-10 mm; Preferably, the width of the blade used for the first crushing is 10-14 mm, the number of blades is 2-4 groups, each group of blades includes a moving blade and a stationary blade arranged at intervals, and the rotation speed of the moving blade is 2800-3000 r / min; Preferably, the width of the blade used for the second crushing is 4-6 mm, the number of blades is 4-6 groups, each group of blades includes a moving blade and a stationary blade arranged at intervals, and the rotation speed of the moving blade is 2800-3000 r / min; Preferably, the first crushing adopts a coarse crusher, and the second crushing adopts a vertical crusher.

3. The biomass impurity removal method according to claim 1, characterized in that: The fluidized bed separation includes: using a fluidized medium to suspend light matter in the biomass powder, using a fluidized bed to put heavy matter in the biomass powder in a non-fluidized state, and transporting the light matter to the dust removal process through the fluidized bed, and removing the heavy matter; Preferably, the heavy objects include sand and / or metal; Preferably, the fluidizing medium comprises air at room temperature, the fluidizing velocity is 4.5-6.5 cm / s, the air inlet temperature of the fluidizing medium is 160-170° C., and the wind pressure is 0.05-0.2 MPa.

4. The biomass impurity removal method according to claim 1, characterized in that: The dust removal includes primary dust removal and secondary dust removal in sequence, wherein the primary dust removal is used to remove large dust particles, and the secondary dust removal is used to remove sticky particles generated in the primary dust removal; Preferably, an electrostatic field is set after the primary dust removal and before the secondary dust removal so that the impurity particles are negatively charged and deposited at the anode; Preferably, the primary dust removal and the secondary dust removal use a cyclone dust collector, and the ratio of the barrel diameter of the cyclone dust collector to the exhaust pipe diameter is 2-3; Preferably, the inlet air flow velocity of the primary dust removal is 20-25 m / s and the temperature is 120-130°C; Preferably, the inlet air flow velocity of the secondary dust removal is 16-20 m / s and the temperature is 80-90°C.

5. The biomass impurity removal method according to claim 1, characterized in that: The magnetic separation is used to remove iron-containing substances in biomass powder; Preferably, a magnetic separator is used to carry out the magnetic separation process; Preferably, the rotation speed of the cylinder used for the magnetic separation is 30-40 r / min, the magnetic deflection angle of the magnetic separation is 15-20 degrees, and the magnetic field strength is 500 Gauss-3500 Gauss.

6. The biomass impurity removal method according to claim 1, characterized in that: The water washing includes soaking and stirring the biomass powder in sequence, dissolving the inorganic salts in the internal structure of the biomass in water through the water washing, thereby removing the inorganic salts; Preferably, the water used for washing has a temperature of 60-80°C and a pH of 6-7; Preferably, the soaking time is 50-60 min; Preferably, the stirring time is 20-30 min.

7. The biomass impurity removal method according to claim 1, characterized in that: The drying includes performing solid-liquid separation on the washed biomass powder, and then drying the solid material to obtain dry biomass powder; Preferably, a hydrocyclone separator is used for the solid-liquid separation process, and a cyclone dryer is used for the drying process; Preferably, during the solid-liquid separation process, the water inlet pressure of the hydrocyclone is greater than 0.4 MPa, and the pressure loss of the hydrocyclone is 0.028-0.032 MPa. Preferably, the inlet air temperature of the drying process is 100-150°C, and the exhaust air temperature is 50-70°C.

8. Use of the biomass impurity removal method according to any one of claims 1 to 7 in the preparation of bio-carbon powder.

9. A method for preparing bio-carbon powder, characterized in that: The method for preparing bio-carbon powder comprises the following steps: The biomass powder after impurities are removed by the biomass impurity removal method according to any one of claims 1 to 8 is baked to obtain bio-carbon powder.

10. The method for preparing bio-carbon powder according to claim 9, characterized in that: The baking temperature is 200-220°C, the baking time is 20-30min, and the heating rate is 20°C / min; Preferably, the heat source for baking is one of water vapor, hot flue gas and inert gas.

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