A method and device for selectively removing alkali from biomass pyrolysis carbon based on alkali occurrence form regulation

Abstract

The present application belongs to the technical field of biomass energy conversion and green carbon granulation, and discloses a method and device for selectively removing alkali from pyrolysis carbon based on alkali metal occurrence form regulation. The present application is based on the occurrence form analysis of representative pyrolysis carbon samples, the initial K+Na content, and the required comprehensive removal rate of w(K)+w(Na)≤0.25% in the mixture of target dealkalization pyrolysis carbon and coal injection, and selects the dealkalization mode between the dilute washing of bio-oil water phase and the dilute acid washing of bio-oil water phase. The present application can match the raw material type, pyrolysis temperature, occurrence form and washing strength, so as to consider the deep dealkalization, fixed carbon retention and calorific value retention. Further, the present application introduces auxiliary granulation forming, which can improve the bulk density, particle mechanical strength, wear resistance and transportation stability of low-migration alkali metal biochar, and reduce the risk of powder dusting, which is beneficial to the engineering application of blast furnace injection, sintering fuel and metallurgical reducing agent.

Description

Technical Field

[0001] This invention relates to the field of biochar pellet forming and biomass energy technology, and in particular to a method and apparatus for selective dealkali removal from biomass pyrolysis char based on the regulation of alkali metal occurrence. Background Technology

[0002] Biomass pyrolysis char is renewable, has a high fixed carbon content, and offers carbon reduction potential, making it a potential partial substitute for metallurgical coal, blast furnace pulverized coal, sintering fuel, or metallurgical reducing agents. Agricultural and forestry biomass is widely available, and the particle size, volatile matter, ash content, and reactivity of the solid char products formed after pyrolysis can be adjusted through pyrolysis temperature and post-processing. However, biomass and its pyrolysis char often contain high proportions of alkali metals and alkaline earth metals such as K, Na, Ca, and Mg. K and Na are particularly prone to migration, volatilization, molten salt formation, or catalytic reactions, which can lead to slagging, ash accumulation, corrosion, furnace lining erosion, coke deterioration, and furnace condition fluctuations.

[0003] Existing water-washing, inorganic acid washing, organic acid washing, or bio-oil acid washing programs mostly use total alkali metal removal rate and total ash reduction rate as the main evaluation indicators, and often employ fixed washing processes or fixed washing intensities. This type of evaluation method does not adequately differentiate the migration and hazardousness of alkali metals in different occurrence forms. Water-soluble and exchangeable K / Na are more likely to migrate and participate in the formation of low-melting-point salts during combustion, gasification, pyrolysis, or metallurgical applications, while acid-soluble and insoluble forms are relatively stable. Continuing to intensify acid washing has limited contribution to reducing the risk of easy migration and may even cause fixed carbon and calorific value loss.

[0004] Therefore, there is an urgent need for a process that differs from fixed water washing, fixed acid washing, or simple bio-oil acid washing. This process can perform speciation analysis on representative pyrolytic carbon samples before selective dealkali removal, thereby determining the dealkali removal mode and immersion parameters between bio-oil aqueous phase dilution washing and bio-oil aqueous phase dilution plus acid washing, avoiding unnecessary water washing pretreatment and excessive acid washing.

[0005] In addition, biomass pyrolysis char after dealkali removal is usually in powder or fine particle form, which can easily cause problems such as dust, low bulk density, poor flowability and insufficient mechanical stability during storage, transportation, metering and metallurgical fuel utilization. Summary of the Invention

[0006] The purpose of this invention is to provide a selective alkali removal method and apparatus for biomass pyrolysis char based on the regulation of alkali metal occurrence. By analyzing the water-soluble, exchangeable, acid-soluble, and insoluble distribution of K, Na, Ca, and Mg in representative samples of pyrolysis char before selective alkali removal, water-soluble and exchangeable K / Na are defined as easily migratable K / Na. With the target of w(K)+w(Na)≤0.25% after mixing pyrolysis char with pulverized coal, the bio-oil aqueous phase dilution washing or acid washing is selected according to the initial K+Na content and the required comprehensive removal rate, to preferentially remove easily migratable K / Na, while reducing fixed carbon loss, calorific value loss, and unnecessary process extension.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for selective dealkali removal from biomass pyrolysis char based on the regulation of alkali metal occurrence, comprising the following steps: S1. Pyrolyze biomass raw materials to obtain pyrolytic char and bio-oil; S2. The pyrolytic carbon is subjected to speciation analysis. The elements analyzed include K, Na, Ca and Mg. The contents of water-soluble, exchangeable, acid-soluble and insoluble states of each element are obtained. The sum of the contents of water-soluble and exchangeable states is defined as the easily migratable state. S3. Selectively impregnate the pyrolytic carbon; S4. The selectively washed liquid is sequentially subjected to solid-liquid separation, washing, and drying to obtain dealkalized pyrolytic carbon. S5. Evaluate the dealkali removal effect of the dealkali pyrolysis char to obtain low-migration alkali metal biochar. Specifically, the selective rinsing method described in step S3 includes: S3.1 Based on the sum of K and Na contents in the pyrolysis char and the mixing ratio of the dealkali pyrolysis char and pulverized coal, calculate the comprehensive removal rate required for the pyrolysis char when the sum of K and Na contents in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%. The calculation method is shown in Formulas 1 to 3: w 混 =(1-x)×w 煤 +x×w 炭 Formula 1, When w 混 When ≤0.25%, w 炭max =[0.25%-(1-x)×w 煤 ]÷x formula 2, η=[w 炭初始 -w 炭max ]÷w 炭初始 ×100% Formula 3, In formulas 1~3, w 混The sum of K and Na contents in the mixture of dealkali pyrolysis carbon and pulverized coal is given by denomination x, where x is the blending ratio of dealkali pyrolysis carbon in the mixture of dealkali pyrolysis carbon and pulverized coal, and x ranges from 1 to 35 wt%. 煤 w is the sum of the K and Na contents in the pulverized coal. 炭 w is the sum of the K and Na contents in the dealkali pyrolysis char. 炭max η represents the maximum sum of K and Na content in the pyrolysis carbon at a blending amount of x, where η is the required overall removal rate of the pyrolysis carbon at a blending amount of x, and w is the maximum sum of K and Na content in the pyrolysis carbon. 炭初始 This is the sum of the K and Na contents in the pyrolytic char; S3.2 When the overall removal rate is <80%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase; when the overall removal rate is >85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase and acid; when the overall removal rate is 80~85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase or diluted and washed with bio-oil aqueous phase and acid. The selective immersion conditions described in step S3 include: pyrolytic carbon particle size of 1-5 mm, solid-liquid mass ratio of 1:3-1:20, bio-oil-water phase to water mass ratio of 1:5-20, immersion solution pH of 2-5.5, immersion temperature of 15-80℃, immersion time of 0.5-4 h, and stirring rate of 20-300 r / min. The evaluation method described in step S5 specifically includes four evaluation indicators: the sum of K and Na content in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%; the removal rate of easily migratable K or Na after dealkali removal is ≥90%; the fixed carbon retention rate of dealkali pyrolysis char is ≥95%; and the calorific value retention rate of dealkali pyrolysis char is ≥95%. Low-migratory alkali metal biochar must simultaneously meet at least three of the evaluation indicators.

[0008] Furthermore, in the method, the biomass raw materials in step S1 include one or more of pine wood, corn stalks, rice stalks, cotton stalks, bamboo, other forestry residues, and other crop straws; The pyrolysis temperature in step S1 is 300~600℃.

[0009] Furthermore, in the method, the method for analyzing the occurrence speciation in step S2 specifically includes: sequential extraction of pyrolytic carbon, obtaining the water-soluble content by water extraction, obtaining the exchangeable content by ammonium acetate solution extraction, obtaining the acid-soluble content by acid solution extraction, and obtaining the insoluble content by subtracting the water-soluble content, exchangeable content and acid-soluble content from the total content. The total content is determined by ICP-OES, ICP-MS, flame photometry or atomic absorption spectrometry after digestion.

[0010] Furthermore, in the method, the bio-oil aqueous phase in step S3.2, either the bio-oil aqueous phase dilution wash or the bio-oil aqueous phase dilution and acid wash, is the aqueous phase obtained by allowing the bio-oil obtained in step S1 to stand and separate into layers; the acid in the bio-oil aqueous phase dilution and acid wash in step S3.2 includes one or more of formic acid, acetic acid, propionic acid, glycolic acid, citric acid, oxalic acid, and hydrochloric acid.

[0011] Furthermore, in the method, the conditions for the bio-oil aqueous phase dilution washing in step S3.2 include: pyrolytic carbon particle size of 1~5mm, solid-liquid mass ratio of 1:3~1:20, bio-oil aqueous phase to water mass ratio of 1:5~20, washing solution pH of 3.5~5.5, immersion temperature of 15~80℃, immersion time of 0.5~3h, and stirring rate of 40~150r / min; The conditions for diluting and acid washing the bio-oil aqueous phase in step S3.2 include: pyrolytic carbon particle size of 1-5 mm, solid-liquid mass ratio of 1:3-1:20, bio-oil aqueous phase to water mass ratio of 1:5-20, washing solution pH of 2-3.5, immersion temperature of 15-80℃, immersion time of 1-4 h, and stirring rate of 40-150 r / min.

[0012] Furthermore, in the method, the low-migration alkali metal biochar in step S5 also includes post-processing, specifically including: sequentially crushing, sieving, mixing and humidifying, granulating and drying to obtain low-migration alkali metal biochar particles.

[0013] The present invention also provides an apparatus for a selective dealkali removal method of biomass pyrolysis char based on the regulation of alkali metal occurrence speciation. The apparatus includes a pyrolysis char storage and feeding unit, a bio-oil aqueous phase dilution / acid addition preparation unit, a selective immersion reaction unit, a solid-liquid separation unit, a drying unit, a sampling and occurrence speciation analysis unit, and a process execution control unit. The pyrolysis char storage and feeding unit, the bio-oil aqueous phase dilution / acid addition preparation unit, the selective immersion reaction unit, the solid-liquid separation unit, and the drying unit are sequentially connected. The sampling and morphological analysis unit is electrically connected to the process execution control unit for transmitting the morphological analysis result signal. The process execution control unit is electrically connected to the bio-oil aqueous phase dilution / acidification preparation unit, the selective immersion reaction unit, and the drying unit for transmitting control signals.

[0014] Furthermore, in the device, the bio-oil aqueous phase dilution / acidification preparation unit includes a bio-oil aqueous phase tank, a water tank, an acid preparation tank, a metering pump, and a stirrer.

[0015] Furthermore, in the device, the solid-liquid separation unit is connected to the wastewater treatment unit; And / or, the selective immersion reaction unit is connected to the wastewater treatment unit; The wastewater treatment unit includes one or more of the following: neutralization tank, sedimentation tank, filter, adsorption unit, and evaporation concentration unit.

[0016] Furthermore, in the device, the drying unit is connected to the granulation and forming unit; The granulation unit includes a carbon powder storage and metering unit, a binder preparation unit, a mixing and humidity conditioning unit, a granulation unit, a drying and cooling unit, and a screening unit connected in sequence.

[0017] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1. This invention focuses on the easily migrating state composed of water-soluble and exchangeable K / Na as the main control target, which can change the dealkali removal target from the total amount reduction to the selective removal of highly migrating and highly hazardous components; 2. This invention does not simply perform water washing, acid washing, or bio-oil acid washing, nor does it simply reduce the total amount of alkali metals. Instead, it selects the dealkali removal mode between bio-oil aqueous phase dilution washing and bio-oil aqueous phase dilution plus acid washing based on the occurrence speciation analysis of representative pyrolysis carbon samples, the initial K+Na content, and the comprehensive removal rate required for w(K)+w(Na)≤0.25% in the target dealkali removal pyrolysis carbon and pulverized coal mixture. Furthermore, it determines the composition of the washing solution, the solid-liquid ratio, the immersion temperature, and the immersion time, so as to match the raw material type, pyrolysis temperature, occurrence speciation, and washing intensity, thereby taking into account deep dealkali removal, fixed carbon retention, and calorific value retention. 3. This invention does not require water washing pretreatment as a necessary step, which can shorten the process flow, and the soaking time, temperature, washing solution ratio and solid-liquid ratio can be determined through pre-experimentation; 4. This invention can utilize the bio-oil aqueous phase produced as a byproduct of the pyrolysis process as a source of acidic washing solution, and add a small amount of acid when deep dealkalization is required; 5. This invention uses w(K)+w(Na)≤0.25% in the fuel after blending dealkali pyrolysis carbon with pulverized coal, removal rate of easily migratable K / Na, retention rate of fixed carbon and retention rate of calorific value as comprehensive evaluation indicators, and is applicable to batch, semi-continuous or continuous operation. 6. This invention introduces a low-ash, low-alkali, low-sulfur, and low-chlorine binder to assist in granulation after selective dealkalization, further preparing low-migration alkali metal biochar into biochar particles with certain mechanical strength and particle size stability. This can improve the bulk density, particle mechanical strength, wear resistance, and transportation stability of low-migration alkali metal biochar, and reduce the risk of powder dust. It is beneficial for engineering applications such as blast furnace injection, sintering fuel, and metallurgical reducing agent, and improves its engineering application adaptability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0019] Figure 1 A schematic diagram of the process flow for selective alkali removal from biomass pyrolysis char; Figure 2 A schematic diagram of the apparatus used in the selective dealkali removal method for biomass pyrolysis char; Figure 3 The influence of different unpyrolyzed biomass on the occurrence speciation of alkali metals / alkaline earth metals; Figure 4 The changes in the occurrence and speciation of corn char at different pyrolysis temperatures; Figure 5 The changes in the occurrence and speciation of rice char at different pyrolysis temperatures; Figure 6 The changes in the occurrence and morphology of cotton char at different pyrolysis temperatures; Figure 7 Examples 1-3 show the changes in the morphology of corn straw charcoal pyrolyzed at 450℃ under different immersion times; Figure 8 Examples 4-7 show the removal rates of alkali metals / alkaline earth metals from corn straw charcoal pyrolyzed at 450°C under different immersion temperatures; Figure 9 The residual alkali metal / alkaline earth metal content of corn straw charcoal pyrolyzed at 450°C under different immersion solutions is used in Example 2 and Comparative Example 1. Detailed Implementation

[0020] This invention provides a method for selective dealkali removal from biomass pyrolysis char based on the regulation of alkali metal occurrence, comprising the following steps: S1. Pyrolyze biomass raw materials to obtain pyrolytic char and bio-oil; S2. The pyrolytic carbon is subjected to speciation analysis. The elements analyzed include K, Na, Ca and Mg. The contents of water-soluble, exchangeable, acid-soluble and insoluble states of each element are obtained. The sum of the contents of water-soluble and exchangeable states is defined as the easily migratable state. S3. Selectively impregnate the pyrolytic carbon; S4. The selectively washed liquid is sequentially subjected to solid-liquid separation, washing, and drying to obtain dealkalized pyrolytic carbon. S5. Evaluate the dealkali removal effect of the dealkali pyrolysis char to obtain low-migration alkali metal biochar. Specifically, the selective rinsing method described in step S3 includes: S3.1 Based on the sum of K and Na contents in the pyrolysis char and the mixing ratio of the dealkali pyrolysis char and pulverized coal, calculate the comprehensive removal rate required for the pyrolysis char when the sum of K and Na contents in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%. The calculation method is shown in Formulas 1 to 3: w 混 =(1-x)×w 煤 +x×w 炭 Formula 1, When w 混 When ≤0.25%, w 炭max =[0.25%-(1-x)×w 煤 ]÷x formula 2, η=[w 炭初始 -w 炭max ]÷w 炭初始 ×100% Formula 3, In formulas 1~3, w 混 The sum of K and Na contents in the mixture of dealkali pyrolysis carbon and pulverized coal is given by denomination x, where x is the blending ratio of dealkali pyrolysis carbon in the mixture of dealkali pyrolysis carbon and pulverized coal, and x ranges from 1 to 35 wt%. 煤 w is the sum of the K and Na contents in the pulverized coal. 炭 w is the sum of the K and Na contents in the dealkali pyrolysis char. 炭max η represents the maximum sum of K and Na content in the pyrolysis carbon at a blending amount of x, where η is the required overall removal rate of the pyrolysis carbon at a blending amount of x, and w is the maximum sum of K and Na content in the pyrolysis carbon. 炭初始 This is the sum of the K and Na contents in the pyrolytic char; S3.2 When the overall removal rate is <80%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase; when the overall removal rate is >85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase and acid; when the overall removal rate is 80~85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase or diluted and washed with bio-oil aqueous phase and acid. The selective immersion conditions described in step S3 include: pyrolytic carbon particle size of 1-5 mm, solid-liquid mass ratio of 1:3-1:20, bio-oil-water phase to water mass ratio of 1:5-20, immersion solution pH of 2-5.5, immersion temperature of 15-80℃, immersion time of 0.5-4 h, and stirring rate of 20-300 r / min. The evaluation method described in step S5 specifically includes four evaluation indicators: the sum of K and Na content in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%; the removal rate of easily migratable K or Na after dealkali removal is ≥90%; the fixed carbon retention rate of dealkali pyrolysis char is ≥95%; and the calorific value retention rate of dealkali pyrolysis char is ≥95%. Low-migratory alkali metal biochar must simultaneously meet at least three of the evaluation indicators.

[0021] In this invention, the biomass raw materials mentioned in step S1 preferably include one or more of the following: pine wood, corn stalks, rice stalks, cotton stalks, bamboo, other forestry residues, and other crop straws. No specific preference is made for the type of biomass raw material; the embodiments only use corn stalks, rice stalks, and cotton stalks as examples for illustration.

[0022] In this invention, the pyrolysis temperature in step S1 is preferably 300~600℃, more preferably 400~500℃, and even more preferably 450℃. The pyrolysis time is not limited; any method well-known in the art can be used. Specifically, for biomass raw materials such as corn stalks, rice stalks, and cotton stalks, a pyrolysis time of 20~60 minutes is used.

[0023] In this invention, the bio-oil mentioned in step S1 refers to the liquid product obtained by condensing the volatile products of biomass pyrolysis; the condensation temperature is preferably 10~60℃, more preferably 10~30℃, and even more preferably 20℃.

[0024] In this invention, the method for analyzing the occurrence speciation in step S2 specifically includes: sequential extraction of pyrolytic carbon, obtaining the water-soluble content by water extraction, obtaining the exchangeable content by ammonium acetate solution extraction, obtaining the acid-soluble content by acid solution extraction, and obtaining the insoluble content by subtracting the water-soluble content, exchangeable content and acid-soluble content from the total content. The total content is determined by ICP-OES, ICP-MS, flame photometry or atomic absorption spectrometry after digestion. The acid solution includes hydrochloric acid solution; The concentrations of the ammonium acetate solution and the acid solution are not limited, and any solution well known in the art can be used; in the specific implementation example, 1 mol / L is used.

[0025] In this invention, in the occurrence morphology analysis described in step S2, the water-soluble state refers to the alkali metal or alkaline earth metal form that can be extracted by leaching with water or deionized water; the exchangeable state refers to the form that can be extracted by leaching with neutral salt solutions such as ammonium acetate; the acid-soluble state refers to carbonates, oxides, partially organic-bound states, or mineral-bound states that can be extracted by leaching with acidic solutions such as hydrochloric acid; and the insoluble state refers to the residual form after deducting the above three forms from the total content.

[0026] In this invention, in step S3.1, the value of x is preferably 15~30wt%, and more preferably 25wt%.

[0027] In this invention, the bio-oil aqueous phase in step S3.2, either the bio-oil aqueous phase dilution wash or the bio-oil aqueous phase dilution plus acid wash, is preferably the aqueous phase obtained by allowing the bio-oil obtained in step S1 to stand and separate into layers; the aqueous phase is rich in water and water-soluble oxygen-containing organic matter; The ambient temperature for the static stratification is preferably 4~25℃, more preferably 15~25℃, and even more preferably 20℃; the static time is preferably 6~24h, more preferably 12~24h, and even more preferably 24h. Optionally, after settling and stratification, the mixture is sequentially centrifuged and filtered to remove coke powder, heavy tar, or suspended particles. The centrifugation speed is preferably 3000-8000 r / min, more preferably 4000-6000 r / min, and even more preferably 5000 r / min; the centrifugation time is preferably 20-60 min, more preferably 30-50 min, and even more preferably 40 min. The filter pore size is preferably 0.45-5 μm, more preferably 0.45-2 μm, and even more preferably 0.45 μm.

[0028] The bio-oil aqueous phase contains one or more of the following: water, acetic acid, formic acid, propionic acid, glycolic acid, aldehydes, ketones, alcohols, and phenols.

[0029] The acid used in the aqueous phase dilution and acid washing of the bio-oil in step S3.2 preferably includes one or more of formic acid, acetic acid, propionic acid, glycolic acid, citric acid, oxalic acid, and hydrochloric acid, more preferably formic acid, acetic acid, propionic acid, glycolic acid, citric acid, oxalic acid, or hydrochloric acid, and even more preferably hydrochloric acid. The amount of acid used is not limited; it can be adjusted to the desired pH.

[0030] In this invention, the conditions for the bio-oil aqueous phase dilution washing in step S3.2 include: the pyrolytic carbon particle size is preferably 1-5 mm (obtained by crushing and sieving); the solid-liquid mass ratio is preferably 1:3-1:20, more preferably 1:5-1:15, and even more preferably 1:10; the mass ratio of bio-oil aqueous phase to water is preferably 1:5-20, more preferably 1:7-15, and even more preferably 1:10; the pH of the washing solution is preferably 3.5-5.5, more preferably 4-5, and even more preferably 4.5; the immersion temperature is preferably 15-80℃, more preferably 50-60℃, and even more preferably 50℃; the immersion time is preferably 0.5-3 h, more preferably 1-2 h, and even more preferably 1 h; the stirring rate is preferably 40-150 r / min, more preferably 80-120 r / min, and even more preferably 100 r / min.

[0031] In this invention, the conditions for diluting and acid washing the bio-oil aqueous phase in step S3.2 include: the pyrolytic carbon particle size is preferably 1-5 mm; the solid-liquid mass ratio is preferably 1:3-1:20, more preferably 1:5-1:15, and even more preferably 1:10; the mass ratio of the bio-oil aqueous phase to water is preferably 1:5-20, more preferably 1:7-10, and even more preferably 1:10; the pH of the washing solution is preferably 2-3.5, more preferably 2-3, and even more preferably 2.5; the immersion temperature is preferably 15-80℃, more preferably 70-80℃, and even more preferably 80℃; the immersion time is preferably 1-4 h, more preferably 2-3 h, and even more preferably 2 h; the stirring rate is preferably 40-150 r / min, more preferably 100-150 r / min, and even more preferably 150 r / min.

[0032] In this invention, the bio-oil aqueous phase dilution wash is used to gently remove water-soluble and exchangeable K / Na; the bio-oil aqueous phase dilution plus acid wash is used for deep removal of K / Na or to treat pyrolytic carbon that is difficult to meet the standards of bio-oil aqueous phase dilution wash.

[0033] In this invention, the selective rinsing described in step S3 is not required to be pretreated with water, multi-stage countercurrent, or washing liquid circulation.

[0034] In this invention, the immersion time, immersion temperature, washing solution ratio, solid-liquid ratio, and stirring rate in step S3.2, which involves diluting the bio-oil in aqueous phase or diluting the bio-oil in aqueous phase with acid, are determined by the analysis of the occurrence speciation of pyrolytic carbon, the initial K+Na content, the required comprehensive removal rate of w(K)+w(Na)≤0.25% in the target dealkali pyrolytic carbon and pulverized coal mixture, and the results of preliminary dealkali removal experiments. This is to avoid unnecessary process extension and excessive acid washing that could lead to loss of fixed carbon and calorific value.

[0035] In this invention, for pyrolytic carbon boundary samples requiring a comprehensive removal rate of 80-85% in step S3.2, the bio-oil aqueous phase dilution washing or bio-oil aqueous phase dilution plus acid washing is selected based on the occurrence speciation analysis and preliminary experimental results; that is, a preliminary experiment of bio-oil aqueous phase dilution washing is first carried out. If the target content cannot be removed, bio-oil aqueous phase dilution plus acid washing is required.

[0036] In this invention, the low-migration alkali metal biochar in step S5 also includes post-processing, specifically including: sequentially crushing, sieving, mixing and humidifying, granulating and drying to obtain low-migration alkali metal biochar particles.

[0037] In this invention, the crushing and sieving processes in the post-processing are not limited, and any solution well known in the art can be used.

[0038] In this invention, the preferred method for mixing and conditioning in the post-processing is to mix low-migration alkali metal biochar, molding binder, and water.

[0039] In this invention, the molding binder is preferably a low-ash, low-alkali-metal, low-sulfur, and low-chlorine binder, specifically including one or more of starch, modified starch, lignin, lignin sulfonate, carboxymethyl cellulose, polyvinyl alcohol, heavy components of bio-oil, and molasses. The specific type of molding binder is not limited; it can be selected according to requirements.

[0040] In this invention, the amount of the molding binder added is 1 to 20% of the dry basis mass of low-migration alkali metal biochar, more preferably 5 to 15%, and more preferably 10%.

[0041] In this invention, the moisture content of the material after mixing low-migration alkali metal biochar, molding binder and water is preferably 5-35%, more preferably 10-20%, and even more preferably 15%.

[0042] In this invention, the granulation molding specifically includes: in the mixed and conditioned material, the binder is uniformly dispersed on the surface and pore structure of the carbon powder particles; then the mixed material is fed into the molding equipment for molding.

[0043] In this invention, the molding equipment preferably includes one or more of the following: disc granulation, roller granulation, double roller extrusion granulation, screw extrusion granulation, or compression molding.

[0044] In this invention, the drying temperature is preferably 60~150℃, more preferably 80~120℃, and even more preferably 100℃.

[0045] In this invention, the particle size of the low-migration alkali metal biochar particles is preferably 1-5 mm. The water-soluble and exchangeable K / Na ratio in the biochar particles is reduced compared to un-alkali-removed pyrolysis carbon particles, while the fixed carbon and calorific value remain within the target range for metallurgical fuel use.

[0046] In this invention, the low-migration alkali metal biochar or the low-migration alkali metal biochar particles are preferably used in blast furnace injection fuel, sintering fuel, metallurgical reducing agent, solid fuel additive or carbon-based briquetted fuel.

[0047] The present invention also provides an apparatus for a selective dealkali removal method of biomass pyrolysis char based on the regulation of alkali metal occurrence speciation. The apparatus includes a pyrolysis char storage and feeding unit, a bio-oil aqueous phase dilution / acid addition preparation unit, a selective immersion reaction unit, a solid-liquid separation unit, a drying unit, a sampling and occurrence speciation analysis unit, and a process execution control unit. The pyrolysis char storage and feeding unit, the bio-oil aqueous phase dilution / acid addition preparation unit, the selective immersion reaction unit, the solid-liquid separation unit, and the drying unit are sequentially connected. The sampling and morphological analysis unit is electrically connected to the process execution control unit for transmitting the morphological analysis result signal. The process execution control unit is electrically connected to the bio-oil aqueous phase dilution / acidification preparation unit, the selective immersion reaction unit, and the drying unit for transmitting control signals.

[0048] In this invention, the sampling and speciation analysis unit is used to obtain the speciation analysis results of alkali metals in representative pyrolytic carbon samples. The analysis results are transmitted to the process execution control unit through one or more of the following methods: manual input, data interface, communication network or signal transmission line, as the basis for determining the selective leaching method and process parameters.

[0049] In this invention, the process execution control unit forms control or signal connections with the bio-oil aqueous phase dilution / acid addition preparation unit, the selective immersion reaction unit, and the drying unit, respectively, for controlling one or more of the following according to preset process parameters: preparation ratio, acid addition amount, liquid inlet amount, stirring rate, immersion temperature, immersion time, and drying temperature.

[0050] In this invention, the pyrolysis char storage and feeding unit 1 is used to store and supply the pyrolysis char to be treated to the immersion washing system; the bio-oil aqueous phase dilution / acid addition solution preparation unit 2 is used to prepare the bio-oil aqueous phase dilution solution or acid washing solution according to the preset process requirements; the sampling / preservation speciation analysis unit 3 is used to analyze the water-soluble, exchangeable, acid-soluble, and insoluble states of K, Na, Ca, and Mg in representative samples of pyrolysis char before selective dealkalization; the selective immersion washing reaction unit 4 is used to immerse and rinse the pyrolysis char according to the preset bio-oil aqueous phase dilution washing or acid washing conditions; the solid-liquid separation unit 5 is used to separate the solid biochar from the washing solution after immersion washing; the process execution control unit 7 is used to determine the bio-oil aqueous phase dilution ratio, whether to add acid, immersion temperature, immersion time, solid-liquid ratio, and stirring rate according to the preservation speciation analysis results and pre-experiment results; and the drying unit 8 is used to dry the dealkalized biochar after solid-liquid separation.

[0051] In this invention, the bio-oil aqueous phase dilution / acidification preparation unit includes a bio-oil aqueous phase tank, a water tank, an acid preparation tank, a metering pump, and a stirrer.

[0052] In this invention, the solid-liquid separation unit is connected to the wastewater treatment unit; And / or, the selective immersion reaction unit is connected to the wastewater treatment unit.

[0053] In this invention, the wastewater treatment unit 6 includes one or more of the following: a neutralization tank, a settling tank, a filter, an adsorption unit, and an evaporation and concentration unit. The wastewater treatment unit is used to neutralize, settle, filter, or recycle leaching wastewater and washing wastewater.

[0054] In this invention, the drying unit is connected to the granulation unit.

[0055] In this invention, the granulation unit 9 includes a carbon powder storage and metering unit, a binder preparation unit, a mixing and humidity conditioning unit, a granulation unit, a drying and cooling unit, and a sieving unit connected in sequence. The granulation unit is used to further prepare the dried low-migration alkali metal biochar into low-migration alkali metal biochar granules.

[0056] Apart from the above conditions, the present invention does not limit other conditions, and solutions well known in the art can be used.

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] Experimental Example 1

[0059] This experiment verifies the changes in the occurrence of alkali metals under different straws and different pyrolysis temperatures.

[0060] Corn stalks, rice stalks, and cotton stalks were used as raw materials and pyrolyzed at 350℃, 400℃, 450℃, and 500℃, respectively, to obtain biomass pyrolytic char at different pyrolysis temperatures. Industrial analysis, elemental analysis, calorific value, and total K / Na / Ca / Mg content were performed on each char sample. Extraction analysis was conducted sequentially according to water-soluble, exchangeable, acid-soluble, and insoluble states. The specific extraction process involved adding water, 1 mol / L ammonium acetate, and 1 mol / L hydrochloric acid sequentially, washing each step for 24 hours, and then performing ICP analysis.

[0061] The occurrence forms of pyrolytic carbon at different biomass and different pyrolysis temperatures were as follows: Figures 3 to 6 express. Figure 3 This was used to compare the effects of different biomass sources on the occurrence speciation of alkali metals / alkaline earth metals before pyrolysis. Figures 4 to 6These data are used to illustrate the changes in the occurrence forms of corn char, rice char, and cotton char at different pyrolysis temperatures. The data are used to establish the correspondence between raw material type, pyrolysis temperature, initial K+Na content, required overall removal rate, and the ratio of easily migratable K / Na, and serve as the basis for subsequent selection of bio-oil aqueous phase dilution washing or acid washing mode.

[0062] Depend on Figures 3 to 6 It is evident that the distribution of K, Na, Ca, and Mg in water-soluble, exchangeable, acid-soluble, and insoluble states varies significantly among different biomass raw materials and at different pyrolysis temperatures. Water-soluble and exchangeable components are highly mobile; a higher proportion of these components indicates a greater risk of migration, slagging, or corrosion during combustion, gasification, or metallurgical applications. Therefore, this experimental example demonstrates that selective dealkali removal based on speciation analysis and target K+Na content allows the washing mode to be matched to the raw material properties and pyrolysis conditions, distinguishing it from fixed water washing, fixed strong acid washing, or simple bio-oil washing.

[0063] Experiment Example 2

[0064] Selective dealkalization based on the results of speciation analysis and the target K+Na content. (Based on Experiment 1 and...) Figures 3 to 6 The data on the occurrence forms of K / Na were used, and the concentration of K+Na in the mixture of the target dealkali-treated pyrolysis carbon and pulverized coal was ≤0.25%. A typical pulverized coal was used as an example (as shown in Table 1). The required comprehensive removal rate of pyrolysis carbon to achieve the target was calculated using formulas 1-3. For carbon samples with a required comprehensive removal rate not exceeding 80%, bio-oil-aqueous phase dilution washing was used; for carbon samples with a required comprehensive removal rate exceeding 85%, acid washing was used; for carbon samples with a required comprehensive removal rate of 80-85%, enhanced bio-oil-aqueous phase dilution washing or acid washing was selected based on the K / Na occurrence forms and preliminary experimental results. After washing, the total K / Na, the removal rates of the four occurrence forms of K / Na, the easily migrating K / Na, fixed carbon, and calorific value were measured.

[0065] Table 1. Alkali metal content of a typical pulverized coal

[0066] Based on the K and Na elemental contents of a typical pulverized coal in Table 1, when biochar is blended with a typical pulverized coal at a mass ratio of 25%, and the blended fuel is required to have w(K) + w(Na) ≤ 0.25%, the w(K) + w(Na) in the biochar should not exceed 0.8359%. Under this constraint, the required K / Na combined removal rates for corn straw char samples at 350℃, 400℃, 450℃, and 500℃ are approximately 74.0%, 77.1%, 77.5%, and 66.5%, respectively, all of which can be classified as bio-oil-aqueous phase dilution washing type; the required K / Na combined removal rates for rice straw char samples at 350℃, 400℃, 450℃, and 500℃ are approximately 79.2%, 74.5%, 69.9%, and 73.8%, respectively, and can also generally be classified as bio-oil-aqueous phase dilution washing type, among which 3 The 50℃ sample has a K / Na removal rate close to 80%, which can be used as an enhanced bio-oil aqueous phase dilution wash or a boundary sample treatment. The required K / Na combined removal rates for cotton straw charcoal samples at 350℃, 400℃ and 450℃ are approximately 51.6%, 55.7% and 27.4%, respectively, which are suitable for mild bio-oil aqueous phase dilution wash. The initial w(K)+w(Na) of the 500℃ sample is approximately 0.7698%, which is already lower than the back-calculated upper limit of 0.8359%. Theoretically, it can meet the K+Na limit after 25% blending without the need for dealkalization.

[0067] Example 1

[0068] S1. The pyrolytic corn straw char selected from Experiment 2 at 450℃ was used as a representative pyrolytic char sample, with a particle size of 1~5mm. The volatile products generated during pyrolysis were collected by condensation at 20℃ to obtain crude bio-oil. The crude bio-oil was allowed to stand at 20℃ (room temperature) for 24h to allow natural stratification, and the liquid phase rich in water and water-soluble oxygen-containing organic matter was taken as the aqueous phase of the bio-oil.

[0069] The initial K, Ca, Na, and Mg contents of corn straw charcoal pyrolyzed at 450℃ are shown in Table 2.

[0070] Table 2. Initial content of alkali metals / alkaline earth metals

[0071] S2, when 450℃ pyrolysis corn straw char is mixed with a typical pulverized coal at a mass ratio of 25%, the required comprehensive removal rate of pyrolysis char when the mixture reaches w(K)+w(Na)≤0.25% is 77.5%.

[0072] S3. The diluted bio-oil aqueous phase obtained by diluting the bio-oil aqueous phase of pyrolyzed corn straw at 450℃ with water at a ratio of 1:10 wt is used as the washing solution. The solid-liquid mass ratio of pyrolyzed char to washing solution is 1:10, and the mixture is immersed in the solution at 25℃ and a stirring rate of 100 r / min for 1 h.

[0073] S4. After soaking, the liquid is separated into solid and liquid components, washed, and dried to obtain dealkali-reduced pyrolytic carbon.

[0074] S5. Evaluate the dealkali removal effect of the dealkali pyrolysis carbon by testing the sum of K and Na element content in the mixture of dealkali pyrolysis carbon and pulverized coal, the removal rate of easily migratable K or Na after dealkali removal, the fixed carbon retention rate of the dealkali pyrolysis carbon, and the calorific value retention rate of the dealkali pyrolysis carbon.

[0075] Example 2

[0076] The difference from Example 1 is that the soaking time in step S3 is modified to 2 hours.

[0077] Example 3

[0078] The difference from Example 1 is that the soaking time in step S3 is modified to 3 hours.

[0079] Examples 1-3 varied the immersion residence time and evaluated the changes in K, Na, Ca, and Mg content or removal rate. Figure 7 As shown, the results indicate that under the leaching conditions of a 1:10 dilution ratio of bio-oil in an aqueous phase, the K content decreased significantly with increasing leaching time, with a larger decrease in the initial stage of leaching. This suggests that the diluted bio-oil-water phase has a strong leaching effect on easily migratable K in corn straw pyrolysis char. The Ca content decreased slowly with increasing leaching time, indicating that some Ca could be leached by acidic components in the aqueous phase, but its release rate and removal magnitude were lower than that of K. The Mg and Na contents were generally low, and the changes with leaching time were not significant, indicating that further extending the leaching time had limited contribution to the further removal of Mg and Na. As the leaching time continued to increase, the decrease in K and Ca contents gradually slowed down, indicating that the leaching process gradually approached leaching equilibrium.

[0080] Table 3 shows the moisture, volatile matter, fixed carbon, ash content and calorific value of corn stalks before and after 450℃ charcoal washing in Example 1.

[0081] Table 3. Comparison of corn stalks before and after charcoal impregnation at 450℃

[0082] Table 3 shows that the fuel quality of corn straw charcoal at 450℃ was improved to some extent after impregnation. The moisture content of the sample decreased from 3.73% to 3.16% after impregnation, indicating that the impregnation-drying treatment did not cause significant moisture absorption. The volatile matter content decreased significantly from 24.14% to 14.07%, indicating that the impregnation process may have removed some low-molecular-weight soluble organic components and volatile components, further enriching the charcoal structure. Meanwhile, the fixed carbon content increased from 53.42% to 64.51%, an increase of 11.09 percentage points, indicating that the proportion of effective carbonaceous components in the biochar increased after impregnation. The ash content decreased slightly from 18.71% to 18.25%, indicating that impregnation had a certain removal effect on some inorganic minerals, but the reduction in ash content was limited due to the presence of a large amount of insoluble ash components in the corn straw charcoal. The calorific value increased from 23.50 MJ / kg to 23.94 MJ / kg, indicating that immersion washing did not reduce its fuel energy quality, but rather slightly improved it due to the enrichment of fixed carbon and the reduction of volatile matter.

[0083] Overall, the immersion treatment not only reduces the alkali metal content but also increases the fixed carbon ratio and calorific value to some extent, indicating that the treatment process does not weaken the basic fuel properties of corn straw char as an alternative fuel for blast furnace injection. The results also show that corn straw char at 450℃, after immersion, exhibits characteristics closer to the requirements of blast furnace injection fuel in terms of fixed carbon content, calorific value, and ash content.

[0084] Example 4

[0085] The difference from Example 2 is that the immersion temperature in step S3 is modified to 30°C.

[0086] Example 5

[0087] The difference from Example 2 is that the immersion temperature in step S3 is modified to 40°C.

[0088] Example 6

[0089] The difference from Example 2 is that the immersion temperature in step S3 is modified to 60°C.

[0090] Example 7

[0091] The difference from Example 2 is that the immersion temperature in step S3 is modified to 80°C.

[0092] Further investigation was conducted into the effect of the immersion temperature of the diluted bio-oil in the aqueous phase, and the results are as follows: Figure 8As shown, increasing the leaching temperature improves the removal rates of K and Na, with K showing the highest removal rate. This indicates that increasing the temperature promotes the release of water-soluble and exchangeable K / Na from the pyrolytic char. In contrast, the removal rates of Ca and Mg are relatively low, and the changes with increasing leaching temperature are limited, suggesting that Ca and Mg in the 450℃ corn straw pyrolytic char may exist more in a more stable acid-soluble or mineral-bound state. These results indicate that diluted bio-oil aqueous phase leaching has a more significant selective removal effect on highly mobile K / Na, while its removal effect on relatively stable Ca / Mg is weaker.

[0093] Based on the optimization of residence time and leaching temperature, further parameter screening was conducted by considering pyrolytic carbon particle size, bio-oil-water phase dilution ratio, and solid-liquid ratio. Particle size mainly affects the mass transfer process of the leaching solution entering the pores and internal ash sites of the carbon particles; the bio-oil-water phase dilution ratio affects the concentration of acidic components and leaching capacity; the solid-liquid ratio affects the effective amount of leaching solution per unit mass of pyrolytic carbon and the K / Na dissolution capacity. Therefore, selective leaching parameters should not be enhanced by simply extending the leaching time or increasing the leaching temperature to strengthen dealkalization, but should comprehensively consider the synergistic effects of particle size, leaching time, leaching temperature, bio-oil-water phase dilution ratio, and solid-liquid ratio. Therefore, with the comprehensive objectives of w(K)+w(Na) ≤ 0.25% in the final pyrolytic carbon and pulverized coal mixture, a high removal rate of easily migratable K / Na, and fixed carbon retention rate and calorific value retention rate meeting the target range, the appropriate ranges for pyrolytic carbon particle size, leaching residence time, bio-oil-water phase dilution temperature, bio-oil-water phase dilution ratio, and solid-liquid ratio were determined.

[0094] Comparative Example 1

[0095] The difference from Example 2 is that the washing solution in step S3 is only water, and the soaking time is 2 hours.

[0096] After immersion washing, the residual contents of K, Na, Ca, and Mg in the pyrolytic char after water washing were determined, and the results are shown in [Figure number missing]. Figure 9 The results showed that water washing could reduce the content of some K, Na, Ca, and Mg in pyrolytic char, indicating that water washing has a certain removal effect on water-soluble alkali metals. However, compared with water washing with a 1:10 dilution of bio-oil, the residual contents of K, Ca, Mg, and Na in the pyrolytic char after water washing were all higher, with the difference in K and Ca being more significant. This indicates that water washing alone mainly relies on dissolution to remove water-soluble components and is insufficient in removing exchangeable, weakly acid-soluble, or partially mineral-bound metal components.

[0097] This comparative example illustrates that while water washing alone is a simple process, it is insufficient to adequately reduce highly mobile K / Na and some alkaline earth metal residues in pyrolytic carbon, and it also fails to adjust the washing intensity based on the distribution differences of metal components in different occurrence forms within the pyrolytic carbon. In contrast, diluted bio-oil aqueous phase immersion washing contains organic acid components such as acetic acid and formic acid, which can further promote the release of exchangeable or weakly acid-soluble metals after water washing removes water-soluble components. Therefore, in the actual dealkali classification of this invention, water washing is not considered a necessary process route. Instead, based on the required comprehensive removal rate and occurrence forms of the target dealkali-removed pyrolytic carbon and pulverized coal mixture w(K) + w(Na) ≤ 0.25%, a choice is made between bio-oil aqueous phase dilution washing and bio-oil aqueous phase dilution plus acid washing.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for selective dealkali removal from biomass pyrolysis char based on the regulation of alkali metal occurrence speciation, characterized in that, Includes the following steps: S1. Pyrolyze biomass raw materials to obtain pyrolytic char and bio-oil; S2. The pyrolytic carbon is subjected to speciation analysis. The elements analyzed include K, Na, Ca and Mg. The contents of water-soluble, exchangeable, acid-soluble and insoluble states of each element are obtained. The sum of the contents of water-soluble and exchangeable states is defined as the easily migratable state. S3. Selectively impregnate the pyrolytic carbon; S4. The selectively washed liquid is sequentially subjected to solid-liquid separation, washing, and drying to obtain dealkalized pyrolytic carbon. S5. Evaluate the dealkali removal effect of the dealkali pyrolysis char to obtain low-migration alkali metal biochar. Specifically, the selective rinsing method described in step S3 includes: S3.1 Based on the sum of K and Na contents in the pyrolysis char and the mixing ratio of the dealkali pyrolysis char and pulverized coal, calculate the comprehensive removal rate required for the pyrolysis char when the sum of K and Na contents in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%. The calculation method is shown in Formulas 1 to 3: w 混 = (1 - x) x w 煤 + x x w 炭 Formula 1, When w 混 When ≤0.25%, w 炭max =[0.25%-(1-x)×w 煤 ]÷x formula 2, η = [w 炭初始 - w 炭max ÷ w 炭初始 × 100% Formula 3 In formulas 1~3, w 混 The sum of K and Na contents in the mixture of dealkali pyrolysis carbon and pulverized coal is given by , where x is the blending ratio of dealkali pyrolysis carbon in the mixture, and x ranges from 1 to 35 wt%. 煤 w is the sum of the K and Na contents in the pulverized coal. 炭 w is the sum of the K and Na contents in the dealkali pyrolysis char. 炭max η represents the maximum sum of K and Na content in the pyrolysis carbon at a blending amount of x, where η is the required overall removal rate of the pyrolysis carbon at a blending amount of x, and w is the maximum sum of K and Na content in the pyrolysis carbon. 炭初始 This is the sum of the K and Na contents in the pyrolytic char; S3.2 When the overall removal rate is <80%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase; when the overall removal rate is >85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase and acid; when the overall removal rate is 80~85%, the pyrolytic carbon is diluted and washed with bio-oil aqueous phase or diluted and washed with bio-oil aqueous phase and acid. The selective immersion conditions described in step S3 include: pyrolytic carbon particle size of 1-5 mm, solid-liquid mass ratio of 1:3-1:20, bio-oil-water phase to water mass ratio of 1:5-20, immersion solution pH of 2-5.5, immersion temperature of 15-80℃, immersion time of 0.5-4 h, and stirring rate of 20-300 r / min. The evaluation method described in step S5 specifically includes four evaluation indicators: the sum of K and Na content in the mixture of dealkali pyrolysis char and pulverized coal is ≤0.25%; the removal rate of easily migratable K or Na after dealkali removal is ≥90%; the fixed carbon retention rate of dealkali pyrolysis char is ≥95%; and the calorific value retention rate of dealkali pyrolysis char is ≥95%. Low-migratory alkali metal biochar must simultaneously meet at least three of the evaluation indicators.

2. The method according to claim 1, characterized in that, The biomass raw materials mentioned in step S1 include one or more of the following: pine wood, corn stalks, rice stalks, cotton stalks, bamboo, other forestry residues, and other crop straws. The pyrolysis temperature in step S1 is 300~600℃.

3. The method according to claim 1, characterized in that, The method for analyzing the occurrence speciation in step S2 specifically includes: sequential extraction of pyrolytic carbon, obtaining the water-soluble content by water extraction, obtaining the exchangeable content by ammonium acetate solution extraction, obtaining the acid-soluble content by acid solution extraction, and obtaining the insoluble content by subtracting the water-soluble content, exchangeable content and acid-soluble content from the total content. The total content is determined by ICP-OES, ICP-MS, flame photometry or atomic absorption spectrometry after digestion.

4. The method according to claim 1, characterized in that, The bio-oil aqueous phase in step S3.2, either through dilution and washing or through acid washing, is the aqueous phase obtained by allowing the bio-oil from step S1 to stand and separate into layers. The acid in the bio-oil aqueous phase dilution and acid washing step S3.2 includes one or more of formic acid, acetic acid, propionic acid, glycolic acid, citric acid, oxalic acid, and hydrochloric acid.

5. The method according to claim 1 or 4, characterized in that, The conditions for the bio-oil aqueous phase dilution washing in step S3.2 include: pyrolytic carbon particle size of 1~5mm, solid-liquid mass ratio of 1:3~1:20, bio-oil aqueous phase to water mass ratio of 1:5~20, washing solution pH of 3.5~5.5, immersion temperature of 15~80℃, immersion time of 0.5~3h, and stirring rate of 40~150r / min; The conditions for diluting and acid washing the bio-oil aqueous phase in step S3.2 include: pyrolytic carbon particle size of 1-5 mm, solid-liquid mass ratio of 1:3-1:20, bio-oil aqueous phase to water mass ratio of 1:5-20, washing solution pH of 2-3.5, immersion temperature of 15-80℃, immersion time of 1-4 h, and stirring rate of 40-150 r / min.

6. The method according to claim 1, characterized in that, The low-migration alkali metal biochar described in step S5 also includes post-processing, specifically including: sequentially crushing, sieving, mixing and humidifying, granulating and drying to obtain low-migration alkali metal biochar particles.

7. The apparatus used in the selective dealkali removal method of biomass pyrolysis char based on the regulation of alkali metal occurrence as described in any one of claims 1 to 6, characterized in that, The device includes a pyrolytic carbon storage and feeding unit, a bio-oil aqueous phase dilution / acidification preparation unit, a selective immersion reaction unit, a solid-liquid separation unit, a drying unit, a sampling and storage speciation analysis unit, and a process execution control unit. The pyrolysis char storage and feeding unit, the bio-oil aqueous phase dilution / acid addition preparation unit, the selective immersion reaction unit, the solid-liquid separation unit, and the drying unit are sequentially connected. The sampling and morphological analysis unit is electrically connected to the process execution control unit for transmitting the morphological analysis result signal. The process execution control unit is electrically connected to the bio-oil aqueous phase dilution / acidification preparation unit, the selective immersion reaction unit, and the drying unit for transmitting control signals.

8. The apparatus according to claim 7, characterized in that, The bio-oil aqueous phase dilution / acidification preparation unit includes a bio-oil aqueous phase tank, a water tank, an acid preparation tank, a metering pump, and a stirrer.

9. The apparatus according to claim 7, characterized in that, The solid-liquid separation unit is connected to the wastewater treatment unit; And / or, the selective immersion reaction unit is connected to the wastewater treatment unit; The wastewater treatment unit includes one or more of the following: neutralization tank, sedimentation tank, filter, adsorption unit, and evaporation concentration unit.

10. The apparatus according to claim 7, characterized in that, The drying unit is connected to the granulation and molding unit; The granulation unit includes a carbon powder storage and metering unit, a binder preparation unit, a mixing and humidity conditioning unit, a granulation unit, a drying and cooling unit, and a screening unit connected in sequence.

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