CN108219889B - Method for preparing biomass charcoal by using crop straws - Google Patents
Method for preparing biomass charcoal by using crop straws Download PDFInfo
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- CN108219889B CN108219889B CN201810058519.3A CN201810058519A CN108219889B CN 108219889 B CN108219889 B CN 108219889B CN 201810058519 A CN201810058519 A CN 201810058519A CN 108219889 B CN108219889 B CN 108219889B
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- 239000002028 Biomass Substances 0.000 title claims abstract description 138
- 239000010902 straw Substances 0.000 title claims abstract description 86
- 239000003610 charcoal Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000002245 particle Substances 0.000 claims abstract description 96
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000001301 oxygen Substances 0.000 claims abstract description 33
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 33
- 238000004227 thermal cracking Methods 0.000 claims abstract description 23
- 238000005056 compaction Methods 0.000 claims abstract description 18
- 238000006243 chemical reaction Methods 0.000 claims description 29
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 26
- 229910052799 carbon Inorganic materials 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 239000007789 gas Substances 0.000 claims description 5
- 238000005469 granulation Methods 0.000 claims description 5
- 230000003179 granulation Effects 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 5
- 239000008187 granular material Substances 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 2
- 238000005336 cracking Methods 0.000 abstract description 13
- 239000011148 porous material Substances 0.000 abstract description 10
- 230000008569 process Effects 0.000 abstract description 9
- 238000000197 pyrolysis Methods 0.000 abstract description 9
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
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- 230000000052 comparative effect Effects 0.000 description 14
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- 238000010438 heat treatment Methods 0.000 description 3
- 240000007594 Oryza sativa Species 0.000 description 2
- 235000007164 Oryza sativa Nutrition 0.000 description 2
- 240000000111 Saccharum officinarum Species 0.000 description 2
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- 238000005516 engineering process Methods 0.000 description 2
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L5/00—Solid fuels
- C10L5/40—Solid fuels essentially based on materials of non-mineral origin
- C10L5/44—Solid fuels essentially based on materials of non-mineral origin on vegetable substances
- C10L5/445—Agricultural waste, e.g. corn crops, grass clippings, nut shells or oil pressing residues
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
- C10B53/02—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form of cellulose-containing material
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
- C10B57/005—After-treatment of coke, e.g. calcination desulfurization
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/10—Biofuels, e.g. bio-diesel
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Agronomy & Crop Science (AREA)
- Solid Fuels And Fuel-Associated Substances (AREA)
Abstract
The invention discloses a method for preparing biomass charcoal by utilizing crop straws, which comprises the steps of crushing and granulating the crop straws in sequence, reducing the bulkiness of the crop straws, discharging air mixed in the crop straws in the granulating process, conveniently controlling the thermal cracking temperature, preventing excessive pyrolysis, maintaining the compaction density of biomass particles at 0.5-0.8 kg/L, facilitating the formation of a temperature gradient of the biomass particles from outside to inside, preventing the excessive pyrolysis, facilitating the volatilization of volatile matters or other gaseous matters due to reasonable compaction density, facilitating the formation of pores in the biomass charcoal and increasing the specific surface area of the biomass charcoal, and then thermally cracking the biomass particles under the condition of limited oxygen at the pressure of-0.1 kpa, facilitating the rapid volatilization of the volatile matters or other gaseous matters in the low-pressure thermal cracking process, and increasing the specific surface area of the biomass charcoal.
Description
Technical Field
The invention belongs to the technical field of pyrolysis of biochar, and particularly relates to a method for preparing biochar from crop straws.
Background
The crop straw is a general term of stem leaf (ear) part of mature crop. It generally refers to the remaining part of wheat, rice, corn, potatoes, rape, cotton, sugarcane and other crops after harvesting seeds, and is rich in nitrogen, phosphorus, potassium, calcium, magnesium, organic matters and the like.
At present, the following methods are common in the treatment of crop straws: firstly, crop straws are crushed and buried in a farmland for returning the straws to the field, but the method has slower speed of treating the straws and is easy to cause the problems of plant diseases and insect pests and the like; secondly, packing crop straws, and putting the crop straws into a thermal power generation boiler for biomass power generation, wherein the utilization rate of the straws is low; thirdly, the crop straws are thermally cracked into biomass charcoal, biomass oil or biomass gas, so that the crop straws are efficiently utilized.
Among the three treatment methods, thermal cracking of crop straws is a treatment method of crop straws with higher research heat at present, for example, Chinese patent document CN101993701A discloses a method for preparing biomass carbon based on waste crop straws, which comprises the steps of cutting crop straws into straw particles, washing and drying the straw particles, then filling the treated straw particles into a quartz tube of a carbonization furnace, introducing inert gas, then heating the straw particles to 350-550 ℃ from room temperature at a heating rate of 25 ℃/min under the environment of inert gas flow of 100m L/min, maintaining the temperature for 1-3min, then stopping heating, cooling the straw particles to the room temperature to obtain solid, and finally washing and drying the solid in sequence to obtain the biomass carbon, thereby treating the waste crop straws.
In the technology, the straw particles are obtained by directly cutting crop straws, are fluffy and are very easy to be mixed with air, so that the temperature in the subsequent high-temperature thermal cracking process is not easy to control, the temperature is easy to rise steeply, the pyrolysis is excessive, and the content of fixed carbon in the biochar is reduced. Therefore, the above-mentioned technology greatly reduces the thermal cracking time and introduces the inert gas for a long time to avoid over-pyrolysis, but at the same time, the thermal cracking in a short time is difficult to effectively increase the specific surface area of the biomass charcoal, which is just the specific surface area of the biomass charcoal is less than 10m2The reason for/g is.
Disclosure of Invention
Therefore, the invention aims to overcome the defects of low specific surface area and fixed carbon content of the existing biomass charcoal, and further provides a method for preparing the biomass charcoal by using crop straws, wherein the specific surface area and the fixed carbon content of the biomass charcoal are high.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the method for preparing biomass charcoal by using crop straws provided by the invention comprises the following steps:
sequentially crushing and granulating crop straws to prepare biomass particles, wherein the compaction density of the biomass particles is 0.5-0.8 kg/L;
under the condition of oxygen limitation, the biomass particles are thermally cracked under the pressure of-0.1 kpa to prepare the biomass charcoal.
Further, the biomass particles have a compacted density of 0.6-0.7 kg/L;
the pressure is-0.05 kpa-0 kpa.
Further, the crushing is to crush the crop straws to the length of 1cm-2 cm;
and the granulation is to extrude and granulate the crushed crop straws to form biomass particles with the particle diameter of 0.5-1.0 cm.
Furthermore, the water content of the crop straws is 8-15 wt%. Preferably 10 wt%.
Further, the temperature of the thermal cracking is 400-500 ℃.
Preferably, the thermal cracking temperature is 450 ℃ and the time is 1-2 h.
Further, the oxygen limitation is to introduce inert gas into the reaction system formed by the thermal cracking until the oxygen content in the reaction system is not more than 3%.
Further comprises the step of carrying out microwave treatment on the thermally cracked biomass particles for 5-10min under the conditions of 300-400W; and/or the presence of a gas in the gas,
the method also comprises the steps of crushing the biomass charcoal to the granularity of 10-20 meshes, and then spraying 300kg of pyroligneous liquor every 1t of the biomass charcoal.
Furthermore, the crop straw is at least one of rice straw, wheat straw, corn straw, sorghum straw, sugarcane straw and rape straw.
In addition, the invention also provides the biomass charcoal prepared by the method. .
Further, the specific surface area of the biomass charcoal is not less than 120m2/g；
The fixed carbon content in the biomass charcoal is not less than 65 wt%.
Compared with the prior art, the invention has the following beneficial effects:
(1) the method for preparing the biomass charcoal by using the crop straws has the advantages that the crop straws are sequentially crushed and granulated, the bulkiness of the crop straws is reduced, air mixed in the crop straws is discharged in the granulation process, the thermal cracking temperature is conveniently controlled, excessive pyrolysis is prevented, and the compacted density of biomass particles is maintained at 0.5-0.8 kg/L, so that the biomass charcoal is beneficial to organismsThe temperature gradient is formed by the biomass particles from outside to inside, excessive pyrolysis can be prevented, and meanwhile, the reasonable compaction density is beneficial to volatilization of volatile matters or other gaseous matters, formation of pores in the biomass carbon and improvement of the specific surface area of the biomass carbon; then, under the condition of oxygen limitation, the biomass particles are thermally cracked under the pressure of-0.1 kpa, volatile components or other gaseous substances in the thermal cracking process are favorably and rapidly volatilized from the biomass particles under the low pressure, so that the specific surface area of the biomass charcoal is increased, and tests prove that the specific surface area of the biomass charcoal prepared by the invention is 140m2The specific carbon content is more than 65wt%, and the biomass charcoal yield is more than 45 wt%.
(2) The method for preparing the biomass charcoal by using the crop straws avoids the defect that the bulkiness of the crop straws is still high due to low density, avoids the defect that the crop straws are dense and are not beneficial to volatilization of volatile matters or other gaseous matters due to high density by limiting the compaction density to be 0.5-0.8 kg/L, avoids the defect that the volatile matters or other gaseous matters are difficult to volatilize from the crop straws due to over-high pressure and avoids the defect that the outside air is easy to enter a reaction system due to over-low pressure by limiting the pressure of thermal cracking to be-0.1 kpa, reduces the volatilization of fixed carbon in the thermal cracking process by pre-extruding into particles, and reduces the dust content in a workshop.
(3) According to the method for preparing the biomass charcoal by using the crop straws, the crushing length of the crop straws is limited, so that the subsequent granulation and molding are facilitated; by limiting the diameter of the biomass particles, the requirements of temperature gradient and volatilization of volatile components or other gaseous substances are balanced, and meanwhile, the production efficiency can be improved; the water content of the crop straws is limited, so that the crop straws can be conveniently granulated and formed without a binder, and meanwhile, the water in the crop straws can volatilize in the thermal cracking process, so that developed pores are formed in the biomass charcoal, and the specific surface area of the biomass charcoal is improved; by carrying out microwave treatment on the biomass particles after thermal cracking, the specific surface area of the biomass charcoal is further improved, volatilization of non-volatile components or other gaseous substances is facilitated, and the fixed carbon content is improved.
(4) The biomass charcoal provided by the invention has large specific surface area, high fixed carbon content and rich pores, and can be applied to soil to improve soil fertility and soil, thereby achieving the effects of controlled release, water retention and soil moisture conservation. Meanwhile, the high fixed carbon content can play a role in carbon sequestration and emission reduction.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is an SEM image of biomass char in example 1 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 10 wt% into particles with the length of 1.5cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.6 kg/L and the particle diameter of 0.8 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.5 hours at 450 ℃ under the condition of limited oxygen at 0kpa to prepare the biomass charcoal.
As shown in fig. 1, the SEM image of the biomass char can be seen from fig. 1: the biomass charcoal has a specific surface area of 141.6m2/g and an average pore diameter of 4.23 nm.
Example 2
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing sorghum straws with the water content of 8 wt% into particles with the length of 2cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.7 kg/L and the particle diameter of 1 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles at-0.1 kpa at 500 ℃ for 1h under the limited oxygen condition to obtain the biomass charcoal.
Example 3
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing the wheat straws with the water content of 15wt% into particles with the length of 1cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.5 kg/L and the particle diameter of 0.5 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 2 hours at 400 ℃ under the condition of oxygen limitation at 0.1kpa to prepare the biomass charcoal.
Example 4
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing the corn straws with the water content of 13 wt% into particles with the length of 1.3cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.8 kg/L and the particle diameter of 0.7 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.3 hours at-0.05 kpa and 470 ℃ under the limited oxygen condition to obtain the biomass charcoal.
Example 5
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 9 wt% into particles with the length of 1.7cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.8 kg/L and the particle diameter of 0.6 cm;
2) introducing helium into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.6h at the temperature of 420 ℃ under the condition of limited oxygen to obtain the biomass charcoal.
Example 6
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 10 wt% into particles with the length of 1.5cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.6 kg/L and the particle diameter of 0.8 cm;
2) introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.5h at 450 ℃ at 0kpa under the limited oxygen condition;
3) and (3) carrying out microwave treatment on the biomass particles after thermal cracking for 10min under 300W to obtain the biomass charcoal.
Example 7
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing sorghum straws with the water content of 8 wt% into particles with the length of 2cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.7 kg/L and the particle diameter of 1 cm;
2) introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles at-0.1 kpa at 500 ℃ for 1h under the limited oxygen condition;
3) and (3) carrying out microwave treatment on the biomass particles after thermal cracking for 5min under 400W to obtain the biomass charcoal.
Example 8
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing the wheat straws with the water content of 15wt% into particles with the length of 1cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.5 kg/L and the particle diameter of 0.5 cm;
2) introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 2 hours at 400 ℃ under the condition of oxygen limitation at 0.1kpa to prepare biomass charcoal;
3) the biomass char was crushed to a particle size of 15 mesh, and then 270kg of pyroligneous liquor was sprayed per 1t of biomass char.
Example 9
The embodiment provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 10 wt% into particles with the length of 1.5cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.6 kg/L and the particle diameter of 0.8 cm;
2) introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.5h at 450 ℃ at 0kpa under the limited oxygen condition;
3) performing microwave treatment on the thermally cracked biomass particles at 300W for 10min to prepare biomass charcoal;
4) the biomass char was crushed to a particle size of 20 mesh, and then 250kg of pyroligneous liquor was sprayed per 1t of biomass char.
Comparative example 1
The comparative example provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 10 wt% into particles with the length of 1.5 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the particles for 1.5 hours at 450 ℃ under the condition of limited oxygen at 0kpa to obtain the biomass charcoal.
Comparative example 2
The comparative example provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing wheat straws with the water content of 10 wt% into particles with the length of 1.5cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 0.6 kg/L and the particle diameter of 0.8 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1.5h at 450 ℃ under the condition of limited oxygen at 5kpa to obtain the biomass charcoal.
Comparative example 3
The comparative example provides a method for preparing biomass charcoal by using crop straws, which comprises the following steps:
1) crushing sorghum straws with the water content of 8 wt% into particles with the length of 2cm, and then extruding and granulating the particles to form biomass particles with the compaction density of 1.2 kg/L and the particle diameter of 1 cm;
2) and introducing nitrogen into the reaction system until the oxygen content in the reaction system is not more than 3%, and thermally cracking the biomass particles for 1h at 500 ℃ at 3kpa under the limited oxygen condition to obtain the biomass charcoal.
Test example 1
The specific surface area and pore size of the biomass charcoal prepared in each of the above examples and comparative examples were measured in accordance with GB/T19587-2004, and the corresponding measurement results are shown in Table 1 below:
TABLE 1 specific surface area and pore size of Biomass charcoal
| Specific surface area/m2/g | Pore size/nm | |
| Example 1 | 141.6 | 4.23 |
| Example 2 | 140.2 | 4.57 |
| Example 3 | 140.5 | 4.34 |
| Example 4 | 142.5 | 4.12 |
| Example 5 | 140.8 | 4.58 |
| Example 6 | 152.8 | 4.35 |
| Example 7 | 151.5 | 4.47 |
| Example 8 | 140.5 | 4.34 |
| Example 9 | 152.8 | 4.35 |
| Comparative example 1 | 80.2 | 6.33 |
| Comparative example 2 | 58.1 | 7.26 |
| Comparative example 3 | 63.8 | 6.57 |
As can be seen from Table 1, the biomass particles are maintained at a compacted density of 0.5-0.8 kg/L, and the reasonable compacted density is favorable for volatilization of volatile components or other gaseous substances, and is favorable for formation of pores in the biomass carbon and increase of the specific surface area of the biomass carbon, and then the biomass particles are subjected to thermal cracking under the condition of oxygen limitation at a pressure of-0.1 kpa, and volatile components or other gaseous substances in the thermal cracking process are favorably and rapidly volatilized from the biomass carbon at the low pressure, so that the biomass carbon prepared by the biomass carbon has a large specific surface area and a small pore size.
Test example 2
The fixed carbon content of the biomass charcoal prepared in each of the above examples and comparative examples was measured, and the biomass charcoal yield was also calculated, and the corresponding test results are shown in table 2 below:
TABLE 2 fixed carbon content in Biomass charcoal and Biomass charcoal yield
| Fixed carbon content | Biomass char yield | |
| Example 1 | 65wt％ | 45wt％ |
| Example 2 | 64wt％ | 44wt％ |
| Example 3 | 64wt％ | 45wt％ |
| Example 4 | 65.5wt％ | 46wt％ |
| Example 5 | 64wt％ | 44wt％ |
| Example 6 | 66.3％ | 46wt％ |
| Example 7 | 66.2％ | 46wt％ |
| Example 8 | 64wt％ | 45wt％ |
| Example 9 | 66.3％ | 46wt％ |
| Comparative example 1 | 32wt％ | 20wt％ |
| Comparative example 2 | 30wt％ | 22wt％ |
| Comparative example 3 | 31wt％ | 23wt％ |
As can be seen from Table 2, the invention crushes and granulates the crop straws in sequence, reduces the bulkiness, discharges air mixed in the crop straws in the granulation process, is convenient to control the thermal cracking temperature and prevent excessive pyrolysis, and maintains the compaction density of the biomass particles at 0.5-0.8 kg/L, thereby being beneficial to forming a temperature gradient from outside to inside of the biomass particles and also preventing excessive pyrolysis, so that the fixed carbon content in the biomass carbon is more than 65wt%, and the biomass carbon yield is more than 45 wt%.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (4)
1. A method for preparing biomass charcoal by using crop straws comprises the following steps:
sequentially crushing and granulating crop straws to prepare biomass particles, wherein the compaction density of the biomass particles is 0.5-0.8 kg/L;
under the condition of oxygen limitation, carrying out thermal cracking on the biomass particles under the pressure of-0.1 kpa to prepare biomass charcoal; wherein,
the crushing is to crush the crop straws to the length of 1cm-2 cm;
the granulation is to extrude and granulate the crushed crop straws to form biomass particles with the particle diameter of 0.5-1.0 cm;
the water content of the crop straws is 8-15 wt%;
the temperature of the thermal cracking is 400-500 ℃, and the time is 1-2 h;
the oxygen limitation is to introduce inert gas into a reaction system formed by the thermal cracking until the oxygen content in the reaction system is not more than 3 percent;
the specific surface area of the biomass charcoal is not less than 120m2(ii)/g, fixed carbon content of not less than 65 wt%.
2. The method of claim 1, wherein the biomass particles have a compacted density of 0.6-0.7 kg/L;
the pressure is-0.05 kpa-0 kpa.
3. The method as set forth in any one of claims 1 to 2, further comprising the step of subjecting the thermally cracked biomass particles to microwave treatment at 400W of 300-; and/or the presence of a gas in the gas,
the method also comprises the steps of crushing the biomass charcoal to the granularity of 10-20 meshes, and then spraying 300kg of pyroligneous liquor every 1t of the biomass charcoal.
4. Biomass char produced by the method of any one of claims 1-3.
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