CN117819544A - Method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis - Google Patents
Method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 156
- 238000000034 method Methods 0.000 title claims abstract description 109
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 238000000197 pyrolysis Methods 0.000 title claims abstract description 91
- 229920000742 Cotton Polymers 0.000 title claims abstract description 75
- 239000010902 straw Substances 0.000 title claims abstract description 67
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 24
- 239000007789 gas Substances 0.000 claims abstract description 189
- 238000006243 chemical reaction Methods 0.000 claims abstract description 140
- 230000008569 process Effects 0.000 claims abstract description 69
- 239000002028 Biomass Substances 0.000 claims abstract description 50
- 239000003610 charcoal Substances 0.000 claims abstract description 43
- 238000001816 cooling Methods 0.000 claims abstract description 43
- 239000002994 raw material Substances 0.000 claims abstract description 33
- 239000003345 natural gas Substances 0.000 claims abstract description 27
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 26
- 239000002023 wood Substances 0.000 claims abstract description 17
- 239000000052 vinegar Substances 0.000 claims abstract description 16
- 235000021419 vinegar Nutrition 0.000 claims abstract description 16
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 9
- 238000003763 carbonization Methods 0.000 claims description 86
- 239000002002 slurry Substances 0.000 claims description 58
- 239000000463 material Substances 0.000 claims description 50
- 238000001994 activation Methods 0.000 claims description 40
- 230000004913 activation Effects 0.000 claims description 38
- 239000000843 powder Substances 0.000 claims description 38
- 238000004898 kneading Methods 0.000 claims description 29
- 239000007787 solid Substances 0.000 claims description 28
- 239000002253 acid Substances 0.000 claims description 27
- 239000011358 absorbing material Substances 0.000 claims description 26
- 239000007788 liquid Substances 0.000 claims description 24
- 238000005507 spraying Methods 0.000 claims description 24
- 238000003786 synthesis reaction Methods 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 238000006477 desulfuration reaction Methods 0.000 claims description 23
- 230000023556 desulfurization Effects 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 21
- 238000001179 sorption measurement Methods 0.000 claims description 21
- 239000000654 additive Substances 0.000 claims description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 18
- 239000001301 oxygen Substances 0.000 claims description 18
- 229910052760 oxygen Inorganic materials 0.000 claims description 18
- 230000015572 biosynthetic process Effects 0.000 claims description 14
- 238000005262 decarbonization Methods 0.000 claims description 14
- 238000002360 preparation method Methods 0.000 claims description 14
- 230000018044 dehydration Effects 0.000 claims description 12
- 238000006297 dehydration reaction Methods 0.000 claims description 12
- 239000011269 tar Substances 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 12
- 238000010000 carbonizing Methods 0.000 claims description 9
- 238000005336 cracking Methods 0.000 claims description 9
- 239000007791 liquid phase Substances 0.000 claims description 9
- 230000003213 activating effect Effects 0.000 claims description 8
- 229920001732 Lignosulfonate Polymers 0.000 claims description 7
- 239000002202 Polyethylene glycol Substances 0.000 claims description 7
- 229920002472 Starch Polymers 0.000 claims description 7
- 230000000996 additive effect Effects 0.000 claims description 7
- 238000010009 beating Methods 0.000 claims description 7
- 239000011280 coal tar Substances 0.000 claims description 7
- 229920001467 poly(styrenesulfonates) Polymers 0.000 claims description 7
- 229920002401 polyacrylamide Polymers 0.000 claims description 7
- 229920001223 polyethylene glycol Polymers 0.000 claims description 7
- 239000011970 polystyrene sulfonate Substances 0.000 claims description 7
- 229960002796 polystyrene sulfonate Drugs 0.000 claims description 7
- 238000003825 pressing Methods 0.000 claims description 7
- 239000004576 sand Substances 0.000 claims description 7
- 238000000926 separation method Methods 0.000 claims description 7
- HLPHHOLZSKWDAK-UHFFFAOYSA-M sodium;formaldehyde;naphthalene-1-sulfonate Chemical compound [Na+].O=C.C1=CC=C2C(S(=O)(=O)[O-])=CC=CC2=C1 HLPHHOLZSKWDAK-UHFFFAOYSA-M 0.000 claims description 7
- 235000019698 starch Nutrition 0.000 claims description 7
- 239000008107 starch Substances 0.000 claims description 7
- 238000007906 compression Methods 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 238000010298 pulverizing process Methods 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 2
- 230000006835 compression Effects 0.000 claims description 2
- 238000005520 cutting process Methods 0.000 claims description 2
- 238000005261 decarburization Methods 0.000 claims description 2
- 238000000151 deposition Methods 0.000 claims description 2
- 238000000465 moulding Methods 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 abstract description 12
- 239000001257 hydrogen Substances 0.000 abstract description 7
- 230000008901 benefit Effects 0.000 abstract description 4
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 239000003344 environmental pollutant Substances 0.000 abstract description 2
- 239000007792 gaseous phase Substances 0.000 abstract description 2
- 239000012071 phase Substances 0.000 abstract description 2
- 231100000719 pollutant Toxicity 0.000 abstract description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 abstract 1
- 238000010438 heat treatment Methods 0.000 description 35
- 239000000203 mixture Substances 0.000 description 27
- 239000005539 carbonized material Substances 0.000 description 25
- 239000000047 product Substances 0.000 description 24
- 238000002156 mixing Methods 0.000 description 16
- 230000000694 effects Effects 0.000 description 15
- 238000003756 stirring Methods 0.000 description 15
- 238000007599 discharging Methods 0.000 description 12
- 208000005156 Dehydration Diseases 0.000 description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 11
- 239000003795 chemical substances by application Substances 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 10
- 230000009471 action Effects 0.000 description 10
- 239000003054 catalyst Substances 0.000 description 10
- 238000002485 combustion reaction Methods 0.000 description 10
- 239000003546 flue gas Substances 0.000 description 10
- 239000000295 fuel oil Substances 0.000 description 10
- 230000006872 improvement Effects 0.000 description 9
- 239000003570 air Substances 0.000 description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 6
- 241000196324 Embryophyta Species 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 5
- 239000003463 adsorbent Substances 0.000 description 5
- 229940045348 brown mixture Drugs 0.000 description 5
- 210000003298 dental enamel Anatomy 0.000 description 5
- 230000003009 desulfurizing effect Effects 0.000 description 5
- 230000009977 dual effect Effects 0.000 description 5
- 235000013305 food Nutrition 0.000 description 5
- 239000000446 fuel Substances 0.000 description 5
- 230000005484 gravity Effects 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 230000036541 health Effects 0.000 description 5
- 238000009434 installation Methods 0.000 description 5
- 150000002576 ketones Chemical class 0.000 description 5
- 239000002808 molecular sieve Substances 0.000 description 5
- 230000007935 neutral effect Effects 0.000 description 5
- 239000003921 oil Substances 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 238000010008 shearing Methods 0.000 description 5
- 239000000741 silica gel Substances 0.000 description 5
- 229910002027 silica gel Inorganic materials 0.000 description 5
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 5
- 239000011800 void material Substances 0.000 description 5
- 239000011787 zinc oxide Substances 0.000 description 5
- 238000000746 purification Methods 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 239000011343 solid material Substances 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000002309 gasification Methods 0.000 description 2
- 240000007594 Oryza sativa Species 0.000 description 1
- 235000007164 Oryza sativa Nutrition 0.000 description 1
- 241000209140 Triticum Species 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000010903 husk Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 239000012263 liquid product Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 235000009566 rice Nutrition 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 238000009331 sowing Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- 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
Abstract
The invention provides a method for preparing synthetic natural gas and active carbon by microwave pyrolysis of cotton straw. Wherein, the gaseous phase generated by the reaction is cooled and condensed to obtain wood vinegar; the non-condensable gas obtained by cooling and condensing the gas phase generated by the reaction mainly comprises combustible gases such as methane, hydrogen, carbon monoxide and the like, and then the natural gas is prepared by treatment; the biomass charcoal generated by the reaction is processed to prepare the activated charcoal. The method provided by the invention has the advantages of easily available and renewable raw materials, simple process, no pollutant emission and environmental friendliness, and the prepared products are wood vinegar, natural gas and active carbon, have great utilization value, and find a feasible way for the efficient utilization of cotton straw resources.
Description
Technical Field
The invention belongs to the technical field of cotton straw pyrolysis recovery, and particularly relates to a method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis.
Background
China is the first cotton production country in the world, and according to the statistical data published by the national statistical bureau, the cotton sowing area in China 2017 is 322.96 ten thousand hm 2 According to 300kg/667m of per unit yield straw 2 The calculation is that the annual cotton stalk yield is about 1453 ten thousand t, and the utilization of the huge amount of cotton stalk resource can generate huge economic benefit. The microwave pyrolysis of cotton straw is a new development direction of the resource utilization of cotton straw, and has great advantages. However, to date, there is no scheme for recycling the product after the microwave pyrolysis reaction of cotton straw.
For example, chinese patent document CN 108219889A discloses a method for preparing biomass charcoal by using crop straw, which mainly uses crop straw to prepare biomass charcoal with high specific surface area and fixed carbon content, and the specific surface area of the prepared biomass charcoal sample is 140m 2 /g-152m 2 Between/g, this is required to have a specific surface area of 900m with commercial granular activated carbon 2 /g-1100m 2 The difference of above/g is large and cannot be applied as commercial activated carbon.
Meanwhile, chinese patent document CN 111378509A discloses a biomass microwave pyrolysis gasification method and system, and discloses that biomass raw materials are derived from corn straw, rice husk, wheat straw, wood block, leaf or branch and any substances containing lignocellulose, wherein the biomass raw materials are cracked The decomposition reaction temperature is 800-1000 ℃, the gas of microwave pyrolysis gasification is one or a combination of more of steam, carbon dioxide, air and oxygen, and phosphoric acid is added as an activating agent, and the specific surface area of the obtained activated carbon is 1200m 2 /g～1800m 2 And/g. But it is only capable of preparing powdered activated carbon.
In addition, chinese patent document CN 112639058B discloses a continuous operation method of microwave pyrolysis of solid materials containing organic matters, which comprises mixing the solid materials containing organic matters with a liquid organic medium, and then delivering the obtained mixture to a microwave field; the mixture is then continuously contacted with a strong wave-absorbing material in an inert atmosphere or under vacuum, wherein the strong wave-absorbing material continuously generates high temperature under microwaves so that the solid material containing the organic matters is continuously cracked together with the liquid organic medium, thereby realizing continuous operation. It does not mention the forward and rational use of cleavage products.
Therefore, there is a need for an efficient method for preparing synthetic natural gas and activated carbon by microwave pyrolysis using cotton straw.
Disclosure of Invention
In order to solve the defects and shortcomings of the prior art, a method for preparing synthetic natural gas and active carbon by microwave pyrolysis of cotton straw is provided, so that the problem that no method for preparing the synthetic natural gas and active carbon by microwave pyrolysis of cotton straw exists at present can be solved.
The invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following steps:
step one: mud kneading stage of wave-absorbing material
The wave-absorbing material is measured and then is ground into powder, after the particle size is smaller than 180 meshes, water and additives are added, and the powder is uniformly stirred and mixed to prepare slurry;
step two: spraying stage of cotton stalk surface
After beating and pressing cotton straw and blowing sand by air, cutting the cotton straw into blocks of 10-15 mm, and uniformly spraying the slurry obtained in the step one on the surface of the cotton straw to form a reaction material;
step three: stage of microwave pyrolysis reaction
The reaction materials are sent into a microwave cracking reaction device, and after nitrogen is introduced, microwave cracking reaction is carried out; in the reaction process, a microwave generator in a microwave pyrolysis reaction device generates microwaves with the frequency of 2450MHz to directly heat reaction materials to 290-750 ℃ and the operating pressure is kept at 5-8 KPa;
step four: solid, liquid and gas separation stage
Depositing biomass carbon formed after the microwave pyrolysis reaction at the bottom of a microwave pyrolysis reaction device and cooling to below 200 ℃; removing tar from the gas formed after the microwave pyrolysis reaction, cooling the gas to below 100 ℃, condensing the condensable gas in the gas into a liquid phase, and obtaining the rest gas as mixed gas;
Step five: natural gas synthesis stage
Carrying out compression cooling, CO conversion, dry desulfurization, PSA decarburization, methanation, depressurization and dehydration on the mixed gas in the step four to finally form natural gas with the methane content of more than 98%;
step six: stage of activated carbon preparation
And (3) carrying out cooling pulverization, kneading molding, carbonization activation, deashing and drying on the biomass carbon obtained in the step (IV) to finally form the activated carbon.
As a further improvement of the scheme, the additive adopted in the first step is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
As a further improvement of the scheme, the solid content of the slurry obtained in the step one is kept between 10.5% and 58.5%.
As a further improvement of the scheme, the solid content weight ratio of the cotton straw to the slurry in the reaction material obtained in the second step is 100:1.5 to 80.
As a further improvement of the above scheme, the liquid phase obtained in the fourth step is wood vinegar.
As a further improvement of the above scheme, theThe mixed gas obtained in the fourth step comprises the following components: h 2 25.0 to 35.0 percent, 18.5 to 24.0 percent of CO and CH 4 15.0 to 35.0 percent, CO 2 26.2 to 36.8 percent, and other gases 1.5 to 3.5 percent, wherein the percentage is volume percentage.
As a further improvement of the above scheme, the synthesis process of the natural gas in the fifth step is as follows:
s1: compressing the mixed gas obtained in the step four to 2.1-3.0 MPa, and reducing the temperature to 28-45 ℃;
s2: CO conversion is carried out on the gas obtained in the S1 under the condition of conversion pressure of 2.1-2.5 MPa and conversion temperature of 200-470 ℃ so that CO and H in the gas 2 O reacts to form H 2 And CO 2 ；
S3: carrying out dry desulfurization on the gas obtained in S2 under the conditions of desulfurization pressure of 2.1-2.9 MPa and desulfurization temperature of 200-400 ℃ to ensure that H in the desulfurized gas 2 S content is less than or equal to 0.1PPm;
s4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 1.5-2.8 MPa and the adsorption temperature is less than or equal to 40 ℃ so that CO in the gas subjected to PSA decarbonization 2 Removing;
s5: methanation is carried out on the gas obtained in the step S4 under the condition of the pressurizing pressure of 3.1-4.5 MPa and the temperature of 200-500 ℃ so as to lead CH in the methanated gas 4 The content reaches more than 98 percent;
s6: and (3) reducing the pressure of the gas obtained in the step S5 to 1.5-1.9 MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption method, so that the dew point of the dehydrated gas is less than-40 ℃, thereby obtaining the qualified natural gas.
As a further improvement of the above scheme, the preparation process of the activated carbon in the step six is as follows:
s1: naturally cooling the biomass charcoal obtained in the step four to normal temperature and pulverizing, so that the granularity of the pulverized biomass charcoal powder is smaller than 200 meshes;
s2: the biomass charcoal powder obtained in the step S1 is fully and uniformly mixed with coal tar under the conditions of the kneading temperature of 70-90 ℃ and the kneading time of 15-20 min, and then dried to form a column raw material;
s3: carbonizing the columnar raw material obtained in the step S2 at 550-650 ℃ under the condition of no or little oxygen to form columnar clinker;
s4: sequentially preheating and drying the columnar clinker obtained in the step S3 at 500-600 ℃, deep carbonizing at 700 ℃ and activating at 800-950 ℃, and cooling to 400 ℃ in a cooling section to form the specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram;
s5: and (3) deashing the activated carbon obtained in the step (S4) by using an acid washing process, and drying to obtain qualified activated carbon.
As a further improvement of the scheme, the mass ratio of the water vapor to the pillar clinker in the activation process of S4 is 8-10: 1.
as a further improvement of the scheme, the activation time of the S4 is 30-50 minutes.
The beneficial effects of the invention are as follows:
compared with the prior art, the method for preparing the synthetic natural gas and the activated carbon by the microwave pyrolysis of the cotton straw is characterized in that the microwave material is added into the cotton straw, and gas, liquid and solid products are separated according to the composition of the components after the pyrolysis reaction. Wherein, the gaseous phase generated by the reaction is cooled and condensed to obtain wood vinegar; the non-condensable gas obtained by cooling and condensing the gas phase generated by the reaction mainly comprises combustible gases such as methane, hydrogen, carbon monoxide and the like, and then the natural gas is prepared by treatment; the biomass charcoal generated by the reaction is processed to prepare the activated charcoal.
The method provided by the invention has the advantages of easily available and renewable raw materials, simple process, no pollutant emission and environmental friendliness, and the prepared products are wood vinegar, natural gas and active carbon, have great utilization value, and find a feasible way for the efficient utilization of cotton straw resources.
Drawings
FIG. 1 is a schematic diagram of the steps of the present invention.
Detailed Description
The following detailed description of specific embodiments of the invention refers to the accompanying drawings, which illustrate in further detail:
example 1
According to the method shown in fig. 1, the invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following specific steps:
Step one: mud kneading stage of wave-absorbing material
187.5kg of wave-absorbing material is metered and then is put into a jet mill for grinding, and the powder is finely ground in a powder making machine until the granularity is smaller than 180 meshes, and then is kneaded. The kneading is to uniformly mix the wave-absorbing material with water and additives, and send the formed slurry into a stirrer, and the stirring process is not only for uniformly mixing the wave-absorbing slurry, but also has the function of enabling the slurry to undergo strong shearing in the stirring process, and improving the rheological property of the slurry due to the action between the additives and the surface of the wave-absorbing material. The prepared slurry is conveyed to a sprayer for standby in the surface spraying process through a slurry pump. Wherein the solid content in the slurry is 10.5%, and the additive is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
Step two: spraying stage of cotton stalk surface
12500kg of cotton straw is subjected to beating and pressing, sand is blown off by air, the cotton straw is conveyed to a slicing process, the cotton straw is cut into blocks with the diameter of 10 mm-15 mm, the cotton straw blocks are conveyed to a surface spraying process and contacted with 1785.7kg of atomized slurry with the solid content of 10.5% sprayed by a sprayer which is pumped from the slurry to the surface spraying process, and the mixture is subjected to a uniform mixing process to uniformly mix the cotton straw with the basic surface of the slurry, so that a reaction material is formed.
Step three: stage of microwave pyrolysis reaction
The reaction materials are conveyed into a high-level bin of a microwave pyrolysis process through a large-inclination-angle belt conveyor, and enter the microwave pyrolysis reaction device to carry out pyrolysis reaction through the automatic control of a metering device arranged at the bottom of the high-level bin according to the material level of the microwave pyrolysis reaction device. The microwave pyrolysis reaction device is operated under the condition that the reaction temperature is 290 ℃ and the operating pressure is 5KPa micro positive pressure. The reaction energy is generated by a microwave generator and is fed into a resonant cavity of the microwave pyrolysis reaction device through a waveguide pipeline, so that the materials in the microwave pyrolysis reaction device are directly heated, and the microwaves have a 'non-thermal effect' on the high polymer. The dual heating effect makes the material heating speed fast and the efficiency high. The double heating effect can quickly dissociate high molecular substances into gas products of low molecular chains.
Step four: solid, liquid and gas separation stage
The gas output from the gas outlet in the microwave cracking reaction device firstly passes through an electrostatic oil catcher to remove a small amount of tar in the gas, then passes through a cooler to cool the gas to below 100 ℃, then condenses the condensable gas into a liquid phase when condensed by a condenser, and the liquid separated from the gas and the liquid is wood vinegar, which is also called plant acid, and is a reddish brown mixture containing various organic matters such as acid, alcohol, phenol, ketone and the like. Wood vinegar is widely used in chemical industry, forestry, agriculture, animal husbandry, food processing industry and medical and health industry.
The non-condensable gas obtained after cooling and condensing is the mixed gas (wherein the components of the mixed gas are H) 2 26.0%, CO 19.50%, CH 4 15.8%, CO 2 36.8% and 1.90% of other gases, wherein the percentages are by volume) are sent to synthesis of natural gas.
3860.2kg of biomass charcoal formed through the microwave pyrolysis reaction is deposited at the bottom of the microwave pyrolysis reaction device, is discharged through a biomass charcoal discharging machine arranged at an oblique outlet at the bottom, and enters a summarizing spiral discharging machine through program control.
Step five: natural gas synthesis stage
S1: 3167Nm of the mixed gas obtained in the fourth step 3 The gas compression process is carried out, the gas is compressed to 2.1MPa, and the temperature is reduced to 28 ℃;
s2: the gas obtained in the step S1 is subjected to CO shift reaction under the condition of shift pressure of 2.1MPa and shift temperature of 200 ℃, and the shift main reaction is as follows:
CO+H 2 O＝H 2 +CO 2
the shift adopts a sulfur-tolerant shift catalyst with the model number of B303Q;
s3: carrying out dry desulfurization on the gas obtained in the step S2 under the condition of desulfurization pressure of 2.1MPa and desulfurization temperature of 200 ℃, wherein zinc oxide with the model of T306 is selected as a dry desulfurizing agent, so that H in the desulfurized gas 2 The S content is less than or equal to 0.1PPm, and meets the requirement of methane synthesis reaction.
S4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 1.5MPa and the adsorption temperature is less than or equal to 40 ℃ so as to ensure that CO in the gas subjected to PSA decarbonization 2 The removal of the gas, so that the obtained gas meets the requirement of synthesis reaction, and the composition components are as follows: h 2 58.2%, CO 12.43%, CH 4 24.53%, CO 2 4.8%, wherein the percentages are by volume, the molar ratio of hydrogen to carbon (H 2 -CO 2 )/(CO+CO 2 ) =3.1. Wherein the CO is resolved 2 2104kg of liquid CO is obtained after purification 2 。
S5: 2039.8Nm obtained in S4 3 Pressurizing the gas to 3.1MPa for the second time, heating to 200 ℃, and then sending the gas into a methanation reactor for methanation treatment, wherein the main reaction of methanation is as follows:
CO+3H 2 ＝CH 4 +H 2 O+Q,
CO2+4H 2 ＝CH 4 +2H 2 O+Q
the methanation treatment adopts Topsoe (TREMPTM) methanation process, and adopts a catalyst with the model of MCR-2X to ensure that CH in the methanated gas 4 The content reaches more than 98 percent.
S6: and (3) reducing the pressure of the gas obtained in the step (S5) to 1.5MPa, reducing the temperature to below 40 ℃, and dehydrating by using a dehydration process of a solid adsorption method under pressure, wherein molecular sieves, silica gel and the like are selected as adsorbents. The qualified natural gas flow obtained after dehydration treatment is 799Nm 3 The methane content is above 98.6%, the gas dew point is below-40 ℃, and the remote transportation of the pressure pipeline is convenient.
Step six: stage of activated carbon preparation
S1: naturally cooling 3860kg of biomass charcoal obtained in the step four to normal temperature, and then conveying to Raymond mill machine-made powder, so that the granularity of the biomass charcoal powder after powder preparation is smaller than 200 meshes;
s2: fully and uniformly mixing the biomass charcoal powder obtained in the step S1 with coal tar under the condition of a kneading temperature of 70 ℃ and a kneading time of 15min by using a screw mixer, then feeding the mixture into a screw extruder to extrude cylindrical strips, and drying to form columnar raw materials;
s3: delivering the columnar raw material obtained in the step S2 into a carbonization furnace, and carbonizing at 550 ℃ under the condition of no or little oxygen; the concrete process is that the column raw material is sent into a carbonization hopper through a rubber belt conveyor, and is evenly added into a carbonization furnace through a spiral guide plate, and a stir-frying plate is arranged in the furnace and has a certain gradient (generally 3 degrees). When the furnace runs, the furnace body rotates at a certain speed, the materials are dispersed and flow to the discharge port at a certain speed due to the action of gravity and the stir-frying plate, the materials are reversely contacted with high-temperature flue gas generated by combustion in the flowing process, the temperature is gradually increased to achieve uniform carbonization, and the materials are discharged from the discharge port, so that columnar clinker is obtained.
The main factors affecting carbonization are as follows:
(1) Carbonization temperature
Too low carbonization temperature will cause insufficient carbonization degree, too high carbonization temperature, too low volatile content of carbonized material, and difficulty in ensuring normal operation of activation reaction. The carbonization temperature is generally 550-650 ℃.
(2) Heating rate of carbonization
The heating rate of carbonization is too high, and the decomposition of biomass charcoal and tar is extremely severe, so that a proper pore structure is difficult to form. If the heating rate of carbonization is too low, the skeleton of carbonized material cannot be completely formed, and the strength is poor.
(3) Influence of charring atmosphere
Anaerobic or less oxygen is the condition for preparing qualified carbonized material. The existence of oxygen can oxidize and burn raw materials, and influence the void structure, strength and yield of carbonized materials.
S4: conveying the columnar clinker obtained in the step S3 to a rotary cremator, sequentially preheating and drying at 500 ℃, deep carbonization at 700 ℃ and activation at 800 ℃, and cooling to 400 ℃ in a cooling section to form a specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram; the columnar raw material after qualified carbonization is sent into a rotary activation furnace, the rotary activation furnace is used as fuel with gas fuel or heavy oil, and high-temperature flue gas generated by combustion is mixed with water vapor to be used as an activating agent. The carbonized material is continuously added into the furnace through a charging device, slowly moves from the furnace tail to the furnace head along the direction of the gradient of the furnace body (the installation gradient of the furnace body is 1 DEG), sequentially passes through the preheating and drying at 500 ℃, the deep carbonization at 700 ℃ and the activation at 800 ℃, and is discharged out of the furnace body through a spiral pipe discharger after the cooling section is cooled to 400 ℃ to obtain 965kg qualified activated carbon products. The mass ratio of the water vapor to the columnar clinker is 8:1, the activation time was 30 minutes.
S5: in order to make the activated carbon obtained by activation have higher quality, the activated carbon obtained by S4 is subjected to deashing treatment by using an acid washing process, wherein the main equipment of the acid washing process comprises an enamel reaction kettle or a rubber lining reaction kettle and other acid-resistant equipment. The activated product is soaked in dilute hydrochloric acid solution, heated, stirred, rinsed to be neutral by hot clear water and then dried. In this process, steam at a certain pressure is used as a heat source and power for stirring. The wet activated carbon is generally dried by a rotary furnace to obtain the specific surface area 1089m 2 Activated carbon product/g.
Example two
According to the method shown in fig. 1, the invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following specific steps:
step one: mud kneading stage of wave-absorbing material
625kg of wave-absorbing material is metered and then is put into a jet mill for grinding, and the powder is kneaded after being finely ground into the particle size of less than 180 meshes in a powder making machine. The kneading is to uniformly mix the wave-absorbing material with water and additives, and send the formed slurry into a stirrer, and the stirring process is not only for uniformly mixing the wave-absorbing slurry, but also has the function of enabling the slurry to undergo strong shearing in the stirring process, and improving the rheological property of the slurry due to the action between the additives and the surface of the wave-absorbing material. The prepared slurry is conveyed to a sprayer for standby in the surface spraying process through a slurry pump. Wherein the solid content in the slurry is 45.6%, and the additive is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
Step two: spraying stage of cotton stalk surface
12500kg of cotton straw is subjected to beating and pressing, sand is blown off by air, the cotton straw is conveyed to a slicing process, the cotton straw is cut into blocks with the diameter of 10 mm-15 mm, the cotton straw blocks are conveyed to a surface spraying process and contacted with 1370kg of atomized slurry with the solid content of 45.6% sprayed by a sprayer which is pumped from slurry to the surface spraying process, and the mixture is subjected to a uniform mixing process to uniformly mix the cotton straw with the basic surface of the slurry, so that a reaction material is formed.
Step three: stage of microwave pyrolysis reaction
The reaction materials are conveyed into a high-level bin of a microwave pyrolysis process through a large-inclination-angle belt conveyor, and enter the microwave pyrolysis reaction device to carry out pyrolysis reaction through the automatic control of a metering device arranged at the bottom of the high-level bin according to the material level of the microwave pyrolysis reaction device. The microwave pyrolysis reaction device is operated under the condition that the reaction temperature is 350 ℃ and the operating pressure is 7KPa micro positive pressure. The reaction energy is generated by a microwave generator and is fed into a resonant cavity of the microwave pyrolysis reaction device through a waveguide pipeline, so that the materials in the microwave pyrolysis reaction device are directly heated, and the microwaves have a 'non-thermal effect' on the high polymer. The dual heating effect makes the material heating speed fast and the efficiency high. The double heating effect can quickly dissociate high molecular substances into gas products of low molecular chains.
Step four: solid, liquid and gas separation stage
The gas output from the gas outlet in the microwave cracking reaction device firstly passes through an electrostatic oil catcher to remove a small amount of tar in the gas, then passes through a cooler to cool the gas to below 100 ℃, then condenses the condensable gas into a liquid phase when condensed by a condenser, and the liquid separated from the gas and the liquid is wood vinegar, which is also called plant acid, and is a reddish brown mixture containing various organic matters such as acid, alcohol, phenol, ketone and the like. Wood vinegar is widely used in chemical industry, forestry, agriculture, animal husbandry, food processing industry and medical and health industry.
The non-condensable gas obtained after cooling and condensing is the mixed gas (wherein the components of the mixed gas are H) 2 26.53%, CO 18.96%, CH 4 15.58%, CO 2 36.89% by volume of other gases, 2.04% by volume of other gases) to be fed to the synthesis of natural gas.
3831kg of biomass charcoal formed through the microwave pyrolysis reaction is deposited at the bottom of the microwave pyrolysis reaction device, is discharged through a biomass charcoal discharging machine arranged at an oblique outlet at the bottom, and enters a summarizing spiral discharging machine through program control.
Step five: natural gas synthesis stage
S1: 3560Nm of the mixed gas obtained in the fourth step 3 The gas is compressed to 2.4MPa and the temperature is reduced to 28 ℃;
s2: the gas obtained in the step S1 is subjected to CO shift reaction under the condition of shift pressure of 2.35MPa and shift temperature of 400 ℃, and the shift main reaction is as follows:
CO+H 2 O＝H 2 +CO 2
the shift adopts a sulfur-tolerant shift catalyst with the model number of B303Q;
s3: carrying out dry desulfurization on the gas obtained in the step S2 under the condition of desulfurization pressure of 2.35MPa and desulfurization temperature of 320 ℃, wherein zinc oxide with the model of T306 is selected as a dry desulfurizing agent, so that H in the desulfurized gas 2 The S content is less than or equal to 0.1PPm, and meets the requirement of methane synthesis reaction.
S4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 2.25MPa and the adsorption temperature is less than or equal to 40 ℃ so as to ensure that CO in the gas subjected to PSA decarbonization 2 Removing, thereby makingThe obtained gas meets the requirement of synthesis reaction, and comprises the following components: h 2 59.09%, CO 16.32%, CH 4 25.14%, CO 2 1.46%, wherein the percentages are by volume, the molar ratio of hydrogen to carbon (H 2 -CO 2 )/(CO+CO 2 ) =3.13. Wherein the CO is resolved 2 2238kg of liquid CO is obtained after purification 2 。
S5: 2206.27Nm obtained in S4 3 Pressurizing the gas to 3.5MPa for the second time, heating to 350 ℃, and then sending the gas into a methanation reactor for methanation treatment, wherein the main reaction of methanation is as follows:
CO+3H 2 ＝CH 4 +H 2 O+Q,
CO2+4H 2 ＝CH 4 +2H 2 O+Q
The methanation treatment adopts Topsoe (TREMPTM) methanation process, and adopts a catalyst with the model of MCR-2X to ensure that CH in the methanated gas 4 The content reaches more than 98 percent.
S6: and (3) reducing the pressure of the gas obtained in the step (S5) to 1.7MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption dehydration process under pressure, wherein molecular sieves, silica gel and the like are selected as adsorbents. The qualified natural gas flow obtained after dehydration treatment is 927.7Nm 3 The methane content is above 98.6%, the gas dew point is below-40 ℃, and the remote transportation of the pressure pipeline is convenient.
Step six: stage of activated carbon preparation
S1: carrying out natural cooling on 3831kg of biomass charcoal obtained in the fourth step to normal temperature, and then conveying to Raymond mill machine-made powder, so that the granularity of the biomass charcoal powder after powder preparation is smaller than 200 meshes;
s2: fully and uniformly mixing the biomass charcoal powder obtained in the step S1 with coal tar added in proportion under the condition of a kneading temperature of 85 ℃ and a kneading time of 16min by using a screw mixer, then feeding the mixture into a screw extruder to extrude cylindrical strips, and drying to form column raw materials;
s3: delivering the columnar raw material obtained in the step S2 into a carbonization furnace, and carbonizing at the carbonization temperature of 620 ℃ under the condition of no or little oxygen; the concrete process is that the column raw material is sent into a carbonization hopper through a rubber belt conveyor, and is evenly added into a carbonization furnace through a spiral guide plate, and a stir-frying plate is arranged in the furnace and has a certain gradient (generally 3 degrees). When the furnace runs, the furnace body rotates at a certain speed, the materials are dispersed and flow to the discharge port at a certain speed due to the action of gravity and the stir-frying plate, the materials are reversely contacted with high-temperature flue gas generated by combustion in the flowing process, the temperature is gradually increased to achieve uniform carbonization, and the materials are discharged from the discharge port, so that columnar clinker is obtained.
The main factors affecting carbonization are as follows:
(1) carbonization temperature
Too low carbonization temperature will cause insufficient carbonization degree, too high carbonization temperature, too low volatile content of carbonized material, and difficulty in ensuring normal operation of activation reaction. The carbonization temperature is generally 550-650 ℃.
(2) Heating rate of carbonization
The heating rate of carbonization is too high, and the decomposition of biomass charcoal and tar is extremely severe, so that a proper pore structure is difficult to form. If the heating rate of carbonization is too low, the skeleton of carbonized material cannot be completely formed, and the strength is poor.
(3) Influence of charring atmosphere
Anaerobic or less oxygen is the condition for preparing qualified carbonized material. The existence of oxygen can oxidize and burn raw materials, and influence the void structure, strength and yield of carbonized materials.
S4: conveying the columnar clinker obtained in the step S3 to a rotary cremator, sequentially preheating and drying at 560 ℃, deep carbonization at 700 ℃ and activation at 850 ℃, and cooling to 400 ℃ in a cooling section to form a specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram; the columnar raw material after qualified carbonization is sent into a rotary activation furnace, the rotary activation furnace is used as fuel with gas fuel or heavy oil, and high-temperature flue gas generated by combustion is mixed with water vapor to be used as an activating agent. The carbonized material is continuously added into the furnace through a charging device, slowly moves from the furnace tail to the furnace end along the direction of the furnace body gradient (the furnace body installation gradient is 1 DEG), and sequentially passes through the preheating and drying at 560 ℃, the deep carbonization at 700 ℃, the activation at 850 ℃ and the cooling section Cooling to 400 ℃, discharging the product from the furnace body through a spiral pipe discharger to obtain 1050kg of qualified activated carbon product. The mass ratio of water vapor to the pillar clinker is 8.5:1, the activation time was 45 minutes.
S5: in order to make the activated carbon obtained by activation have higher quality, the activated carbon obtained by S4 is subjected to deashing treatment by using an acid washing process, wherein the main equipment of the acid washing process comprises an enamel reaction kettle or a rubber lining reaction kettle and other acid-resistant equipment. The activated product is soaked in dilute hydrochloric acid solution, heated, stirred, rinsed to be neutral by hot clear water and then dried. In this process, steam at a certain pressure is used as a heat source and power for stirring. The wet activated carbon is generally dried by a rotary furnace to obtain the specific surface area 966.3m 2 Activated carbon product/g.
Example III
According to the method shown in fig. 1, the invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following specific steps:
step one: mud kneading stage of wave-absorbing material
900kg of wave-absorbing material is metered and then is put into an airflow crusher for grinding, and the powder is kneaded after being finely ground into the particle size of less than 180 meshes in a powder making machine. The kneading is to uniformly mix the wave-absorbing material with water and additives, and send the formed slurry into a stirrer, and the stirring process is not only for uniformly mixing the wave-absorbing slurry, but also has the function of enabling the slurry to undergo strong shearing in the stirring process, and improving the rheological property of the slurry due to the action between the additives and the surface of the wave-absorbing material. The prepared slurry is conveyed to a sprayer for standby in the surface spraying process through a slurry pump. Wherein the solid content in the slurry is 50.2%, and the additive is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
Step two: spraying stage of cotton stalk surface
15000kg cotton straw is subjected to beating and pressing, sand is blown off by air, the cotton straw is conveyed to a slicing process, the cotton straw is cut into blocks with the diameter of 10 mm-15 mm, the cotton straw blocks are conveyed to a surface spraying process and contacted with 1793kg atomized slurry with the solid content of 50.2% sprayed by a sprayer which is pumped from slurry to the surface spraying process, and the mixture is subjected to a uniform mixing process to uniformly mix the cotton straw with the basic surface of the slurry, so that a reaction material is formed.
Step three: stage of microwave pyrolysis reaction
The reaction materials are conveyed into a high-level bin of a microwave pyrolysis process through a large-inclination-angle belt conveyor, and enter the microwave pyrolysis reaction device to carry out pyrolysis reaction through the automatic control of a metering device arranged at the bottom of the high-level bin according to the material level of the microwave pyrolysis reaction device. The microwave pyrolysis reaction device is operated under the micro-positive pressure state with the reaction temperature of 450 ℃ and the operating pressure of 6.5 KPa. The reaction energy is generated by a microwave generator and is fed into a resonant cavity of the microwave pyrolysis reaction device through a waveguide pipeline, so that the materials in the microwave pyrolysis reaction device are directly heated, and the microwaves have a 'non-thermal effect' on the high polymer. The dual heating effect makes the material heating speed fast and the efficiency high. The double heating effect can quickly dissociate high molecular substances into gas products of low molecular chains.
Step four: solid, liquid and gas separation stage
The gas output from the gas outlet in the microwave cracking reaction device firstly passes through an electrostatic oil catcher to remove a small amount of tar in the gas, then passes through a cooler to cool the gas to below 100 ℃, then condenses the condensable gas into a liquid phase when condensed by a condenser, and the liquid separated from the gas and the liquid is wood vinegar, which is also called plant acid, and is a reddish brown mixture containing various organic matters such as acid, alcohol, phenol, ketone and the like. Wood vinegar is widely used in chemical industry, forestry, agriculture, animal husbandry, food processing industry and medical and health industry.
The non-condensable gas obtained after cooling and condensing is the mixed gas (wherein the components of the mixed gas are H) 2 25.02%, CO 19.72%, CH 4 16.76%, CO 2 36.7% of other gases, 1.80% of which are by volume), to be sent to synthesis of natural gas.
4815kg of biomass charcoal formed through the microwave pyrolysis reaction is deposited at the bottom of the microwave pyrolysis reaction device, is discharged through a biomass charcoal discharging machine arranged at an oblique outlet at the bottom, and enters a summarizing spiral discharging machine through program control.
Step five: natural gas synthesis stage
S1: 4118Nm of the mixed gas obtained in the fourth step 3 The gas compression process is carried out, the gas is compressed to 2.3MPa, and the temperature is reduced to 28 ℃;
s2: the gas obtained in the step S1 is subjected to CO shift reaction under the condition of shift pressure of 2.25MPa and shift temperature of 380 ℃, and the shift main reaction is as follows:
CO+H 2 O＝H 2 +CO 2
the shift adopts a sulfur-tolerant shift catalyst with the model number of B301;
s3: carrying out dry desulfurization on the gas obtained in the step S2 under the condition of desulfurization pressure of 2.26MPa and desulfurization temperature of 390 ℃, wherein zinc oxide with the model of T305 is selected as a dry desulfurizing agent, so that H in the desulfurized gas 2 The S content is less than or equal to 0.1PPm, and meets the requirement of methane synthesis reaction.
S4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 2.20MPa and the adsorption temperature is less than or equal to 40 ℃ so as to ensure that CO in the gas subjected to PSA decarbonization 2 The removal of the gas, so that the obtained gas meets the requirement of synthesis reaction, and the composition components are as follows: h 2 55.72%, CO 15.92%, CH 4 26.84%, CO 2 1.52%, wherein the percentages are by volume, the molar ratio of hydrogen to carbon (H 2 -CO 2 )/(CO+CO 2 ) =3.11. Wherein the CO is resolved 2 2631kg of liquid CO is obtained after purification 2 。
S5: 2571.6Nm obtained in S4 3 Pressurizing the gas to 3.4MPa for the second time, heating to 345 ℃, and then sending the gas into a methanation reactor for methanation treatment, wherein the main reaction of methanation is as follows:
CO+3H 2 ＝CH 4 +H 2 O+Q
CO 2 +4H 2 ＝CH4+2H 2 O+Q
The methanation treatment adopts a CRG methanation process of Drvy company in England, and a catalyst with the model of CEG-LH is selected to ensure that CH in the methanated gas 4 The content reaches more than 98 percent.
S6: and (3) reducing the pressure of the gas obtained in the step (S5) to 1.8MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption dehydration process under pressure, wherein molecular sieves, silica gel and the like are selected as adsorbents. The qualified natural gas flow obtained after dehydration treatment is 1115.8Nm 3 The methane content is above 98.7%, the gas dew point is below-40 ℃, and the remote transportation of the pressure pipeline is convenient.
Step six: stage of activated carbon preparation
S1: naturally cooling 4815kg of biomass charcoal obtained in the step four to normal temperature, and then conveying to Raymond mill machine-made powder, so that the granularity of the biomass charcoal powder after powder preparation is smaller than 200 meshes;
s2: fully and uniformly mixing the biomass charcoal powder obtained in the step S1 with coal tar added in proportion under the condition of a kneading temperature of 75 ℃ and a kneading time of 18min by using a screw mixer, then feeding the mixture into a screw extruder to extrude cylindrical strips, and drying to form columnar raw materials;
s3: delivering the columnar raw material obtained in the step S2 into a carbonization furnace, and carbonizing at the carbonization temperature of 580 ℃ under the condition of no or less oxygen; the concrete process is that the column raw material is sent into a carbonization hopper through a rubber belt conveyor, and is evenly added into a carbonization furnace through a spiral guide plate, and a stir-frying plate is arranged in the furnace and has a certain gradient (generally 3 degrees). When the furnace runs, the furnace body rotates at a certain speed, the materials are dispersed and flow to the discharge port at a certain speed due to the action of gravity and the stir-frying plate, the materials are reversely contacted with high-temperature flue gas generated by combustion in the flowing process, the temperature is gradually increased to achieve uniform carbonization, and the materials are discharged from the discharge port, so that columnar clinker is obtained.
The main factors affecting carbonization are as follows:
(1) carbonization temperature
Too low carbonization temperature will cause insufficient carbonization degree, too high carbonization temperature, too low volatile content of carbonized material, and difficulty in ensuring normal operation of activation reaction. The carbonization temperature is generally 550-650 ℃.
(2) Heating rate of carbonization
The heating rate of carbonization is too high, and the decomposition of biomass charcoal and tar is extremely severe, so that a proper pore structure is difficult to form. If the heating rate of carbonization is too low, the skeleton of carbonized material cannot be completely formed, and the strength is poor.
(3) Influence of charring atmosphere
Anaerobic or less oxygen is the condition for preparing qualified carbonized material. The existence of oxygen can oxidize and burn raw materials, and influence the void structure, strength and yield of carbonized materials.
S4: conveying the columnar clinker obtained in the step S3 to a rotary cremator, sequentially preheating and drying at 575 ℃, deep carbonization at 700 ℃ and activation at 900 ℃, and cooling to 400 ℃ in a cooling section to form a specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram; the columnar raw material after qualified carbonization is sent into a rotary activation furnace, the rotary activation furnace is used as fuel with gas fuel or heavy oil, and high-temperature flue gas generated by combustion is mixed with water vapor to be used as an activating agent. The carbonized material is continuously added into the furnace through a charging device, slowly moves from the furnace tail to the furnace head along the direction of the gradient of the furnace body (the installation gradient of the furnace body is 1 DEG), sequentially passes through the preheating and drying at 575 ℃, the deep carbonization at 700 ℃ and the activation at 900 ℃, and is discharged out of the furnace body through a spiral pipe discharger after the cooling section is cooled to 400 ℃ to obtain 1050kg qualified activated carbon products. The mass ratio of the water vapor to the columnar clinker is 9:1, the activation time was 38 minutes.
S5: in order to make the activated carbon obtained by activation have higher quality, the activated carbon obtained by S4 is subjected to deashing treatment by using an acid washing process, wherein the main equipment of the acid washing process comprises an enamel reaction kettle or a rubber lining reaction kettle and other acid-resistant equipment. The activated product is soaked in dilute hydrochloric acid solution, heated, stirred, rinsed to be neutral by hot clear water and then dried. In this process, steam at a certain pressure is used as a heat source and power for stirring. The wet activated carbon is generally dried by a rotary furnace to obtain a comparison tableArea 1020.5m 2 Activated carbon product/g.
Example IV
According to the method shown in fig. 1, the invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following specific steps:
step one: mud kneading stage of wave-absorbing material
600kg of wave-absorbing material is metered and then is put into an airflow crusher for grinding, and the powder is kneaded after being finely ground into the particle size of less than 180 meshes in a powder making machine. The kneading is to uniformly mix the wave-absorbing material with water and additives, and send the formed slurry into a stirrer, and the stirring process is not only for uniformly mixing the wave-absorbing slurry, but also has the function of enabling the slurry to undergo strong shearing in the stirring process, and improving the rheological property of the slurry due to the action between the additives and the surface of the wave-absorbing material. The prepared slurry is conveyed to a sprayer for standby in the surface spraying process through a slurry pump. Wherein the solid content in the slurry is 39.7%, and the additive is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
Step two: spraying stage of cotton stalk surface
15000kg of cotton straw is subjected to beating and pressing, sand is blown off by air, the cotton straw is conveyed to a slicing process, the cotton straw is cut into blocks with the diameter of 10 mm-15 mm, the cotton straw blocks are conveyed to a surface spraying process and contacted with 1511kg of atomized slurry with the solid content of 39.7% sprayed by a sprayer which is pumped from slurry to the surface spraying process, and the mixture is subjected to a uniform mixing process to uniformly mix the cotton straw with the basic surface of the slurry, so that a reaction material is formed.
Step three: stage of microwave pyrolysis reaction
The reaction materials are conveyed into a high-level bin of a microwave pyrolysis process through a large-inclination-angle belt conveyor, and enter the microwave pyrolysis reaction device to carry out pyrolysis reaction through the automatic control of a metering device arranged at the bottom of the high-level bin according to the material level of the microwave pyrolysis reaction device. The microwave pyrolysis reaction device is operated under the micro-positive pressure state with the reaction temperature of 550 ℃ and the operating pressure of 7.2 KPa. The reaction energy is generated by a microwave generator and is fed into a resonant cavity of the microwave pyrolysis reaction device through a waveguide pipeline, so that the materials in the microwave pyrolysis reaction device are directly heated, and the microwaves have a 'non-thermal effect' on the high polymer. The dual heating effect makes the material heating speed fast and the efficiency high. The double heating effect can quickly dissociate high molecular substances into gas products of low molecular chains.
Step four: solid, liquid and gas separation stage
The gas output from the gas outlet in the microwave cracking reaction device firstly passes through an electrostatic oil catcher to remove a small amount of tar in the gas, then passes through a cooler to cool the gas to below 100 ℃, then condenses the condensable gas into a liquid phase when condensed by a condenser, and the liquid separated from the gas and the liquid is wood vinegar, which is also called plant acid, and is a reddish brown mixture containing various organic matters such as acid, alcohol, phenol, ketone and the like. Wood vinegar is widely used in chemical industry, forestry, agriculture, animal husbandry, food processing industry and medical and health industry.
The non-condensable gas obtained after cooling and condensing is the mixed gas (wherein the components of the mixed gas are H) 2 25.02%, CO 23.35%, CH 4 15.95%, CO 2 26.29% and 2.10% of other gases, wherein the percentages are by volume) are sent to synthesis of natural gas.
4215kg biomass charcoal formed through the microwave pyrolysis reaction is deposited at the bottom of the microwave pyrolysis reaction device, is discharged through a biomass charcoal discharging machine arranged at an oblique outlet at the bottom, and enters a summarizing spiral discharging machine through program control, and because the summarizing spiral discharging machine is provided with a cooling device, the biomass charcoal can be cooled to below 200 ℃ and then conveyed to the outlet, and enters a biomass charcoal transport vehicle to be transported to prepare activated charcoal.
Step five: natural gas synthesis stage
S1: 5099Nm of the mixed gas obtained in the step four 3 The gas compression process is carried out, the gas is compressed to 2.6MPa, and the temperature is reduced to 28 ℃;
s2: the gas obtained in the step S1 is subjected to CO shift reaction under the condition of shift pressure of 2.55MPa and shift temperature of 375 ℃, and the shift main reaction is as follows:
CO+H 2 O＝H 2 +CO 2
the shift adopts a sulfur-tolerant shift catalyst with the model number of B303Q;
s3: carrying out dry desulfurization on the gas obtained in the step S2 under the condition of desulfurization pressure of 2.50MPa and desulfurization temperature of 320 ℃, wherein zinc oxide with the model of T306 is selected as a dry desulfurizing agent, so that H in the desulfurized gas 2 The S content is less than or equal to 0.1PPm, and meets the requirement of methane synthesis reaction.
S4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 2.40MPa and the adsorption temperature is less than or equal to 40 ℃ so as to ensure that CO in the gas subjected to PSA decarbonization 2 The removal of the gas, so that the obtained gas meets the requirement of synthesis reaction, and the composition components are as follows: h 2 59.74%, CO 16.83%, CH 4 21.94%, CO 2 1.48%, wherein the percentages are by volume, the molar ratio of hydrogen to carbon (H 2 -CO 2 )/(CO+CO 2 ) =3.18. Wherein the CO is resolved 2 Purifying to obtain 2622kg of liquid CO 2 。
S5: 3706.35Nm obtained in S4 3 Pressurizing the gas to 3.6MPa for the second time, heating to 350 ℃, and then sending the gas into a methanation reactor for methanation treatment, wherein the main reaction of methanation is as follows:
CO+3H 2 ＝CH 4 +H 2 O+Q
CO 2 +4H 2 ＝CH 4 +2H 2 O+Q
The methanation treatment adopts Topsoe (TREMPTM) methanation process, and adopts a catalyst with the model of MCR-2X to ensure that CH in the methanated gas 4 The content reaches more than 98 percent.
S6: and (3) reducing the pressure of the gas obtained in the step (S5) to 1.8MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption dehydration process under pressure, wherein molecular sieves, silica gel and the like are selected as adsorbents. The qualified natural gas flow obtained after dehydration treatment is 1462Nm 3 The methane content is above 98.6%, the gas dew point is below-40 ℃, and the remote transportation of the pressure pipeline is convenient.
Step six: stage of activated carbon preparation
S1: naturally cooling 4215kg of biomass charcoal obtained in the fourth step to normal temperature, and then conveying to Raymond mill machine-made powder, so that the granularity of the biomass charcoal powder after powder preparation is smaller than 200 meshes;
s2: fully and uniformly mixing the biomass charcoal powder obtained in the step S1 with coal tar added in proportion under the condition of a kneading temperature of 80 ℃ and a kneading time of 18min by using a screw mixer, then feeding the mixture into a screw extruder to extrude cylindrical strips, and drying to form columnar raw materials;
s3: delivering the columnar raw material obtained in the step S2 into a carbonization furnace, and carbonizing at the carbonization temperature of 600 ℃ under the condition of no or little oxygen; the concrete process is that the column raw material is sent into a carbonization hopper through a rubber belt conveyor, and is evenly added into a carbonization furnace through a spiral guide plate, and a stir-frying plate is arranged in the furnace and has a certain gradient (generally 3 degrees). When the furnace runs, the furnace body rotates at a certain speed, the materials are dispersed and flow to the discharge port at a certain speed due to the action of gravity and the stir-frying plate, the materials are reversely contacted with high-temperature flue gas generated by combustion in the flowing process, the temperature is gradually increased to achieve uniform carbonization, and the materials are discharged from the discharge port, so that columnar clinker is obtained.
The main factors affecting carbonization are as follows:
(1) carbonization temperature
Too low carbonization temperature will cause insufficient carbonization degree, too high carbonization temperature, too low volatile content of carbonized material, and difficulty in ensuring normal operation of activation reaction. The carbonization temperature is generally 550-650 ℃.
(2) Heating rate of carbonization
The heating rate of carbonization is too high, and the decomposition of biomass charcoal and tar is extremely severe, so that a proper pore structure is difficult to form. If the heating rate of carbonization is too low, the skeleton of carbonized material cannot be completely formed, and the strength is poor.
(3) Influence of charring atmosphere
Anaerobic or less oxygen is the condition for preparing qualified carbonized material. The existence of oxygen can oxidize and burn raw materials, and influence the void structure, strength and yield of carbonized materials.
S4: conveying the columnar clinker obtained in the step S3 to a rotary cremator, sequentially preheating and drying at 550 ℃, deep carbonization at 700 ℃ and activation at 875 ℃, and cooling to 400 ℃ in a cooling section to form the specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram; the columnar raw material after qualified carbonization is sent into a rotary activation furnace, the rotary activation furnace is used as fuel with gas fuel or heavy oil, and high-temperature flue gas generated by combustion is mixed with water vapor to be used as an activating agent. The carbonized material is continuously added into the furnace through a charging device, slowly moves from the furnace tail to the furnace head along the direction of the gradient of the furnace body (the installation gradient of the furnace body is 1 DEG), sequentially passes through the preheating and drying at 550 ℃, the deep carbonization at 700 ℃ and the activation at 875 ℃, and is discharged out of the furnace body through a spiral pipe discharger after the cooling section is cooled to 400 ℃ to obtain 998kg of qualified activated carbon products. The mass ratio of the water vapor to the columnar clinker is 9:1, the activation time was 40 minutes.
S5: in order to make the activated carbon obtained by activation have higher quality, the activated carbon obtained by S4 is subjected to deashing treatment by using an acid washing process, wherein the main equipment of the acid washing process comprises an enamel reaction kettle or a rubber lining reaction kettle and other acid-resistant equipment. The activated product is soaked in dilute hydrochloric acid solution, heated, stirred, rinsed to be neutral by hot clear water and then dried. In this process, steam at a certain pressure is used as a heat source and power for stirring. The wet activated carbon is generally dried by a rotary furnace to obtain the specific surface area 1010.63m 2 Activated carbon product/g.
Example five
According to the method shown in fig. 1, the invention provides a method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis, which comprises the following specific steps:
step one: mud kneading stage of wave-absorbing material
12000kg of wave-absorbing material is metered and then is put into a jet mill for grinding, and the powder is finely ground in a powder making machine until the granularity is smaller than 180 meshes, and then kneading treatment is carried out. The kneading is to uniformly mix the wave-absorbing material with water and additives, and send the formed slurry into a stirrer, and the stirring process is not only for uniformly mixing the wave-absorbing slurry, but also has the function of enabling the slurry to undergo strong shearing in the stirring process, and improving the rheological property of the slurry due to the action between the additives and the surface of the wave-absorbing material. The prepared slurry is conveyed to a sprayer for standby in the surface spraying process through a slurry pump. Wherein the solid content in the slurry is 58.5%, and the additive is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
Step two: spraying stage of cotton stalk surface
15000kg of cotton straw is subjected to beating and pressing, sand is blown off by air, the cotton straw is conveyed to a slicing process, the cotton straw is cut into blocks with the diameter of 10 mm-15 mm, the cotton straw blocks are conveyed to a surface spraying process and contacted with 20512.9kg of atomized slurry with the solid content of 58.5% sprayed by a sprayer which is pumped from slurry to the surface spraying process, and the mixture is subjected to a uniform mixing process to uniformly mix the cotton straw with the basic surface of the slurry, so that a reaction material is formed.
Step three: stage of microwave pyrolysis reaction
The reaction materials are conveyed into a high-level bin of a microwave pyrolysis process through a large-inclination-angle belt conveyor, and enter the microwave pyrolysis reaction device to carry out pyrolysis reaction through the automatic control of a metering device arranged at the bottom of the high-level bin according to the material level of the microwave pyrolysis reaction device. The microwave pyrolysis reaction device is operated under the micro-positive pressure state with the reaction temperature of 750 ℃ and the operating pressure of 8 KPa. The reaction energy is generated by a microwave generator and is fed into a resonant cavity of the microwave pyrolysis reaction device through a waveguide pipeline, so that the materials in the microwave pyrolysis reaction device are directly heated, and the microwaves have a 'non-thermal effect' on the high polymer. The dual heating effect makes the material heating speed fast and the efficiency high. The double heating effect can quickly dissociate high molecular substances into gas products of low molecular chains.
Step four: solid, liquid and gas separation stage
The gas output from the gas outlet in the microwave cracking reaction device firstly passes through an electrostatic oil catcher to remove a small amount of tar in the gas, then passes through a cooler to cool the gas to below 100 ℃, then condenses the condensable gas into a liquid phase when condensed by a condenser, and the liquid separated from the gas and the liquid is wood vinegar, which is also called plant acid, and is a reddish brown mixture containing various organic matters such as acid, alcohol, phenol, ketone and the like. Wood vinegar is widely used in chemical industry, forestry, agriculture, animal husbandry, food processing industry and medical and health industry.
The non-condensable gas obtained after cooling and condensing is the mixed gas (wherein the components of the mixed gas are H) 2 35.02%, CO 24.00%, CH 4 15.00%, CO 2 24.88% and 1.10% of other gases, wherein the percentages are by volume) are sent to synthesis of natural gas.
4210kg of biomass charcoal formed through the microwave pyrolysis reaction is deposited at the bottom of the microwave pyrolysis reaction device, is discharged through a biomass charcoal discharging machine arranged at an oblique outlet at the bottom, and enters a summarizing spiral discharging machine through program control.
Step five: natural gas synthesis stage
S1: 5571Nm of mixed gas obtained in the step four 3 The gas compression process is carried out, the gas is compressed to 3.0MPa, and the temperature is reduced to 45 ℃;
s2: the gas obtained in the step S1 is subjected to CO shift reaction under the condition of shift pressure of 2.5MPa and shift temperature of 470 ℃, and the shift main reaction is as follows:
CO+H 2 O＝H 2 +CO 2
the shift adopts a sulfur-tolerant shift catalyst with the model number of B303Q;
s3: carrying out dry desulfurization on the gas obtained in the step S2 under the condition of desulfurization pressure of 2.9MPa and desulfurization temperature of 400 ℃, wherein zinc oxide with the model of T306 is selected as a dry desulfurizing agent, so that H in the desulfurized gas 2 The S content is less than or equal to 0.1PPm, and meets the requirement of methane synthesis reaction.
S4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 2.8MPa and the adsorption temperature is less than or equal to 40 ℃ so as to ensure that CO in the gas subjected to PSA decarbonization 2 The removal of the gas, so that the obtained gas meets the requirement of synthesis reaction, and the composition components are as follows: h 2 61.23%, CO 17.49%, CH 4 20.00%, CO 2 1.25% by volume, hydrogen to carbon molar ratio (H 2 -CO 2 )/(CO+CO 2 ) =3.2. Wherein the CO is resolved 2 After purification 2740kg of liquid CO is obtained 2 。
S5: 4172.75Nm obtained in S4 3 Pressurizing the gas to 4.5MPa for the second time, heating to 500 ℃, and then sending the gas into a methanation reactor for methanation treatment, wherein the main reaction of methanation is as follows:
CO+3H 2 ＝CH 4 +H 2 O+Q
CO 2 +4H 2 ＝CH 4 +2H 2 O+Q
The methanation treatment adopts Topsoe (TREMPTM) methanation process, and adopts a catalyst with the model of MCR-2X to ensure that CH in the methanated gas 4 The content reaches more than 98 percent.
S6: and (3) reducing the pressure of the gas obtained in the step (S5) to 1.9MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption dehydration process under pressure, wherein molecular sieves, silica gel and the like are selected as adsorbents. The qualified natural gas flow obtained after dehydration treatment is 1585.3Nm 3 The methane content is above 98.7%, the gas dew point is below-40 ℃, and the remote transportation of the pressure pipeline is convenient.
Step six: stage of activated carbon preparation
S1: naturally cooling 4210kg of biomass charcoal obtained in the fourth step to normal temperature, and then conveying to Raymond mill machine-made powder, so that the granularity of the biomass charcoal powder after powder preparation is smaller than 200 meshes;
s2: fully and uniformly mixing the biomass charcoal powder obtained in the step S1 with coal tar under the condition of kneading temperature of 90 ℃ and kneading time of 20min by using a screw mixer, then feeding the mixture into a screw extruder to extrude cylindrical strips, and drying to form columnar raw materials;
s3: delivering the columnar raw material obtained in the step S2 into a carbonization furnace, and carbonizing at the carbonization temperature of 650 ℃ under the condition of no or less oxygen; the concrete process is that the column raw material is sent into a carbonization hopper through a rubber belt conveyor, and is evenly added into a carbonization furnace through a spiral guide plate, and a stir-frying plate is arranged in the furnace and has a certain gradient (generally 3 degrees). When the furnace runs, the furnace body rotates at a certain speed, the materials are dispersed and flow to the discharge port at a certain speed due to the action of gravity and the stir-frying plate, the materials are reversely contacted with high-temperature flue gas generated by combustion in the flowing process, the temperature is gradually increased to achieve uniform carbonization, and the materials are discharged from the discharge port, so that columnar clinker is obtained.
The main factors affecting carbonization are as follows:
(1) carbonization temperature
Too low carbonization temperature will cause insufficient carbonization degree, too high carbonization temperature, too low volatile content of carbonized material, and difficulty in ensuring normal operation of activation reaction. The carbonization temperature is generally 550-650 ℃.
(2) Heating rate of carbonization
The heating rate of carbonization is too high, and the decomposition of biomass charcoal and tar is extremely severe, so that a proper pore structure is difficult to form. If the heating rate of carbonization is too low, the skeleton of carbonized material cannot be completely formed, and the strength is poor.
(3) Influence of charring atmosphere
Anaerobic or less oxygen is the condition for preparing qualified carbonized material. The existence of oxygen can oxidize and burn raw materials, and influence the void structure, strength and yield of carbonized materials.
S4: conveying the columnar clinker obtained in the step S3 to a rotary cremator, sequentially preheating and drying at 600 ℃, deep carbonization at 700 ℃ and activation at 950 ℃, and cooling to 400 ℃ in a cooling section to form a specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram; the columnar raw material after qualified carbonization is sent into a rotary activation furnace, the rotary activation furnace is used as fuel with gas fuel or heavy oil, and high-temperature flue gas generated by combustion is mixed with water vapor to be used as an activating agent. The carbonized material is continuously added into the furnace through a charging device, slowly moves from the furnace tail to the furnace end along the direction of the furnace body gradient (the furnace body installation gradient is 1 DEG), and sequentially undergoes preheating and drying at 600 ℃, deep carbonization at 700 ℃ and living at 950 DEG After cooling to 400 deg.c, the cooled material is discharged from the furnace via spiral pipe discharger, to obtain 1052kg of qualified activated carbon product. The mass ratio of the water vapor to the columnar clinker is 10:1, the activation time was 50 minutes.
S5: in order to make the activated carbon obtained by activation have higher quality, the activated carbon obtained by S4 is subjected to deashing treatment by using an acid washing process, wherein the main equipment of the acid washing process comprises an enamel reaction kettle or a rubber lining reaction kettle and other acid-resistant equipment. The activated product is soaked in dilute hydrochloric acid solution, heated, stirred, rinsed to be neutral by hot clear water and then dried. In this process, steam at a certain pressure is used as a heat source and power for stirring. The wet activated carbon is generally dried by a rotary furnace to obtain the specific surface area 1089m 2 Activated carbon product/g.
The above embodiments are not limited to the technical solution of the embodiments, and the embodiments may be combined with each other to form a new embodiment. The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and any modifications or equivalent substitutions without departing from the spirit and scope of the present invention should be covered in the scope of the technical solution of the present invention.
Claims (10)
1. A method for preparing synthetic natural gas and active carbon from cotton straw by microwave pyrolysis is characterized in that: the method comprises the following steps:
Step one: mud kneading stage of wave-absorbing material
The wave-absorbing material is measured and then is ground into powder, after the particle size is smaller than 180 meshes, water and additives are added, and the powder is uniformly stirred and mixed to prepare slurry;
step two: spraying stage of cotton stalk surface
After beating and pressing cotton straw and blowing sand by air, cutting the cotton straw into blocks of 10-15 mm, and uniformly spraying the slurry obtained in the step one on the surface of the cotton straw to form a reaction material;
step three: stage of microwave pyrolysis reaction
The reaction materials are sent into a microwave cracking reaction device, and after nitrogen is introduced, microwave cracking reaction is carried out; in the reaction process, a microwave generator in a microwave pyrolysis reaction device generates microwaves with the frequency of 2450MHz to directly heat reaction materials to 290-750 ℃ and the operating pressure is kept at 5-8 KPa;
step four: solid, liquid and gas separation stage
Depositing biomass carbon formed after the microwave pyrolysis reaction at the bottom of a microwave pyrolysis reaction device and cooling to below 200 ℃; removing tar from the gas formed after the microwave pyrolysis reaction, cooling the gas to below 100 ℃, condensing the condensable gas in the gas into a liquid phase, and obtaining the rest gas as mixed gas;
step five: natural gas synthesis stage
Carrying out compression cooling, CO conversion, dry desulfurization, PSA decarburization, methanation, depressurization and dehydration on the mixed gas in the step four to finally form natural gas with the methane content of more than 98%;
step six: stage of activated carbon preparation
And (3) carrying out cooling pulverization, kneading molding, carbonization activation, deashing and drying on the biomass carbon obtained in the step (IV) to finally form the activated carbon.
2. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the additive adopted in the first step is one or more of sodium naphthalene sulfonate formaldehyde condensate, lignin sulfonate, polyethylene glycol, starch, polyacrylamide and polystyrene sulfonate.
3. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the solid content of the slurry obtained in the step one is kept between 10.5% and 58.5%.
4. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the solid weight ratio of cotton straw to slurry in the reaction material obtained in the second step is 100:1.5 to 80.
5. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: and D, obtaining a liquid phase which is wood vinegar.
6. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the mixed gas obtained in the fourth step comprises the following components: h 2 25.0 to 35.0 percent, 18.5 to 24.0 percent of CO and CH 4 15.0 to 35.0 percent, CO 2 26.2 to 36.8 percent, and other gases 1.5 to 3.5 percent, wherein the percentage is volume percentage.
7. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the synthesis process of the natural gas in the fifth step is as follows:
s1: compressing the mixed gas obtained in the step four to 2.1-3.0 MPa, and reducing the temperature to 28-45 ℃;
s2: CO conversion is carried out on the gas obtained in the S1 under the condition of conversion pressure of 2.1-2.5 MPa and conversion temperature of 200-470 ℃ so that CO and H in the gas 2 O reacts to form H 2 And CO 2 ；
S3: carrying out dry desulfurization on the gas obtained in S2 under the conditions of desulfurization pressure of 2.1-2.9 MPa and desulfurization temperature of 200-400 ℃ to ensure that H in the desulfurized gas 2 S content is less than or equal to 0.1PPm;
s4: performing PSA decarbonization on the gas obtained in the step S3 under the condition that the adsorption pressure is 1.5-2.8 MPa and the adsorption temperature is less than or equal to 40 ℃ so that CO in the gas subjected to PSA decarbonization 2 Removing;
s5: methanation is carried out on the gas obtained in the step S4 under the condition of the pressurizing pressure of 3.1-4.5 MPa and the temperature of 200-500 ℃ so as to lead CH in the methanated gas 4 The content reaches more than 98 percent;
s6: and (3) reducing the pressure of the gas obtained in the step S5 to 1.5-1.9 MPa, reducing the temperature to below 40 ℃, and dehydrating by using a solid adsorption method, so that the dew point of the dehydrated gas is less than-40 ℃, thereby obtaining the qualified natural gas.
8. The method for preparing synthetic natural gas and activated carbon from cotton straw by microwave pyrolysis according to claim 1, which is characterized in that: the preparation process of the activated carbon in the step six is as follows:
s1: naturally cooling the biomass charcoal obtained in the step four to normal temperature and pulverizing, so that the granularity of the pulverized biomass charcoal powder is smaller than 200 meshes;
s2: the biomass charcoal powder obtained in the step S1 is fully and uniformly mixed with coal tar under the conditions of the kneading temperature of 70-90 ℃ and the kneading time of 15-20 min, and then dried to form a column raw material;
S3: carbonizing the columnar raw material obtained in the step S2 at 550-650 ℃ under the condition of no or little oxygen to form columnar clinker;
s4: sequentially preheating and drying the columnar clinker obtained in the step S3 at 500-600 ℃, deep carbonizing at 700 ℃ and activating at 800-950 ℃, and cooling to 400 ℃ in a cooling section to form the specific surface area of 850m 2 /g～1100m 2 Activated carbon per gram;
s5: and (3) deashing the activated carbon obtained in the step (S4) by using an acid washing process, and drying to obtain qualified activated carbon.
9. The method for preparing synthetic natural gas and activated carbon from cotton stalk by microwave pyrolysis according to claim 8, wherein the method comprises the following steps: the mass ratio of the water vapor to the columnar clinker in the activation process of the S4 is 8-10: 1.
10. the method for preparing synthetic natural gas and activated carbon from cotton stalk by microwave pyrolysis according to claim 8, wherein the method comprises the following steps: the activation time of the S4 is 30-50 minutes.
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