CN117285951A - Method for removing biomass alkali metal and preparing hydrothermal coke - Google Patents
Method for removing biomass alkali metal and preparing hydrothermal coke Download PDFInfo
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- CN117285951A CN117285951A CN202311239708.8A CN202311239708A CN117285951A CN 117285951 A CN117285951 A CN 117285951A CN 202311239708 A CN202311239708 A CN 202311239708A CN 117285951 A CN117285951 A CN 117285951A
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- 239000002028 Biomass Substances 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 58
- 229910052783 alkali metal Inorganic materials 0.000 title claims abstract description 57
- 150000001340 alkali metals Chemical class 0.000 title claims abstract description 56
- 239000000571 coke Substances 0.000 title claims abstract description 49
- 239000007788 liquid Substances 0.000 claims abstract description 69
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 50
- 239000000203 mixture Substances 0.000 claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 238000000926 separation method Methods 0.000 claims abstract description 11
- 230000035484 reaction time Effects 0.000 claims description 8
- 238000004064 recycling Methods 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 235000013399 edible fruits Nutrition 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 2
- 238000002203 pretreatment Methods 0.000 claims description 2
- 235000013311 vegetables Nutrition 0.000 claims description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 19
- 229910052799 carbon Inorganic materials 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 14
- 238000011084 recovery Methods 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000005265 energy consumption Methods 0.000 description 10
- 150000007524 organic acids Chemical class 0.000 description 6
- 238000003825 pressing Methods 0.000 description 6
- 240000008790 Musa x paradisiaca Species 0.000 description 4
- 235000018290 Musa x paradisiaca Nutrition 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 239000007790 solid phase Substances 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- 241000196324 Embryophyta Species 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 230000006837 decompression Effects 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000010902 straw Substances 0.000 description 2
- 241000609240 Ambelania acida Species 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- 241000195493 Cryptophyta Species 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 244000046052 Phaseolus vulgaris Species 0.000 description 1
- 235000010627 Phaseolus vulgaris Nutrition 0.000 description 1
- 240000006394 Sorghum bicolor Species 0.000 description 1
- 235000011684 Sorghum saccharatum Nutrition 0.000 description 1
- 235000021307 Triticum Nutrition 0.000 description 1
- 244000098338 Triticum aestivum Species 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
- 230000006978 adaptation Effects 0.000 description 1
- 239000010905 bagasse Substances 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 235000013339 cereals Nutrition 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- -1 crops (stalk Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 238000006068 polycondensation reaction Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- 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
- C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
- C10B57/06—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition containing additives
-
- 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
- C10B57/08—Non-mechanical pretreatment of the charge, e.g. desulfurization
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The application belongs to the field of biomass energy, and particularly relates to a method for removing biomass alkali metal and preparing hydrothermal coke. The method of the application comprises the following steps: mixing the pretreated biomass with water to obtain a first mixture, and introducing CO into the first mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; carrying out solid-liquid separation on the solid-liquid mixed product to obtain primary hydrothermal solution and hydrothermal coke; then mixing the pretreated biomass, the primary hydrothermal solution and water to obtain a second mixture, and introducing CO into the second mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; and (3) carrying out solid-liquid separation on the solid-liquid mixed product to obtain secondary hydrothermal solution and hydrothermal coke. The present application utilizes high pressure CO 2 The alkali metal in the biomass can be removed by combining with hydrothermal reaction, and the biomass can be treatedThe high-quality low-ash hydrothermal coke is prepared.
Description
Technical Field
The application belongs to the field of biomass energy, and particularly relates to a method for removing biomass alkali metal and preparing hydrothermal coke.
Background
In the biomass thermal conversion utilization process, alkali metal can cause problems of slag bonding, contamination, corrosion and the like, and the safe and stable operation of equipment is seriously affected. At present, the method for removing alkali metal from biomass mainly adopts a water washing method, an inorganic acid washing method, a hydrothermal method and the like. Although the water washing method has lower cost, only partial alkali metal elements which are soluble in water inside can be removed, and the efficiency is lower. The inorganic acid washing method comprises the steps of solution of hydrochloric acid, sulfuric acid, nitric acid and the like, has high removal efficiency, but has the disadvantage of not neglecting: on one hand, the cost of the eluting solvent is high, and on the other hand, a large amount of water is required to be washed and removed in the later stage of the strong acid elution, so that a large amount of acid wastewater is brought, and the extremely high wastewater treatment cost and serious environmental pollution are caused. In the hydrothermal process of biomass, part of alkali metal can be dissolved in water, so that the slagging and contamination behaviors of the solid hydrothermal coke used as fuel are improved to a certain extent, but the problems of high energy consumption, treatment of polluted water and the like exist. How to reduce energy consumption, improve alkali metal removal efficiency and reduce pollution is a problem to be solved in the field.
Aiming at the problems of high cost, pollution, large energy consumption and the like of the traditional method for removing the alkali metal, the invention provides a method for removing the alkali metal by adopting high-pressure CO 2 And removing biomass alkali metal by hydrothermal reaction. The method reduces the pollution, simultaneously reduces the energy consumption and improves the alkali metal removal efficiency.
Disclosure of Invention
In view of this, the present application provides a method for removing alkali metal from biomass using high pressure CO 2 The alkali metal in the biomass is removed by combining the hydrothermal reaction, and the biomass can be prepared into high-quality low-ash hydrothermal coke.
The application provides a method for removing biomass alkali metal, which comprises the following steps:
step 1, mixing pretreated biomass and water to obtain a first mixture, and introducing CO into the first mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; carrying out solid-liquid separation on the solid-liquid mixed product to obtain primary hydrothermal solution and hydrothermal coke;
step 2, mixing the pretreated biomass, the primary hydrothermal solution and water to obtain a second mixture, and introducing CO into the second mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; and carrying out solid-liquid separation on the solid-liquid mixed product to obtain secondary hydrothermal solution and hydrothermal coke.
Preferably, the method further comprises:
and step 3, recycling the secondary hydrothermal solution, and repeating the step 2, wherein the hydrothermal coke and the recyclable hydrothermal solution are obtained once in each cycle.
Preferably, in step 3, the number of repetitions is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
More preferably, in step 3, the number of repetitions is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
In the method, the step 1 is used for generating primary hydrothermal solution, and the step 2 participates in high-pressure CO for the primary hydrothermal solution 2 And a cyclic reaction with a hydrothermal reaction. The application finds that for high pressure CO 2 The hydrothermal solution reacted with the hydrothermal reaction is recycled, and high-pressure CO 2 The organic acid generated in the hydrothermal reaction process is continuously enriched in the hydrothermal solution, so that the effect of removing alkali metal is achieved, the original structure of biomass can be continuously improved in the hydrothermal solution circulation process of the repeated step 2, and the reactions such as polymerization and polycondensation are carried out to form a new carbon body, so that the fixed carbon content is improved, the heat value is improved, and the quality of the hydrothermal coke is improved. The recycling of the hydrothermal solutions can recycle part of heat of the hydrothermal solutions, and pollution caused by subsequent hydrothermal solution treatment is reduced.
However, the present application found that when the hydrothermal solution reaches a certain number of cycles, the concentration of alkali metal contained is high, which is disadvantageous in that alkali metal in biomass is re-introduced into the hydrothermal solution. Therefore, the hydrothermal solution cannot be recycled infinitely, otherwise the purpose of removing alkali metal cannot be achieved, and the number of times of repeating the step 2 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
Preferably, in the step 1, the solid-to-liquid ratio of the biomass to the water is 1:5-1:50;
in the step 2, the solid-liquid ratio of the biomass to the sum of the primary hydrothermal solution and the water is 1:5-1:50, namely, the solid-liquid ratio of the biomass to (the sum of the primary hydrothermal solution and the water) is 1:5-1:50.
More preferably, in step 1, the solid-to-liquid ratio of the biomass to the water is 1:15; in step 2, the solid-to-liquid ratio of the biomass to (the sum of the primary hydrothermal solution and the water) is 1:15.
Preferably, in step 1 and step 2, the CO 2 The pressure of (2) is 1-15 MPa. More preferably, in step 1 and step 2, the CO 2 The pressure of (2) is 4-6MPa.
Preferably, in the step 1 and the step 2, the heating temperature of the hydrothermal reaction is 120-300 ℃, and the reaction time of the hydrothermal reaction is 4-120 min; more preferably, the heating temperature of the hydrothermal reaction is 230-250 ℃, and the reaction time of the hydrothermal reaction is 4-6 min.
Preferably, the CO 2 The pressure of (2) is 4-6MPa; the heating temperature of the hydrothermal reaction is 230-250 ℃, and the reaction time of the hydrothermal reaction is 4-6 min.
Specifically, in the step 1, the primary hydrothermal solution accounts for 75% -95% of the volume of the first mixture; in the step 2, the amount of the primary hydrothermal solution is insufficient to react with the pretreated biomass, so that additional water needs to be added, and the additional water is supplemented according to the solid-to-liquid ratio of 1:1-1:2.
Preferably, step 1 further comprises premixing the first mixture, wherein the premixing comprises introducing CO at 0.1-0.5 MPa 2 Stirring for 5-30 min;
step 2 also comprises premixing the second mixture, wherein the premixing comprises introducing CO of 0.1-0.5 MPa 2 And stirred for 5-30 min.
More preferably, in step 1 and step 2, the CO in the premixing is 2 The pressure is 0.1MPa, and the stirring time is 5min.
Specifically, in the products of the step 1 and the step 2, the primary hydrothermal solution and the secondary hydrothermal solution can keep 70-80% of the temperature during the hydrothermal reaction, and the heating time and the energy required by heating during the hydrothermal reaction can be saved by recycling the primary hydrothermal solution and the secondary hydrothermal solution, so that the energy of the hydrothermal solution can be recycled by the method for recycling the hydrothermal solution.
Specifically, the solid-phase product hydrothermal coke obtained by repeating the steps 1 and 2 can be used as high-quality fuel.
Preferably, in step 1 and step 2, the pretreatment method of biomass includes: and (3) crushing and grinding the biomass raw material to obtain the pretreated biomass, wherein the particle size of the biomass raw material is 2-10 mm.
Preferably, the biomass comprises one or more of the rhizomes of cereal plants, the rhizomes of vegetable plants and the rhizomes of fruits.
Specifically, the biomass may be wood, crops (stalk, straw, wheat straw, bean stalk, cotton stalk, chaff, corn stalk, corncob, sorghum crumb, nut shell, etc.), weeds, algae, fruits (fruit peel, banana stalk, bagasse), etc
Specifically, in step 1 and step 2, the solid-liquid separation method may be an existing conventional solid-liquid separation method, including but not limited to sedimentation, filtration, membrane filtration, mechanical press filtration, vacuum or centrifugation, and the like.
More specifically, in the step 1 and the step 2, the solid-liquid separation method is a sedimentation and mechanical filter pressing method, the solid-liquid mixed product is settled to obtain an upper layer liquid, the volume of the upper layer liquid accounts for 55-65% of that of the solid-liquid mixed product, and the retention temperature of the upper layer liquid is 78-85% of that of the hydrothermal reaction; and carrying out mechanical filter pressing separation on the settled lower-layer bottom slurry to obtain lower-layer liquid, wherein the upper-layer liquid and the lower-layer liquid are both hydrothermal liquid, the volume of the lower-layer liquid accounts for 20-30% of the solid-liquid mixed product, and the retention temperature of the lower-layer liquid is 70-75% of the temperature of the hydrothermal reaction kettle.
The application provides a method for removing biomass alkali metal and preparing hydrothermal coke by using high-pressure CO 2 And removing alkali metal in the biomass by combining with hydrothermal reaction, and preparing the biomass into high-quality low-ash hydrothermal coke. The method of the invention also has the following advantages:
(1) Introducing CO into a mixture of biomass and water 2 Can promote Na, K, ca, mg, sn, fe and other elements to migrate into hydrothermal solution and realize CO 2 And (3) sealing and storing the biomass, and increasing the hydrothermal reaction rate of the biomass.
(2) Organic acid can be generated in the hydrothermal reaction process, the organic acid can be accumulated in the hydrothermal liquid in a hydrothermal liquid circulation mode, the biomass is fully soaked in the hydrothermal liquid, removal of alkali metal in the biomass is facilitated, pollution caused by the production process is reduced, the hydrothermal reaction temperature is reduced, and energy consumption is reduced.
(3) In the hydrothermal solution circulation process, the original structure of the biomass can be improved by small molecular products formed by decomposing the biomass, so that the content of the hydrothermal coke fixed carbon after the hydrothermal solution circulation is increased, and the hydrothermal Jiao Rezhi is improved.
Drawings
In order to more clearly illustrate the embodiments of the present application 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.
FIG. 1 is a schematic diagram of a hydrothermal circulation process according to the present invention;
FIG. 2 is a flow chart of a method for removing alkali metal from biomass provided by the invention;
FIG. 3 shows the removal rate of alkali metal K by the methods of the examples and comparative examples provided by the present invention;
FIG. 4 shows the Na removal rate of alkali metal according to the methods of examples and comparative examples provided by the present invention;
FIG. 5 is a graph showing the percentage of fixed carbon content statistics in the hydrothermal char for the example and comparative example methods provided by the present invention;
FIG. 6 is a chart showing the mid-to-higher heating value statistics of the hydrothermal focus of the example and comparative example methods provided by the present invention;
FIG. 7 is a graph showing hydrothermal fluid energy recovery statistics for the example and comparative example methods provided by the present invention.
Detailed Description
The application provides a method for removing biomass alkali metal and preparing hydrothermal coke, which adopts high-pressure CO 2 The water phase circulating hydrothermal deashing method reduces pollution, reduces energy consumption and improves alkali metal removal efficiency, and is used for solving the technical defects of high cost, pollution and high energy consumption of the traditional biomass alkali metal removal method.
The following description of the technical solutions in the embodiments of the present application will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
The raw materials used in the following examples are all commercially available or self-made.
In particular, the mechanism of the hydrothermal circulation process of the application is shown in figure 1, and the high-pressure CO 2 So that H is in the liquid phase + Concentration is increased while CO 2 Inhibition of H by reverse steam variation 2 The production of the reaction system is ensured. Under the hydrothermal reaction of specific conditions, organic acid is generated by biomass, and the organic acid in the hydrothermal solution is accumulated along with the recycling and re-reaction of the hydrothermal solution, so that the removal of alkali metal in the biomass is facilitated, the pollution caused by the subsequent hydrothermal solution treatment is reduced, and the energy consumption is reduced by recycling part of heat.
Specifically, the flow of the method in the embodiment of the application is shown in fig. 2. Firstly, the pretreated biomass A is crushed to obtain biomass with the particle size of 2-10 mm, the biomass and water C are introduced into a mixer 2 for mixing (the solid-liquid ratio is 1:5-1:50), and CO with the pressure of 0.1-0.5 MPa is introduced 2 Mixing for 5-30 min to obtain a first mixture, and mixing the first mixtureDelivering the mixture into a hydrothermal reaction kettle 3, and introducing CO of 1-15 MPa 2 Carrying out hydrothermal reaction (heating temperature is 120-300 ℃ and reaction time is 4-120 min); after the reaction is finished, the product is decompressed through a decompression kettle to obtain an upper layer liquid; then, carrying out mechanical filter pressing 4 treatment on the bottom slurry, and carrying out filter pressing to obtain a lower layer liquid and hydrothermal coke E, and combining the upper layer liquid and the lower layer liquid to obtain a primary hydrothermal liquid; then, the primary hydrothermal solution is recycled and conveyed into a mixer 2 to be mixed with the new substances and a proper amount of water (the solid-liquid ratio is 1:5-1:50), and CO with the pressure of 0.1-0.5 MPa is introduced 2 Mixing for 5-30 min to obtain a second mixture, conveying the second mixture into a hydrothermal reaction kettle 3, and introducing CO of 1-15 MPa 2 Carrying out hydrothermal reaction (heating temperature is 120-300 ℃ and reaction time is 4-120 min); after the reaction is finished, the product is decompressed through a decompression kettle to obtain an upper layer liquid; then, carrying out mechanical filter pressing 4 treatment on the bottom slurry, and carrying out filter pressing to obtain a lower layer liquid and hydrothermal coke E, and combining the upper layer liquid and the lower layer liquid to obtain a secondary hydrothermal liquid; repeating the steps to obtain hydrothermal solution and hydrothermal coke for 1-13 times of reaction.
In the method, the volume ratio of the upper layer liquid to the first mixture/the second mixture is 55-65%, and the retention temperature of the upper layer liquid is 78-85% of the temperature of the hydrothermal reaction kettle. The volume ratio of the lower layer liquid to the first mixture/the second mixture is 20-30%, and the retention temperature of the lower layer liquid is 70-75% of the temperature of the hydrothermal reaction kettle. In the method, the solid-phase product hydrothermal coke obtained by each reaction can be used as high-quality fuel.
Example 1
The embodiment provides a method for removing biomass alkali metal, which comprises the following steps:
(1) Crushing banana cauloid to 2mm, and putting the crushed materials into a mixer according to a solid-to-liquid ratio of 1:15 with water and introducing 0.1MPa CO 2 And stirred for 5min. After stirring, the mixture enters a hydrothermal reaction kettle, and CO is introduced 2 Pressurizing to 5MPa, heating to 240 ℃, reacting for 5min, and then introducing into a pressure release kettle for pressure release. Extruding the bottom slurry by a machine to obtain solid hydrothermal coke and lower liquid, combining the upper liquid and the lower liquid into primary hydrothermal liquid, and feeding the primary hydrothermal liquid into a mixer for carrying outAnd (5) producing next time.
(2) Crushing banana cauloid to 2mm, and putting the crushed materials into a mixer according to a solid-to-liquid ratio of 1:15 mixing the primary hydrothermal solution and water, and introducing 0.1MPa CO 2 And stirred for 5min. After stirring, the mixture enters a hydrothermal reaction kettle, and CO is introduced 2 Pressurizing to 5MPa, heating to 240 ℃, reacting for 5min, and then introducing into a pressure release kettle for pressure release. Namely, the continuous production of the hydrothermal coke is carried out according to the steps, and the rest conditions are kept consistent. According to the method, the secondary hydrothermal solution and the hydrothermal coke are obtained, the removal rate of Shui Rejiao alkali metal K is 85.04%, the removal rate of Na is 75.36%, the fixed carbon content is 31.24%, the high-order heat value reaches 22.24MJ/kg, and the energy recovery rate of the hydrothermal solution is 70.25%.
Example 2
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated once to obtain three hydrothermal solutions and hydrothermal cokes. The obtained hydrothermal coke has the removal rate of 85.96 percent, the Na removal rate of 76.25 percent, the fixed carbon content of 32.52 percent, the high-order heat value of 22.49MJ/kg and the energy recovery rate of the hydrothermal solution of 70.02 percent.
Example 3
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated twice to obtain four hydrothermal solutions and hydrothermal cokes. The obtained hydrothermal coke has the removal rate of 87.08 percent of alkali metal K, the removal rate of 78.29 percent of Na, the fixed carbon content of 33.25 percent, the high-order heat value of 23.08MJ/kg and the energy recovery rate of the hydrothermal solution of 69.91 percent.
Example 4
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated three times to obtain five hydrothermal solutions and hydrothermal cokes. The obtained hydrothermal coke has a removal rate of 88.90 percent of alkali metal K, a removal rate of 79.12 percent of Na, a fixed carbon content of 33.64 percent, a high-order heat value of 24.08MJ/kg and an energy recovery rate of 69.83 percent.
Example 5
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated nine times to obtain ten hydrothermal solutions and hydrothermal cokes. The obtained hydrothermal coke has a removal rate of 90.21 percent, a Na removal rate of 82.24 percent, a fixed carbon content of 33.91 percent, a high-order heat value of 24.21MJ/kg and a hydrothermal solution energy recovery rate of 69.94 percent.
Example 6
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated ten times to obtain twelve hydrothermal solutions and hydrothermal cokes. The obtained hydrothermal coke has a removal rate of 84.90% of alkali metal K, a removal rate of 74.12% of Na, a fixed carbon content of 33.94%, a high-order heat value of 24.22MJ/kg and an energy recovery rate of 69.91%.
Example 7
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated ten times to obtain thirteen times of hydrothermal solution and hydrothermal coke. The obtained hydrothermal coke has an alkali metal K removal rate of 84.78%, a Na removal rate of 74.01%, a fixed carbon content of 33.95%, a high-order heat value of 24.23MJ/kg and a hydrothermal solution energy recovery rate of 69.95%.
Example 8
This example provides a method for removing alkali metal from biomass, which differs from example 1 in that step 2 is repeated twelve times to obtain ten times of hydrothermal solution and hydrothermal coke. The obtained hydrothermal coke has an alkali metal K removal rate of 84.71%, a Na removal rate of 73.92%, a fixed carbon content of 33.98%, a high-order heat value of 24.25MJ/kg and an energy recovery rate of 69.93%.
Comparative example 1
The comparative example differs from example 1 in that step 2 was omitted, i.e. the banana cauloid was crushed to 2mm, and the crushed material was placed in a mixer according to a solid to liquid ratio of 1:15 with water and introducing 0.1MPa CO 2 And stirred for 5min. After stirring, the mixture enters a hydrothermal reaction kettle, and CO is introduced 2 Pressurizing to 5MPa, heating to 240 ℃, allowing the mixture to enter a pressure release kettle for pressure release after reacting for 5 minutes, and performing extrusion filtration on primary hydrothermal solution to obtain the hydrothermal coke, wherein the removal rate of alkali metal K is 82.88%, the removal rate of Na is 72.39%, the fixed carbon content is 25.46%, and the high-order heat value reaches 21.81MJ/kg, the energy recovery rate of the hydrothermal solution is 0%.
Comparative example 2
This comparative example differs from example 1 in that step 2 was omitted and the hydrothermal reaction temperature in step 1 was 200 ℃. The obtained hydrothermal coke has a removal rate of 78.91% of alkali metal K, a Na removal rate of 69.22%, a fixed carbon content of 24.20%, a high-order heat value of 17.72MJ/kg and an energy recovery rate of 0%.
Comparative example 3
This comparative example differs from example 1 in that step 2 was omitted and the hydrothermal reaction time in step 1 was 30min. The obtained hydrothermal coke has an alkali metal K removal rate of 83.92%, a Na removal rate of 73.42%, a fixed carbon content of 25.34%, a high-order heat value of 21.68MJ/kg and an energy recovery rate of 0%.
Comparative example 4
The comparative example differs from example 1 in that step 2 was omitted and CO was introduced in step 1 2 Pressurizing to 1MPa, heating to 240 ℃, and reacting for 5min. The obtained hydrothermal coke has a removal rate of 81.42% of alkali metal K, a removal rate of 71.24% of Na, a fixed carbon content of 22.34%, a high-order heat value of 20.18MJ/kg and an energy recovery rate of 0%.
The application adopts high-pressure CO 2 The hydrothermal reaction combined with the hydrothermal solution circulation can enable the organic acid to accumulate in the hydrothermal solution, the biomass is fully soaked in the hydrothermal solution, the removal of alkali metal in the biomass is facilitated, the pollution caused by the production process is reduced, meanwhile, the hydrothermal reaction temperature is reduced, and the energy consumption is reduced. Meanwhile, as can be seen from the data of the above examples and comparative examples, the present patent finds that the number of repetitions of step 2 (i.e. the number of repetitions of the secondary hydrothermal solution) has a large influence on the removal rate of alkali metal, and also has a large influence on the fixed carbon content and the higher calorific value of the hydrothermal coke, and the number of hydrothermal solution circulation is too high, so that the concentration of alkali metal in the hydrothermal solution is high, and the alkali metal in the biomass is not beneficial to the formation of fixed carbon when the alkali metal in the biomass is re-fed into the hydrothermal solution, so that the number of hydrothermal solution circulation needs to be controlled within a proper range; in addition, the hydrothermal solution is recycled, the heat of the hydrothermal solution can be recycled, and the energy consumption and the heating time of the hydrothermal reaction are reduced.
To sum upThe biomass raw material is pretreated, then mixed with water in a mixer and introduced with CO 2 Fully mixing the materials for a period of time, then entering a hydrothermal reaction kettle, and introducing high-pressure CO 2 Heating to perform hydrothermal reaction, allowing the reaction to enter a pressure release kettle for a period of time, and separating liquid and solid phases through a separation system after pressure release is completed to obtain hydrothermal coke and hydrothermal liquid. The hydrothermal solution enters the mixer again through the circulating system to be mixed with biomass and supplemented with water, and the hydrothermal solution is subjected to high-pressure CO again 2 And hydrothermal reaction, and then liquid-solid phase separation. After the hydrothermal solution is recycled, the removal rate of the alkali metal K is more than 85%, the removal rate of the alkali metal Na is more than 75%, the energy recovery rate of the hydrothermal solution is more than 60%, the fixed carbon content is more than 30%, and the heat value is more than 22 MJ/kg.
The foregoing is merely a preferred embodiment of the present application and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present application and are intended to be comprehended within the scope of the present application.
Claims (10)
1. A method for removing alkali metal from biomass and preparing hydrothermal coke, comprising the steps of:
step 1, mixing pretreated biomass and water to obtain a first mixture, and introducing CO into the first mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; carrying out solid-liquid separation on the solid-liquid mixed product to obtain primary hydrothermal solution and hydrothermal coke, wherein the primary hydrothermal solution is recycled;
step 2, mixing the pretreated biomass, the primary hydrothermal solution and water to obtain a second mixture, and introducing CO into the second mixture 2 Heating to perform hydrothermal reaction to obtain a solid-liquid mixed product; and carrying out solid-liquid separation on the solid-liquid mixed product to obtain secondary hydrothermal solution and hydrothermal coke.
2. The method as recited in claim 1, further comprising:
and step 3, recycling the secondary hydrothermal solution, and repeating the step 2, wherein the hydrothermal coke and the recyclable hydrothermal solution are obtained once in each cycle.
3. The method of claim 2, wherein in step 3, the number of repetitions is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12.
4. The method according to claim 2, wherein in step 1, the solid to liquid ratio of the biomass to the water is 1:5 to 1:50;
in the step 2, the solid-liquid ratio of the biomass to the sum of the primary hydrothermal solution and the water is 1:5-1:50.
5. The method according to claim 1, wherein in step 1 and step 2, the CO 2 The pressure of (2) is 1-15 MPa.
6. The method according to claim 1, wherein in step 1 and step 2, the heating temperature of the hydrothermal reaction is 120 to 300 ℃, and the reaction time of the hydrothermal reaction is 4 to 120min.
7. The method according to any one of claims 1 to 6, wherein the CO 2 The pressure of (2) is 4-6MPa; the heating temperature of the hydrothermal reaction is 230-250 ℃, and the reaction time of the hydrothermal reaction is 4-6 min.
8. The method of claim 1, further comprising pre-mixing the first mixture in step 1, the pre-mixing comprising introducing CO at 0.1-0.5 MPa 2 Stirring for 5-30 min;
step 2 also comprises premixing the second mixture, wherein the premixing comprises introducing CO of 0.1-0.5 MPa 2 And stirred for 5-30 min.
9. The method according to claim 1, wherein in step 1 and step 2, the pretreatment method of biomass comprises: and (3) crushing and grinding the biomass raw material to obtain the pretreated biomass, wherein the particle size of the biomass raw material is 2-10 mm.
10. The method of claim 1, wherein the biomass comprises one or more of a rhizome stem leaf of a grain plant, a rhizome stem leaf of a vegetable plant, and a rhizome stem leaf of a fruit.
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