Method for providing pyrolysis oil from biomass containing holocellulose and lignin
A two-stage pyrolysis process with controlled residence times in separate reactors enhances pyrolysis oil quality by increasing yield and energy content, addressing existing rapid pyrolysis technology limitations.
Patent Information
- Application Number
- CN202280100987.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-31
- Publication Date
- 2025-07-15
AI Technical Summary
In the process of converting biomass into pyrolytic oil, the existing rapid pyrolysis process has problems of low yield and insufficient energy content, especially in optimizing yield and reducing water content.
Using a dual reactor system, rapid pyrolysis treatment is performed first in the first reactor, followed by prolonging the pyrolysis time in the second reactor, separating the solid layer by gravity deposition, controlling the residence time of the second reactor for further cracking of lignin, combining anaerobic conditions and quenching treatment to condense the pyrolysis gas.
The yield and energy content of pyrolytic oil is improved, the water content is reduced, the carbon-oxygen ratio is increased, and the quality and yield of pyrolytic oil is improved.
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Figure CN120322524A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for providing pyrolysis oil from biomass containing holocellulose and lignin. Among other things, the method provides an improved pyrolysis oil / coke ratio or higher yield. Among other things, the method also provides pyrolysis oil having an improved carbon (C) / oxygen (O) ratio or energy content. Background Art
[0002] Rapid pyrolysis, like slow pyrolysis, is the heating of biomass in the absence of oxygen. Different from slow pyrolysis, rapid pyrolysis typically uses a high heating rate, a short residence time, and rapid quenching of steam to maximize the production of an organic liquid oily product, also known as bio-oil or pyrolysis oil.
[0003] The rapid pyrolysis of biomass using a high heating rate and rapid steam cooling can minimize secondary cracking reactions and repolymerization. By operating at a high temperature, a relatively high yield of pyrolysis oil can be obtained. The rapid pyrolysis of biomass is usually combined with the pretreatment of biomass, including drying the biomass to less than 10 wt.% water and grinding the biomass to a particle size of 2 to 3 mm. A variety of rapid pyrolysis technologies are being or have been commercially developed:
[0004] - A rapid pyrolysis process developed by companies such as Dynamotive Energy Systems Corporation using a fluidized bed reactor;
[0005] - The RTP (Rapid Thermal Processing) process developed by Ensyn Technologies using a transport dilute fluidized bed; and
[0006] - A rapid pyrolysis process developed by Savon Voima using a fluidized bed reactor; and
[0007] - A rapid pyrolysis process developed by Biomass Technology Group using an improved rotating cone reactor.
[0008] In the first three technologies, the recycle of non-condensable products causes the fluidization of the bed, where its rate determines the residence time of steam in the reactor. In all cases, a portion of the gas produced is used to provide energy for the pyrolysis. Particularly in the RTP process, a hot transport dilute fluidized bed (usually sand) is circulated between two reactors: the first reactor is used for pyrolysis, while the second reactor reheats the sand particles by burning the coke formed during pyrolysis.
[0009] In contrast, the process commercialized by BTG is based on the intense mixing of biomass particles with hot sand in an improved rotating cone reactor. Since no carrier gas is used, the volume of the vapor leaving the reactor is much lower than that in a fluidized bed reactor, and thus the size of the condenser used for recovering bio-oil is smaller than that in other technologies. The solid stream containing coke and sand grains is recycled to the combustion section, where burning off the coke provides the energy required to reheat the sand grains fed back to the pyrolysis reactor.
[0010] Although fast pyrolysis technology is commercially available, there is still a need in the art to improve fast pyrolysis process parameters, such as optimizing yields, reducing water content, and / or increasing the energy content of the resulting pyrolysis oil. Summary of the Invention
[0011] Among other purposes, an object of the present invention is to meet the above-mentioned needs in the art.
[0012] As described in the appended claims, the present invention meets the above-mentioned needs.
[0013] Specifically, the present invention meets the above-mentioned needs by a method for providing pyrolysis oil from biomass containing holocellulose and lignin, the method comprising the following steps:
[0014] a) introducing the biomass and a solid heat carrier at a temperature of 400 °C to 700 °C into a first reactor or a first reaction zone respectively;
[0015] b) continuously mixing the biomass and the solid heat carrier in the first reactor or the first reaction zone in the absence of oxygen to provide a first period of pyrolysis treatment of 0.5 to 5 seconds, generating a mixture containing partially pyrolyzed biomass and the solid heat carrier and primary pyrolysis gas;
[0016] bl) optionally, collecting the primary pyrolysis gas from the first reactor or the first reaction zone;
[0017] c) introducing the mixture from the first reactor or the first reaction zone into a second reactor or a second reaction zone, the second reactor or the second reaction zone being configured to provide sedimentation or separation of solids at the bottom of the second reactor or the second reaction zone by gravity, thereby forming a solid layer at the bottom of the second reactor or the second reaction zone;
[0018] d) maintaining the mixture in the second reactor or the second reaction zone for a second period of pyrolysis treatment of 10 to 1200 seconds under anaerobic conditions, additionally generating secondary pyrolysis gas and solid coke, while collecting pyrolysis gas from the second reactor or the second reaction zone;
[0019] e) The collected primary and secondary pyrolysis gases are preferably condensed into pyrolysis oil by quenching to a temperature of 60 °C or lower.
[0020] The inventors have surprisingly found that, compared with the prior art, by increasing the pyrolysis treatment time in the second reactor, the pyrolysis oil yield increases, the resulting pyrolysis oil has a lower water content and / or the energy content of the resulting pyrolysis oil increases, as indicated by a higher carbon (C) / oxygen (O) ratio.
[0021] Without wishing to be bound by a potential mechanism, the inventors hypothesize that the holocellulose (hemicellulose and cellulose) present in the biomass is mainly pyrolyzed (cracked) in the first reactor or the first reaction zone, while the increased time period in the second reactor or the second reaction zone allows additional pyrolysis (cracking) of lignin and the like.
[0022] In the method according to the invention, no other heat is introduced into the method except for the heat provided by the heat carrier introduced into the first reactor or the first reaction zone.
[0023] According to the invention, the method can be carried out in a separate reactor vessel or in a single apparatus comprising separate reaction zones, thereby allowing the required mixing and separation.
[0024] According to the invention, a solid layer, typically consisting of sand and coke, located at the bottom of the second reactor or the second reaction zone is considered necessary to prevent oxygen from entering the second reactor or the second reaction zone.
[0025] According to a preferred embodiment of the invention, the second time period is determined by the height of a solid layer or a dipleg deposited or separated at the bottom of the second reactor or the second reaction zone. The solid is mainly a mixture of a heat carrier and (partially) pyrolyzed biomass or coke.
[0026] According to a particularly preferred embodiment of the invention, the height of the solid layer deposited or separated at the bottom of the second reactor or the second reaction zone controls the second time period, where an increased height increases the second time period. In the second reactor or the second reaction zone, the height of the solid layer at the bottom can be easily controlled using a level controller, thereby allowing removal of solids from the bottom of the second reactor or the second reaction zone.
[0027] According to a preferred embodiment of the invention, the second time period in the method is from 10 to 900 seconds, preferably from 50 to 900 seconds, more preferably from 100 to 900 seconds, and most preferably from 200 to 720 seconds.
[0028] According to the present invention, the solid heat carrier of the present invention is selected from the group consisting of siliceous minerals, catalytic minerals, metals, zeolites, and sand. Sand is preferred because it is an easily obtainable inert material.
[0029] The method provides pyrolysis oil having an increased C content, pyrolysis oil having an increased oil / coke ratio or yield, and / or pyrolysis oil having an increased C / O ratio or energy content.
[0030] Suitable biomass containing holocellulose and lignin used in the method is selected from the group consisting of wood, wood-derived products, agricultural products, agricultural wastes, horticultural products, horticultural wastes, forestry products, forestry wastes, wastes from the human or animal food processing industry, wood chips, sawdust, wood pellets, bark, seeds, nuts, husks, and combinations thereof.
[0031] According to the present invention, the first time period is determined by the volume of the first reactor or the first reaction zone, and the feed rates of the biomass and the solid heat carrier, i.e., the first reactor or the first reaction zone is configured and operated to provide a residence time of 0.5 to 5 seconds.
[0032] The method is preferably a continuous process, i.e., the biomass and the solid heat carrier are continuously supplied to the first reactor or the first reaction zone, the pyrolysis gas is continuously collected from one or more of the reactors or one or more of the reaction zones, and the solid heat carrier and coke are continuously removed from the second reactor or the second reaction zone.
[0033] Preferably, the moisture content of the biomass is less than 10 wt.%, preferably less than 5 wt.%, more preferably less than 3 wt.% or less than 4 wt.%.
[0034] According to the present invention, the temperature of the heat carrier in step (a) is preferably 450 °C to 650 °C, more preferably 450 °C to 600 °C.
[0035] According to a preferred embodiment of the present invention, the first reactor or the first reaction zone includes a mixing device and inlets for the biomass and the heat carrier, an outlet for the mixture of the partially pyrolyzed biomass and the solid heat carrier, and optionally an outlet for primary pyrolysis gas.
[0036] According to another preferred embodiment of the present invention, the second reactor or the second reaction zone includes means for separating solid particles and gas by gravity, and the second reactor further includes an inlet for the mixture of the partially pyrolyzed biomass and the solid heat carrier, an outlet for the solids deposited or separated at the bottom of the second reactor, and an outlet for pyrolysis gas. Description of the Drawings
[0037] The present invention will be further described in detail in the following embodiments. In the said embodiments, reference is made to the following drawings, wherein:
[0038] Figure 1 : shows a schematic diagram of the present method; Figure 1 The top of shows an embodiment of collecting pyrolysis gas from the first and second reactors. Figure 1 The bottom of shows an embodiment of collecting gas from the second reactor.
[0039] Figure 2 : shows a schematic diagram of the second reactor, wherein the height of the solid layer (gray area) or the dipleg deposited or separated at the bottom of the second reactor is different;
[0040] Figure 3 : graphically shows the relationship between the yield, carbon content, and energy content of pyrolysis oil and the residence time in the second reactor or the second reaction zone;
[0041] Figure 4 : graphically shows the relationship between the coke production and the residence time in the second reactor or the second reaction zone. Detailed Description of the Invention
[0042] Examples
[0043] Introduction
[0044] According to the present invention, the pyrolysis of biomass can be divided into two stages: 1) the cracking of holocellulose (hemicellulose and cellulose) and 2) the cracking of lignin. These two stages produce different products and preferably require two cracking strategies. The first cracking strategy generally includes rapidly heating to crack holocellulose, and then rapidly cooling the produced pyrolysis gas (primary gas) to prevent subsequent conversion into permanent gas and water. The second cracking strategy generally includes subjecting lignin to high temperature, but contrary to cracking holocellulose, maintaining the lignin at high temperature to obtain its sufficient conversion rate. The produced gas is guided through a hot sand bed for further cracking to obtain short-chain carbon products (secondary pyrolysis gas).
[0045] The present invention relates to a method for optimally combining two pyrolysis stages in a single pyrolysis process. The present method provides the following advantages:
[0046] 1) Higher quality oil (less water, more organic matter, more acid-emulsifier, shorter phenolic chain - lower polarity, less prone to phase separation);
[0047] 2) Less cracked "non-condensable gas" from the primary gas results in a higher oil yield;
[0048] 3) The increased cracking of lignin provides less "char" and thus higher oil yields.
[0049] Figure 1 An embodiment of the method is schematically shown. The method uses two reactors, where biomass and a heat carrier are supplied to a first reactor configured to provide a residence time of 0.5 to 5 seconds. Subsequently, the partially pyrolyzed biomass is fed into a second reactor, which is configured to allow a residence time of 10 to 1200 seconds.
[0050] Specifically, biomass and a heat carrier (sand) are fed into reactor 1, where they are immediately physically mixed. In reactor 1, "fast pyrolysis" occurs, which is characterized by a rapid temperature increase of the biomass and a short residence time of the primary gas. The residence time of the primary gas is as short as possible (on the order of 0.5 - 5 seconds).
[0051] A mixture of biomass, heat carrier (sand), and pyrolysis gas from fast pyrolysis leaves reactor 1 and enters reactor 2 (separator). The primary pyrolysis gas from fast pyrolysis rises directly in the separator, and the heat carrier (sand) and solid biomass (not fully cracked due to the short residence time in the first reactor) descend (by gravity) in the separator.
[0052] The solid forms a layer (downcomer), and in the separator, this layer slowly sinks (residence time is about 10 to 900 seconds). Due to the high temperature in the downcomer (usually > 350 °C), the lignin "cracks", and the remaining material produces gases that move upward through the hot sand bed and ultimately form secondary pyrolysis gas.
[0053] The combination of primary and secondary gases is condensed into a liquid (pyrolysis oil), for example, by a cyclone separator, while the heat carrier (sand) and fully converted biomass (char) leave the separator through the bottom.
[0054] Experimental setup
[0055] Pyrolysis was carried out using a small pilot plant with 3 different levels of downcomer sand height (as Figure 2 schematically shown) to demonstrate the effect of the residence time of lignin in the downcomer on the quality and yield of the resulting pyrolysis oil.
[0056] Specifically, three experiments were conducted using lignocellulose, clean sand, and a startup fluid, where the output of the screw used to remove sand and char under the separator (reactor 2) was varied between experiments in the following manner: different height levels (I, II, and III) of the downcomer were provided for each run while keeping other operating parameters constant. The different height levels used were: I = very low, at the verge of oxygen transfer; II = low level; III = high level. In the experimental setup used, the residence times obtained in the second reactor were: III: 11 minutes (run 1); II: 4.5 minutes (run 2); I: 3.6 minutes (run 3).
[0057] Results
[0058] As Figure 3 and shown in the following table, higher quality pyrolysis oil was obtained at higher separator levels for the following reasons:
[0059] 1) More organic components as indicated by an increase in the C / O ratio;
[0060] 2) Lower water content in the pyrolysis oil;
[0061] As Figure 4 and shown in the following table, a higher oil / coke yield ratio (material balance) was obtained.
[0062]
[0063]
Claims
1. A method for providing pyrolysis oil from biomass containing holocellulose and lignin, the method comprising the following steps: a) separately introducing the biomass and a solid heat carrier at a temperature of 400 °C to 700 °C into a first reactor or a first reaction zone; b) continuously mixing the biomass and the solid heat carrier in the first reactor or the first reaction zone in the absence of oxygen to provide a first period of pyrolysis treatment of 0.5 to 5 seconds, thereby producing a mixture of partially pyrolyzed biomass and the solid heat carrier and primary pyrolysis gas; bl) optionally, collecting the primary pyrolysis gas from the first reactor or the first reaction zone; c) introducing the mixture from the first reactor or the first reaction zone into a second reactor or a second reaction zone, the second reactor or the second reaction zone being configured to provide deposition or separation of solids at the bottom of the second reactor or the second reaction zone by gravity, thereby forming a solid layer at the bottom of the second reactor or the second reaction zone; d) maintaining the mixture in the second reactor or the second reaction zone for a second period of pyrolysis treatment of 10 to 1200 seconds in the absence of oxygen, additionally producing secondary pyrolysis gas and solid coke, while collecting pyrolysis gas from the second reactor or the second reaction zone; e) condensing the collected primary pyrolysis gas and secondary pyrolysis gas into pyrolysis oil, preferably by quenching to a temperature of 60 °C or lower.
2. The method according to claim 1, wherein the second period of pyrolysis treatment is determined by the height of the solid layer deposited or separated at the bottom of the second reactor or the second reaction zone.
3. The method according to claim 2, wherein The height of the solid layer deposited or separated at the bottom of the second reactor or the second reaction zone controls the second period, wherein an increased height increases the second period.
4. The method according to any one of claims 1 to 3, wherein the second period of pyrolysis treatment is 10 to 900 seconds, preferably 50 to 900 seconds, more preferably 100 to 900 seconds, and most preferably 200 to 720 seconds.
5. The method according to any one of claims 1 to 4, wherein the solid heat carrier is selected from the group consisting of siliceous minerals, catalytic minerals, metals, zeolites, and sand.
6. The method according to any one of claims 1 to 5, wherein the method provides pyrolysis oil having an increased C content.
7. The method according to any one of claims 1 to 6, wherein the method provides pyrolysis oil having an increased oil / coke ratio or yield.
8. The method according to any one of claims 1 to 7, wherein the method provides pyrolysis oil having an increased C / O ratio or energy content.
9. The method according to any one of claims 1 to 8, wherein the biomass containing holocellulose and lignin is selected from the group consisting of wood, wood-derived products, agricultural products, agricultural wastes, horticultural products, horticultural wastes, forestry products, forestry wastes, wastes from the human or animal food processing industry, wood chips, sawdust, wood pellets, bark, seeds, nuts, husks, and combinations thereof.
10. The method according to any one of claims 1 to 9, wherein the first time period is determined by the volume of the first reactor and the feed rates of the biomass and the solid heat carrier.
11. The method according to any one of claims 1 to 10, wherein the method is a continuous process.
12. The method according to any one of claims 1 to 11, wherein the moisture content of the biomass is less than 10 wt.%, preferably less than 5 wt.%, more preferably less than 3 wt.% or 4 wt.%.
13. The method according to any one of claims 1 to 12, wherein the temperature of the heat carrier in step (a) is 450 °C to 650 °C, preferably 450 °C to 600 °C.
14. The method according to any one of claims 1 to 13, wherein the first reactor or the first reaction zone comprises a mixing device and inlets for the biomass and the heat carrier, as well as an outlet for the mixture comprising the partially pyrolyzed biomass and the solid heat carrier, and optionally an outlet for the primary pyrolysis gas.
15. The method according to any one of claims 1 to 14, wherein the second reactor or the second reaction zone comprises means for separating solid particles and gas by gravity, and the second reactor further comprises an inlet for the mixture comprising the partially pyrolyzed biomass and the solid heat carrier, an outlet for the solids deposited or separated at the bottom of the second reactor, and an outlet for the pyrolysis gas.