A method for low-temperature carbonization of poplar wood and application method of derived charcoal

Abstract

The present application discloses a method for low-temperature carbonization of poplar wood and an application method of derived charcoal. The method for low-temperature carbonization of poplar wood comprises the following steps: S1, impregnating the poplar wood with a phosphate ammonium salt; S2, filtering and drying the poplar wood impregnated in step 1; S3, carbonizing the poplar wood filtered and dried in step 2; the application method of the derived charcoal of poplar wood uses the derived charcoal obtained by the low-temperature carbonization method of poplar wood as a pyrolysis raw material for pyrolysis, and the pyrolysis reaction temperature is between 500°C and 900°C; the present invention utilizes an impregnation method to load the poplar wood with different doses of phosphate ammonium salt, and compared with the traditional low-temperature carbonization treatment method, the parameters such as the energy yield of the solid phase product and the calorific value of the solid phase product of the poplar charcoal are better than those of the traditional low-temperature carbonization method, which has a significant promoting effect on the quality improvement of the carbonization of poplar wood; at the same time, by adding the phosphate ammonium salt, the poplar wood can be carbonized at a low temperature, which greatly reduces the cost.

Description

Technical Field

[0001] The present invention relates to the technical field related to low-temperature carbonization of biomass, and in particular to a low-temperature carbonization method for poplar wood and an application method of derived charcoal. Background Art

[0002] With economic development and global climate change, the world faces the challenge and responsibility of carbon emission reduction. Biomass is rich in biomass energy. Because it forms organisms through photosynthesis during its growth, biomass is widely used as a renewable carbon resource to replace other energy sources. During the biomass processing process, thermal treatment is a frequently used technology, which can be divided into three methods: gasification, pyrolysis, and carbonization. Biomass carbonization, also known as biomass dry distillation, is a thermal conversion technology that enriches biomass energy through high-temperature carbonization under anaerobic or oxygen-free conditions.

[0003] When carbonizing poplar biomass, researchers found that when the carbonization heat treatment conditions met the requirements of a final reaction temperature of 300°C and a holding time of 60 minutes, the energy yield, calorific value, and enhancement factor of the solid phase products of the carbonized poplar biomass could be increased to their peak values. However, the energy yield, calorific value, and enhancement factor of the solid phase products obtained by carbonizing poplar biomass using traditional methods were still low, and the quality improvement effect of carbonization on poplar biomass was not obvious. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a low-temperature carbonization method for poplar wood and an application method of derived charcoal, which utilizes an impregnation method to load poplar wood with different doses of ammonium phosphate salts. Compared with the traditional low-temperature carbonization treatment method, the parameters such as the energy yield of the solid phase product and the calorific value of the solid phase product of poplar charcoal are better than those of the traditional low-temperature carbonization method, which has a significant promoting effect on the quality improvement of poplar wood carbonization; at the same time, by adding ammonium phosphate salts, poplar wood can be carbonized at low temperature, greatly reducing costs.

[0005] In a first aspect, the present invention discloses a method for low-temperature carbonization of poplar wood, comprising the following steps:

[0006] S1, impregnation treatment of poplar wood with ammonium phosphate;

[0007] S2, filtering and drying the poplar wood after being soaked in step 1;

[0008] S3, carbonizing the poplar wood filtered and dried in step 2.

[0009] As an optimization solution of this application: the phosphate ammonium salt is selected from 2.9% diammonium hydrogen phosphate or 1.975% diammonium dihydrogen phosphate.

[0010] As a further limitation of the present application, the time for filtration and drying in S2 is 24 hours.

[0011] As a further limitation of the present application, the carbonization heat treatment conditions in S3 are as follows: a carbonization reaction initial temperature of 25°C, a heating rate of 5°C / min, a carbonization reaction final temperature of 300°C, and a holding time of 60 minutes.

[0012] In a second aspect, the present invention discloses an application method of poplar-derived charcoal, which is applied to the above-mentioned low-temperature carbonization method of poplar wood, and the obtained derivative charcoal is used as a pyrolysis raw material for pyrolysis, and the pyrolysis reaction temperature is between 500°C and 900°C.

[0013] The beneficial effects of the present invention are as follows:

[0014] First, considering the calorific value of the solid-phase product, the energy yield of the solid-phase product, the yield of the three-phase product, the element yield in the carbonized solid-phase product, the change in the removal of carbon, hydrogen and oxygen elements, and the enhancement factor, the various parameters of the poplar wood treated with ammonium phosphate salts after carbonization are improved compared to the poplar wood that has not been treated with ammonium phosphate salts, and the carbonization quality improvement effect of the poplar wood is more obvious; among them, the use of diammonium hydrogen phosphate with a concentration of 2.9% or ammonium dihydrogen phosphate with a concentration of 1.975% is most suitable for treating the poplar wood. On the other hand, whether the poplar wood is treated with diammonium hydrogen phosphate or with ammonium dihydrogen phosphate, the final temperature of the carbonization reaction is advanced compared to the poplar wood that has not been treated with ammonium phosphate salts; the advance of the final temperature of the carbonization reaction indicates that the carbonization of the poplar wood can be completed at a lower temperature, which greatly saves the cost caused by high temperature to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a graph showing the yield of three-phase products from carbonization of poplar wood treated with diammonium hydrogen phosphate at different concentrations.

[0016] Figure 2 This is the error diagram of the yield of three-phase products of carbonization of poplar wood treated with different concentrations of diammonium hydrogen phosphate.

[0017] Figure 3 This is a graph showing the yield of three-phase products of carbonization at different temperatures without treatment with ammonium phosphate salt.

[0018] Figure 4 This is the yield error diagram of the carbonized three-phase product at different temperatures without treatment with ammonium phosphate salt.

[0019] Figure 5 This is a line graph showing the energy yield of solid phase products from carbonization of poplar wood treated with different concentrations of diammonium hydrogen phosphate.

[0020] Figure 6 This is a line graph showing the energy yield of solid phase products from carbonized poplar wood without ammonium phosphate treatment at different temperatures.

[0021] Figure 7 This is the distribution diagram of element yield in carbonized solid products treated with different concentrations of diammonium hydrogen phosphate.

[0022] Figure 8 This is the element yield distribution diagram of the carbonized solid phase product at different temperatures without treatment with ammonium phosphate salt.

[0023] Figure 9 The removal curve of C, H, and O elements in the carbonization process treated with different concentrations of diammonium hydrogen phosphate.

[0024] Figure 10 The removal curves of C, H, and O elements during the carbonization process at different temperatures without treatment with ammonium phosphate.

[0025] Figure 11 This is a line graph of the enhancement factor of carbonized products treated with different concentrations of diammonium hydrogen phosphate.

[0026] Figure 12 This is a line graph of the enhancement factor of carbonized products at different temperatures without treatment with ammonium phosphate.

[0027] Figure 13 This is a graph showing the yield of three-phase products from carbonization of poplar wood treated with ammonium dihydrogen phosphate at different concentrations.

[0028] Figure 14 This is the error diagram of the yield of three-phase products of carbonization of poplar wood treated with different concentrations of ammonium dihydrogen phosphate.

[0029] Figure 15 This is a line graph showing the energy yield of solid phase products from carbonized poplar wood treated with different concentrations of ammonium dihydrogen phosphate.

[0030] Figure 16 This is the distribution diagram of element yield in carbonized solid products treated with different concentrations of ammonium dihydrogen phosphate.

[0031] Figure 17 The removal curve of C, H, and O elements in the carbonization process treated with different concentrations of ammonium dihydrogen phosphate.

[0032] Figure 18 This is a line graph of the enhancement factor of carbonized products treated with different concentrations of ammonium dihydrogen phosphate.

[0033] Figure 19 TG diagrams of the carbonization process of untreated poplar wood, 2.9% DAP-treated poplar wood, and 1.975% MAP-treated poplar wood.

[0034] Figure 20 DTG diagrams of the carbonization process of untreated poplar wood, 2.9% DAP-treated poplar wood, and 1.975% MAP-treated poplar wood.

[0035] Figure 21 This is a graph showing the change of NH3 with temperature under the action of ammonium phosphate.

[0036] Figure 22 This is a graph showing the change of CO2 with temperature under the action of ammonium phosphate.

[0037] Figure 23 This is a graph showing the change of H2O with temperature under the action of ammonium phosphate.

[0038] Figure 24 This is a graph showing the change of CO2 with temperature under the action of ammonium phosphate.

[0039] Figure 25 This is a diagram showing the output of small molecule gases from carbonization of poplar wood.

[0040] Figure 26 This is a graph showing the changes in small molecule gas output during carbonization of DAP-treated poplar wood.

[0041] Figure 27 This is a graph showing the changes in small molecule gas output during MAP-treated poplar wood carbonization. DETAILED DESCRIPTION

[0042] In order to clearly understand the technical solution of the present application, the low-temperature carbonization method of poplar wood and the application method of the derived carbon provided by the present application will be described in detail below with reference to specific embodiments and drawings.

[0043] The terms used in the following examples are for the purpose of describing specific embodiments only and are not intended to limit the present application. As used in the specification and claims of this application, the singular expressions "a," "an," "above," "the," and "this" are intended to include expressions such as "one or more," unless the context clearly indicates otherwise. It should also be understood that in the following examples of this application, "at least one," "one or more" refer to one, two, or more than two.

[0044] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "one embodiment," "some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0045] Example 1

[0046] This embodiment provides a method for low-temperature carbonization of poplar wood, which mainly includes the following steps:

[0047] Step 1: impregnating the poplar wood with diammonium phosphate (DAP) having a concentration of 2.9% for 2 hours;

[0048] Step 2, filtering and drying the poplar wood after impregnation in step 1, wherein the filtering and drying time is 24 hours;

[0049] Step 3, carbonizing the poplar wood filtered and dried in step 2, wherein the carbonization heat treatment conditions are as follows: a carbonization reaction initial temperature of 25°C, a heating rate of 5°C / min, a carbonization reaction final temperature of 300°C, and a heat preservation time of 60 minutes.

[0050] Comparative Example 1

[0051] A method for carbonizing poplar wood mainly comprises the following steps:

[0052] Step 1: carbonize the poplar wood. The carbonization heat treatment conditions are as follows: a carbonization reaction initial temperature of 25°C, a heating rate of 5°C / min, a carbonization reaction final temperature of 300°C, and a heat preservation time of 60 minutes.

[0053] The experimental data obtained in Example 1 were compared with the experimental data obtained in Comparative Example 1. The specific experiments are as follows.

[0054] Experiment 1: Comparison of the yields of three-phase products from carbonized poplar wood treated with and without diammonium hydrogen phosphate treatment.

[0055] refer to Figure 1 、 Figure 2 , Figure 1 The graph shows the yield of three-phase products of carbonization of poplar wood treated with diammonium hydrogen phosphate at different concentrations. Figure 2 The graph shows the yield error of the three-phase carbonization products of poplar wood treated with diammonium hydrogen phosphate at different concentrations; Figure 3 、 Figure 4 , Figure 3 The graph shows the yield of three-phase carbonization products at different temperatures without treatment with ammonium phosphate. Figure 4 Shown is the yield error diagram of the carbonized three-phase product at different temperatures without treatment with ammonium phosphate salt.

[0056] pass Figure 1 、 Figure 2 Respectively Figure 3 、 Figure 4The following analysis was conducted after comparison: At a final carbonization temperature of 300°C, the carbonization process of poplar wood treated with diammonium phosphate (DAP) resulted in a higher yield of the carbonized solid phase (C) product and a lower yield of the gas phase (A) product compared to the carbonization process of poplar wood without DAP treatment. With increasing DAP treatment concentration, the yield of the carbonized solid phase product increased, while the yields of the gas phase product and the liquid phase (B) product decreased. In terms of the magnitude of the changes in the three-phase yields, lower DAP treatment concentrations resulted in a higher increase in the solid phase product yield, indicating that DAP treatment has a significant impact on the yields of the carbonized solid phase product and the gas phase product. At a DAP treatment concentration of 2.9%, the yield of the carbonized solid phase product increased by approximately 11% compared to the yield of the carbonized solid phase product without DAP treatment, while the yield of the carbonized gas phase product decreased by approximately 12%. The yield of the liquid phase product remained almost unchanged at lower concentrations. In summary, when the concentration of diammonium hydrogen phosphate treated poplar wood raw materials is less than 2.9% (including 2.9%), compared with the poplar wood not treated with diammonium hydrogen phosphate, the yield of carbonized solid phase products of poplar wood shows a significant increasing trend and the yield of carbonized gas phase products shows a significant decreasing trend.

[0057] The increase in the solid-phase product yield and the decrease in the gas-phase yield can be understood as the formation of a mutually penetrating and cross-linked diammonium hydrogen phosphate-biopolymer complex between diammonium hydrogen phosphate and poplar wood during impregnation; during the carbonization process, diammonium hydrogen phosphate decomposes under heat to produce substances such as phosphoric acid and metaphosphoric acid, which in turn promote the development of the poplar wood pore structure, and phosphoric acid and metaphosphoric acid are subsequently converted into phosphorus pentoxide, which in turn catalyzes the carbonization process of poplar wood and other oxides, thereby deepening the carbonization process of poplar wood, reducing the generation of combustible gas, and increasing the solid-phase product yield.

[0058] Experiment 2: Comparison of the energy yield of solid phase products from carbonized poplar wood treated with and without diammonium hydrogen phosphate treatment.

[0059] refer to Figure 5 The figure shows the energy yield of solid phase products of poplar wood treated with different concentrations of diammonium hydrogen phosphate; Figure 6 Shown is a line graph of the energy yield of solid phase products of poplar wood carbonized without treatment with ammonium phosphate at different temperatures.

[0060] pass Figure 5 and Figure 6After comparison, the following analysis was made: when the final carbonization temperature was 300℃, with the increase of diammonium hydrogen phosphate treatment concentration, the energy yield of carbonized solid phase products first increased and then decreased; when the diammonium hydrogen phosphate treatment concentration was within 5.8%, the energy yield of carbonized solid phase products showed a strong increasing trend, while the energy yield decreased more sharply in the diammonium hydrogen phosphate treatment concentration stage between 5.8% and 17.4%. When the concentration was higher than 17.4%, the energy yield of carbonized solid phase products decreased more slowly; when the diammonium hydrogen phosphate treatment concentration was less than 5.8%, the energy yield of carbonized poplar wood treated with diammonium hydrogen phosphate showed a significant increasing trend compared with that of poplar wood not treated with diammonium hydrogen phosphate. In summary, when the diammonium hydrogen phosphate treatment concentration of poplar wood raw materials was within 5.8%, the energy yield of carbonized solid phase products of poplar wood showed a significant increasing trend compared with that of poplar wood not treated with diammonium hydrogen phosphate.

[0061] When the low diammonium hydrogen phosphate treatment concentration is less than 5.8%, the calorific value of the solid phase product decreases slightly, which is coupled with an increased energy yield. In the concentration range of 5.8%-17.4%, although the carbonized solid phase yield is still increasing, the calorific value of the solid phase product of the treated poplar charcoal drops sharply at this time, resulting in a decrease in the energy yield of the solid phase product. When the concentration is above 17.4%, due to the treatment with excessive diammonium hydrogen phosphate, the calorific value of the solid phase product is no longer enough to match the calorific value of the solid phase product of the original uncarbonized poplar, resulting in a very low energy yield of the carbonized solid phase product at this time.

[0062] Experiment 3: Comparison of element yield distribution in carbonized solid products treated with and without diammonium hydrogen phosphate treatment.

[0063] refer to Figure 7 The figure shows the element yield distribution of carbonized solid products treated with diammonium phosphate at different concentrations; Figure 8 Shown is the element yield distribution diagram of the carbonized solid phase product at different temperatures without treatment with ammonium phosphate salt.

[0064] pass Figure 7 and Figure 8Comparative analysis revealed the following: At a final carbonization temperature of 300°C, the carbon yield of poplar charcoal obtained after diammonium phosphate treatment initially increased and then decreased, while the H and O yields initially decreased and then increased with increasing diammonium phosphate concentration. A diammonium phosphate treatment concentration below 5.8% yielded a higher carbon yield and lower O yield than that obtained without diammonium phosphate addition. A diammonium phosphate treatment concentration of 2.9% resulted in a higher carbon yield than untreated poplar and a lower O yield. Higher diammonium phosphate concentrations resulted in lower carbon yields and higher O yields than untreated poplar charcoal. This suggests that high diammonium phosphate treatment hinders carbon enrichment and oxygen stripping during the carbonization process. In summary, when diammonium phosphate treatment concentrations are below 5.8%, the O content in the poplar biochar decreases significantly, while the carbon content increases significantly, compared to untreated poplar.

[0065] Experiment 4: Comparison of the changes in the removal of C, H, and O elements during the carbonization process with and without diammonium hydrogen phosphate treatment.

[0066] refer to Figure 9 The graph shows the removal curves of C, H, and O elements during the carbonization process treated with diammonium phosphate at different concentrations; Figure 10 Shown are the C, H, and O element removal curves during the carbonization process at different temperatures without treatment with ammonium phosphate.

[0067] pass Figure 9 and Figure 10 Comparison revealed the following analysis: At a final carbonization temperature of 300°C, as the diammonium phosphate concentration increased, the dehydrogenation and deoxygenation indices during the carbonization process first increased and then decreased, while the decarbonization index first decreased and then increased. This trend corroborated the trends in the yields of carbon, hydrogen, and oxygen in the carbonized solid phase products observed in Experiment 3. While the decarbonization index of poplar wood treated with 2.9% diammonium phosphate reached its lowest value at 5.8%, the deoxygenation index peaked at 2.9%. In summary, when the diammonium phosphate concentration was maintained below (inclusive of) 2.9%, the decarbonization index showed a significant decrease, while the deoxygenation index showed a significant increase, compared to untreated poplar wood.

[0068] Poplar wood treated with low-concentration diammonium phosphate (DAP) exhibits a higher deoxygenation index and a lower decarbonization index than untreated wood. Low-concentration DAP decomposes upon heating to produce phosphoric acid and phosphorus pentoxide. These react with the hydroxyl groups of hemicellulose and cellulose in the wood, catalyzing the dehydration of these polysaccharides and promoting their hydrolysis into oligosaccharides and monosaccharides. Phosphoric acid also activates the pore structure of poplar charcoal. As the DAP concentration increases, the deoxygenation and dehydrogenation indices decrease, while the decarbonization index recovers. Excessive phosphoric acid directly esterifies the wood into charcoal, producing phosphorus pentoxide. The resulting high-molecular-weight cross-linked products adhere to the wood's surface, forming a heat- and oxygen-isolating layer that hinders carbonization.

[0069] Experiment 5: Comparison of the higher calorific value of the carbonized solid phase products treated with and without diammonium hydrogen phosphate treatment.

[0070] Reference Table 1 shows the changes in higher calorific value of carbonized solid phase products treated with diammonium hydrogen phosphate at different concentrations:

[0071]

[0072] Temperature / ℃ 0 180 220 260 280 300 320 High calorific value / KJ / kg 17.68 18.27 18.61 20.56 20.52 24.67 27.87

[0073] At a final carbonization temperature of 300°C, the calorific value of the carbonized solid phase product gradually decreased with increasing diammonium phosphate concentration. When the diammonium phosphate concentration was greater than 5.8%, the calorific value of the carbonized solid phase product of untreated poplar wood was 24.7 kJ / kg. When the diammonium phosphate concentration was 17.4%, the calorific value of the carbonized solid phase product was 18.7 kJ / kg, a decrease of 6 kJ / kg. This indicates that high concentrations of diammonium phosphate treatment have a negative effect on the calorific value of poplar wood charcoal. The calorific value of the carbonized solid phase product of poplar wood treated with 2.9% diammonium phosphate only decreased by 0.4 kJ / kg compared to untreated poplar wood. In summary, when the diammonium phosphate concentration was maintained below 5.8%, the calorific value of the carbonized solid phase product did not decrease significantly compared to untreated poplar wood.

[0074] Treatment with high concentrations of diammonium hydrogen phosphate will produce a large amount of phosphoric acid and phosphorus pentoxide, which will cause the poplar wood to undergo esterification and carbonization reactions, with less oxygen stripping. The excessive amount of diammonium hydrogen phosphate may even cause the oxygen content in the biochar to increase, significantly reducing the calorific value of the carbonized solid phase product.

[0075] Experiment 6: Comparison of the evolution of enhancement factor of poplar charcoal treated with and without diammonium hydrogen phosphate treatment.

[0076] refer to Figure 11The figure shows the enhancement factor of carbonization products treated with different concentrations of diammonium hydrogen phosphate; Figure 12 Shown is a line graph of the enhancement factor of carbonized products at different temperatures without treatment with ammonium phosphate.

[0077] pass Figure 13 and Figure 14 The following analysis was conducted: At a final carbonization temperature of 300°C, the enhancement factor decreased with increasing DAP concentration, with varying degrees of decline at different concentration levels. When the DAP concentration was less than 5.8%, the enhancement factor decreased more slowly, due to the increased energy yield of the solid-phase products and a slow decrease in the calorific value of the carbonized solid-phase products. When the DAP concentration was between 5.8% and 17.4%, the enhancement factor decreased rapidly. This is because high DAP concentrations cause the poplar wood to esterify into charcoal, preventing oxygen removal and carbon enrichment, which reduces the calorific value of the solid-phase products of the poplar charcoal. When the DAP concentration was above 17.4%, the enhancement factor slowly decreased to below 1, indicating that high DAP treatment caused a sharp decrease in the calorific value of the poplar wood. In summary, when the DAP concentration of poplar wood was less than 5.8%, the enhancement factor was able to maintain a high value compared to untreated poplar wood.

[0078] Analyzing the data from Experiments 1 to 6, the maximum solid-phase product energy yield was achieved when treating poplar wood with a 5.8% diammonium hydrogen phosphate concentration, indicating that a 5.8% diammonium hydrogen phosphate concentration is appropriate. Treating poplar wood with a diammonium hydrogen phosphate concentration above 2.9% hinders carbon enrichment and oxygen stripping in the carbonized solid-phase product. When treating poplar wood with a 2.9% diammonium hydrogen phosphate concentration, the carbon yield reached a peak, while the oxygen yield reached a low peak, indicating that a 2.9% diammonium hydrogen phosphate concentration is appropriate. The deoxygenation index reached a peak when treating poplar wood with a 2.9% diammonium hydrogen phosphate concentration, indicating that a 2.9% diammonium hydrogen phosphate concentration is appropriate. A 2.9% diammonium hydrogen phosphate concentration effectively preserves the calorific value of the carbonized solid-phase product, indicating that a 2.9% diammonium hydrogen phosphate concentration is appropriate. Taking into account the calorific value of the solid phase product, the energy yield of the solid phase product and the yield of the three-phase product, the element yield in the carbonized solid phase product, the change in the removal of carbon, hydrogen and oxygen elements, and the enhancement factor, the use of diammonium hydrogen phosphate with a concentration of 2.9% is more suitable for the treatment of poplar wood, and the diammonium hydrogen phosphate with a concentration of 2.9% in this application is only specific for poplar wood biomass.

[0079] Example 2

[0080] This embodiment provides a method for low-temperature carbonization of poplar wood, which mainly includes the following steps:

[0081] Step 1: impregnating the poplar wood with 1.975% diammonium phosphate (MAP) for 2 hours;

[0082] Step 2, filtering and drying the poplar wood after impregnation in step 1, wherein the filtering and drying time is 24 hours;

[0083] Step 3, carbonizing the poplar wood filtered and dried in step 2, wherein the carbonization heat treatment conditions are as follows: a carbonization reaction initial temperature of 25°C, a heating rate of 5°C / min, a carbonization reaction final temperature of 300°C, and a heat preservation time of 60 minutes.

[0084] The experimental data obtained in Example 2 were compared with the experimental data obtained in Comparative Example 1. The specific experiments are as follows.

[0085] Experiment 7: Comparison of the yields of three-phase products from carbonized poplar wood treated with and without ammonium dihydrogen phosphate treatment.

[0086] refer to Figure 13 、 Figure 14 , Figure 15 The graph shows the yield of three-phase products of carbonization of poplar wood treated with ammonium dihydrogen phosphate at different concentrations. Figure 16 Shown is the error diagram of the yield of three-phase products of carbonization of poplar wood treated with different concentrations of ammonium dihydrogen phosphate.

[0087] pass Figure 15 、 Figure 16 Respectively Figure 3 、 Figure 4 After comparison, the following analysis was made: when the final carbonization temperature was 300℃, with the increase of the diammonium phosphate treatment concentration, the carbonized solid phase yield of the treated poplar wood gradually increased, the carbonized gas phase yield gradually decreased, and the carbonized liquid phase yield showed a significant downward trend when the diammonium phosphate treatment concentration was above 3.95%; compared with the carbonized three-phase yield of poplar wood treated with 1.975% diammonium phosphate, the carbonized solid phase product yield increased by 12%, while the carbonized gas phase product yield decreased by 13%.

[0088] In summary, the yield of carbonized solid products of poplar wood treated with ammonium dihydrogen phosphate increases and the yield of carbonized gas products decreases compared with the poplar wood not treated with ammonium dihydrogen phosphate.

[0089] When the concentration of ammonium dihydrogen phosphate used to treat poplar wood is below 3.95%, the solid phase yield is improved because ammonium dihydrogen phosphate reduces the precipitation of volatile matter of hemicellulose and cellulose, making the liquid output more inclined to the direction of oxygen-containing organic matter.

[0090] Experiment 8: Comparison of the energy yield of solid phase products from carbonized poplar wood treated with and without ammonium dihydrogen phosphate treatment.

[0091] refer to Figure 15 Shown is a line graph of the energy yield of solid phase products from carbonization of poplar wood treated with different concentrations of ammonium dihydrogen phosphate.

[0092] pass Figure 17 and Figure 6 After comparison, the following analysis was made: when the final carbonization temperature was 300°C, the energy yield of the carbonized solid phase of poplar wood treated with low-concentration dihydrogen ammonium phosphate increased sharply. When the concentration of dihydrogen ammonium phosphate used to treat the poplar wood was higher than 1.975%, the energy yield of the carbonized solid phase product of poplar wood dropped sharply; when the concentration of dihydrogen ammonium phosphate was higher than 3.95%, the energy yield of the carbonized product of poplar wood began to decline slowly.

[0093] In summary, when the concentration of ammonium dihydrogen phosphate treated poplar wood raw materials is within 1.975%, the energy yield of the solid phase product of poplar wood carbonization has an obvious increasing trend compared with the poplar wood not treated with ammonium dihydrogen phosphate.

[0094] With the continuous increase of ammonium dihydrogen phosphate concentration, the yield of carbonized solid-phase products showed an upward trend. However, the calorific value of the carbonized solid-phase products increased only when the ammonium dihydrogen phosphate treatment concentration was 1.975%. When the ammonium dihydrogen phosphate treatment concentration reached above 3.95%, the calorific value of the carbonized solid-phase products showed a slow downward trend, which eventually led to a slow downward trend in the energy yield of the carbonized products. Among them, the enhancement factor is an intuitive reflection of the calorific value of the carbonized solid-phase products. The energy yield of the carbonized products is coupled with the solid-phase product yield and the enhancement factor, that is, the energy yield of the carbonized products is the product of the solid-phase product yield and the enhancement factor.

[0095] Experiment 9: Comparison of element yield distribution in carbonized solid products treated with and without ammonium dihydrogen phosphate treatment.

[0096] refer to Figure 16 Shown is the element yield distribution diagram of the carbonized solid phase product treated with different concentrations of ammonium dihydrogen phosphate.

[0097] pass Figure 18 and Figure 8Comparative analysis revealed the following: At a final carbonization temperature of 300°C, as the diammonium phosphate concentration increased, the carbon yield in the poplar wood carbonization product first increased and then decreased, while the oxygen and hydrogen elements exhibited the opposite trend (first decreased and then increased). The carbon yield increased by 6.27%, from 64.07% in the untreated product to 70.34% in the 1.975% diammonium phosphate treatment. The oxygen yield decreased by 5.487%, from 30.257% in the untreated product to 24.77% in the 1.975% diammonium phosphate treatment. This indicates that a 1.975% diammonium phosphate treatment effectively promotes deoxidation and carbonization during the poplar wood carbonization process. At diammonium phosphate concentrations above 3.95%, the carbon yield of the carbonized product was lower than that of the untreated poplar wood charcoal, while the oxygen yield was higher than that of the untreated poplar wood charcoal. This indicates that low concentrations of ammonium dihydrogen phosphate have a significant promoting effect on the carbonization and quality improvement of poplar wood, while too high a concentration will greatly hinder the carbonization and quality improvement effect.

[0098] In summary, when the concentration of ammonium dihydrogen phosphate treated poplar wood raw materials was 1.975%, the O element in the poplar wood biochar showed a significant downward trend, while the C element showed a significant upward trend, compared with the poplar wood not treated with ammonium dihydrogen phosphate.

[0099] Experiment 10: Comparison of the changes in the removal of C, H, and O elements during the carbonization process with and without ammonium dihydrogen phosphate treatment.

[0100] refer to Figure 17 Shown is the removal curve of C, H, and O elements during the carbonization process treated with ammonium dihydrogen phosphate at different concentrations.

[0101] pass Figure 19 and Figure 10 The following analysis was made after comparison: At a final carbonization temperature of 300°C, as the diammonium phosphate concentration increased, the O and H elements first increased and then decreased during the carbonization process, while the C element exhibited a more zigzag trend. At both 1.975% and 11.85% diammonium phosphate concentrations, the C element achieved lower values, reaching its lowest value at 1.975% diammonium phosphate, while the O and H elements reached their peaks. This indicates that a relatively good carbonization deoxidation index and a low decarbonization index can be achieved at a diammonium phosphate concentration of 1.975%.

[0102] Experiment 11: Comparison of the higher calorific value of carbonized solid products treated with and without ammonium dihydrogen phosphate treatment.

[0103] MAP treatment concentration / % 0 1.975 3.95 11.85 19.75 High temperature calorific value / KJ / kg 24.67 26.45 22.26 18.65 15.94

[0104] At a final carbonization temperature of 300°C, the calorific value of the carbonized solid phase product first increased and then decreased with increasing diammonium phosphate concentration. The calorific value of the solid phase product of poplar wood treated with 1.975% diammonium phosphate increased compared to that of the untreated solid phase product. The solid phase product calorific value of the untreated poplar wood charcoal was 24.67% kJ / kg, while the 1.975% diammonium phosphate treated poplar wood charcoal achieved 26.45 kJ / kg, a 1.78 kJ / kg increase in solid phase product calorific value. However, when the diammonium phosphate concentration of the treated poplar wood reached above 1.975%, the calorific value of the solid phase product began to decrease.

[0105] Experiment 12: Comparison of the evolution of enhancement factor of poplar charcoal treated with and without ammonium dihydrogen phosphate treatment.

[0106] refer to Figure 18 Shown is a line graph of the enhancement factor of carbonized products treated with different concentrations of ammonium dihydrogen phosphate.

[0107] pass Figure 21 and Figure 14 The following analysis was made after comparison: At a final carbonization temperature of 300°C, treatment with ammonium dihydrogen phosphate significantly increased the enhancement factor of the carbonized solid phase product. This enhancement factor increased at a treatment concentration of 1.975% ammonium dihydrogen phosphate. However, at concentrations above 1.975%, the enhancement factor of the carbonized solid phase product rapidly decreased, and the rate of decrease slowed at concentrations above 3.95%. At a treatment concentration of 1.975%, the enhancement factor increased, and the calorific value of the solid phase product also increased.

[0108] Taking into account the calorific value of the solid-phase product, the energy yield of the solid-phase product and the yield of the three-phase product, the element yield in the carbonized solid-phase product, the change in the removal of carbon, hydrogen and oxygen elements, and the enhancement factor, it is more appropriate to use ammonium dihydrogen phosphate with a concentration of 1.975% for the treatment of poplar wood, and the ammonium dihydrogen phosphate with a concentration of 1.975% in this application is also specifically for poplar wood biomass.

[0109] Furthermore, under the action of carbonate ammonium salts (DAP and MAP) in Examples 1 and 2, the thermal weight loss and gas release patterns of poplar wood are as follows:

[0110] Figure 19 The TG diagrams of the carbonization process of untreated poplar wood, 2.9% DAP-treated poplar wood, and 1.975% MAP-treated poplar wood are shown. Figure 20The DTG plots of the carbonization process of untreated poplar wood, 2.9% DAP-treated poplar wood, and 1.975% MAP-treated poplar wood are shown. The TG curves indicate that treatment of poplar wood with diammonium hydrogen phosphate or monoammonium dihydrogen phosphate improves the residual mass after carbonization compared to untreated poplar wood. The residual mass increased from 33.6% to 47.9% after treatment with 2.9% diammonium hydrogen phosphate, and from 33.6% to 40.5% after treatment with 1.975% monoammonium dihydrogen phosphate. The phenolic and alcoholic hydroxyl groups in the hemicellulose and cellulose in the poplar wood undergo cross-linking and esterification with all phosphate groups and other polymers in monoammonium dihydrogen phosphate and monoammonium dihydrogen phosphate to form phosphate esters and polyphosphates, which attach to the surface of the pore structure of the poplar wood charcoal, reducing volatile matter production and increasing the residual mass of the solid phase after carbonization. According to the comparative analysis of the DTG curves, there is only one weight loss peak at 318°C during the low-temperature carbonization of untreated poplar wood, which is due to the maximum weight loss rate of hemicellulose and cellulose in the poplar wood reaching 0.77wt.% / min; while the carbonization process of poplar wood treated with diammonium hydrogen phosphate and ammonium dihydrogen phosphate reaches the corresponding carbonization temperature of the maximum weight loss rate in advance, and the maximum weight loss rates corresponding to diammonium hydrogen phosphate and ammonium dihydrogen phosphate are higher than the maximum weight loss rate of carbonization of untreated poplar wood; the maximum weight loss rate of poplar wood treated with diammonium hydrogen phosphate is 1.23wt.% / min at 280°C, which is 38°C earlier than the temperature corresponding to the maximum weight loss rate of untreated poplar wood, and the weight loss rate is increased by 0.46; the maximum weight loss rate of poplar wood treated with diammonium dihydrogen phosphate is 1.35wt.% / min at 288°C, which is 30°C earlier than the temperature corresponding to the maximum weight loss rate of untreated poplar wood, and the weight loss rate is increased by 0.58. Both diammonium hydrogen phosphate and ammonium dihydrogen phosphate increased the carbonization activity of poplar wood and accelerated its carbonization process. The carbonization reaction of untreated poplar wood was completed at temperatures above 350°C, while the carbonization reaction of poplar wood treated with diammonium hydrogen phosphate and ammonium dihydrogen phosphate was essentially complete at 303°C and 310°C, respectively. These results suggest that treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate can advance the carbonization temperature and intensify the carbonization process to varying degrees. Compared to the carbonization start temperature of 197°C for untreated poplar wood, the reaction temperature of poplar wood treated with diammonium hydrogen phosphate and ammonium dihydrogen phosphate was advanced to 185°C, which is likely due to the thermal degradation of hemicellulose and the subsequent esterification of a small amount of the material. A weight loss shoulder peak was observed for both treated poplar wood and the wood. This weight loss peak is associated with the thermal degradation of some cellulose in the wood. At the maximum weight loss peak, a significant amount of hemicellulose and cellulose undergoes thermal cracking and carbonization, leading to crosslinking reactions.

[0111] Figure 21-Figure 27 The following diagram shows the evolution of small molecule gases during the carbonization process of poplar wood and poplar wood treated with DAP and MAP. Figure 21-24 Comparison of the intensities of different small molecule gases produced during the carbonization process of poplar wood treated with different methods. Figure 25-27The figures are respectively the output of small molecule gases during the carbonization of poplar wood, the output of small molecule gases during the carbonization of poplar wood treated with diammonium hydrogen phosphate, and the output of small molecule gases during the carbonization of poplar wood treated with ammonium dihydrogen phosphate. It can be seen that among the four small molecule gas components, H2O and CO2 are the main components of the gas during the carbonization of untreated poplar wood, while H2O is the main component of the gas during the carbonization of poplar wood treated with diammonium hydrogen phosphate and diammonium dihydrogen phosphate, and the output of the other three small molecule gases is relatively small.

[0112] Depend on Figure 21 The NH3 precipitation peak of untreated poplar wood is at 320°C, while treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate advances the corresponding temperature of the precipitation peak to 270°C and 283°C, respectively. Furthermore, treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate also reduces the intensity of the precipitation peak. This can be understood as the diammonium hydrogen phosphate and ammonium dihydrogen phosphate treatments advance the temperature of the carbonization reaction, thereby advancing the corresponding temperature of the ammonia precipitation peak. The stronger ammonia precipitation peak of diammonium hydrogen phosphate-treated poplar wood than that of ammonium dihydrogen phosphate can be attributed to the thermal decomposition of diammonium hydrogen phosphate to produce ammonium dihydrogen phosphate and ammonia.

[0113] Depend on Figure 22 Treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate not only advances the corresponding temperature of the CH4 precipitation peak but also alters the CH4 precipitation pattern in poplar wood. Untreated poplar wood exhibits a methane precipitation peak at 330°C and a shoulder at 297°C. Treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate advances the precipitation peak to 273°C and 287°C, respectively, and shifts the shoulder to temperatures beyond the corresponding precipitation peak. Methane production generally occurs through two pathways: first, at lower heat treatment temperatures, through the cleavage of methoxyl groups (-OCH3) directly attached to the benzene rings of lignin; second, at higher temperatures, through the cleavage of methyl (-CH3) and methylene (-CH2-) side chains of the basic units (glucose, glycosyl, and phenylmethane) in cellulose, hemicellulose, and lignin. The swelling and oxidation of the phosphate groups in diammonium hydrogen phosphate and ammonium dihydrogen phosphate accelerates the depolymerization of the basic units in hemicellulose, cellulose, and lignin in poplar wood.

[0114] Depend on Figure 23 It can be seen that treatment with diammonium hydrogen phosphate and ammonium dihydrogen phosphate advances the peak temperature of HO precipitation, from 320°C in the untreated wood to 270°C and 283°C, respectively. The HO originates primarily from free and bound water in the biomass, as well as dehydroxylation reactions of hemicellulose, cellulose, and lignin. Therefore, the phosphate groups present in DAP and MAP promote depolymerization and hydrolysis of poplar wood, accelerating the onset of dehydroxylation.

[0115] Depend on Figure 24It can be seen that treatment with DAP and MAP not only advances the CO2 evolution temperature but also reduces the CO2 evolution intensity. CO2 is generated by decarbonylation and decarboxylation of C=O and -COOH groups attached to cellulose and hemicellulose. It is speculated that the carboxyl groups react with ammonia in DAP and MAP to produce amide functional groups, resulting in a significant reduction in CO2 production. Furthermore, DAP can be thermally decomposed into ammonia and MAP, so the CO2 signal produced by MAP-treated poplar wood is stronger than that produced by DAP-treated poplar wood.

[0116] In summary, whether the poplar wood is treated with diammonium hydrogen phosphate or ammonium dihydrogen phosphate, the final temperature of the carbonization reaction is advanced compared with the poplar wood that has not been treated with ammonium phosphate. The advance of the final temperature of the carbonization reaction indicates that the carbonization of poplar wood can be completed at a lower temperature, which greatly saves the cost caused by high temperature to a certain extent.

[0117] Example 3

[0118] The derived carbon obtained in Example 1 and Example 2 was used as a pyrolysis raw material, and a pyrolysis reaction was carried out at a temperature of 500°C-900°C.

[0119] The pyrolysis of untreated derivative charcoal showed that the phenolic compounds in the liquid phase products were mainly phenols, with a content of up to 64.8%, indicating that the lignin that was not degraded by carbonization decomposed in large quantities during this pyrolysis stage to produce a large amount of phenolic compounds, and at the same time produced 7.09% of toluene compounds.

[0120] Reference Table 4 shows the main components and relative contents of the liquid phase products of untreated poplar charcoal pyrolysis:

[0121]

[0122] Reference Table 5 shows the main components and relative contents of the liquid phase products of the pyrolysis of poplar charcoal treated with diammonium hydrogen phosphate:

[0123]

[0124] The content of phenolic compounds in the liquid phase product of poplar charcoal re-pyrolysis treated with diammonium hydrogen phosphate is only 27.49%, which is far less than the amount of phenols in the liquid phase product of poplar charcoal, while the content of (4-hydroxyphenyl)phosphoric acid can reach 17.26%, and the content of toluene compounds is only 0.91%, which is far less than the 7.09% toluene compound content in the liquid phase product of poplar charcoal re-pyrolysis.

[0125] Reference Table 6 shows the main components and relative contents of the liquid phase product of the pyrolysis of poplar charcoal treated with ammonium dihydrogen phosphate:

[0126]

[0127] The (4-hydroxyphenyl) phosphate content of poplar wood-derived charcoal treated with diammonium phosphate reached 29.02%, exceeding the content in the liquid phase product of poplar wood charcoal pyrolysis treated with diammonium phosphate. Phenolic compound content reached 45%, while toluene content was only 1.71%. Treatment with diammonium phosphate also reduced the content of toluene compounds in the liquid phase product.

Claims

1. A method for low-temperature carbonization of poplar wood, characterized in that: The following steps are involved: S1, impregnating the poplar wood with ammonium phosphate; the impregnation time is 2 hours; S2, filtering and drying the poplar wood after impregnation in step 1; the filtering and drying time is 24 hours; S3, carbonizing the poplar wood filtered and dried in step 2; the carbonization heat treatment conditions are as follows: a carbonization reaction starting temperature of 25°C, a heating rate of 5°C / min, a carbonization reaction final temperature of 300°C, and a holding time of 60 minutes; The ammonium phosphate salt is 2.9% diammonium hydrogen phosphate.

2. A method for applying poplar-derived charcoal, characterized in that: The low-temperature carbonization method for poplar wood according to claim 1 is applied to pyrolysis of the derived charcoal obtained at a final carbonization reaction temperature of 300°C as a pyrolysis raw material, and the pyrolysis reaction temperature is between 500°C and 900°C.

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