Mechanical-chemical synergistic biomass dehydration pretreatment method and system

Abstract

The invention discloses a mechanical-chemical synergistic biomass dehydration pretreatment method and system. The method comprises the following steps: crushing biomass to obtain biomass particles, and testing the initial water content of the biomass particles; spraying a composite dehydrating agent into the biomass particles for modification treatment to obtain modified biomass; sequentially carrying out primary low-pressure squeezing treatment and secondary high-pressure squeezing treatment on the modified biomass; and adjusting the pH value of the wastewater obtained by filter pressing. According to the method, the biomass dehydration treatment process is carried out through mechanical-chemical cooperation, and the water content of the biomass obtained through treatment is remarkably reduced. The alkaline solution is used for neutralizing the residual acidity of the wastewater obtained by filter pressing, and the neutralized wastewater can be circularly used for preparing a dehydrating agent, so that the resource waste is reduced.

Description

Technical Field

[0001] This invention relates to the field of biomass energy pretreatment technology, and in particular to a mechanical-chemical synergistic biomass dehydration pretreatment method and system. Background Technology

[0002] Currently, single-shaft screw presses or plate and frame filter presses are commonly used for mechanical dehydration of biomass. However, after processing by these methods, the moisture content of the biomass remains as high as 40-50%, while direct combustion requires a moisture content below 20%, and efficient fermentation requires a moisture content below 30%. Therefore, biomass processed by single-shaft screw presses or plate and frame filter presses does not meet the requirements for direct combustion and efficient fermentation. Furthermore, existing biomass dehydration processes require thermally assisted mechanical dehydration, consuming over 80 kWh / ton, resulting in poor economic efficiency.

[0003] Dehydrating agents are often used in conjunction with biomass dehydration processes. Traditional dehydrating agents such as CaO and PAM (polyacrylamide) are added at a rate of more than 5%. Due to the large amount of dehydrating agents added, alkali metal residues are left, which corrode equipment, damage the organic components of biomass, and reduce methane yield. Studies have shown that when the amount of CaO added is 5%, biogas production decreases by 22%. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a mechanical-chemical synergistic biomass dehydration pretreatment method and system.

[0006] In a first aspect, the present invention proposes a mechanical-chemical synergistic biomass dehydration pretreatment method, comprising the following steps: (1) The biomass was crushed to obtain biomass pellets, and their initial moisture content was tested; (2) Modified biomass is obtained by spraying a composite dehydrating agent onto the biomass pellets; (3) The modified biomass is subjected to a first-stage low-pressure pressing treatment and a second-stage high-pressure pressing treatment in sequence; (4) Adjust the pH value of the wastewater obtained by pressure filtration.

[0007] Furthermore, the biomass particles have a particle size of 3-5 cm.

[0008] Furthermore, the composite dehydrating agent includes citric acid and diatomaceous earth.

[0009] Furthermore, the amount of citric acid added is 0.3% to 0.8% of the mass of the biomass dry substrate.

[0010] Furthermore, the amount of diatomaceous earth added is 1% to 3% of the mass of the biomass dry substrate.

[0011] Furthermore, in step (2), the time for spraying the composite dehydrating agent onto the biomass pellets for modification treatment is 15-30 minutes.

[0012] Furthermore, the pressure of the first-stage low-pressure pressing is 1~3MPa, and the temperature is room temperature.

[0013] Furthermore, the pressure of the secondary high-pressure press is 8~12MPa, and the temperature is 45~50℃.

[0014] Furthermore, in step (4), the pH value of the wastewater obtained by pressure filtration is adjusted to 6.5~7.5.

[0015] Secondly, the present invention provides a system applicable to the preprocessing method proposed in the first aspect above, comprising: A crushing device, the crushing device being used to crush biomass; A chemical modification device is located downstream of the crushing device, in which the crushed biomass reacts with a composite dehydrating agent. The mechanical pressing device is located downstream of the chemical modification device and includes a primary low-pressure pressing device and a secondary high-pressure pressing device. A neutralization and adjustment device is located downstream of the mechanical pressing device and is used to adjust the pH value of the filtered wastewater.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a mechanical-chemical synergistic process for biomass dehydration, resulting in a significant reduction in the water content of the treated biomass.

[0017] This invention utilizes an alkaline solution to neutralize the residual acidity of the wastewater obtained from pressure filtration. The neutralized wastewater can be recycled for the preparation of dehydrating agents, reducing resource waste. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of the mechanical-chemical synergistic biomass dehydration pretreatment method of the present invention; Figure 2 This is a schematic diagram of the mechanical-chemical synergistic biomass dehydration pretreatment system of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The mechanical-chemical synergistic biomass dehydration pretreatment method and system proposed in this invention are described below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the mechanical-chemical synergistic biomass dehydration pretreatment method of the present invention includes the following steps: (1) The biomass was crushed to obtain biomass pellets, and their initial moisture content was tested; (2) Modified biomass is obtained by spraying a composite dehydrating agent onto the biomass pellets; (3) The modified biomass is subjected to a first-stage low-pressure pressing and a second-stage high-pressure pressing in sequence; (4) Adjust the pH value of the wastewater obtained by pressure filtration.

[0022] Step (1) is the biomass crushing process, which involves crushing the biomass to obtain biomass pellets. In some embodiments, the particle size of the biomass pellets is 3-5 cm. Crushing the biomass into small particles helps with subsequent chemical modification and mechanical pressing processes. The moisture content of the biomass pellets is tested, which is the initial moisture content of the biomass, to facilitate subsequent evaluation of the processing results.

[0023] Step (2) is a chemical modification process. The biomass pellets are chemically modified using a composite dehydrating agent. Specifically, the composite dehydrating agent is sprayed into the biomass pellets to carry out the modification treatment and obtain the modified biomass.

[0024] In some embodiments, the composite dehydrating agent includes citric acid and diatomaceous earth, wherein the amount of citric acid added is 0.3% to 0.8% of the mass of the biomass dry substrate, and the amount of diatomaceous earth added is 1% to 3% of the mass of the biomass dry substrate. It is understood that the amount of citric acid added can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% of the mass of the biomass dry substrate, or any combination of two values, and the amount of diatomaceous earth added can be 1%, 2%, 3% of the mass of the biomass dry substrate, or any combination of two values.

[0025] Citric acid can break the hydrogen bonds between cellulose and hemicellulose, releasing bound water. Diatomaceous earth can adsorb free water and form a porous structure, which helps with subsequent mechanical drainage. Citric acid and diatomaceous earth work together to modify biomass, which can increase the efficiency of biomass cell wall rupture by more than 40%.

[0026] In some embodiments, the time for spraying the composite dehydrating agent onto the biomass pellets in step (2) for modification treatment is 15 to 30 minutes. It is understood that the modification treatment time can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, or any value within the range of any two values.

[0027] Step (3) is the mechanical pressing process, in which the modified biomass is subjected to a first-stage low-pressure pressing and a second-stage high-pressure pressing to fully remove the moisture from the biomass.

[0028] In some embodiments, the pressure of the primary low-pressure press is 1~3MPa and the temperature is room temperature. It can be understood that the pressure of the primary low-pressure press can be 1MPa, 2MPa, 3MPa or any value within the range of two values.

[0029] In some embodiments, a primary low-pressure system utilizes a twin-screw extrusion to crush the fiber structure, and the pressure is adjustable to accommodate different materials.

[0030] In some embodiments, the pressure of the secondary high-pressure press is 8~12MPa and the temperature is 45~50℃. It can be understood that the pressure of the secondary high-pressure press can be 8MPa, 9MPa, 10MPa, 11MPa, 12MPa or any two of these values, and the temperature can be 45℃, 48℃, 50℃ or any two of these values.

[0031] In some embodiments, secondary high-pressure pressing utilizes hydraulic plunger pressing to further reduce viscosity, and the gap between the pressing rollers is automatically adjusted based on feedback from pressure sensors during the pressing process (control accuracy ±0.1mm).

[0032] After primary and secondary pressing, the moisture content of the biomass was tested to analyze the moisture content and removal efficiency.

[0033] Step (4) is the treatment process of the wastewater obtained by pressure filtration. By spraying 0.5% NaHCO3 solution, the residual acidity is neutralized and the pH value of the wastewater is reduced to 6.5~7.5. The neutralized wastewater can be recycled for the preparation of dehydrating agent.

[0034] Mechanical-chemical synergistic biomass dehydration pretreatment system, such as Figure 2 As shown, the system includes a crushing device, a chemical modification device, a mechanical pressing device, and a neutralization and adjustment device arranged sequentially upstream and downstream. The crushing device breaks down the biomass to a size of 3-5 cm. The crushed biomass then reacts with a compound dehydrating agent in the chemical modification device. The mechanical pressing device includes a primary low-pressure pressing device and a secondary high-pressure pressing device. The neutralization and adjustment device is used to adjust the pH value of the filtered wastewater.

[0035] The present invention will now be described in detail with reference to specific embodiments.

[0036] Example 1 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0037] Spray a mixture of 0.5% citric acid and 2% diatomaceous earth onto the biomass pellets and react for 15 minutes.

[0038] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 2 MPa. After primary pressing, the moisture content of the output was 45%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 45°C and a pressure of 10 MPa. After secondary pressing, the moisture content of the output was 28%.

[0039] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0040] Example 2 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0041] Spray a mixture of 0.5% citric acid and 2% diatomaceous earth onto the biomass pellets and react for 15 minutes.

[0042] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 2 MPa. After primary pressing, the moisture content of the output was 45%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 45°C and a pressure of 12 MPa. After secondary pressing, the moisture content of the output was 25%.

[0043] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0044] Example 3 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0045] Spray a mixture of 0.8% citric acid and 2% diatomaceous earth onto the biomass pellets and react for 15 minutes.

[0046] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 2 MPa. After primary pressing, the moisture content of the output was 45%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 45°C and a pressure of 10 MPa. After secondary pressing, the moisture content of the output was 24%.

[0047] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0048] Example 4 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0049] Spray a mixture of 0.5% citric acid and 2% diatomaceous earth onto the biomass pellets and react for 15 minutes.

[0050] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 2 MPa. After primary pressing, the moisture content of the output was 45%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 50°C and a pressure of 12 MPa. After secondary pressing, the moisture content of the output was 20%.

[0051] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0052] Example 5 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0053] Spray a mixture of 0.5% citric acid and 2% diatomaceous earth onto the biomass pellets and react for 15 minutes.

[0054] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 3 MPa. After primary pressing, the moisture content of the output was 40%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 45°C and a pressure of 10 MPa. After secondary pressing, the moisture content of the output was 26%.

[0055] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0056] Comparative Example 1 Corn stalks were crushed to 3-5 cm using a crushing device to obtain biomass pellets. The moisture content of the biomass pellets was tested and found to be 65%.

[0057] At room temperature, a twin-screw extruder was used for primary pressing at a pressure of 2 MPa. After primary pressing, the moisture content of the output material was 50%. After primary pressing, a hydraulic plunger device was used for secondary pressing at a temperature of 45°C and a pressure of 10 MPa. After secondary pressing, the moisture content of the output material was 40%.

[0058] For the wastewater obtained during the biomass dehydration process, the residual acidity is neutralized by spraying 0.5% NaHCO3 solution, bringing the pH value of the wastewater to 7. The neutralized wastewater can then be recycled for the preparation of dehydrating agents.

[0059] As can be seen from Examples 1-5 and Comparative Example 1, the final output moisture content of Examples 1-5 is significantly lower than that of Comparative Example 1. This shows that the biomass dehydration treatment using mechanical-chemical synergy in this application significantly reduces the moisture content of the biomass.

[0060] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0061] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0062] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A mechanical-chemical synergistic biomass dehydration pretreatment method, characterized in that, Includes the following steps: (1) The biomass was crushed to obtain biomass pellets, and their initial moisture content was tested; (2) Modified biomass is obtained by spraying a composite dehydrating agent onto the biomass pellets; (3) The modified biomass is subjected to a first-stage low-pressure pressing treatment and a second-stage high-pressure pressing treatment in sequence; (4) Adjust the pH value of the wastewater obtained by pressure filtration.

2. The preprocessing method as described in claim 1, characterized in that, The biomass pellets have a particle size of 3-5 cm.

3. The preprocessing method as described in claim 1, characterized in that, The composite dehydrating agent includes citric acid and diatomaceous earth.

4. The preprocessing method as described in claim 3, characterized in that, The amount of citric acid added is 0.3% to 0.8% of the mass of the biomass dry substrate.

5. The preprocessing method as described in claim 3, characterized in that, The amount of diatomaceous earth added is 1% to 3% of the mass of the biomass dry substrate.

6. The preprocessing method as described in claim 1, characterized in that, In step (2), the time for spraying the composite dehydrating agent onto the biomass pellets for modification is 15-30 minutes.

7. The preprocessing method as described in claim 1, characterized in that, The pressure of the first-stage low-pressure pressing is 1~3MPa, and the temperature is room temperature.

8. The preprocessing method as described in claim 1, characterized in that, The pressure of the secondary high-pressure press is 8~12MPa, and the temperature is 45~50℃.

9. The preprocessing method as described in claim 1, characterized in that, In step (4), the pH value of the wastewater obtained by pressure filtration is adjusted to 6.5~7.

5.

10. A mechanochemical synergistic biomass dehydration pretreatment system, characterized in that, The preprocessing method applicable to any one of claims 1 to 9 includes: A crushing device, the crushing device being used to crush biomass; A chemical modification device is located downstream of the crushing device, in which the crushed biomass reacts with a composite dehydrating agent. The mechanical pressing device is located downstream of the chemical modification device and includes a primary low-pressure pressing device and a secondary high-pressure pressing device. A neutralization and adjustment device is located downstream of the mechanical pressing device and is used to adjust the pH value of the filtered wastewater.

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