Process for recycling and utilizing high-value resources of waterweeds

Abstract

The application discloses a process for recycling and utilizing waterweeds as high-value resources, which comprises four processes of deep dehydration of waterweeds, pyrolysis and gasification, purification and collection of products and upgrading of products. The detailed process is as follows: the salvaged waterweeds are placed for 24-48 hours, then are cut into pieces, are subjected to deep dehydration by using a dehydration agent, and the dehydration agent is separated and recovered; the obtained solid product is continuously sent into an oxygen-free or low-oxygen rotary kiln for pyrolysis and gasification; the obtained gas is subjected to condensation separation, purification and drying to obtain synthetic gas and bio-oil respectively, and the obtained solid is collected to obtain biochar; and the obtained products are subjected to upgrading treatment according to actual requirements, so that the waterweeds are utilized as high-value resources, and secondary pollution is avoided.

Description

Technical Field

[0001] This invention belongs to the fields of ecological water conservancy and renewable energy, and specifically relates to a process for the high-value recycling and utilization of aquatic plants. This process for treating aquatic plants (water hyacinth, water peanut, water lettuce, etc.) in rivers and lakes is applicable to the high-value utilization of biomass with different moisture contents and uneven raw materials. Background Technology

[0002] With the expansion of urbanization and rapid economic development, river and lake pollution has become increasingly serious. Large amounts of untreated or ineffectively treated biological wastewater and industrial and agricultural wastewater are discharged into rivers, lakes, and oceans, exacerbating eutrophication, causing rampant aquatic plant growth, disrupting the ecological balance of water bodies, and leading to severe ecological and environmental problems. Faced with this increasingly prominent environmental problem, physically removing floating aquatic plants from the water surface is the main solution. However, how to treat and dispose of the removed aquatic plants is a crucial issue facing river and lake management.

[0003] Every spring, summer, and autumn, the daily amount of aquatic plants harvested is enormous, reaching millions of tons. These harvested plants are often dumped in landfills, ditches, or low-lying areas near waterways. Prolonged storage leads to rotting and unpleasant odors, and rainwater runoff can cause secondary pollution. While aquatic plants are an important component of biomass, their sheer quantity signifies a vast biomass resource. However, due to their high water content, high organic matter content, easy decay, and presence of heavy metals, the challenge lies in how to fully recycle and utilize these plants while avoiding secondary pollution, turning waste into treasure.

[0004] In particular, due to the high water content of aquatic plants, dehydration must be considered regardless of the treatment method used. However, since most of the water in aquatic plants is bound to organic matter, dehydration is difficult, and dehydration technology has certain problems, thus limiting the means of subsequent resource utilization. Moreover, there is currently a lack of large-scale process flow for the treatment and disposal of aquatic plants. Therefore, this patent proposes a method to achieve reasonable and efficient resource utilization of aquatic plants, avoid secondary pollution, and realize the full utilization of resources. Summary of the Invention

[0005] Technical Problem Solved: This application mainly proposes a process for the high-value resource recycling of aquatic plants, addressing the technical problems in existing technologies such as the large volume of aquatic plants harvested, high water content, difficulty in dehydration and disposal, and low resource utilization. The disclosed process includes four steps: deep dehydration of aquatic plants, gasification pyrolysis, product purification and collection, and product upgrading. The harvested aquatic plants are left to stand for 24-48 hours, then chopped and deeply dehydrated using a dehydrating agent, which is then separated and recovered. The resulting solid product is continuously gasified and pyrolyzed in an oxygen-free or low-oxygen rotary kiln. The obtained gas is condensed, separated, purified, and dried to obtain syngas and bio-oil, respectively, while the obtained solid is collected to obtain biochar. Based on actual needs, the obtained products are upgraded, achieving high-value resource utilization of aquatic plants and avoiding secondary pollution.

[0006] Technical Solution: A process for the high-value resource recycling of aquatic plants, comprising four steps: deep dehydration of aquatic plants, pyrolysis and gasification, product purification and collection, and product upgrading. The harvested aquatic plants are left to stand for 24-48 hours, then chopped and deeply dehydrated using a dehydrating agent, which is then separated and recovered. The resulting solid product is continuously gasified and pyrolyzed in an oxygen-free or low-oxygen rotary kiln. The obtained gas is condensed, separated, purified, and dried to obtain syngas and bio-oil, respectively, while the obtained solid is collected to obtain biochar. Based on actual needs, the obtained products are upgraded, achieving high-value resource utilization of aquatic plants and avoiding secondary pollution. Specifically, the process includes the following steps:

[0007] The first step involves pre-treating the harvested aquatic plants by letting them sit naturally for 24-48 hours until the water content drops to 70-85%. Then, the plants are chopped into 1-5cm pieces. The prepared dehydrating agent is then mixed with the pre-treated aquatic plants in a container with a pressure of 0.1-0.8MPa at a speed of 100-500 r / min for 40-60 minutes. When the water content of the aquatic plants drops to 5-15%, the mixing is stopped, the pressure is increased to normal pressure, and more than 80% of the dehydrating agent is recycled. The liquid and solid are then separated to obtain solid, deeply dehydrated aquatic plants for the second step.

[0008] Step 2: Introduce N2 into the closed rotary kiln to expel more than 95% of the air in the rotary kiln, achieving an oxygen-free or low-oxygen state. Set the reaction temperature to 300~600℃ according to the product requirements. After the reaction temperature is reached, the solid-state deep dehydrated aquatic plants are fed into the rotary kiln through a screw feeder for pyrolysis and gasification. The feed rate is controlled by the screw feeder. The pyrolysis and gasification time of the aquatic plants is 10~30 minutes, which is used for the third step.

[0009] Step 3: The pyrolysis gas produced by pyrolysis gasification is condensed, separated, purified and dried to obtain syngas and bio-oil respectively. The solid is collected to obtain biochar for use in step 4.

[0010] Step 4: Obtain the syngas, bio-oil, and biochar products for direct use or for upgrading according to actual application needs; the syngas is used as preheating gas in a rotary kiln, or is connected to the residential gas pipeline network after deep purification, or is further cracked and reformed to obtain higher quality chemical products; the bio-oil is further upgraded by adding catalysts to produce biodiesel and ethanol; the biochar is used as a soil conditioner, as an adsorbent to adsorb heavy metal pollutants, or as fuel, depending on its properties, and can be further upgraded to partially or completely replace commercial activated carbon;

[0011] Step 5: The biochar of aquatic plants is directly applied to the materials for protecting river and lake banks. It filters, adsorbs, and purifies heavy metal pollutants in rainwater and industrial and agricultural wastewater. At the same time, due to its water absorption and rich nitrogen and phosphorus content, it helps the plants on the banks to grow, which is conducive to the realization of ecological banks.

[0012] As a preferred technical solution of the present invention: the dehydrating agent in the first step is formed by fully mixing 80-95% of the active component and 5-15% of the auxiliary component under a pressure of 0.1-0.8 MPa.

[0013] As a preferred technical solution of the present invention: the active component is L-DME, and it can be separated and recovered after dehydration.

[0014] As a preferred embodiment of the present invention, the auxiliary component is an enzyme.

[0015] As a preferred embodiment of the present invention, the enzyme is a lysin.

[0016] As a preferred embodiment of the present invention, the lysin is cellulase and / or pectinase.

[0017] As a preferred technical solution of the present invention: the pyrolysis gasification reactor mentioned in the second step is a closed rotary kiln. The rotary kiln adapts to the non-uniformity of the aquatic plants, avoids jamming and clogging, realizes uniform pyrolysis gasification of the aquatic plants, and the screw feeder adjusts the feeding rate of the aquatic plants in a timely manner according to the operation of the reactor, and also plays a sealing role.

[0018] As a preferred technical solution of the present invention: in the third step, the synthesis gas, bio-oil and biochar are adjusted according to the reaction temperature, time in the reactor and oxygen content to obtain products with different mass ratios, and then condensed, separated, purified and dried.

[0019] Beneficial Effects: Compared with existing technologies, the above-mentioned technical solutions for the high-value resource recycling of aquatic plants described in this application have the following technical effects: 1. The deep dehydration described in this invention can reduce the water content of aquatic plants to 15%~5% under micro-pressure conditions through the active ingredients and additives of the dehydrating agent. On the one hand, this method is more operable and can achieve large-scale dehydration compared with mechanical dehydration, drying dehydration and other methods; on the other hand, the instruments used for dehydration are simple, and the dehydrating agent can achieve a recycling rate of more than 80%, resulting in low cost; on the other hand, this method can achieve a deep reduction in water content with low energy consumption and a high dehydration rate.

[0020] 2. The pyrolysis gasification reactor described in this invention is a closed rotary kiln, which can accommodate the unevenness of aquatic plants, prevent accumulation, clumping and blockage, and is suitable for the simultaneous pyrolysis reaction of different types of aquatic plants.

[0021] 3. The high-value resource recycling process for aquatic plants described in this invention achieves deep dehydration of the aquatic plants, providing more possibilities for their subsequent resource utilization. Furthermore, by controlling the reaction temperature, reaction time, and oxygen content of the rotary kiln, different gaseous, liquid, and solid products can be obtained, and further quality improvement opens up possibilities for their wider application. Moreover, considering the unique growth characteristics of aquatic plants, the plant can be built near river and lake banks, and the generated biochar can be directly used for embankment protection, contributing to the realization of green and ecological embankment protection.

[0022] Attached image description: Figure 1 This is a process flow diagram for the high-value resource recovery and utilization of aquatic plants in this application. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Example 1: A process for high-value resource recycling of aquatic plants. This process includes four steps: deep dehydration of aquatic plants, gasification pyrolysis, product purification and collection, and product upgrading. The harvested aquatic plants are left to stand for 24-48 hours, then chopped and deeply dehydrated using a dehydrating agent, which is then separated and recovered. The resulting solid product is continuously gasified and pyrolyzed in an oxygen-free or low-oxygen rotary kiln. The obtained gas is condensed, separated, purified, and dried to obtain syngas and bio-oil, respectively. The obtained solid is collected to obtain biochar. According to actual needs, the obtained products are upgraded, achieving high-value resource utilization of aquatic plants and avoiding secondary pollution. The specific steps are as follows:

[0025] Step 1: Select water hyacinth as raw material. Place the harvested water hyacinth under natural conditions for 36 hours until its moisture content drops to 70-85%. Chop it into 1-5cm pieces. Use a dehydrating agent made of 95% active ingredients and 5% cellulase. Mix the dehydrating agent with the pretreated water hyacinth in a 0.6MPa reactor at 200r / min for 40min. Then separate the liquid and solid. The solid product obtained at this time is the deeply dehydrated aquatic plant with a moisture content of 8%. N2 is passed into the rotary kiln to remove all the air, and the reaction temperature is set to 400℃. Once the reaction temperature is reached, a screw feeder is set to ensure that the aquatic plants are fed continuously at a uniform speed. The plants are kept in the furnace for 30 minutes. The pyrolysis gas produced by the pyrolysis gasification is condensed, separated, purified, and dried to obtain syngas and bio-oil. The solid is collected to obtain biochar. The mass ratio of gas, liquid, and solid is 2:1:2. One path of the syngas is used as preheating gas for heating the rotary kiln, and the other path is used to produce hydrogen through cracking and reforming. The bio-oil is used as fuel to provide heat for heating the rotary kiln, and the biochar is used as a dam protection material.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for the high-value resource recycling and utilization of aquatic plants, characterized in that, This process comprises four steps: deep dehydration of aquatic plants, pyrolysis and gasification, product purification and collection, and product upgrading. The harvested aquatic plants are left to stand for 24-48 hours, then chopped and deeply dehydrated using a dehydrating agent, which is then separated and recovered. The resulting solid product is continuously gasified and pyrolyzed in an oxygen-free or low-oxygen rotary kiln. The resulting gas is condensed, separated, purified, and dried to obtain syngas and bio-oil, respectively, while the solid product is collected to obtain biochar. Based on actual needs, the obtained products are upgraded, achieving high-value resource utilization of aquatic plants and avoiding secondary pollution. The specific steps include: The first step involves pre-treating the harvested aquatic plants by letting them sit naturally for 24-48 hours until the water content drops to 70-85%. Then, the plants are chopped into 1-5cm pieces. The prepared dehydrating agent is then mixed with the pre-treated aquatic plants in a container with a pressure of 0.1-0.8MPa at a speed of 100-500r / min for 40-60 minutes. When the water content of the aquatic plants drops to 5-15%, the mixing is stopped, the pressure is increased to normal pressure, and more than 80% of the dehydrating agent is recycled. The liquid and solid are then separated to obtain solid, deeply dehydrated aquatic plants for the second step. Step 2: Introduce N2 into the closed rotary kiln to expel more than 95% of the air in the rotary kiln, achieving an oxygen-free or low-oxygen state. Set the reaction temperature to 300~600℃ according to the product requirements. After the reaction temperature is reached, the solid-state deep dehydrated aquatic plants are fed into the rotary kiln through a screw feeder for pyrolysis and gasification. The feed rate is controlled by the screw feeder. The pyrolysis and gasification time of the aquatic plants is 10~30 minutes, which is used for the third step. Step 3: The pyrolysis gas produced by pyrolysis gasification is condensed, separated, purified and dried to obtain syngas and bio-oil respectively. The solid is collected to obtain biochar for use in step 4. Step 4: Obtain the syngas, bio-oil, and biochar products for direct use or for upgrading according to actual application needs; the syngas is used as preheating gas in a rotary kiln, or is connected to the residential gas pipeline network after deep purification, or is further cracked and reformed to obtain higher quality chemical products; the bio-oil is further upgraded by adding catalysts to produce biodiesel and ethanol; the biochar is used as a soil conditioner, as an adsorbent to adsorb heavy metal pollutants, or as fuel, depending on its properties, and can be further upgraded to partially or completely replace commercial activated carbon; Step 5: The biochar of aquatic plants is directly applied to the materials for protecting river and lake banks. It filters, adsorbs, and purifies heavy metal pollutants in rainwater and industrial and agricultural wastewater. At the same time, due to its water absorption and rich nitrogen and phosphorus content, it helps the plants on the banks to grow, which is conducive to the realization of ecological banks.

2. The process for high-value resource recycling of aquatic plants according to claim 1, characterized in that: In the first step, the dehydrating agent is formed by fully mixing 80-95% of the active component and 5-15% of the auxiliary component under a pressure of 0.1-0.8 MPa.

3. The process for high-value resource recycling of aquatic plants according to claim 2, characterized in that: The active component is L-DME, and it can be separated and recovered after dehydration.

4. The process for high-value resource recycling of aquatic plants according to claim 2, characterized in that: The auxiliary component is an enzyme.

5. The process for high-value resource recycling of aquatic plants according to claim 4, characterized in that: The enzyme in question is a lysin.

6. The process for high-value resource recycling of aquatic plants according to claim 5, characterized in that: The lysin is cellulase and / or pectinase.

7. The process for high-value resource recycling of aquatic plants according to claim 1, characterized in that: The pyrolysis gasification reactor mentioned in the second step is a closed rotary kiln. The rotary kiln adapts to the non-uniformity of the aquatic plants, avoids jamming and clogging, and achieves uniform pyrolysis gasification of the aquatic plants. The screw feeder adjusts the feeding rate of the aquatic plants in a timely manner according to the operation of the reactor, and also plays a sealing role.

8. The process for high-value resource recycling of aquatic plants according to claim 1, characterized in that: In the third step, the synthesis gas, bio-oil, and biochar are mixed according to the required adjustment of reaction temperature, time in the reactor, and oxygen content to obtain products with different mass ratios, followed by condensation, separation, purification, and drying.

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