A system and method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent

Abstract

The present invention relates to a system and method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent, and relates to the technical field of solid waste treatment. It includes a biomass gradient anaerobic fermenter, a solid-liquid separation device, a drying reactor, a gasification reactor, a condensation tower and a syngas purifier; the biomass gradient anaerobic fermenter is connected to the drying reactor through the solid-liquid separation device to transport the biogas residue to the drying reactor, and the drying reactor and the biomass gradient anaerobic fermenter are connected to the gasification reactor to input the biogas and the dried biogas residue from the drying reactor into the gasification reactor for reaction; the gasification reactor is connected to the condensation tower to transport the reaction products to the condensation tower, and the condensation tower is connected to the syngas purifier, and the gas cooled by the condensation tower is purified by the syngas purifier to obtain hydrogen-rich syngas. The present invention uses biogas as a composite gasifying agent to gasify biogas residue, thereby significantly improving the hydrogen production rate.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste treatment, and specifically to a system and method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent. Background Art

[0002] With the continuous growth of global energy demand and the improvement of environmental protection awareness, the development and utilization of biomass resources have gradually become an important way to achieve circular agriculture and low-carbon economy. Biogas residue, as a by-product in the fermentation process, contains a certain amount of organic substances and nutrient elements, and is therefore regarded as a potential biomass resource with a large volume in China. However, the treatment of biogas residue in China currently has the following problems: (1) High moisture content and complex composition: The complex composition structure poses challenges to the direct utilization of biogas residue. (2) High environmental pollution risk: Without treatment or improper treatment, biogas residue will become a source of pathogens and nutrients, polluting water bodies and soil. (3) Low resource utilization rate: Most biogas residues are still abandoned without effective resource utilization.

[0003] Therefore, in order to avoid the problems existing in the biogas residue resource utilization process above, so as to make full use of the organic substances in biogas residue and improve the energy utilization efficiency after gasification of biogas residue. Gasification technology is an efficient and safe biomass conversion technology, which can efficiently convert biogas residue into valuable syngas products. However, biomass gasification technology is affected by various factors, and the type of gasifying agent has a crucial impact on the chemical reactions in the biomass gasification process.

[0004] Commonly used gasifying agents mainly include air, oxygen, carbon dioxide, and mixed gasifying agents, etc. Different gasifying agents affect the composition of key combustible gas components (such as CH4, H2, CO, etc.) in the syngas due to the differences in the contents of functional elements such as C and H, and then affect the calorific value of the product gas, etc. Air is used as the most widely used gasifying agent due to its low cost. However, the high nitrogen content in air results in a low calorific value of the syngas, and at the same time, the high oxygen content makes it difficult to control the gasification degree. Oxygen gasification can reduce the dilution of nitrogen to a certain extent and increase the calorific value of the syngas, but the gas products are difficult to have the characteristics of hydrogen enrichment. Carbon dioxide gasification requires adding steps for capturing and purifying carbon dioxide, increasing the cost. Therefore, the currently developed biogas residue gasification technologies cannot more efficiently gasify biogas residue into high-quality hydrogen-rich and carbon monoxide-rich syngas. Especially for the current urgent demand for clean fuels such as green methanol and aviation kerosene, it is required that the biomass gasification syngas must have high hydrogen enrichment characteristics. Therefore, it is crucial to develop a low-cost and easily available system and method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent. Summary of the Invention

[0005] To solve at least one technical problem in the background art, the present invention provides a system and method for gasifying biogas residues to produce hydrogen-rich syngas using biogas as a composite gasifying agent. By using biogas as a composite gasifying agent to gasify biogas residues, a significant increase in hydrogen production rate is achieved.

[0006] To achieve the above object, the present invention provides a system for gasifying biogas residues to produce hydrogen-rich syngas using biogas as a composite gasifying agent, which is characterized by comprising: a biomass gradient anaerobic fermenter, a solid-liquid separation device, a drying reactor, a gasification reactor, a condensation tower, and a syngas purifier;

[0007] The biomass gradient anaerobic fermenter is connected to the drying reactor through the solid-liquid separation device, and the separated biogas residues are transported to the drying reactor. The drying reactor and the biomass gradient anaerobic fermenter are respectively connected to the gasification reactor, and the biogas generated by the biomass gradient anaerobic fermenter and the biogas residues dried by the drying reactor are jointly input into the gasification reactor for reaction; the gasification reactor is connected to the condensation tower for transporting the reaction products to the condensation tower, and the gas cooled by the condensation tower is purified by the syngas purifier to obtain hydrogen-rich syngas.

[0008] Further, it also includes a biogas collector and a biogas storage tank. The biomass gradient anaerobic fermenter is sequentially connected to the gasification reactor through the biogas collector and the biogas storage tank.

[0009] Further, it also includes a liquid waste collection device and a water resource treatment device. The solid-liquid separation device is sequentially connected to the liquid waste collection device and the water resource treatment device to collect and purify the separated biogas slurry.

[0010] A method for gasifying biogas residues to produce hydrogen-rich syngas using biogas as a composite gasifying agent includes the following steps:

[0011] Step S10, producing biogas through the biomass gradient anaerobic fermenter and transporting the generated biogas to the gasification reactor;

[0012] Step S20, transporting the biogas residues separated by the solid-liquid separation device to the gasification reactor after drying treatment through the drying reactor;

[0013] Step S30, transporting the reaction products obtained from the gasification reactor to the condensation tower, and purifying the gas cooled by the condensation tower through the syngas purifier to obtain hydrogen-rich syngas.

[0014] Further, in step S10, the biogas produced by the biomass gradient anaerobic fermenter is collected by the biogas collector and stored in the biogas storage tank, and the proportion of biogas and nitrogen in the gasification reactor is controlled.

[0015] Furthermore, it further includes step S40, and the biogas slurry separated by the solid-liquid separation device is collected and purified through the liquid waste collection device and the water resource treatment device.

[0016] The beneficial effects of the present invention are as follows:

[0017] Aiming at the typical biomass raw material of biogas residue that is difficult to be resourcefully utilized, the present invention provides a system and method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent to achieve the efficient and clean utilization of biogas residue. By using biogas as a composite gasifying agent to gasify biogas residue, the hydrogen production rate is significantly increased. Through the in-situ digestion of fermented biogas residue and further production of hydrogen-rich syngas, the quality of gas products is improved, and the efficient and clean thermochemical conversion of biomass biogas residue is realized, providing new ideas and technical references for the industrial application of biogas residue biomass. Description of the Drawings

[0018] Figure 1 is the process flow chart of the present invention;

[0019] Figure 2 is the schematic diagram of the gas product distribution under different atmosphere conditions of the present invention;

[0020] Figure 3 is the schematic diagram of H2 / CO and hydrogen production rate under different atmosphere conditions of the present invention;

[0021] Figure 4 is the schematic diagram of the cold gas efficiency of biogas residue gasification under different atmosphere conditions of the present invention;

[0022] Figure 5 is the schematic diagram of the three-phase product distribution of biogas residue gasification under different atmosphere conditions of the present invention;

[0023] Figure 6 is the schematic diagram of the consumption of hydrogen production raw materials of the present invention. Detailed Embodiments

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of this application are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so as to implement the embodiments of this application described here. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] In this application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation.

[0027] Moreover, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0028] In addition, the terms "install", "set", "be provided with", "connect", "be connected", "be sleeved" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there can also be internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0029] To achieve the above object, as Figure 1 shown, the present invention provides a system for gasifying biogas residue with biogas as a composite gasifying agent to prepare hydrogen-rich syngas, which is characterized in that it includes: a biomass gradient anaerobic fermenter, a solid-liquid separation device, a drying reactor, a gasification reactor, a condensation tower and a syngas purifier;

[0030] The biomass gradient anaerobic fermenter is connected to the drying reactor through a solid-liquid separation device, and the separated biogas residue is transported to the drying reactor. The drying reactor and the biomass gradient anaerobic fermenter are respectively connected to the gasification reactor, and the biogas generated by the biomass gradient anaerobic fermenter and the biogas residue dried by the drying reactor are jointly input into the gasification reactor for reaction. The gasification reactor is connected to a condensation tower for transporting the reaction products into the condensation tower. The condensation tower is connected to a syngas purifier, and the gas cooled by the condensation tower is purified by the syngas purifier to obtain hydrogen-rich syngas.

[0031] Further, it also includes a biogas collector and a biogas storage tank. The biomass gradient anaerobic fermenter is sequentially connected to the gasification reactor through the biogas collector and the biogas storage tank.

[0032] Further, it also includes a liquid waste collection device and a water resource treatment device. The solid-liquid separation device is sequentially connected to the liquid waste collection device and the water resource treatment device to collect and purify the separated biogas slurry.

[0033] The main components of biogas are CH4, CO2, etc. Among them, CH4, as the hydrogen donor in the methanation reaction during gasification, can enhance the hydrogen production effect of biomass gasification. At the same time, CO2, as a gasifying agent, can promote the Boudouard reaction to a certain extent, significantly increase the CO production, provide a higher reaction temperature, faster reaction rate, larger product range, and higher thermal efficiency at the same molar ratio, and can obtain a higher syngas calorific value. Biogas and biogas residue, as the products of anaerobic fermentation, realize the in-situ utilization of biogas through gasification means, which can not only save the energy consumption and loss during biogas transportation and achieve local consumption, but also strengthen the energy utilization of biogas residue. Therefore, biogas can be selected as an advantageous gasifying agent for realizing the high-value conversion of biogas residue gasification.

[0034] In order to solve the problem of low efficiency in the treatment and energy utilization of biogas residue, the present invention utilizes a part of the biogas from the biogas project to achieve the resource treatment of biogas residue while improving the conversion rate of biomass in the whole system to high-quality hydrogen-rich syngas. Traditional gasification methods, such as pure nitrogen gasification and CO2 gasification, have the defects of low hydrogen production rate and low energy utilization efficiency. Therefore, the present invention provides a system for gasifying biogas residue with biogas as a composite gasifying agent to prepare hydrogen-rich syngas. This system can effectively improve the gasification efficiency of biogas residue and the H2 and CO production rates, and can ensure experimental safety. The present invention has the characteristics of high efficiency, cost saving, environmental friendliness, etc., so it has good market application value.

[0035] The present invention also provides a method for gasifying biogas residue with biogas as a composite gasifying agent to prepare hydrogen-rich syngas, including the following steps:

[0036] Step S10: Produce biogas through a biomass gradient anaerobic fermenter and transport the generated biogas to a gasification reactor.

[0037] Step S20: Transport the biogas residue separated by a solid-liquid separation device to a drying reactor for drying treatment and then to the gasification reactor.

[0038] Step S30: Transport the reaction products obtained from the gasification reactor to a condensation tower. The gas cooled by the condensation tower is purified through a syngas purifier to obtain hydrogen-rich syngas.

[0039] Furthermore, in Step S10, the biogas produced through the biomass gradient anaerobic fermenter is collected by a biogas collector and stored in a biogas storage tank, and the proportion of biogas and nitrogen in the gasification reactor is controlled.

[0040] Furthermore, it also includes Step S40: The biogas slurry separated by the solid-liquid separation device is collected and purified through a liquid waste collection device and a water resource treatment device.

[0041] The present invention has the following advantages:

[0042] Utilize biogas as a composite gasifying agent: The present invention proposes to use biogas as a composite gasifying agent in the gasification process. Compared with traditional gasifying agents such as air, oxygen, or steam, the introduction of biogas not only effectively utilizes resources and reduces waste gas emissions but also significantly increases the hydrogen production rate in the gasification process due to its high methane content. In addition, the use of biogas can reduce the dependence on external gasifying agents and achieve more economical operation. The present invention finds that the hydrogen production rate under biogas gasification is 50.8% higher than that under pure nitrogen gasification and 40.3% higher than that under a CO2 atmosphere. In addition, the H2 / CO ratio of the syngas produced under a biogas atmosphere is 1.55 to 1.96 times that under CO2 gasification.

[0043] Increase the hydrogen production: The gasification of biogas residue is usually limited by a low carbon-hydrogen ratio in the generation of hydrogen. However, the present invention uses the methane content in biogas as an additional hydrogen source, which not only promotes the deep gasification of biogas residue but also enhances the hydrogen production, thereby generating hydrogen-rich syngas and improving the application potential of this technology in hydrogen energy production.

[0044] System Integration and Efficient Gasification Process Design: The biogas gasification system for biogas residue developed in this invention has significant advantages in energy utilization efficiency. The system design fully considers the supply and control of biogas, optimizes the gasification reaction conditions, and ensures the high efficiency and stability of the gasification reaction. Through the efficient reactor structure design and heat exchange technology, the system can achieve self-circulation utilization of energy, improve the overall efficiency, and reduce energy consumption. The results show that the cold gas efficiency under biogas atmosphere is 2.39 to 3.06 times that of CO2 gasification.

[0045] Optimization of Biogas Residue Gasification Products: The biogas gasification system of this invention has a significant impact on the gas components and the distribution of three-phase products in the biogas residue gasification products. The system design can optimize the gas components, increase the yield of useful gases, and improve the distribution characteristics of three-phase products.

[0046] Synergistic Optimization of Gas Purification and Production of Hydrogen-Rich Syngas: This method not only focuses on hydrogen generation during the gasification process but also significantly reduces the content of impurity gases such as carbon dioxide and carbon monoxide through subsequent gas purification technologies, thereby improving the quality of the syngas and making it more suitable for downstream industrial applications such as chemical synthesis and the preparation of green aviation fuel.

[0047] The following specifically describes the significant advantages of the biogas gasification of biogas residue.

[0048] 1. The biogas atmosphere can improve the thermal performance of the product gas, resulting in a significant increase in the content of H2 and CO, and having the ability to improve the gas quality, such as Figure 2 (a), Figure 2 (b) and Figure 3 (a), Figure 3 (b) shown. The proportion of combustible components (such as H2, CO) in the syngas is relatively high, and the fuel value is high. The purity of the syngas is high: there are fewer impurities in the syngas, which improves its application value in subsequent processes, such as fuel cells or chemical synthesis.

[0049] 2. The biogas gasification of biogas residue has significant advantages in energy utilization efficiency. As Figure 4 can be seen, the cold gas efficiency of biogas gasification is significantly higher than that of CO2 gasification, so that more raw material energy is successfully converted into the chemical energy in the syngas instead of being wasted. This indicates that: the energy loss during the reaction process is small, and the heat loss and the loss of unreacted carbon during the gasification process are small. The reaction is more efficient, and the reaction conditions (such as temperature, pressure, and gasifier ratio) are well optimized, promoting the complete gasification and efficient conversion of raw materials.

[0050] 3. The biogas residue gasification products under biogas atmosphere have significant advantages. The yield of biogas gasification gas products is stably between 59% - 61%, compared with the proportion of gas products under CO2 atmosphere, as Figure 5 (a),Figure 5 As shown in (b), the performance of the gas produced under the biogas atmosphere is higher. In addition, in biogas gasification, the tar yield is lower, decreasing from 3% to 1%. The low tar yield means a reduction in the complex organic matter that needs to be processed during the gasification process, which helps improve the operational stability and efficiency of the system. Because CO2 in biogas can promote the partial oxidation reaction of carbon during gasification to generate carbon monoxide, while avoiding the generation of excessive tar. The yield of biochar is between 38% - 40%, fluctuating slightly but remaining stable. This indicates that the biogas gasification process has little impact on the formation of solid carbon, and can provide a stable output of biochar, facilitating further processing and utilization. Because under the biogas atmosphere, the balance between the partial oxidation of carbon and the reforming reaction of methane makes the formation of biochar relatively stable. This characteristic helps to provide a continuous output of solid products, facilitating further utilization of carbon-based materials, such as soil improvement or carbon capture.

[0051] 4. Under the biogas atmosphere condition, to produce the same 1 g of hydrogen, less raw material consumption is required, as shown in Figure 6 . When generating products of the same mass, there is a close relationship between the amount of raw material consumption and the environmental benefits. Less raw material consumption generally means higher resource efficiency. It not only reduces the exploitation and consumption of natural resources but also decreases the environmental impacts associated with raw material acquisition, thus having positive environmental benefits. At the same time, it can reduce the energy consumption required for raw material extraction and fermentation processes, thereby reducing greenhouse gas emissions and the emissions of other pollutants. The reduction in raw material consumption can reduce the environmental impacts throughout the production cycle, including global warming potential, acidification potential, and eutrophication potential, etc. Therefore, reducing the raw material consumption when generating products of the same mass can bring significant environmental benefits, which not only helps protect natural resources and the ecological environment but also conforms to the goals of sustainable development and circular economy. Reducing raw material consumption further reduces the costs in the production stage, improving economic efficiency.

[0052] The above are only the preferred embodiments of the present invention, and do not impose any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A system for gasifying biogas residue to prepare hydrogen-rich syngas using biogas as a composite gasifying agent, characterized in that, Including: A biomass gradient anaerobic fermenter, a solid-liquid separation device, a drying reactor, a gasification reactor, a condensation tower and a syngas purifier; The biomass gradient anaerobic fermenter is connected to the drying reactor through the solid-liquid separation device, and the separated biogas residue is transported to the drying reactor. The drying reactor and the biomass gradient anaerobic fermenter are respectively connected to the gasification reactor, and the biogas generated by the biomass gradient anaerobic fermenter and the biogas residue dried by the drying reactor are jointly input into the gasification reactor for reaction; The gasification reactor is connected to the condensation tower for transporting the reaction product to the condensation tower. The condensation tower is connected to the syngas purifier, and the gas cooled by the condensation tower is purified by the syngas purifier to obtain hydrogen-rich syngas; It also includes a biogas collector and a biogas storage tank. The biomass gradient anaerobic fermenter is sequentially connected to the gasification reactor through the biogas collector and the biogas storage tank; It also includes a liquid waste collection device and a water resource treatment device. The solid-liquid separation device is sequentially connected to the liquid waste collection device and the water resource treatment device to collect and purify the separated biogas slurry.

2. A method for gasifying biogas residue to prepare hydrogen-rich syngas by using biogas as a composite gasifying agent, characterized in that, Including the following steps: Step S10, producing biogas through the biomass gradient anaerobic fermenter and transporting the generated biogas to the gasification reactor; Step S20, drying the biogas residue separated by the solid-liquid separation device through the drying reactor and then transporting it to the gasification reactor; Step S30, transporting the reaction product obtained by the gasification reactor to the condensation tower, and purifying the gas cooled by the condensation tower through the syngas purifier to obtain hydrogen-rich syngas; In step S10, the biogas produced by the biomass gradient anaerobic fermenter is collected by the biogas collector and stored in the biogas storage tank, and the proportion of biogas and nitrogen in the gasification reactor is controlled; It also includes step S40, collecting and purifying the biogas slurry separated by the solid-liquid separation device through the liquid waste collection device and the water resource treatment device.

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