Synthesis gas backflow heat supply carbonization system and carbonization process

Abstract

The carbonization system comprises a carbonization furnace, a combustion chamber and a heat exchanger, synthesis gas discharged by the carbonization furnace has two flow directions, the first flow direction is led to the combustion chamber and converted into hot flue gas to be used as a heat source of the heat exchanger, and the second flow direction is led to the heat exchanger and converted into hot flue gas to be used as a heat source of the heat exchanger. The heat exchanger can adjust the temperature of the synthesis gas entering the heat exchanger, so that the synthesis gas with proper temperature can flow back into the carbonization furnace to be used as a carbonization heat source; the carbonization system realizes multi-stage self heat supply of an energy closed loop; according to the carbonization process, a carbonization system is supplied with heat through synthesis gas backflow, and external raw materials, a first flue gas circulation path, a second flue gas circulation path, a third valve and a fourth valve are matched, so that smooth conversion from hot flue gas heat supply in an initial stage to synthesis gas backflow self-heat supply in a normal working stage is realized; the stability and the continuity of a carbonization process are guaranteed, and the quality and the production efficiency of biomass charcoal are improved.

Description

Technical Field

[0001] This application relates to the technical field of carbonization furnaces, in particular to a syngas reflux heating carbonization system and a carbonization process. Background Art

[0002] As an important means of resource utilization of agricultural and forestry waste, biomass carbonization technology is widely used in the fields of biomass carbon production, activated carbon preparation, and clean energy development. In traditional carbonization systems, biomass raw materials (such as wood chips, straw, etc.) are pyrolyzed at high temperature under anaerobic conditions to produce biomass carbon, and at the same time, syngas containing tar, carbon monoxide, hydrogen, and carbon particles is generated. However, there are significant defects in the treatment and utilization of syngas in the prior art, which are specifically manifested in the following problems: 1. Traditional carbonization furnaces mainly rely on external fuels (such as diesel, natural gas) for continuous heating to maintain the carbonization temperature, while the self-produced syngas, as a high-calorific value energy source, is not effectively recovered and utilized.

[0003] 2. Most existing systems use a single external heat source for heating and lack a closed-loop heat energy regulation mechanism. The carbonization temperature is easily affected by factors such as raw material characteristics and gas supply fluctuations, resulting in problems such as local overheating (excessive pyrolysis of biomass carbon) or low-temperature zones (incomplete pyrolysis), uneven product quality, and low carbonization efficiency.

[0004] In recent years, although some studies have proposed using biomass gasification gas as an alternative fuel, its process requires the configuration of independent gasification equipment, with low system integration, and the gasification gas has complex components (including ash, sulfides, etc.), which is likely to cause equipment corrosion and secondary pollution. In addition, the existing solutions do not solve the safety control problem of the switch between syngas self-heating and external fuel, and there is a risk of explosion caused by oxygen infiltration.

[0005] In view of the above problems, there is an urgent need for a carbonization system that can achieve closed-loop self-heating of syngas, low pollution emissions, and intelligent regulation, which breaks through the dual bottlenecks of energy efficiency and environmental protection performance by recycling the heat energy of syngas to replace traditional fuels. Summary of the Invention

[0006] The purpose of this application is to overcome the deficiencies in the prior art and provide a syngas reflux heating carbonization system and a carbonization process.

[0007] The present application provides a syngas reflux heating carbonization system, including: a carbonization furnace for carbonizing biomass raw materials to generate syngas and biomass charcoal; a combustion chamber disposed downstream of the carbonization furnace, capable of treating syngas through low-nitrogen combustion to generate hot flue gas; a heat exchanger disposed downstream of the combustion chamber, and the hot flue gas discharged from the combustion chamber can be introduced into the heat exchanger as the heat source of the heat exchanger; the syngas discharged from the carbonization furnace has two flow directions, the first direction leads to the combustion chamber, and after being converted into hot flue gas, it is used as the heat source of the heat exchanger, and the second direction leads to the heat exchanger, and the heat exchanger can adjust the temperature of the syngas entering it; the heat exchanger is connected to the carbonization furnace, and the syngas with a suitable temperature can enter the carbonization furnace through the heat exchanger, serving as the heat source of the carbonization furnace and contacting the biomass raw materials in the carbonization furnace, thereby promoting the carbonization of the biomass raw materials.

[0008] Further, the syngas reflux heating carbonization system further includes: a first induced draft fan for sucking syngas into the first syngas flow passage; a second induced draft fan for sucking syngas into the second syngas flow passage; a flow meter for monitoring the syngas flow rate in the second syngas flow passage; as carbonization progresses, syngas is continuously generated. To control the air pressure in the carbonization furnace, it is necessary to regulate the syngas flow rate entering the second syngas flow passage; by increasing the air draft volume of the first induced draft fan, the syngas flow rate entering the first syngas flow passage increases, and the syngas flow rate entering the second syngas flow passage and flowing to the heat exchanger can be reduced.

[0009] Further, the syngas reflux heating carbonization system further includes a third syngas flow passage. After the amount of syngas discharged from the carbonization furnace is greater than the required amount to maintain the carbonization air pressure, the excess syngas can be discharged through the third syngas flow passage; the discharged syngas can be used for power generation or heating, thereby realizing multi-level utilization of energy.

[0010] Further, the second syngas flow passage downstream of the second induced draft fan bifurcates to form a third syngas flow passage; a first valve is provided on the third syngas flow passage; when the syngas generation amount is insufficient, the first valve is closed; when the syngas generation amount is surplus, the first valve is opened; by increasing the opening degree of the first valve, the discharged syngas flow rate increases, and the syngas flow rate flowing to the heat exchanger can be reduced, so as to control the syngas reflux amount and the air pressure in the carbonization furnace.

[0011] Further, a second valve is provided on the second syngas flow passage; according to the detection result of the flow meter, by increasing or decreasing the opening degree of the second valve, the syngas flow rate flowing to the heat exchanger can be quickly regulated.

[0012] Furthermore, the syngas reflux heat supply carbonization system further includes: a waste heat utilization device, which is connected to the heat exchanger. The hot flue gas serving as the heat source of the heat exchanger still has a certain amount of heat energy after use, enabling the flue gas with heat energy to enter the waste heat utilization device, thereby realizing the cascade utilization of energy; and / or a chimney, which is connected to the heat exchanger and is used for discharging flue gas.

[0013] Furthermore, the combustion chamber includes an oxygen-deficient combustion section and a complete combustion section. The oxygen-deficient combustion section is equipped with a burner and a primary air blower, and the complete combustion section is equipped with a secondary air blower; the syngas first enters the oxygen-deficient combustion section for oxygen-deficient combustion, and then enters the complete combustion section to achieve complete combustion through oxygen supplementation; a cold air inlet is provided on the complete combustion section, and the cold air inlet is close to the outlet of the combustion chamber; by allowing normal-temperature or low-temperature gas to enter the complete combustion section through the cold air inlet, the hot flue gas about to be discharged from the complete combustion section can be cooled down, so that the hot flue gas has the temperature required by the heat exchanger.

[0014] Furthermore, the carbonization furnace is a spiral carbonization furnace, and a spiral shaft is provided inside the carbonization furnace. After the biomass raw material is put into the carbonization furnace, it can be fed forward under the drive of the rotation of the spiral shaft; the rotation of the spiral shaft can also promote the mixing of the biomass raw material and the syngas, thereby improving the pyrolysis efficiency.

[0015] Furthermore, there are two flue gas circulation paths at the outlet of the combustion chamber. The first flue gas circulation path is connected to the carbonization furnace, and the second flue gas circulation path is connected to the heat exchanger; a third valve is provided on the first flue gas circulation path; a fourth valve is provided on the second flue gas circulation path; at the initial stage, the third valve is opened and the fourth valve is closed. The combustion chamber generates hot flue gas by burning raw materials such as natural gas and diesel. The hot flue gas can enter the carbonization furnace through the first flue gas circulation path and directly contact the biomass raw material, promoting the carbonization of the biomass raw material and generating syngas; the syngas returns to the carbonization furnace after passing through the heat exchanger, so that the high-temperature gas for carbonization changes from hot flue gas to a mixture of hot flue gas and syngas; as the carbonization progresses, syngas is continuously generated, and the proportion of syngas in the mixture continuously increases; after the reflux flow rate of the syngas meets the required amount for maintaining the carbonization pressure, the third valve is closed, and the high-temperature gas for carbonization changes from the mixture to syngas.

[0016] The present application also provides a carbonization process, which is realized by using the above-mentioned syngas reflux heating carbonization system, and includes the following steps: In the initial stage, the combustion chamber generates hot flue gas by burning raw materials such as natural gas and diesel. The hot flue gas enters the carbonization furnace and directly contacts with the biomass raw materials, promoting the carbonization of the biomass raw materials and generating syngas; In the transition stage, the reflux flow rate of the syngas is less than the required amount to maintain the carbonization pressure. The syngas refluxes into the carbonization furnace and is used as the heat source of the carbonization furnace together with the hot flue gas; In the normal working stage, the reflux flow rate of the syngas meets the required amount to maintain the carbonization pressure, and the hot flue gas no longer enters the carbonization furnace. Part of the syngas generated by the carbonization furnace enters the combustion chamber, is converted into hot flue gas and used as the heat source of the heat exchanger. Another part of the syngas is temperature-adjusted by the heat exchanger and then refluxes into the carbonization furnace to be used as the heat source of the carbonization furnace.

[0017] The present application provides a syngas reflux heating carbonization system, including a carbonization furnace, a combustion chamber and a heat exchanger. The syngas discharged from the carbonization furnace has two flow directions. The first direction leads to the combustion chamber, is converted into hot flue gas and used as the heat source of the heat exchanger. The second direction leads to the heat exchanger. The heat exchanger can adjust the temperature of the syngas entering it so that the syngas with a suitable temperature refluxes into the carbonization furnace and is used as the heat source of the carbonization furnace; The carbonization system provided by the present application realizes multi-stage self-heating of the energy closed-loop, and different energy forms are reasonably distributed in the system, improving the depth and breadth of energy utilization. This circulation mode makes full use of the energy of the syngas, can improve the energy utilization rate, reduce the production cost and meet the requirements of energy conservation and emission reduction.

[0018] The present application also provides a carbonization process, which realizes the smooth conversion from hot flue gas heating in the initial stage to syngas reflux self-heating in the normal working stage through the syngas reflux heating carbonization system, in cooperation with external raw materials, the first flue gas circulation path, the second flue gas circulation path, the third valve and the fourth valve; The whole conversion process is gradual, avoiding the impact on parameters such as the temperature and pressure in the carbonization furnace caused by the sudden change of the heating method, ensuring the stability and continuity of the carbonization process, and being beneficial to improving the quality and production efficiency of biomass carbon. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of a syngas reflux heating carbonization system provided by the present application. Detailed Embodiments

[0020] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0021] The present application provides a syngas reflux heating carbonization system, including: a carbonization furnace 10 for carbonizing biomass raw materials to generate syngas and biochar; a combustion chamber 20 disposed downstream of the carbonization furnace 10, capable of treating the syngas through low-nitrogen combustion to generate hot flue gas; a heat exchanger 30 disposed downstream of the combustion chamber 20, and the hot flue gas discharged from the combustion chamber 20 can be introduced into the heat exchanger 30 as the heat source of the heat exchanger 30; the syngas discharged from the carbonization furnace 10 has two flow directions, the first one leads to the combustion chamber 20, and after being converted into hot flue gas, it is used as the heat source of the heat exchanger 30, and the second one leads to the heat exchanger 30, and the heat exchanger 30 can adjust the temperature of the syngas entering it; the heat exchanger 30 is connected to the carbonization furnace 10, and through the heat exchanger 30, the syngas with an appropriate temperature can enter the carbonization furnace 10, serve as the heat source of the carbonization furnace 10, and contact the biomass raw materials in the carbonization furnace 10, thereby promoting the carbonization of the biomass raw materials.

[0022] Specifically, reference can be made to Figure 1 , in the figure embodiment, the carbonization furnace 10, the combustion chamber 20, and the heat exchanger 30 are interconnected through gas pipelines to form a syngas utilization loop. Among them, the carbonization furnace 10 is responsible for the carbonization of biomass raw materials. The biomass raw materials in the carbonization furnace 10 undergo pyrolysis reactions in a high-temperature and oxygen-deficient environment, decomposing to generate syngas and biochar. The combustion chamber 20 is disposed downstream of the carbonization furnace 10 and can receive and process the syngas generated by carbonization; by optimizing combustion conditions, such as staged oxygen supply, flue gas recirculation, etc., the generation of nitrogen oxides during the combustion process can be inhibited, while cleaning the syngas and reducing pollutant emissions. The heat exchanger 30 is disposed downstream of the combustion chamber 20 and is connected to the carbonization furnace 10.

[0023] It should be explained that syngas is a combustible gas mixture generated by gasifying or pyrolyzing raw materials such as biomass, coal, and organic waste. Its main components include carbon monoxide (CO), hydrogen (H2), methane (CH4), carbon dioxide (CO2), volatile organic compounds (VOCs), and solid particles (unreacted carbon particles or ash).

[0024] Since syngas is a carbonization product and does not contain oxygen, using high-temperature syngas as the carbonization heat source neither poses an explosion risk nor affects the progress of the carbonization reaction.

[0025] More specifically, a syngas discharge port is provided on the carbonization furnace 10. The discharged syngas is divided into two paths. The first path is connected to the combustion chamber 20 through a pipeline. In the combustion chamber 20, the syngas undergoes low-nitrogen combustion to generate hot flue gas. The hot flue gas enters the heat exchanger 30 along the pipeline, providing a heat source for the heat exchanger 30. The second path is connected to the heat exchanger 30 through a pipeline. After the syngas enters the heat exchanger 30, it can exchange heat with the hot flue gas serving as a heat source, so that the temperature of the syngas meets the carbonization temperature. A syngas reflux port is also provided on the carbonization furnace 10. The heat-exchanged syngas flows back into the carbonization furnace 10 through a pipeline and comes into direct contact with the biomass raw material, providing heat for the carbonization process.

[0026] Traditional carbonization systems mainly rely on external fuel for heating. The syngas reflux heating carbonization system provided in this application promotes syngas reflux heating, uses the originally wasted syngas as a heat source, improves energy utilization efficiency, reduces dependence on external fuel, and lowers production costs.

[0027] Continue to refer to Figure 1 , the syngas reflux port and the syngas discharge port are respectively arranged at both ends of the furnace chamber of the carbonization furnace 10. The refluxed syngas and the syngas generated by carbonization will continuously flow towards the discharge port under the guidance of the fan and the air flow direction, so as to act on the entire furnace chamber comprehensively, ensuring uniform heating. At the same time, the refluxed high-temperature syngas comes into direct contact with the biomass raw material, ensuring that the biomass raw material is accurately heated. The stable carbonization temperature enables the biomass raw material to be carbonized fully and evenly, reducing the situations of local overheating or incomplete pyrolysis, which is beneficial to improving carbonization efficiency and product quality stability.

[0028] Part of the syngas generated by carbonization is used for reflux heating, and another part enters the combustion chamber 20 and forms hot flue gas through low-nitrogen combustion. The main components of the hot flue gas are carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2). The hot flue gas is a relatively clean gas, meeting environmental protection requirements and can be directly discharged to the outside. The combustion chamber 20 can not only burn and process the syngas, making the entire carbonization system more environmentally friendly, but also the generated hot flue gas can be used as a heat source for the heat exchanger 30, further improving energy utilization efficiency.

[0029] The closed-loop heating and temperature regulation mechanism enhances the adaptability of the carbonization system to factors such as raw material characteristics and gas supply fluctuations, reduces system instability caused by changes in external factors, and improves the stability and reliability of system operation.

[0030] In the carbonization system provided by this application, a part of the syngas produced by the carbonization furnace 10 is converted into hot flue gas through low-nitrogen combustion in the combustion chamber 20 to supply heat to the heat exchanger 30, and the other part directly enters the heat exchanger 30, exchanges heat with the hot flue gas, obtains the carbonization temperature and then returns to the carbonization furnace 10, realizing multi-stage self-heating with an energy closed-loop. Different energy forms are reasonably distributed within the system, improving the depth and breadth of energy utilization. This circulation mode enables the full utilization of the energy of the syngas, can improve the energy utilization rate, reduce the production cost, and meet the requirements of energy conservation and emission reduction.

[0031] Optionally, the syngas reflux heating carbonization system provided by this application further includes: a first induced draft fan 51 for attracting syngas into the first syngas flow passage A; a second induced draft fan 52 for attracting syngas into the second syngas flow passage B; a flow meter 55 for monitoring the syngas flow rate in the second syngas flow passage B; as carbonization proceeds, syngas is continuously generated. To control the air pressure in the carbonization furnace 10, it is necessary to regulate the syngas flow rate entering the second syngas flow passage B; by increasing the air suction volume of the first induced draft fan 51 and / or decreasing the air suction volume of the second induced draft fan 52, the syngas flow rate entering the first syngas flow passage A can be increased and the syngas flow rate entering the second syngas flow passage B can be decreased.

[0032] Specifically, refer to Figure 1 , in the figure embodiment, a syngas discharge port is provided at the right end of the carbonization furnace 10. As the syngas is discharged, the pipeline path bifurcates. A first induced draft fan 51 is provided on the first syngas flow passage A, and the first induced draft fan 51 can guide part of the syngas into the combustion chamber 20; a second induced draft fan 52 is provided on the second syngas flow passage B, and the second induced draft fan 52 can guide another part of the syngas into the heat exchanger 30.

[0033] The induced draft fan generates negative pressure through the rotation of the impeller, thereby attracting the gas to flow. The first induced draft fan 51 and the second induced draft fan 52 respectively generate suction forces on their respective flow passages, pushing the syngas to flow in the passages towards the required equipment.

[0034] By regulating the rotational speed and / or the damper opening of the induced draft fan, the syngas flow rate in different syngas flow passages can also be adjusted.

[0035] Continue to refer to Figure 1 , on the second syngas flow passage B, a flow meter 55 is provided upstream of the heat exchanger 30 and downstream of the second induced draft fan 52. The flow meter 55 is used to monitor the syngas flow rate flowing through the second syngas flow passage B.

[0036] The flowmeter 55 is disposed downstream of the second induced draft fan 52 and upstream of the heat exchanger 30 because the temperature of the syngas in this area is relatively low (heat is dissipated during the transportation of the syngas and it is not heated by the heat exchanger 30). The gas will not affect the measurement accuracy due to thermal expansion. At the same time, in this area, the syngas does not exchange heat with the hot flue gas and is not interfered by the complex flow channels of the heat exchanger 30, and the flow is stable, which is convenient for the selection and use of the flowmeter 55.

[0037] It is easy to understand that as the carbonization progresses, more and more syngas is continuously generated. If the reflux flow rate is not controlled, the furnace pressure will increase. Excessive pressure may cause safety problems such as equipment damage and leakage, and will also affect the stability of the carbonization process and the quality of the products. Therefore, it is necessary to regulate the reflux flow rate of the syngas.

[0038] In one embodiment, by adjusting the air volume of the first induced draft fan 51, the flow rate distribution of the two paths of syngas is changed.

[0039] It is easy to understand that according to the principle of fluid mechanics, in a flow splitting system, the flow rate distribution of each branch channel depends on the resistance and power of the channel. When the air volume of the first induced draft fan 51 increases, the resistance in the first path of syngas flow channel A relatively decreases, and the syngas tends to flow into this channel, resulting in a decrease in the flow rate of the syngas entering the second path of syngas flow channel B. Similarly, when the air volume of the first induced draft fan 51 decreases, the resistance in the first path of syngas flow channel A relatively increases, and the syngas tends to flow into the second path of syngas flow channel B, resulting in an increase in the flow rate of the syngas entering the second path of syngas flow channel B.

[0040] It should be explained that there is no air pressure requirement in the syngas path formed by the first path of syngas flow channel A. Therefore, an increase or decrease in the flow rate of the syngas entering the first path of syngas flow channel A will not affect this path. When the combustion chamber 20 operates normally, the treatment of the syngas can be realized; the continuous flow of hot flue gas to the heat exchanger 30 can ensure that the heat exchanger 30 has a stable and continuous heat source, and thus ensure the heat exchange effect on the reflux syngas. The hot flue gas after heat exchange can be directly discharged externally, and the increase or decrease in the flow rate has no impact.

[0041] In another embodiment, by adjusting the air volume of the second induced draft fan 52, the flow rate distribution of the two paths of syngas is changed.

[0042] The adjustment principle of the second induced draft fan 52 is the same as above, and will not be elaborated here.

[0043] If necessary, the air volume of the first induced draft fan 51 can be increased while the air volume of the second induced draft fan 52 is decreased, so as to more efficiently control the flow rate of the syngas entering the second path of syngas flow channel B.

[0044] Effectively controlling the air pressure inside the carbonization furnace 10 can avoid equipment damage and safety accidents caused by excessive air pressure, which is beneficial to extending the service life of the equipment and ensuring the safety of operators. Stable air pressure and precise flow regulation are also beneficial to the operational stability of the carbonization system, which can reduce abnormalities in the carbonization process caused by air pressure fluctuations and unstable flow rates, and improve the reliability and production efficiency of the carbonization system.

[0045] In some embodiments, the requirements for syngas are different in different carbonization stages, and it is necessary to flexibly adjust the reflux flow rate of syngas (i.e., the syngas flow rate entering the heat exchanger 30) to ensure the efficient progress of the carbonization process. By configuring a flow meter 55 in this application, the reflux flow rate can be accurately detected. Further cooperating with the first induced draft fan 51 and the second induced draft fan 52, the reflux flow rate entering the heat exchanger 30 can be quickly adjusted according to the actual requirements of the carbonization process, so that the carbonization furnace 10 has a suitable heat source and a suitable air pressure at the same time, thereby improving the carbonization efficiency and ensuring the quality of biomass carbon.

[0046] Optionally, the syngas reflux heating carbonization system provided in this application further includes a third syngas circulation channel C. After the amount of syngas discharged from the carbonization furnace 10 is greater than the amount required to maintain the carbonization air pressure, the excess syngas can be discharged through the third syngas circulation channel C; the discharged syngas can be used for power generation or heating, thereby realizing the multi-level utilization of energy.

[0047] Specifically, reference can be made to Figure 1 , in the illustrated embodiment, the second syngas circulation channel B downstream of the second induced draft fan 52 bifurcates, one path normally leads to the heat exchanger 30, and the other path forms the third syngas circulation channel C. Part of the syngas entering the second syngas circulation channel B can be discharged through the third syngas circulation channel C.

[0048] As a combustible gas, syngas has a relatively high energy density. Connecting the third syngas circulation channel C to power generation equipment or heating equipment, the discharged syngas can be used for power generation or heating. When used for power generation, the syngas burns to release heat energy, driving a steam turbine or a gas turbine to rotate, and then driving a generator to generate electricity; when used for heating, the heat generated by the combustion of the syngas is transferred to the medium to be heated, such as hot water, air, etc., through a heat exchange device to achieve district heating or industrial heating.

[0049] After meeting the self-heating requirements of the carbonization furnace 10, using the excess syngas for power generation or heating is a further development and utilization of energy.

[0050] It is easy to understand that when the syngas is discharged through the third syngas circulation channel C, it will affect the normal reflux flow rate. Therefore, a first valve is provided on the third syngas circulation channel C; when the syngas generation amount is insufficient, the first valve is closed; when the syngas generation amount is surplus, the first valve is opened.

[0051] Specifically, the carbonization furnace 10 operates to continuously produce synthesis gas. In the early stage, the production of synthesis gas is insufficient, and there is no excess synthesis gas in the path. At this time, the first valve is closed, and the synthesis gas mainly flows in the second synthesis gas flow channel B and the first synthesis gas flow channel A. By adjusting the air extraction volume of the second induced draft fan 52 and / or the first induced draft fan 51, the synthesis gas flow in the two paths can be matched according to the synthesis gas production volume, the reflux demand volume, and the combustion heat supply demand volume. As the carbonization process progresses, the synthesis gas production gradually increases. After the synthesis gas production volume is greater than the sum of the reflux demand volume and the combustion heat supply demand volume, the first valve is opened so that the excess synthesis gas can be discharged through the third synthesis gas flow channel C.

[0052] By providing the third synthesis gas flow channel C, the excess synthesis gas can be processed with low impact (without changing the synthesis gas flow in the first synthesis gas flow channel A anymore) according to the difference between the synthesis gas production volume and the system heat cycle demand volume, and at the same time, the excess synthesis gas can be utilized to further improve the energy utilization rate.

[0053] In a specific embodiment, the second synthesis gas flow channel B located downstream of the second induced draft fan 52 bifurcates to form the third synthesis gas flow channel C; a first valve is provided on the third synthesis gas flow channel C; when the synthesis gas production volume is insufficient, the first valve is closed; when the synthesis gas production volume is surplus, the first valve is opened; by increasing the opening degree of the first valve, the discharged synthesis gas flow increases, and the synthesis gas flow flowing to the heat exchanger 30 can be reduced, so as to control the synthesis gas reflux volume and control the air pressure in the carbonization furnace 10.

[0054] In this embodiment, the third synthesis gas flow channel C is a bypass of the second synthesis gas flow channel B, which neither affects the flow of the synthesis gas in the first synthesis gas flow channel A nor can efficiently and accurately affect the flow of the synthesis gas in the second synthesis gas flow channel B.

[0055] The first valve is a valve with adjustable opening degree (such as a pneumatic valve, an electric valve, etc.). According to the principle of fluid mechanics, the flow rate of the fluid in the pipeline is related to the cross-sectional area and the pressure difference of the pipeline. In the air flow pipeline, the change in the opening degree of the first valve can change the effective cross-sectional area of the pipeline. When the opening degree of the first valve increases, the effective cross-sectional area of the pipeline increases, and under the condition of constant pressure difference, the synthesis gas flow entering the third synthesis gas flow channel C will increase; conversely, when the opening degree of the first valve decreases, the effective cross-sectional area of the pipeline decreases, and under the condition of constant pressure difference, the synthesis gas flow entering the third synthesis gas flow channel C will decrease.

[0056] Therefore, by changing the opening degree of the first valve, the opening and closing of the third synthesis gas flow channel C and the size of the synthesis gas flow entering it can be controlled.

[0057] Specifically, after the synthesis gas production amount is greater than the sum of the reflux demand amount and the combustion heat supply demand amount, the first valve opens. Under the suction of the second induced draft fan 52, the excess synthesis gas comes to the bifurcation of the second synthesis gas flow channel B, and part of the synthesis gas flows to the heat exchanger 30, and another part of the synthesis gas enters the third synthesis gas flow channel C. The flowmeter 55 is arranged downstream of the bifurcation and upstream of the heat exchanger 30 for monitoring the flow rate of the refluxed synthesis gas. By determining the difference between the detected value of the flowmeter 55 and the reflux target value, the opening degree of the first valve is controlled.

[0058] More specifically, when the detected value of the flowmeter 55 is less than the sufficient reflux target value, the first valve is in a closed state, so that the synthesis gas mainly flows to the heat exchanger 30 to promote the carbonization system to enter the normal working state. When the detected value of the flowmeter 55 is greater than the sufficient reflux target value, the first valve opens to allow the excess synthesis gas to be discharged through the third synthesis gas flow channel C. After the synthesis gas is sufficiently refluxed and the self-heating of the carbonization furnace 10 is stably achieved, by adjusting the opening degree of the first valve, the reflux target value of the synthesis gas flowing through the second synthesis gas flow channel B and entering the heat exchanger 30 is maintained.

[0059] The setting with adjustable opening degree of the first valve provides an effective flow regulation means, which can flexibly adjust the flow direction according to the change of the synthesis gas production amount, and avoid the influence on the synthesis gas flow rate in the second synthesis gas flow channel B and the first synthesis gas flow channel A.

[0060] Optionally, a second valve is provided on the second synthesis gas flow channel B; according to the detection result of the flowmeter 55, increasing or decreasing the opening degree of the second valve can quickly regulate the flow rate of the synthesis gas flowing to the heat exchanger 30.

[0061] The second valve is also a valve with adjustable opening degree (such as a pneumatic valve, an electric valve, etc.). The flowmeter 55 is arranged downstream of the second valve to facilitate quickly adjusting the reflux amount of the synthesis gas according to the detection result of the flowmeter 55.

[0062] The use principle of the second valve is similar to that of the first valve, and will not be elaborated here. After there is excess synthesis gas, open the first valve and reduce the opening degree of the second valve, then the excess synthesis gas can be promoted to be discharged until it is confirmed that the detected value of the flowmeter 55 is the reflux target value.

[0063] The flowmeter 55, as a detection element, can obtain in real time the information on the flow rate of the syngas flowing back into the second syngas flow channel B and leading to the heat exchanger 30. The flowmeter 55 can transmit the detection information to the control system. The control system can compare the detected value with the target value of the flowback, and then calculate the opening degree of the valve that needs to be adjusted according to the deviation situation, and send a control signal to the first valve and / or the second valve. For example, when the detected value of the flowmeter 55 is less than the target value of the flowback, increasing the opening degree of the second valve can promote the flow of syngas to the heat exchanger 30; when the detected value of the flowmeter 55 is greater than the target value of the flowback, decreasing the opening degree of the second valve can hinder the flow of syngas to the heat exchanger 30.

[0064] The setting of the second valve provides a direct and accurate means of flow regulation, and can quickly adjust the flow rate of the syngas flowing to the heat exchanger 30 according to actual needs.

[0065] In a specific embodiment, a first valve is provided on the third syngas flow channel C, and a second valve is provided on the second syngas flow channel B, and the second valve is in an open state all the time. After the syngas production is surplus, the first valve is opened to discharge the excess syngas. If the detected value of the flowmeter 55 is still greater than the target value of the flowback, the opening degree of the second valve is reduced to quickly control the flowback flow rate. When necessary, increasing the opening degree of the first valve can further promote the discharge of the excess syngas.

[0066] By setting the first valve and the second valve, the carbonization system can quickly respond to the changes in the flow rate requirements under different working conditions, enhance the adaptability to various biomass raw materials and carbonization processes, and improve the flexibility and reliability of the carbonization system.

[0067] Optionally, the syngas flowback heat supply carbonization system provided by the present application further includes a waste heat utilization device. The waste heat utilization device is connected to the heat exchanger 30. The hot flue gas serving as the heat source of the heat exchanger 30 still has a certain amount of heat energy after use. By enabling the flue gas with heat energy to enter the waste heat utilization device, the cascade utilization of energy can be realized.

[0068] The waste heat utilization device can be a waste heat boiler, a dryer or other devices that require a heat source to work.

[0069] In one embodiment, the heat exchanger 30 includes a housing and a flow-through pipe. The flow-through pipe is disposed inside the housing. One end of the flow-through pipe communicates with the syngas discharge port of the carbonization furnace 10, and the other end communicates with the syngas return port of the carbonization furnace 10. The returned syngas flows inside the flow-through pipe. The housing is provided with a heat source inlet and a heat source outlet. The heat source inlet communicates with the combustion chamber 20, and the heat source outlet communicates with the waste heat utilization device. The hot flue gas enters the housing through the heat source inlet, contacts the flow-through pipe, and realizes heat exchange with the returned syngas. After heat exchange, the flue gas still having heat is discharged into the waste heat utilization device through the heat source outlet, and transfers the remaining heat energy to the substance to be heated, such as the water in the waste heat boiler or the material in the dryer, thereby realizing the cascade utilization of energy and improving the comprehensive utilization rate of energy.

[0070] Optionally, the syngas return heating carbonization system provided by the present application further includes a chimney 41. The chimney 41 communicates with the heat exchanger 30 and is used for discharging flue gas.

[0071] Specifically, reference may be made to Figure 1 , in the illustrated embodiment, the chimney 41 is connected to the heat source outlet of the heat exchanger 30 through a pipe and is located at the end of the flue gas discharge of the entire carbonization system (when the carbonization system includes a waste heat utilization device, the chimney 41 is disposed downstream of the waste heat utilization device). The hot flue gas generated by the combustion chamber 20 enters the heat exchanger 30 to provide a heat source for heating the syngas in the heat exchanger 30. After heat exchange, the flue gas is discharged into the atmosphere through the chimney 41. The chimney 41 utilizes the principle of hot air rising. The temperature of the flue gas inside the chimney 41 is higher than the temperature of the surrounding ambient air, and the density of the flue gas is smaller, so it will flow upward naturally. At the same time, the height and structural design of the chimney 41 can enhance this upward suction force, ensure smooth flue gas discharge, and reduce the impact on the surrounding environment.

[0072] In one specific embodiment, the combustion chamber 20 includes an oxygen-deficient combustion section and a complete combustion section. The oxygen-deficient combustion section is configured with a burner 21 and a primary air blower, and the complete combustion section is configured with a secondary air blower. The syngas first enters the oxygen-deficient combustion section for oxygen-deficient combustion, and then enters the complete combustion section to achieve complete combustion through oxygen supplementation. The complete combustion section is provided with a cold air inlet, and the cold air inlet is adjacent to the outlet of the combustion chamber 20. By allowing normal-temperature or low-temperature gas to enter the complete combustion section through the cold air inlet, the hot flue gas about to be discharged from the complete combustion section can be cooled, so that the hot flue gas has the temperature required by the heat exchanger 30.

[0073] Specifically, in the combustion chamber 20, the oxygen-deficient combustion section is arranged in the front. The air inlet of the oxygen-deficient combustion section communicates with the syngas discharge port of the carbonization furnace 10, and the air outlet communicates with the complete combustion section. The oxygen-deficient combustion section is configured with a burner 21 and a primary air blower. The complete combustion section is arranged in the back. The air inlet of the complete combustion section communicates with the oxygen-deficient combustion section, and the air outlet communicates with the heat exchanger 30. The complete combustion section is configured with a secondary air blower. The complete combustion section is further provided with a cold air inlet, and the cold air inlet is adjacent to the air outlet of the complete combustion section.

[0074] Specifically, the carbonization furnace 10 generates synthesis gas, and part of the synthesis gas is introduced into the oxygen-deficient combustion section. The burner 21 operates, and the primary air blower supplies oxygen to keep the volume content of oxygen in the oxygen-deficient combustion section at 8% - 12%, so as to facilitate the incomplete combustion of the synthesis gas under an oxygen-deficient state. Since the synthesis gas contains combustible components such as carbon monoxide and hydrogen, under oxygen-deficient conditions, these combustible components will not burn completely instantaneously, but react gradually, partially converting into carbon dioxide and water, while releasing a certain amount of heat. The oxygen supply of the primary air blower will be adjusted in real time according to factors such as the flow rate of the synthesis gas, the composition ratio (such as the content ratio of carbon monoxide and hydrogen), and the system-set load, etc., to maintain a stable oxygen-deficient combustion state. This combustion method can control the combustion speed and temperature, effectively reducing the generation of pollutants such as nitrogen oxides.

[0075] Meanwhile, the combustion temperature in the oxygen-deficient combustion section is maintained close to 1000°C. The heat released by the incomplete combustion of the synthesis gas is the main heat source for maintaining this temperature. The temperature control is achieved through the coordinated adjustment of multiple parameters. For example, when the flow rate of the synthesis gas increases, to ensure the effect of oxygen-deficient combustion and temperature stability, the oxygen supply of the primary air blower can be increased, but still kept within the oxygen-deficient range; if the flow rate of the synthesis gas decreases, the oxygen supply is adjusted accordingly. In addition, the heat exchange situation in the combustion chamber is also referred to for fine-tuning the temperature to ensure that the temperature fluctuation range is within a reasonable interval.

[0076] The residence time of the synthesis gas in the oxygen-deficient combustion section is about 2 - 8 s (if the residence time is too short, the synthesis gas may not react sufficiently; if the residence time is too long, it will affect the combustion efficiency and the overall operation rhythm of the combustion chamber 20). This residence time can ensure that the combustible components in the synthesis gas fully undergo incomplete combustion reactions in the oxygen-deficient environment, providing a good foundation for the subsequent reactions in the complete combustion section.

[0077] The synthesis gas that has undergone oxygen-deficient combustion enters the complete combustion section carrying unburned components and intermediate products. In the complete combustion section, the secondary air blower supplies oxygen to increase the volume content of oxygen in this area to 18% - 21%, approaching the normal oxygen content level in the air. Sufficient oxygen supply can ensure that the remaining combustible components (such as carbon monoxide, hydrogen, and intermediate products generated by oxygen-deficient combustion, etc.) come into full contact with oxygen and undergo intense oxidation reactions to achieve complete combustion. The oxygen supply of the secondary air blower will be adjusted according to the composition of the synthesis gas at the outlet of the oxygen-deficient combustion section, the hot flue gas flow rate, and the actual combustion situation to achieve the best complete combustion effect.

[0078] Meanwhile, maintain the combustion temperature in the complete combustion section close to 1000 °C. The heat released by the complete combustion of the remaining combustible components is the main heat source for maintaining this temperature. This temperature can be maintained by adjusting the oxygen supply of the secondary fan. By increasing the oxygen supply, the combustion reaction becomes more intense, thereby increasing the released heat and raising the temperature. Or, a flue gas reflux channel is added to the complete combustion section. The hot flue gas generated in the combustion chamber 20 is cooled after heat exchange (through the heat exchanger 30), so that the cooled flue gas is input into the complete combustion section through the flue gas reflux channel and mixed with the secondary air and the remaining combustible components. The cooled flue gas absorbs the excess heat, causing the combustion temperature to drop back.

[0079] Ensuring that the combustion temperature is stably around 1000 °C can effectively inhibit the formation of thermal NOx at high temperatures and reduce pollutant emissions.

[0080] After two-stage combustion, the syngas is converted into relatively clean hot flue gas. In the combustion chamber 20, the temperature of the hot flue gas is close to the combustion temperature, and the combustion temperature is often higher than the carbonization temperature. Therefore, a cold air inlet is set near the outlet of the complete combustion section, and air (adding a fan to introduce air, or using the existing primary fan or secondary fan to add a branch to connect to the cold air inlet for air introduction) or cooled flue gas (connecting the heat source outlet of the heat exchanger 30 to the cold air inlet through a pipeline, or connecting the heat source outlet of the preheating utilization device to the cold air inlet through a pipeline) is introduced to cool the hot flue gas, so that the temperature of the hot flue gas is close to the carbonization temperature. The cooled hot flue gas enters the heat exchanger 30, so as to make the refluxed syngas have the temperature required for carbonization through heat exchange.

[0081] Optionally, the carbonization furnace 10 is a spiral carbonization furnace. A spiral shaft is provided in the carbonization furnace 10. After the biomass raw material is put into the carbonization furnace 10, it can be fed forward under the drive of the rotation of the spiral shaft; the rotation of the spiral shaft can also promote the mixing of the biomass raw material and the syngas, thereby improving the pyrolysis efficiency.

[0082] Specifically, refer to Figure 1, in the illustrated embodiment, a spiral shaft is installed axially inside the carbonization furnace 10. A biomass raw material inlet and a syngas return port are provided on the left side of the carbonization furnace 10, and a syngas discharge port and a biomass charcoal outlet are provided on the right end of the carbonization furnace 10. When the carbonization furnace 10 is operating, the spiral shaft rotates. After the biomass raw material is fed into the carbonization furnace 10 from the inlet, it advances along the furnace body from left to right towards the syngas discharge port and the biomass charcoal outlet under the axial thrust generated by the rotation of the spiral shaft. During this process, the biomass raw material is carbonized, and the generated syngas flows upward and is discharged through the syngas discharge port to the first syngas flow channel A and the second syngas flow channel B; the generated biomass charcoal accumulates in the lower layer and is discharged through the biomass charcoal outlet. During the advancing process, there is friction between the spiral shaft and the biomass raw material. The frictional force can not only push the biomass raw material to move forward along the spiral direction for continuous conveying, but also form a complex flow field inside the carbonization furnace 10. On the one hand, it causes the biomass raw material to tumble, and on the other hand, it stirs the syngas inside the carbonization furnace 10, promotes the syngas to fully penetrate into all parts of the biomass raw material, and promotes their mutual contact, so that the syngas can transfer heat to the biomass raw material and accelerate the pyrolysis process of the biomass raw material.

[0083] The setting of the spiral shaft enables the biomass raw material to move orderly and evenly inside the carbonization furnace 10, avoiding the problems of material accumulation and blockage. At the same time, the rotation of the spiral shaft can promote the mixing of the syngas and the biomass raw material, so that the biomass raw material can be evenly heated during the carbonization process, improving the quality and quality stability of the biomass charcoal.

[0084] Optionally, there are two flue gas flow paths at the outlet of the combustion chamber 20. The first flue gas flow path D is connected to the carbonization furnace 10, and the second flue gas flow path E is connected to the heat exchanger 30; a third valve is provided on the first flue gas flow path D; a fourth valve is provided on the second flue gas flow path E; at the initial stage, the third valve is opened and the fourth valve is closed. The combustion chamber 20 generates hot flue gas by burning raw materials such as natural gas and diesel. The hot flue gas can enter the carbonization furnace 10 through the first flue gas flow path D and directly contact the biomass raw material, promoting the carbonization of the biomass raw material to generate syngas; the syngas returns to the carbonization furnace 10 after passing through the heat exchanger 30, so that the high-temperature gas for carbonization changes from hot flue gas to a mixture of hot flue gas and syngas; as the carbonization progresses, syngas is continuously generated, and the proportion of syngas in the mixture continuously increases; after the return flow rate of the syngas meets the required amount to maintain the carbonization pressure, the third valve is closed, and the high-temperature gas for carbonization changes from the mixture to syngas.

[0085] Specifically, reference can be made to Figure 1, in the illustrated embodiment, there are two flue gas flow paths at the outlet of the combustion chamber 20. The first flue gas flow path D bypasses the heat exchanger 30 and can directly lead to the carbonization furnace 10. A third valve is installed on the first flue gas flow path D. The second flue gas flow path E is connected to the heat exchanger 30, and a fourth valve is installed on the second flue gas flow path E.

[0086] In the initial stage, the carbonization furnace 10 is not working and there is no syngas. At this time, the combustion chamber 20 generates hot flue gas by burning external fuels such as natural gas and diesel. The third valve is opened and the fourth valve is closed. The hot flue gas can only enter the carbonization furnace 10 through the first flue gas flow path D. The hot flue gas serves as the initial heat source of the carbonization furnace 10 and contacts the biomass raw materials, providing heat to promote the carbonization of the biomass raw materials. The carbonization furnace 10 enters the working state and gradually generates syngas. The syngas flows back through the first syngas flow channel A and enters the carbonization furnace 10, and cooperates with the hot flue gas to jointly serve as the carbonization heat source. To maintain the pressure inside the furnace, after the reflux syngas appears, the amount of hot flue gas entering needs to be reduced. At this time, the fourth valve is opened so that part of the hot flue gas serves as the heat source of the heat exchanger 30.

[0087] As the carbonization process progresses, the reflux flow rate of the syngas continuously increases, and the amount of hot flue gas used as the carbonization heat source decreases accordingly. After the reflux flow rate of the syngas meets the required amount to maintain the carbonization pressure, the third valve is closed. At this time, the high-temperature gas for carbonization in the carbonization furnace 10 is completely composed of syngas, realizing the transformation from external fuel heating to syngas self-heating.

[0088] Briefly speaking, in the initial stage of the operation of the carbonization system, due to the insufficient production of syngas, it is necessary to use the hot flue gas generated by the combustion of external fuels to heat the carbonization furnace 10 and start the carbonization process. As the syngas is continuously generated, the syngas is gradually introduced as the heating energy source, and finally the syngas completely replaces the external fuel for heating.

[0089] The carbonization system provided by this application realizes the transformation from external fuel heating to syngas self-heating, makes full use of the syngas generated in the carbonization process, improves the energy utilization efficiency, and reduces the production cost.

[0090] Optionally, a fifth valve is provided on the first syngas flow channel A. In the initial stage, the fifth valve is closed, and all the generated syngas enters the second syngas flow channel B for reflux.

[0091] Specifically, a flow meter 55 is provided on the second syngas flow channel B. After the flow meter 55 detects the appearance of reflux syngas, the fourth valve is opened, and the hot flue gas generated by burning external raw materials enters the heat exchanger 30 and serves as the heat source of the heat exchanger 30 to facilitate the heat exchanger 30 to heat the reflux syngas.

[0092] After the flowmeter 55 detects that the reflux flow rate of the syngas satisfies the required amount for maintaining the carbonization pressure, the fifth valve opens and the third valve closes. The refluxed syngas flows normally, and the excess syngas enters the combustion chamber 20, serves as a combustion raw material, and generates hot flue gas. Thus, there is no longer a need to burn external raw materials.

[0093] Optionally, the third valve is a valve with adjustable opening degree, and its opening degree can change according to the detection value of the flowmeter 55.

[0094] Generally speaking, as the carbonization progresses, the detection value of the flowmeter 55 will gradually increase, which indicates that the amount of refluxed syngas is increasing. To maintain the carbonization pressure, it is necessary to synchronously reduce the amount of hot flue gas introduced. Therefore, it is necessary to gradually reduce the opening degree of the third valve to prevent the hot flue gas from entering the carbonization furnace 10. The hot flue gas that does not enter the carbonization furnace 10 can enter the heat exchanger 30 through the second flue gas flow path E and be used as a heat exchange heat source.

[0095] Optionally, the fourth valve is also a valve with adjustable opening degree.

[0096] The operation of the fourth valve is similar to that of the third valve, and details will not be elaborated here. The flow direction and corresponding flow rate of the hot flue gas can be regulated by separately controlling the opening degree of the fourth valve.

[0097] In one embodiment, the opening degree of the fourth valve dynamically matches the opening degree of the third valve. When the opening degree of the third valve decreases, the opening degree of the fourth valve increases accordingly to facilitate the entry of excess hot flue gas into the heat exchanger 30.

[0098] Optionally, the carbonization furnace 10 is equipped with a temperature sensor for detecting the temperature inside the furnace to confirm whether the carbonization reaction is proceeding normally.

[0099] During use, the temperature of the hot flue gas discharged from the combustion chamber 20 can be correspondingly regulated according to the detection value of the temperature sensor to maintain the carbonization temperature.

[0100] Optionally, the carbonization furnace 10 is equipped with a pressure sensor for detecting the air pressure inside the furnace to confirm whether the carbonization reaction is proceeding normally.

[0101] Through the pressure sensor, the amount of high-temperature gas entering the carbonization furnace 10 can be replenished in a timely manner. Or, when the syngas and the hot flue gas jointly serve as the carbonization heat source, the opening degrees of the third valve and / or the fourth valve can also be dynamically adjusted through the pressure sensor to maintain the air pressure inside the furnace.

[0102] In the initial stage, the hot flue gas generated by burning external fuel often contains oxygen. It is easy to understand that when the oxygen content is too high, there is a risk of high-temperature explosion when directly introduced into the carbonization furnace 10. To ensure the safe operation of the carbonization system, it is necessary to reduce the oxygen content of the hot flue gas.

[0103] Optionally, at the starting stage, the air supply of the burner 21 is adjusted (by adjusting the primary air blower and / or the secondary air blower), and a fuel-rich combustion mode is adopted. For example, the air-fuel ratio is set to 0.9 to make the combustion close to the complete combustion state, reduce the residue of unconsumed oxygen, and lower the oxygen content of the hot flue gas.

[0104] Optionally, an oxygen sensor is provided at the outlet of the combustion chamber 20. The oxygen sensor can real-time monitor the oxygen concentration in the hot flue gas and feed the data back to the control system. The control system then adjusts the opening degree of the air valve of the blower according to the situation to ensure that the oxygen concentration of the hot flue gas ≤ 5%.

[0105] Optionally, a mixing chamber is provided at the outlet of the combustion chamber 20. The hot flue gas discharged from the combustion chamber 20 first enters the mixing chamber and then flows to the first flue gas circulation path D or the second flue gas circulation path E. An inert gas inlet is provided on the mixing chamber. When the hot flue gas is used as the heat source of the carbonization furnace 10, the inert gas inlet is opened, and inert gas (such as nitrogen, carbon dioxide) is introduced. The inert gas is used to dilute the oxygen concentration in the hot flue gas, thereby reducing the oxygen content of the hot flue gas. At this time, the inert gas can also be used as cold air to participate in the cooling of the hot flue gas.

[0106] In a specific embodiment, the burner 21 adopts a fuel-rich combustion mode, and the air-fuel ratio is 0.9 to ensure that the initial oxygen concentration of the hot flue gas is lower than 8%. A mixing chamber is provided at the outlet of the combustion chamber 20, and an oxygen sensor is provided at the outlet of the mixing chamber; after the hot flue gas enters the mixing chamber, it is mixed with nitrogen to control the oxygen concentration of the hot flue gas to be ready to enter the carbonization furnace 10 below 3%.

[0107] The present application also provides a carbonization process, which is realized by using the above-mentioned syngas reflux heating carbonization system, and includes the following steps: At the starting stage, the combustion chamber 20 generates hot flue gas by burning raw materials such as natural gas and diesel. The hot flue gas enters the carbonization furnace 10 and directly contacts with the biomass raw materials, promoting the carbonization of the biomass raw materials and generating syngas; In the transition stage, the reflux flow rate of the syngas is less than the required amount to maintain the carbonization pressure. The syngas is refluxed into the carbonization furnace 10 and used as the heat source of the carbonization furnace 10 together with the hot flue gas; In the normal working stage, the reflux flow rate of the syngas meets the required amount to maintain the carbonization pressure, and the hot flue gas no longer enters the carbonization furnace 10. Part of the syngas generated by the carbonization furnace 10 enters the combustion chamber 20, is converted into hot flue gas and used as the heat source of the heat exchanger 30. Another part of the syngas is temperature-adjusted by the heat exchanger 30 and then refluxed into the carbonization furnace 10 and used as the heat source of the carbonization furnace 10.

[0108] Specifically, in the starting stage, in the combustion chamber 20, the burner 21 burns external fuels such as natural gas and diesel, and the primary air blower provides an appropriate amount of air for combustion support. The generated hot flue gas enters the carbonization furnace 10 along the first flue gas flow path D through the opened third valve, and directly contacts the biomass raw materials put into it, transferring heat to the raw materials to promote their carbonization and generate syngas.

[0109] In the transition stage, the syngas flows back, but the reflux flow rate is less than the required amount to maintain the carbonization pressure in the furnace. At this time, the syngas does not enter the combustion chamber 20 (the fifth valve is closed), and all passes through the second syngas flow channel B and enters the heat exchanger 30 to flow back to the carbonization furnace 10. In the carbonization furnace 10, the mixture of syngas and hot flue gas is used as the carbonization heat source. To maintain the carbonization pressure in the furnace, the fourth valve is opened, and part of the hot flue gas flows to the heat exchanger 30 to be used as the heat exchange heat source. As the reflux flow rate of the syngas increases (monitored by the flowmeter 55), the input amount of the hot flue gas gradually decreases (by reducing the opening degree of the third valve and / or increasing the opening degree of the fourth valve). That is to say, as the carbonization progresses, the proportion of the hot flue gas in the mixture gas in the carbonization furnace 10 gradually decreases.

[0110] After the reflux flow rate of the syngas meets the required amount to maintain the carbonization pressure in the furnace, the third valve is closed to facilitate the syngas to completely replace the hot flue gas, and finally only the syngas is used as the carbonization heat source. At the same time, the fifth valve is opened, and the excess syngas enters the combustion chamber 20 to replace the external raw materials for combustion and generate hot flue gas.

[0111] The carbonization system enters the normal working stage. The hot flue gas no longer enters the carbonization furnace 10. Part of the syngas generated by the carbonization furnace 10 is introduced into the combustion chamber 20 by the first induced draft fan 51, and the generated hot flue gas enters the heat exchanger 30 as a heat source; the other part enters the heat exchanger 30 through the second induced draft fan 52, and after being heated to an appropriate temperature, it flows back to the carbonization furnace 10 to provide a continuous and stable heat source for carbonization.

[0112] In the normal working stage, after the flow rate of the syngas flowing to the combustion chamber 20 is saturated, the first valve can be opened to discharge the excess syngas through the third syngas flow channel C. The reflux flow rate of the syngas is monitored by the flowmeter 55, and the opening degrees of the first valve and / or the second valve are feedback-controlled to ensure that the reflux flow rate of the syngas always maintains the required amount for the carbonization pressure.

[0113] The carbonization process provided by this application, through the syngas reflux heating carbonization system, in cooperation with external raw materials, the first flue gas circulation path D, the second flue gas circulation path E, the third valve and the fourth valve, realizes the smooth conversion from heat supply by hot flue gas in the initial stage to self-heating by syngas reflux in the normal working stage. The whole conversion process is gradual, avoiding the impact on parameters such as temperature and pressure in the carbonization furnace caused by sudden changes in the heat supply method, ensuring the stability and continuity of the carbonization process, and being beneficial to improving the quality and production efficiency of biomass carbon. Further, with the linkage control among the flowmeter, the induced draft fan and the valves, the carbonization process provided by this application realizes the automatic operation of the conversion of the heat supply method. The system can automatically adjust the valve opening and gas flow direction according to the changes in parameters such as the syngas reflux flow rate, without frequent manual intervention, improving the automation degree of the production process and the accuracy of operation, reducing the errors and failures caused by human factors, and enhancing the reliability and stability of the system.

[0114] The above embodiments only represent several implementation manners of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can still be made, and these all belong to the protection scope of this application. Therefore, the protection scope of the patent of this application shall be subject to the appended claims.

Claims

1. A synthesis gas reflux heating carbonization system, characterized in that: include: A carbonization furnace (10) is used to carbonize biomass raw materials to generate synthesis gas and biochar; A combustion chamber (20) is disposed downstream of the carbonization furnace (10) and is capable of treating the synthesis gas through low-nitrogen combustion to generate hot flue gas; A heat exchanger (30) is arranged downstream of the combustion chamber (20), and hot flue gas discharged from the combustion chamber (20) can be passed into the heat exchanger (30) to serve as a heat source for the heat exchanger (30); The synthesis gas discharged from the carbonization furnace (10) has two flow directions, the first flow direction leading to the combustion chamber (20), and being converted into hot flue gas and used as a heat source for the heat exchanger (30), and the second flow direction leading to the heat exchanger (30), and the heat exchanger (30) is capable of adjusting the temperature of the synthesis gas entering therein; The heat exchanger (30) is connected to the carbonization furnace (10), and the synthesis gas having a suitable temperature can enter the carbonization furnace (10) through the heat exchanger (30), serve as a heat source for the carbonization furnace (10), and contact the biomass raw material in the carbonization furnace (10), thereby promoting the carbonization of the biomass raw material.

2. The synthesis gas reflux heating carbonization system according to claim 1, characterized in that: Also includes: A first induced draft fan (51) for drawing synthesis gas into a first synthesis gas flow channel (A); A second induced draft fan (52) is used to draw the synthesis gas into the second synthesis gas flow channel (B); A flow meter (55) for monitoring the flow rate of synthesis gas in the second synthesis gas flow channel (B); As carbonization proceeds, synthesis gas is continuously generated. In order to control the gas pressure in the carbonization furnace (10), it is necessary to regulate the flow rate of the synthesis gas entering the second synthesis gas flow channel (B); By increasing the induced air volume of the first induced draft fan (51) and / or decreasing the induced air volume of the second induced draft fan (52), the flow rate of synthesis gas entering the first synthesis gas circulation channel (A) can be increased and the flow rate of synthesis gas entering the second synthesis gas circulation channel (B) can be decreased.

3. The synthesis gas reflux heating carbonization system according to claim 2, characterized in that: It also comprises a third synthesis gas circulation channel (C), and when the amount of synthesis gas discharged from the carbonization furnace (10) is greater than the amount required to maintain the carbonization gas pressure, the excess synthesis gas can be discharged through the third synthesis gas circulation channel (C); The exhausted syngas can be used to generate electricity or heat, thus achieving multi-level utilization of energy.

4. The synthesis gas reflux heating carbonization system according to claim 3, characterized in that: The second synthesis gas flow channel (B) located downstream of the second induced draft fan (52) is bifurcated to form the third synthesis gas flow channel (C); The third synthesis gas flow channel (C) is provided with a first valve; When the amount of synthesis gas generated is insufficient, the first valve is closed; When the amount of synthesis gas generated is surplus, the first valve is opened; By increasing the opening of the first valve, the flow rate of the discharged synthesis gas is increased, and the flow rate of the synthesis gas flowing to the heat exchanger (30) can be reduced, so as to control the reflux rate of the synthesis gas and the gas pressure in the carbonization furnace (10).

5. The synthesis gas reflux heating carbonization system according to claim 2, characterized in that: A second valve is provided on the second synthesis gas flow channel (B); By increasing or decreasing the opening of the second valve according to the detection result of the flow meter (55), the flow rate of the synthesis gas flowing to the heat exchanger (30) can be quickly regulated.

6. The synthesis gas reflux heating carbonization system according to claim 1, characterized in that: Also includes: A waste heat utilization device is connected to the heat exchanger (30), and the hot flue gas serving as a heat source of the heat exchanger (30) still has a certain amount of thermal energy after use, so that the flue gas with thermal energy enters the waste heat utilization device, thereby realizing cascade utilization of energy; And / or, a chimney (41), connected to the heat exchanger (30), for discharging flue gas.

7. The synthesis gas reflux heating carbonization system according to claim 1, characterized in that: The combustion chamber (20) comprises an oxygen-deficient combustion section and a complete combustion section, the oxygen-deficient combustion section is equipped with a burner (21) and a primary air fan, and the complete combustion section is equipped with a secondary air fan; The synthesis gas first enters the oxygen-deficient combustion section for oxygen-deficient combustion, and then enters the complete combustion section to achieve complete combustion by supplementing oxygen; The complete combustion section is provided with a cold air inlet, and the cold air inlet is adjacent to the outlet of the combustion chamber (20); By allowing normal temperature or low temperature gas to enter the complete combustion section through the cold air inlet, the hot flue gas about to be discharged from the complete combustion section can be cooled so that the hot flue gas has the temperature required by the heat exchanger (30).

8. The synthesis gas reflux heating carbonization system according to claim 1, characterized in that: The carbonization furnace (10) is a spiral carbonization furnace, and a spiral shaft is provided in the carbonization furnace (10). After the biomass raw material is put into the carbonization furnace (10), it can be fed forward under the rotation of the spiral shaft; The rotation of the screw shaft can also promote the mixing of biomass raw materials and synthesis gas, thereby improving the pyrolysis efficiency.

9. The synthesis gas reflux heating carbonization system according to any one of claims 1 to 8, characterized in that: The combustion chamber (20) has two flue gas flow paths at its outlet, the first flue gas flow path (D) being connected to the carbonization furnace (10), and the second flue gas flow path (E) being connected to the heat exchanger (30); A third valve is provided on the first smoke flow path (D); A fourth valve is provided on the second smoke flow path (E); In the initial stage, the third valve is opened and the fourth valve is closed, and the combustion chamber (20) generates hot flue gas by burning raw materials such as natural gas and diesel, and the hot flue gas can enter the carbonization furnace (10) through the first flue gas flow path (D) and directly contact the biomass raw material, thereby promoting the carbonization of the biomass raw material and generating synthesis gas; The synthesis gas flows back into the carbonization furnace (10) after passing through the heat exchanger (30), so that the high-temperature gas for carbonization changes from hot flue gas to a mixture of hot flue gas and synthesis gas; As carbonization proceeds, synthesis gas is continuously produced, and the proportion of synthesis gas in the mixed gas increases continuously; After the reflux flow rate of the synthesis gas meets the required amount for maintaining the carbonization gas pressure, the third valve is closed, and the high-temperature gas for carbonization changes from the mixed gas to the synthesis gas.

10. A carbonization process, implemented by the synthesis gas reflux heating carbonization system according to claim 9, characterized in that: The following steps are involved: In the initial stage, the combustion chamber (20) generates hot flue gas by burning raw materials such as natural gas and diesel, and the hot flue gas enters the carbonization furnace (10) and directly contacts the biomass raw materials, thereby promoting carbonization of the biomass raw materials and generating synthesis gas; In the transition phase, the reflux flow rate of the synthesis gas is less than the amount required to maintain the carbonization gas pressure, and the synthesis gas is refluxed into the carbonization furnace (10) and used together with the hot flue gas as a heat source for the carbonization furnace (10); During the normal working stage, the reflux flow rate of the synthesis gas meets the amount required to maintain the carbonization gas pressure, and the hot flue gas no longer enters the carbonization furnace (10). Part of the synthesis gas generated by the carbonization furnace (10) enters the combustion chamber (20), is converted into hot flue gas, and is used as a heat source for the heat exchanger (30), while another part of the synthesis gas is temperature-controlled by the heat exchanger (30) and refluxed into the carbonization furnace (10) to serve as a heat source for the carbonization furnace (10).

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