An internally heated rotary carbonization furnace with bidirectional flow heating and its process control method

Abstract

A bidirectional flow heating internal heating rotary carbonization furnace and its process control method are disclosed, relating to a carbonization apparatus. It includes a feeder, a bidirectional flow rotary kiln, a high-temperature gas duct, a discharge cabinet, a cooling carbon collector, a low-temperature gas duct, a medium-temperature gas duct, a two-stage combustion furnace, a high-temperature flue, and a circulating control piping system. Raw material carbonization undergoes two stages: a counter-current carbonization stage, mainly completed in the counter-current carbonization furnace section, where the raw material flows downwards and the flue gas flows upwards, and most of the moisture in the raw material is gasified in this stage; and a co-current carbonization stage, mainly completed in the co-current carbonization furnace section, where both the raw material and flue gas move downwards, and most of the organic matter in the raw material is decomposed in this stage. A process control method is provided, including ignition, heating, feeding carbonization, gas ring formation, two-stage combustion, energy self-supply, control of carbonization temperature, and control of gas flow rate. Compared with previous carbonization systems, this method omits the additional drying step, simplifies equipment, and ensures the stability of the carbonization effect.

Description

Technical Field

[0001] This invention relates to a carbonization apparatus, specifically to an internally heated rotary carbonization furnace with bidirectional flow heating and a process control method. Background Technology

[0002] Biomass includes plants, animals, and microorganisms; all living, growing organic matter can be called biomass. Biomass pyrolysis and carbonization is one of the important ways to utilize biomass energy at present, and research and development of biomass pyrolysis and carbonization processes and equipment should be vigorously promoted. As one of the earliest, most widely used, and still extensively used energy sources in human history, biomass energy still has great potential and room for development. Not only does it have excellent renewability, but its environmentally friendly characteristics also make it a future energy trend.

[0003] In recent years, my country has vigorously supported the development and utilization of biomass energy, leading to the rapid development and optimization of pyrolysis processes and equipment. Carbonization devices for biomass energy are generally carbonization furnaces, which can be further divided into externally heated and internally heated types. Among these, the internally heated carbonization furnace, designed with a large cavity, offers advantages such as simple operation, uniform material distribution and heating, high thermal efficiency, low investment, rich industrial operating experience, and large production capacity, making it an excellent type of low-temperature pyrolysis furnace. However, this technology also suffers from problems such as small single-furnace production scale, outdated automation control, limited raw material sources, and high energy consumption, which have become the primary obstacles to the efficient, environmentally friendly, and clean conversion and utilization of low-rank coal.

[0004] Chinese patent CN111056553A discloses a high-yield rotary carbonization furnace for producing activated carbon. The device includes a self-rotating furnace body, with the furnace tail height higher than the furnace head. A central air duct is located at the center of the furnace body, and several chambers are arranged along the central air duct within the furnace body. Several trapezoidal steps are arranged along the walls of each chamber, which can increase the yield of activated carbon. However, the carbonization method used in this equipment does not fully utilize the pyrolysis gas generated from the material, resulting in high energy consumption.

[0005] Chinese patent CN207435036U discloses a high-efficiency rotary steam activation furnace. This furnace has a spiral steam pipe connected to a steam layer on its inner wall, and several steam nozzles are evenly arranged around its outer wall. This design increases the contact area between steam and materials, allowing for full contact and improving efficiency and output. However, this patent has some shortcomings, lacking in wear resistance, high-temperature resistance, and steam preheating. Furthermore, the wear of the coal on the furnace inner wall and the corrosion of the furnace body by high-temperature flue gas and steam during use are not adequately considered.

[0006] Chinese patent CN118745356A discloses an anaerobic countercurrent rotary biomass carbonization furnace. Combining the principle of an externally heated fixed-bed carbonization furnace, it utilizes a rotary furnace body, offering advantages such as higher gas-solid heat transfer efficiency, faster biomass heating rate, and more uniform temperature distribution. Through the design of the return gas pipe and hot air furnace, it achieves the recovery and combustion of uncooled carbonization gas, effectively recovering and utilizing combustible gas, saving energy and reducing emissions.

[0007] Most existing biomass carbonization furnaces typically employ only counter-current or co-current unidirectional heating carbonization methods. This unidirectional flue gas flow means that the gaseous products of biomass pyrolysis are not separable. To avoid the impact of moisture content in the biomass feedstock on the calorific value of the pyrolysis gas (fuel gas), it is often necessary to dry the biomass feedstock before it enters the furnace when pyrolyzing feedstocks with high moisture content. This necessitates additional drying equipment to ensure successful carbonization, resulting in complex system structures and high equipment investment. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing carbonization equipment and processes by providing an internally heated rotary carbonization furnace with bidirectional flow heating, which features resource conservation, good stability of the thermal circulation system, high production efficiency, and stable quality of the carbonized material.

[0009] Another objective of this invention is to provide a process control method for an internally heated rotary carbonization furnace with bidirectional flow heating.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following specific solutions.

[0011] This invention provides an internally heated rotary carbonization furnace with bidirectional flow heating, comprising: a feeder, a bidirectional flow rotary kiln, a high-temperature gas duct, a discharge cabinet, a cooling carbon discharger, a low-temperature gas duct at the kiln tail, a medium-temperature gas duct at the kiln head, a two-stage combustion furnace, a high-temperature flue, and a circulating control pipeline system.

[0012] The feeder is located at the raw material inlet end of the kiln tail of the bidirectional rotary kiln and is used to push the raw material into the interior of the bidirectional rotary kiln.

[0013] The dual-flow rotary kiln adopts the form of a rotary kiln, and the kiln body is divided into a counter-flow carbonization furnace section and a co-flow carbonization furnace section. The section near the raw material inlet at the kiln tail is the counter-flow carbonization furnace section, and the section near the carbonized material outlet at the kiln head is the co-flow carbonization furnace section.

[0014] The inlet of the high-temperature gas passage is connected to a circulating control pipeline system, and the outlet of the high-temperature gas passage is inserted into the interior of the forward and reverse flow kiln and fixed by a support rod and a high-temperature rotary joint.

[0015] The discharge cabinet is located at the kiln head carbonized material outlet end of the bidirectional rotary kiln and is used to separate the carbonized material from the flue gas.

[0016] The cooling charcoal outlet is located at the bottom of the discharge cabinet and is used to cool the carbonized material and send it outside the device for packaging.

[0017] The low-temperature gas passage is located at the raw material inlet end of the kiln tail of the forward and reverse flow kiln, and collects the low-temperature gas generated in the counter-current carbonization furnace section through a jacket; a low-temperature gas fan is installed in the middle of the low-temperature gas passage to provide power for the flow of low-temperature gas.

[0018] The medium-temperature gas passage is located on the discharge cabinet, which draws out the medium-temperature gas generated in the co-current carbonization furnace section;

[0019] The two-stage combustion furnace is a device for burning low-temperature gas and sub-high-temperature gas. In terms of form, it can be an independent combustion device or a combustion furnace of a boiler. The generated high-temperature flue gas enters the high-temperature flue, and the excess flue gas is sent to the waste heat utilization device.

[0020] The inlet end of the high-temperature flue is connected to a two-stage combustion furnace, and the outlet end is connected to a circulating control pipeline system to draw out the high-temperature flue gas.

[0021] The circulating control pipeline system has a two-inlet and two-outlet pipeline structure, which introduces high-temperature flue gas through a high-temperature flue and medium-temperature gas through a medium-temperature gas duct; the generated secondary high-temperature gas is led out through the secondary high-temperature gas duct to the two-stage combustion furnace; and the generated high-temperature gas is led out through the high-temperature gas duct to the forward and reverse flow kiln.

[0022] The bidirectional rotary kiln uses high-temperature gas as the heat source for carbonization of raw materials. The high-temperature gas in the kiln is divided into two parts: one part is powered by a low-temperature gas blower and flows upward (towards the tail of the kiln) into the counter-current carbonization section; the other part is powered by a circulating control pipeline system and flows downward (towards the head of the kiln) into the co-current carbonization section. In the counter-current carbonization section, a counter-current heating method is used, with the raw material flowing downwards and the high-temperature gas flowing upwards. In the co-current carbonization section, a co-current heating method is used, with both the raw material and the high-temperature gas flowing downwards. In the counter-current carbonization section, the raw material is first dehydrated before carbonization; therefore, the low-temperature gas generated in the counter-current carbonization section contains a large amount of water vapor, has a low calorific value, and is difficult to sustain combustion independently in air. In the counter-current carbonization section, a large amount of the organic components of the raw material undergoes pyrolysis, producing medium-temperature gas with a low water vapor content, a high calorific value, and easy combustion.

[0023] This invention addresses the constraints of medium-temperature and low-temperature combustion gases generated in bidirectional rotary kilns by employing a unique two-stage combustion furnace design. The two-stage combustion furnace comprises two zones: a high-temperature combustion zone and a medium-temperature combustion zone. The high-temperature combustion zone is connected to a secondary high-temperature combustion gas duct and a blower to fully combust the secondary high-temperature combustion gas, generating high-temperature flue gas. The medium-temperature combustion zone is connected to a low-temperature combustion gas duct. The high-temperature flue gas enters the medium-temperature combustion zone and undergoes combustion with the low-temperature combustion gas. This combustion process includes two stages: a physical process, or "forging," where the high-temperature flue gas physically mixes with the water vapor in the low-temperature combustion gas to raise its temperature; and a chemical process, or "combustion," where the combustible components in the low-temperature combustion gas combine with the oxygen in the high-temperature flue gas, releasing heat through combustion. An auxiliary blower can also be installed in the medium-temperature combustion zone to supplement the air required for the chemical combustion process. In the combustion forging process of this invention, high-temperature flue gas is used to physically raise the temperature of water vapor contained in low-temperature fuel gas; and the "high-temperature oxygen" contained in the high-temperature flue gas is used to combust and release heat with the combustible portion contained in the low-temperature fuel gas. The two-stage combustion furnace provided by this invention can ensure stable combustion of low-temperature fuel gas with high water vapor content and low calorific value.

[0024] At the furnace head of the bidirectional rotary kiln, there exists a circulating control pipeline system. This circulating control pipeline system has a ring-shaped topology, consisting of a medium-temperature semi-ring and a high-temperature semi-ring. The medium-temperature and high-temperature semi-rings are interconnected, with the high-temperature flue gas inlet of the high-temperature flue and the gas inlet of the medium-temperature gas duct serving as the boundary. The medium-temperature semi-ring includes: a medium-temperature gas duct, a gas blower, a medium-temperature semi-ring valve, and sequentially connected pipes. The high-temperature semi-ring includes: a high-temperature flue, a carbonization blower, a high-temperature semi-ring valve, and sequentially connected pipes. The high-temperature and medium-temperature semi-rings are completely symmetrical in structure and are interconnected to form a complete ring-shaped topology pipeline structure. Specifically, the gas blower and carbonization blower are symmetrical; the medium-temperature semi-ring valves and high-temperature semi-ring valves are symmetrical; the medium-temperature gas duct and the high-temperature flue are symmetrical; and the high-temperature gas duct and the sub-high-temperature gas duct are symmetrical.

[0025] In the circulating control pipeline system provided by this invention, the sub-high temperature gas flows sequentially through the gas blower and the medium temperature semi-circular valve; after being heated to high temperature gas, it flows through the carbonization blower and the high temperature semi-circular valve, and after being cooled to sub-high temperature gas, it returns to the gas blower, thus forming a circulating flow of gas, i.e., a gas ring; when the medium temperature semi-circular valve and the high temperature semi-circular valve are fully open, the gas in the entire annular pipeline system forms the largest gas ring. Reducing the opening of the medium-temperature semi-annular valve increases the outflow of the secondary high-temperature gas in the gas ring. Simultaneously, based on the ring's characteristics, the inflow of high-temperature flue gas into the gas ring also increases, thereby raising the high-temperature gas temperature and increasing the carbonization temperature; conversely, increasing the opening of the high-temperature semi-annular valve increases the inflow of the medium-temperature gas in the gas ring. Simultaneously, based on the ring's characteristics, the outflow of high-temperature gas into the gas ring also increases, thereby increasing the gas flow rate; conversely, increasing the opening of the high-temperature semi-annular valve also increases the gas flow rate. Therefore, the circulating control pipeline system provided by this invention can adjust the gas flow rate delivered to the forward and reverse flow kiln and regulate the gas temperature in the high-temperature gas passage.

[0026] The temperature of the low-temperature gas is between 100 and 250°C; the temperature of the medium-temperature gas is between 200 and 300°C; the temperature of the sub-high-temperature gas is between 300 and 500°C; the temperature of the high-temperature gas is above 400°C; and the temperature of the high-temperature flue gas is above 700°C.

[0027] In the equipment provided by this invention, the carbonization of raw materials in the bidirectional rotary kiln mainly goes through two stages, with heating methods in two directions in the bidirectional rotary kiln. Therefore, this invention is called "bidirectional rotary kiln".

[0028] The first stage is the counter-current carbonization stage, mainly completed in the counter-current carbonization furnace section. This stage uses a heating method where the raw material flows downwards and the combustion gas flows upwards (counter-current). Most of the moisture in the raw material is evaporated and carried away by the counter-current combustion gas, producing low-calorific-value pyrolysis gas which is then fed into the medium-temperature combustion zone of the two-stage combustion furnace. The second stage is the co-current carbonization stage, also mainly completed in the co-current carbonization furnace section. This stage uses a heating method where both the raw material and combustion gas flow downwards (co-current). The raw material undergoes carbonization and pyrolysis under the action of the combustion gas, producing high-calorific-value pyrolysis gas which is then fed into the high-temperature combustion zone of the two-stage combustion furnace.

[0029] In the first stage, the counter-current carbonization stage, raw materials are fed into the kiln in both forward and reverse directions via a feeder, entering the counter-current carbonization section from the raw material inlet at the kiln tail. After passing through the counter-current carbonization section, the raw materials then enter the forward-current carbonization section. Gas fuel enters the counter-current carbonization section from the middle section of the kiln via a high-temperature gas duct. In the counter-current carbonization section, the gas fuel flows upwards, counter-currently to the raw material, with the gas gradually decreasing in temperature from high to low. Meanwhile, the raw material is heated to near-medium temperature by the gas fuel. During this process, a large amount of moisture in the raw material vaporizes into water vapor, while some of the organic matter in the raw material decomposes into cracked gas. This mixed gas is then carried out of the kiln by the counter-current gas fuel and enters the medium-temperature combustion zone of the two-stage combustion furnace via the low-temperature gas duct.

[0030] In the second stage, the co-current carbonization stage, the raw material passes through the counter-current carbonization section in the bi-directional rotary kiln and enters the co-current carbonization section. In the co-current carbonization section, the raw material undergoes high-temperature pyrolysis and finally enters the discharge box and cooling extruder for discharge. The fuel gas enters the co-current carbonization section from the middle section of the bi-directional rotary kiln through a high-temperature gas duct. In the co-current carbonization section, both the fuel gas and raw material flow downwards (in the same direction), and the fuel gas temperature gradually decreases from high to medium. During this process, the organic matter in the raw material is further pyrolyzed, while most of the moisture is decomposed. Therefore, the pyrolyzed gas produced in the co-current carbonization section has a high calorific value. This mixed gas is then carried out of the bi-directional rotary kiln by the co-current fuel gas and enters the high-temperature combustion zone of the two-stage combustion furnace through the medium-temperature gas duct, the circulating control pipeline system, and the secondary high-temperature gas duct.

[0031] The equipment provided by this invention, when operated according to the following process control method, can achieve the expected beneficial effects. A process control method for an internally heated rotary carbonization furnace with bidirectional flow heating includes the following steps:

[0032] Step 1, Ignition: The high-temperature combustion zone of the two-stage combustion furnace is heated by an auxiliary burner; the auxiliary burner can be a biomass pellet burner, natural gas burner, wood-burning stove, electric furnace, or other heating equipment.

[0033] Step 2, Heating: The high-temperature flue gas is drawn out to the high-temperature gas duct by the carbonization blower of the circulating control pipeline system to heat the forward and reverse flow kiln; the cooled high-temperature flue gas is drawn out to the medium-temperature combustion zone by the low-temperature gas blower, and then sent to the waste heat utilization equipment through the outlet of the two-stage combustion furnace before being discharged.

[0034] Step 3, Feeding and Carbonization: The raw materials are pushed into the interior of the rotary kiln in both forward and reverse directions using a feeder; low-temperature gas is drawn out using a low-temperature gas duct; and medium-temperature gas is drawn out using a medium-temperature gas duct.

[0035] Step 4, Gas ring formation: In the circulating control pipeline system, the secondary high temperature gas flows through the gas blower and the medium temperature semi-circular valve in sequence; after being heated to high temperature gas, it flows through the carbonization blower and the high temperature semi-circular valve, and after being cooled to secondary high temperature gas, it returns to the gas blower, thus forming a circulating flow of gas, i.e., a gas ring.

[0036] Step 5, two-stage combustion: The secondary high-temperature gas drawn from the circulating control pipeline system provides fuel for the high-temperature combustion zone of the two-stage combustion furnace (8) to form high-temperature flue gas and ensure the stability of the combustion furnace; the low-temperature gas enters the medium-temperature combustion zone through the low-temperature gas passage to realize the combustion of low-calorific-value cracked gas.

[0037] Step 6, self-sufficiency of energy: After the high-temperature flue gas generated by the two-stage combustion furnace provides carbonization energy for the forward and reverse flow rotary kiln, the auxiliary burner is turned off to achieve self-sufficiency of energy; excess flue gas is sent to waste heat utilization equipment to achieve efficient energy utilization.

[0038] Step 7, Control of carbonization temperature: In the circulating control pipeline system, reducing the opening of the medium-temperature semi-ring valve will increase the outflow of the secondary high-temperature gas in the gas ring; at the same time, according to the characteristics of the ring, the inflow of high-temperature flue gas in the gas ring will also increase accordingly, thereby increasing the temperature of the high-temperature gas and increasing the carbonization temperature; the reverse is also true.

[0039] Step 8, Gas flow regulation: In the circulating regulation pipeline system, reducing the opening of the high-temperature semi-ring valve will increase the inflow of medium-temperature gas in the gas ring; at the same time, according to the characteristics of the ring, the outflow of high-temperature gas in the gas ring will also increase accordingly, thereby achieving the effect of increasing the gas flow; and vice versa.

[0040] As can be seen from the above steps, the key to realizing the preset process in the equipment provided by the present invention lies in controlling two stages: the ignition stage and the energy self-supply stage.

[0041] During the ignition stage, auxiliary burners (such as biomass pellet burners, natural gas burners, wood-burning stoves, electric furnaces, etc.) provide heat in the high-temperature combustion zone of the two-stage combustion furnace, raising the temperature of the two-stage combustion furnace until it can provide high-temperature flue gas to heat the entire carbonization system, thereby achieving feeding and carbonization.

[0042] In the energy self-sufficiency stage, the two-stage combustion furnace supplies high-temperature flue gas to the carbonization system through a high-temperature flue. The high-temperature flue gas mixes with the secondary high-temperature fuel gas to form high-temperature fuel gas, which is then fed into the bidirectional rotary kiln to provide energy for the carbonization of the raw materials. Simultaneously, the medium-temperature and low-temperature fuel gas produced from the cracking of the raw materials is returned to the two-stage combustion furnace as fuel. Furthermore, the auxiliary burner can be shut off, thus achieving cyclical operation under energy self-sufficiency conditions.

[0043] The bidirectional rotary kiln provided by this invention generates two streams of fuel gas: low-temperature fuel gas and medium-temperature fuel gas. The low-temperature fuel gas contains a large amount of water vapor and has a low calorific value, making it difficult to maintain stable combustion in air. Therefore, in the equipment of this invention, a circulating control pipeline system is used to first send the high-calorific-value fuel gas into the high-temperature combustion zone. The high-temperature flue gas generated in the high-temperature combustion zone ensures both the stability of the combustion furnace and the normal operation of the carbonization system. Then, the low-calorific-value fuel gas enters the medium-temperature calcination zone of the two-stage combustion furnace. The water vapor contained in the low-temperature fuel gas only affects the temperature of the medium-temperature calcination zone and the combustion furnace outlet, without affecting the temperature of the high-temperature combustion zone. Excess flue gas in the two-stage combustion furnace is sent to waste heat recovery equipment through the combustion furnace outlet. This ensures the stable operation of both the combustion furnace and the carbonization rotary kiln while achieving efficient energy utilization.

[0044] The circulating control pipeline system provided by this invention can achieve dual control of carbonization temperature and gas flow rate. Within the circulating control pipeline system, the sub-high temperature gas in the sub-high temperature gas channel mixes with high temperature flue gas to form high temperature gas, which then enters the medium temperature semi-ring through a high temperature semi-ring valve, thus forming a circulating flow of gas, i.e., a gas ring. In the gas ring, the function of the medium temperature semi-ring valve is to adjust the inflow of high temperature flue gas, thereby controlling the temperature of the high temperature gas, i.e., controlling the carbonization temperature; the function of the high temperature semi-ring valve in the gas ring is to adjust the inflow of medium temperature gas, thereby controlling the outflow of high temperature gas, i.e., controlling the gas flow rate. Therefore, the circulating control pipeline system designed in this invention, utilizing the characteristics of a ring, can effectively achieve dual control of carbonization temperature and gas flow rate.

[0045] In this invention, the temperature of the low-temperature gas is between 100 and 250°C; the temperature of the medium-temperature gas is between 200 and 300°C; the temperature of the sub-high-temperature gas is between 300 and 500°C; the temperature of the high-temperature gas is above 400°C; and the temperature of the high-temperature flue gas is above 700°C.

[0046] The present invention has the following beneficial effects:

[0047] ① In the bidirectional rotary kiln of this invention, during the carbonization of raw materials, since the temperature at which moisture in the raw materials vaporizes is much lower than the temperature at which organic matter in the raw materials decomposes, most of the moisture in the raw materials vaporizes during the counter-current carbonization stage, while most of the organic matter in the raw materials decomposes during the co-current carbonization stage. Therefore, the moisture in the raw materials is mainly concentrated in the low-temperature fuel gas, while the calorific value of the medium-temperature fuel gas is almost unaffected by the moisture content of the raw materials. Compared with conventional carbonization rotary kilns, the bidirectional rotary kiln eliminates the additional drying step, simplifies the system, and reduces costs.

[0048] ② The two-stage combustion furnace of this invention employs two-stage combustion technology, consisting of a high-temperature combustion zone and a medium-temperature combustion zone, respectively designed to handle high-calorific-value and low-calorific-value fuel gases. The high-temperature combustion zone utilizes sub-high-temperature fuel gas, which is completely combusted with the assistance of a blower, generating stable high-temperature flue gas. Simultaneously, the medium-temperature combustion zone receives low-temperature fuel gas and raises its temperature through a "combustion-calcination" process—the high-temperature flue gas physically heats the water vapor in the low-temperature fuel gas, while simultaneously causing a combustion reaction between the combustible components in the fuel gas and the oxygen contained in the high-temperature flue gas, further releasing heat. This two-stage combustion design ensures that the low-temperature fuel gas with a high moisture content can also burn stably in the medium-temperature combustion zone without affecting the temperature of the high-temperature combustion zone, guaranteeing the continuous and stable operation of the system.

[0049] ③ The circulating control pipeline system of this invention adopts a ring topology structure, consisting of a high-temperature semi-ring and a medium-temperature semi-ring, which can control the flow rate and temperature of the gas in each region. Utilizing the design concept of the gas ring, the temperature and flow rate of the high-temperature gas entering the bidirectional rotary kiln can be adjusted by regulating the opening of the valves in the high-temperature and medium-temperature semi-rings. For example, reducing the opening of the medium-temperature semi-ring valve increases the inflow of high-temperature flue gas. Based on the characteristics of the gas ring, the inflow of high-temperature flue gas into the gas ring also increases accordingly, thereby increasing the temperature of the high-temperature gas. Similarly, based on the characteristics of the gas ring, reducing the opening of the high-temperature semi-ring valve increases the flow rate of the high-temperature gas. This design not only simplifies process control but also improves the controllability and flexibility of the production process, facilitating dual control of carbonization temperature and gas flow rate, enabling the system to adapt to different process requirements. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of the circulating control pipeline system of the present invention.

[0052] The following are the markings on the components in the diagram: feeder (1), forward and reverse flow rotary kiln (2), high temperature gas duct (3), discharge cabinet (4), cooling charcoal outlet (5), low temperature gas duct (6), medium temperature gas duct (7), two-stage combustion furnace (8), high temperature flue (9) and circulating control pipeline system (10), low temperature gas blower (11), gas blower (12), medium temperature semi-circular valve (13), carbonization blower (14), high temperature semi-circular valve (15), blower (16), auxiliary blower (17), waste heat utilization equipment (18), feed screw (19), secondary high temperature gas duct (20). Detailed Implementation

[0053] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. The scope of protection of the present invention is not limited to the embodiments, and any modifications made by those skilled in the art within the scope defined by the claims also fall within the scope of protection of the present invention.

[0054] See Figure 1 An embodiment of an internally heated rotary carbonization furnace with bidirectional flow heating includes a feeder 1, a bidirectional flow rotary kiln 2, a high-temperature gas duct 3, a discharge cabinet 4, a cooling carbon discharger 5, a low-temperature gas duct 6, a medium-temperature gas duct 7, a two-stage combustion furnace 8, a high-temperature flue 9, and a circulating control pipeline system 10.

[0055] The feeder 1 is located at the raw material inlet end of the kiln tail of the bidirectional rotary kiln 2, and is used to push the raw material into the interior of the bidirectional rotary kiln 2 through the feed screw 19. The feeder 1 is a funnel-shaped container with an open size of 1.5m × 1.5m. The feeder 1 is connected to the top of the feeder 1 by a feed conveyor belt, and the bottom of the feeder 1 is connected to the feed screw 19 with a diameter of Φ0.5 × 3m.

[0056] The bidirectional rotary kiln 2 adopts a rotary kiln form, and its interior is divided into a counter-current carbonization furnace section and a co-current carbonization furnace section. The counter-current carbonization furnace section is located near the raw material inlet at the kiln tail, while the co-current carbonization furnace section is located near the carbonized material outlet at the kiln head. In the counter-current carbonization furnace section, the raw material flows downwards while the high-temperature gas flows upwards, a counter-current heating method. In the co-current carbonization furnace section, both the raw material and the high-temperature gas flow downwards, a co-current heating method. In this embodiment, the bidirectional rotary kiln 2 has a diameter of Φ1.9 × 12 m, and the high-temperature gas passage 3 extends from the kiln head into the rotary kiln. At this point, a 6-meter section near the raw material inlet at the kiln tail is designated as the counter-current carbonization furnace section, and a section near the raw material outlet at the kiln head is designated as the counter-current carbonization furnace section. The length is defined as the co-current carbonization furnace section. The kiln body of the co-current and counter-current rotary kiln 2 forms a 2° angle with the ground and rotates at a speed of 2 r / min. The raw material moves downwards under the influence of gravity during rotation, ensuring that the gas and raw material move in opposite directions in the counter-current carbonization furnace section, i.e., counter-current carbonization. The co-current and counter-current rotary kiln 2 uses high-temperature gas as the heat source for raw material carbonization. The high-temperature gas in the co-current and counter-current rotary kiln 2 is divided into two parts: one part is powered by a low-temperature gas blower 11 and flows upwards (towards the tail of the kiln) into the counter-current carbonization furnace section; the other part is powered by a circulating control pipeline system 10 and flows downwards (towards the head of the kiln) into the co-current carbonization furnace section. In the counter-current carbonization furnace section, a counter-current heating method is used where the raw material flows downwards and the high-temperature gas flows upwards; in the co-current carbonization furnace section, a co-current heating method is used where both the raw material and the high-temperature gas flow downwards.

[0057] The inlet of the high-temperature gas passage 3 is connected to the circulating control pipeline system 10, and the outlet of the high-temperature gas passage 3 is inserted into the interior of the bidirectional rotary kiln 2 and fixed inside the kiln by support rods. The high-temperature gas passage 3 serves as a heat source, and its outlet divides the kiln body of the bidirectional rotary kiln 2 into a counter-current carbonization section and a co-current carbonization section. The high-temperature gas exiting the outlet of the high-temperature gas passage 3 is divided into two flows: one part is powered by the low-temperature gas blower 11 and flows upward into the counter-current carbonization section; the other part is powered by the circulating control pipeline system 10 and flows downward into the co-current carbonization section. The high-temperature gas passage 3 is made of seamless 304 stainless steel pipe with a diameter of Φ0.6m.

[0058] The discharge cabinet 4 is located at the kiln head carbonized material outlet end of the bidirectional rotary kiln 2, and is used to separate the carbonized material from the medium-temperature fuel gas. In this embodiment, the discharge cabinet 4 is a square cabinet made of 304 stainless steel with a width of 2.5m, a height of 3m, and a thickness of 1m.

[0059] The cooling charcoal outlet 5 is located at the bottom of the discharge cabinet 4. The cooling charcoal outlet 5 is a water-cooled spiral with a diameter of Φ0.5×3m, used to cool the carbonized material to room temperature and send it out of the device for packaging, thus realizing the discharge.

[0060] The low-temperature gas passage 6 is located at the raw material inlet end of the kiln tail of the bidirectional rotary kiln 2, and collects the low-temperature gas generated in the countercurrent carbonization furnace section through a jacket. The low-temperature gas passage 6 is made of 304 stainless steel seamless steel pipe with a diameter of Φ0.5m. In the middle of the low-temperature gas passage 6, a low-temperature gas blower 11 is provided. The low-temperature gas blower 11 is a stainless steel centrifugal blower with a total pressure of 2000Pa, a flow rate of 20000m³ / h, and a temperature resistance of 300℃, which is used to provide power for the flow of low-temperature gas. The low-temperature gas blower 11 ensures that the gas direction in the countercurrent carbonization furnace section is upward and sends the low-calorific-value low-temperature gas into the two-stage combustion furnace 8.

[0061] The medium-temperature gas duct 7 is located on the discharge cabinet 4 and is used to extract the medium-temperature gas generated in the co-current carbonization furnace section. The medium-temperature gas duct 7 is made of 304 stainless steel seamless pipe with a diameter of Φ0.5m. Similarly, the raw material moves downwards under the influence of gravity and wind force, and the gas moves in the same direction as the raw material, i.e., co-current carbonization.

[0062] The two-stage combustion furnace 8 is a device for burning low-temperature and sub-high-temperature fuel gas. It can be an independent combustion unit or part of a boiler's combustion chamber. The high-temperature flue gas generated by the combustion in the two-stage combustion furnace 8 enters the high-temperature flue duct 9, and excess flue gas is sent to the waste heat recovery device 18. The two-stage combustion furnace 8 has a circular furnace body with dimensions of Φ2.2 × 8 m. The waste heat recovery device 18 is a waste heat boiler with a capacity of 6 t / h and a pressure of 1 MPa, used to recover energy from the excess flue gas of the two-stage combustion furnace 8.

[0063] The two-stage combustion furnace 8 includes two zones: a high-temperature combustion zone and a medium-temperature combustion zone. The high-temperature combustion zone of the two-stage combustion furnace 8 is connected to a sub-high-temperature gas passage 20 and a blower 16 to fully combust the sub-high-temperature gas and generate high-temperature flue gas. The blower 16 is a conventional centrifugal fan with a total pressure of 500 Pa and a flow rate of 10,000 m³ / h. The sub-high-temperature gas passage 20 is connected to a circulating control pipeline system 10 and the two-stage combustion furnace 8 to draw out the sub-high-temperature gas.

[0064] The high-temperature flue gas generated in the high-temperature combustion zone of the two-stage combustion furnace 8 enters the medium-temperature combustion zone and undergoes combustion with the low-temperature fuel gas. Combustion includes physical and chemical processes: the physical process refers to the physical mixing of the high-temperature flue gas with the water vapor contained in the low-temperature fuel gas to increase the temperature; the chemical process refers to the exothermic combustion of the combustible portion of the low-temperature fuel gas with the oxygen contained in the high-temperature flue gas.

[0065] The medium-temperature combustion zone of the two-stage combustion furnace 8 is connected to the low-temperature gas combustion channel 6 at the kiln tail. The medium-temperature combustion zone may also be equipped with an auxiliary blower 17, which is a conventional centrifugal blower with a total pressure of 500 Pa and a flow rate of 5000 m³ / h.

[0066] The auxiliary burner at the furnace head of the two-stage combustion furnace 8 is a biomass pellet burner with a power of 900,000 kcal, which provides a heat source during the ignition stage and shuts off during the energy self-supply stage. The waste heat recovery equipment 18 at the furnace tail outlet of the two-stage combustion furnace 8 is a waste heat boiler with a capacity of 6 t / h and a pressure of 1 MPa, which recovers energy from the excess flue gas of the two-stage combustion furnace 8.

[0067] The inlet end of the high-temperature flue 9 is connected to the two-stage combustion furnace 8, and the outlet end of the high-temperature flue 9 is connected to the circulating control pipeline system 10 to draw out the high-temperature flue gas. The high-temperature flue 9 is constructed of high-temperature refractory bricks and has an internal cross-sectional area of ​​0.6 × 0.6 m. The high-temperature flue 9 sends the 900°C high-temperature flue gas generated by the combustion in the two-stage combustion furnace 8 into the bidirectional rotary kiln 2. A circulating control pipeline system 10 is installed between the high-temperature flue 9 and the medium-temperature gas passage 7 to control the gas flow rate and produce 600°C high-temperature gas, which is then sent into the bidirectional rotary kiln 2 by the carbonization blower 14. The air outlet of the carbonization blower 14 is connected to the high-temperature gas passage 3 to send the high-temperature gas into the bidirectional rotary kiln 2. The carbonization blower 14 is a stainless steel centrifugal blower with a total pressure of 2000 Pa, a flow rate of 25000 m³ / h, and a temperature resistance of 700°C.

[0068] like Figure 1 and 2The circulating control pipeline system 10 has a two-inlet, two-outlet pipeline structure. It is located between the high-temperature flue duct 9 and the medium-temperature gas duct 7. The two inlets introduce high-temperature flue gas through the high-temperature flue duct 9 and medium-temperature gas through the medium-temperature gas duct 7, respectively. One outlet leads the generated sub-high-temperature gas through the sub-high-temperature gas duct 20 to the two-stage combustion furnace 8; the other outlet leads the generated high-temperature gas through the high-temperature gas duct 3 to the bidirectional rotary kiln 2. The circulating control pipeline system 10 has a ring-shaped topology, consisting of a medium-temperature semi-ring and a high-temperature semi-ring. The medium-temperature semi-ring of the circulating control pipeline system 10 includes the medium-temperature gas duct 7, a gas blower 12, a medium-temperature semi-ring valve 13, and sequentially connected pipes; the high-temperature semi-ring includes the high-temperature flue duct 9, a carbonization blower 14, a high-temperature semi-ring valve 15, and sequentially connected pipes. The high-temperature semi-ring valve 15 connects the high-temperature gas duct 3 and the medium-temperature gas duct 7. The high-temperature semi-ring and the medium-temperature semi-ring are completely symmetrical in structure and are connected end to end to form a complete annular topological pipeline structure. Specifically, the gas fan 12 and the carbonization fan 14 are symmetrical; the medium-temperature semi-ring valve 13 and the high-temperature semi-ring valve 15 are symmetrical; the medium-temperature gas passage 7 and the high-temperature flue 9 are symmetrical; and the high-temperature gas passage 3 and the sub-high-temperature gas passage 20 are symmetrical. In the medium-temperature semi-ring of the circulating control pipeline system 10, high-temperature gas and low-temperature gas are mixed to generate sub-high-temperature gas; in the high-temperature semi-ring of the circulating control pipeline system 10, high-temperature flue gas and sub-high-temperature gas are mixed; furthermore, the oxygen content in the high-temperature flue gas is consumed, and the temperature of the sub-high-temperature gas is increased, thereby forming oxygen-free high-temperature gas. The gas blower 12 is a stainless steel centrifugal blower with a total pressure of 2000 Pa, a flow rate of 30000 m³ / h, and a temperature resistance of 500℃. The gas blower 12 ensures that the gas flow direction in the co-current carbonization furnace section is downward, and sends the high-calorific-value pyrolysis gas into the circulating control pipeline system 10 through the kiln head medium-temperature gas passage 7. The carbonization blower 14 is a stainless steel centrifugal blower with a total pressure of 2000 Pa, a flow rate of 25000 m³ / h, and a temperature resistance of 700℃. Both the medium-temperature semi-circular valve 13 and the high-temperature semi-circular valve 15 are Φ0.6 high-temperature butterfly valves with a temperature resistance of 800℃, used to send excess gas back to the pipeline system for circulation, achieving gas circulation.

[0069] The working principle of the internally heated rotary carbonization furnace with bidirectional flow heating of the present invention is as follows:

[0070] Raw material feeding: The raw material is pushed into the interior of the bidirectional rotary kiln 2 through the feeder 1 and the feed screw 19. The feeder 1 is a funnel-shaped container, with a feed conveyor belt connected to the top and the feed screw 19 connected to the bottom.

[0071] Carbonization process: The raw material is carbonized in a dual-flow kiln 2, which is divided into a counter-flow carbonization section and a co-flow carbonization section. In the counter-flow carbonization section, the raw material moves downward, while the high-temperature gas flows upward through the low-temperature gas blower 11, forming a counter-flow heating method. In the co-flow carbonization section, both the raw material and the high-temperature gas move downward, forming a co-flow heating method. The high-temperature gas passage 3 serves as the heat source, and its outlet divides the kiln body into the counter-flow carbonization section and the co-flow carbonization section.

[0072] Gas circulation and control: High-temperature gas exits from the high-temperature gas duct 3 and is divided into two parts: one part enters the counter-current carbonization furnace section through the low-temperature gas blower 11, and the other part enters the co-current carbonization furnace section through the circulating control pipeline system 10. The circulating control pipeline system 10 is a two-inlet, two-outlet pipeline structure, located between the medium-temperature gas duct 7 and the high-temperature flue 9, used to control the gas flow rate and produce high-temperature gas at 600°C. The medium-temperature gas duct 7 leads out the medium-temperature gas generated in the co-current carbonization furnace section, and the secondary high-temperature gas duct 20 leads out the secondary high-temperature gas generated in the circulating control pipeline system 10 to the two-stage combustion furnace 8.

[0073] Two-stage combustion and waste heat utilization: The two-stage combustion furnace 8 includes a high-temperature combustion zone and a medium-temperature combustion zone, used to burn low-temperature and sub-high-temperature fuel gases to produce high-temperature flue gas. The high-temperature flue gas enters the high-temperature flue duct 9, part of which is sent to the bidirectional rotary kiln 2, and the excess is sent to the waste heat utilization equipment 18 for energy recovery. The waste heat utilization equipment 18 uses a waste heat boiler to recover energy from the excess flue gas of the two-stage combustion furnace 8.

[0074] Discharge and cooling: The carbonized material is separated from the medium-temperature gas in the discharge cabinet 4, and then cooled to room temperature by the cooling carbon discharger 5, and then sent out of the device for packaging.

[0075] System control and auxiliary equipment: The carbonization blower 14 delivers high-temperature fuel gas into the bidirectional rotary kiln 2 and regulates the gas flow rate via the high-temperature semi-annular valve 15. The gas blower 12 ensures the gas flow direction in the co-current carbonization section is downward and regulates the gas flow rate via the medium-temperature semi-annular valve 13. The auxiliary blower 17 provides additional airflow in the medium-temperature combustion zone of the two-stage combustion furnace 8. The auxiliary burner at the furnace head of the two-stage combustion furnace 8 provides a heat source during the ignition phase and shuts off during the energy self-sufficiency phase.

[0076] The internal heating rotary carbonization furnace of the present invention, which uses bidirectional flow heating, achieves a high-efficiency and energy-saving carbonization process by combining bidirectional flow heating with precise control of the gas through a circulating control pipeline system 10. It also recovers energy from excess flue gas through a waste heat utilization device 18, thereby improving the overall energy utilization efficiency.

[0077] The process control method, in conjunction with the embodiments of the present invention, will be further described in detail, including the following steps:

[0078] Step 1, Ignition: Use a biomass pellet burner with a power of 900,000 kcal to heat the high-temperature combustion zone of the two-stage combustion furnace 8, so that the high-temperature combustion zone is heated to 900℃.

[0079] Step 2, heating: The carbonization fan 14 of the circulating control pipeline system 10 draws the 900°C high-temperature flue gas into the high-temperature gas duct 3 to heat the forward and reverse flow kiln 2; the temperature of the cooled high-temperature flue gas is 250°C, which is drawn out to the medium-temperature combustion zone by the low-temperature gas fan 11, and then sent to the waste heat utilization equipment 18 through the outlet of the combustion furnace before being discharged.

[0080] Step 3, Feeding and Carbonization: When the average temperature inside the bidirectional rotary kiln 2 reaches 400℃, feeding is carried out. The raw material is pushed into the bidirectional rotary kiln 2 using the feeder 1; the raw material undergoes a cracking reaction inside the kiln, generating fuel gas, and then 150℃ low-temperature fuel gas is drawn out using the low-temperature fuel gas channel 6; 300℃ medium-temperature fuel gas is drawn out using the medium-temperature fuel gas channel 7.

[0081] Step 4, Gas ring formation: In the circulating control pipeline system 10, the 400°C sub-high temperature gas flows sequentially through the gas blower 12 and the medium temperature semi-circular valve 13; after being heated to 600°C by the high temperature gas, it flows through the carbonization blower 14 and the high temperature semi-circular valve 15, and after being cooled to 400°C by the sub-high temperature gas, it returns to the gas blower 12, forming a circulating flow of gas, i.e., a gas ring;

[0082] Step 5, two-stage combustion: 400°C sub-high temperature gas is drawn from the circulating control pipeline system 10 to provide fuel for the high temperature combustion zone of the two-stage combustion furnace 8, forming 900°C high temperature flue gas; 150°C low temperature gas enters the medium temperature combustion zone through the low temperature gas passage 6 to realize the combustion and calcination of low calorific value cracked gas, and the flue gas temperature of combustion and calcination is 750°C.

[0083] Step 6, self-sufficiency of energy: The high-temperature flue gas generated by the two-stage combustion furnace 8 provides carbonization energy for the forward and reverse flow rotary kiln 2; at this time, the biomass pellet burner is turned off, and the energy self-sufficiency is achieved entirely by using gas; the excess flue gas is sent to the waste heat utilization equipment 18, which can generate 3t / s, 1Mpa high-pressure steam, to achieve efficient energy utilization.

[0084] Step 7, Carbonization Temperature Control: In the circulating control pipeline system 10, if the actual temperature of the high-temperature gas is lower than 600℃, it will result in insufficient carbonization. At this time, reducing the opening of the medium-temperature semi-ring valve 13 increases the outflow of the secondary high-temperature gas in the gas ring, and the inflow of the secondary high-temperature flue gas in the gas ring also increases accordingly; this control will cause the temperature of the high-temperature gas to rise slowly to increase the carbonization temperature; and vice versa.

[0085] Step 8, Gas Flow Regulation: Within the circulating control pipeline system 10, if the temperature of the high-temperature flue gas is below 700℃, it indicates insufficient gas flow, which could lead to the risk of combustion furnace flameout. In this case, reducing the opening of the high-temperature semi-ring valve 15 increases the inflow of medium-temperature gas into the gas ring, and correspondingly increases the outflow of sub-high-temperature gas from the gas ring, thereby increasing the gas flow. This regulation will further effectively improve the condition of the high-temperature combustion zone and increase the combustion furnace temperature; conversely, the opposite is also true.

[0086] The above embodiments are merely preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. An internally heated rotary carbonization furnace with bidirectional flow heating, characterized in that: It includes a feeder (1), a forward and reverse flow rotary kiln (2), a high-temperature gas duct (3), a discharge cabinet (4), a cooling charcoal outlet (5), a low-temperature gas duct (6), a medium-temperature gas duct (7), a two-stage combustion furnace (8), a high-temperature flue (9), and a circulating control pipeline system (10); The feeder (1) is located at the raw material inlet end of the kiln tail of the bidirectional rotary kiln (2) and is used to push the raw material into the interior of the bidirectional rotary kiln (2). The forward and reverse flow rotary kiln (2) adopts the form of a rotary kiln. The kiln body is divided into a counter-current carbonization furnace section and a forward-current carbonization furnace section. The section near the raw material inlet end of the kiln tail is the counter-current carbonization furnace section, and the section near the carbonized material outlet end of the kiln head is the forward-current carbonization furnace section. The inlet of the high-temperature gas passage (3) is connected to the circulating control pipeline system (10), and the outlet of the high-temperature gas passage (3) is inserted into the interior of the forward and reverse flow kiln (2). The discharge cabinet (4) is located at the kiln head carbonized material outlet end of the forward and reverse flow kiln (2) and is used to separate the carbonized material from the medium-temperature gas. The cooling charcoal outlet (5) is located at the bottom of the discharge cabinet (4) and is used to cool the carbonized material and send it out of the device for packaging. The low-temperature gas passage (6) is located at the raw material inlet end of the kiln tail of the forward and reverse flow kiln (2), and collects the low-temperature gas generated by the counter-current carbonization furnace section through the jacket; a low-temperature gas fan (11) is installed in the middle of the low-temperature gas passage (6) to provide power for the flow of low-temperature gas. The medium-temperature gas passage (7) is located on the discharge cabinet to draw out the medium-temperature gas generated in the co-current carbonization furnace section; The two-stage combustion furnace (8) is a device for burning low-temperature gas and sub-high-temperature gas. It adopts independent combustion equipment or the combustion furnace of a boiler. The high-temperature flue gas generated by combustion enters the high-temperature flue (9), and the excess flue gas is sent to the waste heat utilization equipment (18). The inlet end of the high-temperature flue (9) is connected to a two-stage combustion furnace (8), and the outlet end is connected to a circulating control pipeline system (10) to draw out the high-temperature flue gas. The circulating control pipeline system (10) is a two-inlet and two-outlet pipeline structure. High-temperature flue gas is introduced through the high-temperature flue (9) and medium-temperature gas is introduced through the medium-temperature gas duct (7). The generated secondary high-temperature gas is led out through the secondary high-temperature gas duct (20) into the two-stage combustion furnace (8). The generated high-temperature gas is led out through the high-temperature gas duct (3) into the forward and reverse flow kiln (2). The circulating control pipeline system (10) consists of a medium-temperature semi-ring and a high-temperature semi-ring. The medium-temperature semi-ring includes a medium-temperature gas duct (7), a gas blower (12), a medium-temperature semi-ring valve (13), and pipelines connected in sequence. The high-temperature semi-ring includes a high-temperature flue (9), a carbonization blower (14), a high-temperature semi-ring valve (15), and pipelines connected in sequence. The high-temperature semi-ring and the medium-temperature semi-ring are completely symmetrical in structure and are connected end to end to form a complete ring topology pipeline structure. Among them, the gas blower (12) and the carbonization blower (14) are symmetrical; the medium-temperature semi-ring valve (13) and the high-temperature semi-ring valve (15) are symmetrical; the medium-temperature gas duct (7) and the high-temperature flue (9) are symmetrical; and the high-temperature gas duct (3) and the sub-high-temperature gas duct (20) are symmetrical.

2. The internally heated rotary carbonization furnace with bidirectional flow heating as described in claim 1, characterized in that: The bidirectional rotary kiln (2) uses high-temperature gas as the heat source for carbonization of raw materials. The high-temperature gas in the bidirectional rotary kiln (2) is divided into two parts. One part is powered by a low-temperature gas blower (11) and flows upward into the countercurrent carbonization furnace section. The other part is powered by a circulating control pipeline system (10) and flows downward into the co-current carbonization furnace section. In the countercurrent carbonization furnace section, the raw materials flow downward and the high-temperature gas flows upward in a countercurrent heating method. In the co-current carbonization furnace section, the raw materials and high-temperature gas both flow downward in a co-current heating method.

3. The internally heated rotary carbonization furnace with bidirectional flow heating as described in claim 1, characterized in that: The two-stage combustion furnace (8) is provided with two zones, one is a high-temperature combustion zone and the other is a medium-temperature combustion zone; the high-temperature combustion zone is connected to a secondary high-temperature gas duct (20) and a blower (16) for fully burning the secondary high-temperature gas to generate high-temperature flue gas; the medium-temperature combustion zone is connected to a low-temperature gas duct (6) at the kiln tail; the high-temperature flue gas enters the medium-temperature combustion zone and undergoes combustion with the low-temperature gas; the combustion includes two processes, one is a physical process, which refers to the physical mixing of the high-temperature flue gas with the water vapor contained in the low-temperature gas to increase the temperature; the other is a chemical process, which refers to the combustion heat release of the combustible part contained in the low-temperature gas combined with the oxygen contained in the high-temperature flue gas.

4. The internally heated rotary carbonization furnace with bidirectional flow heating as described in claim 1, characterized in that: In the medium-temperature semi-ring of the circulating control pipeline system (10), high-temperature gas and low-temperature gas are mixed to generate sub-high-temperature gas; in the high-temperature semi-ring of the circulating control pipeline system (10), high-temperature flue gas and sub-high-temperature gas are mixed; the oxygen content in the high-temperature flue gas is consumed, and the temperature of the sub-high-temperature gas is increased, thereby forming oxygen-free high-temperature gas.

5. The internally heated rotary carbonization furnace with bidirectional flow heating as described in claim 1, characterized in that: The temperature of the low-temperature gas is between 100 and 250°C; the temperature of the medium-temperature gas is between 200 and 300°C; the temperature of the sub-high-temperature gas is between 300 and 500°C; the temperature of the high-temperature gas is above 400°C; and the temperature of the high-temperature flue gas is above 700°C.

6. A process control method for an internally heated rotary carbonization furnace with bidirectional flow heating as described in claim 1, characterized in that... Includes the following steps: Step 1, Ignition: The high-temperature combustion zone of the two-stage combustion furnace (8) is heated by an auxiliary burner; the auxiliary burner can be a biomass pellet burner, a natural gas burner, a wood-burning stove or an electric stove; Step 2, heating: The high-temperature flue gas is drawn out to the high-temperature gas duct (3) by the carbonization fan (14) of the circulating control pipeline system (10) to heat the forward and reverse flow kiln (2); the cooled high-temperature flue gas is drawn out to the medium-temperature combustion zone by the low-temperature gas fan (11), and then sent to the waste heat utilization equipment (18) through the outlet of the two-stage combustion furnace before being discharged; Step 3, feeding and carbonization: The raw materials are pushed into the interior of the forward and reverse flow rotary kiln (2) using the feeder (1); low-temperature gas is drawn out using the low-temperature gas channel (6); and medium-temperature gas is drawn out using the medium-temperature gas channel (7). Step 4, Gas ring formation: In the circulating control pipeline system (10), the secondary high temperature gas flows through the gas blower (12) and the medium temperature semi-circular valve (13) in sequence; after being heated to high temperature gas, it flows through the carbonization blower (14) and the high temperature semi-circular valve (15), and after being cooled to secondary high temperature gas, it returns to the gas blower (12), thus forming a circulating flow of gas, i.e., a gas ring; Step 5, two-stage combustion: The sub-high temperature gas drawn from the circulating control pipeline system (10) provides fuel for the high temperature combustion zone of the two-stage combustion furnace (8) to form high temperature flue gas and ensure the stability of the combustion furnace; the low temperature gas enters the medium temperature combustion zone through the low temperature gas passage (6) to realize the combustion of low calorific value cracked gas; Step 6, self-supplied energy: The high-temperature flue gas generated by the two-stage combustion furnace (8) provides carbonization energy to the forward and reverse flow rotary kiln (2), and then the auxiliary burner is turned off to achieve self-supplied energy; the excess flue gas is sent to the waste heat utilization equipment (18) to achieve efficient energy utilization. Step 7, Control of carbonization temperature: In the circulating control pipeline system (10), reducing the opening of the medium temperature semi-ring valve (13) will increase the outflow of the secondary high temperature gas in the gas ring. At the same time, according to the characteristics of the ring, the inflow of high temperature flue gas in the gas ring will also increase accordingly, thereby increasing the high temperature gas temperature and increasing the carbonization temperature; the opposite is also true. Step 8, Gas flow regulation: In the circulating regulation pipeline system (10), reducing the opening of the high temperature semi-ring valve (15) will increase the inflow of medium temperature gas in the gas ring. At the same time, according to the characteristics of the ring, the outflow of high temperature gas in the gas ring will also increase accordingly, thereby achieving the effect of increasing the gas flow; the opposite is also true.

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