Biomass side entry pyrolysis recovery system and method based on slag sensible heat driving

Abstract

The application discloses a biomass side-in pyrolysis recycling system and method based on visible heat of molten slag, and the system comprises a separated feeding system, a light-pipe refractory lining rotary reaction kettle, a solid phase grading collection and waste heat feedback system and a gas-liquid multistage purification and recycling system.The separated feeding system realizes non-contact feeding of high-temperature molten slag and biomass, and prevents early combustion and coking at the feeding throat; the light-pipe refractory lining rotary reaction kettle is free of metal components in the interior, and solves the problems of high cost of traditional electric heating and short service life of metal components; the solid phase grading collection and waste heat feedback system realizes hot-state screening and recycling of waste heat of molten slag for raw material pre-drying; and the gas-liquid multistage purification and recycling system realizes high-value separation of heavy tar, light bio-oil and non-condensable combustible gas through gradient condensation.The application solves the problems of short service life of the prior art equipment, easy blocking of feeding and low product recycling quality, and realizes deep utilization of waste heat of molten slag and efficient conversion of biomass.

Description

Technical Field

[0001] This invention belongs to the field of coupling technology of comprehensive utilization of secondary resources in non-ferrous metallurgy and conversion of biomass into renewable energy. It utilizes the sensible heat of high-temperature slag from non-ferrous metallurgy such as copper, lead, and zinc as a heat carrier to drive biomass to undergo anaerobic pyrolysis and realize online separation and high-value recycling of gaseous, liquid, and solid three-phase products. Specifically, it relates to a biomass side-entry pyrolysis recovery system and method based on sensible heat driven by slag. Background Technology

[0003] Pyrolysis technology is a core means of biomass energy conversion and utilization, capable of transforming biomass into high-value-added biochar, bio-oil, and syngas. However, traditional pyrolysis and gasification processes typically rely on coal, gas, or oil for external heat sources, leading to severe environmental pollution and low economic efficiency, thus limiting their large-scale application. This dependence on fossil fuels not only increases operating costs but also weakens the overall carbon emission reduction benefits of bioenergy production.

[0004] Therefore, coupling high-temperature slag from non-ferrous metallurgical waste as a direct heat carrier with the biomass pyrolysis process, utilizing the waste heat of the slag to drive the biomass pyrolysis reaction, constructs an ideal industrial model of waste-to-waste and zero-energy pyrolysis, theoretically possessing enormous potential for energy conservation and emission reduction. However, in the engineering process, existing technologies and equipment have encountered the following core bottlenecks:

[0005] First, the core reaction equipment has a short lifespan: Traditional rotary kilns rely on internal metal fins or stirring shafts to solve the problem of slag mixing. However, under the continuous scouring and high abrasion of molten slag at temperatures above 1000°C, these metal components are prone to softening, deformation, or even breakage and detachment, resulting in extremely short equipment lifespan and high maintenance costs.

[0006] Secondly, the feeding process is prone to coking and blockage: the simple premixed feeding method can easily induce premature combustion and coking blockage of biomass at the feed throat, which poses a major safety hazard and seriously affects the continuous and stable operation of the system.

[0007] Third, the quality of recovered products is low: the extensive recovery process results in poor quality biochar due to the adsorption of impurities, mixed bio-oil components and low utilization value, and there is a lack of cascade recovery methods for medium and low temperature waste heat, resulting in insufficient energy utilization.

[0008] In summary, overcoming the technical barriers of equipment lifespan, feed safety, and high-value recovery of all components, and developing a novel coupling system that is structurally robust, safe in operation, and capable of multi-stage energy utilization, has become the key to promoting the industrialization of slag-coupled biomass pyrolysis technology.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a biomass side-entry pyrolysis recovery system and method based on slag sensible heat drive. Through the integration of a bare tube refractory system and spatiotemporally decoupled feeding technology, the system achieves long-term stable operation and high-value cascade recovery of all components. This system aims to solve common technical problems in existing slag-coupled pyrolysis processes, such as short lifespan of core reaction equipment, easy coking and blockage of mixed feed, and low product recovery quality.

[0011] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0012] A biomass side-entry pyrolysis recovery system based on sensible heat of molten slag is provided. Its main equipment is connected sequentially along the material flow direction, including a separate feeding system, a bare tube refractory-lined rotary reactor system, a solid phase classification collection and waste heat feedback system, and a gas-liquid multi-stage purification and recovery system.

[0013] The separate feeding system is located at the kiln head end of the rotary reactor and employs a spatially decoupled feeding structure combining refractory sliding and cantilever direct injection. This system physically separates the high-temperature molten slag heat carrier and biomass feedstock, feeding them separately into the reactor. Specifically, it includes a high-temperature molten slag receiving hopper at the top and a biomass feed hopper arranged to the side. The bottom outlet of the high-temperature molten slag receiving hopper is connected to a refractory gravity sliding chute. This chute is lined with high-temperature ceramic and is arranged at a large angle. Its discharge end passes through the kiln head sealing cover and extends obliquely into the refractory lining at the bottom of the reactor, using gravity to guide the molten slag into the reactor. The biomass feed hopper is connected to a cantilevered direct injection screw conveyor. This conveyor extends axially into the reactor in a horizontal cantilever shape, with its discharge port extending behind or above the drop point of the refractory gravity sliding chute. This ensures that the biomass, after leaving the conveyor, falls directly onto the already formed high-temperature slag bed, thus physically avoiding premature contact between the two in the narrow feeding channel.

[0014] The high-temperature molten slag receiving hopper sits on an independent steel structure support. Its inner wall is filled with wear-resistant refractory castable with a thickness of not less than 100mm. The bottom outlet is airtightly connected to a refractory gravity sliding chute via a flange. The core of this chute is a high-purity silicon carbide ceramic inner cylinder, wrapped with a steel shell and filled with insulation cotton. The entire chute passes through the composite dynamic and static sealing components at a large angle of 35° to 45° with the horizontal plane, cutting obliquely into the kettle to ensure that the high-viscosity molten slag can slide smoothly by gravity. The biomass feed silo is placed next to the kiln head platform. The cantilevered direct-injection screw conveyor connected to its bottom adopts a double-layer water-cooled jacket structure to resist high-temperature radiation. The screw blades are made of 310S heat-resistant stainless steel and designed with a variable pitch anti-clogging structure. The conveyor extends horizontally into the vessel by 1-2 meters along the axial direction, and its discharge nozzle extends precisely to the area above and behind the material drop point of the chute. This ensures that the biomass particles, after leaving the screw, can directly cover the surface of the formed high-temperature molten slag fluid in a parabolic shape, thus completely eliminating throat contact.

[0015] The tube-type refractory-lined rotary reactor system is connected to the separate feeding system and serves as the core reaction site. The main body of the reactor is a tube structure without internal metal components, and its inner wall is lined with wear-resistant refractory bricks or castable lining to withstand the direct abrasion of high-temperature molten slag. The main drive gear ring is fitted on the outside of the reactor, which drives the reactor to rotate at low speed through a variable frequency drive unit. The mechanical friction and gravity generated by the rotation of the cylinder drive the molten slag and biomass particles at the bottom to tumble, shear, and mix. The sensible heat released by the high-temperature molten slag drives the biomass to undergo an autothermal pyrolysis reaction. The feed end of the reactor is equipped with an inert gas protection interface for introducing nitrogen into the system to maintain a positive pressure anaerobic environment.

[0016] The cylindrical body of the refractory-lined rotary reactor is made of Q345R boiler steel plate. The inner wall is lined with a double-layer staggered refractory lining. The wall-adhering layer is made of lightweight insulating bricks, and the working layer is made of 180mm thick high-alumina bricks or magnesia-chrome bricks, forming a smooth cylindrical reaction chamber without any metal lifting components to withstand the chemical erosion and mechanical wear of molten slag at 1250℃. Flexible dynamic and static sealing devices are installed at both ends of the reactor body to effectively prevent air ingress or gas leakage. A main drive gear ring is installed on the outside of the reactor body via a spring plate, meshing with the pinion of a variable frequency drive unit. The drive system is equipped with an auxiliary motor and a slow-rotation device, enabling precise stepless speed regulation within the range of 0.5-5 r / min to control the reaction residence time of materials in the high-temperature zone.

[0017] The solid-phase classification and waste heat feedback system is sealed and connected to the discharge end of the reactor, constructing a purification and recovery system that utilizes the difference in component condensation temperature for graded separation. This system is used to achieve hot separation of pyrolysis solid products and graded utilization of waste heat. It includes a built-in hot-phase classification drum screen that rotates synchronously with the reactor body. This drum screen is coaxially fixed at the tail end of the reactor body. Utilizing the particle size difference between biochar and slag, fine powdered biochar is screened into the biochar collection hopper below for collection, avoiding secondary adsorption pollution caused by cold screening. The slag discharged from the tail end of the drum screen directly enters the counter-current waste heat utilization heat exchanger, where it exchanges heat with the counter-current incoming cold air. The cooled slag is discharged and recovered, while the heated hot air is transported through a return pipe to the biomass feed silo or the front end of the feed system for pre-drying of the raw materials.

[0018] The built-in hot-state grading drum screen is coaxially welded to the tail of the reactor via a heat-resistant steel support, rotating synchronously with the reactor body. The drum screen mesh is made of high-temperature resistant alloy steel woven mesh with an aperture of 3-5mm, and is covered by a fully enclosed heat-insulating dust collection hood. The outlet for fine particles under the screen is directly connected to the biochar collection hopper, with a star-shaped discharge valve at the bottom to isolate airflow; the outlet for large particles over the screen is connected to a counter-current slag sensible heat utilization heat exchanger via a high-temperature chute. This heat exchanger has a cold air distribution plate at the bottom and a hot air collection hood at the top, and is equipped with a material level gauge and temperature sensor inside, forming a slag-gas counter-current heat exchange channel to ensure that the slag discharge temperature is below 100℃ while generating high-quality hot air.

[0019] The gas-liquid multi-stage purification and recovery system is connected to the gas phase outlet of the solid-phase staged collection system, constructing a tiered fractionation and recovery system based on component dew point differences for the tiered purification and fractionation recovery of pyrolysis gas phase products. It consists of a high-temperature cyclone dust collector, a heavy component spray quench tower, and a light component tubular condenser connected in series along the gas flow direction. The pyrolysis gas first passes through the high-temperature cyclone dust collector to remove entrained fine carbon powder and dust; then it enters the heavy component spray quench tower, where the temperature of the spray liquid is controlled by a matching circulating medium cooler, preferentially condensing and collecting the high-boiling-point heavy tar components; the uncondensed gas flow continues into the light component tubular condenser, where light bio-oil is condensed and precipitated under low-temperature conditions, ultimately separating clean, non-condensable combustible gas.

[0020] Regarding the gas phase pipeline connection and multi-stage recovery, the gas outlet at the top of the kiln tail transition sealing assembly is connected via a flange to a section of insulated pipe covered with aluminum silicate fiber cotton. This pipe is connected to the tangential inlet of the high-temperature cyclone dust collector to prevent premature condensation and coking of the high-temperature oil and gas on the pipe wall due to temperature drop during transportation. The clean pyrolysis gas after dust removal enters the heavy component spray quench tower. The tower is equipped with acid-resistant ceramic structured packing, and an independent heavy oil circulation condensation loop consisting of a circulating pump and a circulating medium cooler is installed outside the tower to precisely control the spray liquid temperature at 130-150℃. High-boiling-point heavy tar is preferentially captured by countercurrent oil washing gas. The uncondensed light component gas is discharged from the top of the tower and enters the light component tube-type condenser. Under the action of circulating cooling water in the tube side, it is rapidly cooled to 30-40℃, thereby completely condensing and precipitating light organic components such as phenols and ketones, as well as water vapor, ultimately achieving online stepwise separation of heavy oil, light oil, and clean non-condensable combustible gas.

[0021] The specific process flow is as follows:

[0022] 1. Start-up and Feeding Stage: Before system startup, nitrogen is introduced into the system through the inert gas protection interface until the oxygen content is below 1%. The variable frequency drive unit is adjusted to rotate the bare tube refractory-lined rotary reactor at a low speed of 2 r / min. 1250℃ high-temperature molten slag from the smelting furnace is poured into the high-temperature molten slag receiving hopper and continuously slids into the reactor through a refractory gravity sliding chute, forming a stable high-temperature heat carrier bed. Simultaneously, biomass is pumped out from the biomass feed hopper and enters the reactor via a cantilevered direct-injection screw conveyor.

[0023] 2. Self-heating pyrolysis and reaction stage: Inside the reactor, biomass particles fall directly onto the surface of molten slag at temperatures above 1000℃, absorbing heat and undergoing drying and pyrolysis. Due to the continuous rotation of the reactor, the molten slag and biomass are carried up and tumbled together by the rotation of the inner wall of the tube, constantly renewing the heat transfer interface. The volatiles produced by the reaction rapidly overflow, and the biomass gradually transforms into biochar. The temperature of the molten slag gradually decreases to 600-700℃ as the reaction proceeds. During this process, the molten slag gradually transforms from a molten state into solid particles, avoiding wall adhesion.

[0024] 3. Solid-phase separation and waste heat feedback: The solid mixture after the reaction moves to the tail end of the reactor and enters a built-in hot-state classifying drum screen. Biochar powder with a particle size of less than 3 mm passes through the screen holes and falls into the biochar collection hopper, is discharged through the discharge valve, and is cooled in the absence of air to obtain a high-porosity biochar product. Cooled copper slag particles with a particle size of more than 5 mm are discharged from the screen and enter a counter-current slag sensible heat utilization heat exchanger to exchange heat with the counter-current ambient cold air. The slag is cooled to below 100°C and discharged for storage, while the cold air is heated to 180-220°C to form clean hot air. This hot air is drawn to the front end by an induced draft fan for the pre-drying of pine sawdust raw materials, completing the energy closed loop.

[0025] 4. Gas-Liquid Stage Purification and Recovery: The pyrolysis mixture, at approximately 500-600℃, exits from the kiln tail and first passes through a high-temperature cyclone dust collector to remove entrained carbon dust. It then enters a heavy component spray quench tower, where the spray liquid temperature is precisely controlled at 150-180℃ by a circulating medium cooler. This causes the higher-boiling-point heavy tar components in the mixture to preferentially condense and precipitate, collected from the bottom of the tower as heavy oil. The uncondensed light component gas enters a light component tubular condenser, where it condenses into reddish-brown light bio-oil under the action of cooling water at 30-40℃. The finally separated non-condensable combustible gas, with a calorific value of approximately 12-15 MJ / Nm³, is purified and sent to a gas storage tank or directly reused for heating in the smelter.

[0026] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0027] (1) The lifespan of core equipment has been significantly extended.

[0028] It abandons the metal lifting components inside the traditional rotary kiln that are prone to high-temperature failure, and adopts a bare tube refractory lining structure. It relies entirely on the rotation of the kettle to achieve slag mixing, which eliminates the risk of softening and breaking of metal components in the molten slag environment of thousands of degrees from the root, and extends the continuous operation cycle of the equipment from several weeks to more than half a year.

[0029] (2) Feeding safety and system stability are greatly improved

[0030] The space-decoupled feeding structure of "refractory sliding chute + cantilever direct injection spiral" is adopted, which forcibly isolates the high-temperature molten slag and biomass in physical space, completely eliminating pre-combustion and coking blockage at the feed throat. Combined with inert gas protection, it achieves inherently safe long-term continuous operation.

[0031] (3) Energy is utilized in a cascade manner, resulting in high system energy efficiency.

[0032] A closed-loop energy utilization system of "high-temperature driven pyrolysis and medium-temperature feedback drying" has been constructed: the sensible heat of molten slag at 1250℃ is used to drive the zero-energy pyrolysis of biomass, and the waste heat of molten slag at 600℃ is recovered through a heat exchanger to generate hot air for pre-drying of raw materials. The comprehensive recovery rate of sensible heat of molten slag is over 85%.

[0033] (4) Full-component graded recycling results in high product added value.

[0034] This innovative approach transforms the traditional pyrolysis process from a crude recovery model characterized by "mixed slag and biochar, and indiscriminate oil and gas separation" to a refined, graded recovery system integrating "hot screening + gas-phase stepped condensation." Hot screening separates biochar from molten slag at high temperatures, preventing adsorption and contamination of the biochar and producing high-porosity biochar. Gas-phase stepped condensation (150℃ rapid cooling + 35℃ condensation) separates heavy tar, light bio-oil, and clean combustible gas in a single step, eliminating the need for subsequent upgrading processes and significantly enhancing the overall value of the products.

[0035] (5) Collaborative treatment, combining environmental protection and economic benefits

[0036] It has achieved cross-industry collaboration between the deep utilization of waste heat in non-ferrous metallurgy and the efficient conversion of biomass energy, avoiding water resource consumption and secondary pollution in the water quenching process.

[0037] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0038] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0039] Figure 1 This is a schematic diagram of the structural connection of the present invention.

[0040] In the diagram: 1-High-temperature molten slag receiving hopper; 2-Biomass feed silo; 3-Refractory gravity sliding chute; 4-Cantilever direct injection screw conveyor; 5-Inert gas protection interface; 6-Kiln head composite dynamic and static sealing assembly; 7-Smooth tube refractory-lined rotary reactor; 8-Main drive gear ring; 9-Variable frequency drive unit; 10-Kiln tail transition sealing assembly; 11-Built-in hot-state grading drum screen; 12-Biochar collection hopper; 13-Counterflow molten slag sensible heat utilization heat exchanger; 14-High-temperature cyclone dust collector; 15-Heavy component spray quench tower; 16-Circulating medium cooler; 17-Light component shell and tube condenser.

[0041] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0043] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0044] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] Example 1

[0046] This embodiment provides a biomass side-entry pyrolysis recovery system driven by sensible heat of molten slag. The main equipment is connected sequentially along the material flow direction, and the overall structure is as follows: Figure 1 As shown.

[0047] I. System Composition

[0048] 1. Separate feeding system

[0049] The separate feeding system is located at the kiln head end of the reactor and includes a high-temperature slag receiving hopper 1, a biomass feeding silo 2, a refractory gravity sliding chute 3, and a cantilevered direct injection screw conveyor 4.

[0050] The high-temperature molten slag receiving hopper 1 is mounted on an independent steel structure support. Its inner wall is filled with 120mm thick wear-resistant refractory castable to receive 1250℃ high-temperature molten slag from a copper smelting flash furnace. The bottom outlet of the receiving hopper is airtightly connected to the refractory gravity sliding chute 3 via a flange.

[0051] The core of the refractory gravity sliding chute 3 is a high-purity silicon carbide ceramic inner cylinder with an inner diameter of 300mm, wrapped with a 10mm thick steel shell and filled with 80mm thick aluminum silicate fiber insulation cotton. The chute is inclined at a 40° angle to the horizontal plane, passes through the kiln head composite dynamic and static sealing component 6, and is obliquely cut into the tube-type refractory-lined rotary reactor 7. Its outlet end extends to about 1.5m inside the reactor from the feed end, and the lower edge of the outlet is about 200mm from the bottom refractory lining surface inside the reactor, ensuring that the high-temperature molten slag can smoothly slide into the reactor by gravity to form a stable high-temperature heat carrier bed.

[0052] The biomass feed silo 2 is located next to the kiln head platform, with a volume of 10m³. The silo is equipped with an arch-breaking device to prevent pine sawdust (particle size ≤10mm, moisture content 15%) from bridging. The bottom outlet of the silo is connected to a cantilevered direct-injection screw conveyor 4.

[0053] The cantilevered direct-injection screw conveyor 4 employs a double-layer water-cooled jacket structure to resist high-temperature radiation, with circulating cooling water flowing through the jacket. The screw blades are made of 310S heat-resistant stainless steel and designed with a variable pitch structure (larger pitch at the feed end and smaller pitch at the discharge end) to prevent clogging. The conveyor extends horizontally cantilevered into the reactor axially for 2.0m, and its discharge nozzle precisely extends approximately 0.8m behind and above the material drop point of the refractory gravity sliding chute 3. This ensures that after the pine sawdust particles leave the screw, they fall directly in a parabolic trajectory to cover the surface of the already formed high-temperature molten slag fluid, achieving direct contact and mixing of biomass and molten slag within the reactor. This completely eliminates premature contact between the two phases at the feed throat from a physical perspective.

[0054] 2. Smooth-tube refractory-lined rotary reactor

[0055] The cylindrical body of the bare-tube refractory-lined rotary reactor 7 is rolled and welded from Q345R boiler steel plate, with dimensions of φ2000×20000mm. The inner wall is lined with a double-layer staggered masonry process: the wall-adhering layer is 115mm thick lightweight mullite insulating brick (thermal conductivity 0.3 W / m·K), and the working layer is 180mm thick high-alumina brick (Al2O3 content ≥75%), forming a smooth cylindrical reaction chamber with an inner diameter of approximately 1410mm. The reactor's inner wall contains no metal lifting plates, stirring fins, or other components; it relies entirely on the mechanical friction and gravity generated during the reactor's rotation to tumble, shear, and mix the molten slag and biomass particles at the bottom.

[0056] The inlet end of the reactor body is equipped with a kiln head composite dynamic and static sealing assembly 6, and the outlet end is equipped with a kiln tail transition sealing assembly 10. Both are flexible graphite block sealing structures, effectively preventing air infiltration or gas leakage. The kiln head sealing cover at the inlet end is equipped with an inert gas protection interface 5 with a pipe diameter of DN50. It is connected to a nitrogen source through a pipeline to introduce nitrogen into the reactor during system startup, operation, and shutdown to maintain a positive pressure (50-200 Pa) anaerobic environment (oxygen content <1%).

[0057] The main drive gear ring 8 is mounted on the outside of the reactor body via a spring plate, meshing with the output pinion of the variable frequency drive unit 9. The variable frequency drive unit 9 has a power of 45kW and is equipped with an auxiliary motor and a slow-rotation device, which can achieve stepless speed regulation within the range of 0.5-5 r / min to precisely control the reaction residence time of the material in the high-temperature zone (design residence time 30-60 min).

[0058] 3. Solid phase fractionation collection and waste heat feedback system

[0059] At the discharge end of the reactor, a built-in hot-state grading drum screen 11 is coaxially fixed to the tail of the reactor body via a heat-resistant steel (ZG40Cr25Ni20) bracket, rotating synchronously with the reactor body. The drum screen mesh is made of high-temperature resistant alloy steel (06Cr25Ni20) woven mesh with circular holes and a diameter of 5mm. The screen is covered by a fully enclosed heat-insulating dust collection hood, lined with aluminum silicate fiber cotton, to maintain the temperature of the screening area (approximately 500-600℃) and prevent biochar from adsorbing tar due to temperature drop.

[0060] The outlet for fine particles (particle size < 5mm) is directly connected to the biochar collection hopper 12 below. The biochar collection hopper 12 is a water-cooled jacketed structure, with a star-shaped discharge valve (φ300mm) at the bottom to continuously discharge biochar and isolate airflow to prevent air intake. The discharged biochar is approximately 150℃, and after being further cooled to below 40℃ by a closed spiral cooling conveyor, it is sent to the finished product silo.

[0061] The large particles (≥5mm in diameter) exiting the sieve are connected to a counter-current slag sensible heat exchanger 13 via a high-temperature resistant chute. This heat exchanger is a vertical structure with a shell diameter of 1200mm and a height of 6000mm, lined with wear-resistant castable. The bottom of the heat exchanger has a cold air distribution plate and a cold air inlet (connected to a blower, airflow 3000 m³ / h), while the top has a hot air collection hood and a hot air outlet. Internally, a material level gauge and a temperature sensor are installed, forming a slag-gas counter-current heat exchange channel. Approximately 600℃ cooled slag particles enter the heat exchanger from the top, slowly descend, and counter-currently contact and exchange heat with the ambient cold air (20℃) blown in from the bottom. After heat exchange, the temperature of the molten slag drops below 80°C and is discharged through the bottom discharge valve for storage or sale. The cold air is heated to 200-220°C to form clean hot air, which is sent back to the jacket of the biomass feed silo 2 or the front-end raw material drying system by the induced draft fan through the insulated pipe for pre-drying of pine wood chips, reducing the moisture content of the raw material from 15% to below 8%, thus completing the energy closed loop.

[0062] 4. Multi-stage gas-liquid purification and recovery system

[0063] The air outlet at the top of the kiln tail transition sealing assembly 10 is connected to an insulated pipe (300mm diameter) covered with 100mm thick aluminum silicate fiber cotton via a flange. This pipe is connected to the tangential inlet of the high-temperature cyclone dust collector 14 in the shortest possible distance to prevent high-temperature oil and gas (about 500-600℃) from condensing due to temperature drop during transportation.

[0064] The high-temperature cyclone dust collector 14 has a wear-resistant castable lining and is designed to remove dust with a dust removal efficiency of ≥95%. It is used to remove fine carbon powder and dust entrained in pyrolysis gas. The collected fine carbon powder is continuously discharged through the lower rotary valve and can be incorporated into biochar products.

[0065] The clean pyrolysis gas (approximately 500℃) after dust removal enters the heavy component spray quench tower 15. This tower is a packed tower with a diameter of 800mm and a height of 10000mm, containing two sections of acid-resistant ceramic (SiC) structured packing with a total packing height of 6m. An independent heavy oil circulation condensation loop is installed outside the tower, including a circulation pump (flow rate 30 m³ / h, head 40m) and a circulating medium cooler 16 (shell-and-tube heat exchanger with a heat exchange area of ​​100m², using heat transfer oil as the medium). By adjusting the cooling medium flow rate of the circulating medium cooler 16, the temperature of the circulating heavy oil sprayed to the top of the tower is precisely controlled at 150±5℃. The pyrolysis gas enters from the bottom of the tower and comes into countercurrent contact with the low-temperature heavy oil flowing from top to bottom in the packing layer. Through the "oil washing gas" method, the heavy tar components with higher boiling points (boiling point > 300℃) in the mixed gas are preferentially condensed and precipitated. They flow into the heavy oil tank at the bottom of the tower with the circulating heavy oil and are periodically discharged as heavy oil products (mainly composed of asphalt, polycyclic aromatic hydrocarbons, etc.).

[0066] Uncondensed light component gas (approximately 150°C) is discharged from the top of the tower and enters the light component shell-and-tube condenser 17. This condenser has a shell-and-tube structure with a heat exchange area of ​​200 m². Circulating cooling water flows through the tubes (inlet temperature 25°C, outlet temperature 35°C), while the shell side carries the heat-decomposed gas. The gas is rapidly cooled to 35-40°C between the tubes, causing the light organic components such as phenols, ketones, and aldehydes, as well as water vapor, to completely condense and precipitate. After gas-liquid separation, the liquid phase enters the light bio-oil storage tank, yielding a reddish-brown light bio-oil product (mainly composed of phenols, acids, ketones, etc.). The non-condensable gas (mainly composed of CO, H2, CH4, C2H4, etc., with a calorific value of approximately 12-15 MJ / Nm³) is purified by a demister and then sent to a gas storage tank or directly recycled through pipelines for heating in industrial furnaces of the smelter.

[0067] II. Process Operation Method

[0068] The specific process steps for biomass pyrolysis using the above system are as follows:

[0069] (1) System startup and establishment of inert atmosphere

[0070] Start the variable frequency drive unit 9 to rotate the bare tube refractory-lined rotary reactor 7 at a low speed of 2 r / min. Continuously introduce nitrogen gas into the system through the inert gas protection interface 5 and purge for 30 minutes until the oxygen content (volume fraction) of the gas sampled from the outlet of the high-temperature cyclone dust collector 14 is less than 1%. Start the circulating oil pump of the heavy component spray quench tower 15 to establish heavy oil circulation, and adjust the spray oil temperature at the top of the tower to 150℃ through the circulating medium cooler 16.

[0071] (2) Feeding and Mixed Pyrolysis

[0072] High-temperature copper slag (1250℃, flow rate 2 t / h) from a copper smelting flash furnace is transferred via a slag bag to a high-temperature slag receiving hopper 1, and then continuously slids into the reactor via a refractory gravity sliding chute 3, forming a high-temperature heat carrier bed with a thickness of approximately 100-150 mm at the bottom of the reactor. Simultaneously, pine sawdust (particle size ≤10 mm, initial moisture content 15%) is continuously injected into the reactor from a biomass feed hopper 2 via a cantilevered direct-injection screw conveyor 4 at a flow rate of 0.5 t / h. After leaving the screw nozzle, the pine sawdust falls directly onto the surface of the high-temperature slag (above 1000℃) in a parabolic trajectory.

[0073] As the vessel rotates continuously at 2 r / min, the molten slag and pine sawdust are carried up and tumbled together by the action of the vessel's inner wall (which has no internal components), constantly renewing the heat transfer interface. The pine sawdust instantly absorbs the sensible heat of the molten slag, rapidly rising to 500-600℃, undergoing rapid drying and pyrolysis to generate pyrolysis volatiles (an oil-gas mixture), and the solid products gradually carbonize into biochar. During the heat transfer process, the temperature of the molten slag gradually decreases, transforming from a molten state (1250℃) into solid particles (approximately 600℃), and continues to move forward with the rotation of the vessel.

[0074] (3) Solid-phase hot separation and waste heat feedback

[0075] The solid mixture after the reaction (biochar and slag particles at approximately 600°C) moves to the tail end of the reactor and enters a built-in hot-state classifying drum screen 11 that rotates synchronously with the reactor. Inside the drum screen, biochar powder with a particle size of less than 5 mm passes through the screen holes and falls into the biochar collection hopper 12 below. After being cooled to 150°C by a water-cooled jacket, it is continuously discharged through a star-shaped discharge valve and further cooled to below 40°C by a closed spiral cooling conveyor, thus obtaining a high-porosity biochar product (specific surface area ≥300 m² / g).

[0076] Cooled copper slag particles larger than 5 mm (approximately 600°C) are discharged from the screen and enter the counter-current slag sensible heat utilization heat exchanger 13 via a chute. Inside the heat exchanger, the slag particles slowly fall and come into counter-current contact with 20°C ambient cold air (airflow 3000 m³ / h) supplied by the bottom blower for heat exchange. After heat exchange, the slag temperature drops below 80°C and is discharged and stored through the bottom discharge valve. The cold air is heated to 200-220°C to form clean hot air, which is then returned by an induced draft fan through insulated pipes to the jacket of the biomass feed silo 2 to pre-dry the pine sawdust inside the silo, reducing its moisture content from 15% to below 8%.

[0077] (4) Vapor phase dust removal and staged condensation

[0078] The pyrolysis mixture at approximately 550°C is discharged from the kiln tail and enters the high-temperature cyclone dust collector 14 through an insulated pipe. Inside the dust collector, the fine carbon powder (particle size <0.1mm) carried in the airflow is separated and captured, and continuously discharged through the lower star-shaped ash discharge valve, and incorporated into the biochar product.

[0079] The pyrolysis gas (approximately 530°C) after dust removal enters the bottom of the heavy component spray quench tower 15. Inside the tower, the pyrolysis gas and the 150°C circulating heavy oil sprayed from top to bottom come into countercurrent contact within the SiC packing layer. Heavy tar components in the pyrolysis gas with boiling points above 300°C (such as asphalt and polycyclic aromatic hydrocarbons) preferentially condense upon cooling and mix into the circulating heavy oil. As the heavy components in the circulating heavy oil continuously accumulate, a portion of the heavy oil is discharged from the bottom of the tower as a product and sent to the heavy oil storage tank, yielding the heavy tar product.

[0080] Uncondensed light component gas (approximately 150°C) is discharged from the top of the tower and enters the light component tubular condenser 17. Inside the condenser, the gas is rapidly cooled to 35-40°C by circulating cooling water at 25-35°C in the tube side, causing the light organic components such as phenols, ketones, and aldehydes, as well as water vapor, to condense and precipitate. After gas-liquid separation, the liquid phase enters the storage tank as a light bio-oil product, yielding reddish-brown light bio-oil. The non-condensable combustible gas (mainly composed of CO, H2, and CH4, with a calorific value of approximately 13 MJ / Nm³) is purified by a demister and then piped to the smelter's steam boiler or drying kiln for use as fuel.

[0081] After 72 hours of continuous operation testing, the system operated stably without any issues such as coking at the feed inlet or damage to internal components of the reactor. Product yields and quality are as follows: biochar yield approximately 28% (wt), with a higher calorific value ≥28 MJ / kg; heavy tar yield approximately 10% (wt); light bio-oil yield approximately 35% (wt); and non-condensable combustible gas yield approximately 27% (wt). The sensible heat recovery rate of the slag is ≥85%, achieving efficient cascade utilization of energy and high-value conversion of biomass resources.

[0082] III. Significant Technological Advancements and Advantages:

[0083] Firstly, regarding the durability and operational safety of core equipment, this invention fundamentally overcomes the hardware bottleneck restricting the industrialization of molten slag coupling technology by reconstructing the reactor structure and feeding method. The system innovatively abandons the metal lifting fins and stirring shafts inside traditional rotary kilns, which are prone to high-temperature failure, and instead adopts a bare tube refractory lining structure. Utilizing the excellent high-temperature resistance and abrasion resistance of the refractory material, combined with the rotary kiln's own gravity tumbling mechanism, slag mixing is achieved. This eliminates the risk of softening, deformation, and breakage of metal components in the molten slag environment at thousands of degrees Celsius, significantly extending the equipment maintenance cycle from several weeks to more than six months. Simultaneously, addressing the tendency of biomass to prematurely combust and coke, the refractory chute sliding and cantilevered spiral direct injection feeding structure designed in this invention physically isolates the high-temperature molten slag and biomass, avoiding pre-mixing contact between the two at the narrow feed throat. This effectively eliminates the hidden dangers of premature combustion and coking blockage in the feed channel, providing a solid hardware guarantee for the system to achieve long-term, inherently safe continuous operation.

[0084] Secondly, regarding system energy efficiency and product recovery quality, this invention constructs a closed-loop energy cascade utilization system and a refined product classification system, significantly improving the economics of the process. This invention systematically breaks the limitation of solely utilizing the high-temperature sensible heat of molten slag, establishing an energy gradient utilization mode of high-temperature molten slag-driven chemical pyrolysis and medium-temperature molten slag feedback physical drying. The waste heat from the molten slag discharged after the reaction is converted into hot air to feed back into the raw material pretreatment, maximizing the utilization of molten slag thermal energy and achieving truly zero-energy pyrolysis operation. More importantly, this invention changes the traditional extensive recovery path. Through hot-state screening technology, biochar is separated before cooling, avoiding tar adsorption pollution and ensuring the high porosity and activity of the carbon material. Combined with a cascade fractionation and condensation process on the gas phase side, high-purity heavy tar and light bio-oil are directly separated by the physical differences of the components, eliminating the need for subsequent complex upgrading processes, thus achieving high-value resource recovery of all components (gas, liquid, and solid) in one step.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A biomass side-entry pyrolysis recovery system driven by sensible heat of molten slag, characterized in that, include: A separate feeding system is used to separately feed the high-temperature molten slag heat carrier and biomass raw materials into the reactor. The tube-type refractory-lined rotary reactor (7) is used to drive the biomass to undergo self-heating pyrolysis reaction by using the sensible heat of high-temperature molten slag as a heat source. Its feed end is connected to the separate feed system. The high-temperature molten slag heat carrier and biomass are mixed in the reactor as the reactor rotates. There are no metal components with stirring function inside the reactor. The solid phase classification collection and waste heat feedback system is connected to the discharge end of the tube-type refractory-lined rotary reactor (7) to realize the hot separation of pyrolysis solid phase products and the graded recovery and utilization of slag waste heat. A multi-stage gas-liquid purification and recovery system is connected to the outlet of the tube-type refractory-lined rotary reactor (7) and is used for the staged purification and fractionation recovery of pyrolysis gaseous products.

2. The biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag according to claim 1, characterized in that: The separate feeding system includes a high-temperature slag receiving hopper (1), a biomass feeding bin (2), a refractory gravity sliding chute (3), and a cantilever direct injection screw conveyor (4). The refractory gravity sliding chute (3) is set at an inclination. Its high end is connected to the bottom outlet of the high temperature molten slag receiving hopper (1), and its low end extends into the bottom of the tube-type refractory lining rotary reactor (7) to guide the high temperature molten slag to slide into the reactor by gravity to form a heat carrier bed. The cantilevered direct injection screw conveyor (4) is set horizontally, with its feed end connected to the biomass feed silo (2) and its discharge end extending into the tube-type refractory lining rotary reactor (7). Its discharge port is located above the discharge point of the refractory gravity sliding chute (3) and is closer to the center of the reactor than the discharge point of the refractory gravity sliding chute (3).

3. The biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag according to claim 1, characterized in that: The tube-type refractory-lined rotary reactor (7) has a cylindrical tube structure. Its inner wall is lined with a wear-resistant refractory lining, and a main drive gear ring (8) is fitted on the outer wall. The main drive gear ring (8) is driven by a frequency converter (9) to control the rotation of the reactor body.

4. The biomass side-entry pyrolysis recovery system based on sensible heat of molten slag as described in claim 1, characterized in that: The solid phase classification collection and waste heat feedback system includes a built-in hot-state classification drum screen (11), a biochar collection hopper (12), and a counter-current slag sensible heat utilization heat exchanger (13). The built-in hot-state grading drum screen (11) is coaxially fixedly installed at the discharge end of the tube-type refractory-lined rotary reactor (7) and rotates synchronously with the reactor body. It is used to separate the mixed materials into small-diameter biochar under the screen and large-diameter molten slag over the screen. The biochar collection hopper (12) is arranged below the built-in hot-state grading drum screen (11) for collecting biochar as undersize material. The counter-current slag sensible heat utilization heat exchanger (13) is connected to the oversize outlet of the built-in hot-state grading drum screen (11) to receive the cooled slag as oversize and perform air-cooled heat exchange. It has a channel inside for the cooled slag and cold air to exchange heat in a counter-current manner. The hot air outlet at the top is connected back to the biomass feed silo (2) through a pipe for the pre-drying of biomass raw materials.

5. The biomass side-entry pyrolysis recovery system based on sensible heat of molten slag as described in claim 1, characterized in that: The gas-liquid multi-stage purification and recovery system includes a high-temperature cyclone dust collector (14), a heavy component spray quench tower (15), and a light component tubular condenser (17) connected in series along the airflow direction. The air inlet of the high-temperature cyclone dust collector (14) is connected to the air outlet of the tube-type refractory-lined rotary reactor (7). The heavy component spray quench tower (15) is equipped with a matching circulating medium cooler (16) to control the temperature of the spray liquid so as to preferentially condense and collect the heavy tar in the pyrolysis gas. The light component tubular condenser (17) is located at the end of the gas path and is used to condense and collect light bio-oil and separate non-condensable combustible gas.

6. The biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag according to claim 1, characterized in that: The feed end of the tube-type refractory-lined rotary reactor (7) is equipped with a kiln head composite dynamic and static sealing assembly (6), and the discharge end is equipped with a kiln tail transition sealing assembly (10) to maintain the atmosphere isolation inside the reactor. The feed end is also provided with an inert gas protection interface (5) for introducing inert protective gas into the system to maintain an anaerobic environment.

7. A biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag according to claim 2, characterized in that: The refractory gravity sliding chute (3) has an inclination angle of 35°-45°. Its core is a high-purity silicon carbide ceramic inner cylinder, which is wrapped with a steel shell. Insulation cotton is filled between the steel shell and the high-purity silicon carbide ceramic inner cylinder.

8. A biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag according to claim 2, characterized in that: The inner wall of the high-temperature slag receiving hopper (1) is filled with wear-resistant and refractory castable with a thickness of not less than 100mm. The cantilever direct injection screw conveyor (4) adopts a double-layer water cooling jacket structure. The screw blades are made of 310S heat-resistant stainless steel and extend into the kettle for 1-2 meters.

9. A biomass side-entry pyrolysis recovery system based on sensible heat driven by molten slag, as described in claim 4, characterized in that: The screen of the built-in hot-state grading drum screen (11) is made of high-temperature resistant alloy steel and the aperture is set to 3-5mm. The lower part of the collecting hopper (12) is provided with a star-shaped unloader.

10. A method for biomass side-entry autothermal pyrolysis and product graded recovery based on the sensible heat cascade utilization of molten slag, characterized in that, The system described in any one of claims 1-9 specifically includes the following steps: Feeding: High-temperature molten slag slides into the bottom of the refractory-lined rotary reactor (7) via a refractory gravity sliding chute (3); biomass is injected into the reactor via a cantilevered direct injection screw conveyor (4) and falls onto the surface of the high-temperature molten slag in a parabolic manner. Pyrolysis: As the reactor rotates, biomass and molten slag tumble and mix, and the sensible heat of the molten slag is used to carry out a self-heating pyrolysis reaction to generate pyrolysis oil and gas and a solid mixture. Solid phase separation and waste heat feedback: The solid phase mixture after pyrolysis is separated by a built-in hot-state classifying drum screen (11). The fine particles of biochar under the screen fall into the biochar collection hopper (12) for collection, and the cooled molten slag particles on the screen enter the counter-current molten slag sensible heat utilization heat exchanger (13) to exchange heat with the counter-current cold air. The cooled molten slag is discharged, and the heated hot air is sent back to the feeding system for raw material pre-drying. Gas-phase staged condensation: After the pyrolysis oil and gas are dedusted by the high-temperature cyclone dust collector (14), the high-boiling-point heavy tar is preferentially condensed and collected in the heavy component spray quench tower (15) by controlling the temperature of the spray liquid; the remaining gas is condensed and collected in the light component tubular condenser (17) to collect light bio-oil and separate non-condensable combustible gas.

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